Trip Circuit Supervision (74Tcs); Trip Circuit Supervision Connections - Siemens 7SR23 DAD Manual

High impedance protection relay

5.2

Trip Circuit Supervision (74TCS)

Binary Inputs may be used to monitor the integrity of the CB trip circuit wiring. Current flows through the B.I.

confirming the integrity of the auxiliary supply, CB trip coil, auxiliary switch, C.B. secondary isolating contacts and

associated wiring connected to that BI. If the current flow ceases, the B.I. drops off and if it is user programmed to

operate one of the output relays, this can be used to provide an alarm. In addition, an LED on the relay fascia can

be programmed to operate. A user text label can be used to define the operated LED e.g. "Trip CCT Fail".

The relevant Binary Input is mapped to 74TCS-n in the INPUT CONFIG>INPUT MATRIX menu. To avoid giving

spurious alarm messages while the circuit breaker is operating the input is given a 0.4s Drop-off Delay in the

INPUT CONFIG>BINARY INPUT CONFIG menu.

To provide an alarm output a normally open binary output is mapped to 74TCS-n.

The following circuits are derived from UK ENA S15 standard schemes H5, H6 and H7.

For compliance with this standard:

Where more than one device is used to trip the CB then connections should be looped between the

tripping contacts. To ensure that all wiring is monitored the binary input must be at the end of the looped

wiring.

Resistors must be continuously rated and where possible should be of wire-wound construction.

Scheme 1 (Basic)

Scheme 1 provides full Trip and Close supervision with the circuit breaker Open or Closed.

Where a 'Hand Reset' Trip contact is used measures must be taken to inhibit alarm indications after a CB trip.

Figure 5-1

Trip Circuit Supervision Scheme 1 (H5)

Chapter 7) 7SR23 DAD Applications Guide

Chapter 7 Page 26 of 42

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