SD-BD-04-02/Rev.09/30-05-68
TRIP CIRCUIT SUPERVISION RELAY
Description
Trip circuit supervision relay (E95) is a device commonly used in power systems to monitor and ensure the reliability of the trip circuit in switchgear or power circuit breaker. It plays a critical role in power stations and substations.
Features
Monitoring the trip circuit status
- Ensures the continuity of the trip circuit, which is responsible for tripping the breaker.
- Detects any disconnections or abnormalities in the circuit, such as broken wires or blown fuses of DC circuit.
Enhancing the reliability of protection systems
- Alerts operators to issues in the trip circuit so they can be resolved before a fault occurs.
Supervising during normal operation and activation
- Operates continuously to monitor the circuit during both standby and active trip conditions.
Application
In a protection system, the trip circuit of the circuit breaker is very vital as it isolates the faulty section. A failed trip coil or its circuit, during an event of actual fault, where that CB is commanded to clear the fault, will unable to isolate the faulted equipment / Section, as results the fault remains in to the system. Hence, fault shall be isolated by the upstream protective relay.
The supervision function is particularly important, when there is only one tripping coil and CB tripping is vital such as Generator circuit breakers or any other important circuit breaker in distribution networks. The E95 is intended for a continuous supervision of circuit breaker trip circuit and to give an annunciation or alarm for he following conditions,
- Short circuit in control supply (DC)
- Open circuit in control supply (DC)
- Loss of control supply voltage
- Failure of mechanism
For any of the above condition, The circuit breaker could not trip and isolates the faulty part while system has actual fault. To overcome such situation, Trip circuit supervision relay (E95) becomes very necessary.
Technical Data
Operations
Figure : 1 Positive DC Trip bus operation (Typical diagram)
Figure : 2 The LED of the E95 lights up (CB open, TC OK) if the breaker is Open, the trip coil is healthy, and the 52b contact is functioning properly. The LED turns off when the breaker closed. The 52b contact helps keep the internal relay energized to prevent unnecessary alarms during breaker operation. During normal operation, there may be a short period when both the 52a and 52b contacts are open. The relay includes a capacitor that delays dropout for at least 200 milliseconds to reduce false alarms during this period.
Figure : 3 In case the breaker is closed, the LED of the E95 lights up (CB Close, TC OK), the trip coil is healthy, and the 52a contact is functioning properly.
Figure : 4 At normal condition, in the event of a trip contact is operated, the trip signal will direct to the trip coil of the breakerthrough the 52a contact.
Connection Diagrams
Dimension
Product Coding
