evaluation of anti-islanding protection schemes
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EVALUATION OF ANTI-ISLANDINGPROTECTION SCHEMES
INDIAN CONTEXT
New Delhi / 21 April 2012
Renewable Energy World India
Kona Eswararao | Gamesa R&D Chennai
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EVALUATION OF ANTI - ISLANDING
SCHEMES
Distributed Generation
Islanding Anti-Islanding protection
Passive schemes and NDZ
PJD applied to weak grid
Simulation results
Conclusion
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Grid Connected RE SystemsChallenges and Issues
Islanding
Dynamic interaction between various generators
Conflict in voltage control for generators in
proximity
Power Quality
Weak Grid situations
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IslandingIntroduction
When loads are being fed power from DG even after the power supply issuspended from utility - Islanding Condition at PCC
Power
Converter
R L C
Grid
Utility breaker
DGDG jQP + gridgrid
jQP +
loadload jQP +
Local Load
PCC
loadDGgrid
loadDGgrid
QQQQ
PPPP
==
==
Wind Turbine
Generator
Formation of Islandwhen breaker is opened
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IslandingIssues
Danger to maintenance and restoration personnel
Destruction at both customer and utility side equipment
Power quality of DG becomes worsen - adversely affect the
loads
Automatic closing of utility breaker may create a condition of
asynchronous closure
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Anti-IslandingClassification
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Anti-IslandingPassive and Active Schemes
Passive techniques are based on measurement of instantaneous voltage,frequency and phase deviations at PCC
Simple and Easy to implement No introduction of noise or harmonic signal into network as like as Active
methods Power Quality not disturbed
The range of active power and reactive power change during islanding will
influence the detection time Passive techniques relay on certain distinct pattern or signatures at the DG
out put
Active techniques introduce deliberate changes or disturbances into the
connected circuit and then observe the response
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Anti-IslandingNDZ for CERC and C-WET requirements
Non Detection Zone (NDZ) is the range activepower and reactive power mismatch thatcauses non detection of Islanding
In this work NDZ is calculated for CERC andCWET based on voltage and frequencyvariation allowed
-27% to 14.34%-5.07% to 1.98%% change in Q
for Qf = 2.5
-17.6% to 9.35%-3.3% to 1.29 %% change in Qfor Qf = 1.63
-15.9 % to 21%-15.9 % to 21%% change in P
47.5 Hz49.5 Hzfmin
51.5 Hz50.2 Hzfmax
30 KV30 KVVmin
36 KV36 KVVmax
CWET at 33 KVCERC at 33 KVPARAMETER
-30 -20 -10 0 10 20 30-10
-8
-6
-4
-2
0
2
4
6
8
10
% Chnage in Active power
%C
hangein
Reactivepower
NDZ for CERC Tolerance at 33 KV
At Qf = 1.63
At Qf = 2.5
UVOV
OF
UF
-30 -20 -10 0 10 20 30-30
-20
-10
0
10
20
30
% Change in Acitve power
%C
ha
ngeinReactivepowr
NDZ for CWET Tolerance at 33 KV Grid
At Qf = 1.63
At Qf = 2.5
UF
OF
OV UV
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PJD ApplicationStiff Grid condition
MATLAB simulation model is developed toanalyse PJD method applied for stiff gridsituation
Islanding detection time for stiff grid is23.5 msec
0 0.05 0.1 0.15 0.2-2
-1.5
-1
-0.5
0
0.5
1
1.5
2Islanding detection at stiff grid
Phasejumpin
radians
Time in sec
Stiff grid
0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.20
0.2
0.4
0.6
0.8
1
Islanding detection at stiff grid
DGCBsta
tus
Time in sec
X: 0.07355
Y: 1
Stiff Grid
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PJD ApplicationWeak Grid condition Voltage fluctuations
Same PJD method is applied to various weak grid situationsDetection time with high voltage fluctuations is 16 msec - Very QUICK
0.06 0.065 0.07 0.075 0.08
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
X: 0.06605
Y: 1
Islanding detection during high grid voltage
DGCBstatus
Time in sec
X: 0.07355
Y: 1
Stiff grid
Vhigh50
Vhigh20
Vhigh10
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PJD ApplicationWeak Grid condition Frequency fluctuations
Detection time same as stiff-grid, effect is negligible Because offrequency variation doesnt contribute to phase angale detection
0.07 0.071 0.072 0.073 0.074 0.075 0.076 0.077
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
X: 0.07355
Y: 1
Islanding detection during high grid frequency
DGCBstatus
Time in sec
Stiff Grid
fhigh10
fhigh20
fhigh50
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PJD ApplicationWeak Grid condition Higher THD presence
Same Islanding detection as compared to stiff grid due to grid alreadyhas harmonics / disturbance
Detection time with high harmonics in the system is just 14 msecFaster detection
0.06 0.062 0.064 0.066 0.068 0.07 0.072 0.074 0.076
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
X: 0.07355
Y: 1
Islanding detection during 5th harmonics in grid
DGCBstatus
Time in sec
X: 0.06425
Y: 1
ideal
THD 10%
THD 20%
THD 50%
0.06 0.065 0.07 0.075 0.08 0.0850
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
X: 0.0622
Y: 1
Islanding detection during 11th harmonics in grid
DGCBstatus
Time in sec
X: 0.07355
Y: 1
Stiff Grid
THD 10%
THD 20%
THD 50%
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Conclusions
Passive methods are simple, cost effective but higher values of NDZ
PJD gives early detection of Islanding when grid is weak
Introduction to DG Islanding phenomenon
Need for Islanding protection stringent Grid codes
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Thank you
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