12, 1995
NORTHWEST POWER POOL
Operating Manual
MINIMUM OPERATING RELIABILITY CRITERIA
SECTION I - INTRODUCTION
Interconnected operation of systems, Pools and regions throughout the United States and Canada
requires responsible action by the dispatchers of all systems. Such broad interconnected operation
makes it necessary for each dispatcher to recognize that the operation of any one system may affect
other systems far removed from the dispatchers own system. This type of operation requires full
cooperation and communication at the dispatcher level during periods of both normal and emergency
operation. Sections II and Ill below set forth the criteria to which the members of the Northwest Power
Pool have agreed to adhere in the operation of their respective systems. Conformity to these cntena will
assure NWPP systems of compliance with NERCs Criteria for Interconnected Operation and WSCCs
Minimum Operating Reliability Criteria.
SECTION Il - GENERAL OPERATING RELIABILITY CRITERIA
Those operating criteria that are general in nature and necessary in the normal operation of the
interconnected bulk power systems are set forth in this section.
1.0
Basic Criteria
The bulk power systems will be operated at all times so that general system instability,
uncontrolled separation, cascading outages, or voltage collapse will not occur as a result
of the most severe single contingency. A single contingency may generally be assumed
to mean the loss of a single system element; however, the outage of multiple system
elements should be treated as a single contingency if caused by a single event of
sufficiently high likelihood. Multiple contingency outages of a credible nature will be
examined, and the system will be operated to protect against general system instability,
uncontrolled separation or cascading outages for these contingencies.
When it is agreed that a disturbance on specific facilities occurs more often than should
be reasonably expected and results in an undue burden on other systems, the owners of
the facilities should take measures to reduce the frequency of occurrence of the
disturbance, and cooperate with other systems in taking measures to reduce the effects
of such disturbance.
Continuity of service to load is the primary objective of the Minimum Operating Reliability
Criteria. Preservation of interconnections during disturbances is a secondary objective
except when preservation of interconnections will minimize the magnitude of load
interruption or will expedite restoration of service to load.
It is undesirable for the loss of load to exceed the amount of load designed to be tripped. Section D
Minimum Operating Reliability Criteria
Page 2 of 28
Revised July 12, 1995
This applies to all levels of system underfrequency load shedding programs,
undervoltage load tripping schemes or other controlled remedial actions. It applies
whether the initiating disturbance occurs within or outside the affected system. This may
require member systems to establish maximum import levels to meet these cnteria. The
necessary operating procedures, equipment, and remedial action schemes shall be in
place to prevent unplanned or uncontrolled loss of load or total system shutdown.
2.0 System
Adjustments
The bulk power systems will be operated to achieve the highest practical degree of
service reliability. Appropriate remedial action will be taken promptly to eliminate any
abnormal conditions which jeopardize reliable operation.
3.0 Operating
Reserve
The reliable operation of interconnected bulk power systems requires that adequate
generating capacity be available at all times to maintain scheduled frequency, including
capacity necessary to supply requirements for load variations and errors in load
forecasting and to replace generating capacity lost due to forced outages of generation or
transmission equipment. The Northwest Power Pool Operating Committee
representatives have agreed to operate their systems in accordance with the following:
3.1
Minimum Operating Reserve
Each control area shall maintain minimum operating reserve as follows:
(a)
For Regulating Margin
Sufficient Spinning Reserve, immediately responsive to automatic
generation control to provide sufficient regulating margin to allow the
control area to meet NERCs Control Performance Criteria.
(b)
For Forced Outages
Plus, an additional amount of Operating Reserve, which can be made
effective within 10 minutes, equal to the sum of 5 percent of the load
responsibility served by hydro generation and 7 percent of the load
responsibility served by thermal generation (at least half of which must
be Spinning Reserve in excess of the requirement in (a) above). The
combined unit ramp rate of each systems on-line, unloaded generating
capacity must be capable of responding to the Spinning Reserve
requirement of that system.
Load Responsibility: System or area finn load demand plus those
firm sales minus those firm purchases for which reseive capacity
is provided by the supplier.
