Power Quality - 5leon.fe.uni-lj.si/media/uploads/files/KEE okt13 IPapic 5.pdf · 1 Course Power Quality - 5 Ljubljana, Slovenia 2013/14 Prof. dr. Igor Papi č [email protected]

1

Course

Power Quality - 5

Ljubljana, Slovenia2013/14

Prof. dr. Igor Papič[email protected]

Interruptions

Content

1st day 2nd day 3rd day 4th day 5th day

Session 1

Introduction to Power Quality • what is PQ • economic value • responsibilities

Harmonics – definitions • calculations • non-linear loads • harmonic

sequences

Harmonics - design of power factor correction devices • resonance points • filter design

Flicker case study • calculation of

flicker spreading in radial network

• variation of network parameters

Interruptions • definitions • reliability indices • improving

reliability

Session 2

Basic terms and definitions • voltage quality • continuity of

supply • commercial

quality

Propagation of harmonics • sources • consequences • cancellation

Flicker - basic terms • voltage variation • flicker frequency • sources • flickermeter

Voltage sags – definitions • characteristics • types • causes

Consequences of inadequate power quality • voltage quality • interruptions • costs

Session 3

PQ standards • EN 50 160 • other standards • limit values

Harmonics - resonances in network • parallel

resonance • series resonance

Flicker spreading • radial network • mashed network • simulation • examples

Propagation of voltage sags • transformer

connections • equipment

sensitivity • mitigation

Modern compensation devices • active and hybrid

compensators • series and shunt

compensators

Session 4

PQ monitoring • measurements • PQ analyzers • data analyses

Harmonics case study • calculation of

frequency impedance characteristics

Flicker mitigation • system solutions

– network enforcement

• compensation

Other voltage variations • unbalance • voltage

transients • overvoltages

Conclusions • PQ improvement

and costs • definition of

optimal solutions

Power Quality, Ljubljana, 2013/14 3

2

Terms and definitions

• EN 50160 (IEC)– long interruption: longer than 3 minutes– short interruption: up to 3 minutes

• IEEE Std.1159-1995– momentary interruption: between 0.5 cycles and 3

seconds– sustained interruption: longer than 3 seconds (overlap

with temporary interruptions)– temporary interruption: between 3 seconds an 1 minute



• IEEE Std.1250-1995– instantaneous interruption: between 0.5 and 30 cycles– momentary interruption: between 30 cycles and 2

seconds– temporary interruption: between 2 seconds and 2

minutes– sustained interruption: longer than 2 minutes

• IEEE Std.859-1987– transient outages are restored automatically– temporary outages are restored by manual switching.– permanent outages are restored through repair or

replacement



• confusion about terminology• short interruption – the supply is restored

automatically• long interruption – the supply is restored manually• EN 50160 term

– supply interruption – a condition in which the voltage at the supply terminals is lower than 1 % of the declared voltage


3


• reliability indices– Energy Not Supplied – ENS

• Dsi – average load,• Ti – interruption duration in node i

– System Average Interruption Frequency Index –SAIFI

∑=i

isi ENS TD

Served CustomersofNumbr TotalonsInterruptiCustomer ofNumbr TotalSAIFI=



• reliability indices– Energy Not Supplied – ENS (European countries)



• reliability indices– System Average Interruption Frequency Index –

SAIFI (European countries)


4


• reliability indices– System Average Interruption Duration Index –

SAIDI

– Momentary Average Interruption Frequency Index – MAIFI

Served Customers ofNumber TotalDurationon InterruptiCustumer

SAIDI ∑=

Served Customers ofNumber TotalonsInterruptiMomentary Customer ofNumber TotalMAIFI=



• reliability indices– System Average Interruption Duration Index –

SAIDI (European countries)



• reliability indices– Momentary Average Interruption Frequency

Index – MAIFI (European countries)


5

EN 50160 definitions

• supply voltage disturbances– supply interruption

• prearranged, when consumers are informed in advance, to allow the execution of scheduled works on the distribution system, the effect can be minimized

• accidental, caused by permanent or transient faults, mostly related to external events, equipment failures or interference



• supply interruption– prearranged

(planned) and accidental (unplanned) interruptions per customer per year



• supply interruption– prearranged

(planned) and accidental (unplanned) interruption minutes lost per customer per year


