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Parameter: Element
•
Default setting: Disabled
This setting is used to allow the element to be switched on and off if it is not required. A separate setting
is provided for each element. These settings can be used to select the number of elements required.
Parameter: 47‑n Input Selection
•
Default setting: NPS (V
Parameter Value
PPS (V
)
1
NPS (V
)
2
ZPS (V
)
0
Parameter: Setting
•
Default setting: 20 V
This is the pickup threshold of the element and is compared against the respective sequence voltage. For
PPS (V
) this would usually set at a level higher than rated system voltage or lower if the overvoltage
1
element is to be used in logic to provide positive sequence undervoltage monitoring. For negative or zero
phase sequence voltages this is usually set at a lower level because there voltages are negligible during
normal system running conditions. For earth fault or residual voltage detection the setting is in zero
phase sequence volts (ZPS) and therefore 1/3 of the residual voltage (3V
suit the individual application.
Parameter: Hysteresis
•
Default setting: 3 %
The element will reset when the voltage recovers to the 47-n setting minus the 47-n hysteresis setting.
The default setting of 3 % is generally enough to avoid chatter of the element but care may be required
for settings which are close to the nominal value when set to PPS (V
reset when the voltage recovers to nominal value as the voltage is still in the hysteresis window.
Parameter: Delay
•
Default setting: 1 s
This is the time delay setting for the DTL element. This should be set to suit the individual application.
Parameter: VTS Inhibit
•
Default setting: No
This setting defines the effect of a voltage transformer failure on the operation of each 47-n function
element. If a VT failure is detected by the separate VTS element, operation of the 47-n element will be
blocked if this setting is set to Yes. If this setting is set to No, the 47‑n element is unaffected by the VTS
element operation and the 47‑n element may operate on the erroneous voltage caused by the VT fuse
failure. It is generally recommended that a setting of Yes is beneficial if the input selection is set to NPS
or ZPS.
Reyrolle 7SR5, Overcurrent Protection Device, Device Manual
C53000-G7040-C014-1, Edition 11.2019
)
2
Description
Positive sequence can be used to detect underlying overvoltage on the system.
This measurement is immune to distortion of voltage values due to imbalance.
Negative sequence can be used to detect unbalance between phases. Unbal-
anced voltage gives rise to unbalanced current flows.
Zero sequence is a measurement of residual voltage. This drives current in
through the neutral or system earth connections.
Protection and Automation Functions
5.9 47 Sequence Overvoltage Protection
). The elements should be set to
0
) otherwise the element may not
1
197
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