S&C Instruction Sheet 768-550 29
Additional Calibration Factors for Self-
Powered Units
Because the battery charger influences the voltage-sensor
ratios, users may wish to further refine the accuracy of the
sensor(s) to ensure voltage output accuracy.
As a consequence, the magnitude-ratio and phase-
angle shift measurements may also be used by the RTU to
calculate system analog values. The corrected sensor ratios
may be used by the RTU to adjust the sensor outputs to
account for the tolerance variations in the components.
The magnitude-ratio and phase-angle shift measurements
of the battery charger are written on a label affixed to the
battery-charger cover.
Voltage-sensor ratio corrections—battery charger phase
magnitude ratio = Yb Xv / Kv
Where Kv = 1386 (for 14.4-kV switches), or
2440 (for 25-kV switches), or
3389 (for 34.5-kV switches)
Xv = magnitude ratio of voltage-sensor
portion of current/voltage sensor
Yb = magnitude ratio of battery charger
Calibration
