Functions
6-157SJ62 Manual
C53000-G1140-C121-1
Definition of nomi-
nal rated values
At addresses 935,0$5<23 and ,35,0$5<23, the nominal volt-
age (phase-to-phase) and current (phase) of the protected equipment is entered (e.g.,
motors). These values do not effect pickup settings. They are generally used to show
values in reference to full scale. For example, if a CT ratio of 600/5 is selected and the
full load current of a motor is 550 amps, a value of 550 amps should be entered for
35,0$5<23(5$7,1*&855(17 if monitoring in reference to full load current is de-
sired. 550 amps are now displayed as 100 % in the percentage metering display.
(Subsection 6.1.1).
Ground Impedance
Ratios (only for
fault location)
The ground impedance ratios must be entered to facilitate line fault location. At ad-
dress 5*5/5DWLR, the resistance ratio of the line is entered, and at address
;*;/5DWLR, the reactance ratio of the line is entered. The ground impedance
ratios are calculated separately, and do not correspond to the real and imaginary com-
ponents of Z
0
/Z
1
. Therefore, no complex calculations are necessary. The ground im-
pedance ratios are obtained from conductor data using the following formulas:
Resistance Ratio: Reactance Ratio:
Where
R
0
= Zero sequence resistance of the line
X
0
= Zero sequence reactance of the line
R
1
= Positive sequence resistance of the line
X
1
= Positive sequence reactance of the line
The ground impedance ratios may be calculated using the impedance values for the
entire line or the impedance per mile values associated with the conductor, since the
length of the line is factored out in the formulas above.
Calculation example:
20 kV free line 120 mm
2
with the following data:
R
1
/s = 0.39 Ω/mile
X
1
/s = 0.55 Ω/mile Positive sequence impedance
R
0
/s = 1.42 Ω/mile
X
0
/s = 2.03 Ω/mile Zero sequence impedance
For ground impedance ratios, the following emerge:
These values are set at addresses and respectively.
Reactance Setting
(only for fault loca-
tion)
The reactance setting must be entered if line fault location is desired. The reactance
setting enables the protective relay to report fault location in terms of distance.
R
G
R
L
--------
1
3
---
R
0
R
1
-------1
–
⋅=
X
G
X
L
-------
1
3
---
X
0
X
1
------ 1
–
⋅=
R
G
R
L
--------
1
3
---
R
0
R
1
-------
1
–
⋅
1
3
---
1.42 Ω mile⁄
0.39 Ω mile⁄
--------------------------------
1
–
0.89=⋅==
X
G
X
L
-------
1
3
---
X
0
X
1
------
1–
⋅
1
3
---
2.03 Ω mile⁄
0.55 Ω mile⁄
--------------------------------
1–
0.90=⋅==
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