WO2014098699A1

WO2014098699A1 - Switchboard

Info

Publication number: WO2014098699A1
Application number: PCT/SE2013/000199
Authority: WO
Inventors: Lars Hjort; Stefan Larsson; Susanne LARSSON
Original assignee: Nätstations Alliansen Ab; SÄLLSTRÖM, Thomas
Priority date: 2012-12-21
Filing date: 2013-12-22
Publication date: 2014-06-26
Also published as: SE537059C2; SE1200786A1

Abstract

A low voltage switchboard for distribution of electric power to a plurality of electric power consumers, comprises an electrical equipment containing switching equipment (11, 12, 13, 21, 22) and a plurality of circuit breakers (3, 15), and an openable enclosure (1) enclosing the electrical equipment. The enclosure comprises a watertight container (10) disposed with watertight connection means (11, 12, 13, 22) enclosing the circuit breakers.

Description

Switchboard

TECHNICAL FIELD

The present invention relates to a switchboard for distribution of electric power. Especially the invention concerns a switchboard for local

distribution of low-voltage electrical power. Such a switchboard comprises electrical equipment containing switching equipment and a plurality of circuit breakers arranged in a grounded enclosure. The enclosure shall protect the electrical equipment from meteorological influences and prevent that a third party may come into contact with the live parts. In particular the invention relates to a cable connected switchboard with a main switch and a plurality of distribution switches.

By the term circuit breaker shall be construed a circuit breaker with built- in protection for residual current. Particularly, a distribution switch construes a MCCB (Moulded Case Circuit Breaker) which may be termed modular circuit breaker with overload and short circuit protection. Such a switch comprises a thermal and a magnetic release and means for extinguishing an induced arc. By low-voltage electric power should be understood power systems rated up to 1000 volts. In Sweden it is usually limited to 400 volts but may be different especially in other countries. Circuit breakers are divided into different sizes, usually according to the rated operating current of 100-630 A. An embodiment of a switchboard comprises a busbar system of three phases plus the neutral forming the base in e.g. a switching cabinet. The cabinet comprises an outer enclosure that prevents access by a third party but is simultaneously openable for installation and service of the

constituent components. To the busbar system is connected a plurality of circuit breakers which distribute the power to an equal number of cable connected consumers. Examples of distribution of electric power using a switchboard can be electricity to retail stores in a mall or distribution to one or more properties in a residential area.

PRIOR ART

The most common type of low-voltage switchboards is termed wiring cabinet. They are often meters high and are frequently placed in urban and residential areas. Such a switchboard includes enclosed electrical equipment for 400 V distribution of electric power to buildings and houses. A conventional wiring cabinet has a foundation that is buried in the ground. The cabinet has at the front one or two fully covering doors with locks that require special keys. Up from the ground an incoming electrical cable protrudes that is connected to a main breaker inside the wiring cabinet. The main switch is connected to a busbar system on which a plurality of distribution switches is mounted. The busbar system is provided in the cabinet spine and comprises five busbars mounted in parallel, one for each of the three phases, one for the zero and one for grounding. The busbars are usually made of aluminium and covered with plastic except in a milled slot in which an electrical device can be

connected. Covering the busbars with plastic make them touch safe even when they are energized. It is an assurance for those who need to fix something in the cabinet, such as when a fuse has blown.

The main switch and distribution switches are comprised of circuit breaker with fuse functions for each output phase. They are screwed directly onto the busbars and connected to an output cable that supplies the user with electric power. The cover of the circuit breaker may in many cases serve as a disconnector. When the circuit breakers are installed, closing the cover of the circuit breaker connects the power automatically and vice versa. Loop mounted wiring cabinets can contain two main breakers wherein the wiring cabinets at fault in the loop can be fed from two ways. Wiring cabinets built above ground are exposed to damage from, for example, cars, machines, people, and weather. The switchboard usually consists of a metal enclosure (approximately 1 m high, 0.6 m wide and 0.3 m deep) with low-voltage electrical equipment mounted inside the enclosure. Wiring cabinets have a simple locking mechanism which by a special key can be opened by a third party. Wiring cabinets are an environmental burden of people's immediate environment. Wiring cabinets above ground are inspected at least every eighth year.

