--- title: "Types of lighting scheme in industry" subject: "Industrial Power Distribution and Illumination" chapter: 7 key: "semester_6/industrial_power_distribution_and_illumination:industrial-lighting-schemes" source: https://www.bctengineer.com/q/semester_6/industrial_power_distribution_and_illumination/industrial-lighting-schemes site: BCT Engineering --- # Types of lighting scheme in industry Industrial Power Distribution and Illumination · Chapter 7: Illumination Design Principles - Asked in: 2080 Chaitra, 4 marks; 2077 Chaitra, 4 marks; 2070 Bhadra, 8 marks; 2068 Magh (old course), 4 marks (asked 4 times) - Video: [Illumination Engineering Part - 10 - Basic Principle of Light Control & Types of lighting Schemes](https://www.youtube.com/watch?v=sIC7YypnDGg) — zenmurali Sachithanandam - 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/industrial-lighting-schemes - Whole chapter: https://www.bctengineer.com/md/semester_6/industrial_power_distribution_and_illumination/chapter-7 ## Question Explain different types of lighting scheme used in an industry. ## Short answer Industrial schemes include general lighting for uniform area illumination, local lighting for high illuminance at specific tasks, and general plus local lighting. By distribution: direct (90-100% downward) is common in workshops, semi-direct in offices, and indirect in areas where glare must be avoided. Emergency lighting ensures safety during supply failure. ## Answer A **lighting scheme** is the way luminaires are arranged to provide light for the work in an area. Industries use the following schemes: #### 1. General lighting Luminaires are spread in a regular pattern over the whole area to give **uniform illumination** (e.g. 200–300 lux) on the working plane, independent of where machines are placed. Spacing–height ratio is kept within limits for uniformity. Used in assembly halls, warehouses and general workshops. #### 2. Localised (local) lighting Extra lamps are fixed **close to particular work points** (on a lathe, inspection bench, drawing board) to give high illumination (500–1000+ lux) only where fine work is done. Saves energy but gives strong contrast if used alone. #### 3. General plus local (supplementary) lighting Moderate general lighting for movement and safety, plus local lamps at critical tasks. This is the usual scheme in machine shops: it is economical and avoids dark surroundings and eye strain. #### 4. Localised general lighting General-type luminaires are concentrated in the zones where work is done (above machine rows), with lower lighting over gangways. #### 5. Emergency lighting Battery-backed or generator-fed lights that come on when the normal supply fails, lighting escape routes, exits, stairs and critical machines (minimum about 1 lux on escape routes). #### Classification by light distribution | Scheme | Downward light | Use in industry | |---|---|---| | Direct | 90–100 % | High-bay halls, workshops (most common) | | Semi-direct | 60–90 % | Offices, control rooms | | General diffusing | 40–60 % | Canteens | | Semi-indirect / indirect | 0–40 % | Drawing offices, VDU rooms (no glare) | In factories, **direct general lighting with high-bay LED or metal-halide luminaires plus local lighting at machines** is the normal choice, with phases distributed to avoid stroboscopic effect. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. What does general lighting aim to provide in an industrial area? A. High lux only at the work points B. Uniform illumination over the whole area regardless of machine position C. Light only during supply failure D. Indirect light only Answer: B. General lighting uses luminaires in a regular pattern to give uniform illumination on the working plane. (Key point: General lighting) 2. Why is localised (local) lighting used alone not good practice? A. It gives too little light at the work point B. It gives strong contrast with dark surroundings C. It cannot be fixed near machines D. It uses more energy than general lighting Answer: B. Local lamps give high lux only at the work point, so used alone they create strong contrast, which is why general lighting is added. (Key point: Localised lighting) 3. Why is general plus local lighting the usual scheme in machine shops? A. It is the most costly and gives the best colour B. It is economical and avoids dark surroundings and eye strain C. It removes the need for any switch D. It only works with emergency lights Answer: B. Moderate general lighting gives safe movement while local lamps serve critical tasks, which is economical and reduces eye strain. (Key point: General plus local scheme) 4. What is the function of emergency lighting? A. To give 500 lux on machines B. To come on when the normal supply fails and light escape routes and critical machines C. To replace general lighting permanently D. To avoid stroboscopic effect Answer: B. It is battery or generator fed and lights exits, stairs and critical machines when normal supply fails (about 1 lux on escape routes). 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