Modeling of PGE Transformers€¦ · Modeling of transformers in various software platforms such as...

MODELING OF TRANSFORMERS IN WECC BASE CASES

For WECC SRWG By Rohan Chatterjee Electrical Engineer – Transmission Planning [email protected]

• Present Utility Practices • Problems with present practices • PowerWorld – Use of Transformer Base data for calculating System Base values. • PSLF – Use of Transformer Base data for calculating System Base values. • PSLF EPC file exported to PowerWorld & PTI RAW file format. • Examples Used – PGE 230/13.8kV GSU, Avista 230/115kV LTC transformer (at Boulder

substation). • Conclusions

T&D Planning 2

Present Utility Practices

Modeling of transformers in various software platforms such as PowerWorld, PSLF, and PSSE is crucial to the accuracy of powerflow solutions and the efficacy of planning/operations studies.

Present WECC base cases contain transformer data for most Northwest utilities in the System Base. Inconsistencies in how different utilities enter their transformer data in System Base.

PGE & Avista transmission planning have discussed the benefits of having a process in place to calculate transformer modeling data from the most accurate source, i.e test reports.

To accurately convert transformer data into the System Base, PowerWorld and PSLF require that the data be provided on the Transformer Base.

PSSE on the other hand, offers user flexibility to provide data in either the System Base or the Transformer Base.

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Problems With Present Practices

When provided with Transformer Base data PowerWorld, PSLF & PSSE convert it to the System Base.

When provided with data on the System Base (from the .epc file), PowerWorld may not necessarily do a 1:1 transformation of this data.

It calculates incorrect values for tap ratios, impedance & magnetizing admittance parameters on the System Base.

Similar to PW, when provided with data in the System Base (from the .epc file), PSLF calculates incorrect System Base values for the impedance & magnetizing admittance parameters.

It uses “FROM” & “TO” side input tap ratios and calculates incorrect values for transformer tap ratios on the System Base.

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Problems With Present Practices

When .EPC files are exported to .RAW file format, the impedance, nominal MVA and nominal kVs get stored as Transformer Base values by default.

If the .EPC file contains System Base data, much like PW & PSLF, this causes PSSE to calculate incorrect System base values for transformer tap ratios, impedance and magnetizing admittance parameters.

There is a need for a standardized manual for transformer modeling.

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When provided with data on the System Base, PSLF

calculates incorrect values for System Base transformer tap

ratios, impedance & mag. admittance parameters.

When provided with data on the System Base, PSSE

calculates incorrect values for System Base transformer tap

ratios, impedance & mag. admittance parameters.

When provided with data on the System Base, PW

calculates incorrect System Base values for tap ratios,

impedance & mag. admittance parameters.

.EPC files (WECC base cases) containing

System Base transformer data

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Same Issues regardless of the software

platform. This isn’t a software issue. The

user needs to ensure that the input data is in the Transformer Base.

PowerWorld

When provided with Transformer Base data PowerWorld converts it to the System Base.

Transformer Base model utilized by PowerWorld

System Base model utilized by PowerWorld

Equations used to calculate impedance and magnetizing admittance parameters on the System Base

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PGE GSU Test Report

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Schematic diagram of the no-load loss test: a) Test Setup, b) Bushings Connection, c) Equivalent circuit

Schematic diagram of the load loss test: a) Test Setup, b) Bushings Connection, c) Equivalent circuit

PGE GSU Nameplate

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Per Phase Impedance %

HV & LV Nominal kVs (on the Transformer/Winding base)

DETC settings on the HV side

Connection Information (Wye-Delta)

Incorrect Modeling

TRANSFORMER DATA ENTERED IN THE SYSTEM BASE

POWERWORLD SYSTEM BASE

Nominal MVA 100 Nominal MVA 100

Nominal kV (GSU High Side)

230 Nominal kV (GSU

High Side) 230

Nominal kV (GSU Low Side)

13.8 Nominal kV (GSU

Low Side) 13.8

R on System Base 0.00213 R 0.00195

X on System Base 0.09544 X 0.08732

Mag B on Sys. Base -0.00120 Mag B -0.00120

Mag G on Sys. Base 0.00504 Mag G 0.00504 Transformer Data (from epc file) Is Entered In the System Base

If the impedance & magnetizing admittance parameters are entered in the System Base, their transformation will not result in identical values, because of the tap ratio on the “TO” side (as circled in red below).