6


• supply voltage disturbances– accidental interruption

• unpredictable, largely random events• a short interruption (up to 3 minutes) caused by a

permanent fault• a long interruption (longer than 3 minutes) caused by

a transient fault



• voltage supply-characteristics– short interruptions of the supply voltage in LV

and MV networks (up to 3 minutes)• annual occurrence: from up to a few tens to up to

several hundreds• approximately 70 % of short interruptions may be less

than one second• in some documents short interruptions are considered

as having durations not exceeding 1 minute• sometimes control schemes are applied which need

operating times of up to three minutes in order to avoid long voltage interruption



• voltage supply-characteristics– long interruptions of the supply voltage in LV

and MV networks (longer than 3 minute)• indicative values: less than 10 or up to 50 depending

on the area• differences in system configurations and structures in

various countries• indicative values are not given for prearranged

interruptions


7



Long interruptions

• terminology– failure

• a device or system that does not operate as intended– outage

• removal of a primary component from the system• forced outage (failure)• scheduled outage

– interruption• a customer is no longer supplied with electricity• due to outages


Long interruptions

• causes of long interruptions– a fault occurs in the power system which leads

to an intervention by the power system protection

– a protection relay intervenes incorrectly, thus causing a component outage

– operator actions cause a component outage which can also lead to a long interruptions


8

Long interruptions

• power system reliability– number and duration of long interruption are

stochastically predicted– availability – the probability of being energized– unavailability – the probability of not being

energized


Long interruptions

• power system reliability– the 9s of reliability in power delivery

Numberof 9s

Reliability[%]

Expecteddisruptions

per year

Acceptable for

3 99.9 9 h homes4 99.99 59 min factories5 99.999 5 min hospitals, airports6 99.9999 32 s banks7 99.99999 30 ms on-line markets


Long interruptions

• power system reliability– failure rates for overhead lines


9

Long interruptions

• power system reliability– failure rates for underground cables


Long interruptions

• definition of areas


Long interruptions

• excluding exceptional events– definition of

exceptional events


10

Long interruptions

• reliability indices – SAIFI– geographical classification


Long interruptions

• reliability indices – SAIDI– geographical classification


Long interruptions

• reliability indices – SAIFI– voltage level classification


11

Long interruptions

• reliability indices – SAIDI– voltage level classification


Short interruptions

• automatic restoration• reclosing of a circuit

breaker• switching to a healthy

supply• automatic transfer

switches in industrial networks


Short interruptions

• reliability indices – MAIFI– European countries


12

Improving reliability

• methods– reducing the number of short-circuit faults– reducing the fault clearing time– changing the system such that the short-circuit

faults results in less severe events at the equipment terminals or at the customer interface

– connecting mitigation equipment between the sensitive equipment and the supply


Consequences of inadequate power quality

Content


Session 1



sequences






reliability

Session 2



quality





Session 3










compensators

Session 4






• compensation





optimal solutions


13

PQ costs examples

• sensitivity of different industries to voltage dips expressed in estimated dips cost per industry


PQ costs examples

• voltage dips cost per event


PQ costs examples

• financial losses caused by voltage dips


14

LPQI - PQ survey

• Leonardo Power Quality Initiative – LPQI – PQ survey

• the survey interviews and web based submission were conducted over a 2-year period in 8 European countries

• 62 complete and 6 partial interviews were carried out • these sectors represent some 38% of the EU-27 total of

turnover• the main purpose of this project was to estimate costs of

wastage generated by inadequate power quality for those sectors within the EU-27 for which electrical power is critical

• PQ costs are reported in the categories of interruptions and voltage quality


LPQI - PQ survey

• Leonardo Power Quality Initiative – LPQI – PQ survey

• all these cost were specified on an annual basis, either reported as such or pro-rated where frequency was less than once pa

• also hypothetical costs that would be the potential losses and risk avoided by power systems that had been immunized against the PQ disturbances were under review

• the subsequent regression analysis was performed to estimate PQ cost across those sectors with “annual turnover” as a key model indicator


LPQI - PQ survey

• PQ survey– number of interviews by sectors and countries


15

LPQI - PQ survey

• PQ survey– PQ consequences

blame


LPQI - PQ survey

• PQ survey– PQ problem sources


LPQI - PQ survey

• PQ survey– PQ

consequences


16

LPQI - PQ survey

• PQ survey– equipment being affected


LPQI - PQ survey

• PQ survey– PQ cost indices (industry)