Some examples of shortcomings with wiring cabinets above ground are as follows:

• Work machines such as snowploughs damage the wiring cabinets.

Wiring cabinets are simply run down, damaged or opened , which means that they can be a danger to third persons such as children, etc.

• Cars may hit and damage the wiring cabinets. It often gives the

result that they become damaged in such a way that children, animals, etc. can enter into a cabinet and hurt themselves.

• People scribbling and pasting advertisements on the cabinets. When making graffiti there is a certain risk of electric danger to the scribbler. There is also a risk of an electric danger when cleaning up graffiti.

• For example at winter snow may be excavated up against or over the cabinets so wiring cabinets becomes hidden. Next time at snow cleaning the wiring cabinets are not visible and the wiring cabinets may be massacred, with the result that wiring cabinets may become hazardous, especially for the third person.

• Aesthetically unattractive to people's immediate environment. This means that the wiring cabinets are placed along the streets, building facades and in places that may be of interest from a cultural point of view. • Wiring cabinets above ground are inspected according to the established practice every eight years by utility companies, which results in high costs.

To avoid these disadvantages, it is known to arrange a switchboard underground. The switchboard is then placed in a well with a not easily openable cover. The well is in this configuration an external enclosure that protects electrical equipment from access by a third party. The above- indicated shortcomings are avoided with this solution but new

shortcomings occur. The main issue to be solved is the switchboard's resistance to drenching with water or rising groundwater.

Known switchboards are air insulated. This means that input electrical equipment is arranged with such clearance distance and so insulated that no arcs or current paths between components with different potentials can be established in an air medium. At extreme weather conditions, however, the electrical equipment may become surrounded by water. Water conducts electricity better than air and a plurality of current paths may be formed in the water. Large amounts of energy can then be transported between live parts in the wiring cabinet. This can lead to major injuries and sometimes explosions. It is also not advisable to approach a

switchboard that is under water.

From DE 1949694 is previously known an underground substation in which electrical components are fixed to a hinged lid and connected via flexible conductors to an incoming cable. The object of the substation is to prevent superstructure and thus not disturb the townscape. By flexibly attaching the cable to the equipment, the lid is easily openable whereby the equipment is easily accessible.

From EP 0982822 (Kienhuis) is previously known a distribution station for electric power. The distribution station is embedded in the ground and has the task to withstand both flooding and rising groundwater. The known distribution station consists of a box embedded in the ground with an outer and an inner crossing cover. The outer cover includes a gas tight enclosure with the opening facing down. The enclosure partially encloses the inner cover. The inner cover includes a frame on which the actual switching equipment is mounted. Around the inner cover is provided a channel for surface water drainage. When the outer cover is closed the surface water flows down into the channel. At a rising of the ground water the outer cover is acting as a diving bell and protects the switching equipment enclosed in the cover. For assembly and inspection the outer cover is first opened then the inner cover is opened and placed on end for convenient access to the equipment.

From US 3755637 (Gloviac) is previously known a subsurface positioned coupling structure for underground distribution of electric power. The coupling structure is designed for high-voltage electric power and has the task to resist flooding. The known structure is contained in a watertight tank comprising a base, a top and a manoeuvre turret welded together into a waterproof container. The manoeuvre turret contains three axes with chain connection to each switch which can be operated with an operating rod. The known coupling structure is as described a load switch. It does not provide any means for tripping at fault currents. A load switch is characterized in that it can carry and break a load current. A circuit breaker can carry and break a fault current which is much larger than such a load current.

The known load switch belongs to the technical field of high voltage which is substantially different from the field of low voltage. Among other things, large isolation distances and insulated penetrations are required for the electrical connections to the load switches. This makes the construction heavy and bulky and would be inappropriate for application in the low- voltage area. The known structure lacks means for tripping the circuit breakers. Introducing such switches would make the design even heavier and more bulky. Thus, a switchboard designed for high voltage would be highly inappropriate in the low-voltage area. The known structure is welded and therefore lacks an openable device which allows for

installation or service. The known load switch is placed in a tomb which lacks both lid and drainage.

