Siemens 7SR105 Rho - CB Maintenance; Output Matrix Test; CB Counters; I 2 T CB Wear

7SR105 Rho Description of Operation
©2018 Siemens Protection Devices Chapter 1 Page 52 of 57
Setting name Range Default Setting Notes
Unsolicited Mode
DISABLED ENABLED DISABLED As Required
Setting is only visible
when COM1 Protocol is
set to DNP3
Destination
Address
0 … 65534 0 As Required
Setting is only visible
when COM1 Protocol is
set to DNP3
Ext Wire loop to
Include line
terminating Res
To Control
System
RS 485
Screened
twisted pair
Rear
terminals
RS 485
Screened
twisted pair
Rear
terminals
1
2
3
4
B/-
Term
A/+
GND
1
2
3
4
GND
Figure 6-6 Communication to Multiple Devices from Control System using RS485
6.2 CB Maintenance
6.2.1 Output Matrix Test
The feature is only visible from the Relay fascia and allows the user to operate the relays functions. The test of
the function will automatically operate any Binary Inputs or LED’s already assigned to that function.
Any protection function which is enabled in the setting menu will appear in the Output Matrix Test.
6.2.2 CB Counters
The following CB maintenance counters are provided:
CB Total Trip Count:
Increments on each trip command issued.
CB Delta Trip Count: Additional counter which can be reset independently of the
Total Trip Counter. This can be used, for example, for
recording trip operations between visits to a substation.
Binary outputs can be mapped to each of the above counters, these outputs are energised when the user
defined Count Target or Alarm Limit is reached.
6.2.3 I
2
t CB Wear
An I
2
t counter is also included and this can provide an estimation of contact wear and maintenance requirements.
The algorithm works on a per phase basis, measuring the arcing current during faults. The I
2
t value at the time of
trip is added to the previously stored value and an alarm is given when any one of the three phase running counts
exceeds the set Alarm limit. The t value is the time between CB contacts separation when an arc is formed,
Separation Time, and the CB Clearance time.
The I
2
t value can also triggered and reset from a binary input or command.