ABB Relion 670 series, Technical Manual

Page: 651 / 1432

The upper V/Hz limit for the Tailor-Made characteristic is always the greater value among the
following two values in %:
• 1.10 x
Pickup1
•
Pickup2
The reason is to prevent the loss of accuracy of the Tailor-Made characteristic when small set value
for
Pickup2 is used.
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-US
Figure 349: 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.
9.4.7.3 Cooling
M5854-92 v6
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.
9.4.7.4 Overexcitation protection function measurands
M5854-95 v7
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
overexcitation situations.
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.
The relative excitation M, shown on the local HMI and in PCM600 has a monitored data value
VPERHZ and is calculated from the expression:
1MRK 502 066-UUS B Section 9
Voltage protection
645
Technical manual