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1MRK 505 372-UEN Rev. K
Section 11
A test with primary current through the protected zone is usually a final check that the current circuits
are correctly connected to the IED protection scheme. It is important to have an appropriate source,
which is able to inject sufficient current in the primary circuit in order to distinguish between noise and
real injected current. Therefore it is recommended that the injection current should be at least 10% of
rated CT primary current.
11.1
Operation of the busbar differential protection
The primary injection tests of a differential IED consist of applying a suitable current source across
the primary winding of the CT connected to the current input of the IED. The testing is normally
carried out on one phase at a time. If the primary current is bigger than the set value of the
DiffOperLevel parameter, the IED shall issue the trip command as well. The primary current injection
test should be repeated for every CT until all current circuits in all phases are checked. The typical
connection for the primary injection test is shown in figure 23.
Primary Injection
Test Set
IEC05000470 V2 EN-US
Figure 23:
Testing will be explained from one general current input CTx (that is, x = 1, 2,..., Nmax; where Nmax
is equal to the maximum number of used CT inputs).
Follow the following test instructions for all used current inputs in an IED.
Procedure
1.
Connect the test set for injection primary current to the main CT connected to the current
terminals of CTx input of the IED as shown in figure 23.
2.
Make sure that current measurement from the CTx input are included in one of the differential
zones.
3.
Inject the primary current in phase L1 and note the incoming and differential currents on the
local HMI of the IED. The values of the incoming and the differential currents shall correspond
to the injected primary current.
4.
Check that the current is present only in the phase being tested.
5.
If the injected current is high enough, check that trip contacts operate accordingly to the
scheme wiring.
Busbar protection REB670
Commissioning manual
Primary injection testing
Whenever it becomes necessary to work on primary equipment, it is essential that all
the necessary switching, locking, earthing and safety procedures are observed and
obeyed in a rigid and formalized manner. Operating and testing procedures should
be strictly followed in order to avoid exposure to live equipment.
1200/1
Optional equipment
(i.e,Test Switch,CB
Fail relay,other relays)
Typical test connection for primary injection testing
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Primary injection testing
IED
CT Input
IEC05000470-2-en.vsd
Section 11
IP10812-1 v1
SEMOD65857-3 v3
SEMOD65857-8 v2
M12203-3 v5
143
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