IS 3842 : Part 1 : 1967 Application guide for electrical relays for ac systems: Part 1 Overcurrent relays for feeders and transformers

1. Scope

1.1 This guide deals with the application of overcurrent rciays for ac S)'lIte.tnS, covered by IS: 3231-1965* for feedetl' and transfonners. It covers both directional and non-directional overcurrent Tciays and their application for phase faults, earth faults, restricted earth faults and corehalance earth-fault ·protection. It also covers time-current characteristics and considerations for the setting and co-ordination of ovcrcurrent (nondirectional) rciays.

l.2 This guide does not cover: va) the principles of system design and system protection,

b) direct acting overcurrent devices, and

c) static relays.