Inverse Time Overcurrent Element Oci And Efi - Toshiba GRT100 Series Instruction Manual

L.)
I = |1kct1I
d 1o
I = max.( |1kct1I
r
|1kct3I
where,
I , I , I : residual current of primary, secondary and tertiary winding
1o 2o 3o
I , I , I , I , I
1a 1b 1c 2a
I : residual current of neutral circuit
N
1kct1, 1kct2, 1kct3: CT ratio matching of primary, secondary and tertiary line CT to neutral
Characteristic DF2 is expressed by the following equation:
 p2 (I kp)
I
d r
where
p2: slope of DF2
kp: break point of DF1 characteristic

2.11.4 Inverse Time Overcurrent Element OCI and EFI

The OCI and EFI elements have one long time inverse characteristic and three inverse time
characteristics in conformity with IEC 60255-3 as shown in Figure 2.11.3. One of these
characteristics can be selected.
These characteristics are expressed by the following equations.
Long Time Inverse
t = T 
(I/Is)1
Standard Inverse

t = T
(I/Is)
Very Inverse
t = T 
(I/Is)
Extremely Inverse
t = T 
(I/Is)
where,
t : operating time
I : fault current
Is : current setting
T : time multiplier setting
+ 1kct2I + 1kct3I + I
2o 3o
|, |1kct1I |, |I1kct1I
1a 1b
|, |kct3I |, |I |)
3b 3c N
, I , I , I , I : phase current of primary, secondary and tertiary winding
2b 2c 3a 3b 3c
CT
120
0.14
0.02
 1
13.5
 1
80
2
 1
 40 
|
N
|, |1kct2I |, |1kct2I
1c 2a
6 F 2 S 0 7 8 9
|, |1kct2I |, |1kct3I
2b 2c 3a
|,