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3RH, 3TX, LZX coupling links
SIRIUS System Manual
GWA 4NEB 430 0999-02b
6-9
6.2.8 Explanation of terms
Electrical isolation
There is no conductive connection between the input circuit and the output
circuit. Electrical isolation is ensured by the in-built relay and, in the case of
semiconductor outputs, by means of optocouplers.
Safe isolation
Safe isolation provides protection against shock currents in different circuits.
It is implemented by means of increased creepages and clearances.
Distinction between
terms
Electrical isolation is not necessarily safe isolation.
Safe isolation is a protective measure against shock current, the primary
purpose of which is to prevent injury. It prevents the voltage of one circuit
crossing over into another.
For the insulation coordination of equipment, the standard specifies values
for the rating of the creepages and clearances.
In the case of safe isolation, these values must be selected by means of
double or reinforced insulation.