7PG2113/4/5/6 Solkor Description of Operation
6.2
VT Supervision (60VTS) – 7PG2114/6
1 or 2 Phase Failure Detection
Normally the presence of negative phase sequence (NPS) or zero phase sequence (ZPS) voltage in a power
system is accompanied by NPS or ZPS current. The presence of either of these sequence voltages without the
equivalent level of the appropriate sequence current is used to indicate a failure of one or two VT phases.
The
60VTS Component
setting selects the method used for the detection of loss of 1 or 2 VT phases i.e.
ZPS
or
NPS
components. The sequence component voltage is derived from the line voltages; suitable VT connections
must be available. The relay utilises fundamental voltage measurement values for this function.
The element has user settings
60VTS V
and
60VTS I.
A VT is considered to have failed where the voltage
exceeds
60VTS V
while the current is below
60VTS I
for a time greater than
60VTS Delay
.
3 Phase Failure Detection
Under normal load conditions rated PPS voltage would be expected along with a PPS load current within the
circuit rating. Where PPS load current is detected without corresponding PPS voltage this could indicate a three
phase VT failure. To ensure these conditions are not caused by a 3 phase fault the PPS current must also be
below the fault level.
The element has a
60VTS VPPS
setting, an
60VTS IPPS Load
setting and a setting for
60VTS IPPS Fault
. A VT
is considered to have failed where positive sequence voltage is below
60VTS VPPS
while positive sequence
current is above
IPPS Load
and below
IPPS Fault
level for more than
60VTS Delay.
External MCB
A binary input can be set as
Ext_Trig 60VTS
to allow the
60VTS Delay
element to be started from an external
MCB operating.
Once a VT failure condition has occurred the output is latched on and is reset by any of the following:-
Voltage is restored to a healthy state i.e. above
VPPS
setting while NPS voltage is below
VNPS
setting.
Ext Reset 60VTS
A binary or virtual input, or function key and a VT failure condition no longer
exists.
Inhibit 60VTS
A binary or virtual input.
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