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Correct Modeling

Transformer Base System Base


Nominal kV (GSU High Side) 241.5 Nominal kV (GSU High Side) 230

Nominal kV (GSU Low Side) 13.2 Nominal kV (GSU Low Side) 13.8

R on XF Base 0.00303 R 0.00213

X on XF Base 0.1356 X 0.09544

Mag B on XF Base -0.00092 Mag B -0.0012

Mag G on XF Base 0.00388 Mag G 0.00504

GSU Test Report

GSU Nameplate

If the impedance & magnetizing admittance parameters are entered in the Transformer Base, they will be correctly transformed to the corresponding System Base values.

Transformer Data Is In the Transformer Base

It is therefore critical that the impedance and magnetizing admittance parameters be entered into

PowerWorld in the Transformer Base.

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Equations used to calculate the transformer tap ratio on the System Base

If the “FROM” & “TO” side tap ratios are entered in the System Base, it ends up calculating incorrect System Base values for transformer tap ratio.

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𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻 = 𝟏𝟏

𝑭𝑭𝑭𝑭𝑭𝑭𝑭𝑭𝑭𝑭𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑭𝑭𝑻𝑻𝑻𝑻∗

𝑵𝑵𝑭𝑭𝑵𝑵𝑵𝑵𝑵𝑵𝑻𝑻𝑭𝑭𝑺𝑺𝑺𝑺𝑺𝑺𝑵𝑵𝑭𝑭𝑵𝑵𝑵𝑵𝑵𝑵𝑻𝑻𝑭𝑭𝑻𝑻𝑻𝑻

∗𝑵𝑵𝑭𝑭𝑵𝑵𝑵𝑵𝑵𝑵𝑭𝑭𝑵𝑵𝑭𝑭𝑵𝑵𝑻𝑻𝑻𝑻

𝑵𝑵𝑭𝑭𝑵𝑵𝑵𝑵𝑵𝑵𝑭𝑭𝑵𝑵𝑭𝑭𝑵𝑵𝑺𝑺𝑺𝑺𝑺𝑺

∴ 𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻 = 𝟏𝟏.𝟎𝟎

𝟎𝟎.𝟗𝟗𝟗𝟗𝟗𝟗𝟗𝟗∗

𝟏𝟏𝟏𝟏.𝟖𝟖𝟏𝟏𝟏𝟏.𝟖𝟖

∗𝟐𝟐𝟏𝟏𝟎𝟎𝟐𝟐𝟏𝟏𝟎𝟎

= 𝟏𝟏.𝟎𝟎𝟎𝟎𝟗𝟗𝟎𝟎𝟖𝟖

𝑻𝑻𝑻𝑻𝑻𝑻𝑺𝑺𝑺𝑺𝑺𝑺𝑻𝑻𝑺𝑺𝑻𝑻 = 𝑪𝑪𝑻𝑻𝑵𝑵𝑵𝑵𝑭𝑭𝑪𝑪𝑻𝑻 𝑻𝑻𝑻𝑻𝑻𝑻 𝑻𝑻𝑻𝑻𝑻𝑻𝑭𝑭𝑭𝑭𝑻𝑻𝑻𝑻 + 𝑭𝑭𝑭𝑭𝑭𝑭𝑭𝑭𝑭𝑭𝑻𝑻𝑻𝑻𝑻𝑻𝑭𝑭𝑵𝑵𝑭𝑭𝑵𝑵𝑻𝑻𝑻𝑻 − 𝟏𝟏 ∗ 𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻

= 𝟏𝟏.𝟎𝟎𝟐𝟐𝟏𝟏𝟗𝟗𝟎𝟎𝟗𝟗+ 𝟏𝟏.𝟎𝟎 − 𝟏𝟏.𝟎𝟎 ∗ 𝟏𝟏.𝟎𝟎𝟎𝟎𝟗𝟗𝟎𝟎𝟖𝟖 = 𝟏𝟏.𝟎𝟎𝟎𝟎𝟎𝟎𝟎𝟎𝟎𝟎

These are values calculated by PowerWorld in the System Base (i.e 100 MVA, 230kV & 13.8kV).

If the “FROM” & “TO” side tap ratios are entered in the Transformer Base, PowerWorld correctly calculates the System Base transformer tap ratio.

All calculations have been documented in the manual on the modeling of PGE

transformers.

