Toshiba GR 200 Series, Instruction Manual

Page: 342 / 1563

6F2S1915 (0.46)
GRZ200 (Soft 031 & 032)
- 321 -
[
FL_Ka
]
Im( )
: Imaginary part when a value is placed in parentheses
Re( )
: Real part when a value is placed in parentheses
L
: Length of line GH in kilometers or miles, [
FL_line_km
] / [
FL_line_mile
]
• : Symbol of Vector product
Equation (2.23-3) is used generally when the transmission lines are treated as having
lumped constants. The user should consider the influence of the distributed capacitance of the
transmission line. Therefore, when the distance to the fault (GF) is greater than 100km (62
mile), the FL computation introduces another fault distance (
GF = χ"
) using Equation (2.23-4).
χ" = χ − k
2
×
χ
3
3
(2.23-4)
where,
k: Propagation constant is pre-fixed by the manufacturer of the transmission line.
(k=
0.001𝑘𝑚
−1
). (2.66.1.4)
(ii)
Equation for phase-to-phase faults
When the occurrence of a phase-‘b’-to-phase-‘c’ fault is considered, the distance to the fault
(
GF = χ
) is computed using the following equations:
I
bc
= I
b
− I
c
(2.23-5)
V
bc
= V
b
− V
c
(2.23-6)
I
f
′ = I
bc
− (I
Lb
− I
Lc
)
(2.23-7)
χ =
I
m
(V
bc
∙ I
f
") × L
{𝑅𝑒(R
1
∙ I
bc
∙ I
f
") + 𝐼𝑚(X
1
∙ I
bc
∙ I
f
")} × K
bc
(2.23-8)
where,
I
f
’
: Current change before and after fault occurrence
If”: Complex conjugate of If’
Ibc
: Fault current in phase-‘b’-to-phase-‘c’
Vbc
: Fault voltage in phase-‘b’-to-phase-‘c’
ILb, ILc
: Load currents in phase-‘b’ and phase-‘c’ before fault occurrence
Kbc
: Compensation factor for phase-bc in an unbalanced 3-phase line, [
FL_Kbc
]
• : Symbol of Vector product
Equation (2.23-8)
is a general expression used when the transmission lines are treated