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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

3

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

5

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

8

• 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?