Path Operator Task Force
Matthew Hunsaker
WECC Staff Liaison
MEMO
Date:
December 12, 2014
To:
WECC Standards Department
Subject:
WECC-0111 TOP-007-WECC-1a, System Operating Limits and
Associated Path Table
Attachment A for WECC-0111 Standard Authorization Request (SAR)
The WECC Path Operator Task Force (TF) is recommending retirement of WECC-0092, TOP-007-WECC-1a
(TOP), System Operating Limits.
Having concluded a review of the TOP, peripheral NERC Standards, and WECC Reliability Coordinator
procedures, the TF has concluded that the TOP should be retired because it is redundant to existing NERC
Standards and Reliability Coordinator procedures.
Background
On April 21, 2011, in Order 752 FERC approved the TOP as a permanent replacement for TOP-SDT-007-0, the
TOP’s “Version Zero” predecessor. The Effective Date of the TOP was set as July 1, 2011.
The Purpose of the TOP is to ensure that when actual flows on specified WECC paths were exceeded, the
associated schedules and flows did not exceed a specified duration. Specific paths are those identified in the
“Major WECC Transfer Paths in the Bulk Electric System” (Table), an attachment to the TOP. The Table is
incorporated by reference into the TOP.
The below table identifies the NERC Standards and Reliability Coordinator procedures in which each of the
TOP Requirements is duplicated.
TOP-007-WECC-1 Requirement
R1. When the actual power flow
exceeds an SOL for a Transmission path,
the Transmission Operators shall take
immediate action to reduce the actual
power flow across the path such that at
no time shall the power flow for the
Transmission path exceed the SOL for
more than 30 minutes. [Violation Risk
Covered Elsewhere
FAC-014-2
Establish and Communicate System Operating Limits
R2. The Transmission Operator shall establish SOLs (as
directed by its Reliability Coordinator) for its portion of
the Reliability Coordinator Area that are consistent with
its Reliability Coordinator’s SOL Methodology.
1
Factor: High] [Time Horizon: Real-time
Operations]
R5.2. The Transmission Operator shall provide any SOLs it
developed to its Reliability Coordinator and to the
Transmission Service Providers that share its portion of
the Reliability Coordinator Area.
Peak Reliability Coordinator System Operating Limit
(SOL) Methodology Version 7.0

Item #2, page 6 – “If any of the acceptable pre- or
post-contingency system performance criteria
stipulated in this Methodology are not being met,
an SOL is being exceeded.”

Item #3, page 6 – Pre-Contingency : Acceptable
system performance for the pre-contingency state
in the Operations Horizon is characterized by the
following [NERC Standard FAC-011-2 R2.1]:
a. The BES shall demonstrate transient,
dynamic and voltage stability.
b. All Facilities shall be within their
continuous Facility Ratings and thermal
limits (Refer to illustration in Appendix II).
c. All Facilities shall be within their precontingency voltage limits.
d. All Facilities shall be within their stability
limits.

Item #4, page 7 – Post-Contingency [SCs]:
Acceptable system performance for the postcontingency state for Single Contingencies (SC) in
the Operations Horizon is characterized by the
following (NERC Standard FAC-011-2 R2.2):
a. The BES shall demonstrate transient,
dynamic and voltage stability.
b. All Facilities shall be within their applicable
short-term Facility Ratings and thermal
limits. (Refer to illustration in Appendix II).
c. All Facilities shall be within their postcontingency voltage limits.
d. All Facilities shall be within their stability
limits.
e. Cascading or uncontrolled separation shall
not occur.

Item #8, page 8 – Conditions that expose the
system to unacceptable BES performance cannot
2
be allowed to continue indefinitely. As such, when
the system is experiencing unacceptable pre- or
post-contingency performance, the system must
be adjusted as soon as practicable to prepare for
the next Contingency.

