2.10 Virtual Input/Outputs; 2.11 Self Monitoring; 2.11.1 Protection Healthy/Defective - Siemens 7SR21 Manual

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7SR21 & 7SR22 Argus Description of Operation

2.10 Virtual Input/Outputs

The relays have 16 virtual input/outputs, these are internal logic states. Virtual I/O is assigned in the same way as

physical Binary Inputs and Binary Outputs. Virtual I/O is mapped from within the INPUT CONFIG > INPUT

MATRIX and OUTPUT CONFIG > OUTPUT MATRIX menus.

The relay incorporates a number of self-monitoring features. Each of these features can initiate a controlled reset

recovery sequence.

Supervision includes a power supply watchdog, code execution watchdog, memory checks by checksum and

processor/ADC health checks. When all checks indicate the relay is operating correctly the 'Protection Healthy'

LED is illuminated.

If an internal failure is detected, a message will be displayed, also an event will be generated and stored. The

relay will reset in an attempt to rectify the failure. This will result in de-energisation of any binary output mapped to

'protection healthy' and flashing of the protection healthy LED. If a successful reset is achieved by the relay the

LED and output contact will revert back to normal operational mode, and the relay will restart.

When the relay has an auxiliary DC supply and it has successfully passed its self-checking procedure then the

front facia Protection Healthy LED is turned on.

A normally open contact can be used to signal protection healthy. When the relay has DC supply and it has

successfully passed its self-checking procedure then the Protection Healthy contacts are made.

A normally closed contact is used to signal protection defective. When the DC supply is not applied to the relay or

a problem is detected within the relay then this output is de-energised and the normally closed contacts make to

provide an external alarm.

An alarm can be provided if the relay is withdrawn from the case. A contact is provided in the case at positions

25-26 of the PSU module, this contact closes when the relay is withdrawn.

Chapter 1 Page 21 of 71

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