Voltage Dependent Time Delay - ABB RES670 Technical Manual

Section 10
Frequency protection
10.1.6.3
304
voltage level causes a short time delay. For the definite time delay, the setting tDelay
sets the time delay.
For the voltage dependent time delay the measured voltage level and the settings
VNom, VMin, Exponent, t_MaxTripDelay and t_MinTripDelay set the time delay
according to figure 105 and equation . The setting TimerMode is used to decide what
type of time delay to apply.
Trip signal issuing requires that the underfrequency condition continues for at least the
user set time delay tDelay. If the PICKUP condition, with respect to the measured
frequency ceases during this user set delay time, and is not fulfilled again within a user
defined reset time, tReset, the PICKUP output is reset, after that the defined reset time
has elapsed. Here it should be noted that after leaving the hysteresis area, the PICKUP
condition must be fulfilled again and it is not sufficient for the signal to only return
back to the hysteresis area.
The total time delay consists of the set value for time delay plus the
minimum operate time of the start function (80-90 ms).
On the RESTORE output of SAPTUF (81) a 100ms pulse is issued, after a time delay
corresponding to the setting of tRestore, when the measured frequency returns to the
level corresponding to the setting RestoreFreq, after an issue of the TRIP output signal.
If tRestore is se to 0.000 s the restore functionality is disabled, and no output will be
given.

Voltage dependent time delay

Since the fundamental frequency in a power system is the same all over the system,
except some deviations during power oscillations, another criterion is needed to decide,
where to take actions, based on low frequency. In many applications the voltage level
is very suitable, and in most cases is load shedding preferable in areas with low
voltage. Therefore, a voltage dependent time delay has been introduced, to make sure
that load shedding, or other actions, take place at the right location. At constant
voltage, V, the voltage dependent time delay is calculated according to equation 61. At
non-constant voltage, the actual time delay is integrated in a similar way as for the
inverse time characteristic for the undervoltage and overvoltage functions.
1MRK 511 408-UUS A
Phasor measurement unit RES670 2.2 ANSI
Technical manual
M13354-19 v5