Siemens siprotec 7SA522, Руководство пользователя

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Functions
6-18
7SA522 Manual
C53000-G1176-C119-2
The per unit length reactance X’ is entered as relative quantity
[
, in address in
Ω
/km, when for example the unit of length is given in
NP
(Address , refer to Sec-
tion 6.1.1 under “
8QLWVRI/HQJWK
” or under address in
Ω
/mile, when the unit
of length is given in
0LOHV
. The corresponding line length is entered in address
/LQH/HQJWK
in kilometres or under address
/LQH/HQJWK
in miles. If the unit
of length in address 0236 is changed after the per unit length impedances in address
1110 or 1112 or the line length in address 1111 or 1113 have been entered, the line
data must be entered again for the revised unit of length.
When entering the parameters with a personal computer and DIGSI
®
4 the values
may optionally also be entered as primary values. The following conversion to second-
ary quantities is then not required.
For the conversion from primary to secondary values the following applies in general:
Correspondingly the following applies to the per unit length reactance of a line:
with
N
CT
— Ratio of the current transformers
N
VT
— Ratio of the voltage transformers
Calculation example:
110 kV overhead line 150 mm
2
similar to above
R'
1
= 0.19
Ω
/km
X'
1
= 0.42
Ω
/km
Current transformer 600 A/1 A
Voltage transformer 110 kV/0.1 kV
The secondary per unit length reactance is therefore:
In address the following is set
[
=
Ω
/km.
Earth Impedance
(Residual)
Compensation Matching of the earth to line impedance is an essential prerequisite for the accurate
measurement of the fault distance (distance protection, fault locator) during earth
faults. This compensation is either achieved by entering the resistance ratio R
E
/R
L
and the reactance ratio X
E
/X
L
or by entry of the complex earth (residual) compensa-
tion factor K
0
. Which of these two entry options applies was determined by the setting
in address (refer to Section 6.1.1). Corresponding to the option determined
there, only the relevant addresses appear here.
Z
sec
Ratio of current transformers
Ratio of voltage transformers
----------------------------------------------------------------------------------- Z
prim
⋅
=
X’
s ek
N
CT
N
VT
----------- X’
prim
⋅
=
X’
sec
N
CT
N
VT
---------- X’
prim
⋅
600 A/1 A
110 kV/0.1 kV
--------------------------------------- 0.42
Ω
/km
⋅
0.229
Ω
/km = = =