Protection Signalling; Inter-Tripping; External Inter-Trip Example Using Separate Cb Fail Device - Siemens 7SR18 Solkor Manual

6.5

Protection Signalling

The relay provides several separate external signalling channels. These can be used for externally initiated inter-
tripping or for signalling from another protection, such as a permissive or blocking signal required by distance
protection schemes. The use of this differential protection with a distance relay is a cost-effective method of
protecting a circuit. It provides dual main protections (operating on different principles and hardware), inter-
tripping, signalling and backup over current protection.
The protection/inter-trip signal is initiated by a contact from an external device, wired to energise one or more of
the binary inputs. The operating time is approximately 20 ms from energising the local relay status input to closing
the output contact of the remote relay.
6.6

Inter-tripping

Provision for both internally and externally initiated inter-tripping is included in the relay. This feature can be
enabled or disabled in the PROT'N COMMS/INTERTRIP menu.
a) Externally Initiated Inter-tripping (85S-n, 85R-n)
External inter-tripping can be initiated by energising a relay Binary Input from an external device. The input(s)
used for this purpose, must be assigned to 85S-n in the INPUT CONFIG setting menu or the INPUT MATRIX of
the local relay. The output relay(s) assigned to trip the circuit breaker, of the remote end relay must be allocated
to the corresponding 85R-n in the OUTPUT CONFIG menu or the OUTPUT MATRIX.
b) Internally Initiated Inter-tripping (87R) (Incorporates 87L-n and 87HS-n signals)
Internal inter-tripping is a situation where one relay issues a command to the other relay to perform some action
e.g. to trip a circuit-breaker in the event of an internal zone fault.
In this example fault current measured by relay A is below setting and the Line Differential 87L-n is inhibited by
the Under Current 37 used as a Guard feature. The Line Differential 87L-n element of relay B, where the fault
current is above setting, will issue a trip to operate its own circuit-breaker. This relay B will also send a Differential
IT (87R) signal to relay A to perform a trip operation.
6.6.1

External Inter-trip example using separate CB Fail device.

The CBs of both Local and Remote Relays can be operated by a single external device e.g. CB Fail relay, via
suitable relay programming.
The following example assumes a CB Fail Relay connected to the Binary Input BI 1 of the Local Relay. Once this
BI 1 is energised, Binary Output contact BO 2 is operated which in turn opens the Local CB, see Figure 6.6.1-1.
At the same time a signal is sent to the Remote Relay via inter-trip channel 85S-4, see Figure 6.6.1-2. This is
received in the Remote Relay and is mapped in the Output Matrix to Binary Output BO 2 which in turn opens the
Remote CB, see Figure 6.6.1-3.
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Figure 6.6-1 Inter-trip via Differential IT (87R)
7SR18 Applications Guide
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