ABB Relion 670 series, Technical Reference Manual

Page: 543 / 1232

five equal subintervals, with six delays. (settings t1 , t2 , t3 , t4 , t5 and t6 ) as shown in
figure 274 . These times should be set so that t1 => t2 => t3 => t4 => t5 => t6.
0
E
maxcont
M
max
- E
maxcont
M
max
t_MinTripDelay
t_MaxTripDelay
delay in s
Overexcitation M-E
maxcont
Excitation M
under-
excitation
99001068_ansi.vsd
ANSI99001068 V1 EN
Figure 274: An example of a Tailor-Made delay characteristic
Delays between two consecutive points, for example t3 and t4, are obtained by linear
interpolation.
Should it happen that t_MaxTripDelay be lower than, for example, delays t1, and t2,
the actual delay would be t_MaxTripDelay . Above Mmax, the delay can only be
t_MinTripDelay .
8.4.2.3 Cooling
Overexcitation protection OEXPVPH (24) is basically a thermal protection; therefore a
cooling process has been introduced. Exponential cooling process is applied. Parameter
Setting tool is an OEXPVPH (24) setting, with a default time constant
t_CoolingK of
20 minutes. This means that if the voltage and frequency return to their previous
normal values (no more overexcitation), the normal temperature is assumed to be
reached not before approximately 5 times
t_CoolingK minutes. If an overexcitation
condition would return before that, the time to trip will be shorter than it would be
otherwise.
8.4.2.4 Overexcitation protection function measurands
A monitored data value, TMTOTRIP, is available on the local HMI and in PCM600.
This value is an estimation of the remaining time to trip (in seconds), if the
overexcitation remained on the level it had when the estimation was done. This
information can be useful during small or moderate overexcitations.
If the overexcitation is so low that the valid delay is t_MaxTripDelay , then the
estimation of the remaining time to trip is done against t_MaxTripDelay .
1MRK505222-UUS C
Section 8
Voltage protection
537
Technical reference manual