ABB REL650 series Technical Manual page 179

1MRK 506 335-UUS A
Technical manual
The voltage and current discrimination part gives phase segregated pickup signals if the
respective measured phase voltage is below the setting parameter PU27PN at the same
time as the zero sequence voltage is above the setting parameter 3V0Pickup. If there is a
pickup in any phase the PICKUP output signal will be activated.
The internal signal for detection of cross-country fault, DetectCrossCountry, that come
from the voltage and current discrimination part of the function can be achieved in three
different ways:
1. The magnitude of 3I
longer than the setting of pick-up timer tIN.
2. The magnitude of 3I
as the magnitude of 3V
time longer than the setting of pick-up timer tVN.
3. The magnitude of 3I
as one of the following conditions are fulfilled:
• the measured phase-to-phase voltage in at least one of the phase combinations
has been below the setting parameter PU27PP for more than 20 ms.
• At least two of the phase voltages are below the setting parameter PU27PN for
more than 20 ms.
The second part, phase preference evaluation, uses the internal signal
DetectCrossCountry from the voltage and current evaluation together with the input
signal PHSEL together with phase selection pickup condition (from phase selection
functions) connected to input PHSEL, and the information from the setting parameter
OperMode are used to determine the condition for trip. To release the Phase preference
logic, at least two out of three phases must be faulty. The fault classification whether it is
a single phase-to-ground, two-phase or cross-country fault and which phase to be tripped
at cross-country fault is converted into a binary coded signal and sent to the distance
protection measuring zone to release the correct measuring zone according to the setting
of OperMode. This is done by activating the output ZREL and it shall be connected to the
input PHSEL on the distance zone measuring element.
The code built up for release of the measuring fault loops is as follows: PHSEL = AN*1
+ BN*2 + CN*4 + AB*8 + AC*16 + CA*32. Example: if only AN start is chosen the value
is 1, if start AN and CN are choosen, the value is 1+4=5.
The input signals RELxxx are additional fault release signals that can be connected to
external protection functions through binary input.
has been above the setting parameter Pickup_N for a time
0
has been above the setting parameter Pickup_N at the same time
0
has been above the setting parameter 3V0Pickup during a
0
has been above the setting parameter Pickup_N at the same time
0
Section 6
Impedance protection
173