End To End Signalling; On-Load Tests - Siemens 7SR18 Solkor Manual

7SR18 Commissioning & Maintenance Guide
2.7
E
ND TO END
Healthy Protection Signalling Communication is required end-to-end for the differential feature to operate
correctly. Protection Signalling Communication failure between relays can be programmed to provide indication
via binary output contact or illuminate an LED on the fascia utilising 'Prot'n Comms Alarm' in the output matrix.
The SIGNAL HEALTHY LED of both relays should be checked, as they are independent of each other.
2.8
O -L
N OAD
The directional feature can be tested using load current. The test undertaken (Test 1 or Test 2) is depending upon
the level of load current flowing in the feeder at the time of the test. The level of load current can be checked via
the restraint current measurement in the Instruments mode. The levels of load, restraint and differential currents
should be recorded. One of the following tests should be performed to test the directional capability. Which of
these two tests to do, will depend upon the restraint (feeder load) current flowing at the time of the test: -
(i) Test 1 - If restraint current is greater than the P/F Differential Setting /2
(ii) Test 2 - If the load current is less than P/F Differential Setting /2
The test procedure is as follows: -
Close both circuit breakers at either end of the feeder to permit load current to flow. Both relays should be stable
and the "Signal Healthy" LED on both relays should be permanently illuminated, i.e. not flashing.
Test 1 – Where Load Current is High
This test applies when the load current is high enough to ensure that the restraint current is higher than half of
"P/F Differential" setting. The restraint current is the average of the load current measured at each end. Since
these two values are normally the same (e.g. unless there are significant values of in-zone capacitance current or
load current of a small auxiliary power transformer in the protected zone), then the restraint current will equal the
load current.
The load current at the local end and the remote end can both be read from either relay using the Instrument
display. This allows the restraint current to be established.
With the relays connected normally and load current flowing the relay should be stable and minimum differential
current displayed on the instruments.
Reversing the CT connections will cause the relays to become unstable and they will issue a trip signal. High
levels of differential current can be observed on the instruments.
Ø
The "Phase Reversal" setting in the relay's "CT/VT Config" setting menu is employed to swing the current
vector on one relay by 180°.
Ø
Use the [ENTER], [ò] and [ñ] pushbuttons or Reydisp Evolution to change the "Phase Reversal" setting from
"Disabled" to "Enabled".
Note: When the [ENTER] pushbutton is pressed to initiate the Phase reversal of 180°, the trip output will be
initiated immediately! Phase reversal can then be turned back to the Disabled setting.
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