LV (Low Voltage) Electrical Engineer interview questions

sajjad qayyum July 21, 2025

 


Here is a list of commonly asked LV (Low Voltage) Electrical Engineer interview questions along with sample answers, tailored for roles in Saudi Arabia, particularly in construction, O&M, and industrial sectors:

⚡ Technical Interview Questions & Sample Answers

1. What is the voltage range for LV systems in Saudi Arabia?

Answer:
In Saudi Arabia, LV systems typically operate at 230V (single-phase) and 400V (three-phase) with a frequency of 60 Hz, as per SEC and SASO standards.

2. Explain the difference between MCB, MCCB, and ELCB.

Answer:

  • MCB (Miniature Circuit Breaker): Protects against overloads and short circuits in small loads.

  • MCCB (Molded Case Circuit Breaker): Used for higher current ratings and offers adjustable trip settings.

  • ELCB (Earth Leakage Circuit Breaker): Detects leakage current to prevent electric shocks.

3. What is the purpose of earthing and how is it implemented in LV systems?

Answer:
Earthing ensures safety by diverting fault current to the ground. In LV systems in Saudi Arabia, TN-S or TT earthing systems are commonly used, and all metallic parts are grounded to protect personnel and equipment.

4. What are the standard cable colors used in Saudi Arabia for LV installations?

Answer:
According to Saudi standards (based on IEC):

  • Phase (L1, L2, L3): Brown, Black, Grey

  • Neutral (N): Blue

  • Earth (PE): Green/Yellow

5. How do you calculate the cable size for an LV circuit?

Answer:
Cable size is based on:

  • Load current

  • Length of cable

  • Voltage drop (usually limited to 3% for lighting and 5% for power)

  • Derating factors (ambient temperature, grouping, etc.)

  • Short circuit withstand capacity

Formula:
I=P3×V×cos⁡ϕI = \frac{P}{\sqrt{3} \times V \times \cos\phi}
Then use cable tables to select the proper size.

🏗️ Site-Specific / Saudi Market Questions

6. Are you familiar with SEC regulations and standards?

Answer:
Yes. I am familiar with Saudi Electricity Company (SEC) standards for LV/MV installations, especially the Distribution Construction Manual (DCM) and Standard Drawings for LV networks, which are mandatory for compliance in residential and industrial projects.

7. How do you ensure compliance with SASO and NFPA standards?

Answer:
By reviewing all designs and installations against:

  • SASO (Saudi Standards, Metrology and Quality Organization) requirements for equipment and safety.

  • NFPA 70 (NEC) for grounding, panel installations, and cable routing.

  • Coordination with QA/QC and HSE to ensure proper documentation and inspections.

🔧 Maintenance & Troubleshooting Questions

8. What steps would you take to troubleshoot a tripping MCB in a DB?

Answer:

  • Identify the circuit/load it serves.

  • Check for overloading or short circuit.

  • Measure current with a clamp meter.

  • Inspect connections and insulation.

  • Replace MCB if defective.

9. How do you perform insulation resistance testing?

Answer:
Using a Megger:

  • Disconnect equipment from supply.

  • Apply 500V or 1000V (as per system voltage).

  • Acceptable insulation resistance: >1 MΩ for LV circuits.

  • Test between phase–earth, phase–neutral, and phase–phase.

📄 General / HR Questions

10. Why do you want to work in Saudi Arabia?

Answer:
Saudi Arabia is undergoing rapid infrastructure growth under Vision 2030. I am eager to contribute my skills in LV systems in such a dynamic market and gain exposure to high-standard projects while enhancing my technical and cultural experience.

11. Can you work under pressure and in remote site locations?

Answer:
Yes. I have previously handled urgent electrical breakdowns and completed time-sensitive LV installations in harsh environments while maintaining safety and quality standards.

12. What software tools are you familiar with?

Answer:

  • AutoCAD for electrical layouts

  • ETAP / Ecodial for load calculations and protection coordination

  • Microsoft Excel for load schedules, BOQs

  • Dialux for lighting design (if relevant)

Here’s the continuation of LV Electrical Engineer Interview Questions & Answers relevant to Saudi Arabia, especially for industrial, commercial, and utility projects:

🧰 Project Execution & Safety Questions

13. How do you prepare a load schedule for an LV distribution system?

Answer:

  • List all loads (lighting, power outlets, HVAC, motors, etc.).

