7SR157 Technical Manual
Chapter 7 - Page 4 of 14
© 2016 Siemens Protection Devices Limited
Section 2: Control Functions
2.1
Synchronising Enable Modes
The 7SR157 relay has been designed to conform to NGTS 3.7.7 and therefore must be able to be set up as a
check synchronising relay, for applications such as manually bringing a generator online and also as a check and
system synchronising relay for applications where two power systems are to be connected. The following
examples show various ways that the relay can be enabled for these different applications.
The
25 Check Sync
and
25 System Sync
functions each have independent enable modes. If the requirement is
for the relay to be used as a check for manually synchronising a generator for example, then
25 System Sync
is
not required.
1.
Set
25 Check Sync
Enable
to
MANUAL
(or
AUTO
)
Set
25 System Sync Enable
to
Disabled
Set
25 Close On Zero
to
Disabled
Setting the
25 System Sync Enable
to
Disabled
and the
25 Close On Zero
to
Disabled
will ensure that the
relay will only give a
25 Check Sync Close output
. The relay will continue to issue a
25 Check Sync Close
output
if the power system conditions fall within the relay setting parameters.
If the requirement is for a check and system synchronising scheme where a lockout of the relay is required if the
system splits, then:
2.
Set
25 Check Sync
Enable
to
MANUAL
(or
AUTO
)
Set
25 System Split Detector
to
Enabled
Set
25 System Split Mode
to
Phase
Set
25 Split Angle
to a suitable angle e.g.
170°
Set
System Sync
Enable
to
LOCKOUT
Set
25 Close On Zero
to
Disabled
This will ensure that if the power system splits the relay will not go into system synchronising mode but revert to
lockout mode. The relay will at this point issue a
System Split Lockout
output.
If the requirement is for a check and system synchronising scheme where system synchronising is required if the
system splits, then:
3.
Set
25 Check Sync
Enable
to
MANUAL
(or
AUTO
)
Set
25 System Split Detector
to
Enabled
Set
25 System Split Mode
to
Phase
Set
25 Split Angle
to a suitable angle e.g.
170°
Set
25 Split Mode
to
SS
Set
System Sync
Enable
to
MANUAL
(or
AUTO
)
Set
25 Close On Zero
to
Disabled
This will ensure that if the power system splits the relay will system synchronise.
It should be noted that at any time during a synchronising sequence, the relay can be inhibited from operation
using the
Check Sync Inhibit
or
System Sync Inhibit
command from the control system.
Note: the relay settings groups could be used to switch between the different modes of the relay. The relay could
be set up to be a check synchroniser in settings Group 1 and a check and system synchronising relay in settings
Group 2. The group selection and thus the actual relay mode of operation could then be changed remotely using
a status input signal or a communications command from a control system.
Summary of Contents for 7SR157 Argus
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