White Paper Harmonics Ver 1

H A R M O N I C Sin Power Systems

White Paper On

Limits, Measurements & Enforcement

TRACTION INSTALLATION DIRECTORATE

Research, Designs & Standards Organisation

Ministry of Railways

PO: Manaknagar, Lucknow-226 011

August 2012

Table of Contents

1. Introduction! 1

1.1. Power Quality: Background! 1

1.2. Definition of power quality! 2

1.3. Various aspects of power quality! 2

1.4. Effect of harmonics! 3

2. Governing Standards: Explanation & Interpretation! 5

2.1. Fundamental Issues! 5

2.2. Regulations! 5

2.3. Discussion! 10

3. IEEE-519: 1992: The Document & Commentary! 14

3.1. Background! 14

3.2. Issues with IEEE 519-1992: Expert’s Perspective! 16

3.3. Key Aspects of IEEE 519-1992! 17

3.4. Nuances! 18

4. The Ecosystem of Standards! 19

4.1. The US Standards/Guidelines! 19

4.2. The British Standard: Engineering Recommendation G5/4-1! 22

4.3. IEC 61000 Family of Standards! 27

5. Conclusion! 31

6. Annexure A! i

! H a r m o n i c s i n P o w e r S y s t e m s

I

1. Introduction

1.1. Power Quality: Background

Electrical power is now the principal form of energy consumed globally. From the smallest of domestic chores to giant machines, electricity is to be found as the energy form of choice. Practically all energy which is used is centrally generated at few power stations and the same gets poured in to the grid and thereafter gets distributed to the customers. Like a highway, which is required to carry higher amounts of traffic, rules of engagement of the users, transmission agencies and the generating units have to be established, else the system would stop working or just collapse.

Electricity Grid, is described as the biggest and most complex machine ever made. The commodity handled on the Grid is highly perishable and there must always be a perfect balance between the energy generated at the generating stations and the energy consumed by the consumers. A mismatch will make the Grid unstable and trip it-serious, physical damage will occur if the Grid is not adequately protected.

As the Grid gets several generators pooling energy in and several consumers drawing out, the discipline needs to be followed by all the participants. Thus, on one hand, the customer expects stable power supply in terms of availability, waveform fidelity and frequency; the customers are supposed to draw power in the prescribed regimen, which should not affect other stakeholders.

Various standards prescribe the standards to which a customer should get power and also, they stipulate the power drawal regimen.

To illustrate, in case the customer draws power at poor power factor, though, the physical utilisation of power is low, the generating units and the transmission lines nevertheless gets stressed to full measure. Thus, there is mechanism designed to make customers draw power at good power factor, so that the rest of the system gets stressed only to the extent of utilisation.

As the loads become more non-linear, issue of harmonics and discipline thereof has assumed increasing importance. The general appreciation of power utilisation hitherto has been based on linear loads and voltage/currents measured at 50 Hz.


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1.2. Definition of power quality

The term has been best described in the open encyclopedia-the Wikipedia1 as: Power quality is the set of limits of electrical properties that allows electrical systems to function in their intended manner without significant loss of performance or life. The term is used to describe electric power that drives an electrical load and the load's ability to function properly with that electric power.

IEEE 1159-2009 talks of power quality as wide variety of electromagnetic phenomena that characterizes the voltage and current at a given time and at a given location on the power system.

C. Sankaran in his book, Power Quality (CRC Press) defines the term as: Power quality is a set of electrical boundaries that allows a piece of equipment to function in its intended manner without significant loss of performance or life expectancy.

1.3. Various aspects of power quality2

ASPECT DEFINITION

Magnitude (regulation)

Long term level of voltage established through transformer taps and dynamically controlled by regulators. Measurement of voltage magnitude over the long term serves the basis for the capture and characterization of other power quality disturbances.

Unbalance Condition of the 3 phase power system where the rms magnitude or phase angle of the line voltages are not equal. This is usually determined as a percent of the ratio of negative sequence component to positive sequence component.

Harmonics Components of electricity with frequencies which are an integral multiple of the fundamental frequency. This is usually expressed in Total Harmonic Distortion or as individual harmonic order (frequency) components.

Flicker Periodic fluctuation of voltage that results in flicker of lighting, particularly incandescent lighting. This is typically causes by fluctuating loads such as hoists, reciprocating pumps, arc furnaces, etc.

Generation occurs at 50 Hz, which is the frequency of the grid. The generators make available a 3-∅ voltage on the grid. As loads get connected, currents flow and power


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1 http://en.wikipedia.org/wiki/Power_quality

2 http://www.hydroone.com/IndustrialLDCs/Pages/PQDefinitions.aspx

gets transacted. The generators need to be loaded evenly on their phases and are designed for taking certain specified amount of unbalance. However, the loads on the grid are suitably distributed over phases, the generators see largely balanced loads. However, some old stations can have difficulty in meeting unbalanced loads. This aspect has been touched upon later while discussing the British Standard ER G5/4-1.

It may be noted that the discussion on harmonics in Indian context is limited to the integral multiple of the fundamental frequencies, whereas perusal of IEEE 519-1992, IEC 61000 family of Standards and British ER G5/4-1 and several commentaries and many more papers reveal need to include inter-harmonics (non-integral multiples of the fundamental) and subharmonics (fractions of the fundamental frequency). This is an area which needs to be covered in Indian Regulatory framework.

1.4. Effect of harmonics3

AT EFFECT

Circuit Breakers Malfunction

Capacitor Banks Overheating

Insulation Breakdown

Failure of internal fuses

Protection Equipment False tripping

Measuring devices Wrong measurements

Transformer reactors Overheating

Motors Increased noise levels

Overheating

Telephones Noise

Transmission lines Overheating

Electronic devices Wrong pulses on data transmission

Over/under voltage

Flickering screens


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3 Power Quality in Electrical Systems, Alexander Kusko, Marc T. Thompson, McGraw Hill

AT EFFECT

Incandescent lamps Reduced life

Flicker


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2. Governing Standards: Explanation & Interpretation

2.1. Fundamental Issues

It is the responsibility of the utility to provide voltage with nil THD (Total Harmonic Distortion)

%V VV

100THD12

n2

n 2

n

#= =/

! ! ! ...[1]

Since,

V VRMS n2

n 1

n==/ ! ! ! ! ! ! ! ! ...[2]

The equation # (1) can also be written as:

%V VV V 100THD

12

RMS2

12

#= -! ! ! ! ! ! ...[3]

Where,

VTHD : Voltage’s Total Harmonic Distortion

Vn : nth Harmonic

VRMS : Root Mean Square of Voltage

VTHD is hence measure of the amount by which the Voltage is distorted. Depending upon the configuration of power supply and type of load, the harmonic content will change. To illustrate, 3rd harmonic or 150 Hz component indicates presence of single phase rectifier load, whereas, odd harmonics without triplens, indicate a full bridge rectifier on 3-phase supply.

2.2. Regulations

Harmonics as as aspect of power quality is fairly new and there still exists considerable confusion on application of the harmonic measures. This section will explore various Indian regulations in vogue.

2.2.1. Central Electricity Authority (Grid Standards) Regulations, 2010

These Regulations stipulate that the transmission licensee shall ensure voltage to conform to the following:


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SR. NO. SYSTEM VOLTAGE (KV RMS)

THD (%) INDIVIDUAL HARMONIC OF A PARTICULAR

FREQUENCY

1 765 1.5 1.0

2 400 2.0 1.5

3 220 2.5 2.0

4 33 to 132 5.0 3.0

The CEA (Grid Standards) Regulations, 2010 define VTHD as:

%V VV

100THD12

n2

n 2

40

#= =/

! ! ! ! ! ...[4]

Further, this Clause stipulates:

“Provided that the standard on Harmonic Distortion shall come into force concurrently with clause 3 of Part IV of the Schedule to the Central Electricity Authority (Technical Standards for Connectivity to the Grid) Regulations, 2007”.

2.2.2. Central Electricity Authority (Technical Standards for Connectivity to

the Grid) Regulations, 2007

There are two very significant directions in these Regulations, they being:

2.2.2.i. Reactive Power4:

2.2.2.i.a. The distribution licensees shall provide adequate reactive compensation to compensate the inductive reactive power requirement in their system so that they do not depend upon the Grid for reactive power support.

2.2.2.i.b. The power factor of the distribution system and the bulk consumer shall not be less than 0.95.


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4 See also Cl.4.6.1 and 6.6 of Central Electricity Regulatory Commission (Indian Electricity Grid Code) Regulations, 2010. It is clear from CEA and CERC’s referred Regulations that reactive power flow (either leading or lagging) should not transact on connected network not owned by IR. This should be seen as long term view to be taken by railways in planning for pf improvement.

2.2.2.ii. Voltage and Current Harmonics (Cl. 3 of Part IV of the Schedule, which is referred above at 2.2.1):

2.2.2.ii.a. The total harmonic distortion for voltage at the connection point shall not exceed 5% with no individual harmonic higher than 3%.

2.2.2.ii.b. The total harmonic distortion for the current drawn from the transmission system at the connection point shall not exceed 8%5.

2.2.2.ii.c. The limits prescribed shall be implemented in a phased manner so as to achieve complete compliance not later that five years from the date of publication of these regulations in the Official Gazette.

It is seen that the above stipulations don’t refer to any International/National Standard or Practice. This Regulation, in Part II of Schedule, for Grid Connectivity Standards applicable to the Generating Units talks about applicability of IEEE-519 for new generating units.

2.2.3. Chhattisgarh State Electricity Supply Code-2011

2.2.3.i. In the Chapter 2, harmonics are to be governed by IEEE STD 519-1992, namely “IEEE Recommended Practices and Requirements for Harmonic Control in Electrical Power Systems”.

2.2.3.ii. Clause 3.7 of the Code is most explicitly lays down the responsibility of the user:

2.2.3.ii.a. The maximum permissible limit of harmonics as specified in Institute of Electrical and Electronics Engineers (IEEE) standard 519 (1992) adopted in clause (5) of part-II of Central Electricity Authority (Technical Standard of Connectivity to the Grid) Regulations 20076 (hereafter CEA (Technical Standard Regulations) is as follows:

• Voltage distortion limit – Utilities’ responsibility


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5 This appears to be anomalous, as for current, THD limit can’t be stipulated. This is because in lightly loaded conditions, the THD is likely to be very poor.

