Phase-to-phase current variation takes the current samples
as input and it calculates the variation using the sampling
value based algorithm. Phase-to-phase current variation
function is a major one to fulfill the objectives of the startup
element.
Zero sequence criterion takes the zero sequence current as
input. It increases the security of protection during the high
impedance fault conditions.
Low voltage criterion takes the phase voltages and phase-
to-phase voltages as inputs. It increases the security of
protection when the three-phase fault occurred on the weak
end side.
Low current criterion takes the phase currents as inputs and
it increases the dependability during the switch onto fault
case of unloaded line.
The differential function can be allowed to trip as no load is
fed through the line and protection is not working correctly.
Features:
• Startup element is sensitive enough to detect the
abnormal status of the protected system
• Startup element does not influence the operation speed of
main protection
• Startup element would detect the evolving faults, high
impedance faults and three phase fault on weak side
• It is possible to block the each sub function of startup
element
• Startup signal has a settable pulse time
5. Impedance protection
Distance protection zone, quadrilateral characteristic
ZMQPDIS, ZMQAPDIS
M13787-3 v15
The line distance protection is an up to five (depending on
product variant) zone full scheme protection function with
three fault loops for phase-to-phase faults and three fault
loops for phase-to-earth faults for each of the independent
zones. Individual settings for each zone in resistive and
reactive reach gives flexibility for use as back-up protection
for transformer connected to overhead lines and cables of
different types and lengths.
Distance measuring zone, quadrilateral characteristic
(ZMQPDIS) together with Phase selection with load
encroachment (FDPSPDIS) has functionality for load
encroachment, which increases the possibility to detect high
resistive faults on heavily loaded lines, as shown in figure
.
en05000034.vsd
R
X
Forward
operation
Reverse
operation
IEC05000034 V1 EN-US
Figure 11. Typical quadrilateral distance protection zone with Phase
selection with load encroachment function FDPSPDIS
activated
The independent measurement of impedance for each fault
loop together with a sensitive and reliable built-in phase
selection makes the function suitable in applications with
single-phase autoreclosing.
Built-in adaptive load compensation algorithm prevents
overreaching of zone 1 at load exporting end at phase-to-
earth faults on heavily loaded power lines.
The distance protection zones can operate independently of
each other in directional (forward or reverse) or non-
directional mode. This makes them suitable, together with
different communication schemes, for the protection of
power lines and cables in complex network configurations,
such as parallel lines, multi-terminal lines.
Line differential protection RED670
1MRK 505 379-BEN R
Version 2.2
36
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