Electrical Engineer Interview Questions for International Candidates: Power Systems, Circuits and Data Centers

The per-unit, fault, protection and data-center questions EE interviewers ask, with honest answers to the sponsorship, PE and U.S.-person questions on OPT.

Electrical engineer interview questions for international candidates fall into four technical tracks: power systems (per-unit math, fault analysis, protection and substations), circuits and power electronics, controls, and data-center electrical design. Most loops also include three visa-linked questions: will you need sponsorship, are you a "U.S. person" for export control, and where do you stand on the FE and PE. Short answers, as of November 1, 2026: answer the sponsorship question honestly, F-1 and H-1B holders are not U.S. persons, and a PE license is not a general H-1B requirement.

Status line, as of 2026-11-01: OPT unemployment limits are in effect and unchanged (90 days on OPT, 150 in aggregate on STEM OPT). Proclamation 11069 is in effect on paper, but its $100,000 H-1B payment is blocked: two federal courts set aside the agency policies that implement it, both rulings are on appeal, and USCIS is not collecting it. Demand is real: in Indeed Hiring Lab's October 22, 2026 snapshot, the data-center postings index stood at 247 (June 2024 = 100) and Engineering at about 145 (February 2020 = 100).

What electrical engineer interview questions should you expect?

Most electrical engineering technical interviews test fundamentals through one hand calculation, one diagram walkthrough and one project deep dive. Utilities and consultancies lean on per-unit fault math and protection. Data-center builders ask about redundancy and the power path from utility feed to rack. Electronics and controls teams ask about converters, op-amps and feedback loops.

Read the posting for clues to the track (standards named, voltage classes, "P&C", "critical facilities").

For firmware or board-level roles, see our guide to hardware and embedded technical interviews; chip design loops are not covered here.

Power systems engineer interview questions

Power interviews usually run per-unit, then fault analysis with symmetrical components, then protection. Interviewers care less about memorized formulas than about whether you pick a base, convert cleanly and notice an impossible answer.

Per-unit and fault analysis

• Why use per-unit values? With base voltages set by the turns ratio, the ideal transformer drops out, and impedances fall in narrow ranges, so a wrong number stands out.
• Change an impedance to a new base. Z(new) = Z(old) × (kV old / kV new)² × (MVA new / MVA old).
• Which sequence networks do you connect for each fault? Single-line-to-ground: all three in series. Line-to-line: positive and negative in parallel. Double-line-to-ground: all three in parallel.
• Is a three-phase fault always the worst case? No. A ground fault can exceed it where zero-sequence impedance is lower than positive-sequence, as at the solidly grounded wye side of a delta-wye transformer.
• What does the X/R ratio change? DC offset, asymmetrical peak current and breaker duty.
• What drives real and reactive power flow? Real power follows the angle difference (P = V1 × V2 × sin δ / X); reactive power follows the voltage-magnitude difference.
• Name the load-flow bus types. Slack, PV and PQ, and why Newton-Raphson is the usual solver.

A worked fault example interviewers love

A 50 MVA, 115/13.8 kV transformer has 10% impedance on its own base, fed from an infinite source. What is the bolted three-phase fault current on the 13.8 kV bus?

1. Fault current in per unit = 1 / 0.10 = 10 pu.
2. Base current at 13.8 kV = 50,000 kVA / (√3 × 13.8 kV) ≈ 2,092 A.
3. Fault current ≈ 10 × 2,092 ≈ 20.9 kA, a fault level of 500 MVA.

The usual follow-up: "Now the utility source is 2,000 MVA at 115 kV." On a 100 MVA base, the source is 100 / 2,000 = 0.05 pu and the transformer 0.10 × (100 / 50) = 0.20 pu, so the total is 0.25 pu. Base current at 13.8 kV is now about 4,184 A, giving about 4,184 / 0.25 ≈ 16.7 kA. Say out loud that the finite source lowered the current, and that 4,184 / 0.20 returns the same 20.9 kA, so the choice of base never changes the answer in amperes. That narration is what gets scored.