6 This Clause appears under ‘Grid Connectivity Standards applicable to the Generating Units’ and appears in the section for ‘New Generating Units’, whereas, the State’s Electricity Supply Code-2011, brings this as the governing standard for customer-utility interface.

BUS VOLTAGE MAXIMUM INDIVIDUAL VOLTAGE DISTORTION

TOTAL MAXIMUM VOLTAGE DISTORTION

33 kV & 132 kV 3.0 5.0

220 kV 2.0 2.5

400 kV 1.5 2.0

• Current distortion – Users’ responsibility The total harmonics distortion for current drawn from the transmission system at the connection point shall not exceed 8%.

2.2.4. IEEE Std. 519-1992: “IEEE Recommended Practices and Requirements

for Harmonic Control in Electrical Power Systems”

2.2.4.i. It was was first introduced in 1981 and comprehensively revised in 1992. It is interesting to note that though the document has been published as a Standard by IEEE Standards Board and approved by American National Standards Institute (the document is recognised as American National Standard), in its title it is referred to be ‘Recommended Practices’ and in its abstract this is referred to as a ‘Guide’.

2.2.4.ii. In the foreword to the Standard, it is mentioned: ‘This recommended practice recognises the responsibility that the users have not to degrade the voltage of the utility serving other users by requiring non-linear currents from the utility. It also recognises the responsibility of the utilities to provide users with close to a sine wave of voltage ’.

2.2.4.iii. The standard lays down the following limits for the voltage harmonics:

Voltage Distortion Limits of IEEE 519-1992 given in Table 11.1

Bus Voltage at PCC Individual Voltage Distortion (%) Total Voltage Distortion THD (%)

69 kV and below 3.0 5.0

69.001 kV through 161 kV 1.5 2.5

161.001 kV and above 1.0 1.5

NOTE: High-voltage systems can have up to 2.0% THD where the cause is an HVDC terminal that will attenuate by the time it is tapped for a user.




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2.2.4.iv. The standard lays down the following limits (combining Table 10.3, 10.4 and 10.5 of IEEE 519-1992) for the current harmonics:

Maximum Harmonic Current Distor2on limits (Ih) in Percent of ILMaximum Harmonic Current Distor2on limits (Ih) in Percent of ILMaximum Harmonic Current Distor2on limits (Ih) in Percent of ILMaximum Harmonic Current Distor2on limits (Ih) in Percent of ILMaximum Harmonic Current Distor2on limits (Ih) in Percent of ILMaximum Harmonic Current Distor2on limits (Ih) in Percent of ILMaximum Harmonic Current Distor2on limits (Ih) in Percent of IL

Individual Harmonic Order (Odd Harmonics)Individual Harmonic Order (Odd Harmonics)Individual Harmonic Order (Odd Harmonics)Individual Harmonic Order (Odd Harmonics)Individual Harmonic Order (Odd Harmonics)Individual Harmonic Order (Odd Harmonics)Individual Harmonic Order (Odd Harmonics)Table 10.3 of IEEE 519-‐1992

Current Distor;on Limits for General Distribu;on Systems120 V < Vn ≤ 69 kV

Table 10.3 of IEEE 519-‐1992Current Distor;on Limits for General Distribu;on Systems

120 V < Vn ≤ 69 kV


120 V < Vn ≤ 69 kV


120 V < Vn ≤ 69 kV


120 V < Vn ≤ 69 kV


120 V < Vn ≤ 69 kV


120 V < Vn ≤ 69 kVISC/IL <11 11≤h<17 17≤h<23 23≤h<35 35≤h TDD

<20*20<5050<100100<1000>1000

4.07.010.012.015.0

2.03.54.55.57.0

1.52.54.05.06.0

0.61.01.52.02.5

0.30.50.71.01.4

5.08.012.015.020.0

Table 10.4 of IEEE 519-‐1992Current Distor;on Limits for General Sub transmission Systems

69 kV < Vn ≤ 161 kV


69 kV < Vn ≤ 161 kV


69 kV < Vn ≤ 161 kV


69 kV < Vn ≤ 161 kV


69 kV < Vn ≤ 161 kV


69 kV < Vn ≤ 161 kV


69 kV < Vn ≤ 161 kV<20*20<5050<100100<1000>1000

2.03.55.06.07.5

1.01.752.252.753.5

0.751.252.02.53.0

0.30.50.751.01.25

0.150.250.350.50.7

2.54.06.07.510.0

Table 10.5 of IEEE 519-‐1992Current Distor;on Limits for General Transmission Systems (>161 kV)

Dispersed Genera;on and Cogenera;onVn > 161 kV













<50≥50

2.03.0

1.01.5

0.751.15

0.30.45

0.150.22

2.53.75

Even harmonics are limited to 25% of the odd harmonic limits above.Even harmonics are limited to 25% of the odd harmonic limits above.Even harmonics are limited to 25% of the odd harmonic limits above.Even harmonics are limited to 25% of the odd harmonic limits above.Even harmonics are limited to 25% of the odd harmonic limits above.Even harmonics are limited to 25% of the odd harmonic limits above.Even harmonics are limited to 25% of the odd harmonic limits above.

Current distortions that result in a dc offset, e.g. half-wave converters, are not allowed.Current distortions that result in a dc offset, e.g. half-wave converters, are not allowed.Current distortions that result in a dc offset, e.g. half-wave converters, are not allowed.Current distortions that result in a dc offset, e.g. half-wave converters, are not allowed.Current distortions that result in a dc offset, e.g. half-wave converters, are not allowed.Current distortions that result in a dc offset, e.g. half-wave converters, are not allowed.Current distortions that result in a dc offset, e.g. half-wave converters, are not allowed.

* All power generation equipment is limited to these values of current distortion, regardless of actual Isc/IL.* All power generation equipment is limited to these values of current distortion, regardless of actual Isc/IL.* All power generation equipment is limited to these values of current distortion, regardless of actual Isc/IL.* All power generation equipment is limited to these values of current distortion, regardless of actual Isc/IL.* All power generation equipment is limited to these values of current distortion, regardless of actual Isc/IL.* All power generation equipment is limited to these values of current distortion, regardless of actual Isc/IL.* All power generation equipment is limited to these values of current distortion, regardless of actual Isc/IL.WhereIsc = maximum short-circuit current at PCC.IL = maximum demand load current (fundamental frequency component) at PCC.

WhereIsc = maximum short-circuit current at PCC.IL = maximum demand load current (fundamental frequency component) at PCC.






2.2.4.v. It can be seen the above values for voltages apply for the utilities, dealt in Section 11 of the Recommended Practices and for current in Section 10 apply on the customers. Though, the limits on voltage appear to be straight forward, those for current need to be interpreted.

2.2.4.vi. A deeper study of the literature and the document itself, indicates imperative need of taking a nuanced view of the situation. It is also required to appreciate the fact as to how this document evolved to become a ‘Recommended Practice’. This White Paper dwells on the issues in implementing the limits stipulated in


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the document and takes a closer look of the document’s intent and evolution in Chapter 3.

2.3. Discussion

2.3.1. As seen from the foregoing, the CEA’s Regulations in vogue in the country, make a mention of harmonics expected at the point of common coupling (PCC) but are silent on the standards these limits are based on and the method of arriving at these limits.

2.3.2. Explicit reference to IEEE 519-1992 has been given in Chattisgarh State Electricity Supply Code-2011 vis-a-vis customer interface.

2.3.3. The reference to IEEE 519-1992 has not been made with respect to user-utility interaction in CEA’s Regulations. They find mention in Central Electricity Authority (Technical Standards for Connectivity to the Grid) Regulations, 2007’s Part II of Schedule, for Grid Connectivity Standards applicable to the Generating Units. This as can be noted that this link of CEA’s Regulations with IEEE 519-1992 is with connecting new generating units to the grid and not about consumer-utility interface.

2.3.4. The CEA’s Regulations and individual State’s stipulations are silent on the modus operandi of measurements. It should be noted that for penal provisions, extent of trespass7 should be established. This presumes:

2.3.4.1. Having the red line drawn clearly, to indicate the limit: and

2.3.4.2. having a verifiable mechanism to reliably establish the extent of trespass.

2.3.5. However, as perusal of various documents indicate, real time, verifiable means of establishing trespass is not possible through IEEE 519-1992 as established in the next chapter.

2.3.6. For penalty to be tenable, existing CEA framework gravitating to IEEE 519-1992 is inadequate. With IR’s substantial stake in electric traction (more than 60% turnover is from electrified networks), it is in IR’s interests to zealously guard health of the power sector and work towards a superior power quality regime.


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7 borrowing the phrase from Paulo F. Ribeiro’s term from his paper ‘Common Misapplications of the IEEE 519 Harmonic Standard: Voltage or Current Limits’. The paper is available on IEEE Xplore digital library.

2.3.7. It is seen that treatment of harmonics in the CEA’s guidelines leans heavily upon IEEE 519-1992 and it would be safe to surmise that this document would form the basis of measurements and interpretation of the results. It is hence, in order, to deliberate in detail the IEEE-519 standard and its various commentaries. As the matter is being dealt for the first time on institutional level in the country for the enforcement of limits on harmonics, it is prudent to bring forth various aspects of this document and their implications. It would be seen that straight forward THD measurement is not possible and there is need to cover lot of ground before implementation of this regime.

2.3.8. To appreciate the imperative and urgent need to deliberate on the history, limits and philosophy of the ‘Recommended Practices’, we need to pause and take a quick overview of two known instances where the application of harmonic limits is being sought:

2.3.8.i. In case of TANGEDCO, the CEA guidelines have been implemented with 15% flat penalty on the violation of the laid norms vide Tariff Order no. 1 of 2012. As the Tariff Order is derived from the CEA’ guidelines, they also inherit the lack of clarity on modus operandi of implementation. From the Tariff Order it is seen that there is element of ungraduated penalty, which fails to take cognisance of extent of ‘violation’ or extent of trespass.

2.3.8.ii. Punjab, instead of levying penalty has proposed higher tariff slab and the case is being contested.

2.3.9. It is worrying that application of IEEE 519’s recommendations has not been done in the spirit of the document. It should be noted that these Recommended Practices are guidelines for system design and the application of individual limits can be erroneous as IEEE 519: 1992 itself mentions at Cl. 10.4.2 (and elaborated in Ribeiro’s paper referred later in this White Paper)... Although the effects of harmonics on electric equipment, appliances, etc. are not fully understood at this time, it is recognized that the stated current distortion limits can be exceeded for periods of time without causing damage to equipment. When evaluating the user compliance with the stated limits, it is recommended that probability distribution plots be developed from he recorded data and analyzed. If the limits are only exceeded for a short period of time, the condition could be considered acceptable.

