Siemens siprotec 7SA6 User Manual

Functions
6-50 7SA6 Manual
C53000-G1176-C133-1
gization is activated for all recognized faults in any zone (i.e. with general fault detec-
tion of the distance protection).
Load Area
(only for
Impedance Pick-up)
On long heavily loaded lines, the risk of encroachment of the load impedance into the
tripping characteristic of the distance protection may exist. To exclude the risk of
unwanted fault detection by the distance protection during heavy load flow, a load
trapezoid characteristic may be set for tripping characteristics with a large R-reach,
which excludes such unwanted fault detection by overload. This load area is
considered in the description of the tripping characteristics (refer to Figure 6-29,
Subsubsection 6.2.4.1).
The R–values 5ORDG( (address ) and 5ORDG (address )
must be set somewhat (approx. 10 %) smaller than the minimum load impedance
which may occur. The minimum load impedance results when the maximum load
current and minimum operating voltage exist.
Calculation example:
110 kV overhead line 150 mm
2
with the following data:
maximum transferrable load
P
max
= 100 MVA corresponding to
I
max
=525A
minimum operating voltage
U
min
=0.9U
N
current transformers600 A/5 A
voltage transformers110 kV/0.1 kV
The resulting minimum load impedance is therefore:
When applying the settings with a personal computer and DIGSI
®
4 these values may
be entered as primary values. The conversion to secondary values is
when applying a security margin of 10 % the following is set:
primary: 5ORDG( =  Ω or
secondary: 5ORDG( =  Ω.
The spread angle of the load trapezoid
ϕORDG((address ) and ϕ load (Ø-
Ø) (address ) must be greater (approx. 5°) than the maximum arising load angle
(corresponding to the minimum power factor cos ϕ).
Calculation example:
minimum power factor
cos ϕ
min
=0.63
ϕ
max
= 51°
Setting
j load (Ø-E) = ϕ
max
+5° = °.
R
Load prim
U
min
3 I
L max
⋅
-------------------------
0.9 110 kV ⋅
3 525 A ⋅
--------------------------
108.87 Ω== =
R
Load sec
N
CT
N
VT
----------
R
Load prim
⋅
600 A/5 A
110kV/0.1kV
--------------------------------------
108.87 Ω⋅ 11.88 Ω
== =

Siemens siprotec 7SA6 Specifications

General

Brand	Siemens
Model	siprotec 7SA6
Category	Relays
Language	English