Protection and relaying

• Explain ANSI devices 50/51 (overcurrent), 67 (directional), 87 (differential) and 21 (distance), and where each applies.
• How do you coordinate a feeder relay with an upstream transformer relay? Time-current curves, a coordination time interval, and a pickup above maximum load but below minimum fault.
• Why does a transformer differential need harmonic restraint? Inrush is rich in second harmonic; fifth-harmonic restraint covers overexcitation.
• How do distance zones work? Zone 1 underreaches (commonly 80 to 90 percent of the line) and trips instantly; Zone 2 overreaches with a delay; Zone 3 is remote backup.
• What is CT saturation, and how can it make a relay misoperate?

Substation engineer interview questions

• Compare single bus, ring bus and breaker-and-a-half arrangements on reliability, maintenance access and cost.
• What are step and touch potential, and how does an IEEE Std 80 grounding design keep them within limits?
• Walk a substation one-line: where the CTs and PTs sit, what the 86 lockout relay does, and why the station DC battery system is critical.
• Physical design versus protection and control design, and IEC 61850 versus hardwired schemes.

Entry-level electrical engineer interview questions: circuits and power electronics

New-grad interviews test whether fundamentals are automatic. You should solve a Thevenin equivalent, an op-amp gain or a three-phase power problem without hesitating, then explain the physics in one sentence.

• Three-phase power: P = √3 × V(line-to-line) × I(line) × power factor; wye versus delta line and phase relationships.
• Why transmit at high voltage? Lower current for the same power, so lower I²R losses.
• Op-amps: inverting gain = −Rf / Rin; the ideal rules (virtual short, no input current) and where they fail (slew rate, bandwidth, output swing).
• RC circuits: after one time constant (τ = RC) a charging capacitor reaches about 63% of its final voltage.
• Converters: an ideal buck converter in continuous conduction has duty cycle D ≈ Vout / Vin; an ideal boost gives Vout = Vin / (1 − D). What sets inductor ripple current?
• Devices: MOSFET versus IGBT on switching speed, voltage class and conduction loss.
• Practical: why decoupling capacitors sit next to IC power pins; how power-factor-correction capacitors can cause harmonic resonance.

Controls engineer interview questions

• What do P, I and D each do? Proportional speeds the response, integral removes steady-state error but adds overshoot and windup risk, derivative adds damping but amplifies noise.
• What is integral windup, and two ways to prevent it (clamping, back-calculation)?
• Read gain margin and phase margin off a Bode plot, and explain what each protects against.
• Why does dead time limit how aggressively you can tune a process loop?
• Write a start/stop seal-in rung in ladder logic; explain SCADA polling and, for utilities, DNP3.
• For generation roles: governor droop and the automatic voltage regulator.

Data center electrical engineer interview questions

Data-center interviews center on one question: how does power get from the utility to the rack, and what happens when any piece fails? Our guide to data-center jobs with H-1B sponsorship covers who is hiring.

• Walk the one-line: utility medium-voltage service, MV switchgear, step-down transformers, low-voltage switchgear, UPS, PDUs and remote power panels, then rack PDUs.
• Redundancy: N, N+1, 2N and distributed redundant ("four to make three"), with the trade-offs in capital cost, utilization and single points of failure.
• Tiers: Uptime Institute Tier III (concurrently maintainable) versus Tier IV (fault tolerant).
• Outage sequence: the UPS carries the load on batteries or flywheels, generators start, an ATS or paralleling switchgear transfers the load, and the system retransfers once utility power is stable.
• Generator sizing: kW versus kVA, step loading, UPS input harmonics, cooling load, standby versus prime ratings.
• Studies and testing: selective coordination, arc flash (IEEE 1584, NFPA 70E), harmonics (IEEE 519), load-bank and integrated systems testing.
• Trend question: how higher rack densities and liquid cooling change distribution.

