ABB REG670 Applications Manual page 415

1MRK 502 071-UEN -
Generator protection REG670 2.2 IEC and Injection equipment REX060, REX061, REX062
Application manual
When ConnType is set to PhN DFT or PhN RMS then the IED automatically divides
set value for UBase by √3. When ConnType is set to PhPh DFT or PhPh RMS then set
value for UBase is used. Therefore, always set UBase as rated primary phase-to-phase
voltage of the protected object. If phase to neutral (PhN) measurement is selected as
setting, the operation of phase-to-earth over voltage is automatically divided by sqrt3.
This means operation for phase-to-earth voltage over:
> ×
U (%) UBase kV ( ) / 3
and operation for phase-to-phase voltage over:
> ×
U (%) UBase(kV)
EQUATION1993 V1 EN
The below described setting parameters are identical for the two steps (n = 1 or 2).
Therefore the setting parameters are described only once.
Characteristicn: This parameter gives the type of time delay to be used. The setting
can be Definite time, Inverse Curve A, Inverse Curve B, Inverse Curve C or I/Prog. inv.
curve. The choice is highly dependent of the protection application.
OpModen: This parameter describes how many of the three measured voltages that
should be above the set level to give operation. The setting can be 1 out of 3, 2 out of 3,
3 out of 3. In most applications it is sufficient that one phase voltage is high to give
operation. If the function shall be insensitive for single phase-to-earth faults 1 out of 3
can be chosen, because the voltage will normally rise in the non-faulted phases at
single phase-to-earth faults. In subtransmission and transmission networks the UV
function is mainly a system supervision function and 3 out of 3 is selected.
Un>: Set operate overvoltage operation value for step n, given as % of UBase. The
setting is highly dependent of the protection application. Here it is essential to
consider the maximum voltage at non-faulted situations. Normally this voltage is less
than 110% of nominal voltage.
tn: time delay of step n, given in s. The setting is highly dependent of the protection
application. In many applications the protection function is used to prevent damages
to the protected object. The speed might be important for example in case of protection
of transformer that might be overexcited. The time delay must be co-ordinated with
other automated actions in the system.
tResetn: Reset time for step n if definite time delay is used, given in s. The default
value is 25 ms.
tnMin: Minimum operation time for inverse time characteristic for step n, given in s.
For very high voltages the overvoltage function, using inverse time characteristic, can
give very short operation time. This might lead to unselective trip. By setting t1Min
longer than the operation time for other protections such unselective tripping can be
avoided.
Section 10
Voltage protection
(Equation 242)
409