MOD-025 Attachment MOD-025 Attachments 1 & 2

Standard MOD-025-2 — Verification and Data Reporting of Generator Real and Reactive
Power Capability and Synchronous Condenser Reactive Power Capability

MOD-025 Attachment 1 – Verification of Generator Real and Reactive Power Capability
and Synchronous Condenser Reactive Power Capability
Periodicity for conducting a new verification:
The periodicity for performing Real and Reactive Power capability verification is as follows:
1. For staged verification; verify each applicable Facility at least every five years (with no
more than 66 calendar months between verifications), or within 12 calendar months of
the discovery of a change that affects its Real Power or Reactive Power capability by
more than 10 percent of the last reported verified capability and is expected to last more
than six months. The first verification for each applicable Facility under this standard
must be a staged test.
2. For verification using operational data; verify each applicable Facility at least every five
years (with no more than 66 calendar months between verifications), or within 12
calendar months following the discovery that its Real Power or Reactive Power capability
has changed by more than 10 percent of the last reported verified capability and is
expected to last more than six months. If data for different points is recorded on different
days, designate the earliest of those dates as the verification date, and report that date as
the verification date on MOD-025, Attachment 2 for periodicity purposes.
3. For either verification method, verify each new applicable Facility within 12 calendar
months of its commercial operation date. Existing units that have been in long term shut
down and have not been tested for more than five years shall be verified within 12
calendar months.
It is intended that Real Power testing be performed at the same time as full load Reactive Power
testing, however separate testing is allowed for this standard. For synchronous condensers,
perform only the Reactive Power capability verifications as specified below.
If the Reactive Power capability is verified through test, it is to be scheduled at a time
advantageous for the unit being verified to demonstrate its Reactive Power capabilities while the
Transmission Operator takes measures to maintain the plant's system bus voltage at the
scheduled value or within acceptable tolerance of the scheduled value.
Verification specifications for applicable Facilities:
1.

For generating units of 20 MVA or less that are part of a plant greater than 75 MVA in
aggregate, record data either on an individual unit basis or as a group. Perform
verification individually for every generating unit or synchronous condenser greater
than 20 MVA (gross nameplate rating).

2.

Verify with all auxiliary equipment needed for expected normal operation in service for
both the Real Power and Reactive Power capability verification. Perform verification
with the automatic voltage regulator in service for the Reactive Power capability
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Standard MOD-025-2 — Verification and Data Reporting of Generator Real and Reactive
Power Capability and Synchronous Condenser Reactive Power Capability

verification. Operational data from within the two years prior to the verification date is
acceptable for the verification of either the Real Power or the Reactive Power
capability, as long as a) that operational data meets the criteria in 2.1 through 2.4 below
and b) the operational data demonstrates at least 90 percent of a previously staged test
that demonstrated at least 50 percent of the Reactive capability shown on the associated
thermal capability curve (D-curve). If the previously staged test was unduly restricted
(so that it did not demonstrate at least 50 percent of the associated thermal capability
curve) by unusual generation or equipment limitations (e.g., capacitor or reactor banks
out of service), then the next verification will be by another staged test, not operational
data:
2.1. Verify Real Power capability and Reactive Power capability over-excited

(lagging) of all applicable Facilities at the applicable Facilities’ normal (not
emergency) expected maximum Real Power output at the time of the
verifications.
2.1.1

Verify synchronous generating unit’s maximum real power and lagging
reactive power for a minimum of one hour.

2.1.2

Verify variable generating units, such as wind, solar, and run of river
hydro, at the maximum Real Power output the variable resource can
provide at the time of the verification. Perform verification of Reactive
Power capability of wind turbines and photovoltaic inverters with at least
90 percent of the wind turbines or photovoltaic inverters at a site on-line.
If verification of wind turbines or photovoltaic inverter Facility cannot be
accomplished meeting the 90 percent threshold, document the reasons the
threshold was not met and test to the full capability at the time of the test.
Reschedule the test of the facility within six months of being able to reach
the 90 percent threshold. Maintain, as steady as practical, Real and
Reactive Power output during verifications.

