Broken Conductor (46Bc); Trip Circuit Supervision (74Tcs); Figure 5.6-1 Logic Diagram: Broken Conductor Function (46Bc); Figure 5.7-1 Logic Diagram: Trip Circuit Supervision Feature (74Tcs) - Siemens 7SR21 Manual

5.6

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
46BC Element
Enabled
Disabled
Inhibit 46BC
IL1
I2
NPS
IL2
Filter
IL3
IL1
I1
PPS
IL2
Filter
IL3

Figure 5.6-1 Logic Diagram: Broken Conductor Function (46BC)

5.7

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'.
74TCS-n
Enabled
Disabled
74TCS-n
74TCS-n

Figure 5.7-1 Logic Diagram: Trip Circuit Supervision Feature (74TCS)

©2010 Siemens Protection Devices Limited
A binary or virtual input or function key.
46BC Setting
&
c
&
≥1
NOTE: Diagram shows two binary inputs mapped
to the same Trip Circuit Supervision element
7SR21 & 7SR22 Argus Description of Operation
46BC Delay
74TCS-n Delay
Chapter 1 Page 64 of 71
46BC
TCS-n