900+ Electrical Engineer Interview Questions and Answers

Lightning arresters are used in transmission lines to protect the equipment and infrastructure from damage caused by lightning strikes.

• Lightning arresters divert the high voltage surge caused by lightning strikes to the ground, preventing it from damaging the transmission lines.

• They provide a low-resistance path for the lightning current to flow, reducing the risk of electrical breakdown and flashovers.

• Lightning arresters help in maintaining the insulation levels of the trans...read more

Switchgear is an electrical equipment that controls, protects, and isolates electrical circuits.

• Switchgear is used to control power supply in electrical systems.

• It protects electrical equipment from damage caused by overloads, short circuits, and faults.

• Types of switchgear include low voltage, medium voltage, and high voltage switchgear.

• Relays are used in switchgear to control the flow of electricity.

• Types of relays include electromagnetic, thermal, and solid-state relays.

Different types of tests to be performed in power transformer

• Insulation resistance test

• Ratio test

• Polarity test

• Vector group test

• No-load test

• Load test

• Temperature rise test

Buchholz relay is used to protect transformers from faults by detecting gas and oil flow abnormalities.

• Buchholz relay is installed in the pipe connecting the transformer tank and conservator tank.

• It operates based on the principle that faults in the transformer generate gases and cause oil flow disturbances.

• When gas or oil flow abnormalities occur, the relay trips and sends a signal to the control panel to isolate the transformer.

• It provides protection against faults such as ...read more

AC stands for alternating current and DC stands for direct current.

• AC is a type of electrical current that periodically changes direction.

• DC is a type of electrical current that flows in one direction.

• AC is commonly used in household appliances and power distribution systems.

• DC is commonly used in batteries and electronic devices.

• Examples of AC sources include power grids and generators.

• Examples of DC sources include batteries and solar panels.

We use Allen Bradley PowerFlex VFD drivers in our plant.

• Our plant uses VFD drivers for controlling the speed of AC motors.

• Allen Bradley PowerFlex VFD drivers are known for their reliability and performance.

• These drivers offer a wide range of features such as overload protection, fault diagnostics, and energy savings.

• We have installed these drivers in various applications such as pumps, fans, and conveyors.

• Our maintenance team is trained to troubleshoot and repair these driver...read more

The maximum voltage of transmission line in India is 765 kV.

• The highest voltage level in India is 765 kV.

• This voltage level is used for long distance transmission of electricity.

• India has several high voltage transmission lines, including the Raigarh-Pugalur HVDC line.

• The maximum voltage level has increased over the years, from 400 kV to 765 kV.

• Higher voltage levels allow for more efficient transmission of electricity.

MPCB and MCB are both circuit protection devices, but they differ in terms of their applications and trip characteristics.

• MCB stands for Miniature Circuit Breaker, while MPCB stands for Motor Protection Circuit Breaker.

• MCBs are primarily used for residential and commercial applications, while MPCBs are specifically designed for motor protection in industrial settings.

• MCBs have a fixed trip current rating and are typically used to protect circuits and appliances from overload ...read more

A two-phase motor is an electrical motor that operates with two alternating currents, providing improved torque and power output.

• Two-phase motors have two windings that are 90 degrees out of phase with each other.

• They are commonly used in applications that require high starting torque, such as air conditioners and refrigerators.

• Two-phase motors can be either synchronous or induction motors.

• They are more efficient and provide smoother operation compared to single-phase motors....read more

The material with zero temperature coefficients is called a zero temperature coefficient material (ZTC).

• ZTC materials have a constant resistance over a wide range of temperatures.

• Examples of ZTC materials include copper, gold, and platinum.

• These materials are commonly used in precision resistors and temperature sensors.

• ZTC materials are also used in electronic circuits to compensate for temperature changes.

The motor used in a washing machine is typically an induction motor.

• Induction motors are commonly used in washing machines due to their reliability and efficiency.

• These motors work by creating a rotating magnetic field that drives the motion of the washing machine drum.

• They are designed to handle the load and torque requirements of washing machine operations.

• Examples of induction motors used in washing machines include single-phase and three-phase motors.

