GUID-F1F4E199-8B6A-4066-ACCB-07FE4F887417 V3 EN
Figure 194: Example of connections to test the line differential IED
Secondary current injection
There are two alternative modes to check the operation of a line differential IED.
These are not exclusive methods for each other and can be used for various test on
the IED.
Normal mode
In normal mode, that is, the mode when the function is on normal operation, the
local end IED sends phasors to the remote end IED and receives phasors measured
by the remote end IED. This mode can be used in testing the operating level and
time of the low and high stages of the local end IED. This is due to a test situation
when the remote end does not measure any current and therefore, all the current fed
to the local end current circuit is seen as differential current at both ends.
Testing of the line differential protection is done with both IEDs separated
geographically from each other. It is important to note that local actions in one IED
cause operation also in the remotely located IED. When testing the line differential
function, actions have to be done in both IEDs.
1YHT530004D05 D Section 4
Protection functions
615 series 371
Technical Manual
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