Toshiba GRZ100-211B, Instruction Manual

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6 F 2 S 0 8 3 4
Figure 2.8.4.2 Three-terminal Model
χ
A = (VA
−
VB + ZA(IB + IC) + ZBIB ) / ZAId (5)
χ
JB = (VA
−
VB + ZBIB
−
ZAIA) / ZBId (6)
χ
JC = (VA
−
VC + ZCIC
−
ZAIA) / ZCId (7)
where,
Id = IA + IB + IC
VC = voltage at terminal C
IC = current at terminal C
χ
A = distance from terminal A to fault point as a ratio to line length from terminal A to
junction
χ
JB ,
χ
JC = distance from junction to fault point as a ratio to line length from junction to
terminal B or C
ZA ,ZB ,ZC = impedance from each terminal to junction
Firstly,
χ
A is calculated using Equation (5) assuming that the fault is between terminal A and the
junction. If the result does not match the input line data, then
χ
JB is calculated using Equation (6)
assuming that the fault is between the junction and terminal B. If the result does not match the
input line data, the calculation is repeated using Equation (7) assuming that the fault is between the
junction and terminal C.
Calculation Method
In the calculation, the sequence quantities of voltages and currents are employed instead of the
phase quantities. Thus, equation (4) is combined with Equation (8) to give:
χ
=
V V Z I Z I Z I
Z I
d
Z I
d
Z I
d
A B B B B 1 1 11 1 12 2 10 0
11 1 12 2 10 0
− + + +
+ +
( )
(8)
where,
VA1 = positive sequence voltage at terminal A
VB1 = positive sequence voltage at terminal B
IB1, IB2 and IB0 = positive, negative and zero sequence current at terminal B
Id1,Id2 and Id0 = positive, negative and zero sequence differential current
Z11, Z12 and Z10 are expressed by the following equations assuming that Zab = Zba, Zbc = Zcb
and Zca = Zac:
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