Functions
6-62
7SA522 Manual
C53000-G1176-C119-2
Accordingly, the reach for any distance zone can be specified as follows:
where
N
CT
— transformation ratio of the current transformers
N
VT
— transformation ratio of the voltage transformers
On long, heavily loaded lines, the MHO circle may extend into the load impedance
range. This is of no consequence as the pick-up by overload is prevented by the load
trapezoid. Refer to margin heading “Load Area” in Sub-section 6.2.2.2.
Calculation example:
110 kV overhead line150 mm
2
with the following data:
s (length) = 21 miles
R
1
/s =
0.31
Ω
/mile
X
1
/s =
0.69
Ω
/mile
R
0
/s
=
0.87
Ω
/mile
X
0
/s =
1.96
Ω
/mile
current transformers600 A/5 A
voltage transformers110 kV/0,1 kV
The following line data is calculated:
R
L
= 0.31
Ω
/mile · 21 miles = 6.51
Ω
X
L
= 0.69
Ω
/mile · 21 miles = 14.49
Ω
Z
L
=
√
6.51
2
+ 14.49
2
Ω
=15.88
Ω
For the first zone, a setting of 85 % of the line length should be applied, which results
in
primary:
Z1
prim
= 0.85 · Z
L
= 0.85 · 15.88
Ω
= 13.5
Ω
or secondary:
Independent Zones
Z1 up to Z5
By means of the setting parameter
02'(
each zone can be set
)RUZDUG
or
5HYHUVH
(Address
,
). This allows any combination of forward or reverse
graded zones. Zones that are not required, are set
,QDFWLYH
.
The values derived from the grading coordination chart are set for each of the required
zones. The setting parameters are grouped for each zone. For the first zone, Z1, these
are the parameters
(address
) specifying the impedance of the upper
zenith of the MHO circle from the origin (reach), as well as the relevant delay time set-
tings.
Different delay times can be set for single- and multiple-phase faults in the first zone:
(address
) and
(address
). The first zone
is typically set to operate without additional time delay.
Z
sec
N
CT
N
VT
-----------
Z
prim
⋅
=
Z1
sec
N
CT
N
VT
----------
Z
prim
⋅
600 A/5 A
110 kV/0.1 kV
--------------------------------------
13.5
Ω
⋅
1.47
Ω
=
=
=
Summary of Contents for siprotec 7SA522
Page 20: ...7SA522 Manual C53000 G1176 C119 2 ...
Page 64: ...7SA522 Manual C53000 G1176 C119 2 ...
Page 89: ...SIPROTEC 4 Devices 4 25 7SA522 Manual C53000 G1176 C119 2 Figure 4 20 CFC Logic example ...
Page 408: ...7SA522 Manual C53000 G1176 C119 2 ...
Page 456: ...7SA522 Manual C53000 G1176 C119 2 ...
Page 516: ...7SA522 Manual C53000 G1176 C119 2 ...
Page 620: ...Appendix B 48 ...
