Toshiba GR-200-5 Instruction Manual page 295

Detection of current change (OCD)
2.24.4
Current change detection relay
(i)
Suppose that the difference exists between the latest current phasor (I
phasor (I ). The OCD function can operate if the difference is larger than setting [OCD]. The
N
I can be measured for the last two-cycles; the difference is decided using Equation (2.24-1):
N
where the decision criteria is given by pick-up threshold value (I s ).
The pick-up threshold is set using the setting [OCD].
OCD logic
(ii)
Figure 2.24-5 shows the OCD logic and its output signals.
A
OCD B
C
Figure 2.24-5 Current change check relay logic
| ��
− ��
�� ��
I
M
I
N
Figure 2.24-4 Current change detection
8000001B66
8100001B67
8200001B68
- 275 -
| > ��
��
I
S
8000001B6F
0 t
8100001B70
0 t
8200001B71
0 t
0.1s
6F2T0207 (0.01)
) and the last current
M
(2.24-1)
To Common, DEFCAR
To VTF
OCD-A
OCD-B
OCD-C
GRE200 (5,6)