Technical Knowledge & Core Engineering
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Q: What is the difference between MCB, MCCB, and RCCB?
A: MCB protects against overcurrent/short circuit in low-current circuits; MCCB handles higher current ratings and allows adjustable trip settings; RCCB detects leakage current to protect against electric shock. -
Q: Explain the difference between single-phase and three-phase systems.
A: Single-phase has one alternating voltage; three-phase has three voltages 120° apart, giving smoother power and higher efficiency. -
Q: How do you calculate cable size for a load?
A: By considering load current, permissible voltage drop, ambient temperature, short-circuit capacity, and derating factors using IEC or NEC standards. -
Q: What is the difference between earthing and grounding?
A: In IEC terms, “earthing” connects equipment to the earth for safety, while “grounding” connects to a reference potential point in the electrical system. -
Q: What is the function of a capacitor bank in a substation?
A: It improves power factor, reduces losses, and increases system efficiency. -
Q: What is a harmonic in electrical systems?
A: Harmonics are voltage or current distortions at multiples of the fundamental frequency, often caused by nonlinear loads like VFDs. -
Q: Explain difference between star and delta connection.
A: Star provides neutral point, lower phase voltage; delta has no neutral, higher line voltage, and is used for heavy loads. -
Q: How do you test transformer insulation resistance?
A: Using a megger at appropriate voltage (e.g., 1kV/5kV), following IEEE/IEC guidelines. -
Q: What is an IP rating?
A: Ingress Protection rating shows dust and water resistance, e.g., IP65 means dust-tight and protected against water jets. -
Q: Why is power factor important?
A: Low power factor increases losses and utility charges; correction improves efficiency.
Saudi Standards, Codes & Regulations
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Q: Which electrical codes are followed in KSA?
A: Saudi Building Code (SBC), Saudi Electric Company (SEC) standards, IEC standards, and sometimes NEC for specific cases. -
Q: What is SASO?
A: Saudi Standards, Metrology and Quality Organization — ensures compliance of equipment with national standards. -
Q: How do you ensure compliance with SEC regulations in project design?
A: By referencing SEC design manuals, approved equipment lists, and submitting designs for SEC approval before implementation. -
Q: What is the maximum allowable voltage drop in Saudi regulations?
A: Typically ≤3% for lighting and ≤5% for power circuits (per SEC and IEC standards). -
Q: How do you design systems for high ambient temperatures in KSA?
A: Use derating factors for cables, select higher temperature class equipment, ensure adequate ventilation, and choose desert-rated transformers.
Safety & Protection
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Q: What is lockout-tagout (LOTO)?
A: A safety procedure to ensure equipment is de-energized and locked before maintenance. -
Q: What are the basic PPE requirements for electrical work?
A: Insulated gloves, safety helmet, arc-rated clothing, face shield, and insulated shoes. -
Q: How do you select circuit breakers for motor protection?
A: Based on full-load current, starting current, trip characteristics, and manufacturer guidelines. -
Q: How do you prevent arc flash hazards?
A: Conduct arc flash studies, label panels, maintain safe working distances, and use PPE per NFPA 70E. -
Q: How do you ensure safe grounding in desert soil?
A: Use multiple ground rods, increase rod length, add chemical backfill, and test regularly.
Practical Applications & Troubleshooting
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Q: What is the first step when a motor trips frequently?
A: Check load conditions, motor temperature, protective device settings, and insulation. -
Q: How do you identify a cable fault?
A: Using time-domain reflectometers (TDR), insulation testers, or cable fault locators. -
Q: How do you test a relay?
A: With secondary injection test kits to verify operation at set points. -
Q: How do you determine generator capacity?
A: Based on total connected load, diversity factor, future expansion, and starting currents. -
Q: What is synchronization in generators?
A: Matching voltage, frequency, and phase before connecting to the grid or another generator.
Project & Maintenance
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Q: How do you prepare an electrical load schedule?
A: By listing all connected loads, diversity factors, demand factors, and summing total kW and kVA. -
Q: What is preventive maintenance in electrical systems?
A: Scheduled inspections, cleaning, lubrication, and testing to avoid failures. -
Q: How do you reduce downtime in industrial plants?
A: Use predictive maintenance, spare parts stock, trained technicians, and redundancy. -
Q: How do you select lighting for hazardous areas?
A: Based on explosion-proof ratings (Ex), gas group, and temperature class per IEC 60079. -
Q: How do you plan cable routing in large plants?
