--- title: "Load estimate, supply features and sources" subject: "Industrial Power Distribution and Illumination" chapter: 1 key: "semester_6/industrial_power_distribution_and_illumination:load-estimate-supply-sources" source: https://www.bctengineer.com/q/semester_6/industrial_power_distribution_and_illumination/load-estimate-supply-sources site: BCT Engineering --- # Load estimate, supply features and sources Industrial Power Distribution and Illumination · Chapter 1: Introduction - Asked in: 2078 Chaitra, 2+2+4 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/load-estimate-supply-sources - Whole chapter: https://www.bctengineer.com/md/semester_6/industrial_power_distribution_and_illumination/chapter-1 ## Question Why Electrical Load Estimate is important in electrical installation? What are the key features of the supply system to industry? Explain different sources of supply to Industrial Plant. ## Short answer Load estimation determines maximum demand using demand/diversity factors to size transformers, cables, switchgear, set contract demand, and plan expansion. Key supply features: reliability, voltage regulation (±5%), correct frequency, adequate capacity, safety, flexibility, economy, and voltage matched to load size. Sources: utility grid (NEA), captive power, cogeneration, standby/emergency (DG, UPS), renewables, dual feeders. ## Answer #### Importance of electrical load estimate Load estimation finds the actual maximum demand of the installation from the connected load using demand and diversity factors (or ku and ks). It is important because: - It fixes the **size of transformer, generator, cables, busbars and switchgear**. Over-estimate wastes money and runs equipment at low efficiency; under-estimate causes overheating and tripping. - It sets the **contract demand** and tariff with the utility (NEA). - It is needed for **voltage drop, fault level and protection** calculations. - It allows planning for **future expansion** with a known margin. #### Key features of the supply system to industry 1. **Reliability and continuity:** process loads need supply with few interruptions; alternative sources or ring/selective schemes are used. 2. **Good voltage regulation:** voltage within about ±5% of rated, so motors give rated torque. 3. **Correct frequency** (50 Hz in Nepal) and a sinusoidal waveform with low harmonics. 4. **Adequate capacity** for present load plus future expansion. 5. **Safety:** proper earthing, protection and isolation. 6. **Flexibility:** easy to extend and to isolate parts for maintenance. 7. **Economy:** low first cost, low losses, good power factor. 8. **Supply voltage matched to the load size:** 400/230 V for small plants, 11 kV or 33 kV for medium and large plants, 66 kV or 132 kV for very large plants. #### Sources of supply to an industrial plant 1. **Utility grid (NEA):** the main source for most plants. Small industries get 400 V three-phase; larger ones take 11 kV or 33 kV and have their own substation. Cheapest and most reliable for normal running, but subject to load shedding and outages. 2. **Captive power plant:** the plant's own generator, such as a small hydro plant (common in Nepal for remote industries), a diesel generator set or a steam turbine. Used where grid supply is absent or unreliable. 3. **Cogeneration:** industries like sugar, paper and cement use process steam or waste heat (bagasse) to make electricity and heat together, and may sell surplus power to the grid. 4. **Standby/emergency sources:** diesel generator sets with automatic transfer switches, UPS and battery banks for critical loads (control systems, emergency lighting, computers). 5. **Renewable sources:** rooftop solar PV (grid-tied or with batteries), wind, biogas. They reduce the energy bill and dependence on the grid. 6. **Dual utility feeders:** two incoming feeders from different substations for high reliability. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. Why is load estimation important? A. It removes the need for any protection B. It increases the connected load C. It fixes the sizes of transformer, cables and switchgear and sets the contract demand D. It only decides the colour code Answer: C. Correct sizing avoids waste from over-estimate and overheating from under-estimate. (Key point: Importance of load estimate) 2. Which voltage regulation is expected for supply to industry? A. Within +/-25% B. Within about +/-5% of rated voltage C. Exactly zero variation D. Any value above rated Answer: B. Voltage must stay close to rated so motors give rated torque. (Key point: Key supply features) 3. What is cogeneration? A. Producing electricity and process heat together, e.g. using bagasse or waste heat B. Buying power from two utilities C. Storing power in a UPS only D. Using only solar panels Answer: A. Sugar, paper and cement plants use process steam or waste heat to make power and heat together. (Key point: Cogeneration) 4. Which sources serve critical loads when the grid fails? A. Larger transformers B. Capacitor banks C. Earth electrodes D. Diesel generators with automatic transfer switches, UPS and battery banks Answer: D. Standby sources supply critical loads such as control systems during outages. 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