Electro-Voice 250, 1252 operation manual Loss Compensation in Three Element Installations

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.

Correct calculation of loss compensation also requires knowledge of the meter installation. In order to calculate the loss compensation settings you will need the following information regarding the meter and the installation:

•Number of meter elements

•Potential Transformer Ratio (PTR)

•Current Transformer Ratio (CTR)

•Meter Base Voltage

•Meter Base Current

This section is limited to application of Nexus meters to three-element metering installations. As a result, we know that:

•Number of metering elements = 3

•Meter Base Voltage = 120 Volts

•Meter Base Current = 5 amps

The loss compensation values can be calculated by clicking the TLC Calculator button on the Transformer Loss screen of the Nexus Device Profile (MS Excel Spreadsheet) or by completing the worksheet “Three Element Loss Compensation Worksheet” below. In order to activate the Excel Spreadsheet, you must have MS Excel installed on your computer.

NOTE: A copy of the Excel Spreadsheet with Example Numbers can be found in Appendix A of this manual.

Electro Industries/GaugeTech Doc # E107706 V1.25 7-4