DISCLOSURE OF THE INVENTION

An object of the invention is to seek ways to provide a method and an apparatus for improving a switchboard. Another object is to provide a switchboard that without adversely affecting the townscape is service friendly and resist flooding as well as a rising of groundwater.

These objects are achieved according to the invention by a switchboard according to the features in the characterizing part of the independent claim 1, and with a method according to the features in the independent method claim 8. Advantageous embodiments are stated in the dependent claims. According to the invention the switchboard includes an enclosure which prevents water penetration to the electrical equipment. In an embodiment the enclosure comprises a watertight container that encloses at least one electrical component. The electrical accessibility of the enclosed

component is performed by watertight connection means which are arranged through the container. The interconnection between the electrical components is arranged by insulated electrical conductors. Thus, should the switchboard become surrounded by water, the electrical function is not affected. In an embodiment the enclosure comprises a hermetic enclosure. The environment of the enclosure can by using an enclosed moisture absorber become completely dry. In such an

environment oxidation of the enclosed contact bodies is avoided. The electrical equipment comprises a plurality of circuit breakers and switching equipment for connection of the circuit breakers as well as incoming and outgoing electrical cables. In an embodiment the electrical equipment is protected by an enclosure that meets Ingress Protection Rating of IP67. First digit means that the equipment is dust tight which also includes all kinds of ingress protection. The second digit means that the equipment can be temporarily submerged in water without damage. In an embodiment the circuit breakers comprise a main switch and a plurality of distribution switches. In an embodiment the switchboard comprises a watertight container which accommodates a plurality of distribution switches. In an embodiment the enclosure comprises a watertight container enclosing the whole electrical equipment. The electrical equipment may also comprise means for remote reading of the equipment or manoeuvring the circuit breakers. Each joint between extrinsic cables and the access points of the switchboard is protected with a cable termination and shrink tubing.

By the electrical equipment being protected against both flooding and submersion in water the switchboard can operate even under water.

Current rush and arcs can then be avoided and the staff is safe to approach the switchboard to inspect or operate the distribution switches. Since the components are isolated the switchboard offers a safe

environment for the staff who will service the facility as well as for a third party and animals. The switchboard is only hazardous in the case that someone by using force breaks the facility (sabotage).

The electrical equipment is in an embodiment located in a well dug in the ground which well forms an outer enclosure that prevents access by a third party. The well is equipped with a cover which implies that the entire facility is protected from external impact. In an embodiment the cover is adapted to withstand the load of a vehicle such as for example a car. The well is thus capable of being located in a sidewalk or on a parking lot. Where the ground inclines the cover is arranged in parallel with the ground level. The entire well is then inclined or the cover is provided with a wedge-shaped frame. In an embodiment the well is square-shaped and open at the bottom for convenient drainage. In an embodiment the well comprises a well arranged in parallel or the like in which an operator can curl down and conveniently mount devices or perform service at the facility.

The switchboard according to the invention is especially intended to be placed below ground level but can also be used in wiring cabinets above ground.

The position of the switchboard is measured in the X and Y coordinates so that it is easy to find. All enclosures of electrical equipment is positioned in the well such that they are easily accessible for replacement or expansion. The facility is completely personal safe regarding electrical hazards. The enclosure enclosing the switchboard is sturdy and can withstand normal handling during assembly etc. The electrical equipment enclosed in the enclosure is capable of being submerged in water without the electrical properties being changed. Drainage for the disposal of water is arranged under the well and is connected to the surface water system.

The inventive concept also includes an enclosure for enclosing a circuit breaker so that it without being disabled is submersible in water. The circuit breaker is enclosed in a watertight container in which watertight connectors for incoming and outgoing conductors are arranged. In an embodiment these connectors include solid bars of a material which conducts current. In an embodiment the connector comprises a rod of copper. Other metals such as compound constructions may also be used. In an embodiment the connectors comprise insulation coated cables with end fittings that prevent water penetration. The cables are fixed in the container with a waterproof gland. The connection of the circuit breaker to the connectors on the inside of the container is trivial since this is made on the inside of the enclosure itself. A common bolt bond or flat connectors may be used. Connecting an electrical cable to any of the connectors on the outside of the container requires an extra consideration. An electrical cable generally consists of a conductor surrounded by insulation. The conductor includes a plurality of helical strands that make the cable bendable without breakage. However between the strands water may penetrate and follow the cable inside the insulation. Therefore the cable itself cannot usually be led into the enclosure to the circuit breaker. Water would then through the space between the strands penetrate the enclosure. However if the cable end is sealed so that no water is able to penetrate a cable gland may be used. In an embodiment of the invention such sealed cable end comprises a metal sleeve provided with rigid base clamped about the cable conductor and heat-shrinkable tubing that seals the joint. With such a closed cable end conductors can be replaced with a cable and a waterproof grommet such as a gland.