2.3.10. Apart from the above there is need of more clarity in the measurements as given below:


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SR. NO. ASPECT IMPACT

1 Calculation of TDD (Total Demand Distortion)

This should be done on the maximum load current as per IEEE 519-1992. Method of arriving at this value needs to be established. IEEE 519-1992 recommends that the load current be calculated as the average current of the maximum demand for the preceding 12 months. However, it is not clear how this can be applied to users with low load factors as traction loads.

Practice of plain measurements of THD for current is WRONG application of IEEE 519.

In almost all harmonic analysers, THD is measured, this, then is converted as TDD.

2 System level study for harmonics and resonance

This determines ability of the system to tolerate harmonics. It needs to be seen that genesis of IEEE 519 was in introduction of static converters which drew harmonic currents in a system with capacitors provided. As the Recommended Practices are system level document, one needs to establish the vulnerability of the utility to a customer’s non-linear load.

3 Measurement Period The Recommended Practice mention 10/15 minute period to arrive at levels of harmonic currents. Also, IEEE-519 recognises that stated distortion limits can be exceeded.

4 Extent of distortions Any penalty needs to be graduated to the extent of ‘violation’.

5 Calculation/estimation of load currents

There is recommended method to arrive at the loads to be considered while working out TDD. However, clear method needs to be established given highly dynamic nature of the traction load.


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2.3.11. Indian Railways under Ministry of Railways has been model customer since decades and view their responsibility to be so with due seriousness. Introduction of new generation of locomotives and electrical multiple units mitigate harmonics at the source itself. Being part of the Government, the Railways are keen to establish methods to implement equitable, practical and sustainable Power Quality regimen.

2.3.12. This document is a step to work out the interpretation of IEEE-519 in the country consistent with the document itself.


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3. IEEE-519: 1992: The Document & Commentary

3.1. Background

As has been seen in the foregoing, the CEA Regulations lean on the IEEE 519-1992. It is hence prudent to take a deeper look of the same. Though, there are other such standards world wide, the IEEE 519-1992 is discussed first.

It is important to understand the background of the IEEE-519 and its evolution to appreciate various values given. To get most authoritative view, paper by the Co-Chairman (Ray P. Stratford) and the Secretary (Christopher K. Duffey) of the joint task force which prepared the current version was referred to and salient points are discussed as under:

3.1.1. 8The electrical energy in the USA in 1970s was principally charged for based on demand and kWHrs. This prompted users to install capacitors extensively in their networks. The oil embargo of 1973 pushed the energy prices steeply. This encouraged use of capacitor even more. About this time the solid state drives matured. These drives needed harmonic currents. Increasing demand of harmonic currents and proliferation of capacitors together was perceived as serious development as this threatened the health of the electrical ecosystem.

3.1.2. Accordingly the Static Power Converter Committee of the Industry Applications Society started work on a document which emerged as ‘IEEE 519-1981, IEEE Guide for Harmonic Control and Reactive Compensation of Static Power Converters’. This document, though was meant to aid in the application of solid state converters, the utilities found it useful and accordingly a subgroup for study of harmonics was set up by the IEEE, Power Engineering Society under T&D Committee. When IEEE-519-1981 came up for review, a joint effort between original authoring committee, viz. Static Power Converter Committee and the Power Engineering Society was initiated.

3.1.3. Signaling wider acceptance of 1981 document, the new document received new name. To appreciate the changed thrust as reflected in the participation of the document reviewing committee, the following table can be perused:


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8 Christopher K. Duffey & Ray P. Stratford: Update of Harmonic Standard IEEE-519: IEEE Recommended Practices and Requirements for Harmonic Control in Electric Power Systems published in IEEE Transactions on Industry Applications, Vol 25, No.6 Nov/Dec 1989

OLD NAME OF IEEE 591-1981 NEW NAME OF IEEE 519-1992

IEEE Guide for Harmonic Control and

Reactive Compensation of Static

Power Converters

Recommended Practices and

Requirements for Harmonic Control In Electric Power Systems

The 1981 version gave limits for the voltage distortion only. Utilities faced unresolved issue of single customer taking up full harmonic current absorption capacity. This did not permit distribution among users to draw harmonic currents. This led to creation of the criteria which limits the harmonic currents drawn. It is this philosophy which is sought to be implemented.

3.1.4. It is seen that the authors saw this document to address a system problem. The standard saw imperative need of grading the requirement placed on the user by:

3.1.4.i. Clarifying the need to specify the strength of the network the user is connected to and

3.1.4.ii. Level of load user draws.

3.1.5. This was achieved by defining key metric viz:

SCR II

Load

Short_Circuit=

! ! ! ! ! ! ! ! ...[5]

SCR! ! : Short Circuit Ratio

IShort_Circuit! : Maximum short circuit current at PCC

ILoad ! ! : Maximum load current (fundamental) at PCC

The numerator denotes the available short-circuit level at the PCC (Point of Common Coupling). Higher level indicates stronger network as it can support a higher level of current. The ratio thus provides a way to size a customer. Larger customer is one who has a lower ratio, and as can be seen from the Table #10.1 of IEEE 519-1992 reproduced below, smaller customers can draw larger harmonic currents.


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Table 10.1 of IEEE 519-1992Basis for Harmonic Current Limits

SCR at PCC Maximum Individual Frequency Voltage Harmonic (%)

Related Assumption

10 2.5 – 3.0% Dedicated system20 2.0 – 2.5% 1 – 2 large customers50 1.0 – 1.5% A few relatively large customers100 0.5 – 1.0% 5 – 20 medium size customers1000 0.05 – 0.10% Many small customers

Above table gives user classification.

3.2. Issues with IEEE 519-1992: Expert’s Perspective

Further, paper of Paulo F.Ribeiro9 who has been a key resource on application of IEEE 519 and on a top level chair of IEEE Power Quality Subcommittee, as can be seen on the website of IEEE SA (Standards Association), has been referred10. As can be seen, this paper is very recent and has come by after CEA guidelines have come. The salient issues touched by Ribeiro being:

3.2.1. The IEEE 519 is not in reality a standard, its a recommended practice.

3.2.2. The objective of the recommendation is many times misunderstood and consequently erroneously interpreted and applied.

3.2.3. Issue of current vis-a-vis voltage limitation needs deliberation.

3.2.4. Though harmonic voltage is the ultimate measure of system integrity, harmonic currents, even with harmonic voltages are in limit can cause problems in series equipment like transformers and shunt equipment like capacitors.

3.2.5. Exceeding the harmonic current limits proposed by IEEE 519 and for one particular customer does not translate directly to a violation of the harmonic voltages. The limits prescribed, when aggregated with all other possible users at the same PCC could possibly result in a voltage distortion in excess of limits prescribed in IEEE 519. This point mentioned by Ribeiro needs to be read along with Cl 10.4.2 of IEEE 519-1992, which mentions ‘...it is recognized that the stated


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9 grouper.ieee.org/groups/td/pq/orgchart/2009-07-15%20PQ%20Subcom%20Organization%20Chart.pdf

10 Common Misapplications of the IEEE 519 Harmonic Standard: Voltage or Current Limits, Paulo F. Ribeiro, This paper appears in: Power and Energy Society General Meeting - Conversion and Delivery of Electrical Energy in the 21st Century, 2008 IEEE, Date of Conference: 20-24 July 2008

current distortion limits can be exceeded for periods of time without causing harm to the equipment. When evaluating user compliance with stated limits, it is recommended hat probability distribution plots be developed from the recorded data and analyzed. If the limits are only exceeded for a short period of time, the condition could be considered acceptable’.

3.2.6. Ribeiro cautions when utilizing these current limits to avoid designing or installing unnecessary and expensive filtering equipment.

3.2.7. He notes (note that this paper is as recent as 2008), ... Perhaps in future new diagnostic indices could be developed to assist in application of harmonic distortion recommendations...

3.2.8. Though IEEE 519 establishes or rather recommends that harmonic current limitation is the responsibility of end users and that of harmonic voltage is with the utility, as a simplified procedure for distortion control, end users are recommended to use both limits with sensitivity and discrimination to avoid installing unnecessary filtering equipment or neglecting possible local resonances which could cause internal interference and damages...Furthermore, considering that the present current limits were determined based on typical system impedances of 20 years ago, and much has changed in terms of system impedance, harmonic source characteristics and background distortion content, it is expected that the recommended limits for both voltage and current be used. Thus, one of the principal contributors to the IEEE-519 advocates caution against use of voltage for utility and current for user approach.

3.2.9. He concludes by noting...Excess of (current) limits on PCC or internal to an installation should not be immediately interpreted as the need for installation of filtering equipment. Harmonic Voltage limits, however, when exceeded at the PCC or within an installation should immediately require an overall checkup of the installation.

3.3. Key Aspects of IEEE 519-1992

Cl 10.4 of IEEE 519-1992 mentions...The recommended current distortion limits are concerned with the following indice (sic):

3.3.1. TDD: Total demand distortion (RSS), harmonic current distortion in % of maximum demand load current (15 or 30 min demand)


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3.3.2. The limits listed in Tables 10.3, 10.4, and 10.511 should be used as system design values for the “worst case”for normal operation (conditions lasting longer than one hour). For shorter periods, during start-ups or unusual conditions, the limits may be exceeded by 50%.

3.3.3. ...It is recommended that the load current, IL, be calculated as the average current of the maximum demand for the preceding 12 months.

3.3.4. Formulating above, we get:

... %I II I I I 100TDD

Load2

22

32

42

52

#= + + + + ...[6]

3.4. Nuances

3.4.1. To measure the current harmonics, practice is to carry out measurements with harmonic analysers, which carry out ‘snapshot THD (current) measurements’ which is clearly not the TDD as mentioned in the IEEE 519-1992. From the point of view of Railways, where the load is highly dynamic and the sub-stations see poor load factors, following need to be decided:

3.4.1.i. What is the demand load-should it be contract demand (CD) or maximum demand (MD) or transformer rating? Taking CD appears to be plausible way as this determines provisioning of upstream equipment and also reflects IR’s assessment of its load. This is the approach taken in IEC TR 61000-3-6.