LPQI - PQ survey

• PQ survey– PQ event costs


17

LPQI - PQ survey

• PQ survey– PQ cost summary

by the type of PQ disturbance


LPQI - PQ survey

• PQ survey– PQ cost summary by the

type of costs– labor cost– Work in Progress – WIP

• labor and materials inevitably lost

• labor needed to make up lost production

• sales or services such as overtime pay, extra shifts

• …


LPQI - PQ survey

• PQ survey – type of costs– process slow down when the production process could not

reach its nominal efficiency covering equipment restarts, resets, repeating operations, time needed for additional adjustments to and maintenance of equipment including losses in value of products running out of specification and/or value of insufficient quality of products as a consequence of a particular PQ disturbance

– equipment costs including damage, shortened effective lifetime, premature component wear out, need for additional maintenance or repair and for the purchase or rental of backup equipment

– other costs like additional fines, penalties, personnel injury related costs, including additional compensation or increased insurance rates

– savings from unused materials, unpaid wages and mainly unconsumed energy


18

LPQI - PQ cost summary


LPQI - PQ survey

• Leonardo Power Quality Initiative – LPQI – PQ survey - conclusions

• industry wastes a huge amount of resource unnecessarily

• the nature of the main causes of poor power quality illustrates that better design and greater investment into these systems would eradicate most of these losses

• measurement and diagnostics are significantly low for industrial sectors for which electrical power is so important

• industry [and others] would appear to be in denial about the levels of waste incurred


Slovenian survey

• LPQI questionnaire• PQ survey

– number of interviews by sectors

Investigated organizations Nr. Food and kindred products 4 Pulp and paper 3 Printing and publishing 3 Plastic and rubber 2 Metallurgy 2 Automotive 2 Cement 1 Transport 1 White goods 1 Pharmaceuticals 1 Oil or petroleum refining 1 Textiles 1 Insurance, broker &services 1 Chemicals 1 Sum 24


19

Slovenian survey

• PQ survey– reported consequences of experienced PQ events


Slovenian survey

• PQ survey– annual costs related to category of organizations with

annual consumption of 1 to 5 GWh (8 organizations)


Slovenian survey

• PQ survey– annual costs related to category of organizations with

annual consumption of 5 to 25 GWh (6 organizations)


20

Slovenian survey

• PQ survey– annual costs related to category of organizations with annual

consumption of more than 25 GWh (10 organizations)


Italian survey

• PQ survey– number and structure of interviews


Italian survey

• PQ survey– interruption costs– direct costs -

economic damage due to a hypothetical interruption scenario


21

Italian survey

• PQ survey– interruption costs– the quantification two key variables

• willingness to pay (WTP), expressed as the price which the consumer would be willing to pay another company ready to take over with a reserve service in the event of supply interruptions on the part of the main supplier

• willingness to accept (WTA) expressed as the amount that would be considered satisfactory if the company supplying electricity should decide to discount payment of the supply each time an interruption occurs

– WTP and WTA act as tools by which to verify the consistency of gathered information

– from an economic point of view these two aspects express the same concept of valuation of damage due to the interruption


Italian survey

• PQ survey– normalization

• direct costs, WTA and WTP are normalized on Energy Not Supplied (ENS)

• ENS, in kWh, indicates the quantity of energy that would on average have been consumed if the supply had not been interrupted in a given scenario for a given duration


Italian survey

• PQ survey– WTA and WPT

normalized values


22

Costs of ENS – Slovenia

• costs of ENS in Slovenia for 2006– 83 interviews– determination of

ENS– cost of ENS in

Slovenia equals 4,28 €/kWh


Costs of ENS – Europe

• overview of costs of interruptions in Europe– the differences between countries and between customer

groups


Modern compensation devices

23

Content


Session 1



sequences






reliability

Session 2



quality





Session 3










compensators

Session 4






• compensation





optimal solutions


Modern Compensation Devices

• network reconfiguring devices– Solid State Current Limiter – SSCL – Solid State Breaker – SSB– Solid State Transfer Switch – SSTS

• thyristor controlled reactive elements– Thyristor Controlled Reactor – TCR– Thyristor Switched Capacitor – TSC – Static Var Compensator – SVC – Thyristor Controlled Series Compensator – TCSC