A: Avoid interference sources, follow SEC clearance rules, and use proper cable trays/conduits.
Behavioral & Situational
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Q: Describe a challenging electrical project you worked on.
A: (Candidate shares example, focusing on problem-solving, technical expertise, and teamwork.) -
Q: How do you handle conflict in a project team?
A: By listening, understanding both sides, and finding a technical or contractual solution. -
Q: How do you prioritize work during an outage?
A: Safety first, critical loads second, then restoring non-critical systems. -
Q: How do you handle working in extreme heat conditions?
A: Plan work in cooler hours, use heat-resistant PPE, hydrate, and take breaks. -
Q: How do you ensure documentation is always up to date?
A: Keep an as-built file, update after each change, and maintain digital backups.
Future & Innovation
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Q: What’s your experience with renewable energy in KSA?
A: (Candidate should mention solar PV, hybrid systems, and SEC grid integration.) -
Q: How do you integrate SCADA into electrical systems?
A: By selecting compatible RTUs/PLCs, ensuring communication protocols, and linking with control rooms. -
Q: What’s your experience with energy audits?
A: Measure consumption, identify inefficiencies, recommend corrective actions. -
Q: How do you keep up with latest electrical engineering trends?
A: Reading IEC updates, attending IEEE seminars, following SEC circulars. -
Q: Why should we hire you for an electrical engineer role in KSA?
A: (Candidate should align technical expertise, knowledge of KSA codes, and proven project success.)
Drawing & Design-Related Interview Questions
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Q: How do you read and interpret a single-line diagram (SLD)?
A: Identify main incoming supply, busbars, breakers, transformers, feeders, and protective devices, then follow the power flow. -
Q: What is the difference between a wiring diagram and a schematic diagram?
A: Wiring diagram shows physical connections/layout; schematic shows functional relationships without physical layout. -
Q: How do you verify that an electrical drawing complies with SEC standards?
A: Check against SEC design manuals, approved equipment specifications, and cable sizing tables. -
Q: What symbols are commonly used for breakers, transformers, and motors in electrical drawings?
A: (Candidate should mention IEC standard symbols: CB for breaker, circle with winding for transformer, M in circle for motor, etc.) -
Q: How do you check if the cable routing in drawings meets site conditions?
A: Compare with site layout, check clearances, avoid mechanical damage zones, and ensure accessibility. -
Q: What is an as-built drawing?
A: A revised drawing reflecting all changes made during construction, matching the final installation. -
Q: How do you prepare a cable schedule from a drawing?
A: List cable sizes, lengths, sources, destinations, tag numbers, and installation routes as per the SLD and layouts. -
Q: How do you interpret a panel schedule in drawings?
A: Understand breaker ratings, circuit assignments, load types, and phase distribution. -
Q: How do you use AutoCAD or Revit for electrical drawings?
A: For drafting SLDs, layouts, lighting and power plans, and coordinating with other trades. -
Q: How do you verify load balancing in a three-phase system from drawings?
A: Check panel schedules for equal distribution of load across phases. -
Q: How do you review shop drawings before approval?
A: Check dimensions, cable routes, component ratings, and compliance with design intent. -
Q: How do you coordinate electrical drawings with mechanical and civil drawings?
A: Use combined services drawings (CSD) or BIM to detect clashes and adjust routing. -
Q: What is the purpose of a lighting layout drawing?
A: Shows the location, type, and control of light fixtures to ensure proper illumination and compliance. -
Q: How do you prepare a grounding layout drawing?
A: Show earth pits, conductors, connections to equipment, and ensure compliance with SEC/IEC. -
Q: How do you interpret a control wiring diagram?
A: Follow the sequence of operation, identify control devices, and trace signal flow. -
Q: What is a riser diagram?
A: Vertical schematic showing how electrical systems connect across building floors. -
Q: How do you check voltage drop compliance from drawings?
A: Use cable lengths and sizes from drawings, calculate voltage drop, and compare to limits. -
Q: How do you identify circuit numbers from electrical plans?
A: Refer to panel schedules and match with plan symbols and notations. -
Q: How do you prepare a bill of quantities (BOQ) from drawings?
A: Measure quantities from layouts, list equipment, and apply standard specifications. -
Q: How do you mark revisions in an electrical drawing?
A: Use revision clouds, tags, and update the revision block with date and description.
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