Download Information Document – Voltage Control General Operating Practice

Information Document
General Operating Practice – Voltage Control
ID# 2010-007(ARS)
This information documents is for information purposes only and is intended to provide guidance. In the
event of any discrepancy between the information document and the related authoritative document(s) in
effect, the authoritative document(s) governs. Please submit any questions or comments regarding this
information document to [email protected].
1
Purpose
This information document supports VAR-001-AB-1a, Voltage and Reactive Control, and VAR-002-AB1.1b, Generator Operation for Maintaining Network Voltage Schedules and section 304.4 of the ISO rules,
Maintaining Network Voltage. The purpose of this information document is to provide information related
to the general operating practices that the AESO considers when managing voltage control.
This information document is likely of most interest to operators of transmission facilities, legal owners of
generating units, legal owners of aggregated generating facilities, operators of generating units and
operators of aggregated generating units.
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Background
The AESO is responsible for the overall reliability of the interconnected electric system including ensuring
that transmission system voltages (which includes 500 kV, 240 kV, 144 kV, 138 kV, 72 kV, and 69 kV) are
maintained within acceptable levels. Operators of transmission facilities, generating units and aggregated
generating facilities are responsible for operating facilities connected to the transmission system.
The transmission system must be capable of steady state operation within acceptable voltage ranges
during normal and abnormal conditions.
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General Operating Concepts and Practices by the AESO
This section communicates the general operating concepts and practices the AESO uses for controlling
voltage levels of the transmission system.
3.1
These general operating concepts and practices include:
(1)
Immediately address voltage limit violations and work to return operating voltages to within
established limits.
(2)
Maintain voltage levels in the upper end of the desired operating voltage ranges during heavy load
periods to:
(a)
reduce the risk of transmission system instability;
(b)
minimize line losses; and
(c)
be best prepared for contingencies.
(3)
Adjust voltage levels to the upper end of the desired operating voltage range prior to significant
system load increases.
(4)
Coordinate voltage adjustments with operators of transmission facilities, generating units and
aggregated generating facilities so that voltage adjustments in one area do not have adverse
effects in other areas of the interconnected electric system.
(5)
Adjust generating unit terminal or collector bus voltages to ensure reactive power is
proportionately balanced based on maximum continuous rating between generating units or
aggregated generating facilities located in close electrical proximity to each other.
(6)
Issue directives to transmission must-run generating units in accordance with section 302.1 of the
ISO rules, Real Time Transmission Constraint Management, including increasing transmission
must-run levels to help support the voltage levels if the system voltages cannot be maintained
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Information Document
General Operating Practice – Voltage Control
ID# 2010-007(ARS)
within acceptable limits and the generating unit reactive power adjustments, reactor and capacitor
switching, and tap changer adjustments have all been unsuccessful.
(7)
Use static VAr compensators and synchronous condensers in order to provide fast acting reactive
power compensation in the transmission system and dynamic reactive power reserve.
3.2 The AESO may use the following general operating practices when voltages fall below the desired
range:
3.3
4
(a)
issue instructions or directives to apply capacitor banks or remove reactors in the applicable
area;
(b)
issue instructions or directives to adjust transformer taps to raise the system voltage;
(c)
issue instructions or directives to operators of generating units or aggregated generating
facilities in the area to raise the voltage by:
(i)
adjusting the taps on the transmission system step up transformer; or
(ii)
adjusting the set point of the automatic voltage regulator or voltage regulating
system;
(d)
issue instructions or directives to adjust static VAr compensator or synchronous condenser
set points;
(e)
cancel outages that would lead to unacceptable low voltages;
(f)
curtail any or all of opportunity services, export and demand opportunity services;
(g)
issue directives for transmission must run;
(h)
shed firm load; or
(i)
accept the operation of under voltage load shed following a contingency.
The AESO may use the following general operating practices when voltages go above the desired
range.
(a)
issue instructions or directives to remove capacitor banks or apply reactors in the applicable
area;
(b)
issue instructions or directives to operators of generating units or aggregated generating
facilities in the area to lower their voltage by:
(i)
adjusting the taps on the transmission system step up transformer; or
(ii)
adjusting the set point of the automatic voltage regulator or voltage regulating
system;
(c)
issue instructions or directives to adjust transformer taps to lower the system voltage;
(d)
issue instructions or directives to adjust static VAr compensator or synchronous condenser
set points; or
(e)
remove lightly loaded lines from service while considering next contingency impacts following
removal of a line for voltage control.
Operator Requests
This section provides general information regarding requests from an operator of a transmission
facility and an operator of a generating unit for voltage adjustments.
(1)
An operator of a transmission facility may initiate a request to the AESO for a voltage adjustment
on its transmission system or an adjacent transmission system if the transmission operator
identifies the need. The AESO will assess the need based on the overall system voltage and
immediate or upcoming events of which the AESO is aware. If the AESO does not agree with the
need for the adjustment, the AESO will provide an explanation to the operator.
(2)
An operator of a generating unit or aggregated generating facility may initiate a request to the
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Information Document
General Operating Practice – Voltage Control
ID# 2010-007(ARS)
AESO for a voltage adjustment on the generating unit or aggregated generating facility if the
operator identifies the need. The AESO will assess this need based on the overall system voltage
and immediate or upcoming events of which the AESO is aware. If the AESO does not agree with
the need for the adjustment, the AESO will provide an explanation to the operator.
However the AESO should consider whether the generating unit or aggregated generating facility is still
able to supply dynamic reactive power reserves. Of particular concern is when a generating unit or
aggregated generating facility is at a limit; the operator should advise the AESO that the generating unit
or aggregated generating facility is operating at such a limit. However, under weak system conditions
such as during system restoration, it may become more challenging to alleviate this issue.
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Information on Alberta Reliability Standard VAR-001-AB-1a
5.1 Facilities with Exceptions
As determined in accordance with the criteria set out in Appendix 1 of VAR-001-AB-1a, the AESO has
determined that the following wind aggregated generating facilities, as represented by their pool asset
descriptions, are not required to comply with a directive in requirements R5 and R8 of the reliability
standard:
(a) Castle River (CR1);
(b) Cowley Ridge (CRWD); and
(c) McBride Lake (AKE1).
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Information on Alberta Reliability Standard VAR-002-AB-1.1b
6.1 Facilities with Exceptions
As determined in accordance with the criteria set out in the Applicability of VAR-002-AB-1.1b, the AESO
has determined that the following wind aggregated generating facilities, as represented by their pool
asset descriptions, are not required to comply with the requirements in this reliability standard:
(a) Castle River (CR1);
(b) Cowley Ridge (CRWD); and
(c) McBride Lake (AKE1).
6.2 Information on the Requirements
R3 –Examples of out of service conditions may include that the automatic voltage regulator or voltage
regulating system has failed, has been placed in manual or has been changed to a mode other than
voltage control.
The time frame of the reporting has not been specified; if the operator of the generating unit is attempting
to deal with concerns that affect equipment or personnel safety, requiring the operator to contact the
AESO within a specific period may comprise the operator’s ability to correct these concerns.
Revision History
Effective Date
Description of Changes
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