Top 50 Medium Voltage Switchgear Interview Questions – Expert Q&A to Crack Electrical Jobs Fast
Preparing for technical interviews in the power sector requires more than theory. Recruiters look for practical knowledge, safety awareness, and real-world troubleshooting skills. This guide on medium voltage switchgear interview questions covers the most asked topics in utilities, substations, and industrial power systems. The answers are clear, practical, and focused on job readiness.
Table of Contents
Engineers who review these medium voltage switchgear interview questions gain confidence in protection, operation, maintenance, and testing concepts. The content also reflects common field scenarios faced by electrical professionals.
What Is Medium Voltage Switchgear?
Medium voltage switchgear is electrical equipment used to control, protect, and isolate electrical circuits operating typically between 1 kV and 36 kV. It includes circuit breakers, disconnectors, relays, busbars, and protection systems.
Interview panels often start with basics before moving to advanced medium voltage switchgear interview questions on protection schemes and fault analysis.
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Core Technical Medium Voltage Switchgear Interview Questions
Below is a structured table of frequently asked medium voltage switchgear interview questions with expert answers.
| No. | Question | Expert Answer |
|---|---|---|
| 1 | What is the purpose of medium voltage switchgear? | It controls, protects, and isolates MV electrical equipment during normal and fault conditions. |
| 2 | Define medium voltage range. | Typically from 1 kV up to 36 kV, depending on standards. |
| 3 | What are the main components? | Circuit breakers, busbars, CTs, PTs, relays, isolators, and earthing switches. |
| 4 | What is a vacuum circuit breaker? | A breaker that uses vacuum as the arc quenching medium. |
| 5 | Why is SF6 used in switchgear? | SF6 has excellent insulating and arc-quenching properties. |
| 6 | What is arc quenching? | The process of extinguishing the arc formed when contacts open. |
| 7 | What is busbar protection? | A protection scheme to detect internal bus faults quickly. |
| 8 | Difference between AIS and GIS? | AIS uses air insulation, GIS uses SF6 gas insulation. |
| 9 | What is a protection relay? | A device that detects faults and sends trip signals. |
| 10 | What is interlocking? | A safety system preventing incorrect operation sequence. |
These medium voltage switchgear interview questions often test both definitions and applied understanding.
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Protection and Safety Related Questions
Protection is a key area in medium voltage switchgear interview questions because safety and system reliability depend on it.
| No. | Question | Expert Answer |
|---|---|---|
| 11 | What is overcurrent protection? | Protection that operates when current exceeds preset value. |
| 12 | What is earth fault protection? | Detects leakage current flowing to ground. |
| 13 | What is differential protection? | Compares incoming and outgoing currents to detect internal faults. |
| 14 | What is arc flash? | A dangerous release of energy due to an electrical arc. |
| 15 | How do you prevent arc flash? | Proper maintenance, relays, arc detection, and PPE. |
| 16 | What is CT ratio? | Ratio of primary current to secondary current. |
| 17 | What is relay coordination? | Setting relays to operate in the correct sequence. |
| 18 | What is a trip circuit? | The circuit that energizes the breaker trip coil. |
| 19 | Why is earthing important? | It protects equipment and personnel during faults. |
| 20 | What is a lockout relay? | A relay that prevents re-closing until reset manually. |
Understanding safety adds strong weight to your answers in medium voltage switchgear interview questions.
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Operation and Maintenance Questions
Interviewers want candidates who understand field practices. These medium voltage switchgear interview questions focus on operation and upkeep.
| No. | Question | Expert Answer |
|---|---|---|
| 21 | What checks are done before energizing? | Insulation, wiring, interlocks, and protection settings. |
| 22 | What is preventive maintenance? | Scheduled inspection and servicing to avoid failures. |
| 23 | What causes breaker failure? | Coil issues, mechanical wear, or control circuit faults. |
| 24 | What is contact resistance test? | A test to measure resistance across breaker contacts. |
| 25 | What is insulation resistance test? | Measures insulation health using a megger. |
| 26 | Why lubricate moving parts? | To reduce wear and ensure smooth operation. |
| 27 | What is thermography used for? | Detecting hotspots in connections and busbars. |
| 28 | What is partial discharge? | Localized insulation breakdown without full flashover. |
| 29 | Why is cleaning important? | Dust and moisture reduce insulation strength. |
| 30 | What is breaker timing test? | Measures opening and closing time of a breaker. |
Practical exposure makes your responses stronger during medium voltage switchgear interview questions.
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Testing and Commissioning Questions
Testing knowledge is essential for engineers working with MV panels. These medium voltage switchgear interview questions often come in commissioning roles.
| No. | Question | Expert Answer |
|---|---|---|
| 31 | What is primary injection testing? | Injecting high current to test protection and CTs. |
| 32 | What is secondary injection testing? | Testing relays using simulated signals. |
| 33 | What is HV withstand test? | High voltage test to verify insulation strength. |
| 34 | What is polarity test of CT? | Ensures correct connection of CT terminals. |
| 35 | What is ratio test of CT? | Verifies CT transformation ratio. |
| 36 | What is functional testing? | Checking control logic and interlocks. |
| 37 | Why test trip circuits? | To ensure breaker trips during faults. |
| 38 | What is dielectric test? | Test to check insulation integrity. |
| 39 | What is continuity test? | Ensures wiring connections are complete. |
| 40 | Why record test results? | For future reference and maintenance history. |
Confidence in testing improves performance in medium voltage switchgear interview questions for commissioning jobs.
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Advanced and Scenario-Based Questions
Senior roles often include analytical medium voltage switchgear interview questions based on field faults.
| No. | Question | Expert Answer |
|---|---|---|
| 41 | What happens during busbar fault? | High fault current flows, protection trips instantly. |
| 42 | Why breaker fails to close? | Control voltage loss, spring not charged, or interlock active. |
| 43 | Why breaker trips repeatedly? | Persistent fault or wrong relay setting. |
| 44 | What is auto reclose? | Automatic reclosing after temporary fault clearance. |
| 45 | Difference between load break and fault break? | Load break handles normal current, fault break handles short circuit. |
| 46 | What is motorized switchgear? | Switchgear operated using electric motors. |
| 47 | What is remote operation? | Operating switchgear from control room or SCADA. |
| 48 | What is condition monitoring? | Tracking equipment health using sensors and data. |
| 49 | How do you handle SF6 leakage? | Detect, isolate, repair, and refill safely. |
| 50 | What is the role of SCADA in switchgear? | Monitoring, control, and alarm management. |
These advanced medium voltage switchgear interview questions test troubleshooting ability and system understanding.
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Final Preparation Tips
Reviewing medium voltage switchgear interview questions is most effective when combined with site experience, manuals, and protection drawings. Focus on safety procedures, lockout practices, and standard testing methods. Employers value engineers who understand both theory and field risk.
Practice explaining answers clearly and confidently. Many medium voltage switchgear interview questions are designed to see how you think under pressure, not just what you memorize.
Mastering these medium voltage switchgear interview questions will help you stand out in interviews for substations, power plants, utilities, and industrial facilities. Strong fundamentals, practical exposure, and safety awareness are the keys to cracking electrical jobs quickly. Use our online tool for free Sub Panel Breaker Size Calculator – Find the Right Breaker for Your Electrical Sub Panel
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