Electrical Engineering Interview Questions 2026: Core Companies, DISCOMs and PSUs

Electrical and EEE graduates have the widest spread of employers of any core branch: switchgear and automation multinationals (ABB, Siemens, Schneider Electric, Hitachi Energy, GE Vernova), Indian majors (L&T Electrical and Automation, Havells, Polycab, CG Power, KEC), utilities (Tata Power, Adani Energy, Torrent), EPCs, and the EV industry from Tata and Mahindra to Ather and Ola. About 1.26 lakh students enrolled in 2024-25, 83,355 registered for GATE EE in 2025, and the placement rate is around 59%.

Electrical also has the largest government route of any branch. GATE feeds the power PSUs (NTPC, PGCIL, BHEL, NHPC, SJVN, NLC) and the oil PSUs, ESE offers 73 electrical posts in 2026, and every state DISCOM and TRANSCO runs its own assistant-engineer exam - TSSPDCL, APTRANSCO, UPPCL, KPTCL, TANGEDCO and MSEB among them - which together account for thousands of posts a year. Both routes end in a technical interview built on machines, power systems and protection, and that is what this guide prepares you for.

How the interview actually runs

The private route is an online test followed by one or two technical interviews and HR. Siemens Energy's test is 91 questions in 80 minutes across aptitude, verbal and domain sections; its interview asks about substation components, motor types, DC series motor speed control and the Buchholz relay. Schneider Electric runs an aptitude test and then a personal interview across power systems, protection, automation, machines and digital logic. ABB interviews lean on machines and protection; L&T and Tata Power lean on site electrical and plant operations. Bosch's EEE hiring is embedded-flavoured: microcontrollers and embedded C. Eligibility is usually 60-70% with no backlogs.

The technical panel opens with your project and then moves to a predictable core: transformer tests and vector groups, induction motor slip and starting, per-unit and fault calculations, power factor correction, circuit breaker types, earthing, PWM inverters and basic PLC ladder logic. Many panels ask you to draw a substation single-line diagram on the spot.

Government interviews come after the GATE score or the written exam. They are fundamentals-first personal interviews in front of utility or PSU engineers: transmission line parameters, protection schemes, distribution losses, safety regulations and your project, plus questions on the organisation itself. Recent GATE thresholds put NTPC, BHEL and PGCIL around 740-780 marks.

Electrical machines and transformers questions

Q (fresher): Why do you run open-circuit and short-circuit tests on a transformer? A: The open-circuit test on the LV side gives core loss and the magnetising branch; the short-circuit test on the HV side gives copper loss and the series impedance, so efficiency and regulation follow without a full-load test.
Q (fresher): What does the vector group Dyn11 mean? A: Delta-connected HV, star-connected LV with the neutral brought out, and the LV phasor leading the HV phasor by 30 degrees, which decides whether two transformers can be paralleled.
Q (fresher): What does a Buchholz relay do? A: A gas-actuated relay in the pipe between the tank and the conservator that alarms on slow gas accumulation from minor faults and trips on the oil surge of a major internal fault.
Q (fresher): Why does an induction motor draw high current at start? A: At standstill the slip is one, so the rotor circuit looks like a transformer with a shorted secondary; the starting current is typically five to seven times full-load current, which is why star-delta, autotransformer or soft starters are used.
Q (fresher): How is the speed of a DC series motor controlled, and why must it never run unloaded? A: By armature voltage, series resistance or field diversion; unloaded the flux collapses and speed rises dangerously because torque and flux both depend on the same current.
Q (experienced): What does IE3 versus IE4 mean when you specify a motor? A: IEC 60034-30 efficiency classes; IE3 is the premium level mandated for new motors in India, IE4 is super-premium, and the difference pays back through energy cost over the motor's life.

Power systems, protection and switchgear questions

Q (fresher): Why do we use the per-unit system? A: It normalises quantities across voltage levels so transformer ratios vanish and impedances of machines and lines become comparable, which simplifies fault and load-flow studies.
Q (fresher): What is the Ferranti effect? A: The receiving-end voltage of a long, lightly loaded line rising above the sending-end voltage because the line's capacitive charging current flows through its series inductance.
Q (fresher): What is the equal area criterion? A: A graphical transient-stability test: the machine stays in synchronism if the decelerating area available after the fault clears can match the accelerating area gained during the fault.
Q (fresher): What are the zones of a distance relay? A: Zone 1 covers about 80% of the line and trips instantaneously; Zone 2 reaches about 120% with a 0.3-0.5 s delay; Zone 3 backs up the adjacent line with a longer delay.
Q (fresher): How does differential protection work? A: It compares the current entering and leaving a zone and trips on the difference, with a bias slope so CT mismatch during a through-fault does not cause a false trip.
Q (fresher): How does an SF6 breaker quench the arc? A: Sulphur hexafluoride's high dielectric strength and electronegativity capture free electrons, and a puffer or self-blast action blows the gas across the arc at current zero.
Q (experienced): What is the earth-grid design check per IEEE 80 and IS 3043? A: Compute grid resistance and ground potential rise for the maximum earth-fault current, then verify that step and touch voltages are below the tolerable limits for the fault clearing time and surface layer.