Visa questions in electrical engineering interviews (as of 2026-11)

Sponsorship, export control and licensure questions sound alike but ask different things.

For wording the first answer, see how to answer "do you need sponsorship" in an interview. On the second, the ITAR definition at 22 CFR 120.62 says a U.S. person is "a person who is a lawful permanent resident as defined by 8 U.S.C. 1101(a)(20) or who is a protected individual"; an EAD does not change that. Our explainer on the export-control "U.S. person" question covers what an honest "no" rules out, which matters most in defense electronics.

Does a power engineer need a PE license for H-1B?

Usually not at entry level. 8 CFR 214.2(h)(4)(v)(C)(1) says "a state may allow an individual without licensure to fully practice the occupation under the supervision of licensed senior or supervisory personnel in that occupation." USCIS then examines the duties and the petitioner's evidence of the supervisor's identity, physical location and credentials. Under paragraph (h)(4)(v)(A), when an occupation requires a state license to fully perform its duties, the beneficiary must hold it before approval. Whether a role that seals drawings as engineer of record falls there depends on state law and the actual duties, so that question belongs with the employer's immigration attorney.

Interviewers still ask, because the PE drives promotion. Answer with dates: "I passed the FE Electrical and Computer exam in May; I'll sit for PE Power once my state board says my experience qualifies." NCEES lists the PE Power exam as computer-based and offered year-round at Pearson test centers, and describes the FE exam as "designed for recent graduates and students who are close to finishing an undergraduate engineering degree." Our civil engineering PE and H-1B guide lays out a licensing timeline that maps closely onto power roles.

Common misconception: "No one will sponsor me until I have a PE." Correction: the specialty-occupation test turns on the degree and the duties, and 8 CFR 214.2(h)(4)(v)(C) lets USCIS grant H-1B status for supervised practice where the state allows it. The supervised experience a PE requires can be earned while on OPT, STEM OPT or H-1B; your state board decides what counts.

How do utilities decide whether to sponsor H-1B?

Employer by employer: some sponsor and many do not. Investor-owned utilities, public power agencies, consultancies, switchgear makers and data-center developers each set their own policy, sometimes department by department. Our breakdown of where electrical engineering H-1B filings come from maps the employer types.

Two facts matter as of 2026-11-01. Wage-weighted H-1B selection has been in effect since 2026-02-27, so a registration at wage Level I carries one entry against four at Level IV. In our reading, that lowers a new graduate's lottery odds and can factor into whether an employer registers one at all. And if a hiring manager raises the $100,000 payment, the USCIS I-129 page (updated 2026-10-30) says a court "vacated agency guidance implementing the $100,000 payment requirement," and that DHS still plans to collect the payment if that order is lifted. USCIS's H-1B guidance (dated 2026-09-21) says change-of-status requests it grants inside the US, the usual OPT-to-H-1B route, were never covered; a denied change of status, or a petition asking for consular notification, would be covered if collection resumed. Point the employer to its immigration counsel rather than arguing the law yourself.

How to prepare for a power systems interview

An eight-step plan that also protects your OPT clock:

1. Confirm your OPT end date and unemployment-day count with your DSO, and keep your employer information reported on time as your DSO directs, so start-date answers are exact. The SEVP unemployment counter page explains that SEVIS counts each day "without employer information" from your actual OPT start date.
2. Search the USCIS H-1B Employer Data Hub for the employer's legal name (the petitioning entity can differ from the brand), or query by city, state and NAICS industry code, to see recent filings.
3. Download the latest LCA disclosure file from DOL OFLC's performance data page (FY2026 Q3, through 2026-06-30) and filter by employer for job titles and worksites.
4. Rework the fault example above by hand, then repeat it as a single-line-to-ground fault with sequence networks.
5. Read the standards named in the posting: IEEE Std 80 for grounding, IEEE 1584 for arc flash, the IEEE C37 series for relaying.
6. Sketch a one-line diagram from your own project and rehearse a two-minute walkthrough.
7. Log in to MyNCEES and note your FE date, or schedule the FE Electrical and Computer exam, so your PE answer has dates.
8. Write your sponsorship and U.S.-person answers as one sentence each and say them aloud until they sound calm.

