Provincial Electricity Authority, Thailand 1 Harmonic Assessment of PEA North1, Chiangmai’s...

Provincial Electricity Authority, Thailand 1

Harmonic Assessment of PEA Harmonic Assessment of PEA North1, North1,

Chiangmai’s Customers in North Chiangmai’s Customers in North Industrial EstateIndustrial Estate

Chotepong Pongsriwat. M.Eng(EE) Chief of Power Quality SectionPEA (Chiang Mai, THAILAND)

19 - 21 September 2011, Chiang Mai, Thailand

PQSynergy TM 2011

• Distribution System: 22, 33 kV 289,328 cct-km

• Transmission System: 115 kV 8,701 cct-km

• 99.98% of electrified villages

• 14.60 millions of customer

• 14,089.58 MW of peak load

• 89,602.24 millions of KWhr of sales electricity

Provincial Electricity AuthorityPEA North Area 1,

ChiangMai, Thailand

Provincial Electricity Authority, Thailand 219 - 21 September 2011, Chiang Mai, Thailand

Problems created by harmonics

• Capacitor Problems

Due to its lower impedance, capacitors are even more susceptible to higher order harmonics. If not protected from harmonic stress, a capacitor may fail pretty soon.

19 - 21 September 2011, Chiang Mai, ThailandProvincial Electricity Authority, Thailand 3


When capacitor banks are installed for power factor improvement, the power system will exhibit one or more nature

frequencies due to a RLC network system formed by the capacitor bank and the remaining power distribution system.

-If one of the harmonic currents produced by the non-linear load is close to one of the nature frequencies, resonance conditions

will occur .

Parallel Resonance

jhXs

-jXc/hIh

Rs

Zh

Ihs Ihc

)(

))((

h

XhXjR

h

jXjhXR

Zc

ss

css

h

Simplified NetworkSimplified Network

Provincial Electricity Authority, Thailand

6 PulseConverter

Low VoltageCapacitor

2-WindingTransformer

AC VoltageSource

22 kV Bus

400 V Bus

HarmonicSource

PCC

Typical industrial circuit topologyTypical industrial circuit topology

We used to have voltage sources. Harmonic generators are often current Sources

Parallel Resonance (cont’)

jhXs

-jXc/hIh

Rs

Zh

Ihs Ihc

h

XhX c

s

)(

)(

)/(h

XhXjR

IjhXR

hjX

VI

css

hss

c

hhc

)(

)/(

h

XhXjR

IhjX

jhXR

VI

css

hc

ss

hhs

At resonance point :

hs

shc I

R

jhXI

1

hs

chs I

R

hjXI

/

)(h

XhXjR

jhXR

I

IM

css

ss

h

hcc

)(

/

h

XhXjR

hjX

I

IM

css

c

h

hss

Current Amplification


Easy evaluation of resonance

• * If the harmonic spectrum exhibits abnormal magnitudes, it is abad sign of harmonic resonance.

• * Typically caused by interaction with Power Factor Correction capacitors.


THDH02

H03H04

H05H06

H07H08

H09H10

H11H12

H13H14

H15

0

5

10

15

20

%

B IHarm (max)

Created with DranView 6.6.3

H5 H7

14.2%13%

LCf

2

1

1000.0802.00604.00406.00208.0010.000 [Hz]

4.0161

3.1749

2.3338

1.4926

0.651

-0.1898

400 V Bus: Network Impedance, Magnitude in Ohm

646.100 Hz 3.809 Ohm

DIg

SIL

EN

T

Resonance Frequency :

At this frequency where the inductive and capacitive reactances are equal, harmonic resonance occurs and the total effective impedance can be very high (parallel resonance) or very low (series resonance) depends on the system configuration.


Resonance Point

1000.0802.00604.00406.00208.0010.000 [Hz]

4.0161

3.1749

2.3338

1.4926

0.651

-0.1898


371.800 Hz 1.272 Ohm

DIg

SIL

EN

T

Case 1:

1000.0802.00604.00406.00208.0010.000 [Hz]

4.0161

3.1749

2.3338

1.4926

0.651

-0.1898


457.200 Hz 1.916 Ohm

DIg

SIL

EN

T

Case 2:

1000.0802.00604.00406.00208.0010.000 [Hz]

4.0161

3.1749

2.3338

1.4926

0.651

-0.1898


646.100 Hz 3.809 Ohm

DIg

SIL

EN

T

Case 3:

Case Capacitor Size (% of Transformer

Size)

1 30%

2 20%

3 10%


From Simulation

• In the past of Thailand, most medium/low voltage transformer in distribution system have delta/wye ground winding configuration installed with low voltage fixed capacitor which has

defined the reactive power rating (kVAR) equal to 30% of transformer size (kVA) on secondary side of the transformer .

• From this action, harmonic resonance from this capacitor can possibly occur.


Case Capacitor Size (% of Transformer Size)

1 30%

2 20%

3 10%


0.01

0.1

1

10

1 5 7 11 13 17 19 23 25

Harmonic Order (h)

Am

plif

icat

ion

(T

imes

)

Mc

Ms

Case 1: Current Amplification

0.1

1

10

1 5 7 11 13 17 19 23 25

Harmonic order (h)

Am

plif

icat

ion

(T

imes

)

Mc

Ms

Case 2:


0.1

1

10

100

1 5 7 11 13 17 19 23 25

Harmonic order (h)

Am

plif

icat

ion

(T

imes

)

Mc

Ms

Case 3:


From Simulation

Changing for 30% rule.