  • Group them into logical DBs (Lighting DB, Power DB, etc.).

  • Calculate individual and total load (in kW or kVA).

  • Apply diversity factor and power factor.

  • Convert to current and select appropriate MCB/MCCB/cables accordingly.

  • Ensure feeder breaker, cable sizing, and transformer sizing align with the final load.

14. What is the procedure for cable laying on-site?

Answer:

  • Check approved cable routing drawings and cable schedule.

  • Perform trench or tray inspection.

  • Lay cable with proper spacing and avoid sharp bends.

  • Apply cable tags and markers as per SEC or client standard.

  • Conduct megger test before and after cable laying.

  • Record and submit installation inspection and test reports.

15. What are the typical protections used in LV systems?

Answer:

  • Overcurrent Protection: MCB, MCCB

  • Earth Leakage Protection: RCCB, ELCB

  • Short Circuit Protection

  • Surge Protection Devices (SPD)

  • Over/Under Voltage Protection (especially for sensitive equipment)

🛠️ O&M (Operation & Maintenance) Specific

16. What maintenance activities are required for LV panels?

Answer:

  • Visual inspection for discoloration, rust, or loose terminals.

  • Thermal scanning (IR) to detect overheating.

  • Tightening of all terminal connections.

  • Megger testing for insulation quality.

  • Cleaning of panels and verifying correct labeling.

  • Functional testing of breakers and protection relays.

17. How do you manage spare parts and preventive maintenance?

Answer:

  • Maintain a spare parts inventory based on OEM recommendations and failure history.

  • Prepare a preventive maintenance schedule monthly, quarterly, and annually.

  • Log all maintenance activities in CMMS or Excel sheets.

  • Perform root cause analysis (RCA) for major faults and update PM plans accordingly.

📈 Documentation & Reporting

18. What documents do you prepare for project handover?

Answer:

  • As-built drawings

  • Megger and IR test reports

  • Cable test reports

  • Earth resistance test reports

  • Final inspection checklists

  • Operation & Maintenance (O&M) manuals

  • Commissioning reports

  • Warranty certificates

19. How do you handle inspection requests with consultants or SEC?

Answer:

  • Ensure work is completed as per ITP (Inspection & Test Plan).

  • Fill and submit RFI (Request for Inspection) form.

  • Prepare checklist, test reports, and drawings.

  • Escort the inspector during the visit and explain the work done.

  • Address punch list (if any) and close the comments promptly.

🧑‍💼 Behavioral / Soft Skills

20. How do you handle a delay due to missing materials on-site?

Answer:

  • Immediately notify the procurement/logistics team.

  • Use available spares or propose temporary workaround if approved.

  • Update project manager and reschedule affected activities.

  • Learn from the issue and improve future material tracking.

21. How do you ensure coordination with other services (HVAC, plumbing, civil)?

Answer:

  • Attend coordination meetings.

  • Overlay drawings with other services using AutoCAD.

  • Use color-coded drawings to identify and resolve clashes.

  • Adjust routing or request RFI if changes are required.

  • Maintain clear communication with all discipline leads.

✅ Final Interview Tips for Saudi Arabia (Especially with SEC, Aramco, or Royal Commission Projects)

  • Be familiar with SEC-DCM, SASO, and IEC standards.

  • Know the permit to work (PTW) and LOTO (Lockout/Tagout) systems.

  • Prepare to discuss previous project experiences and your role.

  • Be ready for practical questions like reading SLDs, control circuit diagrams, and fault diagnosis.

  • Show awareness of safety regulations, especially in high-temperature and dusty environments.

Absolutely! Let’s continue with more advanced LV Electrical Engineer interview questions—ideal for interviews in Saudi Arabia with companies like Aramco, SEC, NEOM, Royal Commission, or major EPC contractors.

🧮 Advanced Technical & Design Questions

22. How do you design and size an LV distribution board (DB)?

Answer:

  • Identify total connected load and apply diversity factors.

