1 10
1
10
100
1000
2 403 4 5 20 30
TD = 2
TD = 3
TD = 4
TD = 5
TD = 6
TD = 7
TD = 8
TD = 9
TD = 10
TD = 1
OVEREXCITATION IN %
Time (s)
IEEE OVEREXCITATION CURVES
en01000373_ansi.vsd
(M-Emaxcont)*100)
TD = 60
TD = 20
ANSI01000373 V1 EN-US
Figure 348: Delays inversely proportional to the square of the overexcitation
The critical value of excitation M is determined indirectly 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 195.
( )
Pickup2 f
M 1.40
Vn/fn
= =
ANSIEQUATION2286 V1 EN-US (Equation 195)
The Tailor-Made law allows a user to design an arbitrary delay characteristic. In this case the
interval between M =
Pickup1
, and M = Mmax is automatically divided into five equal subintervals,
with six delays. (settings
t1
,
t2
,
t3
,
t4
,
t5
and
t6
) as shown in figure 349. These times should be set
so that t1 => t2 => t3 => t4 => t5 => t6.
The lower V/Hz limit is always the set value
Pickup1
in %.
Section 9 1MRK 502 066-UUS B
Voltage protection
644
Technical manual
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