Modern Compensation Devices

• active compensators– Voltage Sourced Converter – VSC– Static Compensator – StatCom– parallel active filter (Distribution Static Compensator –

DStatCom)– Dynamic Voltage Restorer – DVR (series active filter)– hybrid active filter (different configurations)– Unified Power Quality Conditioner - UPQC


24

Network reconfiguring devices

• Solid State Current Limiter – SSCL– in series with a feeder– solid-state switches are opened when a fault is detected– current limiting inductor



• Solid State Breaker – SSB – similar topology as SSCL– limiting inductor is connected in series with an opposite-

poled thyristor pair (blocked after a few cycles of faulted current)



• Hybrid Breaker– combination of mechanical and solid-state breaker– conventional circuit breaker has lower conducting losses

(normal operating conditions)


25


• Solid State Transfer Switch – SSTS– transfer of power to the alternate feeder


Thyristor controlled reactive elements

• Thyristor Controlled Reactor – TCR



• Thyristor Controlled Reactor – TCR– 12-pulse

connection


26


• Thyristor Switched Capacitor – TSC

L1

L2

L3 T1 T3

T2

C1

C2

C3L1

L3

L2



• Static Var Compensator – SVC – TCR– TSC– tuned filters– fixed capacitors– different configurations



• Static Var Compensator – SVC– U-I characteristic– voltage dependent reactive current


27


• Thyristor Controlled Series Compensator – TCSC – series line compensation– parallel connection of fixed capacitor and TCR (variable

capacitance)

T

C

L

Iv IC

IL


Active compensators

• Voltage Sourced Converter – VSC – 6-pulse configuration– IGBTs or GTOs with anti-parallel diodes– gate turn-off capability

uDC

S1

S2

S3 S5

S4 S6

CL1L2L3


Active compensators

• Voltage Sourced Converter – VSC – one leg of a three-phase converter– Pulse Width Modulation - PWM


28

Active compensators

• Voltage Sourced Converter – VSC– 2 Voltage Sourced Converters in a 12-pulse connection


Active compensators

• Voltage Sourced Converter – VSC– three-level Voltage

Sourced Converter– harmonics cancellation

+udc'/2

-udc'/2

C/2

C/2

N L1

1 1'

1A 1A'

4 4'

4A 4A'


Active compensators

• Voltage Sourced Converter – VSC– four-wire Voltage Sourced Converter– LV applications


29

Active compensators

• Statc Compensator –StatCom– shunt connected VSC– voltage-independent

source of reactive current– reactive power– voltage control– flicker


Active compensators

• Statc Compensator – StatCom– comparison between

StatCom and SVC– simulation of voltage

sag compensation –motor starting

Primerjava SVC, STATCOM

t (s) 0.60 0.70 0.80 0.90 1.00 1.10 ...

-0.40 -0.30 -0.20 -0.10 0.00 0.10 0.20 0.30 0.40

Tok

(kA

)

I L1 20 kV STATCOM I L1 20 kV SVC

-2.0

-1.0

0.0

1.0

2.0

3.0

4.0

P (M

W),

Q (M

VA)

P STATCOM P SVC

0.0

2.0

4.0

6.0

8.0

10.0

P (M

W),

Q (

MVA

)

Q STATCOM Q SVC

0.900

0.950

1.000

1.050

1.100

Nap

etos

t (p

u)

U 20 kV rms STATCOM U 20 kV rms SVC

StatComSVC


Active compensators

• parallel active filter– the same configuration as

StatCom– Distribution Static

Compensator - DStatCom– different control

algorithms– compensation of load

current– current harmonics– current unbalances

Active filter

C

Network

ui

up

Lp

ivuv

ib

ip

Zb

Load

udc

Zom


30

Active compensators

• parallel active filter– simulation of compensation of an unbalanced and non-

linear load– case 1

Aktivni kompenzator

0.110 0.120 0.130 0.140 0.150 0.160 0.170 0.180 0.190 0.200 0.210 0.220 0.230 0.240 0.250 0.260 ...

-0.100

-0.050

0.000

0.050

0.100

I (k

A)

I 5 kV omrezje L1 I 5 kV breme L1

-0.100 -0.075 -0.050 -0.025 0.000 0.025 0.050 0.075 0.100

I (kA

)

I komp L1

-6.0

-4.0

-2.0

0.0

2.0

4.0

6.0

U (k

V)

U 5 kV


Active compensators

• parallel active filter– simulation of compensation of an unbalanced and non-

linear load– case 2

Aktivni kompenzator

0.130 0.140 0.150 0.160 0.170 0.180 0.190 0.200 0.210 ...