3.4.1.ii. Measurements be done on 15/30 min period instead of taking snapshot of THD

3.4.1.iii. Conditions lasting for more than 1 hour be considered

3.4.1.iv. Direction of harmonics to be established. It is seen that being connected to a grid can make other customer’s harmonics travel to capacitor bank owned by some one else. There are some manufacturers who claim that their equipment can measure the direction of flow of harmonics. This has been refuted in several peer reviewed papers, like “An Investigation on the Validity of Power-Direction Method for Harmonic Source Determination” authored by Wilsun Xu and Yilu Liu (IEEE Transactions on Power Delivery, Vol. 18 No. 1 January 2003)

3.4.2. There is need to look at the practice followed globally and the developments.


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11 Table in Para 2.2.4.iv

4. The Ecosystem of StandardsThe problem of power quality has been studied under generic label of Electromagnetic Compatibility. There are several international standards which govern the EMC domain. Infact, with all these standards, there exists extensive commentaries and guidelines on their application.

The most extensive set of guidelines are laid by IEC. They have been developed by experts and have been voted upon by participating nations. Whereas, the IEEE 519-1992 has been developed by the volunteers and is a guideline. British Regulations G5/4-1 govern the harmonics in power systems. From the available information following information is compiled.

It is seen that Harmonics is but one dimension of Power Quality. Various documents, world wide have addressed the issue in a comprehensive manner. This is imperative as these issues usually are not amenable to piecemeal resolution/mitigation. The principal standards, viz. IEEE 519-1992, IEC-61000 family and the British ER G5/4-1 are all supposed to be accompanied by application guidelines. IEEE 519-1991’s application guideline is under preparation. It would be hence noted, that the reference of IEEE 519 influenced limits per se does not serve the long term purpose.

CEA’s Regulations have stated a laudable objective to usher in better power quality regime. However, a reference to IEEE-519-1992 and addressing just the harmonics part of the power quality domain needs further clarity.

4.1. The US Standards/Guidelines

4.1.1. IEEE Recommended Practices and Requirements for Harmonic Control

in Electrical Power Systems, IEEE 519-1992

This document is part of a fast evolving family of documents addressing various aspects of power quality. Leading researchers have expressed their concern on the inadequacies of the document which has come by more than two decades ago. This document has been discussed in the Chapter #3 of this White Paper in some detail.


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4.1.2. Guide for Applying Harmonic Limits on Power Systems (P519A):

4.1.2.i. This document is being prepared by P519A Task Force of the Harmonics Working Group (IEEE PES T&D Committee) and SCC22-Power Quality.

4.1.2.ii. This document’s need was felt to develop means of implementation of IEEE 519:1992 and incorporate better understanding of the harmonics. This is not yet published and the work is still on.

4.1.2.iii. This also indicates the fluidity in the applicability of IEEE 519-1992.

4.1.2.iv. P519A/D5 is available on the internet, this is dated May 4,1996. It is understood to have been withdrawn and a new draft is likely to come up.

4.1.2.v. Shown above are the principal documents on harmonics.


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Harmonics Standards

IEEE British IEC

IEEE 519-1992

IEEE 1159.1

IEEE 1159.3

IEEE 1159.2IEEE 1159-2009

G5/4-1

IEC 61000-2

IEC 61000-4

IEC 61000-3

IEEE 519.1

4.1.3. IEEE Recommended Practice for Monitoring Electric Power Quality,

IEEE 1159-2009

4.1.4. The standard aims to define the practice for monitoring power quality and gives overview of various aspects of the measurements.

4.1.5. Defines power quality phenomena.

4.1.6. Direct users in the proper monitoring and data interpretation of electromagnetic phenomena that cause power quality problems.

4.1.7. Offers a tutorial on power system disturbances and their common causes.

4.1.8. To summarise:

4.1.8.i. IEEE 1159: Provide general guidelines for PQ measurements & standard definitions for the different categories of PQ problems.

4.1.8.ii. IEEE 1159.1: Develop guidelines for instrumentation requirements associated with different types of PQ phenomena. The Standard is maintained by the Task Force on Recommended Practice for Power Quality.

4.1.8.iii. IEEE 1159.2: Develop guidelines for characterizing different PQ phenomena. The Standard is maintained by Task Force on Characterization of a Power Quality Event Given An Adequately Sampled Set of Digital Data Points (Characterization of the Sampled Data)

4.1.8.iv. IEEE 1159.3: Define an interchange format that can be used to exchange PQM information b/w different apps. The Standard is maintained by Task Force on the Transfer of Power Quality Data (Interchange data format).

4.1.9. 1250-2011 - IEEE Guide for Identifying and Improving Voltage Quality

in Power Systems12The use of some electrical equipment attached to typical power systems creates voltage quality concerns. There is an increasing awareness that some equipment is not designed to withstand the surges, faults, distortion, and


21

12The description is the abstract of the standard, taken from the link: http://ieeexplore.ieee.org/xpl/articleDetails.jsp?tp=&arnumber=5744556&contentType=Standards&sortType%3Dasc_p_Sequence%26filter%3DAND%28p_Publication_Number%3A5744554%29

reclosing duty present on typical utility distribution systems. Traditional concerns about steady-state voltage levels and light flicker due to voltage fluctuation also remain. These concerns are addressed by this guide by documenting typical levels of these aspects of voltage quality and indicating how to improve them. Other documents that treat these subjects in more detail are referenced.

4.2. The British Standard: Engineering Recommendation G5/4-1

4.2.1. These Recommendations are by the Energy Networks Association (ENA). The first version was published in February’ 2001 and the revision came in October’ 2005. It may be noted that the ETR 122 was the companion guide on the application of the G5/4 standard.

4.2.2. With deregulation of the power sector in Britain, a hierarchy of documents was created. These documents in turn permitted unbundling of various layers of power sector.

4.2.3. To quote from the Appendix A of ER G5/4:

The planning levels in this Recommendations are to be used by NOCs13 as reference levels against which they assess the suitability for connection to their systems of large loads and equipment which are rated over 16 A and are subject to their consent. They are specific to UK supply systems but are based on IEC Technical Report 61000-3-6.

Compatibility levels for public system harmonics are specified in IEC Basic Standards 61000-2-2 and 61000-2-12. The immunity test levels for equipment are higher levels based on the specified compatibility levels. If network distortion exceeds the relevant compatibility level, experience has shown that there will be a sudden increase in equipment failures and customer complaints.

The precise relationship between specified compatibility levels and planning levels depends on the disturbance phenomenon being considered and whether or not they are load related....The margins between planning and levels and compatibility level depend upon the electrical characteristics of the supply network, the background levels of


22

13 NOC as defined in ER G5/4: A generic term embracing Grid Operating Companies and Distribution Network Operators.

distortion, the nature of the disturbance (continuous or random), load profiles, and load density of the supply system area.

Planning levels stipulated by the NOCs are there fore subject to national and local supply system conditions.

4.2.4. It is seen that an elaborate three stage process (Cl. 5) has been laid out to assess connection of non-linear equipment. This assessment procedure is intended to be generally applicable to any non-linear equipment that has a harmonic current emission in to the electricity supply system irrespective of the direction of the fundamental frequency power flow. Therefore there is no differentiation between loads and generation as far as the procedure is concerned. Any specific references to load or generation should therefore be treated as implying the general case of non-linear equipment.

[Cl. 5.1.5]...Measurements of background harmonic levels are generally needed for Stage 2 and always for Stage 3 assessments. The responsibility for making these measurements lies with the NOC....In general, the background harmonics should be assessed over atleast a 7 day period when the PCC fault levels are representative of post-connection conditions.

4.2.5. As can be noted, the G5/4 repeatedly veers around to new connections. This is further explained by commentary on G5/4-1:

14...Where a user wishes to install new equipment to extend an existing installation, and where agreement to connect has already been established under previous rules, it is possible that the connection of additional equipment could involve a new and lower limit being applied to the whole installation under the terms of a new agreement.

This would be retrospective, and therefore difficult to enforce.

In these circumstances agreement to connect without increase in the aggregate harmonic current loading should be forthcoming, although the overall connection may be for a higher power.


23

14 Para 7 of Managing Harmonics-A guide to ENA Engineering Recommendation G5/4-1, 6th Edition: 2011. Published by GAMBICA, which is the national organisation representing the interests of companies in the instrumentation, control, automation and laboratory technology industry in the UK. It can be accessed at: http://www.gambica.org.uk/

Where a user wishes to replace existing equipment with new equipment of similar functionality, there should be no need to repeat the application procedure, if documentary evidence exists that the levels of harmonic currents generated by the new equipment do not exceed the existing levels.

4.2.6. Another key aspect of the ER G5/4 is the focus on voltage harmonics. The current harmonics limits in turn is assessed by capacity of the utility to supply without voltage at point of connection exceeding the stipulated limits. This is perhaps the only practical method of evaluation. It may be noted that when IEEE 519-1981 evolved to its 1992 version, the current limits were brought in. Juxtaposing the IEEE 519-1992 with ER G5/4 and IEC family of standards, it is clear why current limits were recommended. IEEE 519 being recommendation gives framework for system design and not for enforcement. As would be brought out in the following, implementation of limits on existing network is quite difficult and all other standards talk about connection of new loads. Also the standards which now have been enforced are far more detailed.

4.2.7. The ER G5/4 has very pragmatic view on the limits and hence mentions in Cl. 10 that ...In exceptional circumstances, where for example a customer is located in an area remote from other customers and it is certain that only that customer’s equipment will be connected to the local network, the Distribution Network Operator (DNO) may assess new load under Stage 2 using compatibility levels appropriate to the network voltage, instead of planning levels. To appreciate the difference between planning levels and compatibility levels, following graphs from IEC TR 61000-3-6: 2008 can be referred.

Following graph illustrates basic voltage quality concepts with time/ location statistics covering the whole system:


24

TR 61000-3-6 ! IEC:2008(E) – 17 –

Disturbance level

Probability density

System disturbance level

Immunity test levels

Compatibility level

Equipment immunity level

Planning levels

IEC 091/08

Figure 1 – Illustration of basic voltage quality concepts with time/ location statistics covering the whole system

Assessedlevel

Planninglevel

Disturbance level

Probability density

Sitedisturbancelevel

Compatibility level

Localequipmentimmunitylevel

IEC 092/08

Figure 2 – Illustration of basic voltage quality concepts with time statistics relevant to one site within the whole system

As Figure 2 illustrates, the probability distributions of disturbance and immunity levels at any one site are normally narrower than those in the whole power system, so that at most locations there is little or no overlap of disturbance and immunity level distributions. Interference is therefore not generally a major concern, and equipment is anticipated to function satisfactorily. Electromagnetic compatibility is therefore more probable than Figure 1 appears to suggest.

