Specifications

Generator and Motor Protection SIPROTEC 7SK81
7/15SIPROTEC Compact · SIEMENS SIP 3.01 · Edition 3
Fig. 7/18 Typical protection concept for an asynchronous high-voltage motor
Busbar
I>, I>>,
I>>>
50 49 46 37
14
49
86 Motor restart inhibit
47 27 59 59N
51M
51N
67N
Rotation V< V>
46-1 PU I<
Motor starting protection
M
IN>
Blocked rotor
Tachometer
or
V0>
ILoad>
S>
IN>>
52
Visio-LSA220ba-us.pdf
Fig. 7/17 Line feeder with load shedding
Busbar
I>, I>>,
I>>>
50 50N 51 51N
49 46 86
Final trip
27 81U
V<
f<
>
I2>
I>, Ip
IN>>
IN>,
INTOC
52
Visio-LSA4876a-us.pdf
for Low-Power CT and VT Applications - Application examples
Line feeder with load shedding
In unstable power systems (e.g. solitary
systems, emergency power supply
in hospitals), it may be necessary to
isolate selected consumers from the
power system in order to protect the
overall system. The overcurrent-time
protection functions are effective only
in the case of a short-circuit. Overloa-
ding of the generator can be measured
as a frequency or voltage drop.
Motor protection
For short-circuit protection, the stages
I>> and I
E
>> are available, for example.
Sudden load variations in running ope-
ration are acquired by the I
load
> func-
tion. For isolated systems, the sensitive
earth-fault detection (I
EE
>>, V
0
>) can
be used. The stator is protected against
thermal overload by s, the rotor by
I
2
>, start-time supervision and restart
inhibit. A locked rotor is detected via
a binary input, and shut down as fast
as required. The restart inhibit can be
deactivated by an “emergency start”.
The undervoltage function prevents a
start when the voltage is too low; the
overvoltage function prevents insu-
lation damages.
1
2
3
4
5
6
7
8
9
10