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GUID-B455F553-4F09-442D-9297-4262002D5D07 V2 EN
Figure 411:
Fault loop impedance for phase-to-ground fault loops “AG Fault”, “BG
Fault” or “CG Fault”
The ground-fault distance calculation algorithm is selected with setting
EF algorithm Sel
.
Options for the selection are “Load compensation” and “Load modelling”. For the correct
operation of both algorithms there should not be any zero-sequence current sources, for
example, grounding transformers, in front of the protection relay location.
The “Load compensation” algorithm utilizes symmetrical components to compensate for
the effect of load on the measured voltages and currents. In case of radial feeders, this
algorithm should be selected with low-impedance/effectively grounded systems where
the fault current is fed from one side only and there are no in-feeds along the protected line.
The “Load modelling” algorithm takes into account the effect of the load in the measured
currents and voltages by considering it in the fault loop model. In case of radial feeders,
this algorithm can be applied with low-impedance/effectively grounded systems where
the fault current is fed from one side only. The “Load modelling” algorithm has been
especially designed for ungrounded systems.
The “Load modelling” algorithm requires the
Equivalent load Dis
setting, that is, an
equivalent load distance, as an additional parameter. The derivation and meaning of this
parameter is illustrated in
, where the load is assumed to be evenly distributed
along the feeder, resulting in the actual voltage drop curve as seen in the middle part of
.
In case of evenly distributed load,
Equivalent load Dis
~ 0.5. When the load is tapped at
the end of the feeder,
Equivalent load Dis
= 1.0. If the load distribution is unknown, a
default value of 0.5 can be used for
Equivalent load Dis
.
The maximum value of the voltage drop, denoted as V
drop
(real), appears at the end of the
feeder. The
Equivalent load Dis
parameter is the distance at which a single load tap
corresponding to the total load of the feeder would result in a voltage drop equal to
V
drop
(real). The dashed curve shows the voltage drop profile in this case.
Section 5
1MAC059074-MB A
Protection related functions
808
615 series ANSI
Technical Manual
Содержание Relion 615 series
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