Siemens 7SR157 Argus, Manual

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7SR157 Technical Manual
Chapter 7 - Page 10 of 14 © 2016 Siemens Protection Devices Limited
Section 4: Common Functions
4.1 Binary Inputs
Each Binary Input (BI) can be programmed to operate one or more of the relay functions e.g. inhibits for elements,
close-circuit supervision status and plant status signals etc. A common use of BI is to provide indication of alarm
or fault conditions. They can also be mapped directly to LEDs and for triggering waveform storage and operate
Binary Outputs directly.
4.1.1 The Effects of Capacitance Current
The BI have a low minimum operate current and may be set for instantaneous operation. Consideration should be
given to the likelihood of mal-operation due to capacitance current. Capacitance current can flow through the BI
for example if an earth fault occurs on the dc circuits associated with the relay. The BI will be less likely to mal-
operate if they:
1 Have both the positive and negative auxiliary supplies switched (double-pole switched).
2 Do not have extensive external wiring associated with them e.g. if the wiring is confined to the
relay room.
4.1.2 AC Rejection
The default pick-up time delay of 20ms provides immunity to ac current for dc applications e.g. induced from cross
site wiring.
BI can be configured for intentional operation from an ac supply by setting pickup and drop-off timers for each
individual BI: set pick-up to 0ms and drop-off to 25ms. If the wiring for ac operation of BI is more than 10 metres
in length, then screened twisted pair cable should be used.
If additional pick-up or drop-off time delays are required by the scheme logic, then this functionality can be
achieved by programmable logic within the device. An example:
An ac supply operated BI is required to operate the System Sync inhibit function, but also include a 100ms
minimum pick-up delay and 200ms minimum drop-off delay.
1) Set BI 1 for ac operation: