NOTICE DATE: November 13,
2008
NOTICE TYPE: M-D111308-01
Legal
SHORT DESCRIPTION: Protocol
Interpretation Request on Reactive Power Capability Requirements
INTENDED AUDIENCE: All ERCOT
Market Participants
LONG DESCRIPTION: An Entity
has submitted to ERCOT a Protocol Clarification/Interpretation Request (PIR)
regarding subsection (2) in Protocol Section 6.5.7.1, Generation Resources
Required to Provide VSS Installed Reactive Capability, and subsection (5) in
Protocol Section 6.7.6, Deployment of Voltage Support Service. Specifically,
the PIR seeks clarification on issues surrounding Reactive Power capability
requirements.
ERCOT provides the following guidance to the questions
submitted by the Entity.
Yes. Protocol Section 6.5.7.1(2) sets the Reactive
Power capability requirement for all Generation Resources that provide Voltage
Support Service (VSS). The section states that a Generation Resource is
required to have and maintain an Unit Reactive Limit (URL) with a power factor
capability of +/- 0.95, determined at its net max output to the transmission
system, and that this capability must be maintained – no exceptions are
provided.
There is no minimum Reactive Power capability
requirement. The Reactive Power requirement is set forth in Protocol Section
6.5.7.1, Generation Resources Required to
Provide VSS Installed Reactive Capability. Specifically, subsection
(2) states:
Generation Resources required to provide VSS except as
noted below in items (3) or (4), shall
have and maintain a URL which has an over-excited (lagging) power factor
capability of ninety-five hundredths (0.95) or less and an under-excited
(leading) power factor capability of ninety-five hundredths (0.95) or less,
both determined at the generating unit’s maximum net power to be supplied
to the transmission grid and at the transmission system Voltage Profile
established by ERCOT, and both measured at the point of interconnection to the
TDSP.
As described in the response to Question 1, Protocol
Section 6.5.7.1(2) states that a Generation Resource must provide the MVAR
requirement (+/- 0.95 power factor) calculated at the maximum net output to the
ERCOT Transmission Grid, and that level must be available at all MW output
levels.
ERCOT, or TSPs designated by ERCOT, have the right to
instruct Generation Resources to make adjustments for voltage support within
the URL capacity limits. However, dispatching a Generation Resource within a
URL range is the right of the system operator, and is unrelated to, and does
not affect a Generation Resource’s obligation to maintain a power factor
capability of +/- 0.95 when dispatched by ERCOT or TSPs.
Protocol Section 6.7.6(5) confirms the power factor
capability requirement in Protocol Section 6.5.7.1(2). Specifically, the first
sentence reads:
At all times a Generation Resource unit required to
provide VSS is On-Line, the URL must be available for utilization at the
generating unit’s continuous rated active power output, and Reactive Power up to the unit’s operating
capability must be available for utilization at lower active power output levels.
Therefore, under this Protocol as well, the power
factor capability requirement does not
decrease with decreasing generation output. A Generation Resource must be able
to maintain the MVAR capability requirement as described in Protocol Section
6.5.7.1(2) even with decreasing power output.
The second sentence in Protocol Section 6.7.6(5)
states:
In no event shall the Reactive Power available be less
than the required installed reactive capability multiplied by the ratio of the
lower active power output to the generating unit’s continuous rated
active power output, and any Reactive Power available for utilization must be
fully deployed to support system voltage upon request by ERCOT, or a TSP.
This sentence does not conflict with the power factor
capability requirement in the first sentence or Protocol Section 6.5.7.1(2) by
establishing a minimum reactive capability requirement. In fact, as described
above, the requirement in 6.5.7.1(2) is confirmed in the first sentence of this
section. The language in the second sentence of this section merely accounts
for situations in which a Generation Resource encounters equipment-related
issues or other unforeseen circumstances that may cause the Reactive Power
capability to be less than the requirement in Protocol Section 6.5.7.1(2). If
the Reactive Power is less than the calculation described in the second
sentence, then the Generation Resource’s ability to support system
voltage may jeopardize the reliability of the ERCOT Transmission Grid.
Both references above refer to the Net High Capability
Limit provided by the Generation Resource to ERCOT through resource
registration. Net High Capability Limit is the net high MW generation output
based on the rating of plant equipment minus plant Load.
CONTACT:
If you have any questions, please contact your ERCOT Account Manager. You may
also call the general ERCOT Client Services phone number at (512) 248-3900 or
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