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1). What is Power System?

The Power system is a system that is made up of the components that are used in the Distribution, Generation, and Transmission systems. The power system serves to create electrical energy by using coal and diesel as inputs. The system is equipped with components such as a

  • Motor,
  • Circuit breaker,
  • Synchronous generator,
  • Transformer, and
  • Conductor, among other things.

2). What is meant by P-V curves?

  • P is an abbreviation for pressure,
  • V is an abbreviation for volume

in the P-V curve.

A PV curve or indication diagram displays the proportional change in pressure & volume that occurs inside a system.

This curve is very helpful in a variety of processes, including thermodynamics, respiratory physiology, and cardiovascular physiology. The P-V curve was developed in the eighteenth century in order to have a better understanding of efficient engines.

3). What does “synchronous condenser” mean?

Synchronous Condenser, also known as Synchronous Phase Modifier (or) Synchronous Compensator, is a sophisticated method for increasing power factor. This is a motor that operates without the need of a mechanical load. By altering the field winding’s excitation. The reactive volt ampere may be absorbed or generated by a synchronous condenser.

For power factor improvements more than 500 KVAR, a synchronous condenser is preferable than a static condenser.

For lower-rated systems, a capacitor bank is employed.          

4). What is the difference between a fuse and a circuit breaker?

FuseCircuit Breaker
A fuse is a wire that keeps a circuit from overheating. It does not imply overload.A circuit breaker is an automatic switch that protects a circuit against overloading.
It does not denote overloads.It denotes overloads.
It can only be used once.It may be used several times.
It protects against power overloads.It protects against not just power overloads but additionally short circuits.
It is incapable of detecting fault circuit conditions.  It merely executes the interruption procedure.It detects and interrupts defective circuit conditions.
It has a low breaking strength.In compared to the fuse, it has a higher breaking capability.
It operates automatically.Circuit breakers may be either automated or manual.
It operates in a very short period of time, around 0.002 seconds.It operates in 0.02-0.05 seconds.
It is less expensive than a circuit breaker.It is expensive.

5). What is referred as tariff?

Tariff refers to the charge levied on items imported from other nations in order to make them more expensive. As a consequence, product costs rise and become less desired or competitive in comparison to local goods and services. Tariffs are imposed to limit commerce from certain foreign nations or to reduce imports of a specific product.

The government imposes two different types of tariffs:

  • Tariff Specification
  • Ad-valorem Tariff

6). What is the difference between a transmission & distribution line?

Transmission lines are utilised across long distances and have greater voltage to transfer more power. In other terms, the transmission line transfers power from the power plants to the substations.

Distribution lines deliver power across small distances. They can transfer power locally since the voltage is lower. The substation supplies power to the residences.

7). What are the different types of energy sources?

There are only two categories of energy sources,

  • Renewable Energy Source
  • Non-Renewable Energy Source

 which are further subdivided:

Renewable Energy Source – The energy sources originate from a natural source that is refreshedconstantly.

The following are examples of renewal sources:

  • Solar energy
  • Wind energy
  • Geothermal energy
  • Water energy
  • Biomass and biofuelsenergy

Non-Renewable Energy Source-The energy depleted from a source that cannot be restored and will eventually run out. Non-renewableenergy sourceincludes

  • Oil
  • Coal
  • Petroleum and
  • Natural Gas

8). What is the function of relay?

The switches that close and open the circuit are referred to as relays. They carry out this duty both electrically and electromechanically. Relays are employed in a variety of applications, including manufacturing. To manage the electricity, control panels & building automation are used.

Relay Types:Relays are classified into many types based on their operating principles. polarity and operation:

  • Electromechanical Relay
  • Solid State Relay
  • Electrothermal Relay
  • Electromagnetic relay
  • Hybrid Relay

9). What is a nuclear power plant?

Nuclear power plants employ nuclear fission to create energy. Nuclear reactors and the Rankine cycle (which converts water into steam) are used to produce heat. This steam is needed to power the turbine & generator. Nuclear power accounts for 11% of total global electricity production.

The following is a list of the components used in nuclear power reactors to create energy.

  • Steam Generation
  • Nuclear Reactor
  • Turbine & Generator
  • Water Cooling Towers

10). What is mean by cable grading or grading of cables?

The term “grading of cable” refers to the process of achieving a uniform distribution of dielectric stress (or) voltage gradient in a dielectric. The dielectric stress is at its absolute lowest at the conductor’s outermost sheath, while it is at its absolute greatest near the surface.

Because the tension is not distributed evenly across the cable, the insulation will eventually break down, which will result in the cable becoming thicker. The grading of cables is that allows for the uniform distribution of dielectric stress, which allows for this problem to be circumvented.

11). What is a pumped storage plant?

Pumped-storage  hydroelectricity, commonly known as hydroelectricity, is a kind of hydroelectric energy storage that is used for load balancing. When there is a significant demand for electricity, the reservoir’s water is discharged via turbines to create electricity. It has the most storage capacity available for the grid.

12). How to verify current transformer(CT)?

A digital multimeter equipped with a millivolt AC (mVac) range may be used to evaluate the output voltage (Vo) of a current transformer (CT) out in the field. This test is helpful for confirming that the CT is functioning correctly that current flows through the conductor on which the CT is mounted.

