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Operation and characteristic
2.10.1
The ICD function examines the ratio of a second harmonic current (I2f) to the fundamental
current (I1f) in each phase. If the ratio | I
function is able to identify the presence of inrush currents. Figure 2.10-1 illustrates the
characteristic; the operation region is designated by the hatched area; the operation threshold
is set with the [ICD-OC].
I 2f
0
ICD–OC
Figure 2.10-1 ICD characteristic and operation region
As shown in Figure 2.10-1, the user should set both the [ICD-2f] and [ICD-OC] when the
second harmonic inrush current should be detected. The user should set On for the scheme
switch [ICD-EN] to enable the ICD operation.
Scheme logic
2.10.2
Figure 2.10-2 illustrates the ICD logic. When second harmonic inrush current is detected, the
ICD signal will be received by other protection functional elements.
A
ICD
B
C
is larger than the setting [ICD-2f], the ICD
| | I
⁄
|
2f
1f
ICD-2f (%) = tanθ×100
|I 2f |/|I 1f |ICD-2f(%)
|I 1f |ICD–OC
θ
I 1f
8000001C20
8100001C21
8200001C22
8300001C23
≥1
Figure 2.10-2 ICD logic
- 128 -
&
ICD
To OC, SOTF-OC
ICD-A
ICD-B
ICD-C
To EF, OCN, BCD, SEF
ICD-OR
6F2T0207 (0.01)
GRE200 (5,6)
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