Setting of minimum operate currents
The operation of the distance function will be blocked if the magnitude of the currents is
below the set value of the parameter IMinOpPP and IMinOpPG.
The default setting of IMinOpPP and IMinOpPG is 15% of IBase. The values have been
proven in practice to be suitable in most of the applications. However, there might be
applications where it is necessary to increase the sensitivity by reducing the minimum
operate current down to 10% of IBase. This happens especially in cases, when the IED
serves as a remote back-up protection on series of very long transmission lines.
The minimum operate fault current is automatically reduced to 75% of its set value, if the
distance protection zone has been set for the operation in reverse direction.
Setting of timers for distance protection zones
The required time delays for different distance protection zones are independent of each
other (if TimerSelZx is set to Timers seperated). Distance protection zone 1 can also have
a time delay, if so required for selectivity reasons. Time delays for all zones can be set in
a range of 0 to 60 seconds. The tripping function of each particular zone can be inhibited
by setting the corresponding OpModetPGZx and OpModetPPZx (where x is 1-5
depending on selected zone) parameter to Disabled. Different time delays are possible for
the phase-to-ground tPGZx (where x is 1-5 depending on selected zone) and for the phase-
to-phase tPPZx (where x is 1-5 depending on the selected zone) measuring loops in each
distance protection zone separately, to further increase the total flexibility of a distance
protection. OpModetPGZx and OpModetPPZx must be set to Enabled even if the time
delays tPGZx and tPPZx are set to 0 s.
The zone timer handler feature in ZQMPDIS (21) uses the parameter TimerSelZx (where x
is 1-5 depending on the selected zone) to enable the timer selection for the different zones.
Different signals or combination of different signals are possible to start the timers for the
zones.
• Timers separated - Separate start of timers from individual start phase to ground and
phase to phase measurement loops
• Timers linked - Start of timers linked within zone, either phase to ground or phase to
phase will start all the timers within zone
• Internal start - Internal common start of function of all the 5 zones
• Start from PhSel - Common start of timers from phSelLogic Start signal, if direction
condition is forward for the particular phase and also the zone is set for DirModeZx
setting as Forward
• External start - External common start of timers
1MRK 506 334-UUS A Section 6
Impedance protection
135
Application manual
To Next Page
Loading...
