Protection Engineering Basics and Schemes Protection Engineering | Page 70

We will discussed three schemes of Trip circuit
Supervision here
 H4
 H5
 H7
2.4.1 H4 Trip Circuit Scheme:
Here we are only
monitoring the circuit healthiness, one lamp and small
value resistor is connected in parallel of protection relay
contacts.
H4 Operation: here very small amount of current is flow
across resistor and lamp, but this resistor-lamp circuit
carry small amount of current and unable to energize
make auxiliary contacts 52A of breaker.
That minimum current through resistor-lamp (Trip
supervision Relay) is interrupted when circuit not remains
healthy and lamp indication will be off. Indications means
either circuit not remain healthy or relay operated. You
can differentiate it by viewing status of relay.
pg. 70