4.4 Emission levels

The co-ordination approach recommended in this report relies on individual emission levels being derived from the planning levels. For this reason, the same indices are applied both when evaluating actual measurements against the emission limits and against the planning levels.

One or more of the following indices can be used to compare the actual emission level with the customer’s emission limit. More than one index may be needed in order to assess the impact of higher emission levels allowed for short periods of time such as during bursts or start-up conditions.

• The 95 % weekly value of Uhsh (or Ihsh), the r.m.s. value of individual harmonics over "short" 10 min periods, should not exceed the emission limit.

LICENSED

TO RESEA

RCH D

ESIGN

S & STA

ND

ARD

S ORG

AN

ISATIO

N (RD

SO)

FOR IN

TERNA

L USE A

T THIS LO

CATIO

N O

NLY

, SUPPLIED

BY BO

OK

SUPPLY

BUREA

U.

Following graph illustrates basic voltage quality concepts with time statistics relevant to one site within the whole system:

TR 61000-3-6 ! IEC:2008(E) – 17 –

Disturbance level

Probability density

System disturbance level

Immunity test levels

Compatibility level

Equipment immunity level

Planning levels

IEC 091/08

Figure 1 – Illustration of basic voltage quality concepts with time/ location statistics covering the whole system

Assessedlevel

Planninglevel

Disturbance level

Probability density

Sitedisturbancelevel

Compatibility level

Localequipmentimmunitylevel

IEC 092/08

Figure 2 – Illustration of basic voltage quality concepts with time statistics relevant to one site within the whole system

As Figure 2 illustrates, the probability distributions of disturbance and immunity levels at any one site are normally narrower than those in the whole power system, so that at most locations there is little or no overlap of disturbance and immunity level distributions. Interference is therefore not generally a major concern, and equipment is anticipated to function satisfactorily. Electromagnetic compatibility is therefore more probable than Figure 1 appears to suggest.

4.4 Emission levels

The co-ordination approach recommended in this report relies on individual emission levels being derived from the planning levels. For this reason, the same indices are applied both when evaluating actual measurements against the emission limits and against the planning levels.

One or more of the following indices can be used to compare the actual emission level with the customer’s emission limit. More than one index may be needed in order to assess the impact of higher emission levels allowed for short periods of time such as during bursts or start-up conditions.

• The 95 % weekly value of Uhsh (or Ihsh), the r.m.s. value of individual harmonics over "short" 10 min periods, should not exceed the emission limit.

LICENSED

TO RESEA

RCH D

ESIGN

S & STA

ND

ARD

S ORG

AN

ISATIO

N (RD

SO)

FOR IN

TERNA

L USE A

T THIS LO

CATIO

N O

NLY

, SUPPLIED

BY BO

OK

SUPPLY

BUREA

U.

This buttresses further that application of harmonics limits is not straightforward exercise.

4.2.8. Stage 3 of assessment procedure which covers connection at > 33 kV, is worth quoting to appreciate the intent of the authors and the inherent pragmatism of the Recommendations:

15The Stage 3 of the assessment will be made by the NOC with the characteristics of the non-linear equipment being provided by the customer. Where the customer is connecting a system containing non-linear equipment, the NOC will be required either to provide the customer with the system harmonic impedance values at the PCC which will enable the customer to evaluate his system harmonic performance, or to model part of the customer’s system with in the Stage 3 assessment.


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15 Cl. 8.1 of Engineering Recommendations G5/4

It should be read with Section VIII of Ribeiro’s earlier quoted paper ‘Common Misapplications of the IEEE 519 Harmonic Standard: Voltage or Current Limits’:

Although IEEE 519 establishes or rather recommends that harmonic current limitation is the responsibility the end-users (customers) and that harmonic voltage is the responsibility of the system owners or operators (utilities), as a simplified procedure for distortion control, end-users are recommended to use both limits with sensitivity and discrimination to avoid both installing unnecessary filtering equipment or neglecting possible local resonances which could cause internal interference and damages. Furthermore, considering that the present current limits were determined based

on typical system impedances of 20 years ago, and that much has changed in

terms of system impedance, harmonic source characteristics and background distortion content, it is expected that the recommended limits for both voltage

and currents be utilized with .

Continuing with the ER G5/4, section 8.2 reads as:

The assessment of the connection of new non-linear equipment consists of:

4.2.8.i. Measuring the levels of distortion already existing on the system,

4.2.8.ii. Calculating the distortion which will be caused by the new equipment, and

4.2.8.iii. Predicting the possible effect on harmonic levels by an addition of the results of (4.2.8.i) and (4.2.8.ii)

Connection of the equipment is acceptable if the results of (4.2.8.iii) are less

than the THD and the harmonic voltage planning levels for individual harmonic order.

4.2.9. Other key salient points of ER G5/4 being:

4.2.9.i. In addition to the assessment based on conditions at the PCC, assessment at other locations to be undertaken to establish directly the possibility of resonance effects (Cl 8.2).

4.2.9.ii. Recommends use of harmonic analysis program even for simple network calculations (Cl 8.3.1).


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4.2.9.iii. Assessment to include factors like time (time of day), duration of operation (Cl. 8.3.2).

4.2.9.iv. Only the +ve and -ve triplen components associated with lack of balance between the three phases needs to be considered (Cl. 8.3.2).

4.2.9.v. If more than one traction supply point is involved, it is likely that different phase pairs will be used for unbalance mitigation. Before summation of harmonics with relatively stable background level, the assessed contribution from each should be made taking in to account both the degree of coordination between the respective traction load currents and the phase difference between the harmonic components (Cl. 8.3.3).

4.3. IEC 61000 Family of Standards

This is truly most elaborate family of standards. Very carefully drafted and voted upon by member nations, these standards strike the ‘thou shalt not...’ tone. The degree of detail to be found in these standards make them very comprehensive.

It is beyond the scope of this White Paper to dwell upon all of these, however, IEC Technical Report 61000-3-6 2nd Edition published in February 2008 is a very recent document and merits closer look.

4.3.1. IEC/TR 61000-3-6 2nd Edition: February 2008-Electromagnetic

compatibility (EMC) –Part 3-6: Limits – Assessment of emission limits

for the connection of distorting installations to MV, HV and EHV

power systems.

4.3.1.i. This document is a Technical Report and not a Standard. To appreciate the difference, it is instructive to quote from the foreword of this document: The main task of the IEC technical committees is to prepare international standards. However, a technical committee may propose the publication of a technical report when it has collected data of a different kind from that which is normally published as an International Standard, for example ‘state of the art’.

4.3.1.ii. Further, the document mentions, this edition is significantly more streamlined than the first edition, and it reflects the experiences gained in the application of the first edition (published in 1996). As part of this streamlining process, this second edition does not address communications circuit interference. It may be


27

noted that IEEE 519-1992 still carries this legacy. IEC sub committee, SC 77A responsible for this TR invited inputs from CIGRE Study Committee C4 and CIRED Study Committee S2 in 2002. A joint task force was set up in 2003. This makes this TR most authoritative, substantive and current of all documents on the harmonics aspect of power quality.

4.3.1.iii. As can be seen, the TR focuses on voltage aspect. To quote from the Cl. 1, the Scope, The report addresses the allocation of the capacity of the system to absorb disturbances. ... This report gives guidance for the coordination of the harmonic voltages between different voltage levels in order to meet the compatibility levels at the point of utilisation.

4.3.1.iv. The key premise being...The development of emission limits (voltage or current) for individual equipment or a customer’s installation should be based on the

effect that these emission limits will have on the quality of the voltage. This should be seen with the observations of Ribeiro quoted earlier in the discussion of IEEE 519-1992. This philosophy is to be found in ER G5/4-1, which is the British Standard for harmonics.

4.3.1.v. The TR brings the concept of ‘planning levels’ (Cl 4.2.1) which are the harmonic voltage levels that can be used for the purpose of determining emission limits, taking in to consideration all distorting installations. Planning levels are specified by the system operator or owner for all system voltage levels and can be considered as internal quality objectives if the system operator or owner and may even be made available to individual customer on request. Planning level for harmonics are equal to or lower than compatibility levels and they should allow coordination of harmonic voltages between different voltage levels....this report outlines procedures for using these planning levels to establish the emission limits for individual customers.

4.3.1.vi. Cl 6.2 Note 3: If the installation exceeds the harmonic voltage emission limits it may be because:

• The system impedance is high due to the presence if harmonic resonance conditions,

• The installation is resonating with the supply system, or

• The harmonic currents generated by the installation are too high.


28

4.3.1.vii. It is thus seen that the before putting the cause of voltage harmonics on the customer’s door step, two more possible causes need to be ruled out.

4.3.1.viii. Cl 6.4 clearly calls for information on the system harmonic impedance as a prerequisite both for the system operator or owner for assessing emission limits and for the customer in order to assess the emission levels of the considered installation-

• Impedance for converting emission limits from voltage to current

• Impedance for pre-connection assessment of emission levels

• Impedance for assessing actual emission levels

4.3.1.ix. Cl. 6.4.4 gives general guidelines for assessing the system harmonic impedance

4.3.1.x. Thus it is seen that TR 61000-3-6 faces the issue of harmonic disturbances with acknowledgement to the complexity of the problem. There is clear mention that the harmonic impedance of the system may vary significantly with time (Cl 6.4.4). It is a point which has been noted by Ribeiro in his paper quoted earlier. Further,

with growth of power sector in the country it is safe to presume that these

values would see frequent revisions.

4.3.1.xi. The document aims to have equitable apportionment of the actual harmonic absorption capability to various users. For each customer only a fraction of the global emission limits will be allowed. A reasonable approach is to take the ratio between the agreed power and the total supply capability...Such a criterion is related to the fact that the agreed power of a customer is often linked with his share in the investment costs of the power system. This translates closest to the Contract Demand. This should settle the issue of denominator in determination of TDD as per IEEE 519-1992.

4.3.1.xii. Very important point is made in Cl 8.2.2.2 & 9.2.3: It may be preferred to specify harmonic current limits to the distorting installation, even if the aim is to limit the harmonic voltages in the system. It will be the responsibility of the system operator or owner to provide data concerning the frequency-dependent impedance of the system, in order to enable expressing these limits in terms of harmonic currents.