  • Break down the load into circuits: lighting, sockets, HVAC, etc.

  • Calculate current for each circuit using I=PV×cos⁡ϕI = \frac{P}{V \times \cos \phi}

  • Select MCBs based on load current + margin.

  • Choose MCCB for main incomer with proper frame size.

  • Ensure neutral and earth bar sizing matches conductor ratings.

  • Verify the busbar rating, IP rating, and type testing per IEC 61439.

23. Explain the procedure for performing an earth pit resistance test.

Answer:

  • Use the fall-of-potential method with an earth tester.

  • Insert two auxiliary rods (current and potential probe) in a straight line from the earth electrode.

  • Measure resistance and ensure it's within allowable limits (<1 ohm for sensitive equipment, <5 ohms for general systems in Saudi Arabia).

  • Maintain logs and repeat tests seasonally if required.

24. What are your steps for LV panel commissioning?

Answer:

  • Visual check of wiring, terminations, labeling, and enclosure.

  • Insulation resistance testing.

  • Functional check of breakers, control circuits, and indication.

  • Load balancing check (if applicable).

  • Verify earthing continuity.

  • Document and submit commissioning report to consultant/client.

🛡️ Protection & Coordination

25. What is discrimination in electrical protection, and how is it ensured?

Answer:
Discrimination (or selectivity) ensures only the faulty section trips, not the whole system.
Achieved by:

  • Graded settings of MCB/MCCB trip curves (Type B, C, D)

  • Time-current coordination studies using software like ETAP

  • Using cascading protection where upstream breaker supports downstream under fault.

26. What is a short circuit calculation and why is it important?

Answer:
Short circuit calculation determines fault current at various points.
Used to:

  • Size breakers (withstand Icu, Ics)

  • Choose cables (thermal & mechanical stress limits)

  • Ensure equipment survives fault condition.

Formula for 3-phase fault current (approx.):

Isc=VLL3×ZI_{sc} = \frac{V_{LL}}{\sqrt{3} \times Z}

Where Z = total impedance from source to fault point.

💻 Software & Digital Skills

27. Which software do you use for LV system design?

Answer:

  • ETAP or Ecodial – load flow, short circuit, protection coordination

  • AutoCAD – layouts and SLDs

  • Dialux / Relux – lighting design

  • Excel – load schedules, BOQs, cable sizing sheets

  • Revit MEP – 3D electrical modeling (in large-scale projects)

28. Have you worked with Building Management Systems (BMS) or Smart Panels?

Answer:
Yes. I’ve interfaced LV systems with BMS for:

  • Real-time monitoring of loads

  • Alarm & fault reporting

  • Energy metering and load shedding
    Smart panels with modbus/TCP/IP integration are used for energy optimization in modern facilities.

🧑‍🏭 Leadership / Team Management

29. How do you lead a team of technicians on-site?

Answer:

  • Assign daily tasks based on priority and manpower.

  • Conduct toolbox talks (TBT) and safety briefings.

  • Supervise installation, testing, and troubleshooting.

  • Ensure compliance with QHSE and client standards.

  • Motivate the team and resolve any site-level conflicts or challenges.

30. What challenges have you faced in Saudi projects and how did you overcome them?

Answer:

  • Extreme heat impacting outdoor work – scheduled night shifts and cooling stations.

  • Material delays – managed alternative sourcing and adjusted timelines.

  • Language barriers – used simple English and visual instructions for multicultural teams.

  • Client changes mid-execution – reissued revised shop drawings and communicated clearly with all stakeholders.

📎 Bonus: Aramco-Specific Questions (If Applying There)

31. Are you familiar with Aramco standards (SAES, SATIP, SAIC)?

Answer:
Yes. I’ve worked with:

  • SAES-P-111 / SAES-P-104 for LV electrical systems

  • SATIP for testing and inspection procedures

  • SAIC for checklists used during Aramco inspections
    I ensure that all materials and workmanship comply with Aramco Engineering Standards (AES) and pass final inspection without NCRs.

