Toshiba GR-200 Series Instruction Manual page 36

Relay polarity
2.1.1
The user can choose either non-directional OC or directional OC for each OC stage. In addition,
the user can further select either the forward or the reverse direction for each of the directional
OC elements selected.
Characteristic of non-directional OC
(i)
The characteristic of the non-directional type OC is a circle that has a center at the origin. A
setting and a scheme switch is used to configure each non-directional OC element; i.e., the user
can set the threshold value of the non-directional OC element for stage 1 using setting [OC1],
provided time characteristic is required for define time delay (DT) described in Chapter
2.1.2(ii). Nondir should be set for the scheme switch [OC1-Dir].
Characteristic of directional-OC element in the forward direction
(ii)
As shown in Figure 2.1-1, the characteristic of the directional-OC elements in the forward
direction is a semi-circle based upon the borderline; the hatched area shows the operating
region of a directional-OC element.
I
Forward
Operation zone
Figure 2.1-1 Characteristic of the directional-OC element in the forward direction
Note: Directional characteristic angle (θ) forms the angle between the reference
1
quantity and the directional characteristic angle line. The half plane represents
the zone of operation bordered on one side by the borderline and extending in the
direction that contains both the reference (polarizing) and operating quantities.
Note: For the polarizing voltage (Vpol), greater than 1.0 voltage should be applied for
2
sensing.
A reference signal, that is, a polarization signal is required by the directional OC element,
the reference signal is derived from a phase-to-phase voltage: for example, the directional OC
element for phase-A (OC-A) uses the phase-B-to-phase-C voltage rotated by 90° (V
the leading direction, this reference signal is illustrated in Figure 2.1-2. The direction of the
Reverse
Operation zone
Polarizing voltage (Vpol)
2
-θ
1
Directional characteristic
angle line
- 17 -
Forward
Operation zone
I
+θ
6F2T0200 (0.15)
Directional characteristic
angle line
1
Polarizing voltage (Vpol)
2
Reverse
Operation zone
90°) in
BC
GRE200 (1,2)