Mitsubishi Electric MELPRO-A Series Instruction Manual page 15

【Lead-out cable】
No. Shield grounding method
電源側 ZCT
CB
1
Ic
GR
外部事故
2
3
4
5
Capacitance and charging current
System voltage
6.6
kV
Charging current (Ic)
Ic=2πfCE (A)
Grounding protection of
cable itself
ｹｰﾌﾞﾙ
Within the protection
ﾍｯﾄﾞ
ｼｰﾙﾄﾞ
range. The GR operates.
ｱｰｽ
Same as No.1
Same as No.1
Within the protection
range. However, as the
earth fault current is
divided and separately
flows to two grounding
points, the detection
sensitivity is lowered.
Within the protection
range. But the GR does
not operate.
Form
3-wire
(3-wire bundle～earth)
Single wire
Ic: 3-wire bundle charging current (A)
f : Frequency (Hz)
C : 3-wire bundle capacitance (F)
E : Voltage to ground (V)
Effect of charging
current (Ic) in the
event of external
grounding fault
○
Charging current flows
through ZCT. So the GR
may operate in the
case of large charging
current.
○
Same as No.1
○ △
Same as No.1
△
Same as No.1.
Moreover, because of
potential difference
between grounding
points, circulating
current may cause the
GR to operate when the
low-voltage circuit
has a ground fault.
×
Charging current does
not pass through ZCT.
So the GR does not
operate.
6600V cross-linked polyethylene cable
Cross section (CV,CE,EM-CE,CVT,CET,EM-CET)
area
2
(mm )
Capacitance
(μF/km)
8 0.63
14 0.72
22 0.81
38 0.96
60 1.11
100 1.35
150 1.56
200 1.53
250 1.65
8 0.21
14 0.24
22 0.27
38 0.32
60 0.37
100 0.45
150 0.52
200 0.51
250 0.55
For single wire, the charging current of single wire is shown.
The charging current shown the table is in the case of 60Hz.
For 50Hz, it should be 5/6 times.
The capacitance value is based on the specification of JIS C
3606 (2003).
15
Consideration
△ If the charging
current is large,
use a DGR.
△ Same as No.1
Same as No.1
× Not recommended
○ Same as No.4
JIS C 3606
Charging current
(A/km)
0.905
1.034
1.163
1.379
1.594
1.939
2.241
2.198
2.370
0.302
0.345
0.388
0.460
0.531
0.646
0.747
0.733
0.790
Evaluation
○
○
△
×
×
JEP0-IL9555