System voltage calibration

A method for calibrating a capacitor voltage sensor that measures voltage on a power line at medium voltage coupled through a bushing well interrupter (BWI) to a primary coil of a transformer that is part of a series of transformers associated with a loop circuit, where each transformer includes a source side BWI and a load side BWI, the method comprising:

• measuring a control voltage on a secondary coil of the transformer;
• measuring voltage on the capacitor sensor when the BWI is known to be closed and the voltage on the primary coil is the same as the voltage on the power line;
• identifying a calibration factor that when multiplied by the measured voltage on the capacitor sensor when the BWI is closed makes the measured voltage on the capacitor sensor substantially equal to the control voltage;
• subsequently measuring voltage on the capacitor sensor when the BWI is open or closed during operation of the transformer;
• and
• multiplying the subsequently measured voltage on the capacitor sensor when the BWI is open or closed by the calibration factor to obtain a measured voltage.

A system for calibrating a capacitor voltage sensor that measures voltage on a power line coupled through a switch to a primary coil of a transformer, the system comprising:

• means for measuring a control voltage on a secondary coil of the transformer;
• means for measuring voltage on the capacitor sensor when the switch is known to be closed and the voltage on the primary coil is the same as the voltage on the power line;
• means for identifying a calibration factor that when multiplied by the measured voltage on the capacitor sensor when the switch is closed makes the measured voltage on the capacitor sensor substantially equal to the control voltage;
• means for subsequently measuring voltage on the capacitor sensor when the switch is open or closed during operation of the transformer;
• and
• means for multiplying the subsequently measured voltage on the capacitor sensor when the switch is open or closed by the calibration factor to obtain a measured voltage.