Electric connections

An electric connection

We can not longer even imagine life without electricity. It is an essential feature of a home. This connection is established with the start of construction so that things like electric mixers and other devices can be used, which help get the work done more easily. A cable line in the ground is not an architectural problem. Energy distributors require applicants for an electric connection to place an electric meter box on the edge of the property, on a fence or the wall of a house, so that it is accessible to a worker even if the owner of the house is not at home. It is also necessary to ensure the placement of such an electric meter box if you are renovating a house and at the same time you are changing the internal distribution of electricity.

Equally essential equipment for a home is a lightening rod. It is added after completion of the rough construction, when the roof has been completed. The part of it on the roof has a purposeful character and must be professionally designed and at the same time installed so that the earth connection is functional and safe.

Connections for electrical energy
All consuming devices / captation devices are connected to the distribution main of the electricity supplier by an electrical connection. Electrical connections are divided according to:

  1. the method of making a connection:
    • connections made by an outdoor line
    • connections made by a cable placed in the ground
    • connections made by a combination of the previous two methods
  2. the voltage level:
    • connections up to 1 kV
    • connections of more than 1 kV up to 45 kV
    • connections over 45 kV
  3. An electric connection according to STN 33 3320:3/2002 begins with the branching from the equipment of the public electricity distribution main (aerial or cable) in the direction of the customer. A connection up to 1 kV ends with a service box (this must be sealed and labeled with a safety plate – *lightening bolt*).
    The service box is:

  • the main house fuse box HDS (SP), if the connection is made to an aerial main (by a bare conductor, an insulated conductor or an aerial-suspended cable). It is placed at a height of 2.5 to 3 m
  • • the main house fuse box (SP, SP+RE), if the connection is made by an underground cable

It is placed such that the lower edge is 0.6 m above the definitively treated terrain. Only one electrical connection should be made for each building.

Protection in the service box is done with screw-in or blade fuses and must be minimally one degree higher (from the line of nominal currents according to STN 33 0125) than the protection before the electric meter. Fuses for individual consumers must be properly labeled.

For reasons of safe operation and work there must be minimally 0.8 m of free space in front of the service box.

A service box can in some cases (garages, cottages,...) be replaced by a distribution panel in a publicly accessible space, in which electric meters are placed for a number of buildings.

Connections made by a cable line

If the connection of a building is made by looping the cable main of the electrical supplier, the connection is made up of only a service box, possibly only a set of fuses in the distribution box.

If it is advisable, the service box can at the same time also be a main switch box for the distribution equipment; in this case a part of the box is used as the main switch box and part as a service box.

If it is advisable, one fuse box (SP) or main switch box of the distribution equipment of the electrical supplier can also serve for the connecting of several buildings. Each feed into these buildings must be independently connected and protected in this box. The minimal diameters for cables of an electric connection are 4 x 16 mm2 Al with branches in the main switch or fuse box of the cable line from the independent safety element.

With the making of a cable connection by branching with a T-connector (with the consent of the supplier) the minimum cross-section is 25 mm2.

The service box is a part of the connection. It is usually placed on the boundary of the customer’'s property such that its door and detachable cover of the cable space are in a publicly accessible spot.

The lower edge should be 0.6 m above the altered terrain. Depending on the local conditions, it’s possible to place it higher, up to 1.5 m.

If the cable connection branches from an aerial line, the service box is placed in a publicly accessible place. It can also be placed on the support of the aerial line at a height of 2.5 to 3 m.

If the cable branches from an aerial line this cable on the pole of the aerial line must be protected from mechanical damage by a protective pipe to a height of minimally 2.5 m. At the point of the cable’s entry into the protective tube measures must be taken against the leaking in of water.

Connections made by aerial cables

An aerial connection is prepared from insulated conductors, hanging/suspended cables or self-supported cables. The use of bare conductors is permitted only in unique cases and with the consent of the electricity supplier. The use of direct-burial cables hanging on a wire or on a rope is illegal.

The minimum cross-sectional area of the conductors is 16 mm2 AlFe with bare conductors and 16 mm2 Al with hanging cables.

The part of the connection from the last support (roof structure,...) to the service box should be as short as possible. Cable connections are prepared preferentially. The cable and the insulated conductor cannot be interrupted or extended.

With the establishing of a new connection, the outside part of a wall from the building using the electricity must be used for placing the part of the connection attached to the building.

With reconstruction of an electrical connection it is possible to keep the original part of the connection as a feeder only if it does not traverse the internal spaces of the building and if they are suitably made for limiting the unauthorized drawing of electricity.

Both parts of the feeder can be connected to the last support. The connection of the conductors must be protected by insulation and must be visible from a publicly accessible location.

With the attaching of cables or conductors to a wall measures must be taken against the leaking in of water.

The service box is placed in a publicly accessible location. Preferentially it is placed on a support (pole) of the electrical energy main and the line from the service box to the meter box is considered as the feed.

If the support for the public main is situated on an object of the building of the customer, the lower edge of the service box should be at a height of 2.5 to 3 m above the definitively altered terrain.