Toshiba GR 200 Series, Instruction Manual

Page: 268 / 1563

6F2S1915 (0.46)
GRZ200 (Soft 031 & 032)
- 247 -
2.13.1
Drop-off and pickup setting
Figure 2.13-1 shows the characteristic of the OVS element. The outer circle shows the
threshold of pick-up threshold voltage (PU), whereas the inner circle shows drop-off voltage
point (DO). The hatched area shows the operation area of the OVS.
V
V
Pickup
0
Dropoff
Figure 2.13-1 Characteristic of OVS element
For example, with regard to the OVS1 element, suppose the user sets a pick-up value in
P.U for setting [
OVS1
]. Then the user should set a drop-off value using setting [
OVS1-DPR
],
which configures the ratio of the PU to the DO.
2.13.2
Delay for the operation of the OVS element
The OVS element has a delay timer for the operation. For the OVS1 element, the user can set
a delay time using setting [
TOVS1
]. The user can find the delay timer in the OVS function
logic. (See section 2.13.5)
2.13.3
Time characteristic
The OVS element has two characteristics between a voltage condition and an operation time;
hence, the user should select a mode either (i) definite (independent) time characteristic delay
or (ii) inverse (dependent) time characteristic delay. For the definite time characteristic delay,
the operation time is a constant. In the inverse time characteristic delay, the operation time
depends upon the level of the voltage condition.
(i)
Definite time characteristic (DT)
To operate the definite (independent) time delay, set
DT
for scheme switch [
OVS1-Timer
].
Resetting the OVS element is performed when a voltage falls below the drop-off voltage.
(ii)
Invers time characteristic (IDMT)
To operate the dependent (invers) time delay, set
IDMT
for scheme switch [
OVS1-Timer
].
Operation feature
The operate time of the inverse (dependent) time characteristic is inversely proportional to the
level of the voltage condition. Figure 2.13-2 shows the invers time characteristic of the OVS
element when a multiplier setting is used. The OVS element uses Equation (2.13-1) to be in