Capacitance potential dividers for the investigation of transient overvoltages in crossbonded cables

The work outlined in the paper was initiated in order to ascertain the nature of transient overvoltages due to switching in a 132kV crossbonded-cable system. The instrumentation for recording high-voltage transients comprised high-ratio capacitance potential dividers capable of reproducing voltages at the cable terminals, cable midsections and cable joints, in conjunction with portable oscilloscopes. The theory and design of the types of potential divider used is given in detail. The design of a coaxial divider which may be built into a cable or cable joint is described. A hybrid-type potential divider has been devised for use at 33kV which employs capacitive and resistive potential division, to give a high division ratio and a flat response up to 2Mc/s, while using inexpensive components. The calibration of potential dividers is discussed, and a simple function generator devised for this purpose is described, Illustrations of calibration waveforms and oscillograms recorded in the field are reproduced.