ABB Relion 670 Series Applications Manual page 136

Section 8
Current protection
This protection function must operate only in a selective way. So check all system and transient
conditions that could cause its unwanted operation.
Only detailed network studies can determine the operating conditions under which the highest
possible fault current is expected on the line. In most cases, this current appears during three-
phase fault conditions. But also examine single-phase-to-ground and two-phase-to-ground
conditions.
Also study transients that could cause a high increase of the line current for short times. A typical
example is a transmission line with a power transformer at the remote end, which can cause high
inrush current when connected to the network and can thus also cause the operation of the built-
in, instantaneous, overcurrent protection.
Common base IED values for primary current (
( SBase ) are set in the global base values for settings function GBASVAL.
GlobalBaseSel : This is used to select GBASVAL function for reference of base values.
Operation : Set the protection to On / Off .
OpModeSel : This parameter can be set to 2 out of 3 or 1 out of 3 . The setting controls the
minimum number of phase currents that must be larger than the set operate current
operation. Normally this parameter is set to
protection is to be used mainly for multi phase faults,
Pickup : Set operate current in % of IB .
IP>>Max and IP>>Min should only be changed if remote setting of operation current level, IP>> , is
used. The limits are used for decreasing the used range of the
IP>>Max and IP>>Min , the closest of the limits to IP>> is used by the function. If IP>>Max is smaller
IP>>Min , the limits are swapped.
than
MultPU : The set operate current can be changed by activation of the binary input MULTPU to the
set factor
8.1.3.1 Meshed network without parallel line
The following fault calculations have to be done for three-phase, single-phase-to-ground and two-
phase-to-ground faults. With reference to Figure 56, apply a fault in B and then calculate the
current through-fault phase current I
impedance values for Z
maximum through fault current from A to B.
130
MultPU .
and the maximum source impedance values for Z
A
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IBase ), primary voltage ( UBase ) and primary power
1 out of 3 and will thus detect all fault types. If the
2 out of 3 should be chosen.
. The calculation should be done using the minimum source
fB
1MRK 511 401-UUS F
Pickup for
IP>> setting. If IP>> is set outside
in order to get the
B
Bay control REC670
Application manual
M12915-9 v8