National Cement Company Senior Electrical Engineer Interview Questions and Answers

Substations use various equipment for power distribution and control.

• Transformers: Step up or step down voltage levels.

• Circuit breakers: Protect the system from overloads and faults.

• Switchgear: Control and isolate electrical circuits.

• Busbars: Distribute power to different parts of the substation.

• Relays: Monitor and protect the system from abnormalities.

• Capacitors: Improve power factor and voltage stability.

• Disconnect s...read more

CTs, PTs, LAs, and Transformers are electrical devices used in power systems for measurement, protection, and voltage transformation.

• CTs (Current Transformers) are used to measure and transform high currents into manageable levels for instruments and relays.

• PTs (Potential Transformers) are used to measure and transform high voltages into low voltages for instruments and relays.

• LAs (Lightning Arresters) are used to prot...read more

Circuit breakers are safety devices that protect electrical circuits from damage caused by overload, short circuit, or ground fault.

• Circuit breakers are used to prevent damage to electrical equipment and wiring.

• They interrupt the flow of electricity when there is an overload, short circuit, or ground fault.

• Circuit breakers are commonly used in homes, businesses, and industrial settings.

• They come in different sizes and ...read more

The rating of copper and aluminium cables depends on their size, insulation, and intended use.

• Copper cables have higher conductivity and are therefore rated higher than aluminium cables of the same size.

• The rating of a cable also depends on its insulation material and thickness.

• Cables used for high voltage transmission have higher ratings than those used for low voltage applications.

• For example, a 10 AWG copper cable m...read more

Types of protection on Transformer side line side

• Overcurrent protection

• Differential protection

• Restricted earth fault protection

• Overvoltage protection

• Under voltage protection

Different types of relays are used for protection system such as overcurrent, differential, distance, and directional relays.

• Overcurrent relays are used to protect against overloads and short circuits.

• Differential relays are used to protect transformers and generators from internal faults.

• Distance relays are used to protect transmission lines from faults.

• Directional relays are used to protect against faults in specific...read more