ABB Relion 670 Series Applications Manual page 154

Section 8
Current protection
different overcurrent protections is normally enabled by co-ordination between the operate time
of the different protections. To enable optimal co-ordination all overcurrent protections, to be co-
ordinated against each other, should have the same time characteristic. Therefore a wide range of
standardized inverse time characteristics are available for IEC and ANSI.
Table 21:
Curve name
ANSI Extremely Inverse
ANSI Very Inverse
ANSI Normal Inverse
ANSI Moderately Inverse
ANSI/IEEE Definite time
ANSI Long Time Extremely Inverse
ANSI Long Time Very Inverse
ANSI Long Time Inverse
IEC Normal Inverse
IEC Very Inverse
IEC Inverse
IEC Extremely Inverse
IEC Short Time Inverse
IEC Long Time Inverse
IEC Definite Time
User Programmable
ASEA RI
RXIDG or RD (logarithmic)
It is also possible to tailor make the inverse time characteristic.
Normally it is required that EF4PTOC (51N_67N) 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 pickup level for some
time. Therefore, there is a possibility to give a setting of a multiplication factor
residual current pick-up level. This multiplication factor is activated from a binary input signal
MULTPUx 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 pickup 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 (51N_67N) has a possibility of second harmonic
restrain if the level of 2
current.
148
Time characteristics
nd
harmonic current reaches a value above a set percent of the fundamental
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1MRK 511 401-UUS F
INxMult to the
Bay control REC670
Application manual