7SR210 & 7SR220 Applications Guide
© 2013 Siemens Protection Devices Limited
Page 27 of 48
2.14 Neutral Overvoltage (59N)
Neutral Overvoltage Displacement (Residual Overvoltage) protection is used to detect an earth fault where little or
no earth current flows.
This can occur where a feeder has been tripped at its HV side for an earth fault, but the circuit is still energised
from the LV side via an unearthed transformer winding. Insufficient earth current would be present to cause a trip,
but residual voltage would increase significantly; reaching up to 3-times the normal phase-earth voltage level.
If Neutral Overvoltage protection is used, it must be suitably time graded with other protections in order to prevent
unwanted tripping for external system earth faults.
Figure 2.14-1
NVD Application
Typically NVD protection measures the residual voltage (3V
0
) directly from an open delta VT or from capacitor
cones – see fig. 2.13-2 below.
Figure 2.14-2
NVD Protection Connections
Summary of Contents for Argus 7SR21
Page 1: ...Energy Management 7SR21 7SR22 Argus Overcurrent Relay Reyrolle Protection Devices ...
Page 2: ......
Page 4: ...Contents 7SR11 and 7SR12 Page 2 of 2 2018 Siemens Protection Devices Limited ...
Page 185: ...7SR210 Settings Guide Unrestricted 2018 Siemens Protection Devices Limited Page 61 of 61 ...
Page 277: ...7SR220 Settings Guide Unrestricted Page 72 of 107 2013 Siemens Protection Devices Limited ...
Page 382: ...7SR220 Technical Manual Chapter 4 Page 2 of 96 2017 Siemens Protection Devices Limited ...
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