Senior Electrical Engineer Interview Questions UK: 8 Real Questions and What Interviewers Want

Applying for a Senior Electrical Engineer job in the UK? Here is what you are likely to be asked. These questions come from our Senior Electrical Engineer question bank of 16 questions, written for UK employers at senior level.

Eight Senior Electrical Engineer interview questions, and what the interviewer is thinking

1. How do you size a cable for a new three-phase distribution circuit, and which factors can catch out a less experienced designer?

Why they ask: They want to see that you apply BS 7671 methodically rather than picking a size from experience.

2. How do you carry out a protection coordination or discrimination study, and what are you trying to achieve?

Why they ask: Senior engineers are expected to ensure faults clear selectively without losing healthy parts of the network.

3. What is involved in connecting a new generator or battery storage system to the distribution network, and what do G98 and G99 mean?

Why they ask: Grid connection is a regular task, and they want to know you understand the process and the compliance rules.

4. How would you select and size a transformer and standby generator for a commercial building?

Why they ask: This tests your grasp of load assessment, diversity and the practical selection of power plant.

5. What is arc flash, and how would you reduce the risk in a switchboard design?

Why they ask: They are checking that you design out hazards, which is central to a senior engineer's duty under the regulations.

6. The DNO tells you the capacity for your client's EV charging scheme is only half of what was requested, and the programme is already tight. What do you do?

Why they ask: They want to see commercial and technical problem solving under constraint.

7. Tell me about a time you led the electrical design on a complex project and had to balance technical, cost and programme pressures.

Why they ask: They want evidence you can take ownership of a design at senior level.

8. What does a typical week look like for a senior electrical engineer, and what do you enjoy most about it?

Why they ask: They want to see you understand the breadth of the role beyond pure design.

A sample answer to question 1

How do you size a cable for a new three-phase distribution circuit, and which factors can catch out a less experienced designer?

I start with the design current, then choose the protective device rating. Next I apply the correction factors from Appendix 4 of BS 7671: ambient temperature, grouping, thermal insulation and the installation method, such as clipped direct, tray or buried duct. That gives the minimum tabulated current-carrying capacity. I then check voltage drop against the limits, and for long runs this often drives the final size rather than current capacity. After that I verify the fault current withstand using the adiabatic equation, checking the cable survives until the device clears, and confirm earth fault loop impedance so disconnection times are met. The traps I watch for are harmonic loading, which can make the neutral carry significant current, ignoring grouping with neighbouring circuits, and forgetting that soil thermal resistivity changes buried cable ratings. I document assumptions in the calculation so a checker can follow them, and I would use design software such as Amtech or ETAP to confirm the results.

Common mistake to avoid: Sizing on current capacity alone; failing to document assumptions

Want the rest?

Full model answers, key points and common mistakes for all 16 questions are on the Senior Electrical Engineer interview questions page. The first five are free, no sign-up needed.