--- title: "Define coincidence factor" subject: "Transmission and Distribution System Design" chapter: 6 key: "semester_8/transmission_and_distribution_system_design:define-coincidence-factor" source: https://www.bctengineer.com/q/semester_8/transmission_and_distribution_system_design/define-coincidence-factor site: BCT Engineering --- # Define coincidence factor Transmission and Distribution System Design · Chapter 6: Electrical Load Characteristics and Load Forecast - Asked in: 2069 Bhadra (old course), 3 marks; 2067 Chaitra (old course), 2 marks (asked 2 times) - Video: [Importance of high Load factor & Diversity Factor](https://www.youtube.com/watch?v=do7hSqvUFPI) — Neso Academy - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_8/transmission_and_distribution_system_design/define-coincidence-factor - Whole chapter: https://www.bctengineer.com/md/semester_8/transmission_and_distribution_system_design/chapter-6 ## Question Define coincidence factor with respect to distribution consumer characteristics and discuss its significance on the design of distribution system. ## Short answer Coincidence factor is group maximum demand divided by sum of individual maximum demands (≤1). It prevents oversizing of distribution transformers and feeders by recognizing that individual peaks do not occur simultaneously, allowing accurate equipment rating. ## Answer **Coincidence factor** is the ratio of the maximum demand of a group of consumers taken together to the sum of the individual maximum demands of those consumers: $$ \text{Coincidence factor} = \frac{\text{Maximum demand of the group}}{\sum \text{Individual maximum demands}} = \frac{1}{\text{Diversity factor}} \le 1 $$ It is less than 1 because consumers do not all reach their own peaks at the same time. For example, if 50 houses each have a peak of 2 kW but the group peak is 60 kW, the coincidence factor is $60/100 = 0.6$. **Significance in distribution design:** - The peak load on a distribution transformer, LT feeder or service main is found as (number of consumers) × (individual peak) × (coincidence factor). Without it, equipment would be badly oversized. - It decreases as the number of consumers increases, so a transformer serving many consumers needs less capacity per consumer than a service drop serving one. - It lets the designer choose smaller, cheaper transformers and conductors while still meeting the actual peak, and gives realistic voltage drop and loss calculations. - Wrong (too high) values give idle capacity and high no-load losses; too low values cause overloading. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. Coincidence factor is: A. Sum of individual maxima divided by group maximum B. Maximum demand of the group divided by the sum of individual maximum demands C. Average load divided by peak load D. Connected load divided by demand Answer: B. It is group maximum demand over the sum of individual maxima, the reciprocal of diversity factor, and is at most 1. (Key point: Definition) 2. Why is the coincidence factor less than 1? A. Voltage drops reduce the load B. Consumers do not reach their individual peaks at the same time C. Power factor is below 1 D. Losses are neglected Answer: B. Individual peaks occur at different times, so the group peak is below the sum of peaks. (Key point: Why less than 1) 3. 50 houses of 2 kW peak each have a group peak of 60 kW. What is the coincidence factor and how is it used? A. 1.67; to enlarge transformers B. 0.6; transformer peak = number x individual peak x coincidence factor, avoiding oversizing C. 0.6; it is added to the diversity factor D. 0.3; it replaces load factor Answer: B. 60/100 = 0.6. Using it sizes transformers and feeders for the actual peak. 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