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© 2018 SDG&E and SEL
Phase-Shifting Transformer Control
and Protection Settings Verification
Bill Cook
San Diego Gas & Electric
Michael Thompson, Kamal Garg, and Milind Malichkar
Schweitzer Engineering Laboratories, Inc.
• Utility high-voltage (HV) transmission system
• Phase-shifting transformer (PST) project
• Protection and control (P&C) design team
• P&C design development
• PST operation fundamentals
• Project design details
• Testing: acceptance, commissioning, and in-service
Introduction
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Utility High-Voltage Transmission System
Utility
Load
Center
500 kV #3
500 kV #1
500 kV #2
230 kV Gen
AZ
230 kV East-West Interconnection
Outage of 500 kV Line #1
Utility
Load
Center
500 kV #3
500 kV #1 Opens
500 kV #2
230 kV GenIncreased
230 kV Flow
Opening of 500 kV Line #1 increases flow
through 230 kV East-West transmission
AZ
230 kV East-West Interconnection
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Outage of 500 kV Line #1
Utility
Load
Center
500 kV #3
500 kV #1 Opens
500 kV #2
230 kV GenControl to Reduce
230 kV Flow
Addition of PSTs provides control
of 230 kV transmission flow
AZ
230 kV East-West Interconnection
• August 2015: Form engineering team
• Fall 2015: Begin PST design
• Spring 2016: Develop detailed schemes
• July 2016: Conduct factory acceptance test (FAT)
• October 2016: Conduct PST operations training
• JanuaryApril 2017: Complete wiring and settings
• April 2017: Perform functional testing for commissioning
• May 1, 2017: Energize and load PSTs; perform in-service testing
P&C Design and Test Schedule
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Two-Core PST
IV
2L CB
PST 2
2S CB
1L CB
PST 1
1S CB
BP CB
S L
NS0L0
Series
Core
Excitation
Core
262T 262T
407T
382T
* Variable with tap position and ARS.
(Excitation secondary includes coarse,
fine, and booster windings.)
0-288T*
PST Impedance and Phase Shift
Net Quadrature Voltage
Booster Winding
Fine Winding
Coarse Winding
A16 N R16 R32 R48
Advance to Retard Tap Position
Quadra
ture
Voltage
A16–N N–R16 R16–R32 R32–R48
B
B
F
C
C
F
BC F
B B F C C
B B F
B
PST Data
Pha
se S
hift (D
egre
es)
Phase Shift (Degrees) % Impedance
Tap Position
% I
mped
ance
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Main 1 Primary and Secondary Protection
9N9S
Load Source
S0
L0
J0
87S
87P
87-PSTnP
87P
63
Protective
Relay
87-PSTnS
87S
87-1/2
POTT
REF
64T
32CC
Protective
Relay
Main 2 Overall Differential Protection
9N9S
Load Source
S0
L0
J0
87O
87-PSTnO
87S
87-1/2
POTT
REF
64T
32CC
Protective
Relay
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IAADD = IABYP + (IAPST1 + IAPST2)
IASUB = IABYP (IAPST1 + IAPST2)
Ratio 0: even distribution of load current
Ratio 1: no load current in one branch
Ratio >1: when circulating current is present
Breaker Bypass Logic
SUBCIRC
ADD
IAIA
IA
• Master / Follower and Independent operation
• Tap position out-of-synchronism
• Circulating apparent power
• Blocking for motor runaway
• Tap set point per CAISO
• Run-to-neutral control function
• PST automatic regulation during N-1 condition
PST Controller Tap Position Logic
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PST Controller Tap Position Logic
CAISO Tap
Set Point
x • yx
y
CAISO Tap
Load in
Tap Reg.