13). What is ACSR?

ACSR – Aluminium Conductor Steel-Reinforced Cable

The term “aluminium conductor steel-reinforced cable” (ACSR) refers to a specific kind of stranded conductor that has a high capacity and a high strength and is often used in overhead power lines. Aluminium of very high purity is used for the outer strands because of the material’s excellent conductivity, low weight, cheap cost, resistance to corrosion, and reasonable mechanical stress resistance.

14). Describe the Ferranti effect

The voltage increases at a transmission lines of receiver end compared to the  sending end voltage is known as the ferranti effect. It is seen when there is either no load connected or a very modest load.

15). What is Internal and External faults?

Internal Faults

  • Phase-to-phase faults that are internal in nature lead to system component failure.
  • Overheating and failed windings may lead to internal defects.
  • The cooling system’s failure may potentially result in a mechanical issue.

The most effective way to prevent internal defects is via testing and maintenance.

External Faults

  • An external failure happens outside the transformer or system. It does not include defective hardware.
  • Damage may result from external issues like lightning strikes.
  • It is a defect even if the air temperature is higher than a threshold value.

Since these conditions are unpredictable, the problem can only be fixed after the underlying cause has disappeared.

Therefore, it is crucial to be ready for these types of circumstances. External faults are minimal, but if the issue is not fixed, the system might fail.

16). What is meant by electrical grounding and earthing?


Grounding may be used to obtain insulation against unintentional currents. The main wire is attached to the power source, while a separate section of the cable is tucked inside the mattress. Overloading and other harmful consequences are avoided.


Because these unplanned surges and bursts of electricity pose a risk to human life, earthing is utilised to defend against them. Connecting an earth wire from equipment to the ground allows for earthing. An extremely low resistance channel for the passage of electricity to ground is provided by earth wire. A person won’t experience the shock as a result.

17). What is Sag?

The distance between the highest point of a pair of electric poles or towers from the lowest point of the conductor that connects those two points is called sag.

18). What type of effects does the sudden increase in voltage (or) over voltage surge affect have on the power system?

Surges may create overvoltage, which can lead to spark over & flash over between phase & ground at the network’s weakest point, the collapse of gaseous, solid, or liquid insulation, and the failure of spinning machinery and transformers.

19). What does “Bus Bar Protection” refer to?

The purpose of bus bar protection, as the name implies, is to safeguard the bus bar from any type of error. If a bus bar failure occurs, the feeders are disconnected and the whole supply is disrupted. The error has a number of causes such as an external product accidently falling over the bus bar, a failure of the circuit breakers, or a breakdown of the support insulators. The following are the most popular bus zone protection schemes

  • Back-up protection
  • Circulating current protection
  • Voltage Overvoltage protection
  • Differential Overcurrent protection
  • Frame leakage protection

20). What are the primary effects of the electrical faults?

The following are some of the effects of power system faults:

  • The heat produced by the significant quantity of the defect might result in overheating and mechanical stress.
  • There is always a risk of fire due to arcing large currents create. The fire can spread to the system component if the malfunction continues for a longer period of time.
  • Additionally, overheating may shorten the life of insulation by weakening it.
  • Rotating machinery linked to the system may get heated by imbalanced current and voltage.
  • Since each generator is linked to the others, synchronisation is required. Unbalanced current and voltage may cause the whole system to crash, and in the worst condition, they might cause a blackout.
  • Because the supply to the customers may be interrupted, it may also make the system less reliable. Additionally, a failure might harm the tools utilised in the power system network.

In order to prevent the problem mentioned above, it is essential to repair the system’s problematic component.

21). What is the purpose of bundle conductor?

A bundle conductor is made up of two or more sub-conductors. It functions as a conductor for one phase. One, two, three, or four sub-conductors may be used to make up one phase. For voltages higher than 22 kV, bundle conductor is employed.

The transmission is the bundle conductor’s primary function. By lowering inductance and the skin effect, it maintains the voltage and improves efficiency.

22). What is the different power system operational states?

The different states are:

Normal  state

When both operational limits and load are satisfied, the system is said to be normal. The overall demand for all operational limitations must be satisfied for the system to operate in its natural condition.

Alert state

In the event that the system’s security level is lower than a predetermined threshold or the degree of system disruption increases.

Emergency state

The system will enter the emergency state if the disruption is significant while it is in an alert state. Utilising corrective action, the system will either revert to its default settings or enter an alert mode.

Extremis state

If no preventative action is taken during the emergency condition, it moves to one of the two extremis states. In this condition, the control action has been executed in order to return the system to either the emergency condition or the regular state.

23). What is meant by Slack Bus?

When it pertains to electric power, Swing bus is another name for slack bus, and V bus is the term of slack bus. In order to keep the active power IPI & reactive power IQI in a system from becoming unbalanced during load flow studies, a slack bus is used in the system. It either sends out or takes in the active (or) reactive power coming into or going out of the system.

24). When Directional Relays are employed?

The direction relay becomes operational whenever the power flows in the transmission line proceeds in a certain direction.

25). How many numbers of relays are necessary to effectively protecting a device?

A two-phase fault relay & one earth fault relay are needed for improved protection.In order to provide enough protection, devices will require both type of relays.

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