Question 1
Difficulty: medium
Can you walk me through how you would perform a load flow study for a new substation or network expansion project?
Sample answer
I’d start by confirming the objective of the study, whether it’s to verify normal operating conditions, check contingency performance, or support equipment sizing. Then I’d gather the network model, including one-line diagrams, transformer data, line impedances, generator limits, capacitor banks, and expected load profiles. I always validate the model first because bad input data leads to bad decisions. After that, I’d run base-case load flow in a tool such as ETAP, PSS/E, or DIgSILENT and review bus voltages, branch loading, transformer taps, and power factor. If I find violations, I’d test practical fixes like reconfiguring feeders, adjusting transformer taps, adding reactive support, or changing conductor sizes. I also look beyond the steady-state result and ask whether the solution is operationally realistic. In my experience, the best study is one that not only passes the numbers, but also gives operations a clear, easy-to-implement plan.
Question 2
Difficulty: medium
Describe a time when you had to troubleshoot a recurring voltage drop or power quality issue.
Sample answer
In a previous role, we had a recurring voltage drop complaint at the end of a feeder serving mixed commercial and motor loads. The issue was intermittent, which made it harder because the steady-state model did not fully explain it. I started by reviewing SCADA trends and then coordinated a site visit to capture actual measurements during peak demand. That helped me see that the problem was tied to a combination of motor starting, long feeder length, and a poor power factor during certain operating windows. I worked with the operations team to test a few options, including capacitor placement and revised switching sequences. We also adjusted the feeder operating configuration to reduce loading during the peak period. The complaint dropped significantly after that. What I learned was that power quality problems often need both data and field observation, not just a desktop study. I try to approach those issues with patience, because the first explanation is rarely the whole story.
Question 3
Difficulty: medium
How do you decide whether to use overhead lines, underground кабling, or a different network configuration for a project?
Sample answer
I look at the decision as a balance of technical performance, reliability, cost, maintenance, and environmental constraints. Overhead lines are usually more economical and easier to repair, but they can be more exposed to weather, right-of-way issues, and visual concerns. Underground cabling reduces exposure and can improve reliability in dense areas, but it comes with higher installation cost, thermal limitations, and more complex fault location and repair. I also consider the loading profile and future growth because a design that works today may become constrained in a few years. In some cases, a different network configuration, like a looped feeder or sectionalized radial system, gives the best combination of reliability and flexibility without overcommitting to the most expensive option. I like to present these tradeoffs clearly to stakeholders so the final choice reflects both engineering reality and business priorities. The right answer is rarely the cheapest one or the most technically elegant one alone.
Question 4
Difficulty: hard
What steps would you take to ensure a protection scheme is properly coordinated across a distribution or transmission system?
Sample answer
Protection coordination starts with understanding the system philosophy and the fault levels at each point in the network. I begin by collecting relay settings, breaker ratings, CT and VT ratios, transformer impedances, and any generator contribution that could affect fault current. Then I map the protection zones and confirm what each device is supposed to protect and what it should not trip for. From there, I review time-current coordination, pickup settings, and directional logic where needed. I also check that upstream and downstream devices maintain selectivity so the closest device clears the fault first. In more complex systems, I’ll simulate multiple fault scenarios to see how the scheme behaves during normal, backup, and contingency conditions. After the settings are prepared, I like to validate them with peer review and, if possible, commissioning tests. In my view, good protection design is about balancing speed, sensitivity, and selectivity so the system is both safe and stable when something goes wrong.
Question 5
Difficulty: easy
Tell me about a time you had to explain a complex engineering recommendation to a non-technical stakeholder.
Sample answer
I had to present a recommendation to replace an aging transformer before it failed, and the finance team was focused on the upfront cost. Rather than leading with technical details, I framed the issue around business risk: outage exposure, replacement lead time, and the operational impact of an unplanned failure. I used simple visuals to show how the transformer loading had changed over time and how thermal stress was increasing the probability of failure. I also compared the planned replacement cost against the likely cost of emergency procurement, downtime, and customer impact. That changed the conversation from “Can we postpone this?” to “How do we manage the risk responsibly?” I made sure to answer questions directly and avoid jargon unless it was necessary. The recommendation was approved, and the project moved forward on schedule. That experience reinforced for me that good engineering communication is not about simplifying the truth too much; it’s about translating technical risk into terms people can act on confidently.
