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Generator Test Data, Generator Capability Curve,

and NPRR 366 Terms

March 14, 2012

Mike Noth &

Bracy Nesbit

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Common Interests

• Provide a stable and reliable system

• Comply with regulatory requirements (avoid non-compliance)

• Best value for customers

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Review of Generator Capability

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Area the Generator Can Safely Operate

GENERATOR CAPABILITY

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Critical VSS Areas of Generator OperationD

ecreasing PF

Increasing PF

Increasing PF

Decreasing P

F

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NPRR 366 Problem

• The system needs to adhere to a voltage profile to remain stable

• No single generator can prop up or sink the system voltage

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Simple Nomograph of voltage from Generator Terminals to BES

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The blue diamonds represent actual test points from leading and lagging reactive tests.Gen Gross are points measured at the Generator terminals.

Red square represents 0.95 to 1.05 pu Voltage and +/- 0.95 power factor.

Actual Generator Test Data – At Generator Terminals

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Dashed green lines roughly represent +/- 2% pu of Voltage profile value and bounded by red =/- 0.95 power factor lines.

The blue diamonds represent actual test points from leading and lagging reactive tests.Net to BES are points measured at the POI.

Red square represents 0.95 to 1.05 pu Voltage and +/- 0.95 power factor.

Actual Generator Test Data – At POI

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Existing Nodal Protocol 3.15

(3) Generation Resources required to provide VSS must be capable of producing a defined quantity of Reactive Power to maintain a Voltage Profile established by ERCOT. Generation Resources shall comply with the following Reactive Power Requirements: an over-excited (lagging) power factor capability of 0.95 or less and an under-excited (leading) power factor capability of 0.95 or less, both determined at the generating unit's maximum net power to be supplied to the ERCOT Transmission Grid and at the transmission system Voltage Profile established by ERCOT, and both measured at the POI. The Reactive Power requirements shall be available at all MW output levels and may be met through a combination of the Generation Resource’s Unit Reactive Limit (URL), which is the generating unit’s dynamic leading and lagging operating capability, and/or dynamic VAr capable devices. This Reactive Power profile is depicted graphically as a rectangle. …continued…

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Existing Nodal Protocol 3.15

(3) Generation Resources required to provide VSS must be capable of producing a defined quantity of Reactive Power to maintain a Voltage Profile established by ERCOT. Generation Resources shall comply with the following Reactive Power Requirements: an over-excited (lagging) power factor capability of 0.95 or less and an under-excited (leading) power factor capability of 0.95 or less, both determined at the generating unit's maximum net power to be supplied to the ERCOT Transmission Grid and at the transmission system Voltage Profile established by ERCOT, and both measured at the POI. The Reactive Power requirements shall be available at all MW output levels and may be met through a combination of the Generation Resource’s Unit Reactive Limit (URL), which is the generating unit’s dynamic leading and lagging operating capability, and/or dynamic VAr capable devices. This Reactive Power profile is depicted graphically as a rectangle. …continued…

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Decreasing P

FIncreasing P

FIncreasing P

FD

ecreasing PF

PF=0.95 or Less

Capacitive VAr devices have to be added

Reactive VAr devices have to be added

PF=0.95 or Less

Present Protocol Requirement to meet the Voltage Profile

There are no boundaries for the Generation Resource to supply reactive power in order to meet the Voltage Profile

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Back to the NPRR 366 Problem

• The system needs to adhere to a voltage profile to remain stable

The Generation Resource must operate to the operating point determined by the Transmission Operator

• No single generator can prop up or sink the system voltage

The Generation Resource will operate up to the generator capability

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Generating Resource Operating Modes Required to Meet the Voltage Profile – Generator Operating Point determined by Transmission Operator

VAR-002-1.1b

R2. Unless exempted by the Transmission Operator, each Generator Operator shall maintain thegenerator voltage or Reactive Power output (within applicable Facility Ratings1) as directed by the Transmission Operator.

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Nodal Protocol 3.15 Option A Revision

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