2.2. Verify Reactive Power capability of all applicable Facilities, other than wind and

photovoltaic, for maximum overexcited (lagging) and under-excited (leading)
reactive capability for the following conditions:
2.2.1

At the minimum Real Power output at which they are normally expected
to operate collect maximum leading and lagging reactive values as soon as
a limit is reached.

2.2.2

At maximum Real Power output collect maximum leading reactive values
as soon as a limit is reached.

2.2.3

Nuclear Units are not required to perform Reactive Power verification at
minimum Real Power output.

2.3. For hydrogen-cooled generators, perform the verification at normal operating

hydrogen pressure.
2.4. Calculate the Generator Step-Up (GSU) transformer losses if the verification

measurements are taken from the high side of the GSU transformer. GSU
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Standard MOD-025-2 — Verification and Data Reporting of Generator Real and Reactive
Power Capability and Synchronous Condenser Reactive Power Capability

transformer real and reactive losses may be estimated, based on the GSU
impedance, if necessary.
3.

Record the following data for the verifications specified above:
3.1. The value of the gross Real and Reactive Power generating capabilities at the end

of the verification period.
3.2. The voltage schedule provided by the Transmission Operator, if applicable.
3.3. The voltage at the high and low side of the GSU and/or system interconnection

transformer(s) at the end of the verification period. If only one of these values is
metered, the other may be calculated.
3.4. The ambient conditions, if applicable, at the end of the verification period that the

Generator Owner requires to perform corrections to Real Power for different
ambient conditions such as:


Ambient air temperature



Relative humidity



Cooling water temperature



Other data as determined to be applicable by the Generator Owner to perform
corrections for ambient conditions.

3.5. The date and time of the verification period, including start and end time in hours

and minutes.
3.6. The existing GSU and/or system interconnection transformer(s) voltage ratio and

tap setting.
3.7. The GSU transformer losses (real or reactive) if the verification measurements

were taken from the high side of the GSU transformer.
3.8. Whether the test data is a result of a staged test or if it is operational data.
4.

Develop a simplified key one-line diagram (refer to MOD-025, Attachment 2) showing
sources of auxiliary Real and Reactive Power and associated system connections for
each unit verified. Include GSU and/or system Interconnection and auxiliary
transformers. Show Reactive Power flows, with directional arrows.
4.1. If metering does not exist to measure specific Reactive auxiliary load(s), provide

an engineering estimate and associated calculations. Transformer Real and
Reactive Power losses will also be estimates or calculations. Only output data are
required when using a computer program to calculate losses or loads.
5.

If an adjustment is requested by the Transmission Planner, then develop the
relationships between test conditions and generator output so that the amount of Real
Power that can be expected to be delivered from a generator can be determined at
different conditions, such as peak summer conditions. Adjust MW values tested to the
ambient conditions specified by the Transmission Planner upon request and submit
them to the Transmission Planner within 90 days of the request or the date the data was
recorded/selected whichever is later.
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Standard MOD-025-2 — Verification and Data Reporting of Generator Real and Reactive
Power Capability and Synchronous Condenser Reactive Power Capability

Note 1:

Under some transmission system conditions, the data points obtained by the Mvar
verification required by the standard will not duplicate the manufacturer supplied
thermal capability curve (D-curve). However, the verification required by the
standard, even when conducted under these transmission system conditions, may
uncover applicable Facility limitations; such as rotor thermal instability, improper tap
settings or voltage ratios, inaccurate AVR operation, etc., which could be further
analyzed for resolution. The Mvar limit level(s) achieved during a staged test or from
operational data may not be representative of the unit’s reactive capability for
extreme system conditions. See Note 2.

Note 2:

While not required by the standard, it is desirable to perform engineering analyses to
determine expected applicable Facility capabilities under less restrictive system
voltages than those encountered during the verification. Even though this analysis
will not verify the complete thermal capability curve (D-curve), it provides a
reasonable estimate of applicable Facility capability that the Transmission Planner
can use for modeling.

Note 3:

The Reactive Power verification is intended to define the limits of the unit’s Reactive
Power capabilities. If a unit has no leading capability, then it should be reported with
no leading capability; or the minimum lagging capability at which it can operate.

Note 4:

Synchronous Condensers only need to be tested at two points (one over-excited point
and one under-excited point) since they have no Real Power output.

