Toshiba GR200 Series - 2.23 Earth fault overvoltage protection (OVG)

6F2S1914 (0.49)
GRL200 (Soft 033 & 037)
- 316 -
Earth fault overvoltage protection (OVG)
The earth fault overvoltage protection (OVG) function has two stages (OVG1 and OVG2); and
the time characteristic of each stage can be taken from either definite time or inverse definite
minimum time. The purpose of each stage of the OVG is to detect earth fault on unearthed,
resistance-earthed system or AC generators.
The low voltage setting, which may be applied for an OVG element, is susceptible to any
third harmonic component that may be superimposed on an input signal. Therefore, the
function incorporates the filter to suppress the third harmonic component.
To simplify the description, only OVG1 is discussed but is applicable to OVG2; hence,
read the expression for OVG1 as OVG2 for the OVG 2nd stage unless a special explanation or
instruction has been provided.
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Note: Several IED models do not have phase-phase over-voltage protection features. To
determine whether the features are implemented in the IED or not, locate the IED ordering
number; and check the order number at “G&T position” referring to the comparison table below.
For more information, see Appendix: Ordering .
Table 2.23-1 Comparative table in respective ordering numbers
feature
Ordering No. at “G&T”
33
37
OVG
Earth fault over-voltage protection
✓
✓
✓: Applicable NA: Not applicable