Differential Protection
Warm Wishes. I need some clarification regarding the differential trip protection in Line Differential Protection Siemens Siprotec Relay 7SD522. I am using Digsi Seiments software. The relay manual also available in the help menu. If you just click the help menu and select help on device, you can get the manual and search diff protection.
Now I am doing Differential protection test.
1) For diffenential protection, in the I/O masking, I enabled Diff General Trip (3141) and inject the fault current by Omicron. I got the output.
but, If i am enabled Diff Trip 1p L1, I couldn't get the output. I followed the same procedure which i followed in the Diff General Trip.
As per the "Tripping Logic of the Differential Protection - Fig 2-32 in the 7SD5 manual, page 102), If diff high set or I>Release diff is high, then any one of the 7 output contact should enable (3141, 3142 ....3147). But for me 3141 is only tripped. Other contacts not tripping.
Also, Sometimes when the injected current is increasing above the set point, for example if I diff>> = 1.2A, my injected current is going above 1.3A, that time I
manually stop the injected current, that time in relay display, "Diff Flt L1E, PU time 1231ms, Trip time 0ms" such that display appears. This happened only after i
manually stop the injecting current, not by automatic tripping. I can understand that the relay senses, but it didn't give any trip command to the output contact.
Kindly clarify the above.
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Intertrip Function
2) As per the "Logic Diagram of the Intertrip Transmission Circuit - Fig 2-33, in the 7SD5 manual, page 110",
the IT.Send.PI1L1 (3511, 3512,.....3516) can be enabled by two ways. By getting,
1) Diff Trip 1pL1 (3142 to 3145)
2) >Intertrip L1 (3501 to 3504). (Binary input)
For the first one, I couldn't get the Diff Trip from differential protection. I am thinking that Intertrip shouldn't work except these four Diff Trips (3142, 3143, 3144, 3145).
And for the second one, i injected a 110V DC input to the input terminal of the relay (I selected BI 1) and assigned the LED 1 for the assigned input. Than i set (unlatched) IT.Send.PI1.L1 binary output 4 and assigned a LED 2 for this.
When I injected the 110V input to the input terminal, LED 1 Glows. and other than there is no output. I couldn't understand that how to get the Inter Trip Send Signal Output by enabling the binary input.
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Anybody, if you know about the line diffenential siemens relay testing, kindly clarify my doubts.
If you ask more details, i can give.
regards,
kailash
Siemens Line Differential Relay Testing (Siprotec 7SD522)
