• setting RCADir to value +65 degrees, that is, the negative sequence current
typically lags the inverted negative sequence voltage for this angle during the
fault
• setting ROADir to value 90 degrees
• setting LowVolt_VM to value 2%, that is, the negative sequence voltage level
above which the directional element will be enabled
• setting Operation_OC1 to On
• setting StartCurr_OC1 to value between 3-10%, (typical values)
• setting tDef_OC1 to insure proper time coordination with other earth-fault
protections installed in the vicinity of this power line
• setting DirMode_OC1 to Forward
• setting DirPrinc_OC1 to IcosPhi&U
• setting ActLowVolt1_VM to Block
DNSPTOC is used in directional comparison protection scheme for the power line
protection, when communication channels to the remote end of this power line are
available. In that case, two negative sequence overcurrent steps are required - one in
forward and another in reverse direction. The OC1 stage is used to detect faults in
forward direction and the OC2 stage is used to detect faults in reverse direction.
However, the following must be noted for such application:
• setting RCADir and ROADir are applicable for both steps OC1 and OC2
• setting DirMode_OC1 must be set to Forward
• setting DirMode_OC2 must be set to Reverse
• setting StartCurr_OC2 must be made more sensitive than pickup value of the
forward OC1 element, that is, typically 60% of StartCurr_OC1 set pickup level
in order to insure proper operation of the directional comparison scheme during
current reversal situations
• the start signals STOC1 and STOC2 from OC1 and OC2 elements is used to send
forward and reverse signals to the remote end of the power line
• the available scheme communications function block within IED is used between
the protection function and the teleprotection communication equipment, in
order to insure proper conditioning of the above two start signals.
ActLowVolt1 and ActLowVolt2 should not be set to Memory.
1MRK 505 291-UEN A Section 6
Current protection
153
Application manual
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