--- title: "T/F: radial operation of distribution in Nepal" subject: "Transmission and Distribution System Design" chapter: 5 key: "semester_8/transmission_and_distribution_system_design:tf-nepal-radial-distribution" source: https://www.bctengineer.com/q/semester_8/transmission_and_distribution_system_design/tf-nepal-radial-distribution site: BCT Engineering --- # T/F: radial operation of distribution in Nepal Transmission and Distribution System Design · Chapter 5: Electric Power Distribution - Asked in: 2070 Bhadra, 1+3 marks - 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/tf-nepal-radial-distribution - Whole chapter: https://www.bctengineer.com/md/semester_8/transmission_and_distribution_system_design/chapter-5 ## Question With reference to a distribution system design, state whether the following statement is True or False with justification: In Nepal, the primary and secondary distribution systems operate in radial. ## Short answer TRUE. NEA operates both primary (33/11 kV) and secondary (400/230 V) distribution radially, even though some urban 11 kV feeders have open-loop ties that are normally open. This radial operation minimizes cost, simplifies protection, and supports rural electrification, though at the expense of reliability and tail-end voltage. ## Answer **TRUE.** In Nepal (NEA's distribution under the INPS), both levels are operated radially: - **Primary distribution** (33 kV and 11 kV): feeders leave the grid or distribution substation and branch out to the 11/0.4 kV transformers along one path. Some urban 11 kV feeders in Kathmandu Valley and other cities have tie switches or ring main units forming loops. These are kept **normally open** (open loop) and the feeders are still **operated radially**. The tie is closed only to transfer load during faults or maintenance. - **Secondary distribution** (400/230 V): each distribution transformer feeds its own LT lines radially to the consumers. There is no interconnection between transformers. Reasons for radial operation: 1. It has the lowest cost for Nepal's low and scattered load density and long hilly feeders. 2. Protection is simple (drop-out fuses, OC/EF relays, reclosers) and operation is easy. 3. It is easy to extend for rural electrification. Its main drawbacks are lower reliability, poor tail-end voltage and higher losses. NEA reduces these through sectionalizing, open-loop ties in cities and more substations. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. The statement 'In Nepal, primary and secondary distribution operate radially' is: A. False, because primary is operated as a closed mesh B. False, because secondary transformers are interconnected C. True, because both levels are operated radially D. True only for secondary distribution Answer: C. Both primary (33 and 11 kV) and secondary (400/230 V) systems are operated radially in NEA's distribution. (Key point: Verdict) 2. How do urban 11 kV feeders with tie switches or RMUs still count as radial? A. The ties are kept normally open and closed only to transfer load in faults or maintenance B. The ties are always closed C. The ties connect LT lines of different transformers D. The ties are used only at 33 kV Answer: A. Open-loop ties leave the feeders operated radially in normal service. (Key point: Urban tie switches) 3. How is the 400/230 V secondary system arranged? A. All transformers are interconnected in a mesh B. Each distribution transformer feeds its own LT lines radially, with no interconnection between transformers C. Transformers are connected in a ring at 400 V D. It uses single-phase 33 kV lines Answer: B. Each transformer supplies its own radial LT network. 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