On STEM OPT, the USCIS STEM OPT page requires an employer enrolled in E-Verify that completes and signs Form I-983, and training that "takes place at a site other than the employer's principal place of business" is allowed only if every training obligation, including a bona fide employer-employee relationship, is still met. Describe field-heavy substation or construction work and its locations accurately in that plan, and ask your DSO if you are unsure.

Common mistakes

• Giving a number without a sanity check. Say "about 17 kA, plausible for a 50 MVA unit", not just "16,735".
• Answering "yes" to "Are you a U.S. person?" because you hold an EAD. Work authorization and export-control status are different questions.
• Calling a PE an H-1B requirement, or promising a PE date. Your state board sets eligibility.
• Hiding the sponsorship need until the offer. A late "no" burns unemployment days, and the limit is 90 on OPT and 150 in aggregate on STEM OPT.

Frequently asked questions

What technical questions are asked in electrical engineering interviews?

Most loops include one hand calculation, one diagram walkthrough and one project deep dive. Power roles ask about per-unit values, fault types and relay protection, data-center roles ask about redundancy and the utility-to-rack power path, and electronics and controls roles ask about converters, op-amps and PID tuning. Questions about sponsorship and export control usually come up too.

Do utilities sponsor H-1B for electrical engineers?

Some do and many do not, and the decision is made employer by employer, not by industry. As of November 2026 the most reliable check is the employer's own record in the USCIS H-1B Employer Data Hub, which covers fiscal years 2009 through 2026 quarter 4, and in DOL's LCA disclosure files, plus a direct question to the recruiter.

Is a PE license needed for power engineers on H-1B?

Usually not at entry level. Under 8 CFR 214.2(h)(4)(v), in effect as of November 2026, the license must be held before approval only when the occupation requires one to fully perform the duties, and USCIS can approve an H-1B for supervised practice where the state allows it. Whether a role that seals drawings as engineer of record needs the license first depends on state law and the duties, so that question belongs with the employer's immigration attorney.

What questions come up for data center electrical roles?

Expect to draw the one-line from the utility service through switchgear, transformers, UPS and PDUs to the rack, to compare N+1, 2N and distributed redundancy, and to explain what happens in the seconds after a utility outage. Generator sizing, selective coordination, arc-flash studies and commissioning tests are common follow-ups.

How do I prepare for a power systems interview?

Rework a per-unit fault calculation by hand, review differential, overcurrent and distance protection, and practice a two-minute walkthrough of a one-line diagram from your own project. If you are on OPT or STEM OPT, confirm your dates and unemployment days with your DSO first, so your start-date and sponsorship answers are precise.

Sources

• 8 CFR 214.2, H-1B licensure and beneficiary qualifications (Cornell LII)
• 22 CFR 120.62, definition of U.S. person (Cornell LII)
• USCIS, Form I-129 page
• USCIS, STEM OPT extension
• USCIS, H-1B Employer Data Hub
• DOL OFLC, performance data and disclosure files
• SEVP, unemployment counter
• NCEES, PE Electrical and Computer and FE exam
• Indeed Hiring Lab, US labor market snapshot, October 2026

How we checked this: we read the regulations, USCIS, DOL, SEVP and NCEES pages above and Indeed's October 22, 2026 snapshot on November 1-2, 2026, checked the status of each policy statement as of November 1, 2026, and reworked each calculation by hand; the technical answers reflect standard power-engineering practice.

This is general information, not legal or tax advice; your own I-20, EAD and notices govern, so take F-1, OPT and SEVIS questions to your DSO and petition or status strategy to a licensed immigration attorney.

If you want help targeting power, controls or data-center roles where sponsorship is realistic and preparing for these loops, talk to F1Jobs.