Toshiba GR200 Series Instruction Manual page 79

Extended application
2.1.5
Switch-onto-fault (SOTF)
(i)
If a dead line has a fault prior to energization the CB should trip quickly upon when the line
is energized. To trip the CB when the faulted line is energized, a switch-onto-fault (SOTF)
protection function is provided. This function is armed for a certain period after the CB is
closed.
1
The SOTF function can operate, in the case when a line remains in a non-energized state
for a certain time, which is termed as the deadline time defined by the protection common
(PROT_COMMON
If Z*S is required to operate for the SOTF function, On is set for the scheme switch [Z*S-
SOTF]. When Z*S is not required to operate for the SOTF operation, the scheme switch is set
to Off.
The SOTF function is provided for all of the ZS/ZG elements; hence, all of the elements
are provided with similar scheme switches and these switches are termed "SOTF" with the
zone names [Z*S-SOTF] for ZS, [Z*G-SOTF] for ZG.
Note: The distance- measuring element can operate for faults other than close-up three-
1
phase faults.
Note: The operation and settings of the PROT_COMMON is described separately, (See
2
Chapter
Blocking all phase-ground elements
(ii)
Each Z*G zone has an option to block all phase-ground elements from operating if more than
one phase is involved in a ground fault. This is achieved using settings [Z1G-MPFBlk], [Z1XG-
MPFBlk], [Z2G-MPFBlk], [Z3G-MPFBlk], [Z4G-MPFBlk], [Z5G-MPFBlk]. When any of these
settings are set to Block, the associated zone phase-ground elements will only operate in the
event of a single phase to ground fault. On the other hand, where more than one phase is
involved, the phase-ground elements are blocked, allowing the phase-phase elements to detect
the fault & trip.
Enhancing the detection of faulted-phases
(iii)
Faulted phase can be detected by 'Covering zones', which are independent distance elements
designed solely for enhancing the faulted phase detection. This 'Covering zone' is not used for
the determination of the fault location. The 'Covering zones' does not have zero-sequence
compensation; accordingly, the faulted phase(s) can be determined more securely.
) function.
2
Relay application: Protection common
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6F2S1915 (0.46)
)
GRZ200 (Soft 031 & 032)