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.
INReleasePE
This setting opens up an opportunity to enable phase-to-earth measurement for phase-
to-phase-earth faults. It determines the level of residual current (3I0) above which
phase-to-earth measurement is activated (and phase-to-phase measurement is
blocked). The relations are defined by the following equation.
0 max
Re
3
100
ph
IN leasePE
I I× ³ ×
EQUATION2548 V1 EN (Equation 148)
Where:
INReleaseP
E
is the setting for the minimum residual current needed to enable operation in the phase-
to-earth 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-earth faults. Maintain this default setting value
unless there are very specific reasons to enable phase-to-earth measurement. Please
note that, even with the default setting value, phase-to-earth measurement is activated
whenever appropriate, like in the case of simultaneous faults: two earth faults at the
same time, one each on the two circuits of a double line.
8.4 Pole slip protection PSPPPAM
1MRK 502 071-UEN - Section 8
Impedance protection
Generator protection REG670 2.2 IEC and Injection equipment REX060, REX061, REX062 261
Application manual
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