It is therefore critical that “FROM” & “TO” side tap ratios be entered in


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𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻 = 𝟏𝟏

𝑭𝑭𝑭𝑭𝑭𝑭𝑭𝑭𝑭𝑭𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑭𝑭𝑻𝑻𝑻𝑻∗

𝑵𝑵𝑭𝑭𝑵𝑵𝑵𝑵𝑵𝑵𝑻𝑻𝑭𝑭𝑺𝑺𝑺𝑺𝑺𝑺𝑵𝑵𝑭𝑭𝑵𝑵𝑵𝑵𝑵𝑵𝑻𝑻𝑭𝑭𝑻𝑻𝑻𝑻

∗𝑵𝑵𝑭𝑭𝑵𝑵𝑵𝑵𝑵𝑵𝑭𝑭𝑵𝑵𝑭𝑭𝑵𝑵𝑻𝑻𝑻𝑻

𝑵𝑵𝑭𝑭𝑵𝑵𝑵𝑵𝑵𝑵𝑭𝑭𝑵𝑵𝑭𝑭𝑵𝑵𝑺𝑺𝑺𝑺𝑺𝑺

∴ 𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻 = 𝟏𝟏.𝟎𝟎𝟏𝟏.𝟎𝟎

∗𝟏𝟏𝟏𝟏.𝟖𝟖𝟏𝟏𝟏𝟏.𝟐𝟐

∗𝟐𝟐𝟎𝟎𝟏𝟏.𝟗𝟗𝟐𝟐𝟏𝟏𝟎𝟎

= 𝟏𝟏.𝟎𝟎𝟗𝟗𝟎𝟎𝟎𝟎

𝑻𝑻𝑻𝑻𝑻𝑻𝑺𝑺𝑺𝑺𝑺𝑺𝑻𝑻𝑺𝑺𝑻𝑻 = 𝑪𝑪𝑻𝑻𝑵𝑵𝑵𝑵𝑭𝑭𝑪𝑪𝑻𝑻 𝑻𝑻𝑻𝑻𝑻𝑻 𝑻𝑻𝑻𝑻𝑻𝑻𝑭𝑭𝑭𝑭𝑻𝑻𝑻𝑻 + 𝑭𝑭𝑭𝑭𝑭𝑭𝑭𝑭𝑭𝑭𝑻𝑻𝑻𝑻𝑻𝑻𝑭𝑭𝑵𝑵𝑭𝑭𝑵𝑵𝑻𝑻𝑻𝑻 − 𝟏𝟏 ∗ 𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻

= 𝟏𝟏+ 𝟎𝟎.𝟗𝟗𝟎𝟎𝟎𝟎𝟗𝟗𝟗𝟗− 𝟏𝟏 ∗ 𝟏𝟏.𝟎𝟎𝟗𝟗𝟎𝟎𝟎𝟎 = 𝟏𝟏.𝟎𝟎𝟎𝟎𝟎𝟎𝟐𝟐𝟏𝟏

GE PSLF When provided with Transformer Base input data PSLF converts it to the System Base.

When provided with System Base input data, the tap ratios, impedance & magnetizing admittance parameters are calculated incorrectly in the System Base.

Please note that PSLF requires that the Nominal MVA (i.e tbase) and the data items tapp, tapfp, tapfs, vnomp and vnoms be entered on the Transformer Base.

The conversion of the data from the individual transformer bases to a common system base for network solutions is handled internally by PSLF.

Transformer Base model utilized by PSLF

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Round Butte VR3

* From bus 43483 ROUNDB N 230.00 R from-tert pu 0.000000 * Variable V tap pu 1.023910

* To bus 43490 ROUND B3 13.80 X from-tert pu 0.000000 * Step size pu(deg) 0.000000

* Circuit Id 1 R to-tert pu 0.000000 Max var. tap pu(deg) 0.000000

Project Id 0 X to-tert pu 0.000000 Min var. tap pu(deg) 0.000000

* Trans Status 1 *From wind nom volt Kv 230.0 Max Cont V(P) pu (MW) 0.000000

Normal Status 0 *To wind nom volt Kv 13.80 Min Cont V(P) pu (MW) 0.000000

* Tap control type 1 *Tert wind nom volt Kv

0.000000 G-Core loss pu 0.005040

* From-To Base MVA 100.000000 * From fixed tap pu 1.000000 B-Magnetizing pu -0.001200

R from-to pu 0.002130 * To fixed tap pu 0.956520

* X from-to pu 0.09544 * Tert fixed tap pu 1.000000

The table shows the information pertaining to nominal MVA, nominal kV, impedance and admittance parameters in an epc file. (all in System Base).