(c)
For lnterruptible lmports
Plus, an additional amount of Operating Reserve, which can be made
effective within 10 minutes, equal to interruptible imports.
(d)
For On-demand Obligations to Others Section D
Minimum Operating Reliability Criteria
Page 3 of 28
Revised July 12, 1995
Plus, an additional amount of Operating Reserve, which can be made
effective within 10 minutes, equal to on-demand obligations to other
systems.
(e)
Nonspinning Reserve Obligations
The Nonspinning Reserve obligations identified in 3.1 .b, 3.1 .c, and
3.1 .d, if any, can be met by use of the following:
(1)
Interruptible load.
(2)
Interruptible exports.
(3)
On demand rights from other systems.
(4)
Spinning Reserve in excess of requirements in 3.1 .a and
3.1.b.
(5)
Off line generation which qualifies as Nonspinning Reserve.
3.2
Operating Reserve Obligation
Operating Reserve Obligation is defined as the amount of Operating Reserve a
utility must have available to replace capacity loss of any unit which trips, fails to
start, load, or continue to generate on its own or some other system due to an
emergency. Operating Reserve Obligation is equal to 5 percent of a utilitys Load
Responsibility served from hydro resources plus 7 percent of its Load
Responsibility served from thermal resources, and must be fully available within
10 minutes.
3.3
Operating Reserve Practices and Procedures
(a)
Distribution of Operating Reserve
Each system shall exercise prudent operating judgment in distributing
Operating Reserve, taking into account effective utilization of capacity in
an emergency, time required to be effective, transmission limitations, and
local area requirements. Spinning Reserve should be distributed to
maximize the effectiveness of governor action.
(b)
Knowledge of Operating Reserve
Operating Reserve shall be calculated by each system such that the
amount available in the next 10 minutes will be known at all times.
(c)
Entitlement to Request Operating Reserve
In the event of a forced outage of capacity on a NWPP system, that
system is entitled to request and schedule capacity and energy from
other Pool systems after full utilization of its own Operating Reserve
Obligation plus any additional Operating Reserve at its disposal. Upon
request, a system is obligated to schedule the delivery of capacity and
energy to replace a forced outage of capacity on another system up to
the amount of its Operating Reserve Obligation, provided that capacity is
not already being used to replace a forced outage of capacity on its own
or some other Pool system. Section D
Minimum Operating Reliability Criteria
Page 4 of 28
Revised July 12, 1995
The current method of meeting the NWPP Operating Reserve
requirements is clarified and outlined in Appendix 1 of the NWPP
Operating Manual. It is recommended in Appendix 1 that once a Pool
utility has determined that Operating Reserve Obligation must be
requested from another Pool utility, the most appropriate or adjacent
utility may be the first utility called BPA will usually be first and B. C.
Hydro the second. Regardless of which Pool utility is requested to deliver
its Operating Reserve Obligation, the following practices and procedures
apply.
(d)
Time of Request
Operating Reserve shall be requested within 60 minutes after the
occurrence of an initiating event.
(e)
Accounting for Operating Reserve
Energy associated with the scheduled receipt and delivery of Operating
Reserve Obligation shall be accounted for as Operating Reserve.
(f)
Maximum Time of Use
No system shall draw on the Operating Reserve Obligation of other
systems for a period longer than 60 minutes for any one forced outage.
(g)
Restoration of Operating Reserve
After the occurrence of any event requiring the use of Operating
Reserve, Operating Reserve on the deficient system shall be restored as
promptly as practicable. The time taken to restore Operating Reserve
should not exceed 60 minutes.
(h)
Delivery Options
The delivering system, at its option, may require:
(1)
The return of energy delivered as Operating Reserve, or
(2)
Reimbursement of costs actually incurred through increased
generation to deliver the energy.
(i)
Return of Operating Reserve
If return is required, the receiving system shall return the energy
delivered as Operating Reserve promptly, preferably during like hours
but, in any case, in a manner suitable to the needs of the delivering
system.
(j)
Wheeling
When intermediate systems are involved, any delivery or return of
Operating Reserve shall be exempt from wheeling charges and losses.
Deliveries must be