32. What are key documents required for Aramco electrical inspection?

Answer:

  • Approved IFC/Shop drawings

  • Cable schedules and termination charts

  • Megger test reports

  • Earth test reports

  • SAIC checklist filled and signed

  • Material approvals (MAF, MIR)

  • As-built documentation

Great! Let’s continue with additional real-world scenario questions, safety protocols, testing procedures, and Saudi-specific regulations relevant to LV Electrical Engineer interviews.

🧪 Testing & Commissioning – In-Depth

33. What are the types of tests performed on LV cables before energization?

Answer:

  1. Continuity Test – Verify phase and neutral continuity.

  2. Insulation Resistance Test (Megger) – Phase to Earth, Phase to Neutral, etc.

  3. High Voltage Test (Hi-Pot) – Usually for critical or long-distance cables.

  4. Polarity Test – Ensures correct terminal connections.

  5. Phase Sequence Test – Especially for motors and 3-phase loads.

  6. Loop Impedance Test – Checks fault path resistance.

34. What is a Megger test and how do you interpret its values?

Answer:
A Megger applies a high DC voltage (typically 500V or 1000V) to measure insulation resistance.

Acceptance values:

  • >1 MΩ for general LV circuits (as per IEC)

  • >2 MΩ or more for sensitive systems (Aramco/SEC might require higher)

  • Any reading <1 MΩ indicates possible insulation deterioration or moisture ingress.

35. What are the procedures for DB (Distribution Board) testing and commissioning?

Answer:

  • Visual inspection (wiring, labels, tightness, phase sequence)

  • Insulation resistance test

  • Functional testing of breakers

  • Load balancing verification

  • Earthing continuity test

  • Interlock and shunt trip test (if present)

  • Phase rotation confirmation (for 3-phase DBs)

🧯 HSE (Health, Safety, and Environment)

36. What are the main electrical hazards in LV systems?

Answer:

  • Electric Shock

  • Arc Flash

  • Short Circuit

  • Fire due to Overload or Faulty Wiring

  • Trip Hazards from Loose Wires

  • Improper Earthing

37. What are your responsibilities as an LV engineer under Saudi safety regulations?

Answer:

  • Ensure compliance with Saudi Labor Law, SFDA, SCECO, and NEOM/ARAMCO safety rules.

  • Always follow LOTO (Lockout-Tagout) during maintenance.

  • Conduct risk assessments and issue Work Permits (PTW) before starting job.

  • Wear full PPE and ensure all tools are calibrated and insulated.

  • Conduct toolbox talks (TBT) and safety drills with technicians.

📄 Documentation & Quality Assurance

38. How do you prepare a Method Statement for LV cable installation?

Key Contents:

  • Scope of work

  • Materials & tools required

  • Pre-installation checks (tray/conduit inspection, cable tags)

  • Cable pulling method

  • Bending radius & spacing

  • Megger testing before and after laying

  • Safety precautions

  • QA/QC checklist

39. What is an ITP and why is it important?

Answer:
ITP (Inspection & Test Plan) outlines:

  • Activities to be inspected

  • Responsible parties (QC, consultant)

  • Frequency of inspection

  • Acceptance criteria

  • Relevant documents (drawings, standards)
    It ensures quality control and traceability in every phase of execution.

40. What is an RFI and when do you raise it?

Answer:
An RFI (Request for Inspection/Information) is raised:

  • Before conducting any inspection activity

  • When there is a design clash or unclear instruction

  • To request consultant/client approval
    You attach relevant drawings, ITP reference, and test results with the RFI.

🏗️ Practical Jobsite Scenarios

41. The main breaker is tripping frequently—what steps do you take?

Answer:

  • Check load current vs breaker rating.

  • Look for short circuit or earth leakage in circuits.

  • Measure current with clamp meter phase-wise.

  • Inspect for loose terminals or faulty breakers.

  • Divide load across multiple circuits if overloaded.

42. If a motor runs in reverse after installation, what could be the issue?

Answer:
It’s likely due to wrong phase sequence. Swap any two phases to correct rotation.

43. How do you handle client rejection due to wrong cable terminations?

Answer:

  • Apologize professionally and accept the feedback.

  • Re-check terminations as per the cable schedule and single line diagram.

  • Re-terminate using proper crimping tools and lug sizes.

