CONTROLLED SWITCHING FOR CIRCUIT BREAKERS
WITH PRE-INSERTION RESISTORS
ENERGIZING SHUNT CAPACITOR BANKS
ZACH SMITH, LUKE COLLETTE, TAKASHI YONEZAWA
MITSUBISHI ELECTRIC POWER PRODUCTS, INC.
UNITED STATES
TOMOHITO MORI, HARUHIKO KOYAMA
MITSUBISHI ELECTRIC CORPORATION
JAPAN
CIGRE-IEC 2016 Colloquium
May 9-11, 2016 Montréal, Québec Canada
2nd International Colloquium on EHV and UHV (AC & DC)
Introduction
2
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Shunt capacitor switching often requires controlled
closing, especially at higher voltages
Closing resistors sometimes used for shunt capacitor
switching at 550kV and higher
This case study analyses different switching
strategies using EMTP-RV and verifies that result
with an in-service circuit breaker
CIGRE-IEC 2016 Colloquium
May 9-11, 2016 Montréal, Québec Canada
2nd International Colloquium on EHV and UHV (AC & DC)
Case study substation layout
3
CIGRE-IEC 2016 Colloquium
May 9-11, 2016 Montréal, Québec Canada
2nd International Colloquium on EHV and UHV (AC & DC)
Original strategy
4
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Switching target originally was to initiate current
near a voltage zero
Improvement over no mitigation strategy
Might be adequate, depending on capacitor bank,
breaker design, CLR, maintenance cycle
CIGRE-IEC 2016 Colloquium
May 9-11, 2016 Montréal, Québec Canada
2nd International Colloquium on EHV and UHV (AC & DC)
Simulation of a close operation without controlled
switching and closing resistors
5
Peak inrush current
through breaker =
5.1 kA.
CIGRE-IEC 2016 Colloquium
May 9-11, 2016 Montréal, Québec Canada
2nd International Colloquium on EHV and UHV (AC & DC)
Simulation of a close operation with only
controlled switching
6
Peak inrush current
through breaker =
1.7 kA.
CIGRE-IEC 2016 Colloquium
May 9-11, 2016 Montréal, Québec Canada
2nd International Colloquium on EHV and UHV (AC & DC)
Simulation of a close operation with the original
controlled switching target
7
Electrical make of
main contacts.
Peak inrush current
through breaker =
2.0 kA.
Electrical make of
resistor contacts.
CIGRE-IEC 2016 Colloquium
May 9-11, 2016 Montréal, Québec Canada
2nd International Colloquium on EHV and UHV (AC & DC)
Illustration of original controlled switching
strategy
8
RDDS for resistor contacts
considering +/-1.0 ms mechanical
scatter and +/-10% deviation
Pre-insertion
resistor is inserted
Voltage across
main contacts
(absolute value)
RDDS for main contacts
considering +/-1.0 ms mechanical
scatter and +/-10% deviation
Pre-insertion resistor
is bypassed
Target 14o after
voltage zero
(resistor contacts).
Line-to-ground
bus voltage
Fixed time between
resistor and main contact
mechanical making
Existing Controlled Switching Strategy:
Target 14o after voltage zero (resistor contacts).
CIGRE-IEC 2016 Colloquium
May 9-11, 2016 Montréal, Québec Canada
2nd International Colloquium on EHV and UHV (AC & DC)
Original switching strategy was flawed
9
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Voltage on open arcing contacts is actually the
voltage across the resistor, not system voltage
Peak voltage is roughly 200kV due to 400Ω closing
resistor
Arcing contacts are electrically making at the peak
voltage!
What if we target arcing contact voltage zero
rather than resistor contact voltage zero?