The encapsulated electrical equipment is in an embodiment attached to transverse mounting beams in the well. The beams are placed near the well cover for easy installation and service. Between the circuit breakers a plurality of brackets are arranged for connecting the circuit breakers. Each bracket is enclosed in an insulating sheath and has at each end a connector that fits into the connector of the enclosed circuit breakers. In an embodiment the brackets comprise a rolled up stocking of an elastic insulation such as silicone rubber. After installing the bracket the elastic stocking is stretched over the splice to a waterproof joint. The

interconnection itself of the circuit breakers is thus both touch-safe and waterproof. In an embodiment a bracket comprises three conductors isolated from each other and enclosed in a common insulation from the surroundings. The corresponding contacts in this embodiment are dived into three parts and fit into a corresponding three-part contact device in the enclosure of the breaker.

In an embodiment of the invention the encapsulated electrical equipment comprises a plurality of distribution switches. Compared to the version where each distribution switch has its own enclosure, a common enclosure means that the connections between the distribution switches can be made inside the enclosure and are therefore not required to be insulated against the surrounding environment. In an embodiment the enclosure comprises three input and three output contacts for each location of a distribution switch and the three contacts for connection with a further enclosure with distribution switches. Thus, the enclosure does not need to be fully equipped with distribution breakers but may contain a smaller number of distribution breakers than can be accommodated. Facing a build-up of a distribution station a plurality of distribution switches arranged in a modular system of enclosures can thus be ordered. This may be both economically advantageous as well as simplifying the structure. In an embodiment of the invention the switchboard comprises an enclosure accommodating all electrical equipment. In this embodiment the equipment is mounted conventionally with a busbar system contained in the enclosure. The enclosure contains thus all of the electrical equipment and has on the outside only contacts for incoming and outgoing cables. The entire enclosure consists in an embodiment of a transparent plastic container which allows a simple visual inspection. The enclosure is in an embodiment divisible for access and service in the workplace. In an embodiment the enclosure comprises two enclosure parts joined together with a watertight joint. The enclosure comprises in an embodiment a horizontal flange joint which is mounted with an elastic sealing on site. In an embodiment the upper part is larger than the lower part wherein the flange joint is positioned at a low level. The upper part will enclose an air pocket which if leakage occurs prevents water ingress. This is known as the diving bell effect. All cable entries are arranged in the lower part. In an embodiment the upper part comprises a collar which extends down under the flange joint and thus surrounds the lower part.

In an embodiment of the switchboard each distribution switch in the enclosure is arranged operable from outside the enclosure. In an

embodiment this operation is provided with a watertight rotary knob which is in communication with the distribution switch lever. In an embodiment the actuation is provided by including an elastic portion to the enclosure which encloses the distribution switch own control lever wherein the lever is operable through the elastic portion.

According to a first aspect of the invention the object is achieved by a low voltage switchboard for distribution of electric power to a plurality of electric power consumers, comprising an electrical equipment containing switching equipment and a plurality of circuit breakers, and an openable enclosure enclosing the electrical equipment, wherein the enclosure comprises a watertight container disposed with watertight connection means enclosing the circuit breakers.

According to an embodiment of the invention the circuit breakers comprise a main switch and a plurality of distribution switches. According to an embodiment of the invention the enclosure comprises a well with a cover arranged in parallel with the ground surface and adapted to withstand the load of a vehicle. According to an embodiment of the invention the container comprises an upper part and a lower part which are joined together by a flange joint. According to an embodiment of the invention the upper part of the container is dome-shaped and surrounding the electrical equipment whereby an increase of ground water creates an air pocket in the upper part which prevents water penetration and thus protects the electrical equipment. According to an embodiment of the invention the upper part of the container comprises an openable window allowing service and access to the enclosed electrical equipment.

