GE Grid Solutions Multilin 9450 - 7.2 EPM 9450;9650 Meters Transformer Loss Compensation

7–4 EPM 9450/9650 ADVANCED POWER QUALITY METERING SYSTEM – INSTRUCTION MANUAL
EPM 9450/9650 METER'S TRANSFORMER LOSS COMPENSATION CHAPTER 7: TRANSFORMER LOSS COMPENSATION
7.2 EPM 9450/9650 Meter's Transformer Loss Compensation
The EPM 9450/9650 meter provides compensation for active and reactive power quantities
by performing numerical calculations. The factors used in these calculations are derived
either:
• By clicking the TLC Calculator button on the Transformer Loss screen of the Device
Profile, to open the GE Loss Compensation Calculator in Microsoft Excel
• By figuring the values from the worksheet shown here and in the GE
Communicator Instruction Manual.
Either way, you enter the derived values into the GE Communicator software through the
Device Profile Transformer and Line Loss Compensation screen.
The GE Communicator software allows you to enable Transformer Loss Compensation for
Losses due to Copper and Iron, individually or simultaneously. Losses can either be added
to or subtracted from measured readings. Refer to the GE Communicator Instruction
Manual for instructions.
Loss compensation values must be calculated based on the meter installation. As a result,
transformer loss values must be normalized to the meter by converting the base voltage
and current and taking into account the number of elements used in the metering
installation. For three-element meters, the installation must be normalized to the phase-
to-neutral voltage and the phase current; in two-element meters the installation must be
normalized to the phase-to-phase voltage and the phase current. This process is
described in the following sections.
7.2.1 Loss Compensation in Three Element Installations
Loss compensation is based on the loss and impedance values provided on the
transformer manufacturer's test report. A typical test report will include at least the
following information:
• Manufacturer
• Unit Serial Number
• Transformer MVA Rating (Self-Cooled)
• Test Voltage
• No Load Loss Watts
• Load Loss Watts (or Full Load Loss Watts)
• % Exciting Current @ 100% voltage
• % Impedance
The transformer MVA rating is generally the lowest MVA rating (the self-cooled or OA rating)
of the transformer winding. The test voltage is generally the nominal voltage of the
secondary or low voltage winding. For three-phase transformers these values will typically
be the three-phase rating and the phase-to-phase voltage. All of the test measurements
are based on these two numbers. Part of the process of calculating the loss compensation
percentages is converting the transformer loss values based on the transformer ratings to
the base used by the meter.