Answer / pritish

in case of short transmission line, the protection due to arc resistance is the major factor. hence , the relay should be selected which is less affected to arc resistance. and according to R-X diagram of impedance and reactance relay, the area of reactance relay is more and it is less affected to arc resistance fault but impedance relay is moderately affected due to arc resistance. so reactance relay is used in a short transmission line.


for more clarification, please email to pritish.nath@gmail.com

Answer / niket gupta

In the short transmission single to ground falling fault are occur 85% so when this fault occur then the resistance are changed so impedace are also changed and arc producing so we not use the impedance relay

Answer / nagesh.patwari

1. During Short circuit current Step and Touch potential increases.Step potential : It is the potential developed between the two feet on the ground of a man or animal when short circuit occurs. This results in flow of current in the body leads to electrical shockTouch potential: It is the potential that is developed between the ground and the body of the equipment when a person touches the body during fault condition. When operating personnel touch an electrical equipment during short circuit condition, fault current flows through the human body. This is defined as touch potential.Gravel/Stones in the substation is provided to reduce the step potential and touch potential when operators work on switch yard.2. Power Transformers installed in the substations will have oil as cooling and insulating medium. Oil leakage takes place during operation or when changing the oil in the transformer. This oil spillage which can catch fire is dangerous to the switchyard operation. So Stones/Gravel is provided to protect from fire when oil spillage takes place.3. Stones eliminate the growth of small weeds and plants inside the switch yard4. Improves yard working condition5. Provides protection from wild life and snakes.

Answer / k.prakashchandra

The impedance too small to be measured

before transformer oil dielectric strenght tests are taken the oil should be allowed to settle to remove option 1 air bubbles 2 gasses 3 contamination 4 water

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