Setting Guidelines - ABB REG670 Applications Manual

1MRK 502 071-UEN -
9.2.3
Generator protection REG670 2.2 IEC and Injection equipment REX060, REX061, REX062
Application manual
standardized inverse time characteristics are available for IEC and ANSI. It is also
possible to tailor make the inverse time characteristic.
Normally, it is required that the phase overcurrent protection shall reset as fast as
possible when the current level gets lower than the operation level. In some cases
some sort of delayed reset is required. Therefore, different kinds of reset
characteristics can be used.
For some protection applications, there can be a need to change the current pick-up
level for some time. A typical case is when the protection will measure the current to
a large motor. At the start up sequence of a motor the start current can be significantly
larger than the rated current of the motor. Therefore, there is a possibility to give a
setting of a multiplication factor to the current pick-up level. This multiplication factor
is activated from a binary input signal to the function.
Power transformers can have a large inrush current, when being energized. This
phenomenon is due to saturation of the transformer magnetic core during parts of the
period. There is a risk that inrush current will reach levels above the pick-up current
of the phase overcurrent protection. The inrush current has a large 2
content. This can be used to avoid unwanted operation of the protection function.
Therefore, OC4PTOC has a possibility of 2
harmonic current reaches a value above a set percent of the fundamental current.
The phase overcurrent protection is often used as a protection for two and three phase
short circuits. In some cases, it is not wanted to detect single-phase earth faults by the
phase overcurrent protection. This fault type is detected and cleared after operation of
earth fault protection. Therefore, it is possible to make a choice how many phases, at
minimum, that have to have current above the pick-up level, to enable operation. If set
1 of 3 it is sufficient to have high current in one phase only. If set 2 of 3 or 3 of 3 single-
phase earth faults are not detected.

Setting guidelines

When inverse time overcurrent characteristic is selected, the operate
time of the stage will be the sum of the inverse time delay and the set
definite time delay. Thus, if only the inverse time delay is required, it
is important to set the definite time delay for that stage to zero.
The parameters for the directional phase overcurrent protection, four steps OC4PTOC
are set via the local HMI or PCM600.
The following settings can be done for OC4PTOC.
Common base IED values for primary current (IBase), primary voltage (UBase) and
primary power (SBase) are set in the global base values for settings function
GBASVAL.
GlobalBaseSel: This is used to select GBASVAL function for reference of base
values.
Current protection
nd
harmonic restrain if the level of 2
Section 9
nd
harmonic
nd
325