Real Time Clock; Time Synchronisation - Data Communication Interface; Time Synchronisation - Binary Input; Time Synchronisation - Irig-B (Optional) - Siemens 7SR21 Manual

6.7

Real Time Clock

Time and date can be set either via the relay fascia using appropriate commands in the System Config menu, via
the data comms channel(s) or via the optional IRIG-B input. Time and date are maintained while the relay is de-
energised by a back up storage capacitor.
In order to maintain synchronism within a substation, the relay can be synchronised to the nearest second or
minute using the IEC 60870-5-103 protocol, optional IRIG-B input or binary input.
The default date is set at 01/01/2000 deliberately to indicate the date has not yet been set. When editing the
Time, only the hours and minutes can be edited. When the user presses ENTER after editing the seconds are
zeroed and the clock begins running.
6.7.1

Time Synchronisation - Data Communication Interface

Where the data comms channel(s) is connected the relay can be directly time synchronised using the global time
synchronisation. This can be from a dedicated substation automation system or from 'Reydisp Evolution'
communications support software.
6.7.2 Time Synchronisation – Binary Input
A binary input can be mapped Clock Sync from BI. The seconds or minutes will be rounded up or down to the
nearest value when the BI is energised. This input is leading edge triggered.
6.7.3 Time Synchronisation – IRIG-B (Optional)
A BNC connector on the relay rear provides an isolated IRIG-B time synchronisation port. The IRIG-B input
expects a modulated 3-6 Volt signal and provides time synchronisation to the nearest millisecond.
6.8

Settings Groups

The relay provides eight groups of settings – Group number (Gn) 1 to 8. At any one time only one group of
settings can be 'active' – SYSTEM CONFIG>Active Group setting.
It is possible to edit one group while the relay operates in accordance with settings from another 'active' group
using the View/Edit Group setting.
Some settings are independent of the active group setting i.e. they apply to all settings groups. This is indicated
on the top line of the relay LCD – where only the Active Group No. is identified. Where settings are group
dependent this is indicated on the top line of the LCD by both the Active Group No. and the View Group No. being
displayed.
A change of settings group can be achieved either locally at the relay fascia, remotely over the data comms
channel(s) or via a binary input. When using a binary input an alternative settings group is selected only whilst the
input is energised (Select Grp Mode: Level triggered) or latches into the selected group after energisation of the
input (Select Grp Mode: Edge triggered).
©2010 Siemens Protection Devices Limited
7SR21 & 7SR22 Argus Description of Operation
Chapter 1 Page 70 of 71