Application Notes P54x/EN AP/La4
MiCOM P543, P544, P545 & P546
(AP) 6-55
AP
Therefore, settings in secondary values are:
For relays rated to 1 A (HV and MV sides) Is1 = 200 mA and Is2 = 2 A
For relay rated to 5 A (LV side) Is1 = 1 A and Is2 = 10 A
For the current differential high setting (Id High set) the setting must be in excess of the
anticipated inrush current after ratio correction. Assuming that maximum inrush is 12 times
the nominal transformer current, it would be safe to set the relays at 15 times the nominal
current, therefore the setting would be:
Id high set : for HV side = 15 In = 15 A
for MV side = 15 In = 15 A
for LV side = 15 In = 75 A
3.2 Distance protection setting example
3.2.1 Objective
To prot
ect the 100 km double circuit line between Green Valley and Blue River substations
using a MiCOM P54x in distance POR Permissive Overreach mode and to set the relay at
Green Valley substation, shown in Figure 18. It is assumed that mho characteristics will
be
used.
80km60km
100km
21 21
Tiger Bay Green Valley Blue River Rocky Bay
System data
Green Valley - Blue River transmission line
System voltage 230kv
System grounding solid
CT ratio 1200/5
VT ratio 230000/115
Line length 100km
Line impedance
Z1 = 0.089 + J0.476 OHM/km
Z2 = 0.426 + J1.576 OHM/km
Fault levelts
Green V
alley substation busbars maximum 5000MVA, minimum 2000MVA
Blue River substation busbars maximum 3000MVA, minimum 1000MVA
Circuit continous rating = 400MVA
Worst-case power factor of load = 0.85
P1019ENb
P1019ENa
Figure 18 System assumed for worked example
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