ABB REG650 Technical Manual page 284

Section 9
Voltage protection
278
be allowed. In case the inverse delay is longer than 1800 seconds, OEXPVPH (24) trips
t_MaxTripDelay, see figure 126.
A definite minimum time, t_MinTripDelay, can be used to limit the operate time at
high degrees of overexcitation for Pickup1. In case the inverse delay is shorter than
t_MinTripDelay, OEXPVPH (24) function trips after t_MinTripDelay seconds.
Time (s)
1000
100
10
1
1 2 3
ANSI01000373 V1 EN
Figure 127: Delays inversely proportional to the square of the overexcitation
The critical value of excitation M is determined via OEXPVPH (24) setting Pickup2.
Pickup2 can be thought of as a no-load voltage at rated frequency, where the inverse
law should be replaced by a short definite delay, t_MinTripDelay. If, for example,
Pickup2 = 140 %, then M is according to equation 88.
IEEE OVEREXCITATION CURVES
4 5 10
OVEREXCITATION IN %
1MRK 502 043-UUS B
TD = 60
TD = 20
TD = 10
TD = 9
TD = 8
TD = 7
TD = 6
TD = 5
TD = 4
TD = 3
TD = 2
TD = 1
20 30 40
(M-Emaxcont)*100)
en01000373_ansi.vsd
Technical Manual