Switchgear and Protection

For cost and safety, the outdoor substations are installed for voltages above_________________? A. 11 kVB. 33 kV C. 60kV D. 110kV

Short-circuit currents are due to_______________? A. single phase to ground faults B. phase to phase faults C. two phase to ground faults D. three phase faultsE. any of these

A.C. network analyser is used to solve problems of_______________? A. load flow B. load flow and short-circuit C. load flow and stabilityD. load flow, short-circuit and stability E. none of the above

To reduce short circuit fault currents are used_____________? A. reactors B. resistors C. capacitors D. none of the above

Induction cup relay is operated due to changes in________________? A. current B. voltage C. impedanceD. all of the above

When a wave propagates on a transmission line, it suffers reflection several times at_____________? A. tapg B. load end C. sending endD. sending and other end E. all of the above

The reflection co-efficient at the open circuited end of a transmission line___________? A. zero B. infinityC. unity D. none of the above

The contacts of high voltage switches used in power system are submerged in oil. The main purpose of the oil is to______________? A. lubricate the contacts B. insulate the contacts from switch bodyC. extinguish the arc D. all of the above E. none of the above

H.R.C. fuses provide best protection against________________? A. overload B. reverse current C. open-circuitsD. short-circuits

To protect most of the electrical equipment handling low power, the types of relays used are______________? A. thermocouple B. electronic and bimetallicC. both (A) and (B) D. none of the above