𝑻𝑻𝑻𝑻𝑻𝑻 𝑻𝑻𝑻𝑻𝑻𝑻𝑭𝑭𝑭𝑭𝑺𝑺𝑺𝑺𝑺𝑺𝑻𝑻𝑭𝑭𝑵𝑵 𝑩𝑩𝑻𝑻𝑺𝑺𝑭𝑭 = 𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻 + 𝑻𝑻𝑻𝑻𝑻𝑻𝒕𝒕𝑻𝑻 − 𝟏𝟏

𝑻𝑻𝑻𝑻𝑻𝑻𝒕𝒕𝑺𝑺∗

𝑻𝑻𝑭𝑭 𝒌𝒌𝑵𝑵𝑪𝑪𝑭𝑭𝑵𝑵𝑺𝑺𝑺𝑺𝑺𝑺

𝑻𝑻𝑭𝑭 𝒌𝒌𝑵𝑵𝑪𝑪𝑭𝑭𝑵𝑵𝑻𝑻𝑻𝑻∗

𝑭𝑭𝑵𝑵𝑭𝑭𝑵𝑵 𝒌𝒌𝑵𝑵𝑪𝑪𝑭𝑭𝑵𝑵𝑻𝑻𝑻𝑻

𝑭𝑭𝑵𝑵𝑭𝑭𝑵𝑵 𝒌𝒌𝑵𝑵𝑪𝑪𝑭𝑭𝑵𝑵𝑺𝑺𝑺𝑺𝑺𝑺;

𝑻𝑻𝑻𝑻𝑻𝑻 𝑻𝑻𝑻𝑻𝑻𝑻𝑭𝑭𝑭𝑭𝑺𝑺𝑺𝑺𝑺𝑺𝑻𝑻𝑭𝑭𝑵𝑵 𝑩𝑩𝑻𝑻𝑺𝑺𝑭𝑭 = 𝟏𝟏.𝟎𝟎𝟐𝟐𝟏𝟏𝟗𝟗𝟏𝟏𝟎𝟎 + 𝟏𝟏 − 𝟏𝟏

𝟎𝟎.𝟗𝟗𝟗𝟗𝟗𝟗𝟗𝟗∗

𝟏𝟏𝟏𝟏.𝟖𝟖𝟏𝟏𝟏𝟏.𝟖𝟖

∗𝟐𝟐𝟏𝟏𝟎𝟎𝟐𝟐𝟏𝟏𝟎𝟎

= 𝟏𝟏.𝟎𝟎𝟎𝟎𝟎𝟎𝟎𝟎𝟎𝟎 (𝐈𝐈𝐈𝐈𝐈𝐈𝐈𝐈𝐈𝐈𝐈𝐈𝐈𝐈𝐈𝐈𝐈𝐈)

If the “FROM” & “TO” side tap ratios are entered in the System Base, it results in incorrect System Base values for transformer tap ratio.

𝑶𝑶𝒕𝒕𝒕𝒕 − 𝑵𝑵𝑭𝑭𝑵𝑵𝑭𝑭𝑪𝑪𝑻𝑻𝑻𝑻 𝑻𝑻𝑻𝑻𝑻𝑻 𝑻𝑻𝑻𝑻𝑻𝑻𝑭𝑭𝑭𝑭𝑺𝑺𝑺𝑺𝑺𝑺𝑻𝑻𝑭𝑭𝑵𝑵 𝑩𝑩𝑻𝑻𝑺𝑺𝑭𝑭 = 𝒌𝒌𝑵𝑵𝑳𝑳𝑳𝑳, 𝑵𝑵𝑻𝑻𝑵𝑵𝑭𝑭𝑻𝑻𝑽𝑽𝑻𝑻𝑭𝑭/𝑭𝑭𝑭𝑭𝑭𝑭𝑭𝑭𝑭𝑭 𝑻𝑻𝑻𝑻𝑻𝑻 𝑷𝑷𝑭𝑭𝑺𝑺𝑻𝑻𝑭𝑭𝑭𝑭𝑪𝑪

