DEVELOPMENT AND APPLICATION OF A 10 MHZ DIGITAL SYSTEM FOR CURRENT-ZERO MEASUREMENTS

After a short historical review, the development of an accurate digita l system is described that is intended for measurement of are currents and voltages in the current-zero period of circuit breakers during hi gh-power tests. Two channels with 12-bit resolution and 10 M samples p er second can each store 4 K of data using 400 mu s. The transmitting unit is battery operated near to the test object, free from ground. Th e receiving unit is at ground potential, coupled by an optic fibre syn chronous link. As a current device, an M coil is applied to measure th e derivative of the current. For the voltage device, a special capacit ive divider has been developed. Results of current-zero tests in vacuu m and SF6 circuit breakers are presented and discussed.