Power electronics, drives and EV questions

Q (fresher): Why is PWM used in inverters? A: Switching the output at high frequency with a modulated pulse width pushes harmonics to multiples of the switching frequency, where a small filter removes them, while the fundamental amplitude is controlled by the modulation index.
Q (fresher): What is the difference between V/f control and vector control of an induction motor? A: V/f keeps flux constant by scaling voltage with frequency and is fine for fans and pumps; vector control decouples flux and torque currents for fast, precise torque response at low speed.
Q (fresher): Why do EV chargers distinguish AC and DC charging? A: AC charging feeds the vehicle's onboard charger, limited to a few kilowatts by its size; DC fast charging bypasses it and feeds the battery directly through the CCS2 connector at tens to hundreds of kilowatts.
Q (experienced): What does a BMS do beyond measuring cell voltage? A: State-of-charge and state-of-health estimation, cell balancing, thermal management commands, contactor control and fault isolation, with functional-safety requirements under AIS-156.

Control systems and measurements questions

Q (fresher): What does the Routh-Hurwitz criterion tell you? A: The number of sign changes in the first column of the Routh array equals the number of closed-loop poles in the right half-plane, so no sign changes means a stable system.
Q (fresher): What is gain margin? A: The factor by which the loop gain can rise before the closed loop becomes unstable, read at the phase-crossover frequency on the Bode plot.
Q (fresher): Why is a 4-20 mA loop used for transmitters? A: The live zero at 4 mA detects a broken wire, current is immune to line resistance and noise over long runs, and the loop can power the transmitter.
Q (fresher): What is the dielectric strength of air? A: About 3 kV/mm at atmospheric pressure, the figure behind clearance distances in switchgear.

PLC, SCADA, standards and design questions

Q (fresher): What is ladder logic? A: A graphical PLC programming language modelled on relay circuits, one of the five IEC 61131-3 languages, where rungs of contacts and coils execute in a scan cycle.
Q (fresher): What is the difference between PLC, DCS and SCADA? A: A PLC is a fast discrete controller for a machine or a skid; a DCS is a distributed system for continuous process control; SCADA supervises geographically spread assets over telemetry.
Q (experienced): How do you size a cable? A: From continuous current with derating for ambient temperature, grouping and installation method per IS 1255 and IEC 60364, then check voltage drop and short-circuit withstand for the fault clearing time.
Q (experienced): What does IEC 61439 form of separation mean? A: The degree of internal partitioning in an LV switchboard, from Form 1 with no separation to Form 4b where busbars, functional units and their terminals are all segregated.
Q (experienced): What are the IEEE 519 harmonic limits? A: Current distortion limits at the point of common coupling that depend on the short-circuit ratio, from 5% total demand distortion for a stiff supply below a ratio of 20 up to 20% above 1000, plus a voltage THD limit.
Q (experienced): How do you select a PV string length? A: So that open-circuit voltage at the coldest site temperature stays below the inverter's 1000 or 1500 V limit and maximum-power voltage at the hottest temperature stays above the MPPT minimum.

What experienced engineers get asked

Design and protection roles (2-10 years) are interviewed on single-line diagrams, cable schedules and derating, relay coordination and arc-flash studies in ETAP or DIgSILENT, earthing design per IS 3043 and IEEE 80, lightning protection per IEC 62305, substation automation per IEC 61850, panel design per IEC 61439, and the CEA safety regulations. Solar and storage designers add PVsyst, IEC 61215/61730 module standards and BESS sizing.

Plant and maintenance roles are interviewed on testing and commissioning: insulation resistance and polarisation index, tan delta, dissolved gas analysis, relay secondary injection, CT polarity; on condition monitoring with thermography and partial discharge; and on BEE energy audits and ISO 50001. Automation roles add DCS architectures, Modbus, Profinet and OPC UA, SIL determination under IEC 61508/61511, and FAT/SAT. Lead roles add CEIG approvals, tenders and O&M contracts.

The DISCOM and PSU interview

After a state DISCOM written exam or a GATE shortlist, the personal interview is run by practising utility engineers. Expect transmission line parameters and the Ferranti effect, protection schemes for feeders and transformers, distribution transformer sizing and losses, AT&C loss reduction, safety rules and electrical accident procedures, the Indian Electricity Grid Code and frequency limits, and your project. IOCL weights GATE 85% with the group discussion and interview at 15%; BHEL runs a three-member panel on fundamentals and plant questions.

A 4-week plan

Week 1: Circuit theory, electrical machines and power systems from the Electrical Core section, 40 questions a day; redraw the transformer equivalent circuit and a substation single-line diagram from memory.
Week 2: Power electronics, control systems and measurements; take the free 2-minute readiness check on your stream.
Week 3: Electrical Design section for protection, cable sizing, standards and PLC/SCADA if you target design or automation roles; Plant and Utility Ops for testing, maintenance and grid operations if you target plant, utility or PSU roles.
Week 4: Recruiter pages for Siemens, PGCIL and NTPC, timed aptitude, and two full mock interviews at your target level.

All of the questions above are drawn from placd's Electrical Engineering banks, about 1,050 questions across the core, design and plant sections with explanations. Start at the department hub, placd.in/engineering/electrical, browse topics such as placd.in/questions/ee-core/electrical-machines, placd.in/questions/ee-core/power-systems and placd.in/questions/ee-design/protection-and-switchgear, and sit the scored AI mock interview on Pro at placd.in/products/mock-interview (take the free readiness check first), with the interviewer asking from the electrical bank when you pick an electrical role.