Siemens 7SR23 DAD, Manual

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Chapter 7) 7SR23 DAD Applications Guide
©2013 Siemens Protection Devices Limited Chapter 7 Page 41 of 42
7.2 Binary Outputs
Binary Outputs are mapped to output functions by means of settings. These could be used to bring out such
digital signals as trips, a general pick-up, plant control signals etc.
All Binary Outputs are trip rated
Each can be defined as Self or Hand Reset. Self-reset contacts are applicable to most protection applications.
Hand-reset contacts are used where the output must remain active until the user expressly clears it e.g. in a
control scheme where the output must remain active until some external feature has correctly processed it.
Case contacts 26 and 27 will automatically short-circuit when the relay is withdrawn from the case. This can be
used to provide an alarm that the Relay is out of service.
Notes on Self Reset Outputs
With a failed breaker condition the relay may remain operated until current flow in the primary system is
interrupted by an upstream device. The relay will then reset and attempt to interrupt trip coil current flowing
through an output contact. Where this level is above the break rating of the output contact an auxiliary relay with
heavy-duty contacts should be utilised.
7.3 LED
S
Output-function LEDs are mapped to output functions by means of settings. These could be used to display such
digital signals as trips, a general pick-up, plant control signals etc.
User Defined Function LEDs are used to indicate the status of Function Key operation. These do not relate
directly to the operation of the Function Key but rather to its consequences. So that if a Function Key is depressed
to close a Circuit-Breaker, the associated LED would show the status of the Circuit-Breaker closed Binary Input.
Each LED can be defined as Self or Hand Reset. Hand reset LEDs are used where the user is required to
expressly acknowledge the change in status e.g. critical operations such as trips or system failures. Self-reset
LEDs are used to display features which routinely change state, such as Circuit-Breaker open or close.
The status of hand reset LEDs is retained in capacitor-backed memory in the event of supply loss.