MGVCL Exam Paper (30-07-2021 Shift 3)
Consider the following statements associated with Buchholz’s relays. Statement 1: Buchholz's relay is used for protection of a transformer against incipient faults. Statement 2: Buchholz's relay can be installed on oil cooled transformers.
Buchholz relay is used for protecting transformer against incipient or internal faults. Buchholz relay is a gas-actuated relay installed in oil immersed transformers for protection against all kinds of faults.
Here auto transformer change voltage from 600 V to 200 V. Voltage ratio (a) = 600/200 = 3 kVA rating of the auto-transformer = (a/(a - 1))*(kVA rating of auto transformer) = (3/2)*20 = 30 kVA
When voltage changes occur in rapid succession, with magnitudes large enough to cause lighting level variations. The human eye-brain response is most sensitive to periodic r.m.s. voltage changes that occur at around 8 - 10 cycles per second.
EXAMIANS