𝒌𝒌𝑵𝑵𝑳𝑳𝑳𝑳, 𝑺𝑺𝑺𝑺𝑺𝑺𝑻𝑻𝑭𝑭𝑵𝑵 𝑵𝑵𝑭𝑭𝑵𝑵𝑭𝑭𝑪𝑪𝑻𝑻𝑻𝑻�

𝒌𝒌𝑵𝑵𝑳𝑳𝑳𝑳, 𝑭𝑭𝑭𝑭𝑭𝑭𝑭𝑭𝑭𝑭 𝑻𝑻𝑻𝑻𝑻𝑻 𝑷𝑷𝑭𝑭𝑺𝑺𝑭𝑭𝑻𝑻𝑭𝑭𝑭𝑭𝑪𝑪𝒌𝒌𝑵𝑵𝑳𝑳𝑳𝑳, 𝑺𝑺𝑺𝑺𝑺𝑺𝑻𝑻𝑭𝑭𝑵𝑵 𝑵𝑵𝑭𝑭𝑵𝑵𝑭𝑭𝑪𝑪𝑻𝑻𝑻𝑻�

= 𝟐𝟐𝟏𝟏𝟗𝟗.𝟎𝟎𝟗𝟗𝟎𝟎

𝟐𝟐𝟏𝟏𝟎𝟎�𝟏𝟏𝟏𝟏.𝟐𝟐

𝟏𝟏𝟏𝟏.𝟖𝟖�= 𝟏𝟏.𝟎𝟎𝟎𝟎𝟐𝟐𝟏𝟏 (Correct)

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* From bus 43483 ROUNDB N 230.00 R from-tert pu 0.000000 * Variable V tap pu 1.000

* To bus 43490 ROUND B3 13.80 X from-tert pu 0.000000 * Step size pu(deg) 0.000000

* Circuit Id 1 R to-tert pu 0.000000 Max var. tap pu(deg) 0.000000

Project Id 0 X to-tert pu 0.000000 Min var. tap pu(deg) 0.000000

* Trans Status 1 *From wind nom volt Kv

241.50 Max Cont V(P) pu (MW) 0.00

Normal Status 0 *To wind nom volt Kv 13.20 Min Cont V(P) pu (MW) 0.000000

* Tap control type 1 *Tert wind nom volt Kv

0.000000 G-Core loss pu 0.000388

* From-To Base MVA 130.000000 * From fixed tap pu 0.974950 B-Magnetizing pu -0.000922

R from-to pu 0.003026 * To fixed tap pu 1.00000 * X from-to pu 0.135601 * Tert fixed tap pu 1.000000

Using the input Transformer Base data, these are values calculated by PowerWorld in the System Base.

The table shows the information pertaining to nominal MVA, nominal kV, impedance and admittance parameters in an epc file for Round Butte VR3. (all in Transformer Base).

𝑻𝑻𝑻𝑻𝑻𝑻 𝑻𝑻𝑻𝑻𝑻𝑻𝑭𝑭𝑭𝑭𝑺𝑺𝑺𝑺𝑺𝑺𝑻𝑻𝑭𝑭𝑵𝑵 𝑽𝑽𝑻𝑻𝑺𝑺𝑭𝑭 = 𝟏𝟏 + 𝟎𝟎.𝟗𝟗𝟎𝟎𝟎𝟎𝟗𝟗𝟗𝟗𝟎𝟎 − 𝟏𝟏

𝟏𝟏.𝟎𝟎𝟎𝟎𝟎𝟎𝟎𝟎∗

𝟏𝟏𝟏𝟏.𝟖𝟖𝟏𝟏𝟏𝟏.𝟐𝟐

∗𝟐𝟐𝟎𝟎𝟏𝟏.𝟗𝟗𝟐𝟐𝟏𝟏𝟎𝟎

= 𝟏𝟏.𝟎𝟎𝟎𝟎𝟎𝟎𝟐𝟐𝟏𝟏

If the “FROM” & “TO” side tap ratios are entered in the Transformer Base, it results in correct System Base values for transformer tap ratio.

When this epc file is opened in PowerWorld, we see the input information as it should be on the Transformer Base.

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The Nominal KV, impedance parameters and Nominal MVA are stored in the Transformer

Base. I/O code 2 in PSSE parlance.

The magnetizing admittance parameters are stored in the System Base. I/O code 1 in

PSSE parlance.

