Isolator switch
Encyclopedia
In electrical engineering
, a disconnector or isolator switch is used to make sure that an electrical circuit can be completely de-energised for service or maintenance. Such switches are often found in electrical distribution and industrial
applications where machinery must have its source of driving power removed for adjustment or repair. High-voltage isolation switches are used in electrical substations to allow isolation of apparatus such as circuit breaker
s and transformer
s, and transmission lines, for maintenance. Isolating switches are commonly fitted to domestic extractor fans when used in bathrooms in the UK. Often the isolation switch is not intended for normal control of the circuit and is only used for isolation.
Isolator switches have provisions for a padlock
so that inadvertent operation is not possible (see: Lockout-Tagout). In high voltage or complex systems, these padlocks may be part of a trapped-key interlock system
to ensure proper sequence of operation. In some designs the isolator switch has the additional ability to earth
the isolated circuit thereby providing additional safety. Such an arrangement would apply to circuits which inter-connect power distribution systems where both end of the circuit need to be isolated.
The major difference between an isolator and a circuit breaker
is that an isolator is an off-load device intended to be opened only after current has been interrupted by some other control device. Safety regulations of the utility must prevent any attempt to open the disconnector while it supplies a circuit.
Standards in some countries for safety may require either local motor isolators or lockable overloads (which can be padlocked).
Electrical engineering
Electrical engineering is a field of engineering that generally deals with the study and application of electricity, electronics and electromagnetism. The field first became an identifiable occupation in the late nineteenth century after commercialization of the electric telegraph and electrical...
, a disconnector or isolator switch is used to make sure that an electrical circuit can be completely de-energised for service or maintenance. Such switches are often found in electrical distribution and industrial
Industry
Industry refers to the production of an economic good or service within an economy.-Industrial sectors:There are four key industrial economic sectors: the primary sector, largely raw material extraction industries such as mining and farming; the secondary sector, involving refining, construction,...
applications where machinery must have its source of driving power removed for adjustment or repair. High-voltage isolation switches are used in electrical substations to allow isolation of apparatus such as circuit breaker
Circuit breaker
A circuit breaker is an automatically operated electrical switch designed to protect an electrical circuit from damage caused by overload or short circuit. Its basic function is to detect a fault condition and, by interrupting continuity, to immediately discontinue electrical flow...
s and transformer
Transformer
A transformer is a device that transfers electrical energy from one circuit to another through inductively coupled conductors—the transformer's coils. A varying current in the first or primary winding creates a varying magnetic flux in the transformer's core and thus a varying magnetic field...
s, and transmission lines, for maintenance. Isolating switches are commonly fitted to domestic extractor fans when used in bathrooms in the UK. Often the isolation switch is not intended for normal control of the circuit and is only used for isolation.
Isolator switches have provisions for a padlock
Padlock
Padlocks are portable locks used to protect against theft, vandalism, sabotage, unauthorized use, and harm. They are designed to protect against some degree of forced and surreptitious entry.- History :...
so that inadvertent operation is not possible (see: Lockout-Tagout). In high voltage or complex systems, these padlocks may be part of a trapped-key interlock system
Interlock (engineering)
Interlocking is a method of preventing undesired states in a state machine, which in a general sense can include any electrical, electronic, or mechanical device or system....
to ensure proper sequence of operation. In some designs the isolator switch has the additional ability to earth
Ground (electricity)
In electrical engineering, ground or earth may be the reference point in an electrical circuit from which other voltages are measured, or a common return path for electric current, or a direct physical connection to the Earth....
the isolated circuit thereby providing additional safety. Such an arrangement would apply to circuits which inter-connect power distribution systems where both end of the circuit need to be isolated.
The major difference between an isolator and a circuit breaker
Circuit breaker
A circuit breaker is an automatically operated electrical switch designed to protect an electrical circuit from damage caused by overload or short circuit. Its basic function is to detect a fault condition and, by interrupting continuity, to immediately discontinue electrical flow...
is that an isolator is an off-load device intended to be opened only after current has been interrupted by some other control device. Safety regulations of the utility must prevent any attempt to open the disconnector while it supplies a circuit.
Standards in some countries for safety may require either local motor isolators or lockable overloads (which can be padlocked).