Section 11 Primary Injection Testing; Operation Of The Busbar Differential Protection - ABB REB670 Commissioning Manual

1MRK 505 372-UEN A
Section 11
11.1
Busbar protection REB670 2.2 IEC
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.
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.

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
1200/1
IEC05000470 V2 EN-US
Figure 23: Typical test connection for primary injection testing
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).
Optional equipment
(i.e,Test Switch,CB
Fail relay,other relays)
Section 11
Primary injection testing
IED
CT Input
IEC05000470-2-en.vsd
IP10812-1 v1
SEMOD65857-3 v3
SEMOD65857-8 v2
M12203-3 v5
161