. The device shall release acoustic
and/or optical signal, automatically disconnect the supply.2.2.
After the occurrence first fault (in case when the supply not automatically
disconnected) conditions for the disconnection the supply the event second fault as
specified for and systems shall apply, depending whether all the exposed conductive
parts are interconnected protective conductor (collectively earthed) are earthed groups
or individually.FUNDAMENTAL RULES FOR PROTECTION AGAINST ELECTRIC SHOCK
46
According Czech standards the highest earthing resistance firmly given Ω
(exceptionally small systems 100 Ω).
Where exposed conductive parts are earthed groups individually, the conditions TT
system are considered.g. recommended that first fault
be eliminated within the shortest possible time. when the first fault occurs (e.4. for operation rooms hospitals,
for heavy industry machinery). For such system the maximum
required disconnecting time depends whether this system the neutral conductor is
distributed not according Table 5.
Table 5.
In systems, the use the following monitoring and/or protective devices recognized:
- insulation monitoring devices,
- overcurrent protective devices,
- residual current protective devices.
Inspite rare use systems this systems are unavoidable cases when necessary to
finish some work, operation etc. case interconnection all exposed conductive parts with earthed protective
conductor system arises after the occurrence first fault.
An insulation monitoring device shall provided indicate the occurrence first fault
from live part exposed conductive parts earth.4 The maximum disconnection time case second fault system
Installation nominal voltage Disconncting time (s)
Uo (V) Nutral not distributed Nutral distributed
120-240 0,8 5
230/400 0,4 0,8
400/690 0,2 0,4
580/1000 0,1 0,2
Other conditions for the case second fault system are similar the ones TT
systems
