(1) Description of Operation 7SR224
Page 56 of 66 ©2009 Siemens Protection Devices Limited
5.4 BROKEN CONDUCTOR (46BC)
The element calculates the ratio of NPS to PPS currents. Where the NPS:PPS current ratio is above
46BC Setting an output is given after the 46BC Delay.
The Broken Conductor function can be inhibited from
Inhibit 46BC A binary or virtual input.
Figure 5.4-1 Logic Diagram: Broken Conductor Function (46BC)
5.5 TRIP CIRCUIT SUPERVISION (74TCS)
The relay provides three trip circuit supervision elements.
One or more binary inputs can be mapped to 74TCS-n. The inputs are connected into the trip circuit
such that at least one input is energised when the trip circuit wiring is intact. If all mapped inputs
become de-energised, due to a break in the trip circuit wiring or loss of supply an output is given.
The 74TCS-n Delay setting prevents failure being incorrectly indicated during circuit breaker
operation. This delay should be greater than the operating time of the circuit breaker.
The use of one or two binary inputs mapped to the same Trip Circuit Supervision element (e.g.
74TCS-n) allows the user to realise several alternative monitoring schemes – see ‘Applications Guide’.
TCS-n
Enabled
Disabled
&
74TCS-n
74TCS-n
74TCS-n Delay
≥1
74TCS-n
NOTE: Diagram shows two binary inputs mapped
to the same Trip Circuit Supervision element
Figure 5.5-1 Logic Diagram: Trip Circuit Supervision Feature (74TCS)
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