Extra-Low Voltage (ELV) is a reduced electricity supply voltage used in houses, parks, swimming pools, gardens, wandering-lead hand lamps & portable appliances for outdoor use for eliminating the risk of electric shock.
An AC voltage below than 50 volts and DC voltage below 120 volts are considered ELV. Systems like telephone, data transmission, LAN, CCTV, fire alarm & master clock systems operate on ELV.
With ELV the danger of serious harm is significantly smaller as compare to normal voltage therefore ELV is used in order to reduce the danger of electric shock.
Types of ELV:
Protective ELV (PELV), Separated ELV (SELV) & Functional ELV (FELV) are the three types of ELV system.
Separated Extra-Low Voltage:
In such type of system a single fault cannot be the reason of electric shock because the Low-voltage output is electrically separated from earth & other systems. Such type of ELV design consultant KSA, UAE, Qatar and Gulf based countries use extensively in their home base decoration.
There is no provision for earth in SELV circuit. These systems are used in location where the operation of electrical equipment presents a serious hazard. For example, using electric equipment’s in swimming pool, medical apparatus and amusement parks.
This measure depends on supplying power at extra-low voltage from the secondary windings of isolating transformers especially designed according to national or to international (IEC 60742) standard. The impulse withstands level of insulation between the primary and secondary windings are very high, and/or an earthed metal screen is sometimes incorporated between the windings. The secondary voltage never exceeds 50 V rms.
Protective Extra-Low Voltage:
These systems are for general use where low voltage is required or when preferred for safety reason excluding the high risk locations like swimming pool.
This system is for general use where low voltage is required, or preferred for safety reasons, other than in the high-risk locations noted above. The conception is similar to that of the SELV system, but the secondary circuit is earthed at one point.
However, protection against direct contact hazards is generally necessary, except when the equipment is in zone of equipotential bonding, and the nominal voltage must be equal to or less than 25 V rms, and the equipment is used in normally dry locations only, and large-area contact with the human body is not expected. In all other cases, 6 V rms is the maximum permitted voltage then direct contact is not any risk.
Functional Extra-Low Voltage:
Such type of systems can be used just for functional purposes like machine control systems. A voltage of 50 V or less is used, but not all of the requirements relating to SELV or PELV are fulfilled here in this case. Appropriate measures must be taken to ensure protection against both direct and indirect contact hazards, according to the location and use of these circuits.
Benefits of ELV:
It is these benefits that are currently driving the rapid growth of ELV design consultant in KSA, and around the globe. Because of significant reductions in CO2 emissions due to lower power requirements, and reductions in raw material usage, result from the need for fewer street cables. The end result is significantly lower costs compared to traditional LED solutions, due to improved technology.
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