Harmonics effect to the network Practical Case

European International Journal of Science and Technology Vol. 9 No. 11 November 2020

Cite this article: Alkhalifah, A. & Habiballah, I.O. (2020). Harmonics effect to the network – Practical Case. European International Journal of Science and Technology, 9(11), 1-8.

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Harmonics effect to the network – Practical Case

Ayoub Alkhalifah1 and I.O Habiballah

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1College of Electrical Engineering, KFUPM, Dahran, Saudi Arabia

Email: [email protected] 2College of Electrical Engineering, KFUPM, Dahran, Saudi Arabia

Email: [email protected]

Published: 30 November 2020

Copyright © Alkhalifah et al.

Abstract

This paper shows the effect of harmonics in power quality for the electrical network. Also, it will represent

the problem that can appear in the network because of high harmonics. Moreover, this paper will discuss one

case study and provide the proper solution based on given information from the end user.

Keywords: harmonics, THDV, THDI, AHF.

I. INTRODUCTION

In recent years, power quality become one of the main important topics in power system field because the

poor power quality will lead to lose money from the electricity supplier as well as end user. Power quality is a

major concern for transmission and distribution utilities, industries, and transport and infrastructure sectors.

Poor power quality affects grid reliability, productivity, leads to higher operating costs and penalties for non-

compliance with grid codes.

Poor power quality means any event related to the electrical network that makes end user lose money, there

are three main parameters that cause poor power quality which it will lead to energy losses and high running

costs: harmonics, reactive power, and load imbalance. A poor power factor can be a result of either

significant phase difference between voltage and current at the load terminals, or it can be due to a high

harmonic content. Poor load current phase angle is generally the result of an inductive load such as induction

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motors, power transformer, welder, etc. [1]. In this paper the focus will be on harmonics. Harmonics appear

in voltage waveform because of electronic devices that draw current in nonlinear way. Moreover, harmonics

can increase the current in power system which results higher losses (I2R) and increase the heat in neutral

conductor and distribution transformer as well. Nonlinear loads change the nature of sinusoidal wave form of

AC power current and this will lead to AC voltage drop consequently [2-4].

There are two definition for total harmonic distortion (THD), the harmonic existing in the network compared

with fundamental. The other definition, the harmonic content in network compared with waveform’s rms

value [5].

There are a lot of products, systems and services that improve power quality including capacitors and filters,

power electronics-based compensators and software solutions, across the power value chain for low, medium

and high-voltage applications, helping to shape a stronger, smarter and greener grid.

In this paper ABB software called “PQF sizing application“ will be used to provide a solution that will damp

the harmonics in the system network using active harmonics filter (AHF). Using ABB software to get a

solution comply with IEEE 519 standard by damping the harmonics in the system network up to the accepted

value based on IEEE 519 standard [1] as shown in table I and table II.

Table I: VOLTAGE DISTORTION LIMIT BASED ON IEEE 519

Table II: CURRENT DISTORTION LIMIT BASED ON IEEE 519

II. CAUSES OF HARMONIC DISTORTION

Linear load like electrical heater and lighting bulbs will not cause harmonics while nonlinear load like Arc

and induction furnaces, welding machines, LED light, and telecom system will cause harmonics in the

system.

In general, waveform distortion is due to the presence of nonlinear or time variable impedances or because of

bridge rectifiers, whose semiconductor devices carry the current only for a fraction of the complete period,

thus originating discontinuous curves with the consequent introduction of several harmonics.


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III. PROBLEMS CAUSE BY HARMONIC DISTORTION

Harmonic presence in facility can cause a serios problems like:

Unstable operating of generators.

Voltage flicker: which is the rapid change of voltage with high magnitude causing lighting level variations

which are noticeable or annoying to human beings, the effect is called flicker.

Devices overheating.

To illustrate the effect of harmonic in the network, below figures shown how the current wave form will be

distorted because of harmonics.

Fig 1: Fundamental frequency (without harmonics)

Fig 2: Fundamental frequency + fifth harmonic

Fig 3: Fundamental frequency + fifth harmonic + seventh harmonic

Fig 4: Fundamental frequency + fifth harmonic + seventh harmonic + thirteenth harmonic


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Fig 5: Fundamental frequency + fifth harmonic + seventh harmonic + thirteenth harmonic +

twintyfifth harmonic

Previous figures can show that adding more and more harmonics will end up with a step waveform instead of

sinusoidal waveform.

IV. Harmonics Effect On Power Factor

The power factor (PF) as a term may cause some confusion because there are three different type of power

factor: true power factor, displacement power factor, and distortion power factor. The true power factor takes

in the account [2]:

1. Distortion power factor depend on Total Harmonic Distortion Current THDI.

2. Displacement power factor is known as cosϕ, which is cosine the angle between voltage and current.

V. CASE STUDY

Case study will be analyze using ABB software called “PQF sizing application “to provide a solution that

will damp the harmonics in the system network using active harmonics filter (AHF). In this case study the

aim to reduce harmonic distortion contribution of the loads at LV busbar = 5% (THDI loads = 5%):

Fig 6: Customer Installation & Detailed Load Description


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Fig 7: Transformer, cable, and AC drives characteristics

Fig 8: Waveform for current and voltage with and without AHF

Fig 9: Representation THDI and THDV with and without AHF


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Fig 10: Representation THDI and THDV tables

Based on software the best solution to damp the harmonics up to accepted value (less than 5%) by using

active harmonic filter called” PQFS-M10 S10”.

The main technical specification for this product shown in table III.


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TABLE III: THECHNICAL SPECIFICATION FOR AHF (PQFS)

Description Value

Altitude Up to 1000m above sea leve

Minimum temperature -10°C

Maximum temperature +40°C

Degree of protection IP30

Dimensions per enclosure W x D x H: 588 x 310 x 705 mm

CT requirements 3 CTs are required (Class 1.0)

Network voltage ratings 380 V to 415 V between phases

Network frequency 50 Hz or 60 Hz

Current ratings Unit type 7: 100 A

Neutral current ratings 270A

Harmonics that can be filtered

15 harmonics individually selectable in the range

2nd · 50th

harmonic order if the neutral is connected

Degree of filtering Programmable per harmonic in absolute terms

Filtering efficiency Better than 97% of filter rating typically

Response time 40 ms typically (10% - 90% filtering)

VI: CONCLOSION

Finally, case study shows how the harmonic can cause a distortion in both current and voltage waveform.

Also, there are high amount of current losses that cause a poor power quality, high losses, and generate

unnecessary heat that can be avoided by improving the power quality and reduce the harmonic.

In addition, reducing the harmonic will reflect to the power factor and it will improve the power factor in

process with reducing the harmonics.

However, there are no one standard solution can solve all power quality issues. The measurement shall be

taken, and the analysis should be done properly to select the best solution for poor power quality issue.

Acknowledgment

I am grateful for all support from Dr. I.O Habiballah and Electrical Engineering Department at KFUPM for

giving me the resources needed to complete this paper.

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Harmonics effect to the network Practical Case