Question 6
Difficulty: medium
How do you approach short-circuit analysis, and what do you look for in the results?
Sample answer
I approach short-circuit analysis as a design and safety check, not just a calculation exercise. First, I define the study cases and make sure the network model reflects the current operating configuration, source strength, transformer connections, and grounding methods. Then I calculate fault currents for the relevant fault types, including three-phase, line-to-ground, line-to-line, and double-line-to-ground where applicable. I compare the results against equipment interrupting ratings, bus withstand ratings, and relay pickup requirements. I also pay attention to how fault current changes under different generation or utility tie conditions, since those variations can affect protection margins. If the levels are too high, I look at options like impedance changes, current-limiting reactors, or breaker upgrades. If they are too low, I check whether protection sensitivity may be compromised. What I’m really looking for is a practical picture of how the system behaves under stress, so we can protect people and equipment without overdesigning the network.
Question 7
Difficulty: medium
Describe a situation where you had to balance reliability improvement with budget constraints.
Sample answer
I worked on a feeder improvement project where the original proposal called for a full rebuild, but the budget only supported a phased approach. Instead of treating that as a limitation, I broke the network into sections based on risk and impact. I looked at outage history, customer criticality, loading, fault frequency, and asset condition to identify where a targeted investment would produce the biggest reliability gain. We prioritized reconductoring a heavily loaded section, added sectionalizing points to improve restoration time, and replaced only the most problematic assets rather than the entire feeder. That approach did not solve everything at once, but it delivered a meaningful reliability improvement within the available budget. I also made sure the long-term plan was still visible so the work we did first would support future upgrades. I think that’s an important skill in power systems engineering: knowing how to create value in stages instead of waiting for the perfect funding package.
Question 8
Difficulty: hard
If you discovered that a model used for planning studies was giving inconsistent results, how would you investigate and fix it?
Sample answer
I would treat that as a model integrity issue first, not a software issue. My first step would be to compare the study assumptions against source documents like as-built drawings, commissioning records, SCADA data, and equipment nameplates. I’d check for common problems such as incorrect transformer taps, swapped phase connections, outdated line impedances, or duplicate loads. Then I’d isolate the inconsistency by running simplified cases and changing one variable at a time until I found the source of the mismatch. If the issue involved load representation, I would verify whether the model was using peak, average, or coincident demand correctly. I also like to involve someone familiar with the field conditions because local operating practices often explain odd results. Once I find the root cause, I update the model and document the correction so the same issue does not recur. I’ve found that maintaining model discipline is just as important as doing the study itself, because a reliable planning process depends on trustworthy data.
Question 9
Difficulty: medium
How do you handle working with operations, maintenance, and project teams when their priorities conflict?
Sample answer
I try to start by recognizing that each group is looking at the system from a different angle. Operations is focused on keeping the network stable today, maintenance is trying to reduce risk and workload, and project teams are balancing scope, schedule, and cost. When priorities conflict, I bring everyone back to the shared objective, which is usually safe and reliable operation with minimal disruption. I find it helps to use data rather than opinion: outage history, asset condition, loading trends, and risk ranking. If we’re debating a shutdown window or equipment replacement sequence, I’ll lay out the technical constraints clearly and propose options with tradeoffs instead of a single yes-or-no answer. I also make sure to listen carefully, because sometimes the best solution is one that I would not have suggested on my own. In practice, I’ve seen that collaboration improves when people feel heard and when decisions are explained transparently. Strong technical work matters, but strong coordination is what gets the work completed safely.
Question 10
Difficulty: easy
Why are you interested in power systems engineering, and what makes you a strong fit for this role?
Sample answer
I’m interested in power systems engineering because it sits at the intersection of analysis, practical problem-solving, and real-world impact. The work affects everything from customer reliability to equipment life to system safety, so the decisions really matter. What I enjoy most is taking a complex network issue, breaking it into manageable pieces, and finding a solution that works in the field, not just on paper. I think I’m a strong fit because I’m careful with data, comfortable using engineering tools, and disciplined about validating assumptions before I recommend a change. I also communicate well with both technical and non-technical teams, which is important in a role where study results need to turn into action. Just as importantly, I like being accountable for the outcome. I do not want to produce analysis that sits in a folder; I want to help design systems that are safer, more reliable, and easier to operate over the long term.
