--- title: "Lighting schemes: local, general, emergency" subject: "Industrial Power Distribution and Illumination" chapter: 7 key: "semester_6/industrial_power_distribution_and_illumination:lighting-schemes-local-general-emergency" source: https://www.bctengineer.com/q/semester_6/industrial_power_distribution_and_illumination/lighting-schemes-local-general-emergency site: BCT Engineering --- # Lighting schemes: local, general, emergency Industrial Power Distribution and Illumination · Chapter 7: Illumination Design Principles - Asked in: 2079 Chaitra, 4+4 marks; 2075 Bhadra, 8 marks (asked 2 times) - Video: [factory lighting in illumination | factory lighting design | local lighting | general | in hindi](https://www.youtube.com/watch?v=-ndEWy2YHDY) — Mind of Engineer - 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/lighting-schemes-local-general-emergency - Whole chapter: https://www.bctengineer.com/md/semester_6/industrial_power_distribution_and_illumination/chapter-7 ## Question State various types of lighting schemes. Explain local lighting, general lighting and emergency lighting used in an industry. ## Short answer Lighting schemes are classified by distribution (direct, semi-direct, etc.) and coverage (general, local, emergency). General lighting provides uniform illumination over the whole floor. Local lighting concentrates high illuminance on small work areas with adjustable lamps. Emergency lighting automatically activates on power loss to light escape routes and critical areas. ## Answer #### Types of lighting schemes By light distribution: **direct, semi-direct, general diffusing, semi-indirect and indirect** lighting (decided by the fraction of light thrown downward, from 90–100 % for direct to 0–10 % for indirect). By coverage of the area: **general lighting, local (localised) lighting, general plus local lighting, localised general lighting and emergency lighting**. #### General lighting General lighting provides a **uniform level of illumination over the whole floor area**, irrespective of the position of work. Luminaires of the same type are installed in a regular grid at a spacing within the allowed spacing-to-height ratio, usually with direct or semi-direct distribution. - Gives good uniformity (minimum/average ≥ 0.7) and allows machines to be moved freely. - Typical levels: 150–300 lux in workshops, stores and assembly areas. - Disadvantage: lighting the whole area to the level needed for fine work wastes energy. #### Local lighting Local lighting gives **high illumination on a small working area**, using lamps fixed on or near the machine (adjustable arm lamps, bench lights, machine lamps). - Gives 500–2000 lux where fine work, inspection or measurement is done. - Can be aimed to show surface texture and reduce shadows from the worker's body. - Must be used with some general lighting to avoid sharp contrast and eye fatigue; local lamps should be shielded to prevent glare and be low-voltage (24/48 V) in hazardous places. #### Emergency lighting Emergency lighting **operates automatically when the normal supply fails**, so that people can leave safely and dangerous processes can be shut down. - **Escape lighting:** lights exits, corridors, stairs and exit signs (about 1 lux minimum on escape routes). - **Standby lighting:** keeps essential work going (control rooms, hospitals, critical processes). - **Sources:** self-contained battery luminaires, central battery systems, UPS or DG sets with automatic changeover; batteries are usually rated for 1–3 hours. - Must be tested regularly. ```text Normal supply ──┬── General & local lights │ [Charger]──[Battery]──┐ │ │ (supply fails) → [Changeover] → Emergency lights ``` ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. Which list classifies lighting schemes by coverage of the area? A. Direct, semi-direct, general diffusing, semi-indirect, indirect B. General, local, general plus local, localised general, emergency C. Escape, standby, central battery D. Incandescent, LED, HID Answer: B. By coverage the schemes are general, local, general plus local, localised general and emergency. The other list is by light distribution. (Key point: Two ways of classifying schemes) 2. What is the main disadvantage of general lighting? A. Poor uniformity B. Machines cannot be moved C. Lighting the whole area to the level for fine work wastes energy D. It cannot use direct luminaires Answer: C. General lighting gives good uniformity and freedom to move machines, but meeting fine-work levels everywhere wastes energy. (Key point: General lighting disadvantage) 3. In a hazardous place, how should local lamps be supplied and fitted? A. Low voltage (24/48 V) and shielded to prevent glare B. At 400 V without shielding C. Only with no general lighting D. Only as emergency lamps Answer: A. Local lamps should be shielded against glare and be low-voltage (24/48 V) in hazardous places, and used with some general lighting. (Key point: Local lighting use) 4. Why must local lighting be used with some general lighting? A. To avoid sharp contrast and eye fatigue B. To reduce the supply voltage C. To increase lamp life D. To make it work as emergency lighting Answer: A. Sharp contrast between a bright work spot and dark surroundings causes eye fatigue. 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