This electric current will not only be that of the installation itself, but may also be part of the neutral current of neighboring installations. It therefore follows that the grounding wires of an installation may carry a significant current even when the main supply to that installation is switched off. This could clearly cause a hazard if in a potentially explosive part of an installation, such as a petrol storage tank, the ground wire were to carry part of the neutral current of a number of installations. Caravan power supply
The primary winding of the transformer must be RCD protected unless the equipment fed is to be used indoors.
How can one demonstrate the difference among earthing systems we have? Requirement #3 Reference: Practical Grounding, Bonding, Shielding and Surge Protection G. Vijayaraghavan, Mark Brown and Malcolm Barnes ( Buy hardcopy from Amazon) supply, each socket being fed by its own individual transformer.
Construction sites A Sockets on a construction site must be separated extra-low voltage (SELV) or protected by a residual current circuit breaker (RCD) with an operating current of not more than 30 mA, or must be electrically separate from the rest of the Requirement #5
The special requirements for construction sites do not apply to temporary buildings erected for the use of the construction workers, such as offices, toilets, cloakrooms, dormitories, canteens, meeting rooms, etc. These areas/buildings are not subject to changes as construction work progresses and are thus exempt from these requirements. IPX5 The objective of electrical installation on a construction site is to provide lighting and power to enable the work to proceed.
By the very nature of the installation, it will be subjected to the kind of rough treatment, which is unlikely to be applied to most fixed installations. Electrical installations where use of TN-C-S system is prohibited (photo credit: Edvard Csanyi) The electrical installation of a marina is subject to hazards not usually encountered elsewhere. These include the presence of water and salt, the movement of the craft, increased corrosion due to the presence of salt water and dissimilar metals and the possibility of equipment being submerged due to unusual wave activity in bad weather.
Pl) Minimum degree of protection The power supply to a caravan must be made using approved type of coupler at a height of not more than 1. The coupler socket (fixed to the caravan body) must have a spring-loaded lid, which will protect the socket when caravan is traveling.
The use of electrical systems in these cases will depend on the zone of use. These zones are defined in each case depending on the presence of vulnerable human body in the vicinity. Use of lower-voltage isolated systems, ground fault alarms and RCD is advised depending on the application.
Zone A clear notice must be affixed near the socket to indicate voltage, current and frequency of the supply required by the caravan. IPX8 TN-C-S system Cables and their connections must not be subjected to strain, and cables must not be run across roads or walkways without mechanical protection. Circuits supplying equipment must be fed from a distribution assembly including overcurrent protection, a local RCD if necessary and socket outlets where needed.
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Marina supply systems For this reason, the use of TN-C-S supply system is prohibited in the case of petrol-filling stations. Such installations must be fed from TN-S supply systems. Schematic of a TN-C-S system
Each socket orgroup of sockets must be provided with a durable and legible notice giving instructions for the electricity supply. Go back to Instalations ↑
Where multiple single-phase sockets are installed on the same pontoon, they must all be connected to the same phase of the supply unless fed through isolating transformers. The effect of any contact with live electrical parts could therefore be particularly dangerous. A hospital where open-heart surgery is performed poses even greater danger because of the effect of stray electric currents finding their way to the human heart through medical appliances used in the treatment.
Also explosive hazards may exist in certain hospital locations handling anesthetic gases.
Most sockets are likely to be fed at 110 V from centertapped transformers and so will comply with this requirement. Edvard Csanyi Electrical engineer, programmer and founder of EEP. Highly specialized for design of LV/MV switchgears and LV high power busbar trunking (<6300A) in power substations, commercial buildings and industry facilities.
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It is usual for such installations to be subjected to thorough inspection and testing at intervals, which will never exceed 3 months. Your real name * Six levels of voltage are recognized for a construction site installation. They are: IPX4 for outdoor pools A caravan is a leisure accommodation vehicle, which reaches its site by being towed by a vehicle.
A motor caravan is used for the same purpose, but has an engine, which allows it to be driven; the accommodation module on a motor caravan may sometimes be removed from the chassis. Montazeri For example, the loss of the main protective conductor and a fault to the metalwork in the caravan is likely to go unnoticed until someone makes contact with the caravan whilst standing outside it. These are as follows: Requirement #1 Best Regards Dear sir Home / Technical Articles / Electrical installations where use of TN-C-S system is prohibited The requirements of the Electricity Supply Regulations do not allow the supply neutral to be connected to any metalwork in a caravan, which means that TN-C-S supplies must not be used to supply them.
By Edvard | November, 6th 2015 | 2 comments | Save to PDF This rules out the use of TN-C-S supplies for marinas. Where this is the supply provided, it must be converted to a TT system atthe main distribution board by provision of a separate ground electrode system of driven rods or buried mats with no overlap of resistance area with any ground associated with the TN-C-S supply. Example of a heavily burned hot conductor in the receptacle.
This is another fire hazard not uncommon in the marina environment (photo credit: qualitymarineservices. Net) The equipment used must be suitable for the particular supply to which it is connected, and for the duty it will meet on site. Where more than one voltage is in use, plugs and sockets must be non-interchangeable to prevent misconnection.
This socket must be connected to a main isolator with RCD protection with an operating current of 30 mA, which on operation will disconnect all live conductors. All metal parts of the caravan, with the exception of metal sheets forming part of the structure, must be bonded together and to a circuit-protective conductor, which must not be smaller than 4 mm 2 except where it forms part of a sheathed cable or is enclosed in conduit. C IPX2 for indoor pools The neutral of a TN-C-S system must not be connected to the grounded system of a boat so that the hazards, which follow the loss of continuity in the supply PEN conductor, are avoided.
All dangers associated with fixed electrical installations are also present in and around caravans. Added to these are the problems of moving the caravan, including connection and disconnection to and from the supply, often by unskilled people. Grounding is of prime importance because the dangers of shock are greater.
Caravan vehicle power supply (photo credit: withoutahitch. Au)
, where danger to human beings is more probable. The reason for this is that in some of the locations, the human beings are partly unclothed, without shoes and are in contact with water or their body is wet. Swimming pool wiring (photo credit: mikeholt.
Com) A real danger can arise when the non-current-carrying metalwork of an installation is connected to the system’s neutral, as is the case with a TN-C-S-fed system. The ground system is effectively in parallel with the neutral and can thus share the normal neutral current under certain conditions. Let’s discuss the requirements for these consumers briefly below // IPX5 where water jets are likely to be used for cleaning B Socket outlets must be enclosed in distribution assemblies, fixed to the outside of the assembly enclosure or fixed to a vertical wall.
Sockets must not be left unattached, as is often the case on construction sites. Like residential caravans, such craft require external power supplies, and this section is intended to ensure the safety and standardization of such supplies. The marina will often include shore-based facilities such as offices, workshops, toilets, leisure accommodation, and so on and is exempt from these special requirements.
Marine power supply (photo credit: whitehallannapolis. Com) If the marina is large enough, it may be that the supply company will provide a separate transformer and a TN-S system.
Apart from the use of TN-S system certain additional requirements are also applicable. Another typical situation where TN-C-S systems are not used is the marina power supply system. A marina is a location, often a harbor, for leisure craft to berth.
Requirement #4 The zonal concept for a particular swimming pool (credit: iee. Org) Distribution and supply equipment must be protected to IP44. This means provision of mechanical protection from objects more than 1 mm thick and protection from splashing water.
Such equipment will include switches and isolators to control circuits and to isolate the incoming supply.