Hitachi 670 Series Application Manual page 45

1MRK505382-UEN Rev. K
Table 3:
Station
Type of fault
Object
Setting
Characteristic
High set stage
It is important to achieve a proper back-up protection. The short circuit protection on the outgoing
bays and on the LV side of the transformer are set according to a prepared selectivity chart. An
example in Figure
and Normal Inverse has k=0.12 to give back-up to outgoing bays' relays which are extremely inverse
and selective to remote fuses.
IEC14000047 V1 EN-US
Figure 39:
Communication set-up, 670/650 series
Application Guide
Backup protection example data
Tap transformer 10 MVA
Three phase fault
1 = 10 kV Line A
2 MVA
IEC Extr.inverse, k=0.5, A=80,
p=2
14 MVA
39 shows that the setting of the short circuit protection on the LV side is 14 MVA,
Selectivity chart
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Analog and binary signal transfer for line differential protection
2 = T1 10 kV 50/51
14 MVA
IEC Norm.inverse k=0.12,
A=0.14, p=0.02
- - - -
IEC14000047 -1-en.ai
Section 4
3 = 130 kV 87L
(ImaxAddDelay)
20 MVA
IEC Norm.inverse k=0.18,
A=0.14, p=0.02
- - - -
39