The TD-4 relay may be used for any timing application requiring a two-stage timing interval. The first stage being adjustable from 0.1 to 1.0 seconds, and the second stage for 0.5 to 3.0 seconds. The relay operates from a DC source of 48, 125, or 250 volts DC.
This relay is particularly suitable for use as a timing unit for the second and thirdzone KD-4 and KD-41 relays in a compensator distance relaying scheme. By proper connections in the relaying scheme, the TD-4 will provide a single time delay for zone 2 faults, or a longer time delay for zone 3 faults.