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Standard MOD-025-2 — Verification and Data Reporting of Generator Real and Reactive
Power Capability and Synchronous Condenser Reactive Power Capability

MOD-025 Attachment 2
One-line Diagram, Table, and Summary for Verification Information Reporting
Note: If the configuration of the applicable Facility does not lend itself to the use of the diagram,
tables, or summaries for reporting the required information, changes may be made to this form,
provided that all required information (identified in MOD-025, Attachment 1) is reported.
Company:

Reported By (name):

Plant:

Unit No.:

Date of Report:

Check all that apply:
Over-excited Full Load Reactive Power Verification
Under-excited Full Load Reactive Power Verification
Over-excited Minimum Load Reactive Power Verification
Under-excited Minimum Load Reactive Power Verification
Real Power Verification
Staged Test Data
Operational Data

Simplified one-line diagram showing plant auxiliary Load connections and verification data:
Point of
interconnection
C

*

*

*
*

F

flow in direction of arrow; negative
numbers indicate power flow in

D

opposite direction of arrow.

Generator Step Up

*

*
A

Auxiliary or
Station Service
Transformer(s)

Other point(s) of
interconnection

B
Unit Auxiliary
Transformer(s)

E

Generator(s)
Aux bus

Positive numbers indicate power

*

Auxiliary or
Station Service
Transformer(s)

Aux bus

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Standard MOD-025-2 — Verification and Data Reporting of Generator Real and Reactive
Power Capability and Synchronous Condenser Reactive Power Capability
Point

A

Voltage

Real Power

kV

Reactive Power

Comment

MW

Mvar

Sum multiple generators that are verified together
or are part of the same unit. Report individual unit
values separately whenever the verification
measurements were taken at the individual unit.
Individual values are required for units or
synchronous condensers > 20 MVA.

MW

Mvar

Sum multiple unit auxiliary transformers.

MW

Mvar

Sum multiple tertiary Loads, if any.

MW

Mvar

Sum multiple auxiliary and station service
transformers.

Identify calculated values, if any:
B

kV

Identify calculated values, if any:
C

kV

Identify calculated values, if any:
D

kV

Identify calculated values, if any:
E

kV

MW

Mvar

If multiple points of Interconnection, describe
these for accurate modeling; report points
individually (sum multiple auxiliary transformers).

F

kV

MW

Mvar

Net unit capability

Identify calculated values, if any:

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Standard MOD-025-2 — Verification and Data Reporting of Generator Real and Reactive
Power Capability and Synchronous Condenser Reactive Power Capability

MOD-025 -Attachment 2 (continued)
Verification Data
Provide data by unit or Facility, as appropriate
Data Type

Data Recorded

Last Verification
(Previous Data;
will be blank for
the initial
verification)

Gross Reactive Power Capability (*Mvar)
Aux Reactive Power (*Mvar)
Net Reactive Power Capability (*Mvar) equals Gross
Reactive Power Capability (*Mvar) minus Aux
Reactive Power connected at the same bus (*Mvar)
minus tertiary Reactive Power connected at the same
bus(*Mvar)
Gross Real Power Capability (*MW)
Aux Real Power (*MW)
Net Real Power Capability (*MW) equals Gross Real
Power Capability (*MW) minus Aux Real Power
connected at the same bus (*MW) minus tertiary Real
Power connected at the same bus(*MW)
* Note: Enter values at the end of the verification period.

GSU losses (only required if verification measurements
are taken on the high side of the GSU - Mvar)
Summary of Verification


Date of Verification _________,Verification Start Time _____, Verification End Time ______



Scheduled Voltage ______________



Transformer Voltage Ratio: GSU ______, Unit Aux _____, Station Aux _____, Other Aux
_____



Transformer Tap Setting: GSU ______, Unit Aux _____, Station Aux _____, Other Aux _____



Ambient conditions at the end of the verification period:
Air temperature: _________
Humidity: _________
Cooling water temperature: _________
Other data as applicable: _________
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Standard MOD-025-2 — Verification and Data Reporting of Generator Real and Reactive
Power Capability and Synchronous Condenser Reactive Power Capability


Generator hydrogen pressure at time of test (if applicable) _____________

Date that data shown in last verification column in table above was taken _____________
Remarks :

Note: If the verification value did not reach the thermal capability curve (D-curve), describe the reason.

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