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Transformer Loss Compensation

Transformer Loss Compensation. Presented by: Mike Coit. Why Use TLC?. Billing point is different than metering point. Impractical to meter at billing point. Too expensive (High Voltage vs. Low Voltage). Inaccessible.

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Transformer Loss Compensation

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  1. Transformer Loss Compensation Presented by: Mike Coit

  2. Why Use TLC? • Billing point is different than metering point. • Impractical to meter at billing point. • Too expensive (High Voltage vs. Low Voltage). • Inaccessible. • Low voltage service changed to high voltage service, existing metering to be used. Transformer Loss Compensation

  3. TLC Objectives • Determine unmetered losses between billing point and metering point. • Add (subtract) the unmetered losses to (from) the metered quantities. • Energy (kWh) and Quadergy (kvarh) may both be compensated for at the metering point. Transformer Loss Compensation

  4. Loss Compensation Methods • Transformer Loss Meter • A separate meter with special V2 and I2 stators • Transformer Loss Compensator • Losses added into standard watthour meter registration using a specialized compensator. • Resistor Method • A variation of above, using resistors for no-load compensation and calibration adjustments for load loss compensation. • Solid State Meter with TLC capabilities Transformer Loss Compensation

  5. Transformer Losses • Hysteresis (no-load loss) • Energy expended from changing intensity and direction of magnetic flux in transformer. • Eddy Currents (no-load loss) • Energy expended by circulating currents induced within the core material • Load Currents (load loss) • Energy expended by load current in transformer windings having some resistance (I2R losses). • Treat Line Loss compensation (if needed) as if it’s part of transformer load losses. Transformer Loss Compensation

  6. Transformer Loss Modeling • No-load loss watts proportional to V2 • Load loss watts proportional to I2 • No-load loss vars proportional to V4 • Load loss vars proportional to I2 • Manufactures supply watts loss test results • Loss vars are derived from the mfg. data. Transformer Loss Compensation

  7. Rated kVA* L-N Voltage Line Current VTR CTR No load loss watts* (Iron Losses) Load loss watts* (Copper Losses) % Excitation Current % Impedance Line Losses* (optional) Data required for kV2 TLC *Per element values Transformer Loss Compensation

  8. TLC Values calculated for kV2 • Secondary Conductance, G • G Elem = (LFE Elem watts * VTR / CTR) / (Volts L-N)2 • Secondary Resistance, R • R Elem = ((LCU Elem watts + LL Elem watts)* CTR / VTR) / (Amps Line)2 • Secondary Susceptance, B • B Elem = (LFE Elem vars * (VTR)3 / CTR) / (Volts L-N)4 • Secondary Reactance, X • X Elem = (LCU Elem vars * CTR / VTR) / (Amps Line)2 Transformer Loss Compensation

  9. How TLC is performed in the kV2 • Every momentary interval… • Per element losses are calculated • Example: LFE Elem wh = G Elem * VL-N2h • Losses are added to or subtracted from load measurements • Adjusted values are then processed normally (energy and quadergy is accumulated, demands are calculated, etc.) Transformer Loss Compensation

  10. Testing a TLC enabled kV2 • Calibration LED is unaffected by TLC • TLC may be disabled to facilitate testing using displayed values or PI outputs • Check no load losses by applying expected voltage only (no current) to the meter • Note that expected voltage may differ from typical test voltages • Load losses can be compared after subtracting out the measured load and no-load losses from the metered value. Transformer Loss Compensation

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