Protection System Modeling
Paul McGlynn
PJM System Planning
11/7/13
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Background
• Table 1 of the NERC TPL Standard identifies
transmission system performance requirements following
various contingencies
– Old TPL Standard referred to as Category A (no contingencies),
Category B (events resulting from the loss of a single element) and
Category C (events resulting in the loss of two or more elements)
– New TPL Standard is similar but category of events are P0 through P7
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Issue
•
•
Recently been suggested by a
stakeholder that the TPL standards
require the transmission planner to
evaluate the failure of a blocking relay
that would result in the simultaneous loss
of two circuits
Entity is suggesting the transmission
planner should evaluate this type of an
event as a Category C event based on
the hi-lighted section of Table 1 on the
right.
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Blocking Relay Failure Example
•
•
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Fault on Line A-C
Line relays at substation A and
substation C properly detect the Sub A
fault and open the breakers
shown
Blocking relay failure on line C-E
causes the breaker at substation
E to incorrectly open for the fault
Sub B
on line A-C
All breakers open at roughly the
same time (typically on the order
of 4 cycles for 230 kV and above
facilities)
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Sub C
Sub D
Sub E
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Discussion
•
Table 1 of the old TPL standard requires the transmission planner to
simulate “SLG Fault, with Delayed Clearing (stuck breaker or protection
system failure)” on a transmission element
•
The same event in the new standard is “P5 Multiple Contingency (Fault
plus relay failure to operate)” and requires the transmission planner to
simulate “Delayed Fault Clearing due to the failure of a non-redundant
relay protecting the Faulted element to operate as designed” on a
transmission element
•
These are the only references to relay failures in the table of events that
need to be simulated.
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Discussion
•
•
•
•
PJM has historically applied the criteria by simulating faults with
delayed clearing (i.e. the fault remains on the system longer) and
simulating the resulting breaker operations due to the relay failure to
operate.
PJM evaluates all combinations of two single contingency outages as
part of our N-1-1 testing however system adjustments are completed
between contingencies
PJM has not historically evaluated the simultaneous loss of two
transmission elements due to a fault and the incorrect operation of a
blocking relay as a “Category C” event
Following are examples of events that PJM evaluates as part of our
“category C delayed clearing” analysis
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Relay Failure - Delayed Clearing Example
•
•
•
Fault on Line A-C
Line relays at substation A
Sub A
open the line breaker (in
approximately 4 cycles)
Primary line relays at
substation C fail to operate.
Back-up relays operate to
Sub B
clear the fault after some time
delay (10-15 cycles)
Sub C
Sub D
Sub E
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Breaker Failure - Delayed Clearing Example
•
•
•
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Fault on Line A-C
Line relays at substation A open
the line breaker (in
Sub A
approximately 4 cycles)
Line relays at substation C
operate to clear the fault but
circuit breaker (shown in black)
fails to clear the fault
Sub B
After some time delay, breaker
failure relays at substation C
open the breakers shown
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Sub C
Sub D
Sub E
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Discussion
•
•
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NERC standards require transmission planners to simulate multiple single
contingency outages through our N-1-1 testing. However system
adjustments are made after the first contingency and prior to simulating the
second contingency.
N-1-1 testing does not simulate two simultaneous single contingencies.
Application of a criteria that would simulate the simultaneous outage of two
unrelated BES facilities would likely require significant upgrades due to
thermal issues and stability issues.
Relay system considerations
– Use other schemes that do not rely on a blocking signal to remain secure
– Periodically test blocking signals to ensure they will work when required
– Automatic reclosing considerations
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Discussion and Follow-Up?
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•
PJM does not believe that the NERC TPL standards require the
transmission planner to simulate the simultaneous loss of two BES
elements due to a fault on one facility and the incorrect operation of
a blocking relay on an adjacent facility, as a category C event under
the old standard or as a category P3 – P7 event under the new TPL
standard.
Do stakeholders believe PJM should be evaluating the simultaneous
loss of two or more BES facilities due to a blocking relay failure?
– PJM would need information from TOs on the location and the contingencies that
could result
•
Other ideas?
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