Parameter: UV Guard Inhibit
•
Default setting: Yes
Function elements can be blocked if all phase voltages fall below setting.
Settings Example
Negative Phase Sequence (NPS) protection detects phase unbalances and is widely used in protecting rotating
plant such as motors and generators. However such protection is almost universally based on detecting NPS
current rather than voltage. This is because the NPS impedance of motors etc. is significantly less than the
Positive Phase Sequence (PPS) impedance and therefore the ratio of NPS to PPS current is much higher than
the equivalent NPS:PPS voltage ratio.
NPS voltage is used for monitoring busbar supply quality rather than detecting system faults. The presence of
NPS voltage is due to unbalanced load on a system. Any system voltage abnormality is important since it will
affect every motor connected to the source of supply and can result in mass failures in an industrial plant. NPS
voltage function elements can be used as alarms to indicate that the level of NPS has reached abnormal levels.
Remedial action can then be taken, such as introducing a balancer network of capacitors and inductors. Very
high levels of NPS voltage indicate incorrect phase sequence due to an incorrect connection.
Settings Menu
Configuration > Function Config
Parameter Setting Options Settings
Default Gn1 Gn2 Gn3 Gn4
47 Sequence Voltage Disabled
Enabled
Disabled
Functions > Protection > 47 > Gn 47 Common
Parameter Setting Options Settings
Default Gn1 Gn2 Gn3 Gn4
UV Guard Setting 1 to 200 V, Δ 0.5 V 5 V
Functions > Protection > 47 > Gn 47-n
Parameter Setting Options Settings
Default Gn1 Gn2 Gn3 Gn4
Element Disabled
Enabled
Disabled
Measurement NPS (V2)
PPS (V1)
ZPS (V0)
NPS
Setting 1 to 200 V, Δ 0.5 V 20 V
Hysteresis 0 to 80 %, Δ 1 % 3 %
Delay 0 to 20 s Δ 0.01 s,
20 to 100 s Δ 0.1 s,
100 to 1000 s Δ 1 s,
1000 to 10000 s Δ 10 s,
10000 to 14400 s Δ 100 s
1 s
VTS Inhibit No
Yes
No
UV Guard Inhibit No
Yes
Yes
5.9.5
Protection and Automation Functions
5.9 47 Sequence Overvoltage Protection
198 Reyrolle 7SR5, Overcurrent Protection Device, Device Manual
C53000-G7040-C014-1, Edition 11.2019
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