When the epc file containing the data in the System Base is exported to the Siemens PSSE raw file format, it is stored in the raw file in the Transformer Base. This creates the following issues; • The FROM & TO winding nominal kVs and the

winding nominal MVA are set equal to their respective nominal System Base values.

• The System Base transformer tap ratio is calculated incorrectly.

• The System Base values for impedance and magnetizing admittance parameters are calculated incorrectly.

17 T&D Planning

𝑻𝑻𝑺𝑺𝑺𝑺𝑺𝑺𝑻𝑻𝑭𝑭𝑵𝑵 𝑩𝑩𝑻𝑻𝑺𝑺𝑭𝑭 =𝑻𝑻𝑭𝑭𝑻𝑻𝒋𝒋

∗𝑵𝑵𝑽𝑽𝑻𝑻𝑺𝑺𝑭𝑭 𝑭𝑭 𝑪𝑪𝑻𝑻𝑵𝑵𝑭𝑭𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑭𝑭

𝑵𝑵𝑽𝑽𝑻𝑻𝑺𝑺𝑭𝑭 𝑭𝑭 𝑭𝑭𝑭𝑭𝑺𝑺𝑭𝑭𝑵𝑵𝑭𝑭𝑭𝑭∗

𝑵𝑵𝑽𝑽𝑻𝑻𝑺𝑺𝑭𝑭 𝒋𝒋 𝑭𝑭𝑭𝑭𝑺𝑺𝑭𝑭𝑵𝑵𝑭𝑭𝑭𝑭

𝑵𝑵𝑽𝑽𝑻𝑻𝑺𝑺𝑭𝑭 𝒋𝒋 𝑪𝑪𝑻𝑻𝑵𝑵𝑭𝑭𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑭𝑭=

𝟏𝟏.𝟎𝟎𝟐𝟐𝟏𝟏𝟗𝟗𝟎𝟎𝟗𝟗𝟎𝟎.𝟗𝟗𝟗𝟗𝟗𝟗𝟗𝟗

∗𝟐𝟐𝟏𝟏𝟎𝟎𝟐𝟐𝟏𝟏𝟎𝟎

∗𝟏𝟏𝟏𝟏.𝟖𝟖𝟏𝟏𝟏𝟏.𝟖𝟖

= 𝟏𝟏.𝟎𝟎𝟎𝟎𝟎𝟎𝟎𝟎 (𝑭𝑭𝑪𝑪𝒊𝒊𝑭𝑭𝑵𝑵𝑵𝑵𝑭𝑭𝒊𝒊𝑻𝑻)

𝑻𝑻𝑺𝑺𝑺𝑺𝑺𝑺𝑻𝑻𝑭𝑭𝑵𝑵 𝑩𝑩𝑻𝑻𝑺𝑺𝑭𝑭 = 𝑻𝑻𝒋𝒋𝟐𝟐 ∗ 𝑻𝑻𝑻𝑻𝑵𝑵𝑻𝑻𝑪𝑪𝑺𝑺𝒕𝒕𝑭𝑭𝑵𝑵𝑵𝑵𝑭𝑭𝑵𝑵 𝑩𝑩𝑻𝑻𝑺𝑺𝑭𝑭 ∗

𝑵𝑵𝑽𝑽𝑻𝑻𝑺𝑺𝑭𝑭 𝒋𝒋 𝑪𝑪𝑻𝑻𝑵𝑵𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑭𝑭

𝑵𝑵𝑽𝑽𝑻𝑻𝑺𝑺𝑭𝑭 𝑭𝑭 𝑭𝑭𝑭𝑭𝑺𝑺𝑭𝑭𝑵𝑵𝑭𝑭𝑭𝑭

𝟐𝟐

∗𝑻𝑻𝑵𝑵𝑴𝑴𝑭𝑭𝑭𝑭𝑺𝑺𝑭𝑭𝑵𝑵𝑭𝑭𝑭𝑭𝑻𝑻𝑵𝑵𝑴𝑴𝑪𝑪𝑻𝑻𝑵𝑵𝑭𝑭𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑭𝑭

