MCQ Practice — Category 07
Cable & Wire MCQ
Cable types, color coding, sizing, insulation — IEC standard ke hisaab se cable knowledge test karo. 5 parts mein divide.
50 Questions
5 Parts
Easy → Hard
Hinglish Explanation
Select a Part to Practice
Part 01
Basics
Q 1–10
Easy
Start
Part 02
Types/Insulation
Q 11–20
Easy–Med
Start
Part 03
Sizing
Q 21–30
Medium
Start
Part 04
Standards
Q 31–40
Med–Hard
Start
Part 05
Gulf Site
Q 41–50
Hard
Start
Theory + Gulf Rules — Cable & Wire
Cable vs Wire – Basic Difference
Main Mohammad Arif – 12+ saal Gulf aur India ke electrical supervisor. Cable selection electrical installation ka backbone hai. Gulf projects mein cable ki cost aur quality dono critical hain – galat sizing se failures, overheating, aur fire risk ho sakta hai.
Wire: Single conductor (solid or stranded) – usually with one layer of insulation. Cable: Two or more insulated conductors bundled together with an overall sheath. But everyday conversation mein log dono ko interchangeably use karte hain.
Gulf Note: UAE, Saudi, Qatar mein BS 6724, BS 5467, IEC 60502 standards commonly use hote hain. Armoured (SWA) cables underground aur exposed areas mein mandatory hote hain.
Cable Types – Which One to Use?
| Type | Insulation | Max Temp | Use Case |
|---|---|---|---|
| PVC | Polyvinyl Chloride | 70°C | House wiring, general purpose |
| XLPE | Cross-Linked Polyethylene | 90°C | Power cables, higher rating |
| LSZH | Low Smoke Zero Halogen | 70-90°C | Public buildings, data centers, metro |
| FR/FRLS | Fire Retardant | 70°C | Fire alarm, emergency circuits |
Armoured vs Unarmoured
Armoured (SWA/AWA)
- SWA – Steel Wire Armour (for steel wire armoured cables)
- Mechanical protection – underground, exposed areas
- Rodent damage, impact resistance
- Common in Gulf for distribution
Unarmoured
- No metal armour layer
- Lighter, cheaper, easier to handle
- Indoor, protected environments
- Cable trays, conduits, false ceilings
Conductor Material – Copper vs Aluminium
- Copper: Higher conductivity (about 60% better), more expensive, higher weight, better reliability. Preferred for critical circuits.
- Aluminium: Lighter, cheaper, lower conductivity – so larger size needed for same current. Used for large power cables (cost savings).
- Gulf preference: Copper is more common for reliability, but aluminium is used for large main feeders to save cost.
Aluminium termination: Special bi-metallic lugs aur anti-oxidant paste use karo – aluminium oxidation issues hote hain joints mein.
Cable Sizing – Ampacity, Voltage Drop, Derating
Sizing Steps
1. Calculate load current – I = P/(√3×V×PF×Eff) for 3-phase
2. Select base ampacity – from manufacturer tables (PVC or XLPE)
3. Apply derating factors – temperature, grouping, installation method
4. Check voltage drop – V_drop = I×R×L, should be < 3-5%
5. Select next higher standard size
Installation Methods & Derating
- Free Air (in cable tray) – best cooling, highest ampacity.
- In Conduit / Trunking – reduced cooling, lower ampacity.
- Buried Directly – soil thermal resistance matters, different derating.
- Grouping – multiple cables together reduce cooling capacity.
- Ambient Temperature – Gulf (45°C+) needs derating (typically 0.85-0.9).
Standards – India, BS, IEC
| Standard | Region | Key Points |
|---|---|---|
| IS 694 | India | PVC insulated cables upto 1100V |
| IS 7098 | India | XLPE insulated cables |
| BS 6724 | UK/Gulf | LSZH cables for fire safety |
| BS 5467 | UK/Gulf | Armoured cables with PVC insulation |
| IEC 60502 | International | Power cables from 1kV to 30kV |
HV Cables (11kV/33kV) – What's Different?
- Semi-conducting layers – around conductor and insulation to control electric field stress.
- Metal screen/tape – for fault current path and to equalize potential.
- Thicker insulation – for higher voltage rating.
- Special jointing kits – field stress control is critical.
- Testing: Partial Discharge (PD), Tan Delta, Sheath testing – beyond basic IR.
Gulf Rule: HV cable jointing in Gulf requires approved contractor, trained technicians, and factory-made joints – field-made joints strictly controlled. DEWA/KAHRAMAA have specific approval requirements.
Cable Testing & Commissioning
- Insulation Resistance (IR) / Megger – Minimum 1 MΩ per kV (typical).
- Continuity Test – Each conductor continuity verify.
- High Voltage (HV) Test / VLF – For commissioning HV cables.
- Partial Discharge (PD) Test – Detects insulation defects.
- Sheath Integrity Test – For armoured/sheathed cables.
Gulf Interview – Cable Ke Sawaal
- Load ke hisaab se cable size kaise select karte hain? – Ampacity + voltage drop + derating.
- PVC vs XLPE difference? – Temperature rating, current capacity.
- Armoured cable kahan use hota hai? – Underground, exposed areas.
- Derating factor kab apply karte hain? – Temperature, grouping, conduit.
- Voltage drop calculation ka importance? – Long runs mein equipment performance.
- Colour coding standard? – Phase, Neutral, Earth colours.
Cable Size Calculator Use Karo
Load, length, voltage, temperature daalo – cable size aur voltage drop instantly milega.
VoltGuru.in — Cable & Wire MCQ — 50 Questions — Free for Gulf Electricians