4.3.1.xiii. The Cl 8.3 and 9.3 mentions that... In all the cases, when appropriate the system operator or owner may decide to allocate higher emission limits under stage 3. A careful


29

study of the connection should always be carried out, taking account of the pre-existing distortion and of the expected contribution from the considered installation for different possible operating conditions. Acceptance of higher than normal emission limits may be given to customers only on a conditional basis and limitations may be specified by the system operator or owner, for instance-temporary Stage 3 limits for-

• as long as spare supply capacity remains available in the system for allowing more emissions,

• as long as most other customers do not make full use of their normal stage 2 emissions limits,

• the time needed for a new installation, in order to implement additional corrective measures whenever needed.

4.3.1.xiv. It is thus seen that the TR acknowledges background harmonics and considers impact of a load thereon. The TR 61000-3-6 not just focuses on voltage instead of current, it also works on equitable apportionment of the available capacity of harmonic absorption. Also relaxation of limits is permissible if other consumers are not able to utilise this limit. This is most economical implementation. The document instead of arriving at the fixed current limits as in IEEE 519-1992 and mentioned in CEA Regulations, gives limits on voltage harmonics. The relationship between voltage harmonics and current harmonics is also established but only after realistic determination of the system’s harmonic impedance, a subject dealt in considerable detail.

4.3.1.xv. Other documents of IEC 61000 family of interest are listed in Annexure A. It can be seen in the Annexure that scores of standards need to be created to make limits enforceable. IEEE 519-1992, at best can be used as recommended guideline to declare the intent, however, it is grossly inadequate for creating an enforceable regime.


30

5. Conclusion5.1. Harmonic levels in power system has been extensively researched and very carefully

drafted standards, notably IEC- 61000 family of standards and British Standard ER G5/4-1 have emerged in the past few years. Some of these came after the CEA Regulations of 2007 were promulgated, which appear to lean on much older IEEE 519-1992.

As level of harmonic limits have been laid down by CEA, following immediate issues emerge:

5.1.1. A limit has been placed on current THD, whereas current distortions can’t be meaningful without referencing them to a fixed value. This is because of the fact that in general THD changes with load and infact under low loads, THD can be very high.

5.1.2. Different standards have addressed this issue. IEEE 519-1992 for instance has taken average current of the maximum demand of preceding 12 months, whereas, IEC Technical Report 61000-3-6 takes ‘agreed power’ between customer and the grid as the value to be used. Agreed power approach has been recommended by IEC as system’s technical rating is done based on this value. This value for Indian scenario is Contract Demand.

5.1.3. Key issue which is addressed by various Standards is that every power system

has a capacity of sourcing harmonic currents, with limit being determined by

the level of harmonic currents which lead to unacceptable distortion of

voltage.

5.1.3.1. IEC/TR 61000-3-6 (February 2008) and BR G5/4-1 (2005) lay elaborate method for arriving at this limit. Having assessed this limit, various Standards/Practices arrive at methods to apportion this capacity amongst various users.

5.1.3.2. It may be noted that IEEE 519-1992, a 20 year old document tried to address the issue by suggesting limits on current TDD. This being a design guideline, its applicability at user end in isolation has been questioned in recent literature.

5.1.4. We also have to consider the latest international document viz. IEC TR 61000-3-6 (February‘2008) to peruse the need of apportioning the capacity to


31

source harmonics at various levels in the power system. It may be noted that IEC sub committee, SC 77A responsible for this TR invited inputs from CIGRE Study Committee C4 and CIRED Study Committee S2 in 2002. A joint task force was set up in 2003. This makes this TR most authoritative, substantive and current of all documents on the harmonics aspect of power quality.

5.2. With regards to applicability of IEEE 519-1992, it needs to be noted that this is a system design ‘Recommended Practice’. Latest commentaries have been quite vocal to voice the inadequacies of this document. Ribeiro, as discussed earlier has cautioned against use of only current limits. Further, to quote Cl 10.4.2 of IEEE 519-1992,... Although the effects of harmonics on electric equipment, appliances, etc. are not fully understood at this time, it is recognized that the stated current distortion limits can be exceeded for periods of time without causing damage to equipment. When evaluating the user compliance with the stated limits, it is recommended that probability distribution plots be developed from he recorded data and analyzed. If the limits are only exceeded for a short period of time, the condition could be considered acceptable.

5.3. Thus, it clearly emerges that:

5.3.1. IEEE 519-1992 can at best be used a preliminary system design guide. In view of much better researched documents like IEC/TR 61000-3-6, published in 2008, which has been drafted taking inputs from CIRED and CIGRE, making it most authoritative document on the subject. This document has dealt the subject taking cognisance of due complexity of the system.

5.3.2. IEEE 519-1992 is inadequate to be used as document for enforcing the limits.

5.3.3. Measurements carried out by Utilities should consider Cl. 10.4.2 of IEEE 519-1992. Further, the denominator of the TDD calculation should be contract demand.

5.4. It may be seen that, in Cl. 6(6) of Central Electricity Authority (Technical Standards for Connectivity to the Grid) Regulations, 2007, possible need of study to assess transmission system capability, transient stability, voltage stability, losses, voltage regulation, harmonics, voltage flicker, electromagnetic transients, machine dynamics, ferro resonance, metering requirements, protective relaying, sub-station grounding and fault duties, has been given. Whereas in the Cl. 3 of Part IV of the Schedule, only


32

limits on harmonics are given. As discussed earlier, giving absolute limit on current THD is not technically correct approach. Ministry of Railways are approaching the Central Electricity Authority for needed clarity. Also, on the issue of measurements, matter is being discussed with CPRI.

5.5. On the matter of penal provisions following emerge:

5.5.1. IEEE 519-1992 being system design guideline is not only quaint but also inadequate to be used as basis for penalty.

5.5.2. For penalties, first a limit needs to be arrived at. As can be seen in latest literature, IEC and British guidelines (IEC and British Standards are to be factored in as mentioned at Cl. 1, Part I of Schedule to CEA(Technical Standards for Connectivity to the Grid) Regulations, 2007) a very different approach has been taken (vis-a-vis that of IEEE 519-1992). Thus basing the limits on the approach given by IEEE 519-1992 would lead to misdirected investments.

5.5.3. In the approaches of flat penalty, the element of ‘extent of trespass’ has not been factored in. Also, as argued by Ribeiro, in his paper quoted earlier, it is not correct to take current limits as the final deciding factors. This approach is technically grossly sub-optimal and should not form basis for justifying investments. Another important technical aspect is discussed below.

5.6. Another important aspect which emerges on perusal of Cl. 6(6) of Central Electricity Authority (Technical Standards for Connectivity to the Grid) Regulations, 2007, is the fact that this Regulation is not as yet implemented. Given the recent disturbances in the Grid, these aspects will also be dealt in more elaborate matter. This would have possible impact on the design of mitigation equipment installed today as limits of other aspects are not yet known.

5.7. Railways need to keep, nevertheless a sharp eye on the system harmonics for the safety of the traction supply network. Incidences of resonance have been documented and need to be kept in check to avoid system disturbances.

5.8. Long before the CEA Regulations came or the IEEE 519-1992 made an impact, IR was already working on mitigation of harmonics at the load end. IRGP-140, the contract signed in July 1993 with erstwhile ABB Transportation, Switzerland, for the Transfer of Technology (ToT) of new generation of electric locomotives - included a harmonic


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filter. Locomotives based on this technology are now in serial production. Similarly, all new AC EMUs introduced in Mumbai suburban following DC to AC conversion are provided with harmonic mitigation. All new 25 kV AC Metro stock being introduced in the country are also equipped with harmonic management components. It needs to be flagged that IR’s requirement of harmonic containment is also for the safe operation of signal circuits. Assessment of harmonics has been key component of rolling stock clearance due to this reason. Thus, it can be seen that IR has been doing load level measurements and containment much before these Regulations came about.

5.9. To appreciate, the approach taken internationally, one must peruse the ecosystem of standards created by IEC as cryptically mentioned in Annexure A.


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6. Annexure AFollowing tables have been given to help appreciate that harmonics form a part of larger field of EMC and should be dealt holistically. The sheer number of standards on the issue is staggering as can be seen below.

IEC 61000 Part - 1

Standard Number Standard Title

IEC/TR 61000-1-1 Ed. 1.0 b Electromagnetic compatibility (EMC) - Part 1: General - Section 1: Application and interpretation of fundamental definitions and terms

IEC/TS 61000-1-2 Ed. 2.0 enElectromagnetic compatibility (EMC) - Part 1-2: General - Methodology for the achievement of functional safety of electrical and electronic systems including equipment with regard to electromagnetic phenomena

IEC/TR 61000-1-3 Ed. 1.0 en Electromagnetic compatibility (EMC) - Part 1-3: General - The effects of high-altitude EMP (HEMP) on civil equipment and systems

IEC/TR 61000-1-4 Ed. 1.0 enElectromagnetic compatibility (EMC) - Part 1-4: General - Historical rationale for the limitation of power-frequency conducted harmonic current emissions from equipment, in the frequency range up to 2 kHz

IEC/TR 61000-1-5 Ed. 1.0 en Electromagnetic compatibility (EMC) - Part 1-5: General - High power electromagnetic (HPEM) effects on civil systems

IEC 61000 Part - 2

EC/TR 61000-2-1 Ed. 1.0 b

Electromagnetic compatibility (EMC) - Part 2: Environment - Section 1: Description of the environment - Electromagnetic environment for low-frequency conducted disturbances and signalling in public power supply systems

IEC 61000-2-2 Ed. 2.0 bElectromagnetic compatibility (EMC) - Part 2-2: Environment - Compatibility levels for low-frequency conducted disturbances and signalling in public low-voltage power supply systems

IEC/TR 61000-2-3 Ed. 1.0 bElectromagnetic compatibility (EMC) - Part 2: Environment - Section 3: Description of the environment - Radiated and non-network-frequency-related conducted phenomena

IEC 61000-2-4 Ed. 2.0 bElectromagnetic compatibility (EMC) - Part 2-4: Environment - Compatibility levels in industrial plants for low-frequency conducted disturbances

IEC/TS 61000-2-5 Ed. 1.0 bElectromagnetic compatibility (EMC) - Part 2: Environment - Section 5: Classification of electromagnetic environments. Basic EMC publication

IEC/TR 61000-2-5 Ed. 2.0 b Electromagnetic compatibility (EMC) - Part 2-5: Environment - Description and classification of electromagnetic environments

IEC/TR 61000-2-6 Ed. 1.0 bElectromagnetic compatibility (EMC) - Part 2: Environment - Section 6: Assessment of the emission levels in the power supply of industrial plants as regards low-frequency conducted disturbances

