ABB REL670 2.2 IEC, Applications Manual

Page: 412 / 908

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.
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-US
(Equation 401)
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.
8.13.4.11 ZMMMXU settings
GUID-760E7792-1BA4-47B3-A437-1C7777425F57 v1
ZZeroDb
Section 8
1MRK 506 369-UEN B
Impedance protection
406 Line distance protection REL670 2.2 IEC
Application manual