Set Point x • yx
y
+
+Sum
CAISO Tap
Out of
Range
+
–
+
–
Extreme ADV
Tap
Extreme RET
Tap
SCADA
Heartbeat
Current Tap
Maximum
Delta Tap
+
–
Delta CAISO Tap
Position+
–Sum ABS(x) x
Tap Delta
Block Alarm
Local
Auto
PST Controller Front Panel
ENABLED
TRIP
TARGET
RESET
NEUTRAL
SOURCE CB CL
PERMISSIVE
LOAD CB CL
PERMISSIVE
BYPASS CB CL
PERMISSIVE
LOW OVRLD
ALARM
MB ALARM
AUTO BLOCKED
MAN BLOCKED
SPARE
ADVANCE
TAP
FOLLOWER CTRL
MODE
ENABLED
REMOTE
ENABLED
LOCAL
ENABLED
MASTER
CTRL MODE
ENABLED
RUN
TO
NEUTRAL
OFF
INDEPENDENT
CTRL MODE
ENABLED
MANUAL
ENABLED
AUTOMATIC
ENABLED
ALARM,
SEE LCD
PARALLEL
BLOCK
LTC TRIPPED
NA
HI OVRLD
ALARM
RUN TO NEUT
BLOCKED
SPARE
N-1 OVERLOAD
ALARM
LTC OVR CUR
86T TRIPPED
SPARE
RETARD
TAP
SOURCE CB
LOAD CB
BYPASS CB
N-1 ARMED
ISO MODE
OVERRIDE
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• Neutral
• Retard
• Advance
• Extreme retard
• Extreme advance
Tap Position Logic
1
8
4
10
2
x • yx
y
x • yx
y
x • yx
y
x • yx
y
x • yx
y
20
x • yx
y
+
+
SUM+
++
+
ARS Input
AMVXXX
Raw
Tap-Changer
Position
f(x,y)
x
y
Circulating Apparent Power
CIRC
P1 P2P P1
2
CIRC
Q1 Q2Q Q1
2
2 2
CIRCP1 P2 Q1 Q2
S P1 Q12 2
+16–16–32–48 Neutral
Region 1Region 2Region 3
Block Curve
Alarm Curve
CIR
C M
VA
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FAT Procedure
L S
J0S0L0
SER Core
EXT
Core
9S
87P
87S
87O
3ϕ
1ϕ FLOC 9 FLOC 7
FLOC 2
FLOC 1
FLOC 3
87S
87O
87P
9N
87P
87S
87O
PT
FLOC 6 FLOC 8
FLOC 4
FLOC 5
3ϕ
SDGECFE
TL23050
FAT Procedure
Location Description87P 87S and 87O
Fault TypeKCL ATB SEQ POTT
FLOC 1 Series Transformer Tap Y N Y Y Internal
FLOC 2 Series Transformer Delta N Y M M Internal
FLOC 3 Booster Winding Ground N M M M Internal
FLOC 4 Turn-to-Turn N N Y Y Internal
FLOC 5 Booster Turn-to-Turn N N Y Y Internal
FLOC 6 Internal Y Y Y Y Internal
FLOC 7 Internal Y Y Y Y Internal
FLOC 8 IV Bus NOP External
FLOC 9 CFE Line / Bus NOP External
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FLOC 1 Single Phase
Motor Running
Tap Raise / Lower Asserts
T = 0
Tap Raise / Lower Asserts
Motor Running
T = 0 + 1 PI
BCD Counter Disappears
T = 0.4 Seconds
BCD Counter Reasserts
T = 2.9 Seconds
Motor Stops
T = 3.5 Seconds
1
2
3
4
5
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• Verify wiring to and from PSTs and associated circuit breakers
• Verify LTC settings with PST motors and contactors
• Verify local / SCADA, auto / manual, and CAISO set-point controls
• Verify Master / Follower LTC operation
• Perform SCADA testing and prove functionality
• Provide field training on local controls, displays, and indications
• Provide system operator training
• Develop Sequence of Events data to document PST operation
Functional Testing During Commissioning
1. Parallel PST 1 and PST 2, setting tap position for combined
loading of 170 MW outbound. Complete testing.
2. Advance PST 1 to +1 tap and retard PST 2 to 1. Complete
testing, including circulating apparent power calculation.
3. Open PST 2, placing all load on PST 1. Complete testing.
4. Parallel PST 2 with PST 1 on neutral tap and open PST 1. Move
PST 2 tap to same position used in Step 3 and complete testing.
5. Parallel PST 1 with PST 2 on neutral tap. Advance PST 1 to
+1 tap and retard PST 2 to 1. Complete testing.
In-Service Testing During Energization
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PST Loading 87S / 87S
Compensation Matrix
• IS: IA = IB − IC = Matrix 9
(i.e., CCW 30 • 9 = 270°
for ABC phase rotation)
• IT: IA = IC − IB = Matrix 3
(i.e., CCW 30 • 3 = 90°
for ABC phase rotation)
PST Loading 87S / 87S
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Compensation Verification
87P CT Rolled
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• Coordination among multiple teams
• Protection and control design
• Simulator and lab testing
• Training for operations staff
• Field and in-service testing
• CT polarity investigation
• Documentation and field results
Conclusion
Questions?