P54x/EN OP/La4 Operation
(OP) 5-26
MiCOM P543, P544, P545 & P546
OP
The minimum operating current is therefore a function of the s1 and k1 settings. With k1 set
to 30% and Is1 set to 0.2 pu, the minimum operating current will be:
min
= 1.176 s1
min
= 0.235 pu
1.2 Disabling/enabling differential protection
The diffe
rential function can be globally enabled or disabled using the CONFIGURATION
/Phase Diff/Enabled-Disabled setting.
If the differential function is disabled globally (i.e. CONFIGURATION column), no current
differential message is transmitted and no current differential measurements (Measurements
3) and channel communication statistics (Measurements 4) are displayed. Therefore a
remote connected relay, will display a signaling fail and C Diff failure alarm.
If the differential function is enabled globally (i.e. CONFIGURATION column) and disabled
within a group (i.e. group x column), current differential message is exchanged, current
differential measurements (Measurements 3) and channel communication statistics
(Measurements 4) are displayed, local current differential protection cannot trip but relay can
receive a differential inter-trip from the remote end.
1.3 Differential relay compatibility
with previous versions
Current differential protection in P54x relays is as follows:
P543 - P546 models suffix K are compatible with each other
In non GPS mode P543 - P546 models suffix K are compatible with relay models
P543 - P546 suffix B,G and J
In GPS mode P543 - P546 models suffix K are compatible with relay models
P545 - P546 suffix B,G and J
P543 - P546 models suffix K are not compatible with suffix A models
If a relay suffix K is communicating with a relay suffix B,G or J, a monitor bit labeled
H/W B to J model in Measurement 4/Channel status will become 1
Differential current transformer supervision (Differential CTS) in P543 - P546 models suffix K
are only compatible with P543 - P546 models suffix K.
1.4 Differential relay without voltage connections
Differential p
rotection does not need phase or neutral voltage connections as this protection
relies entirely on the currents measured at each end of the line.
If there are no voltage connections to the P54x relay, the VTs Connected Yes/No setting
under CT AND VT RATIOS should be set to No. Once set to No, this will cause the relay
VTS logic to set the VTS Slow Block and VTS Fast Block DDBs, but it will not raise any
alarms. It will also override the VTS enabled setting should the user set it. The purpose of
this is to stop the pole dead logic working incorrectly in the absence of voltage and current
inputs.
1.5 Line parameters settings
1.5.1 Phase rotation (phase sequence)
A setting i
s used to select whether the 3 phase voltage set is rotating in the standard ABC
sequence, or whether the rotation is in reverse ACB order. The appropriate selection is
required to ensure that all sequence components and faulted phase flagging/targeting is
correct.
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