• Some washing machines...read more

Control diagram of a motor with remote and local start using star delta starter.

• Use a star delta starter for reduced voltage starting

• Include a remote start/stop switch in the control circuit

• Use a contactor to switch between star and delta connections

• Include overload protection in the circuit

• Use a control transformer to step down voltage for control circuit

• Include a pilot light to indicate motor status

Different types of tests related to transformers include routine tests, type tests, and special tests.

• Routine tests are performed on every transformer and include measurement of winding resistance, insulation resistance, and voltage ratio.

• Type tests are performed on a sample transformer to verify its design and include temperature rise test, impulse test, and short-circuit test.

• Special tests are performed on transformers with specific requirements and include noise level test...read more

Yes, electrical load calculation is the process of determining the amount of power that a building or electrical system requires.

• Electrical load calculation involves considering the power requirements of various electrical devices and appliances in a building or system.

• Factors such as voltage, current, and power factor are taken into account during the calculation.

• Load calculation helps in determining the appropriate size of electrical equipment, such as transformers, circuit...read more

Amperes current law states that the current flowing through a conductor is directly proportional to the voltage applied across it.

• Amperes current law is also known as Kirchhoff's current law.

• It is used to calculate the current flowing through a circuit.

• Motors work on the principle of electromagnetic induction.

• Different types of motors include AC motors, DC motors, stepper motors, and servo motors.

• The function of a commutator is to reverse the direction of current flow in a DC...read more

Impedance voltage of a transformer is the voltage drop that occurs across the transformer's impedance when a current flows through it.

• Impedance voltage is a result of the transformer's internal impedance.

• It is caused by the resistance and reactance of the transformer's windings and core.

• Impedance voltage can be calculated by multiplying the current flowing through the transformer with its impedance.

• It represents the voltage that is required to overcome the impedance and allow...read more

The number of turbines at a generating site varies depending on the specific site.

• The number of turbines can range from a few to several dozen, depending on the size and capacity of the generating site.

• Large-scale wind farms can have hundreds of turbines, while smaller sites may only have a handful.

• The number of turbines is determined by factors such as available land, wind resource, and desired power output.

• For example, a wind farm in Texas called Roscoe Wind Farm has 634 tu...read more

The process for a project involves planning, design, implementation, testing, and commissioning.

• Define project scope and objectives

• Create a project plan with timelines and milestones

• Design the system or product

• Procure necessary materials and equipment

• Implement the design and build the system or product

• Test the system or product to ensure it meets requirements

• Commission the system or product for use

• Provide ongoing support and maintenance

• Document the entire process for future r...read more

Different sequence of current in SLG, LLG, LLLG faults.

• SLG fault has only one phase grounded, LLG fault has two phases grounded, LLLG fault has all three phases grounded

• In SLG fault, the sequence of current is positive-negative-zero, in LLG fault it is zero-positive-negative, and in LLLG fault it is zero-zero-zero

• These faults can cause damage to electrical equipment and must be quickly detected and resolved

Open secondary winding in potential transformer causes high voltage in secondary circuit.

• Secondary voltage increases to dangerous levels

• May cause insulation failure

• Can damage equipment connected to secondary circuit

• Can be prevented by using protective devices like fuses and circuit breakers

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 may be rated for 30 amps, while a 10 AWG aluminium cable ma...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 protect electrical equipment from lightning strikes and voltag...read more

Types of breakdown include thermal, dielectric, and electrostatic. Types of maintenance include corrective, preventive, and predictive.

• Thermal breakdown occurs due to excessive heat and can cause insulation failure.

• Dielectric breakdown occurs due to high voltage and can cause insulation failure.

• Electrostatic breakdown occurs due to static electricity and can cause damage to electronic components.

• Corrective maintenance is performed after a failure has occurred.

• Preventive maint...read more

The latest technology in transformer fire exposition safety system includes advanced monitoring systems, fire suppression techniques, and enhanced insulation materials.

• Advanced monitoring systems use sensors to detect abnormal temperature rise or gas emissions, triggering alarms and shutdowns.

• Fire suppression techniques include the use of automatic water mist systems, which quickly extinguish fires and minimize damage.

