A. ground connection for the system neutral
B. the discharge path for surge arresters
C. safety to the operating personnel
D. All of the above
Answer: D. All of the above
Explanation:
The need of earthing:
Power plants and substations are extremely vulnerable to hazards of lightning strikes, electrical and mechanical equipment malfunctioning, and human errors in which surge current of the order of kilo amperes is impressed on the plant or is generated from within.
Earthing:
It is to provide a sufficiently low impedance path and means to carry and dissipate electric currents into the ground under normal and fault conditions without exceeding any operating and equipment limits or adversely affecting continuity of service.
It provides a ground connection for the system neutral.
Advantages of earthing:
Adequate earthing of electrical substations is of significant importance to increase the reliability of the supply service as it helps
to provide stability of voltage conditions
preventing excessive voltage peaks during disturbances
providing protection against lightning
provides a discharge path for surge arresters
Other than that, an earthed system can assure such a degree of human safety that a person working or walking in the vicinity of grounded facilities is not exposed to the danger of a critical electric shock.