• For a low voltage distribution system with capacitor installed, system response evaluation is useful method in order to get an approximation of the resonance frequency for the system.

• During the resonance condition, some of the capacitor indices may over the limitation if the resonance frequency has the same value or very close to some harmonic order of harmonic current source.

• Noticeably, capacitor installation at 30% of distribution transformer size may lead to have higher rms current in capacitor and exceed the maximum allowable limit recommended by IEEE Std 1036-1992.

Capacitor Limitation

IEEE Std 1036-1992 indicates that the capacitor can be applied continuously within the following limitations, including harmonic components:

a) 180% of rated rms current b) 120% of rated peak voltage c) 110% of rated rms voltage d) 135% of rated reactive power


Harmonic StandardPurpose: Purpose: Ensure that the

networkdistortion does not

exceedpermissible levels thatguarantee proper

operation ofconnected equipment.


IEEE Std 519-1992

Typical levels & tendencies:-THDV <5% and limit for each harmonic component-Derive current limits to obtain voltage limits-Take into account high order harmonics

Customer Story• Customer specializes in desiging, manufacturing and

servicing high quality galleys, galley & cargo equipment

-Magnetic contactor of switching capacitor used to explodeand they would like to check the quality of power system.

-They would like to eliminate harmonic, if it exists.

After checking, Major problems are

-Most loads are Electronic Ballast,

ASDs(Adjustable Speed Drives), including with anodizing & electropolishing process which run frequently during production process.

-The harmonics are higher than standard

-Capacitor Switching cause high current rate and current magnification


Single line diagram of system


Provincial Electricity Authority, Thailand 15Provincial Electricity Authority, Thailand 15

Ic

Is Measuring Point

Measurement Location


IcIs

IsIc

Harmonic Resonance Point Assessment


Resonance frequency corresponding to the parameters of the system.

C Bank Step#

f(Hz)Resonance

OrderXL

Resonance

XC Resonance

System Impedance at Fundamantal Frequency

(Ohm)

System Impedance at Resonance Frequency

(Ohm)

11000.20

200.0

01599.6792

015996.792

0008268257 1268.

27072.5

141.4

01131

144

011311.44

0008289018. 634.

35774

7

115

5

00923.5752

009235.752

000830988. 423.

45001.0

100.0

00799.8396

007998.396

0008330845. 317.

54473

0895. 00715.

3983

007153.983

0008351911. 254.

64083.3

81700653.0663

006530.663

0008373081. 211.

73780.4

75600604.6219

006046.219

0008394355. 181.

83536

2707. 00565.

572

005655.72

0008415734. 159.

Frequency Scan


From 400V System

Resonance at 7th HarmonicCapacitors & reactors(transformers) will always create resonance for some frequencies.Resonance is impossible to avoidResonance is not a problem if not excited

System frequency response as capacitor sizeis varied in relation to transformer

Harmonic Assessment with Standard


Result from MDB

Current

Waveform


Voltage

Waveform

Spectrum

Result from Capacitor

Current

Waveform


Voltage

Waveform

Spectrum

Magnified CurrentIs


Ic

VcVs

Result : VTHD (Capacitor)


THD Fund Normalized

Result : VTHD (System/Transformer)


THD Fund Normalized

Result : ITHD (Capacitor)


THD Fund Normalized

Result : ITHD (System/Transformer)


THD Fund Normalized

Capacitor Switching• Switching of Capacitor

(Switch off for 1 step)


Ic

Is

Capacitor Switching


• Switching of Capacitor(Switch in for 1 step: step 4 to 5)

Capacitor Switching

• Vpeak of 230V. System = 325.26 V.


• Vpeak = 455.2 V.equal to 1.4 Vpk

(exceed to the limit of rated Vpk, IEEE1026-1992 :1.2 Vpk)



• All of 8 Capacitors Steps are switched into the system.

Harmonic Assessment with Standard


Suggestions


1. Replace the original magnetic contactor to new type Magnetic contactor with insertion of damping resistor (With Unlimited Peak Current)

2. Detuned Filter Bank 8x50 kVar,400V. 50Hz. 3 phase.

3. Reconsideration, for individual harmonic loads , when new harmonic loads are installed to the system because customer has oftenly add the load without concerning to harmonic.

Thank you very much for your attentions.Thank you very much for your attentions.


Chotepong PongsriwatPQ Chief

SuwipaKittithanapisanPQ Assistant Chief

NatSongkramPQ Engineer

NarusornJan-ngernPQ Engineer

SatidSriwongTechnician

ChinarukKumpromTechnician

Power Quality Team : Chiangmai THAILANDPower Quality Team : Chiangmai THAILANDPower Quality Team : Chiangmai THAILANDPower Quality Team : Chiangmai THAILAND

Date post:	26-Dec-2015
Category:	Documents
Upload:	hector-jennings
View:	238 times
Download:	0 times

Provincial Electricity Authority, Thailand 1 Harmonic Assessment of PEA North1, Chiangmai’s...

Documents