Normally,
each short circuit-, earth fault- or high voltage indicator needs a
power supply.
a) In order to avoid an independant supply, the necessary power should
be supplied by the controlled network.
b) The power supply should be independent of any maintanance and
control service (e.g. lithium battery).
A) Capacitive
power supply
Two potential plates are mounted
near a power transmission line. The supplied capacitive power will be
transmitted to a capacitor. This capacitor-charge guarantees the
function of the short circuit indicator. The above mentioned system can
only be applied with unscreended cables.
B) Auxiliary
voltage 9-110 VDC, 230 VAC
The power supply of the short
circuit indicator is carried out by a network which is independent of
the controlled network (e.g. emergency power net 230 VAC -- parallel
networks -- or similar systems).
C) Power
supply 230 VAC with capacitor buffering
The short circuit indicator is
supplied with power from the controlled network.
In case the operating voltage breaks down due to a short circuit, a
capacitor stores power which guarantess all switching and indicating
functions once. After the net has been reclosed, the short circuit
indicator resets itself, and the capacitor is being recharged.
D) Power
supply 230 VAC with battery buffering
The power, which is necessary for
using the short circuit indicator, can be supplied by the controlled
network. This power breaks down in case of a short circuit. However,
the operating voltage is already provided by an accumulator, which is
continuously charged. This version of the indicator also provides a
self-acting reset after a preadjusted time if the system is not working.
E) Battery (lithium type)
A battery (lithium type) supplies
the short circuit indicator with the necessary operating voltage. Each
battery is exchangeable. The life time of the battery is between 5 and
10 years (depending on the version of the indicator).
F) Inductive power supply
The power for operating the short
circuit indicator is gained via an inductive coupling to a power
transmitting line. Via a coil, the operating current (minimum 10 A)
generates as much power as the operation of the short circuit indicator
requires. This system is only possible together with screened
single-core-cables.
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