= 𝟎𝟎.𝟗𝟗𝟗𝟗𝟗𝟗𝟗𝟗 𝟐𝟐∗ 𝟎𝟎.𝟎𝟎𝟎𝟎𝟏𝟏𝟗𝟗𝟐𝟐𝟎𝟎 ∗𝟏𝟏𝟏𝟏.𝟖𝟖𝟏𝟏𝟏𝟏.𝟖𝟖

𝟐𝟐

∗𝟏𝟏𝟎𝟎𝟎𝟎.𝟎𝟎𝟏𝟏𝟎𝟎𝟎𝟎.𝟎𝟎

= 𝟎𝟎.𝟎𝟎𝟎𝟎𝟏𝟏𝟐𝟐𝟐𝟐𝟎𝟎 𝑻𝑻.𝑻𝑻 (𝑭𝑭𝑪𝑪𝒊𝒊𝑭𝑭𝑵𝑵𝑵𝑵𝑭𝑭𝒊𝒊𝑻𝑻)

PSSE Two-Winding Transformer Circuit

The Nominal KV, impedance parameters and Nominal MVA are stored in the Transformer

Base. I/O code 2 in PSSE parlance.

The magnetizing admittance parameters are stored in the System Base. I/O code 1 in

PSSE parlance.

When the epc file containing the data in the Transformer Base is exported to the Siemens PSSE raw file format, it is stored correctly in the raw file in the Transformer Base. This results in; • The FROM & TO winding nominal kVs and the

winding nominal MVA are set equal to their respective nominal Transformer Base values.

• The System Base transformer tap ratio is calculated correctly.

• The System Base values for impedance and magnetizing admittance parameters are calculated correctly.

18 T&D Planning

𝑻𝑻𝑺𝑺𝑺𝑺𝑺𝑺𝑻𝑻𝑭𝑭𝑵𝑵 𝑩𝑩𝑻𝑻𝑺𝑺𝑭𝑭 =𝑻𝑻𝑭𝑭𝑻𝑻𝒋𝒋

∗𝑵𝑵𝑽𝑽𝑻𝑻𝑺𝑺𝑭𝑭 𝑭𝑭 𝑪𝑪𝑻𝑻𝑵𝑵𝑭𝑭𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑭𝑭

𝑵𝑵𝑽𝑽𝑻𝑻𝑺𝑺𝑭𝑭 𝑭𝑭 𝑭𝑭𝑭𝑭𝑺𝑺𝑭𝑭𝑵𝑵𝑭𝑭𝑭𝑭∗

𝑵𝑵𝑽𝑽𝑻𝑻𝑺𝑺𝑭𝑭 𝒋𝒋 𝑭𝑭𝑭𝑭𝑺𝑺𝑭𝑭𝑵𝑵𝑭𝑭𝑭𝑭

𝑵𝑵𝑽𝑽𝑻𝑻𝑺𝑺𝑭𝑭 𝒋𝒋 𝑪𝑪𝑻𝑻𝑵𝑵𝑭𝑭𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑭𝑭=

𝟎𝟎.𝟗𝟗𝟎𝟎𝟎𝟎𝟗𝟗𝟗𝟗𝟎𝟎𝟏𝟏.𝟎𝟎

∗𝟐𝟐𝟎𝟎𝟏𝟏.𝟗𝟗𝟐𝟐𝟏𝟏𝟎𝟎

∗𝟏𝟏𝟏𝟏.𝟖𝟖𝟏𝟏𝟏𝟏.𝟐𝟐

= 𝟏𝟏.𝟎𝟎𝟎𝟎𝟐𝟐𝟏𝟏 (𝒊𝒊𝑭𝑭𝑵𝑵𝑵𝑵𝑭𝑭𝒊𝒊𝑻𝑻)

𝑻𝑻𝑺𝑺𝑺𝑺𝑺𝑺𝑻𝑻𝑭𝑭𝑵𝑵 𝑩𝑩𝑻𝑻𝑺𝑺𝑭𝑭 = 𝑻𝑻𝒋𝒋𝟐𝟐 ∗ 𝑻𝑻𝑻𝑻𝑵𝑵𝑻𝑻𝑪𝑪𝑺𝑺𝒕𝒕𝑭𝑭𝑵𝑵𝑵𝑵𝑭𝑭𝑵𝑵 𝑩𝑩𝑻𝑻𝑺𝑺𝑭𝑭 ∗

𝑵𝑵𝑽𝑽𝑻𝑻𝑺𝑺𝑭𝑭 𝒋𝒋 𝑪𝑪𝑻𝑻𝑵𝑵𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑭𝑭

𝑵𝑵𝑽𝑽𝑻𝑻𝑺𝑺𝑭𝑭 𝑭𝑭 𝑭𝑭𝑭𝑭𝑺𝑺𝑭𝑭𝑵𝑵𝑭𝑭𝑭𝑭

𝟐𝟐

∗𝑻𝑻𝑵𝑵𝑴𝑴𝑭𝑭𝑭𝑭𝑺𝑺𝑭𝑭𝑵𝑵𝑭𝑭𝑭𝑭𝑻𝑻𝑵𝑵𝑴𝑴𝑪𝑪𝑻𝑻𝑵𝑵𝑭𝑭𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑭𝑭

= 𝟏𝟏.𝟎𝟎 𝟐𝟐∗ 𝟎𝟎.𝟎𝟎𝟎𝟎𝟏𝟏𝟎𝟎𝟐𝟐𝟗𝟗 ∗𝟏𝟏𝟏𝟏.𝟐𝟐𝟏𝟏𝟏𝟏.𝟖𝟖

𝟐𝟐

∗𝟏𝟏𝟎𝟎𝟎𝟎.𝟎𝟎𝟏𝟏𝟏𝟏𝟎𝟎.𝟎𝟎

= 𝟎𝟎.𝟎𝟎𝟎𝟎𝟐𝟐𝟏𝟏𝟏𝟏𝟎𝟎 𝑻𝑻.𝑻𝑻 (𝒊𝒊𝑭𝑭𝑵𝑵𝑵𝑵𝑭𝑭𝒊𝒊𝑻𝑻)

PSSE Two-Winding Transformer Circuit

Avista Boulder Substation

19 T&D Planning

Avista Boulder Substation

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Avista Boulder LTC Transformer Test Report

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Schematic diagram of load losses test: a) Test Setup, b) Bushings Connection, c) Equivalent circuit

Schematic diagram of no-load losses test: a) Test Setup, b) Bushings Connection, c) Equivalent circuit

Avista Boulder LTC Transformer Nameplate Information

22 T&D Planning

Per Phase Impedance %

HV & LV Nominal kVs (on the Transformer/Winding base)

LTC/NLTC settings on the HV/LV sides

Wye-Wye primary-secondary connection with delta connected tertiary winding

Boulder (Incorrect Modeling)

TRANSFORMER DATA ENTERED IN THE SYSTEM BASE

POWERWORLD SYSTEM BASE


Nominal kV (GSU High Side)

230 Nominal kV (GSU

High Side) 230

Nominal kV (GSU Low Side)

115 Nominal kV (GSU

Low Side) 115

R on System Base 0.000447 R 0.000451

X on System Base 0.028486 X 0.028734

Mag B on Sys. Base 0 Mag B 0

Mag G on Sys. Base 0 Mag G 0 Transformer Data (from aux file) Is Entered In the System Base

If the impedance & magnetizing admittance parameters are entered in the System Base, their transformation will not result in identical values, because of the tap ratio on the “TO” side (as circled in red below).


23 T&D Planning

Boulder (Correct Modeling)

Transformer Base System Base


Nominal kV (GSU High Side) 236.5 Nominal kV (GSU High Side) 230

Nominal kV (GSU Low Side) 112.75 Nominal kV (GSU Low Side) 115

R on XF Base 0.001108 R 0.000447

X on XF Base 0.070591 X 0.028486

Mag B on XF Base 0 Mag B 0

Mag G on XF Base 0 Mag G 0

Boulder LTC Test Report

Boulder LTC Nameplate Information

If the impedance & magnetizing admittance parameters are entered in the Transformer Base, they will be correctly transformed to the corresponding System Base values.

Transformer Data Is In the Transformer Base

It is therefore critical that the impedance and magnetizing admittance parameters be entered into


24 T&D Planning

Conclusions

New PGE practice - All transformer data required for the ColumbiaGrid/WECC base case development process will be provided by PGE in the Transformer Base.

EPC files containing Transformer Base data can be faithfully exported to the PowerWorld and PSSE platforms without any data skews or distortions.

Providing Transformer Base input parameters to the software platforms enables their accurate internal conversion to the corresponding System Base parameters.

PGE & Avista agree & strongly recommend that utilities submit transformer data in the Transformer Base for the WECC base case development process. This will result in WECC-wide uniformity in transformer modeling for system planning studies.

Update the Data Preparation Manual to have utilities provide their transformer data only in the Transformer Base.

25 T&D Planning

Modeling of PGE Transformers€¦ · Modeling of transformers in various software platforms such as...

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