Areva MiCOM P441, Technical Manual

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Application Notes P44x/EN AP/E33
MiCOM P441/P442 & P444 Page 119/220
4.4.4 Check Synchronism Settings
Depending on the particular system arrangement, the main three phase VT for the relay may
be located on either the busbar or the line. Hence, the relay needs to be programmed with
the location of the main voltage transformer. This is done under the ‘CT & VT RATIOS’
column in the ‘Main VT Location’ cell, which should be programmed as either ‘Line’ or ‘Bus’
to allow the previously described logic to operate correctly. (See DDB description bellow)
Note that the check synch VT input may be driven from either a phase to phase or phase to
neutral voltage. The ‘C/S Input’ cell in the ‘CT & VT RATIOS’ column has the options of A-N,
B-N, C-N, A-B, B-C or C-A, which should therefore be set according to the actual VT
arrangement.
If the VTS feature internal to the relay operates, the check synchronising element is inhibited
from giving an ‘Allow Reclosure’ output. This avoids allowing reclosure in instances where
voltage checks are selected and a VT fuse failure has made voltage checks unreliable.
Measurements of the magnitude angle and delta frequency (slip frequency - since version
A4.0 with model 07) – the rated frequency of network is displayed by default in case of
problem with the delta f calculation : No line voltage or no bus voltage or both of the check-
synch voltage are displayed in the ‘MEASUREMENTS 1’ column.
Individual System Check logic features can be enabled or disabled by means of the C/S
Check Scheme function links. Setting the relevant bit to 1 will enable the logic, setting bits
to 0 will disable that part of the logic. Voltage, frequency, angle and timer thresholds are
shared for both manual and autoreclosure, it is the live/dead line/bus logic which can differ.