! H a r m o n i c s i n Tr a c t i o n P o w e r S u p p l y

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IEC/TR 61000-2-7 Ed. 1.0 b Electromagnetic compatibility (EMC) - Part 2: Environment - Section 7: Low frequency magnetic fields in various environments

IEC/TR 61000-2-8 Ed. 1.0 bElectromagnetic compatibility (EMC) - Part 2-8: Environment - Voltage dips and short interruptions on public electric power supply systems with statistical measurement results

IEC 61000-2-9 Ed. 1.0 bElectromagnetic compatibility (EMC) - Part 2: Environment - Section 9: Description of HEMP environment - Radiated disturbance. Basic EMC publication

IEC 61000-2-10 Ed. 1.0 b Electromagnetic compatibility (EMC) - Part 2-10: Environment - Description of HEMP environment - Conducted disturbance

IEC 61000-2-11 Ed. 1.0 b Electromagnetic compatibility (EMC) - Part 2-11: Environment - Classification of HEMP environments

IEC 61000-2-12 Ed. 1.0 bElectromagnetic compatibility (EMC) - Part 2-12: Environment - Compatibility levels for low-frequency conducted disturbances and signalling in public medium-voltage power supply systems

IEC 61000-2-13 Ed. 1.0 enElectromagnetic compatibility (EMC) - Part 2-13: Environment - High-power electromagnetic (HPEM) environments - Radiated and conducted

IEC/TR 61000-2-14 Ed. 1.0 en

Electromagnetic compatibility (EMC) - Part 2-14: Environment - Overvoltages on public electricity distribution networks

IEC 61000 Part - 3

IEC 61000-3-2 Ed. 3.2 b Electromagnetic compatibility (EMC) - Part 3-2: Limits - Limits for harmonic current emissions (equipment input current ≤ 16 A per phase)

IEC 61000-3-2 Amd.1 Ed. 3.0 bAmendment 1 - Electromagnetic compatibility (EMC) - Part 3-2: Limits - Limits for harmonic current emissions (equipment input current ≤ 16 A per phase)

IEC 61000-3-2 Amd.2 Ed. 3.0 bAmendment 2 - Electromagnetic compatibility (EMC) - Part 3-2: Limits - Limits for harmonic current emissions (equipment input current ≤ 16 A per phase)

IEC 61000-3-2 Ed. 3.2 b Cor.1Corrigendum 1 - Electromagnetic compatibility (EMC) - Part 3-2: Limits - Limits for harmonic current emissions (equipment input current ≤16 A per phase)

IEC 61000-3-3 Ed. 2.0 b

Electromagnetic compatibility (EMC) - Part 3-3: Limits - Limitation of voltage changes, voltage fluctuations and flicker in public low-voltage supply systems, for equipment with rated current ≤16 A per phase and not subject to conditional connection

IEC 61000-3-3 Amd.1 Ed. 1.0 bAmendment 1 - Electromagnetic compatibility (EMC) - Part 3: Limits - Section 3: Limitation of voltage fluctuations and flicker in low-voltage supply systems for equipment with rated current <= 16 A

IEC 61000-3-3 Amd.2 Ed. 1.0 b

Amendment 2 - Electromagnetic compatibility (EMC) - Part 3-3: Limits - Limitation of voltage changes, voltage fluctuations and flicker in public low-voltage supply systems, for equipment with rated current <= 16 A per phase and not subject to conditional

IEC/TS 61000-3-4 Ed. 1.0 bElectromagnetic compatibility (EMC) - Part 3-4: Limits - Limitation of emission of harmonic currents in low-voltage power supply systems for equipment with rated current greater than 16 A

IEC/TS 61000-3-5 Ed. 2.0 bElectromagnetic compatibility (EMC) - Part 3-5: Limits - Limitation of voltage fluctuations and flicker in low-voltage power supply systems for equipment with rated current greater than 75 A


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IEC/TS 61000-3-5 Ed. 2.0 b Cor.1

Corrigendum 1 - Electromagnetic compatibility (EMC) - Part 3-5: Limits - Limitation of voltage fluctuations and flicker in low-voltage power supply systems for equipment with rated current greater than 75 A

IEC/TS 61000-3-5 Ed. 2.0 b Cor.2

Corridendum 2 - Electromagnetic compatibility (EMC) - Part 3-5: Limits - Limitation of voltage fluctuations and flicker in low-voltage power supply systems for equipment with rated current greater than 75 A

IEC/TR 61000-3-6 Ed. 2.0 enElectromagnetic compatibility (EMC) - Part 3-6: Limits - Assessment of emission limits for the connection of distorting installations to MV, HV and EHV power systems

IEC/TR 61000-3-7 Ed. 2.0 enElectromagnetic compatibility (EMC) - Part 3-7: Limits - Assessment of emission limits for the connection of fluctuating installations to MV, HV and EHV power systems

IEC 61000-3-8 Ed. 1.0 bElectromagnetic compatibility (EMC) - Part 3: Limits - Section 8: Signalling on low-voltage electrical installations - Emission levels, frequency bands and electromagnetic disturbance levels

IEC 61000-3-11 Ed. 1.0 b

Electromagnetic compatibility (EMC) - Part 3-11: Limits - Limitation of voltage changes, voltage fluctuations and flicker in public low-voltage supply systems - Equipment with rated current <= 75 A and subjet to conditional connection

IEC 61000-3-12 Ed. 2.0 bElectromagnetic compatibility (EMC) - Part 3-12: Limits - Limits for harmonic currents produced by equipment connected to public low-voltage systems with input current >16 A and ≤ 75 A per phase

IEC/TR 61000-3-13 Ed. 1.0 enElectromagnetic compatibility (EMC) - Part 3-13: Limits - Assessment of emission limits for the connection of unbalanced installations to MV, HV and EHV power systems

IEC/TR 61000-3-13 Ed. 1.0 en Cor.1

Corrigendum 1 - Electromagnetic compatibility (EMC) - Part 3-13: Limits - Assessment of emission limits for the connection of unbalanced installations to MV, HV and EHV power systems

IEC/TR 61000-3-14 Ed. 1.0 enElectromagnetic compatibility (EMC) - Part 3-14: Assessment of emission limits for harmonics, interharmonics, voltage fluctuations and unbalance for the connection of disturbing installations to LV power systems

IEC/TR 61000-3-15 Ed. 1.0 enElectromagnetic compatibility (EMC) - Part 3-15: Limits - Assessment of low frequency electromagnetic immunity and emission requirements for dispersed generation systems in LV network

IEC 61000 Part - 4

IEC 61000-4-1 Ed. 3.0 b Electromagnetic compatibility (EMC) - Part 4-1: Testing and measurement techniques - Overview of IEC 61000-4 series

IEC 61000-4-2 Ed. 2.0 b Electromagnetic compatibility (EMC) - Part 4-2: Testing and measurement techniques - Electrostatic discharge immunity test

IEC 61000-4-2 Amd.1 Ed. 1.0 bAmendment 1 - Electromagnetic compatibility (EMC) - Part 4: Testing and measurement techniques - Section 2: Electrostatic discharge immunity test. Basic EMC Publication

IEC 61000-4-2 Amd.2 Ed. 1.0 bAmendment 2 - Electromagnetic compatibility (EMC) - Part 4: Testing and measurement techniques - Section 2: Electrostatic discharge immunity test. Basic EMC Publication

IEC 61000-4-3 Ed. 3.2 bElectromagnetic compatibility (EMC) - Part 4-3: Testing and measurement techniques - Radiated, radio-frequency, electromagnetic field immunity test


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IEC 61000-4-3 Amd.1 Ed. 3.0 bAmendment 1 - Electromagnetic compatibility (EMC) - Part 4-3: Testing and measurement techniques - Radiated, radio-frequency, electromagnetic field immunity test

IEC 61000-4-3 Amd.2 Ed. 3.0 bAmendment 2 - Electromagnetic compatibility (EMC) - Part 4-3: Testing and measurement techniques - Radiated, radio-frequency, electromagnetic field immunity test

IEC 61000-4-4 Ed. 2.0 b Cor.2Corrigendum 2 - Electromagnetic compatibility (EMC) - Part 4-4: Testing and measurement techniques - Electrical fast transient/burst immunity test

IEC 61000-4-4 Ed. 2.1 b Electromagnetic compatibility (EMC) - Part 4-4: Testing and measurement techniques - Electrical fast transient/burst immunity test

IEC 61000-4-4 Amd.1 Ed. 2.0 bAmendment 1 - Electromagnetic compatibility (EMC) - Part 4-4: Testing and measurement techniques - Electrical fast transient/burst immunity test

IEC 61000-4-5 Ed. 2.0 b Electromagnetic compatibility (EMC) - Part 4-5: Testing and measurement techniques - Surge immunity test

IEC 61000-4-6 Ed. 3.0 bElectromagnetic compatibility (EMC) - Part 4-6: Testing and measurement techniques - Immunity to conducted disturbances, induced by radio-frequency fields

IEC 61000-4-6 Amd.1 Ed. 2.0 bAmendment 1 - Electromagnetic compatibility (EMC) - Part 4-6: Testing and measurement techniques - Immunity to conducted disturbances, induced by radio-frequency fields

IEC 61000-4-6 Amd.2 Ed. 2.0 bAmendment 2 - Electromagnetic compatibility (EMC) - Part 4-6: Testing and measurement techniques - Immunity to conducted disturbances, induced by radio-frequency fields

IEC 61000-4-7 Ed. 2.1 b

Electromagnetic compatibility (EMC) - Part 4-7: Testing and measurement techniques - General guide on harmonics and interharmonics measurements and instrumentation, for power supply systems and equipment connected thereto

IEC 61000-4-7 Amd.1 Ed. 2.0 b

Amendment 1 - Electromagnetic compatibility (EMC) - Part 4-7: Testing and measurement techniques - General guide on harmonics and interharmonics measurements and instrumentation, for power supply systems and equipment connected thereto

IEC 61000-4-8 Ed. 2.0 b Electromagnetic compatibility (EMC) - Part 4-8: Testing and measurement techniques - Power frequency magnetic field immunity test

IEC 61000-4-8 Amd.1 Ed. 1.0 bAmendment 1 - Electromagnetic compatibility (EMC) - Part 4: Testing and measurement techniques - Section 8: Power frequency magnetic field immunity test. Basic EMC Publication