Item #9, page 9 – When system studies conducted
throughout the Operations Horizon (including
Real-time Assessments) indicate that any of the
acceptable post-contingency system performance
criteria are not being met, the TOP shall take precontingency actions to achieve acceptable
performance. These actions may include, at a
minimum, the following: [NERC Standard FAC011-2 R2.4]
a. Commit and re-dispatch generation.
b. Make adjustments to the uses of the
transmission system (e.g., schedule
curtailments/adjustments).
c. Make changes to system topology.

Item #47, page 18 – TOPs and the RC shall identify
the subset of SOLs that qualify as IROLs consistent
with this SOL Methodology. When a TOP
identifies an SOL that qualifies as an IROL, the TOP
shall communicate the results of its analysis with
impacted TOPs and the Peak RC. The Peak RC shall
make the final determination whether the
identified SOL shall be declared an actual IROL.

Item #48. Page 18 – SOLs qualify as IROLs when
impact containment cannot be demonstrated as
described in the ‘Impact Containment and IROL
Load Impact’ section below or when studies
indicate that instability, Cascading, or
uncontrolled separation may occur resulting in
uncontrolled interruption of load equal to or
greater than 1000 MW.
IROL-009-1, Reliability Coordinator Actions to Operate
Within IROLs
R3. When an assessment of actual or expected system
conditions predicts that an IROL in its Reliability
Coordinator Area will be exceeded, the Reliability
Coordinator shall implement one or more Operating
Processes, Procedures or Plans (not limited to the
3
Operating Processes, Procedures, or Plans developed for
Requirements R1) to prevent exceeding that IROL.
(Violation Risk Factor: High) (Time Horizon: Real-time
Operations)
R4. When actual system conditions show that there is an
instance of exceeding an IROL in its Reliability
Coordinator Area, the Reliability Coordinator shall,
without delay, act or direct others to act to mitigate the
magnitude and duration of the instance of exceeding that
IROL within the IROL’s Tv. (Violation Risk Factor: High )
(Time Horizon: Realtime Operations)
PRC-004-WECC-1, Protection System and Remedial
Action Scheme Misoperation
R2.3. If the Protection System or RAS has a SecurityBased or Dependability-Based
Misoperation and a FEPS and FERAS is not in service to
ensure BES reliability, Transmission Owners or Generator
Owners shall repair and place back in service within 22
hours the Protection System or RAS that misoperated. If
this cannot be done, then Transmission Owners and
Generator Owners shall perform the following. [Violation
Risk Factor: High] [Time Horizon: Same-day Operations]
R2.3.1. When a FEPS is not available, the Transmission
Owners shall remove the associated Element from
service.
R2.3.2. When FERAS is not available, then:
2.3.2.1. The Generator Owners shall adjust generation to
a reliable operating level, or
2.3.2.2. Transmission Operators shall adjust the SOL and
operate the facilities within established limits.
TOP-004-2
Transmission Operations
R1. Each Transmission Operator shall operate within the
Interconnection Reliability Operating Limits (IROLs) and
System Operating Limits (SOLs).
R4. If a Transmission Operator enters an unknown
operating state (i.e. any state for which valid operating
limits have not been determined), it will be considered to
4
be in an emergency and shall restore operations to
respect proven reliable power system limits within 30
minutes.
R5. Each Transmission Operator shall make every effort
to remain connected to the Interconnection. If the
Transmission Operator determines that by remaining
interconnected, it is in imminent danger of violating an
IROL or SOL, the Transmission Operator may take such
actions, as it deems necessary, to protect its area.
R6. Transmission Operators, individually and jointly with
other Transmission Operators, shall develop, maintain,
and implement formal policies and procedures to provide
for transmission reliability. These policies and procedures
shall address the execution and coordination of activities
that impact inter- and intra-Regional reliability, including:
R6.1. Monitoring and controlling voltage levels and real
and reactive power flows.
R6.2. Switching transmission elements.
R6.3. Planned outages of transmission elements.
R6.4. Responding to IROL and SOL violations.
TOP-007-0
Reporting System Operating Limit (SOL) and
Interconnection reliability Operating Limit (IROL)
Violations
