Specifications

Overcurrent Protection SIPROTEC 7SJ80
4/12 SIPROTEC Compact · SIEMENS SIP 3.01 · Edition 3
Application examples
Radial systems
General hints:
The relay at the far end (D) from the
infeed has the shortest tripping time.
Relays further upstream have to be
time-graded against downstream
relays in steps of about 0.3 s.
Earth-fault detection in isolated or
compensated systems
In isolated or compensated systems,
an occurred earth fault can be easily
found by means of sensitive directio-
nal earth-fault detection.
Fig. 4/9 Protection concept with time-overcurrent protection
Infeed
Transformer protection
Busbar
51 51N 46 79
2) 1)
Busbar
Load
51 51N 46
Busbar
Load
51 51N 46
Load
D
C
B
A
AR
Further power supply
I>t
IN>t I2>t
I>t
IN>t I2>t
I>t
IN>t
I2>t
*
*
52
52
52
52
Busbar
IN>t dir.
Load
Infeed
50 51
67Ns
I>> I>t
7XR96
1)
60/1
52
Fig. 4/10 Protection concept for directional earth-fault detection
4_9_LSA4839-en.pdf
4_10_LSA4840a-en.pdf
1) Auto-reclosure
(ANSI 79) only with
overhead lines
2) Unbalanced load
protection (ANSI 46)
as backup protection
against asymmetrical
faults
1) The sensitive current
measurement of the
earth current should
be made by a zero-
sequence current
transformer
1
2
3
4
5
6
7
8
9
10