CIGRE-IEC 2016 Colloquium
May 9-11, 2016 Montréal, Québec Canada
2nd International Colloquium on EHV and UHV (AC & DC)
Illustration of proposed controlled switching
strategy
10
RDDS for main contacts
considering +/-1.0 ms mechanical
scatter and +/-10% deviation
RDDS for resistor contacts
considering +/-1.0 ms mechanical
scatter and +/-10% deviation
RDDS for
main contacts
RDDS for resistor
contacts
Pre-insertion
resistor is inserted
Target 56o after
voltage zero
(resistor contacts).
Voltage across
main contacts
(absolute value)
Pre-insertion resistor
is bypassed
Line-to-ground
bus voltage
Fixed time between
resistor and main contact
mechanical making
Proposed Controlled Switching Strategy:
Target 56o after voltage zero (resistor contacts).
CIGRE-IEC 2016 Colloquium
May 9-11, 2016 Montréal, Québec Canada
2nd International Colloquium on EHV and UHV (AC & DC)
Simulation of the proposed controlled switching
strategy optimizing arcing contact inrush
11
Electrical make of
main contacts.
Electrical make of
resistor contacts.
Peak inrush current
through breaker =
0.8 kA.
CIGRE-IEC 2016 Colloquium
May 9-11, 2016 Montréal, Québec Canada
2nd International Colloquium on EHV and UHV (AC & DC)
Real world measurements
12
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Simulations show significant improvement with the
new switching target
Does real data match simulations?
Simulation:
 2.0
kA original inrush peak
 0.8 kA new inrush peak
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In-service measurement (average over 15 closes):
 1.9
kA original inrush peak
 0.7 kA new inrush peak
CIGRE-IEC 2016 Colloquium
May 9-11, 2016 Montréal, Québec Canada
2nd International Colloquium on EHV and UHV (AC & DC)
Measured closing operation with original
controlled switching target
13
Electrical make of
main contacts.
Peak inrush current
through breaker =
1.9 kA.
Electrical make of
resistor contacts.
CIGRE-IEC 2016 Colloquium
May 9-11, 2016 Montréal, Québec Canada
2nd International Colloquium on EHV and UHV (AC & DC)
Measured close operation with new controlled
switching target
14
Electrical make of
main contacts.
Electrical make of
resistor contacts.
Peak inrush current
through breaker =
0.7 kA.
CIGRE-IEC 2016 Colloquium
May 9-11, 2016 Montréal, Québec Canada
2nd International Colloquium on EHV and UHV (AC & DC)
Measured inrush current magnitude and prestrike duration
15
Date
PEAK INRUSH CURRENT (A)
Phase A
Phase B
PRE-STRIKE DURATION (ms)
Phase C
Phase A
Phase B
Phase C
Original Target Points
2-Feb-15
1809
1925
2042
2.1
2.1
2.1
5-Feb-15
2161
1858
1987
2.2
2.1
2.1
9-Feb-15
1907
1889
1894
2.2
2.2
2.1
10-Feb-15
1853
1842
1842
2.2
2.1
2.1
12-Feb-15
1962
2026
1819
2.1
2.2
2.2
Average =
1921
2.1
New Target Points
11-Jan-16
792
647
652
0.5
0.4
0.4
11-Jan-16
846
644
745
0.6
0.3
0.6
13-Jan-16
727
631
603
0.6
0.3
0.4
14-Jan-16
914
678
683
0.7
0.5
0.5
14-Jan-16
918
818
826
0.7
0.4
0.7
Average =
742
0.5
CIGRE-IEC 2016 Colloquium
May 9-11, 2016 Montréal, Québec Canada
2nd International Colloquium on EHV and UHV (AC & DC)
Conclusions
16
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Simulations match measurements
Inrush current peak: 1921 A  742 A
Pre-strike duration: 2.1 ms  0.5 ms
96% reduction in pre-strike arc energy
(using i2t approximation)
When multiple mitigation strategies are combined,
their interactions need to be considered to achieve
optimal results
CIGRE-IEC 2016 Colloquium
May 9-11, 2016 Montréal, Québec Canada
2nd International Colloquium on EHV and UHV (AC & DC)