--- title: "Substation site criteria and H-pole BOQ" subject: "Industrial Power Distribution and Illumination" chapter: 4 key: "semester_6/industrial_power_distribution_and_illumination:substation-site-boq-h-pole" source: https://www.bctengineer.com/q/semester_6/industrial_power_distribution_and_illumination/substation-site-boq-h-pole site: BCT Engineering --- # Substation site criteria and H-pole BOQ Industrial Power Distribution and Illumination · Chapter 4: Distribution Substation of Industrial Plant - Asked in: 2080 Chaitra, 8 marks - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_6/industrial_power_distribution_and_illumination/substation-site-boq-h-pole - Whole chapter: https://www.bctengineer.com/md/semester_6/industrial_power_distribution_and_illumination/chapter-4 ## Question Explain about site evaluation criteria of Substation. Also, prepare a Bill of Quantity of 11/0.4kV 50 kVA H-Pole Distribution Substation. ## Short answer Site must be near load centre, accessible with firm ground and safe surroundings. A typical 11/0.4 kV 50 kVA H-pole substation BoQ includes transformer, two poles, platform channels, arresters, fuses, AB switch, insulators, conductors, LT distribution box, cables, earthing sets, stay set, danger plate, concrete foundation and labour. ## Answer #### Site evaluation criteria for a substation 1. **Near the load centre**: reduces LT cable length, voltage drop, losses and copper cost. 2. **Access to the HT line**: close to the 11 kV feeder route so the HT tap is short. 3. **Accessibility**: road access for transporting the transformer and for maintenance and fire-fighting vehicles. 4. **Ground conditions**: firm, level, non-flooding land; low soil resistivity for good earthing. 5. **Safety**: away from fuel stores, chemicals, explosive areas, schools and crowded places; enough clearance from buildings and trees. 6. **Space**: enough area for the present equipment, future expansion, fencing and working clearance. 7. **Environment**: free from dust, corrosive fumes and salt spray (otherwise choose indoor type); good natural ventilation. 8. **Cost and legal issues**: land cost, right-of-way, approval of the utility and local bodies. 9. **Aesthetics and noise**: transformer noise and appearance in residential surroundings. #### Bill of quantities: 11/0.4 kV, 50 kVA H-pole substation (typical) | S.N. | Item | Unit | Qty | |---|---|---|---| | 1 | Distribution transformer 50 kVA, 11/0.4 kV, Dyn11, ONAN | No. | 1 | | 2 | PSC / steel tubular pole, 11 m | No. | 2 | | 3 | MS channel (100 × 50 mm) for transformer platform and cross-arms | Set | 1 | | 4 | 11 kV lightning arrester, 9 kV, 5 kA | No. | 3 | | 5 | 11 kV drop-out fuse unit with fuse links | Set | 3 | | 6 | 11 kV AB switch, gang operated, 200 A | Set | 1 | | 7 | 11 kV pin insulators with pins | No. | 6 | | 8 | 11 kV disc insulators with hardware | Set | 3–6 | | 9 | HT jumper conductor (ACSR Dog/Rabbit) | m | 30 | | 10 | LT distribution box with MCCB 100 A (or fuse units), busbars | No. | 1 | | 11 | LT cable 1.1 kV, 3½ core 35 mm² Al XLPE (transformer to LT box) | m | 15 | | 12 | LT shackle / spool insulators | No. | 8 | | 13 | Earthing sets (pipe/plate electrode, GI strip/wire, chamber) | Set | 3 | | 14 | GI earth wire 8 SWG | kg | 20 | | 15 | Stay set complete with stay wire and insulator | Set | 2 | | 16 | Danger plate and anti-climbing device | Set | 2 | | 17 | Bolts, nuts, clamps, lugs, connectors | Lot | 1 | | 18 | Concrete for pole foundation | m³ | 1.5 | | 19 | Labour, transport, testing and commissioning | Job | 1 | Three separate earths are provided: one for the transformer neutral, one for the transformer body and metal parts, and one for the lightning arresters. Quantities are typical and vary with the utility's standard drawing. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. Why should a substation be sited near the load centre? A. It shortens the 11 kV line to zero B. It removes the need for earthing C. It increases the short-circuit level D. It shortens LT cables, reducing voltage drop, losses and cost Answer: D. LT current is high, so short LT runs save copper and I2R loss. (Key point: Load centre siting) 2. Which ground condition is desirable for a substation site? A. Low-lying land for natural drainage collection B. Firm, level, non-flooding land with low soil resistivity C. High-resistivity rocky soil D. Soft reclaimed land near a river Answer: B. Low resistivity gives good earthing; non-flooding land protects equipment. (Key point: Ground conditions) 3. Which transformer and pole quantity are listed in the BOQ for the 50 kVA H-pole substation? A. One 50 kVA transformer on one pole B. Three 50 kVA transformers on four poles C. One 250 kVA transformer on three poles D. One 50 kVA Dyn11 transformer on two 11 m poles Answer: D. H-pole means two poles carrying a platform. (Key point: H-pole BOQ) 4. How many separate earths are provided and for what? A. One common earth for everything B. Three: transformer neutral, transformer body, and lightning arresters C. Two: HT line and LT line D. Four: one per phase and one for neutral Answer: B. Separate electrodes let protection work correctly and keep surge currents away from the neutral. 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