6.6.3 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 four step residual overcurrent protection, zero or negative
sequence direction EF4PTOC are set via the local HMI or PCM600.
The following settings can be done for the four step residual overcurrent protection.
GlobalBaseSel: Selects the global base value group used by the function to define
(IBase), (UBase) and (SBase).
SeqTypeUPol: It is used to select type of voltage polarization quantity, i.e. ZeroSeq
and NegSeq for direction detection.
SeqTypeIPol: It is used to select type of current polarization quantity, i.e. ZeroSeq and
NegSeq for direction detection.
SeqTypeIDir: It is used to select type of operating quantity, i.e. ZeroSeq and NegSeq
for direction detection.
Operation: Sets the protection to On or Off.
EnaDir: Enables the directional calculation in addition to the directional mode
selection in each step.
6.6.3.1 Settings for steps 1 and 4
n means step 1 and 4. x means step 1, 2, 3 and 4.
DirModex: The directional mode of step x. Possible settings are Off/Non-directional/
Forward/Reverse.
Characteristn: Selection of time characteristic for step n. Definite time delay and
different types of inverse time characteristics are available.
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 have
to be a minimum time difference Dt between the time delays of two protections. The
minimum time difference can be determined for different cases. To determine the
Section 6 1MRK 505 291-UEN A
Current protection
118
Application manual
To Next Page
Loading...
