Type : 7SJ50
Features and technical specifications:
- Phase–failure protection
- Earth–fault protection
- Over current time protection with selectable characteristics (inverse or definite–time)
- Directional over current–time protection with directional relay 7SP20
- Overload protection selectable without or with memory (thermal replica)
- Overload protection with start–up time monitoring (locked rotor)
- Additional high set (instantaneous) o/c elements available with all characteristics This numerical over current–time/overload protection relay block is easily insert in your schematic diagram and connect as you like way.
Application :
- over current–time and earth–fault protection relay, the 7SJ50 can protect radial feeders as well as small or medium sized machines and transformers.
- It can be used as back–up protection for differential and distance relays in HV and EHV feeder protection schemes.
- It can also be used as overload protection for motors, transformers and cables.
- By use of the directional relay 7SP20, the 7SJ50 can also be applied to ring feeders or to parallel lines with a single in feed. All components , including the DC/DC converter are located on a single PCB. The device can be supplied in three case variations. The model for panel surface mounting is supplied with two–tier terminals accessible from the front. The variants for panel flush mounting or cubicle mounting have rear connection terminals and are available with or without glass cover. Mode of operation :- The measuring quantities from the C.T.s are galvanically isolated, transformed and
shunted by input transducers and resistor circuits. The current proportional analog measuring voltages are then converted into digital values and further processed by a microcomputer. Based on the measured values and the selected characteristic and settings, it computes the tripping time. Measurement is performed on all
phases.
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