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Find top electrical engineering interview questions and answers on transformers, breakers, protection, and testing for job preparation.
What is the main purpose of a power transformer? A power transformer is mainly used to transfer power from one voltage level to another voltage level for transmission or sub-transmission purposes. Power transformers are of two types: step-up transformers and step-down transformers. A step-up transformer increases the voltage level of the generated power from the … Read more
Why are stress cones used in cable termination? When a high-voltage cable is cut for termination, the metallic sheath or screen of the cable is also cut. As a result, a sharp edge is created at the cut end of the sheath. At this sharp edge, the electric field becomes highly concentrated, which produces high … Read more
What is a VRLA Battery Bank? The full form of VRLA is “Valve Regulated Lead Acid”. Therefore, a VRLA battery means a Valve-Regulated Lead-Acid battery. It is essentially a modified version of a conventional low-maintenance lead-acid battery. Overchargings form oxygen and hydrogen gases due to electrolysis of water. These gases escape through vents provided on … Read more
What is the Rated Voltage Factor in voltage transformers, and how is it determined? This is the ratio of the maximum operating voltage to the rated primary voltage of the PT. We have to multiply this factor by the primary rated voltage. This determines the maximum operating voltage of the PT. In other words, this … Read more
What is the definition of the rated voltage of a lightning arrester? As per IS 3070, the definition of the “rated voltage of a Lightning Arrester” is given below.The maximum permissible r.m.s. value of power-frequency voltage between the line and earth terminal under temporary over-voltage conditions for a duration of 10 seconds as established in … Read more
What are the short circuit withstand levels for 400kV, 220kV, and 132kV transformers? 400 kV transformers must withstand 63 kA for 1 second. 220 kV transformers must withstand 50 kA for 1 second and 40 kA for 3 seconds. 132 kV transformers must withstand 40 kA for 1 second and 31.5 kA for 3 seconds. … Read more
What type of circuit breaker is generally used for the 36KV class? Ans: The 36KV class circuit breaker is normally an outdoor type Vacuum Circuit Breaker (VCB). Why is VCB Preferred in 33KV Outdoor Systems Over SF6 Circuit Breakers? Ans: VCBs offer a more economical approach for 33KV systems compared to SF6 circuit breakers. It … Read more