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.
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
The tendency of a Reach of Distance Relay to operate at impedance larger than its setting value is known as overreach. Overreach is the presence of d.c. offset in the fault current wave, as the offset current has a higher peak value than that of a symmetrical wave for which the relay is set.
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