R1. A Transmission Operator shall inform its Reliability
Coordinator when an IROL or SOL has been exceeded and
the actions being taken to return the system to within
limits.
R2. Following a Contingency or other event that results in
an IROL violation, the Transmission Operator shall return
its transmission system to within IROL as soon as
possible, but not longer than 30 minutes.
R3. A Transmission Operator shall take all appropriate
actions up to and including shedding firm load, or
directing the shedding of firm load, in order to comply
with Requirement R2.
5
R4. The Reliability Coordinator shall evaluate actions
taken to address an IROL or SOL violation and, if the
actions taken are not appropriate or sufficient, direct
actions required to return the system to within limits.
TOP-008-1
Response to Transmission Limit Violations
R1. The Transmission Operator experiencing or
contributing to an IROL or SOL violation shall take
immediate steps to relieve the condition, which may
include shedding firm load.
R2. Each Transmission Operator shall operate to prevent
the likelihood that a disturbance, action, or inaction will
result in an IROL or SOL violation in its area or another
area of the Interconnection. In instances where there is a
difference in derived operating limits, the Transmission
Operator shall always operate the Bulk Electric System to
the most limiting Parameter.
VAR-001-2b
Generator Operation for Maintaining Network Voltage
Schedules
R2. The Transmission Operator shall not
have the Net Scheduled Interchange for
power flow over an interconnection or
Transmission path above the path’s SOL
when the Transmission Operator
implements its real-time schedules for
the next hour. For paths internal to a
Transmission Operator Area that are
not scheduled, this requirement does
not apply. [Violation Risk Factor:
Medium] [Time Horizon: Real-time
Operations]
R2.1. If the path SOL decreases within
20 minutes before the start of the hour,
the Transmission Operator shall adjust
the Net Scheduled Interchange within
R10. Each Transmission Operator shall correct IROL or
SOL violations resulting from reactive resource
deficiencies (IROL violations must be corrected within 30
minutes) and complete the required IROL or SOL violation
reporting.
NERC Reliability Functional Model Version 5 (Model)
defines the TOP tasks that are in conflict with R2. The
Model assigns the Interchange Arrangement to
Transmission Service Provider (TSP).
From the Model the tasks assigned to the TOP are to:
1. Monitor and provide telemetry (as needed) of all
reliability-related parameters within the reliability area.
2. Monitor the status of, and deploy, facilities classed as
transmission assets, which may include the transmission
lines connecting a generating plant to the transmission
system, associated protective relaying systems and
Special Protection Systems.
3. Develop system limitations such as System Operating
Limits and Total Transfer Capabilities, and operate within
6
30 minutes to the new SOL value. Net
Scheduled Interchange exceeding the
new SOL during this 30-minute period
will not be a violation of R2.
those limits.
4. Develop and implement emergency procedures.
5. Develop and implement system restoration plans.
6. Operate within established Interconnection Reliability
Operating Limits.
7. Perform reliability analysis (actual and contingency) for
the Transmission Operator Area.
8. Adjust flow control devices within the transmission
area to maintain reliability.
9. Deploy reactive resources to maintain transmission
voltage within defined limits.
From the Model, the TSP tasks are to:
1. Receive transmission service requests and process
each request for service according to the requirements of
the tariff.
a. Maintain commercial interface for receiving and
confirming requests for transmission service according to
the requirements of the tariff (e.g., OASIS).
2. Determine and post available transfer capability
values.
3. Approve or deny transmission service requests.
4. Approve Arranged Interchange from transmission
service arrangement perspective.
5. Allocate transmission losses (MWs or funds) among
Balancing Authority Areas.
INT-006-3
Response to Interchange Authority
R1.2. Each involved Transmission Service Provider shall
confirm that the transmission service arrangements
associated with the Arranged Interchange have adjacent
Transmission Service Provider connectivity, are valid and
prevailing transmission system limits will not be violated.
7
8