ABB RELION RET670, Applications Manual

Page: 453 / 1016

OperationSC
Choose the setting value SeriesComp if the protected line or adjacent lines are
compensated with series capacitors. Otherwise maintain the NoSeriesComp setting
value.
CVTtype
If possible, the type of capacitive voltage transformer (CVT) that is used for
measurement should be identified. Note that the alternatives are strongly related to the
type of ferro-resonance suppression circuit that is included in the CVT. There are two
main choices:
Passive type For CVTs that use a non-linear component, like a saturable inductor, to limit overvoltages
(caused by ferro-resonance). This component is practically idle during normal load and
fault conditions, hence the name ‘passive’. CVTs that have a high resistive burden to
mitigate ferro-resonance also fall in to this category.
Any
This option is primarily related to the so-called active type CVT, which uses a set of
reactive components to form a filter circuit that essentially attenuates frequencies other
than the nominal in order to restrain the ferro-resonance. The name ‘active’ refers to the
fact that this circuit is always involved during transient conditions, regardless of voltage
level. This option should also be used for types that do not fall under the other two
categories, for example, CVTs with power electronic damping devices, or if the type cannot
be identified at all.
None
(Magnetic)
This option should be selected if the voltage transformer is fully magnetic.
3I0Enable_PG
This setting opens up an opportunity to enable phase-to-ground measurement for
phase-to-phase-ground faults. It determines the level of residual current (3I0) above
which phase-to-ground measurement is activated (and phase-to-phase measurement is
blocked). The relations are defined by the following equation.
0 max
3I0Enable _ PG
3
100
ph
I
I I
× ³ ×
EQUATION2548-ANSI V1 EN-US
(Equation 369)
Where:
3I0Enable_P
G
is the setting for the minimum residual current needed to enable operation in the phase-to-
ground fault loops in %
Iphmax is the maximum phase current in any of three phases
By default this setting is set excessively high to always enable phase-to-phase
measurement for phase-to-phase-ground faults. Maintain this default setting value
1MRK 504 163-UUS A
Section 8
Impedance protection
Transformer protection RET670 2.2 ANSI 447
Application manual