Circuit breakers may be
used place fuses, which case the circuit breaker may also provide the
means isolation, although further means isolation usually provided
so that maintenance can carried out the circuit breakers themselves.Overcurrent, short circuit and earth fault protection
239
Emergency switching involves the rapid disconnection the electrical
supply single action remove prevent danger.
The purpose functional switching provide control electrical cir-
cuits and equipment normal service.
Emergency switching for use anyone. The Regulations
acknowledge the growth the number electronic dimmer switches being
used for the control and functional switching lighting circuits. They should installed where danger may arise and be
clearly identified emergency switches.2.
When selecting protective device must give consideration the fol-
lowing factors:
● the prospective fault current,
● the circuit load characteristics,
. Push-buttons
used for emergency switching must coloured red and latch the stop
or off position.
Electrical machines must provided with means emergency switch-
ing, and person operating electrically driven machine must have
access emergency switch that the machine can stopped an
emergency.When the device controls discharge lighting circuit must
have current rating capable switching inductive load.
Safety First
Isolation
Isolation and switching for protection
is important safety measure the
electrotechnical industry.
Definition
Functional switching involves the
switching off, varying the
supply, electrically operated equip-
ment normal service.
Overcurrent protection
The consumer’s mains equipment must provide protection against overcur-
rent, that current exceeding the rated value (Regulation 430. Plugs and socket outlets cannot
be considered appropriate for emergency disconnection supplies.
The purpose emergency switching cut off the electrical energy rap-
idly remove unexpected hazard.
Functional switching involves the switching off, varying the sup-
ply, electrically operated equipment normal service. The func-
tional switch must capable performing the most demanding duty may
be called upon perform (IEE Regulations 537.
The device must capable interrupting the total steady current the cir-
cuit appliance.5.
Definition
Emergency switching involves the
rapid disconnection the electrical
supply single action remove
or prevent danger.4. Where contactors are operated remote control they
should open when the coil de-energized, that is, fail safe.3).1 and 2).2).2. Fuses
provide overcurrent protection when situated the live conductors; they
must not connected the neutral conductor.
Functionalswitching isfortheuseroftheelectricalinstallationorequipment. The remote stop/start arrangement could meet this require-
ment for electrically driven machine (Regulations 537. Devices
which are suitable for emergency switching are switches, circuit break-
ers and contactors. The device used for emergency
switching must immediately accessible and identifiable, and capable
of cutting off the full load current