• Enhanced insulation materials, such as fire-resistant coat...read more

The procedure for material selection, calculations, and real-time experience in projects involves thorough research, analysis, and testing.

• Research different materials based on project requirements and constraints

• Perform calculations to determine material properties, dimensions, and feasibility

• Conduct tests and simulations to validate material selection and design choices

• Gain real-time experience through hands-on project work and troubleshooting

• Iterate on material selection a...read more

Universal motors are used for AC and DC power while series motors are used for DC power only.

• Universal motors have a high starting torque and can operate at high speeds, making them suitable for appliances like vacuum cleaners and power tools.

• Series motors have a high starting torque and can operate at low speeds, making them suitable for applications like electric trains and cranes.

• Universal motors have brushes that wear out quickly due to the high speeds and frequent use, w...read more

Proper protection measures must be taken when working with HT/LT lines and transformers.

• Ensure proper grounding and earthing of the system

• Use appropriate types of conductors for the specific application

• Perform regular cable testing to ensure safety and reliability

• Implement safety protocols and procedures for working with high voltage equipment

• Use personal protective equipment (PPE) such as gloves, goggles, and insulated tools

• Follow all relevant safety codes and regulations

Electrical panel is a device that receives power from a source and distributes it to various circuits.

• Electrical panel is also known as a breaker panel or distribution board

• Cable trays are used to support and protect electrical cables

• Perforated cable trays have holes for ventilation while ladder cable trays have rungs for support

• Sizes of cable trays vary depending on the number and size of cables being supported

• Cable trays are erected by attaching them to walls or ceilings us...read more

Swing equations are used to model the behavior of power systems during transient events.

• Swing equations are a set of differential equations that describe the dynamics of power systems during transient events.

• They are used to model the behavior of generators, transformers, and other components in the power system.

• Swing equations take into account the mechanical and electrical properties of the system, as well as the power flow and voltage levels.

• They are important for analyzin...read more

A single line diagram of a distribution system is required with proper specifications.

• The diagram should show the flow of power from the source to the load

• It should include all components such as transformers, switchgear, and cables

• The specifications should include voltage levels, power ratings, and protection devices

• The diagram should follow standard symbols and conventions

• Example: A 11 kV distribution system with a 500 kVA transformer and 630 A circuit breaker

To design busbar for increased fault level but same current rating, increase the cross-sectional area of the busbar.

• Increase the thickness of the busbar

• Increase the width of the busbar

• Use materials with higher conductivity

• Use busbar supports with higher short-circuit strength

• Consider the temperature rise of the busbar

• Perform a fault level calculation to determine the required cross-sectional area

A machine is a device that uses energy to perform a task. The principle of a machine is to make work easier. High voltage has advantages in power transmission.

• A machine is a mechanical or electrical device that uses energy to perform a task.

• The principle of a machine is to make work easier by multiplying force or changing the direction of force.

• Examples of machines include engines, motors, pumps, and generators.

• High voltage is advantageous in power transmission because it red...read more

Types of protection on Transformer side line side

• Overcurrent protection

• Differential protection

• Restricted earth fault protection

• Overvoltage protection

• Under voltage protection

The stator is used in an induction motor to generate a rotating magnetic field.

• The stator consists of a set of windings that are connected to an AC power source.

• When the AC power is applied, the stator windings create a rotating magnetic field.

• This rotating magnetic field induces currents in the rotor, which in turn creates a torque and causes the rotor to rotate.

• The stator windings are typically made of copper or aluminum and are arranged in a specific pattern to create the ...read more

The transformer step down voltage in high tension section depends on the specific system and requirements.

• The step down voltage is determined by the transformer's turns ratio

• High tension sections typically operate at voltages above 100 kV

• Step down transformers are used to reduce voltage for distribution to lower voltage systems

An induction motor works on the principle of electromagnetic induction to generate rotating magnetic fields.

• Induction motor has a stator with a set of windings that are connected to an AC power source.

• When AC current flows through the stator windings, it creates a rotating magnetic field.

• This rotating magnetic field induces current in the rotor windings, causing the rotor to rotate.

