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FAQ
Frequently Asked
Questions
Ground Connections
Two different ground connection systems
What would happen if the ground connection were eliminated?
Conclusions
The ground connection is a element very important to guarantee
the safety of all the devices installed in the power lines. As a
result, this is one of the main issues to be considered during the
installation of the couplers.
The Capacitive Couplers for medium voltage power lines are
used for the transmission of PLC-BPL signals on a frequency
range from 2 to 100 MHz.
The couplers have two different ground connections (the connection to
the ground and the shield of the coaxial cable), so the installation of a
coupler could, in some cases, involve two different ground systems.
Some particular situations must be considered when we install a
coupler.
This paper has been prepared to give an answer to several questions
received about what would happen if we eliminate the ground
connection of any of the Capacitive Couplers, once they are installed.
Two different ground connection systems
ARTECHE Capacitive Couplers for medium voltage power
lines used for the transmission of PLC-BPL signals are made
up of a silicone module that houses the capacitive part and
that provides the necessary electrical insulation, and a
polyurethane plastic element which houses the tuning
circuitry together with the ground connections and the TNC/BNC
connector for the signal cable.
The next picture/diagram shows the scheme of the internal
configuration of the capacitive couplers (Pic.1).
Pic. 1
In the installation of the capacitive couplers, two different
grounds must be considered:
When the ground references are the same, the whole ground system
will be always at the same voltage.
(1) The one connected by the ground screws of the coupler
that is the ground connection of the power line to which the
coupler must be connected to get a reference for the high
voltage circuit.
Otherwise, if the ground references are different, a voltage difference
could appear between the two different ground systems, due to
failures in elements in the power line or to the working conditions of
the lightning arresters.
(2) The ground of the coaxial cable connected to the
TNC/BNC connector that corresponds to the shield of the
coaxial cable. This shield should be grounded at the PLC-BPL
repeater.
In this case the capacitive coupler is an element connected to these
two ground systems, so it is the device that should withstand this
difference of voltages. To protect the device in this situation, the
coupler has been designed to withstand a 5 kV insulation between
the ground connections and the TNC/BNC signal connector.
Depending on the situation in field and on how the distribution
network has been designed, both ground connections could
be connected to the same ground reference or to different
ones.
Ground connections
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FAQ
Frequently Asked
Questions
What would happen if the ground connection were eliminated?
 On the side of the TNC/BNC connector, there is 0 Volts,
because of the ground connection of the coaxial cable in the
PLC-BPL repeater.
If a capacitive coupler or any electrical device losses the
ground reference, the working conditions of the device are
different from the ones defined as normal working conditions.
These situation should not happen because the device is not
prepared to withstand the ground reference disconnection.
 The transformer insulation works up to 5 kV because it has
been designed to withstand temporary overvoltages but not
the voltage generated because of the elimination of the
ground connection. Thus, the transformer will not withstand
this voltage.
Let’s see what would happen in this situation (Pic. 2):
 The ground reference is lost, so the whole system will be at
V volts (the voltage of the line) on the side of the drain coil
because of the voltage of the power line.
 The transformer will fail and the coupler will stop working in
communications because of that.
Pic. 2
This situation will provoke the following scenario (Pic. 3):
ground but if the coaxial cable is disconnected from the
PLC-BPL repeater, the ground reference will be lost again
and a risky situation will come up.
 The system suddenly will have a new ground reference
through the TNC/BNC connector and the coaxial cable
connected to the PLC-BPL repeater. This connection
maintains the reference of the system.
 In this case, if the coaxial cable has an extra ground
connection (coax grounding block) before being connected
to the PLC-BPL repeater, this will avoid possible risks for the
people working in the PLC-BPL repeater.
 The voltage on the coaxial cable connected to the PLCBPL
repeater will not be so high while it is connected to
Pic. 3
Ground connections
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FAQ
Frequently Asked
Questions
Conclusions
The ground connection is a very important element in any
power line to guarantee the coupler’s normal and safe working
conditions and that can not be eliminated. The electrical safety
of the device will depend on this connection.
ARTECHE capacitive couplers have two different ground
connections, one is the connection to the ground the coupler,
grounded by a direct connection to ground and the other one
is the shield of the coaxial cable, grounded at
Ground connections
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the PLC-BPL repeater.
ARTECHE capacitive couplers have an internal 5 kV isolation to
withstand the possible overvoltages between the two different
ground connections.
In every device connected to a voltage power line could happen the
same. If the ground connection is removed, the working conditions
and the safety of the entire system would change and a significant
failure could happen.
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