ABB RELION 670 Series Applications Manual page 170

Section 7
Current protection
Inverse time characteristic enables fast fault clearance of high current faults at the same time as
selectivity to other inverse time phase overcurrent protections can be assured. This is mainly used
in radial fed networks but can also be used in meshed networks. In meshed networks, the settings
must be based on network fault calculations.
To assure selectivity between different protections, in the radial network, there has to be a
minimum time difference Dt between the time delays of two protections. To determine the
shortest possible time difference, the operation time of protections, breaker opening time and
protection resetting time must be known. These time delays can vary significantly between
different protective equipment. The following time delays can be estimated:
Protection trip time:
Protection resetting time:
Breaker opening time:
The different characteristics are described in the technical reference manual.
tx : Definite time delay for step x . The definite time tx is added to the inverse time when inverse
time characteristic is selected. Note that the value set is the time between activation of the start
and the trip outputs.
Pickup"x" : Operate residual current level for step x given in % of IB .
INx>MaxEd2Set and INx>MinEd2Set should only be changed if remote setting of operation current
INx> , is used. The limits are used for decreasing the used range of the INx> setting. If INx> is
level,
set outside
function. If
kx : Time multiplier for the dependent (inverse) characteristic for step x .
IMinx : Minimum pickup current for step x in % of IB . Set IMinx below Pickupx for every step to
achieve ANSI reset characteristic according to standard. If
will reset at current equals to zero.
txMin : Minimum operating time for inverse time characteristics. At high currents, the inverse time
characteristic might give a very short operation time. By setting this parameter, the operation
time of the step can never be shorter than the setting.
164
15-60 ms
15-60 ms
20-120 ms
INx>MaxEd2Set and INx>MinEd2Set , the closest of the limits to INx> is used by the
INx>MaxEd2Set is smaller than INx>MinEd2Set , the limits are swapped.
IMinx is set above for any step, signal
1MRK 505 337-UUS A
Application manual