IEC 61000-4-9 Ed. 1.1 b Electromagnetic compatibility (EMC) - Part 4-9: Testing and measurement techniques - Pulse magnetic field immunity test

IEC 61000-4-9 Amd.1 Ed. 1.0 bAmendment 1 - Electromagnetic compatibility (EMC) - Part 4: Testing and measurement techniques - Section 9: Pulse magnetic field immunity test. Basic EMC Publication

IEC 61000-4-10 Ed. 1.1 bElectromagnetic compatibility (EMC) - Part 4-10: Testing and measurement techniques - Damped oscillatory magnetic field immunity test

IEC 61000-4-10 Amd.1 Ed. 1.0 bAmendment 1 - Electromagnetic compatibility (EMC) - Part 4: Testing and measurement techniques - Section 10: Damped oscillatory magnetic field immunity test. Basic EMC Publication

IEC 61000-4-11 Ed. 2.0 bElectromagnetic compatibility (EMC) - Part 4-11: Testing and measurement techniques - Voltage dips, short interruptions and voltage variations immunity tests


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IEC 61000-4-12 Ed. 2.0 b Electromagnetic compatibility (EMC) - Part 4-12: Testing and measurement techniques - Ring wave immunity test

IEC 61000-4-28 Ed. 1.2 bElectromagnetic compatibility (EMC) - Part 4-28: Testing and measurement techniques - Variation of power frequency, immunity test for equipment with input current not exceeding 16 A per phase

IEC 61000-4-13 Ed. 1.1 bElectromagnetic compatibility (EMC) - Part 4-13: Testing and measurement techniques - Harmonics and interharmonics including mains signalling at a.c. power port, low frequency immunity tests

IEC 61000-4-13 Amd.1 Ed. 1.0 bAmendment 1 - Electromagnetic compatibility (EMC) - Part 4-13: Testing and measurement techniques - Harmonics and interharmonics including mains signalling at a.c. power port, low frequency immunity tests

IEC 61000-4-14 Ed. 1.2 bElectromagnetic compatibility (EMC) - Part 4-14: Testing and measurement techniques - Voltage fluctuation immunity test for equipment with input current not exceeding 16 A per phase

IEC 61000-4-14 Amd.1 Ed. 1.0 b Amendment 1 - Electromagnetic compatibility (EMC) - Part 4-14: Testing and measurement techniques - Voltage fluctuation immunity test

IEC 61000-4-14 Amd.2 Ed. 1.0 bAmendment 2 - Electromagnetic compatibility (EMC) - Part 4-14: Testing and measurement techniques - Voltage fluctuation immunity test for equipment with input current not exceeding 16 A per phase

IEC 61000-4-15 Ed. 2.0 bElectromagnetic compatibility (EMC) - Part 4-15: Testing and measurement techniques - Flickermeter - Functional and design specifications

IEC 61000-4-15 Ed. 2.0 b Cor.1Corrigendum 1 - Electromagnetic compatibility (EMC) - Part 4-15: Testing and measurement techniques - Flickermeter - Functional and design specifications

IEC 61000-4-15 Amd.1 Ed. 1.0 bAmendment 1 - Electromagnetic compatibility (EMC) - Part 4: Testing and measurement techniques - Section 15: Flickermeter - Functional and design specifications

IEC 61000-4-16 Ed. 1.2 bElectromagnetic compatibility (EMC) - Part 4-16: Testing and measurement techniques - Test for immunity to conducted, common mode disturbances in the frequency range 0 Hz to 150 kHz

IEC 61000-4-16 Amd.1 Ed. 1.0 bAmendment 1 - Electromagnetic compatibility (EMC) - Part 4-16: Testing and measurement techniques - Test for immunity to conducted, common mode disturbances in the frequency range 0 Hz to 150 kHz

IEC 61000-4-16 Amd.2 Ed. 1.0 bAmendment 2 - Electromagnetic compatibility (EMC) - Part 4-16: Testing and measurement techniques - Test for immunity to conducted, common mode disturbances in the frequency range 0 Hz to 150 kHz

IEC 61000-4-17 Ed. 1.2 b Electromagnetic compatibility (EMC) - Part 4-17: Testing and measurement techniques - Ripple on d.c. input power port immunity test

IEC 61000-4-17 Amd.1 Ed. 1.0 bAmendment 1 - Electromagnetic compatibility (EMC) - Part 4-17: Testing and measurement techniques - Ripple on d.c. input power port immunity test

IEC 61000-4-17 Amd.2 Ed. 1.0 bAmendment 2 - Electromagnetic compatibility (EMC) - Part 4-17: Testing and measurement techniques - Ripple on d.c. input power port immunity test

IEC 61000-4-18 Ed. 1.1 b Electromagnetic compatibility (EMC) - Part 4-18: Testing and measurement techniques - Damped oscillatory wave immunity test

IEC 61000-4-18 Amd.1 Ed. 1.0 b Amendment 1 - Electromagnetic compatibility (EMC) - Part 4-18: Testing and measurement techniques - Damped oscillatory wave immunity test

IEC 61000-4-20 Ed. 2.0 bElectromagnetic compatiility (EMC) - Part 4-20: Testing and measurement techniques - Emission and immunity testing in transverse electromagnetic (TEM) waveguides


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IEC 61000-4-20 Amd.1 Ed. 1.0 bAmendment 1 - Electromagnetic compatibility (EMC) - Part 4-20: Testing and measurement techniques - Emission and immunity testing in transverse electromagnetic (TEM) waveguides

IEC 61000-4-22 Ed. 1.0 bElectromagnetic compatibility (EMC) - Part 4-22: Testing and measurement techniques - Radiated emissions and immunity measurements in fully anechoic rooms (FARs)

IEC 61000-4-23 Ed. 1.0 bElectromagnetic compatibility (EMC) - Part 4-23: Testing and measurement techniques - Test methods for protective devices for HEMP and other radiated disturbances

IEC 61000-4-24 Ed. 1.0 bElectromagnetic compatibility (EMC) - Part 4: Testing and measurement techniques - Section 24: Test methods for protective devices for HEMP conducted disturbance - Basic EMC Publication

IEC 61000-4-25 Ed. 1.0 bElectromagnetic compatibility (EMC) - Part 4-25: Testing and measurement techniques - HEMP immunity test methods for equipment and systems

IEC 61000-4-25 Amd.1 Ed. 1.0 bAmendment 1 - Electromagnetic compatibility (EMC) - Part 4-25: Testing and measurement techniques - HEMP immunity test methods for equipment and systems

IEC 61000-4-27 Amd.1 Ed. 1.0 bAmendment 1 - Electromagnetic compatibility (EMC) - Part 4-27: Testing and measurement techniques - Unbalance, immunity test for equipment with input current not exceeding 16 A per phase

IEC 61000-4-28 Amd.1 Ed. 1.0 bAmendment 1 - Electromagnetic compatibility (EMC) - Part 4-28: Testing and measurement techniques - Variation of power frequency, immunity test

IEC 61000-4-28 Amd.2 Ed. 1.0 bAmendment 2 - Electromagnetic compatibility (EMC) - Part 4-28: Testing and measurement techniques - Variation of power frequency, immunity test for equipment with input current not exceeding 16 A per phase

IEC 61000-4-29 Ed. 1.0 bElectromagnetic compatibility (EMC) - Part 4-29: Testing and measurement techniques - Voltage dips, short interruptions and voltage variations on d.c. input power port immunity tests

IEC 61000-4-30 Ed. 2.0 b Electromagnetic compatibility (EMC) - Part 4-30: Testing and measurement techniques - Power quality measurement methods

IEC/TR 61000-4-32 Ed. 1.0 enElectromagnetic compatibility (EMC) - Part 4-32: Testing and measurement techniques - High-altitude electromagnetic pulse (HEMP) simulator compendium

IEC 61000-4-33 Ed. 1.0 enElectromagnetic compatibility (EMC) - Part 4-33: Testing and measurement techniques - Measurement methods for high-power transient parameters

IEC 61000-4-34 Ed. 1.1 b

Electromagnetic compatibility (EMC) - Part 4-34: Testing and measurement techniques - Voltage dips, short interruptions and voltage variations immunity tests for equipment with mains current more than 16 A per phase

IEC 61000-4-34 Amd.1 Ed. 1.0 b

Amendment 1 - Electromagnetic compatibility (EMC) - Part 4-34: Testing and measurement techniques - Voltage dips, short interruptions and voltage variations immunity tests for equipmentwith mains current more than 16 A per phase

IEC/TR 61000-4-35 Ed. 1.0 en Electromagnetic compatibility (EMC) - Part 4-35: Testing and measurement techniques - HPEM simulator compendium


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IEC 61000 Part - 5

IEC/TR 61000-5-1 Ed. 1.0 b Electromagnetic compatibility (EMC) - Part 5: Installation and mitigation guidelines - Section 1: General considerations - Basic EMC publication

IEC/TR 61000-5-2 Ed. 1.0 b Electromagnetic compatibility (EMC) - Part 5: Installation and mitigation guidelines - Section 2: Earthing and cabling

IEC/TR 61000-5-3 Ed. 1.0 b Electromagnetic compatibility (EMC) - Part 5-3: Installation and mitigation guidelines - HEMP protection concepts

IEC/TS 61000-5-4 Ed. 1.0 bElectromagnetic compatibility (EMC) - Part 5: Installation and mitigation guidelines - Section 4: Immunity to HEMP - Specifications for protective devices against HEMP radiated disturbance. Basic EMC Publication

IEC 61000-5-5 Ed. 1.0 bElectromagnetic compatibility (EMC) - Part 5: Installation and mitigation guidelines - Section 5: Specification of protective devices for HEMP conducted disturbance. Basic EMC Publication

IEC/TR 61000-5-6 Ed. 1.0 en Electromagnetic compatibility (EMC) - Part 5-6: Installation and mitigation guidelines - Mitigation of external EM influences

IEC 61000-5-7 Ed. 1.0 bElectromagnetic compatibility (EMC) - Part 5-7: Installation and mitigation guidelines - Degrees of protection provided by enclosures against electromagnetic disturbances (EM code)

IEC/TS 61000-5-8 Ed. 1.0 en Electromagnetic compatibility (EMC) - Part 5-8: Installation and mitigation guidelines - HEMP protection methods for the distributed infrastructure

IEC/TS 61000-5-9 Ed. 1.0 en Electromagnetic compatibility (EMC) - Part 5-9: Installation and mitigation guidelines - System-level susceptibility assessments for HEMP and HPEM


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