ABB REB650, Руководство по применению, Страница: 110 / 322

It is also possible to tailor make the inverse time characteristic.
Normally it is required that EF4PTOC 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
operating level for some time. Therefore, there is a possibility to give a setting of a
multiplication factor
INxMult to the residual current pick-up level. This
multiplication factor is activated from a binary input signal ENMULTx to the
function.
Power transformers can have a large inrush current, when being energized. This
inrush current can produce residual current component. The phenomenon is due to
saturation of the transformer magnetic core during parts of the cycle. There is a risk
that inrush current will give a residual current that reaches level above the
operating current of the residual overcurrent protection. The inrush current has a
large second harmonic content. This can be used to avoid unwanted operation of
the protection. Therefore, EF4PTOC has a possibility of second harmonic restrain
if the level of 2
nd
harmonic current reaches a value above a set percent of the
fundamental current.
7.2.3 Setting guidelines
IP14988-1 v1
M15282-3 v12
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 four step residual overcurrent protection are set via the local
HMI or PCM600. The following settings can be done for the function.
Common base IED values for the primary current ( IBase ), primary voltage ( UBase )
and primary power ( SBase ) are set in global base values for settings function
GBASVAL.
GlobalBaseSel : Selects the global base value group used by the function to define
IBase , UBase and SBase as applicable.
SeqTypeUPol : This is used to select the type of voltage polarising quantity i.e. Zero
seq or Neg seq for direction detection.
SeqTypeIPol : This is used to select the type of current polarising quantity i.e. Zero
seq or Neg seq for direction detection.
Section 7
1MRK 505 388-UEN B
Current protection
104 Busbar protection REB650 2.2 IEC
Application manual