minimizing capacitor bank
DESCRIPTION
Minimizing Capacitor BankTRANSCRIPT
Copyright © FPL and SEL 2013
Minimizing Capacitor Bank Outage
Time Through Fault Location
Joseph Schaefer Florida Power & Light Company
Satish Samineni, Casper Labuschagne,
Steven Chase, and Dereje Jada Hawaz Schweitzer Engineering Laboratories, Inc.
Capacitor Bank Configuration
Units in
Series
Units in ParallelCapacitor
Element
Problem Statement
• Unit or element failures result in
overvoltages
• Unbalance protection usually trips bank if
overvoltages are too high
• Locating faulty unit is time-consuming
process, resulting in long outage time
Steps to Put Bank Back in Service
• Take bank out of service
• Isolate and ground bank
• Disconnect each unit
• Measure capacitance across each unit
• Replace faulty unit
• Balance bank
• Energize bank
Fault Location Technique
• Unbalance protection provides primary
protection against unit or element failures in
capacitor banks
• Unbalance protection methods
♦ Phase voltage
♦ Neutral voltage
♦ Phase current
♦ Neutral current
Fault Location Technique
• Unbalance protection uses measured
quantities from instrument transformers to
calculate unbalance quantity
• Unbalance quantity is phasor
♦ Magnitude
♦ Phase angle
Fault Location Technique
Phase and Section With Faulty Unit
Reference
Quantity
Unbalance
Quantity
ɸ°
±15°
Fault Location Technique
• Supervised by alarm or trip for sensitivity
• ±15° blinder applied for security
• Affected by fusing method
• Immune to inherent unbalance
Advantages of Proposed Fault
Location Technique
• Minimal outage time – by identifying phase
and section
• Economical – embedded in protection
• Versatile – can be applied to wide range of
bank configurations
Power System Modeled in RTDS
Load
L1G1 T1
Capacitor
Bank
Phase Voltage Unbalance Protection Single-Wye Bank
DVp = VBUSp – Kp • VTAPp
Bus
Tap
ABC
VBUSp
VTAPp
Fault Location Principle
ALARMTRIP
DVpA
–15° Φ 15°
165° Φ –165°
Enable
1
2
Switch at Position a if Bank Is Fuseless
Switch at Position b if Bank Is Fused
2
1Phase p
Top Section
Phase p
Bottom Section
a
b
1
2
a
b
Capacitor Bank Model
12
3
Single Capacitor Unit
88 kV Bus
Tap
4
4 Top
Bottom
4
Fault in Phase A and Top Section
Fault in Phase A and Bottom Section
Neutral Voltage Unbalance Protection Single-Wye Bank
DVG = VBUSA + VBUSB + VBUSC – 3 • VN –
(K1 • (VBUSB – VN) + K2 • (VBUSC – VN))
BusABC
VBUSp
VN
N
Fault Location Principle
ALARM
TRIP
DVGA
–15° Φ 15°
165° Φ –165°
Enable
1
2
–135° Φ –105°
45° Φ 75°
105° Φ 135°
–75° Φ –45°
3
4
5
6
2
1Phase A
4
3Phase B
6
5Phase C
Capacitor Bank Model
230 kV Bus
8
ABC
8N
1
8
Single Capacitor Unit
Fault in Phase A
Fault in Phase C
Neutral Voltage Unbalance Protection Double-Wye Bank
DVG = VNn – Kn • V1BUS
Bus ABC
VBUSp N n
VNn
RightLeft
Fault Location Principle
ALARM
TRIP
DVGA
–15° Φ 15°
165° Φ –165°
Enable
–135° Φ –105°
45° Φ 75°
105° Φ 135°
–75° Φ –45°
Switch at Position a if Bank Is FuselessSwitch at Position b if Bank Is Fused
1
2 Phase A Left Section
Phase A Right Section
a
b
2
1
a
b
3
4 Phase B Left Section
Phase B Right Section
a
b
4
3
a
b
5
6 Phase C Left Section
Phase C Right Section
a
b
6
5
a
b
1
2
3
4
5
6
Phase Current Unbalance Protection H-Bridge Bank
60p = IHp – Kp • ICAPp
BusABC
ICAPA ICAPB ICAPC
IHA IHB IHC
Fault Location Principle
ALARM
TRIP
60pA
–15° Φ 15°
165° Φ –165°
Enable
Switch at Position a if Bank Is FuselessSwitch at Position b if Bank Is Fused
1
2
Phase p
Top Left or
Bottom Right
Section
Phase p
Top Right or
Bottom Left
Section
a
b
2
1
a
b
1
2
Capacitor Bank Model
345 kV Bus
11
2
A
2
11
Top
Right
Bottom
Right
2 2 1
6
Single Capacitor Unit
Fault in Top Left Section of Phase A
Fault in Bottom Left Section of Phase A
Phase Current
and Voltage
Unbalance
Protection Fault Location
Principle
ALARM
TRIP
60pA
–15° Φ 15°
165° Φ –165°
Enable
1
2
3
4
–15° Φ 15°
165° Φ –165° DVpA
TRIP
Enable
ALARM
Switch at Position a if Bank Is Fuseless
Switch at Position b if Bank Is Fused
Phase p
Top Left
Section
a
b
a
b
Phase p
Bottom
Right
Section
a
b
a
b
Phase p
Top
Right
Section
a
b
a
b
Phase p
Bottom
Left
Section
a
b
a
b4
3
1
2
3
4
1
2
4
3
2
1
3
4
2
1
Fault in Top Left Section of Phase A
Fault in Bottom Right Section of Phase A
Phase Current Unbalance Protection Double-Wye Bank
BusABC
IPB IPC
ICA ICB ICC
IPA
Fault Location Principle
ALARM
TRIP
60ФA
–15° Φ 15°
165° Φ –165°
Enable
Switch at Position a if Bank Is FuselessSwitch at Position b if Bank Is Fused
1
2Phase Ф
Left Section
a
b
2
1
a
b
1
2 Phase Ф
Right Section
Neutral Current Unbalance Protection Double-Wye Bank
BusABC
ICAPA ICAPB ICAPC
IN
Left Right
60N = IN – (K1 • ICAPB + K2 • ICAPC)
Fault Location Principle
ALARM
TRIP
60NA
–15° Φ 15°
165° Φ –165°
Enable
–135° Φ –105°
45° Φ 75°
105° Φ 135°
–75° Φ –45°
Switch at Position a if Bank Is FuselessSwitch at Position b if Bank Is Fused
1
2 Phase A Left Section
Phase A Right Section
a
b
2
1
a
b
3
4 Phase B Left Section
Phase B Right Section
a
b
4
3
a
b
5
6 Phase C Left Section
Phase C Right Section
a
b
6
5
a
b
1
2
3
4
5
6
Capacitor Bank Model
15
5
Single Capacitor Unit
33 kV Bus
2
ABC
12Left Right
Fault in Left Section of Phase B
Fault in Right Section of Phase C
Conclusion
• Locating faulty unit is time-consuming
• Proposed fault location technique
♦ Reduces investigating time by 50 to 92%
♦ Minimizes capacitor bank outage time
♦ Is embedded in unbalance protection,
making it economical
♦ Can be applied to any bank configuration
and fusing method
Conclusion
• Proposed fault location technique
♦ Is not affected by inherent unbalance
♦ Provides advanced alarms for planned
maintenance
♦ Provides fuse savings in externally fused bank
• Using multiple unbalance protection
methods improves protection reliability and
fault location
Questions?