1-phase bus differential relay using auxiliary summation CT's
REB 101 is a high-speed differential relay of the percentage stabilised type for phase and earth-fault detection and can be used for busbars at all voltage levels. Internal faults are measured before saturation of the current transformer. Stability for external faults is guaranteed also at instantaneous saturation of the current transformer.
In gas insulated switchgears the current transformer cores in the bushings can preferably be used. The total gas insulated switchgear will then be included in the measuring zone of the bus protection.
Intermediate summation current transformers are used for adjustment of the CT-ratios and to reduce the secondary current. They are also used to galvanically separate the primary from the measuring circuit of the relay.
Main Features:
- Percentage restrained differential relay for phase-to-phase and phase-earth faults
- Microprocessors in logic- and time-circuits with self supervision
- Measuring time 1-3 ms and trip impulse from REB 101 within 6-9 ms
- Full stability for through-going fault currents even when current transformers are totally saturated