-0.100

-0.050

0.000

0.050

0.100

I (k

A)

I 5 kV breme L1 I 5 kV breme L2 I 5 kV breme L3

-0.100

-0.050

0.000

0.050

0.100

I (kA

)

I 5 kV omrezje L1 I 5 kV omrezje L2 I 5 kV omrezje L3

-0.080 -0.060 -0.040 -0.020 0.000 0.020 0.040 0.060 0.080

I (kA

)

I komp L1 I komp L2 I komp L3


Active compensators

• Dynamic Voltage Restorer – DVR – series active filter – voltage sags and harmonics compensation


31

Active compensators

• Dynamic Voltage Restorer – DVR – simulation of voltage sag compensation

Aktivni filter

0.00

0.20

0.40

0.60

0.80

1.00

1.20 U omrezje 20 kV rms

U (

pu)

U breme 20 kV rms

-25.0 -20.0 -15.0 -10.0 -5.0 0.0 5.0

10.0 15.0 20.0 25.0

U (

kV)

U omrezje 20 kV L1 U omrezje 20 kV L2 U omrezje 20 kV L3

-40 -30 -20 -10

0 10 20 30 40

U (

kV)

U breme 20 kV L1 U breme 20 kV L2 U breme 20 kV L3

networkload


Active compensators

• hybrid active filter 1– parallel connection

of an active and passive filter

– less expensive solution

– active filter is smaller


Active compensators

• hybrid active filter 2– series active filter and parallel passive filter


32

Active compensators

• hybrid active filter 2– series active filter and parallel passive filter– LV simulation case


Active compensators

• hybrid active filter 2– series active filter and parallel passive filter– simulation results

only passive filters with active filter Aktivni filter

-0.40 -0.30 -0.20 -0.10 0.00 0.10 0.20 0.30 0.40

U (k

V)

U 0,4 kV L1

-0.060

-0.040 -0.020

0.000 0.020

0.040 0.060

I (kA

)

I breme 0,4 kV L1

-0.100 -0.080 -0.060 -0.040 -0.020 0.000 0.020 0.040 0.060 0.080 0.100

I (kA

)

I omrezje 0,4 kV L1

Aktivni filter

-0.40 -0.30 -0.20 -0.10 0.00 0.10 0.20 0.30 0.40

U (k

V)

U 0,4 kV L1

-0.060

-0.040 -0.020

0.000 0.020

0.040 0.060

I (kA

)

I breme 0,4 kV L1

-0.100 -0.080 -0.060 -0.040 -0.020 0.000 0.020 0.040 0.060 0.080 0.100

I (kA

)

I omrezje 0,4 kV L1


Active compensators

• hybrid active filter 3– series connection of

active filter and passive compensator of reactive power

– active filter blocks harmonics (resonances)

– active filter is very small


33

Active compensators

• hybrid active filter 3– series connection of

active filter and passive compensator of reactive power

– simulation of reactive power compensation

– resonance with only passive compensator

Industrijsko omrežje

0.200 0.250 0.300 0.350 0.400 ...

0.00 To

k tra

nsfo

rmat

orja

TR

1

I3_L1

-40 -30 -20 -10

0 10 20 30 40

Nap

etos

t v C

TP 3

5 kV

U CTP 35 kV L1

-0.40 -0.30 -0.20 -0.10 0.00 0.10 0.20 0.30 0.40

Tok

kom

penz

ator

ja K

2

I K_Store L1


Active compensators

• Unified Power Quality Conditioner - UPQC– series and parallel VSC– common dc link


Active compensators

• active compensation (expensive!)– general application


34

Conclusions

Content


Session 1



sequences






reliability

Session 2



quality





Session 3










compensators

Session 4






• compensation





optimal solutions


Economic evaluation

• economic evaluation methodology – characterize the system power quality

performance– estimate the costs associated with the power

quality variations– characterize the solution alternatives in terms of

costs and effectiveness– perform the comparative economic analysis


35

Economic evaluation

• economic evaluation methodology


Economic evaluation

• system power quality performance– annual expected number of voltage sags– annual expected number of interruptions– estimation of other disturbances– PQ technical issues

