Toshiba GR200 Series Instruction Manual page 55

Quad element
For the element for the fault in phase-bc, the polarizing voltage (Vp bc ) is given using
Equation (2.1-29):
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For the element for the fault in phase-a, the polarizing voltage (Vp a ) is given using
Equation (2.1-30):
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where,
V 0 = voltage in zero-sequence
Va = voltage in phase-A
Vbc = voltage in phase-bc
In Equation (2.1-29), the Vp bc voltage is subject to the memory action if the close-in fault
occurs in three-phases; that is, the values of the Va and Vbc voltages are set from the pre-fault
voltages. The memory is retained for two cycles after the fault occurs. Note that the polarizing
voltage (Vpa) in Equation (2.1-30) is not subject to the memory action.
If a close-in fault in three-phases occurs, the Quad element can be enhanced for an offset
Quad element, as shown in Figure 2.1-10. Similar to issuing the instantaneous trip signal for
the close-in three-phase fault, this enables the Quad element to issue a trip signal with a
delayed time together using the memory action.
X
lagging
o
Figure 2.1-9 Directional element
= √3 × ( ���� − �� ) ∠ − 90° + ��
���� 0
= √3 × ( ���� − �� ) + ��
�� 0
- 34 -
I
θ
Directional element
����
∠90°
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6F2S1915 (0.46)
R
(2.1-29)
(2.1-30)
GRZ200 (Soft 031 & 032)