ed at or below their rated voltage. All of our capacitors are designed with a continuous overvoltage capability of 110% of rated voltage. This overvoltag capability allows the capacitor to withstand unbalanced and system voltages higher than the rated m
Meters such as the Fluke 110, 170, and 180 series can provide the required data necessary to determine the presence of a failed capacitor. Although other test methods are available, such as live testing, this technical note is centered on testing capacitors in their de-energized state.
Due to their relatively low capacitance (0.20uF to 100.00uF), testing of the capacitors can be done with many standard digital multi-meters (DMM's). Meters such as the Fluke 110, 170, and 180 series can provide the required data necessary to determine the presence of a failed capacitor.
De-energize the capacitor bank per the recommendations of the capacitor bank manufacturer. All necessary safety procedures should be followed. Isolate the capacitor bank (i.e. provide a visible disconnect) from the medium or high voltage system. Wait at least five minutes after de-energization before proceeding to the next step.
It is therefore recommended that externally fused capacitors be tested before replacement in situations where the external fuse has blown. For internally fused capacitors, testing is required as the fuse is not visible. The following test procedure requires the capacitor/harmonic filter bank to be grounded and disconnected.
Open Capacitors - Typically the DMM will show a "di.sc" or a very low capacitance reading (capacitance reading in the 0 to 1 nF). Partially Failed Capacitors - Typically the DMM will show a capacitance reading that is more than 10% greater than the capacitors nominal value as shown in Table-1.