• The speed of the rotor rotation is slightly less than the speed of the rotating magnetic field,...read more

The current carrying capacity of conductors varies depending on their material and size.

• The current carrying capacity of a conductor is determined by its cross-sectional area.

• Conductors with larger cross-sectional areas can carry more current.

• The material of the conductor also affects its current carrying capacity.

• Copper is a commonly used conductor material with high current carrying capacity.

• Aluminum is another conductor material but has a lower current carrying capacity co...read more

The bending radius for HT cables varies depending on the cable type and size.

• The bending radius for XLPE cables is typically 12 times the cable diameter.

• For PILC cables, the bending radius is usually 20 times the cable diameter.

• The bending radius for EPR cables is generally 10 times the cable diameter.

• It is important to follow the manufacturer's recommendations for bending radius to avoid damaging the cable.

• Bending radius can also be affected by factors such as temperature an...read more

The maintenance procedure of DG involves regular checks and servicing to ensure optimal performance.

• Regularly check oil and coolant levels

• Inspect air filters and replace if necessary

• Clean and inspect spark plugs

• Check battery and charging system

• Perform load bank testing

• Schedule routine maintenance with a qualified technician

• Keep a maintenance log for record keeping

Lighting levels for indoor and outdoor areas are determined based on the purpose of the space and the activities that take place.

• Indoor lighting levels are typically measured in foot-candles or lux

• Outdoor lighting levels are typically measured in lumens per square meter

• Calculation procedures involve determining the required illuminance level for the space and selecting appropriate light fixtures and bulbs

• Factors such as color rendering index, color temperature, and glare cont...read more

Yes, core loss depends upon frequency.

• Core loss is the energy lost in the magnetic core of a transformer or inductor.

• It is caused by hysteresis and eddy current losses.

• Hysteresis loss is proportional to the frequency and magnetic flux density.

• Eddy current loss is proportional to the square of the frequency and the thickness of the core.

• Higher frequency leads to higher core loss, which can cause overheating and reduced efficiency.

Various types of equipment are required in LT and HT line work, including transformers, circuit breakers, insulators, conductors, and protective devices.

• Transformers

• Circuit breakers

• Insulators

• Conductors

• Protective devices

Feeder charging and handing over involves the process of transferring electrical power from one source to another.

• Ensure proper safety measures are in place before starting the process

• Check the voltage and current ratings of the feeder to ensure compatibility with the receiving end

• Disconnect the feeder from the power source and connect it to the receiving end

• Verify the successful transfer of power and ensure proper functioning of the system

• Complete necessary documentation and...read more

Earthing road is used in HT lines to provide a path for fault current to flow safely into the ground, preventing damage to equipment and ensuring safety.

• Earthing road is a conductive strip or wire buried in the ground near HT lines.

• It provides a low resistance path for fault current to flow into the ground, preventing damage to equipment and ensuring safety.

• Proper installation of earthing road involves burying the conductor at a sufficient depth below the surface to ensure go...read more

Dewpoint test is done in transformer to check the moisture content in the insulation oil.

• Moisture in insulation oil can cause breakdown of transformer insulation

• Dewpoint test helps to determine the moisture content in the oil

• It is a preventive maintenance measure to avoid transformer failure

• The test involves cooling a mirror until dew forms on it, and measuring the temperature at which dew forms

Yes, I can draw a single line diagram of s/d starter.

• A single line diagram shows the electrical connections and components in a simplified manner.

• For an s/d starter, the diagram would include the power supply, motor, overload relay, and contactor.

• The diagram would also show the control circuit components such as push buttons and switches.

• The diagram should follow standard symbols and conventions for electrical diagrams.

• An example of a single line diagram for an s/d starter ca...read more

Yes, I have experience managing spare parts and their records and documents.

• I have previously managed spare parts and their records and documents in my previous job.

• I am familiar with inventory management software and can use it to keep track of spare parts.

• I can create and maintain a database of spare parts, including their specifications, purchase dates, and maintenance history.

• I can also ensure that all necessary documentation, such as manuals and warranties, are properly ...read more