IEC06000062-2-en.vsdx
OperLevel
Slope (settable)
I
out
[Primary Amps]
I
d
[Primary Amps
]
Operate
region
IEC06000062 V2 EN-US
Figure 41: Check zone operation characteristic
The built-in check zone feature has to be enabled (that is, setting parameter
Operation
shall be
set to
On
) in order to fully enable the check zone. For substations where traditional “CT
switching” is not required (that is, single busbar station or one-and-half breaker station), a
check zone must not be used. For such applications, the check zone shall be disabled by the
setting parameter
Operation
to
Off
.
The check zone measures only the currents from the bays which leaves the station. Exactly
which CTs shall be measured by the check zone varies, depending on the version of the IED
used:
• In two-zone busbar differential protections, it is freely settable by using the setting
CheckZoneSel
at each bay function block.
• In six-zone busbar differential protection, the currents of all active feeder bays are
measured unconditionally by the check zone, if the check zone is able to operate. By an
active feeder, we mean a feeder bay which is not deactivated, that is, neither its
operMode
is
Off
nor it is out of service.
And the check zone supervises differential protection zones. Exactly which differential
protection zones shall be supervised by the operation of the check zone also varies, depending
on the version of the IED used:
• In two-zone busbar differential protections, freely settable by using a setting
CheckZoneSup
at each zone function block,
• In six-zone busbar differential protection, all active protection zones are supervised
unconditionally by the check zone, if the check zone is able to operate. By an active
protection zone, we mean a zone which both is enabled and used/connected to at least
one CT.
Moreover, there are some additional features only available for six-zone busbar differential
protection, for example, the possibilities to externally block the check zone operation.
Please also refer to “Check zone protection” in Technical reference manual, for more details
about the check zone.
6.1.3.4 Switch status monitoring
M12107-3 v4
The so-called CT switching (that is, zone selection) is required in situation when one particular
circuit (that is, bay) can be connected to different busbars by individual disconnectors. Typical
example is a station with double busbars with or without transfer bus as shown in Figure
61,
1MRK 505 370-UEN D Section 6
Differential protection
Busbar protection REB670 97
Application manual
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