  • Request re-inspection with test results attached.

  • Conduct toolbox talk to prevent recurrence.

44. Describe how you perform load balancing in a 3-phase panel.

Answer:

  • Use clamp meter to measure phase currents.

  • Move single-phase circuits between phases to distribute load evenly.

  • Ideal difference between phases: <10–15%

  • Re-label circuits and update load schedule accordingly.

🧩 Real-World Troubleshooting Scenarios

45. A lighting circuit trips every evening. How do you troubleshoot it?

Answer:

  • Check time correlation — suspect overload during evening peak.

  • Inspect for moisture ingress (especially for outdoor lighting).

  • Measure load current vs MCB rating.

  • Check for damaged wires, loose terminals, or shared neutral.

  • Perform insulation resistance test on the circuit.

  • Replace faulty fixtures or isolate affected branch.

46. How do you identify a loose neutral fault in an LV system?

Answer:

  • Symptoms: flickering lights, voltage fluctuation, overheating in neutrals.

  • Measure neutral-to-earth voltage—should be ~0V. If not, suspect loose neutral.

  • Open panel and inspect for burned/loose connections.

  • Tighten terminations or replace damaged busbars/lugs.

47. How do you handle voltage drop in long cable runs?

Answer:

  • Calculate voltage drop using:

    Vd=2×L×I×R1000V_d = \frac{2 \times L \times I \times R}{1000}

  • Mitigation:

    • Use larger cable size

    • Reduce cable run length if possible

    • Use higher voltage level (e.g., step-up/step-down at load end)

    • Use aluminum instead of copper only if allowed and economical

🌍 Energy Efficiency & Smart Tech

48. What are some ways to improve energy efficiency in LV systems?

Answer:

  • Use LED lighting with motion sensors

  • Install power factor correction capacitors

  • Apply load scheduling via timers or BMS

  • Reduce standby power losses

  • Conduct regular IR scans and maintenance to avoid losses

  • Monitor energy using smart metering and data analytics

49. Are you familiar with energy metering and load monitoring?

Answer:
Yes. I’ve worked with:

  • Digital energy meters (Modbus enabled)

  • Demand side management tools

  • Remote load monitoring via SCADA or BMS

  • Generated reports for power usage, load factor, and harmonics
    Useful for detecting abnormal usage and optimizing power consumption.

📡 Modern Practices & Integration

50. How do you integrate solar (PV) systems with LV panels?

Answer:

  • Solar inverter feeds into main panel via breaker

  • Must include:

    • AC & DC isolators

    • Anti-islanding protection

    • Synchronization with grid (on-grid systems)

  • Protection via SPD, fuses, and overcurrent breakers

  • Metering for exported/imported power as per SEC Net Metering regulations

51. What are your experiences with KNX, DALI, or smart home systems?

Answer:

  • Used KNX for smart lighting and HVAC integration in villas

  • Implemented DALI systems for lighting automation in commercial buildings

  • Familiar with integrating with BMS through gateways

  • Able to program lighting scenes and schedules for energy savings

🧑‍🔧 Hands-on Installation Checks

52. What are key things to check before energizing an LV panel?

Answer:

  • Panel earthing continuity

  • Megger test passed

  • Phase sequence and voltage checks

  • Proper labeling and circuit identification

  • No loose wires or unused open terminals

  • Breakers in OFF position before switching ON incomer

53. How do you identify phase loss in a 3-phase motor system?

Answer:

  • Use motor protection relay with phase failure detection

  • Visual signs: motor humming, not starting, overheating

  • Check L1, L2, L3 voltages

  • Inspect contactor terminals and cable connections

  • Replace fuse/breaker or re-terminate as needed

📋 Saudi-Specific Project Requirements

54. What are the SEC submittal requirements for LV connections?

Answer:

  • Approved shop drawings (SLD, load schedule, layout)

  • BOQ with SASO/SEC-approved materials

  • Load demand sheet

  • Test reports (IR, earth resistance)

  • As-built drawings

  • Inspection Request (IR) with date/time for site visit

55. What are the basic requirements for electrical rooms as per SEC?

Answer:

  • IP55-rated panels if exposed to dust

  • Adequate ventilation or exhaust fans

  • Anti-static flooring (for sensitive areas)

  • Emergency lighting and fire extinguisher

  • Proper clearance around panels (usually ≥1m in front)

  • Danger and warning signs in Arabic/English

56. What is your understanding of “Aramco Loop Folder”?

Answer:

  • A Loop Folder includes:

  • Loop diagram
  • Cable schedule
  • Termination detail
  • Test sheets (loop test, insulation, continuity) Instrument datasheet
  • Used for control systems and is part of final handover documentation.

