Binary Outputs (Output Relays); Figure 2.9-1 Binary Output Logic - Siemens 7SR21 Manual

7SR21 & 7SR22 Argus Description of Operation
2.9

Binary Outputs (Output Relays)

Relays are fitted with 6, 8, 14 or 16 binary outputs. All outputs are fully user configurable and can be programmed
to operate from any or all of the available functions.
The Power Supply module includes the relay basic I/O. The module includes six binary outputs each fitted with 1
contact – providing in total 1 x normally closed (NC), 2 x change-over (CO) and 3 x normally open (NO) contacts.
Non-directional (7SR21) relays have two additional binary outputs providing 2 x NO contacts on the analogue
module. Additional I/O modules may be fitted; these provide 8 x NO contacts.
In the default mode of operation binary outputs are self reset and remain energised for a user configurable
minimum time of up to 60 seconds. If required, outputs can be programmed to operate as 'hand reset' relays.
The binary outputs can be used to operate the trip coils of the circuit breaker directly where the trip coil current
does not exceed the 'make and carry' contact rating. The circuit breaker auxiliary contacts or other in-series
auxiliary device must be used to break the trip coil current.
When the relay is withdrawn from the case all normally closed contacts will be open circuited. This should be
considered in the design of the control and protection circuitry.
Notes on Hand Reset Outputs
Hand reset outputs can be reset by either pressing the TEST/RESET► button, by energising a suitably
programmed binary input, or, by sending an appropriate command over the data communications channel(s).
On loss of the auxiliary supply hand-reset outputs will reset. When the auxiliary supply is re-established the binary
output will remain in the reset state unless the initiating condition is still present.
Notes on Self Reset Outputs
Self reset operation has a minimum reset time of 100ms
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.

Figure 2.9-1 Binary Output Logic

©2010 Siemens Protection Devices Limited Chapter 1 Page 20 of 71