MGVCL Exam Paper (30-07-2021 Shift 3)
In transformers, Statement 1: Deterioration of oil may occur due to the result of prolonged overloading of the transformer. Statement 2: Dielectric faults occur in the winding due to turn-to-turn insulation breakdown.
Dielectric faults occur in the winding due to turn-to-turn insulation breakdown. It is the insulation between the turns of the winding. Insulation breakdown commonly occurs due to high current and voltage which are high above the rated values. The breakdown of the insulation results in the flashover of the winding turns and cause a short circuit.
Deterioration of oil may occur due to the result of prolonged overloading of the transformer. Excessive oil temperature produces the formation of sludge, water, and acids. Moisture entering the oil as a result of the breathing action greatly reduces its dielectric strength so that breakdown from coils or terminal leads to tank or core structure may take place.
Advanced metering infrastructure (AMI) is an integrated system of smart meters, communications networks, and data management systems that enables two-way communication between utilities and customers. The goal of an AMI is to: Provides utility companies with real-time data about power consumption and allow customers to make informed choices about energy usage based on the price at the time of use.
Bus Type - Known Parameter - Unknown Parameter Load Bus -P, Q - V, phase angle Generator Bus - P, V (magnitude) - Q, Voltage phase angle Slack Bus Voltage - magnitude and phase angle - P, Q
Frequency response analysis is the technique whereby a sinusoidal test signal is used to measure points on the frequency response of a transfer function or impedance function. Sweep Frequency Response Analysis (SFRA) testing provides insight into the mechanical and electrical integrity of transformers.
Main Purpose of SFRA Test: Transformer Core displacement Winding displacement for both rotor and transformer Broken or loosen clamp connections Inter turn short circuit Internal short circuit Winding to Core Earth fault Winding Open circuit condition
EXAMIANS