t
TD
V Vpickup
Vpickup
=
⋅
⋅
− >
>
−
+
480
32 0 5
0 035
.
.
ANSIEQUATION2288 V2 EN (Equation 36)
The details of the different inverse time characteristics are shown in section "Inverse
time characteristics".
TRIP signal issuing requires that the residual overvoltage condition continues for at
least the user set time delay. This time delay is set by the parameter t1 and t2 for
definite time mode (DT) and by some special voltage level dependent time curves for
the inverse time mode (TOV).
If the PICKUP condition, with respect to the measured voltage ceases during the delay
time, the corresponding PICKUP output is reset.
8.3.7.3 Blocking
It is possible to block two step residual overvoltage protection (ROV2PTOV, 59N)
partially or completely, by binary input signals where:
BLOCK:
blocks all outputs
BLK1: blocks all pickupand trip outputs related to step 1
BLK2: blocks all pickup and trip inputs related to step 2
8.3.7.4 Design
The voltage measuring elements continuously measure the residual voltage. Recursive
Fourier filters filter the input voltage signal. The single input voltage is compared to
the set value, and is also used for the inverse time characteristic integration. The design
of Two step residual overvoltage protection (ROV2PTOV, 59N) is schematically
described in
Figure 56.
1MRK 505 277-UUS C Section 8
Voltage protection
141
Technical Manual
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