Utility Protection Practices in PJM

Terry Fix Protective Relay Systems Consultant Dominion Energy Past Chair of PJM Relay Subcommittee Typical Electrical Power System Single-Line Diagram

Transmission Protection Characteristic Transmission Protection Characteristic

Pilot Protection Scheme with Communication

Transmission Breaker Transmission Current and Voltage Sensing Devices Transmission Protective Relays Substation Control House Transmission Substation Lightning Strikes Transmission Power Transformer Windings of a Power Transformer Winding Damage due to Fault Current Equipment Damage Large Power Plants 2003 Northeast Blackout NERC Common Failure Modes Common Equipment Failures Transmission Reclosing Practices

27 Breaker Reclosing Cycle Temporary Transmission Fault

• Fault Clears Open Service Restored

Closed

0.4 sec Fault

28 Breaker Reclosing Cycle Temporary Transmission Fault

• Fault Clears Open Service Restored

Closed

Fault Fault0.4 sec 15 sec

29 Breaker Reclosing Cycle Permanent Transmission Fault

Open

Line Lockout

Closed

Fault Fault Fault Fault

0.4 sec 15 sec 80 sec 30

Fault Types

X X X X X X X X

3 Phase Phase Phase 2 Phase to to to Phase Ground Ground

32 Basic Protective Devices

Fuse Recloser

Overcurrent Relay

33 Fuses

•Basic sectionalizing device •One time operation •Needs to be replaced •Inverse time characteristic •Minimum melt time •Total clear time

34 Fuse Time vs. Current Curve

Inverse Time Characteristic seconds

2.1 •Total Clear Time

0.7 •Minimum Melt Time

500 1000 amps 35 Reclosers

•Basic sectionalizing device •Multiple operations •Inverse time characteristic •Fast “A” curve •Time delayed “B” curve

36 Recloser Time vs. Current Curve

Seconds

2.1 “B” Curve

0.7

“A” Curve

500 1000 Amps 37 Types of Relays

Microprocessor Electromechanical (Schweitzer Relay 38 Relay Time vs. Current Curve

Pick up Seconds Inverse time curve

3.0

1.0 Instantaneous setting

300 500 1000 Amps 39 Protective Device Coordination

• Proper timing and operational sequencing of protective devices • Coordination minimizes customer outages while clearing circuit faults

40 Coordination Curve Fuse, Recloser, Relay

Seconds 160 RV Relay “B” Curve

Recloser 2.1 Fuse 125 N Overcurrent relay Total Clear time delay and 0.7 instantaneous curve “A” Curve

500 1000 Amps 41 DG Protection Issues Reduction of Reach

With DG:

Vr  InwZ23  (Inw  Idg )Z3a

The impedance measured by Vr Idg the relay R: Zr   Z23  Z3a  Z3a Inw Inw disturbance

REDUCES THE REACH! DG Protection Issues Short-Circuit Current

SCENARIO 1: Fault at point ‘a’ 1 I f  Inw  Zth

Zth is the inner impedance of the Thevenin representation of the network in p.u.

With DG:

I f  Inw  Idg AMPLITUDE!

SCENARIO 2: Fault at ‘b2’ With DG: Reverse current flow at the directional relay ‘R’ DIRECTION! DG Protection Issues Voltage Profile

Distributed generation impacts the voltage profile at local buses. DG Protection Issues Reverse Power Flow

Reverse Power Flows cause issues with automatic tap changers. Typical Distribution Substation Construction Equipment Damage Equipment Damage Personal Safety Personal Safety Distribution Reclosing Practices

51 Breaker Reclosing Cycle Temporary Distribution Fault

Open Service Restored

• Fault Clears

Closed

Fault Fault 10 sec 45 sec

52 Breaker Reclosing Cycle Permanent Distribution Fault

Open

Circuit Lockout Closed Fault Fault

10 sec 45 sec Fault

53 How Does DER Integrate into This System

Questions?