Power Grid Corporation of India Interview Questions, Process, and Tips

Transformers are rated in KVA because it represents the apparent power they can handle.

• KVA stands for kilovolt-ampere, which is a unit of apparent power.

• Transformers are designed to handle a certain amount of power, and the KVA rating indicates their capacity.

• The KVA rating takes into account both the voltage and current that the transformer can handle.

• It helps in determining the appropriate size and capacity of the tr...read more

The ground clearance of a 400KV transmission line varies depending on various factors.

• The ground clearance of a transmission line is the vertical distance between the lowest point of the conductor and the ground.

• The ground clearance is determined based on safety regulations and requirements.

• Factors that influence the ground clearance include terrain, vegetation, and proximity to buildings or roads.

• In hilly areas, the g...read more

The tan Delta value of electrical equipment should be as low as possible.

• Tan Delta is a measure of the dielectric losses in electrical equipment.

• A low tan Delta value indicates that the equipment has good insulation properties.

• The tan Delta value can be affected by factors such as temperature, moisture, and aging of the equipment.

• For transformers, a typical tan Delta value is around 0.001 or lower.

ACSRinvar conductors are widely used in metro principal cities due to their high strength and low thermal expansion.

• ACSRinvar conductors have a high tensile strength, making them suitable for long-distance transmission lines in metro cities.

• They have a low coefficient of thermal expansion, which helps in reducing sagging of the conductors and maintaining power transmission efficiency.

• The use of ACSRinvar conductors in ...read more

The Basis setting of REF protection for a transformer should be determined based on the transformer's characteristics and the system requirements.

• The basis setting of REF (Restricted Earth Fault) protection for a transformer is typically determined by considering the transformer's winding configuration, impedance, and the system's fault level.

• The setting should be chosen to ensure that the protection operates reliably ...read more

The SF6 gas used for Ckt breaker chamber should be maintained at a pressure of around 5-7 bar.

• The SF6 gas in the circuit breaker chamber should be maintained at a specific pressure to ensure proper functioning.

• The recommended pressure for SF6 gas in the circuit breaker chamber is typically between 5 and 7 bar.

• Maintaining the correct pressure helps in extinguishing the arc during circuit interruption.

• Too low or too high...read more

Star-star zero phase shift transformer windings are used to provide a balanced three-phase output with zero phase shift between primary and secondary voltages.

• Star-star zero phase shift transformer windings are commonly used in power distribution systems.

• They are used to supply power to three-phase loads such as motors, generators, and transformers.

• The windings are designed in such a way that the voltages in the primar...read more

AIS and GIS substations differ in their construction and insulation methods.

• AIS (Air Insulated Substation) uses air as the insulation medium, while GIS (Gas Insulated Substation) uses SF6 gas.

• AIS substations require larger land areas compared to GIS substations.

• GIS substations are more compact and can be installed in urban areas where space is limited.

• AIS substations are more susceptible to environmental factors like p...read more

Vibration dampers are used with conductors to reduce the risk of fatigue failure and damage caused by wind-induced vibrations.

• Vibration dampers absorb and dissipate the energy generated by wind-induced vibrations in conductors.

• They help to reduce the risk of fatigue failure and damage to the conductor and associated hardware.

• Vibration dampers are typically installed at regular intervals along the length of the conducto...read more

The main function of LA in a substation is to protect electrical equipment from lightning strikes.

• LA stands for Lightning Arrester.

• It is installed in substations to divert lightning strikes away from sensitive equipment.

• LA provides a low-impedance path for lightning current to flow to the ground.

• It helps in preventing damage to transformers, circuit breakers, and other electrical devices.

• LA operates by ionizing the air...read more