This relay can be used for definite time over current protection against phase and Earth faults on medium and low voltage distribution systems. The definite time relay offers a considerable advantage over inverse time relays in instances where there ia a wide variation in line impedance. Another application is in the field of stalling protection of motors. When the thermal overload relay does not provide protection against stalling, separate definite time O/C relay type CTU can be used to provide the same. This relay comes in following nomenclature: CTU-12/22/32/52/62/15. CTU relay combines the advantage of complete static measurements with characteristic of the robust, well proved attracted armature unit. These relays measure current and time accurately, imposes low burden on CT's. Each phase comprises a static overload detector and timer, which is accurate over a 10: 1-time setting range. When the positive peak of the input signal exceeds the reference level, the time delay circuit starts and after a preset time, drives the output relay. Instantaneous high set unit when fitted uses alternate half cycle for measurement and through a separate level detector drives a separate output relay.
