Siemens 7SR51 - 6.3 60 VTS VT Supervision

60VTS VT Supervision
Overview of Functions
The 60VTS Voltage Transformer Supervision function is used to:
•
Detect the loss of voltage supply due to VT fuse operation on 1, 2 or 3 phases
•
Provide a delayed alarm for indication purposes
•
Can be used to automatically inhibit protection elements that could be adversely affected by the resulting
erroneous voltage
•
Can be used to automatically switch directional protection elements to be non-directional during failed
fuse conditions
Structure of the Function
The VT supervision function has group dependent settings. These settings can be different in each settings
group – group numbers (Gn) 1 to 4.
The function monitors the VT using the 3 phase VT inputs e.g. VT1/2/3 and 3 phase CT inputs e.g. CT1/2/3. The
fundamental frequency component are measured from processing of the measured samples.
The pickup output from the 60VTS function element is used internally to block selected protection elements.
1 or 2 Phase Failure Detection
The presence of negative phase sequence (NPS) or zero phase sequence (ZPS) voltage in a power system is
normally accompanied by NPS or ZPS current. The presence NPS or ZPS voltages without the corresponding
level of NPS or ZPS current can indicate a failure of 1 or 2 VT phases.
3 Phase Failure Detection
During normal load conditions PPS voltage and PPS load currents are measured within operating limits. Meas-
urement of PPS load without corresponding PPS voltage can indicate 3 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 VT is considered to have failed where positive sequence voltage is below 60VTS V
1
while positive
sequence current is above I
1
load and below I
1
fault level.
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 V
1
setting while NPS or ZPS voltage is below V 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
6.3
6.3.1
6.3.2
Supervision Functions
6.3 60VTS VT Supervision
Reyrolle 7SR5, Overcurrent Protection Device, Device Manual 379
C53000-G7040-C014-1, Edition 11.2019