A single meter cannot measure the losses in a transformer or transmission line directly. It can however, include computational corrections to calculate the losses and add or subtract those losses to the power flow measured at the meter location. This is the method used for loss compensation in the Nexus meter.
The computational corrections used for transformer and transmission line loss compensation are similar. Generically,
In the Nexus meter, Loss Compensation is a technique that computationally accounts for active and reactive power losses. The meter calculations are based on the formulas below. These equations describe the amount of active (Watts) and reactive (VARs) power lost due to both iron and copper effects (reflected to the secondary of the instrument transformers).
Total Secondary Watt Loss =
(((Measured Voltage/Cal point Voltage)2 x %LWFE) + ((Measured Current/Cal Point Current)2 x %LWCU)) x
Total Secondary VAR Loss =
(((Measured Voltage/Cal point Voltage)4 x %LVFE) + ((Measured Current/Cal Point Current)2 x %LVCU)) x
The Values for %LWFE, %LWCU, %LVFE, %LVCU are derived from the transformer and meter information, as demonstrated in following sections.
The calculated loss compensation values are added to or subtracted from the measured Watts and VARs. The selection of adding or subtracting losses is made through the meter profile when programming the meter. The meter uses the combination of the add/subtract setting and the directional definition of power flow (also in the profile) to determine how to handle the losses. Losses will be "added to" or "subtracted from" (depending on whether add or subtract is selected) the Received Power flow. For example, if losses are set to "Add to" and received power equals 2000 kW and losses are equal to 20kW then the total metered value with loss compensation would be 2020 kW; for these same settings if the meter measured 2000 kW of delivered power the total metered value with loss compensation would be 1980 kW.
Since transformer loss compensation is the more common loss compensation method, the meter has been designed for this application. Line loss compensation is calculated in the meter using the same terms but the percent values are calculated by a different methodology as described in a subsequent section below.
Nexus 1250/1252 Transformer Loss Compensation:
•Performs calculations on each phase of the meter for every measurement taken. Unbalanced loads are accurately handled.
•Calculates numerically, eliminating the environmental affects that cause inaccuracies in electromechanical compensators.
Electro Industries/GaugeTech Doc # E107706 V1.25 |
