Technische Alternative CAN-EZ3, Общая информация, Установка и подключение, Основные функции

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Installation and connection – CAN bus
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• Avoiding earth loops
Where a bus cable is routed between several buildings, ensure that earth loops are avoided.
The reason for this is that buildings actually have different potentials compared to the earth
potential. An earth loop is created when connecting one cable screen in each building
directly with the equipotential bonding system. In other words, a current flows from the
higher to the lower potential.
For example, if lightning strikes near one of the buildings, the potential of that building will
briefly be raised by several kV.
In this case, the equalizing current flows to earth via the bus screen and causes an extreme
electromagnetic input which can result in the destruction of the bus components.
Lightning protection
Efficient lighting protection is highly dependent on good building earthing that meets the relevant
regulations.
An external lightning protection system offers protection against a direct lightning strike.
In order to protect against voltage surges in the 230 V mains supply cable (indirect lightning strike),
appropriate lightning conductors and surge arresters compliant with local regulations must be fitted
in the upstream distribution systems.
In order to protect the individual components of a CAN network against indirect lightning strike, we
recommend the use of surge arresters specifically developed for bus systems.
Example: CAN bus surge arresters CAN-UES from Technische Alternative
Gas discharge arrester for indirect earthing EPCOS N81-A90X
Examples of different network versions
Key to symbols:
Max. cable length: 1000 m at 50 kbit/s
The screen must be continued at each network node and be connected to the device earth (GND).
The screen earthing or GND must only be implemented
indirectly via a gas discharge arrester.
Ensure that no unintentional direct connection of earth or screen and the earth potential is created
(e.g. via sensors and the earthed pipework).
... device with its own power supply (RSM610, UVR16x2, UVR67 etc.)
... device is supplied by the bus (CAN-I/O 45, CAN-MTx2 etc.)
... terminated (end devices) ... open termination
... gas discharge arrester for indirect earthing