• costs for power quality variations– costs associated with different disturbances– weighting factors representing the relative impact of

different disturbances– summation of weighted costs – equivalent interruptions– PQ techno-economical issues


Economic evaluation

• cost and effectiveness for solution alternatives1. equipment specification changes2. sub-panel level equipment protection3. site-wide protection4. grid solutions


36

Economic evaluation

• cost and effectiveness for solution alternatives


Economic evaluation

• cost and effectiveness for solution alternatives– LPQI PQ survey - PQ solutions


Economic evaluation

• cost and effectiveness for solution alternatives– costs of power

quality mitigation equipment


37

Economic evaluation

• cost and effectiveness for solution alternatives– costs of mitigation techniques - 1


Economic evaluation

• cost and effectiveness for solution alternatives– costs of mitigation techniques - 2


Economic evaluation

• cost and effectiveness for solution alternatives– UPS example - the table below compares the relative

cost per kW, relative to power requirement, for a distributed system with that for a centralized system


38

Economic evaluation

• comparative economic analysis– Net Present Value (NPV)

investment of lifetime ... years ofnumber ...

ratediscount ... investment initial ...

at time flowcash ... )1(

0

00

ntrC

tCF

Cr

CFNPV

t

n

tt

t∑=

−+

=


Economic evaluation

• comparative economic analysis– Net Present Value (NPV)– NPV is a measure of how much value is created or added

today by undertaking an investment– i.e. the difference between the investment’s market value

and its cost– for independent projects - an investment should be

accepted if the net present value is positive and rejected if it is negative

– for mutually exclusive projects - the project with the largest positive NPV should be selected


Economic evaluation

• comparative economic analysis– Internal Rate of Return (IRR)

investment of lifetime ... years ofnumber ...

investment initial ... at time flowcash ...

(IRR)discount of rate internal ... )1(

0

0

00

ntC

tCFR

CR

CF

t

n

tt

t∑=

−+

=


39

Economic evaluation

• comparative economic analysis– Internal Rate of Return (IRR)– the internal rate of return is the discount rate that makes

the NPV of a project equal to zero– set NPV equal to zero and solve for interest rate - the

interest rate that yields an NPV of zero is the IRR– an investment is acceptable if the IRR exceeds the

required rate of return - it should be rejected otherwise


Economic evaluation

• comparative economic analysis– Payback Time (PBT)

benefits annual from subtracted expences annual ...return annualnet on)installati (equipmet costs initial ... investmentnet

12return annualnet

investmentnet )months(

+

⋅=PBT


Economic evaluation

• comparative economic analysis– Payback Time (PBT)– the payback is the length of time it takes to recover the

initial investment– assume cash flows are received uniformly throughout the

year - calculate the number of years it will take for the future cash flows to match the initial cash outflow

– an investment is acceptable if its calculated payback period is less than some pre-specified number of years


40

Economic evaluation

• comparative economic analysis– example of an

analysis for sag and interruption mitigation

– cost of capital discount rate equals to 10 %

– assumed lifetime is 10 years


Economic evaluation

• comparative economic analysis– example of an analysis

for replacement of overhead lines with cables

– considered• maintenance• reliability• losses


Economic evaluation

• comparative economic analysis– example of an analysis for replacement of overhead lines

with cables


41

Economic evaluation


with cables– NPV


Economic evaluation


with cables– IRR

IRR

(%)


Conclusions

• importance of power quality knowledge– performance and interpretation of PQ

measurements– detailed analysis of disturbances

• analysis of disturbing loads• determination of emission levels• disturbance spreading in the network

– better negotiating position for concluding the power supply contracts


42

Conclusions

• importance of power quality knowledge– planning and purchasing new equipment and

connecting new customers • large power electronics devices – THD• large motor drives – voltage dips• large arc furnaces – flicker • connection of passive power factor correction devices

– resonance • specification of other compensation devices• …


Conclusions

• importance of power quality knowledge– solving conflicts between suppliers and

customers– evaluating costs due to poor PQ – determining economically optimal mitigation

techniques– …– …


Documents

Power Quality - 5leon.fe.uni-lj.si/media/uploads/files/KEE okt13 IPapic 5.pdf · 1 Course Power Quality - 5 Ljubljana, Slovenia 2013/14 Prof. dr. Igor Papi č [email protected]