IEC08000278-1-en.vsdx
IED
LOCAL REMOTE
Trans.
21-216
PDH
MUX
SDH
MUX
SDH
MUX
PDH
MUX
Trans.
21-216
IED
Fibre-optic or galvanic loop-back
Test 1 Test 2 Test 3 Test 4 Test 5 Test 6 Test 7
IEC08000278 V1 EN-US
Figure 89: An example of loop-back testing set-up
Test 1: connect RX and TX directly to the actual LDCM with a fibre-optic loop. Check that the
communication status is OK on the local HMI.
If there is more than one LDCM in the local line differential protection IED, the test must
be repeated for each channel.
Test 2 to Test n: loop back RX+ to TX+ and RX- to TX-. Loop back, one-by-one, in respective
interface in the communication network. Check that the communication status is OK for each
interface point on the local HMI. If no fault is found, Test 1 and Test 2 should be repeated in reverse
order from the remote end.
When loop-back testing is finished, remember to restore the original terminal numbers.
Having the same terminal number at both ends can cause an unwanted trip. If the
terminal was set to Test mode, check that the local trip is reset before leaving the Test
mode
1MRK505382-UEN Rev. K Section 5
Communication set-up
Communication set-up, 670/650 series 91
Application Guide
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