🧠 Behavioral / HR-Type Interview Questions

57. Tell me about a time you had a conflict with a supervisor or client. How did you handle it?

Answer:

  • Be honest but professional.
  • Example: "A consultant rejected our LV panel installation due to incorrect breaker labeling. I respectfully acknowledged the concern, corrected the issue with the site team, double-checked all other panels, and requested a re-inspection — which we passed. The client appreciated our prompt response."

58. How do you prioritize tasks when multiple deadlines clash?

Answer:

  • Assess which task impacts safety or critical path first.
  • Use tools like Gantt charts or daily job tracking sheets.
  • Coordinate with other departments to optimize manpower.
  • Communicate early with supervisors if adjustments are needed.

59. Describe a successful project you worked on from start to finish.

  • Tip: Use STAR format (Situation, Task, Action, Result)
  • Example:
  • Situation: Commercial mall LV system in Riyadh.
  • Task: Lead the installation of 20 DBs, 10 km of cable, and lighting system.
  • Action: Supervised 10 electricians, ensured testing & QA documentation.
  • Result: Delivered before deadline with zero NCRs. Client awarded us extension for Phase 2.

60. Have you ever failed on a job? What did you learn?

Answer:

  • Be honest but focus on what you learned.
  • Example:
  • “During early career, I approved cable pulling before duct inspection, which led to rework. Since then, I always verify pre-checklists and never skip quality steps, even under pressure.”

🧾 Certifications, Codes & Approvals

61. Are you certified with the Saudi Council of Engineers (SCE)?

Answer:

  • Yes (if applicable). If not:
  • "I am in the process of upgrading my profession and SCE registration for compliance with Saudi labor law. I have all documents ready."

62. Are you familiar with SASO requirements?

Answer:

  • Yes. SASO (Saudi Standards, Metrology, and Quality Org.) ensures that:
  • All electrical products (cables, DBs, switches, etc.) are tested & certified.
  • We only use SASO-approved materials on SEC, Aramco, or NEOM projects.
  • Also handle GSO conformity for imported items.

63. What codes do you follow for LV design in Saudi Arabia?

Answer:

  • IEC 60364 – General LV electrical installation standards
  • IEC 60947 – For switchgear
  • NEC (NFPA 70) – For hazardous areas
  • SEC DCM – For distribution connections
  • SAES – For Aramco-specific projects

🌐 For NEOM / Modern Projects

64. Have you worked with smart grids or digital panels?

Answer:

  • Yes (if applicable).
  • Experience with IoT-enabled DBs, remote metering, and load monitoring
  • Used Modbus/TCP-IP to link to BMS or cloud dashboards
  • Helps reduce downtime and allows predictive maintenance

65. How do you contribute to sustainable or green building initiatives?

Answer:

  • Designing energy-efficient lighting
  • Power factor correction for energy saving
  • Proper cable sizing to reduce losses
  • Integrating solar power with LV panels
  • Complying with LEED, SASO, or NEOM sustainability goals

✅                          ITEM
🔌                            Know key formulas: Voltage Drop, Load, Power Factor
🧪 Practice how to explain IR, Loop, and Earth Tests
📈 Understand load schedules and DB sizing
🧯 Be confident with HSE procedures and LOTO
📋 Memorize your role in QA/QC, ITPs, RFI, MIRs
🇸🇦 Learn Arabic technical terms (optional but helpful)
🪪 Bring copies of SCE Certificate, Iqama, Degree, and Site IDs
💬 Prepare 1–2 project stories for behavioral questions
📁 Carry portfolio of drawings, photos, or sample reports (digital or printed)
sajjad qayyum

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