Toshiba GR200 Series Instruction Manual page 73

this case a fault that evolves from an external fault to an internal fault.
Current
Differential Element
Input
(DIFL)
Waveform Discriminating
Element (WDE)
Starting Element (SE)
Evolving fault detection
element (EVD)
Figure 2.4-1 Differential element with CT saturation countermeasure
The algorithm used in this element is given by Equations (2.4-1) to (2.4-3):
where,
ΔId: Change in the differential current Id
(ΔIp + ΔIn): Change in the restraining current in the positive and negative half cycles
Id: Differential current
Ip: Sum of positive input currents
In: Sum of negative input currents
m, m-1, m-2: Sampling timing
The SE will operate when the sum of the absolute values of the difference between the
instantaneous values of current data from one cycle is greater than a specified percentage of
minDIF-I.
where,
I j : Current at j
minDIF-I: A minimum value of between settings [DIFL-I1] and [DIFL-I2]
Starter
∆Id < 0.15 × ( ∆Ip + ∆In )
∆Id = | ����
− ����
�� ��−1
∆���� + ∆���� = | ����
− ����
�� ��−1
+ | ����
��
�� − �� > 0.5 × min DIF– I
�� ( ��−1���������� )
����
- 50 -
&
0
t
&
3 cycles
CTSC
t
0
1 cycle
| + | ���� |
− ����
��−1 ��−2
| + | ���� |
− ����
��−1 ��−2
− ���� | + | ���� − ����
��−1 ��−1
6F2S1914 (0.49)
Tripping
Output
&
EVD
(2.4-1)
(2.4-2)
(2.4-3)
|
��−2
(2.4-4)
GRL200 (Soft 033 & 037)