According to an embodiment of the invention the electrical equipment comprises means for remote monitoring or remote control of the circuit breakers.

According to a second aspect of the invention the object is achieved with a method at distribution of low voltage electric power to a plurality of electricity consumers from a switchboard comprising an electrical equipment containing switching equipment and a plurality of circuit breakers, and an openable enclosure containing the electrical equipment, comprising protecting the circuit breakers against water penetration by providing in the enclosure a waterproof container holding the circuit breakers.

According to an embodiment of the invention the method further

comprises designing the container to comprise an upper part and a lower part, and forming the upper part cup-shaped and covering the electrical equipment whereby at container leakage and increase of ground water an air pocket is formed in the upper part of the container that prevents water penetration and thereby protecting the electrical equipment.

DESCRIPTION OF FIGURES

The invention will be further explained by description of embodiments with reference to the accompanying drawings, where

Figure 1 is a switchboard according to the invention containing a

plurality of circuit breakers and switching equipment,

Figure 2 is an encapsulated circuit breaker, Figure 3 is a common enclosure for a plurality of circuit breakers, Figure 4 is a switchboard completely contained in one for the whole of the electrical equipment surrounded container with the cover removed,

Figure 5 is a section of an electrical switchboard enclosed in a

watertight container for the entire electrical equipment with a lid containing an air pocket,

Figure 6 is an embodiment of a switchboard according to the

invention in which the enclosure contains an openable window, and Figure 7 is a detail of the switchboard of Figure 6 where a cable

closure surrounds the connection cable.

DESCRIPTION OF EMBODIMENTS

Figure 1 shows a switchboard disposed in a well 1 with a cover 2 which is dimensioned for supporting the load of a vehicle. The well forms an outer enclosure that prevents access by a third party. The well can thus be placed in pedestrian and bicycle paths, parking areas, lawns etc. Inside the well is provided a plurality of distribution switches 3 mounted on transverse mounting beams 4. In the example shown each distribution switch comprises an encapsulated circuit breaker with integrated fault current protection, and is shown as a container 10 with a switch symbol 3. The switchboard is in the example shown a three phase system and the distribution switches are interconnected by isolated connection brackets 5 in pairs of three. Each distribution circuit breakers is coupled with

waterproof connectors 6 to a three-phase power cable 7 for power distribution to different electricity consumers. Each power cable includes a cable termination 8 that splits the cable end into phases. The cable termination prevents water from penetrating into the breaker enclosure. Each distribution switch includes a lever 9 which can be operated from outside the enclosure. The waterproof container 10 contains the enclosure standard of IP67. The first digit means that the circuit breaker is dustproof. The second digit means that the circuit breaker is protected against temporary immersion in water. Other switching equipment such as connecting brackets and cable connections are also made to meet the IP code of IP67. Thus the whole switchboard positioned in the well resists both flooding of surface water and increase in groundwater. The circuit breakers are preferably of the type MCCB. In an embodiment the enclosure includes a hermetic enclosure whereby the internal environment can be arranged so that the switching equipment does not oxidize.

The well protects the electrical equipment from mechanical stress, for example from ingress of soil etc. The well also forms an outer enclosure that protects the electrical equipment against access by a third party. For water runoff the well is open at the bottom. Conveniently the bottom is provided with a drain which is connected to a surface water system. The cover of the well is provided with holes 20 for passage of surface water. The cover is also stable enough to withstand the passage of for example a car. In an embodiment the cover is placed on a wedge-shaped frame, to cooperate with the inclination of the surrounding ground. In an

embodiment the cover is lockable.

The distribution switch 3 of Figure 2 consists of a watertight container 10 of an insulating material that encloses a circuit breaker and has watertight connection means. In the example shown the encapsulated distribution switch comprise three connection means 11 for the incoming three phase power and three connection means 12 for re-transmission of the incoming electric power. The enclosure also contains three connecting means 13 for connection of an electric cable for power transmission to an electricity consumer. The connection means conducting current through the

enclosure into the distribution switch. In an embodiment the connection means consists of metal rods that penetrate the watertight container 10 in a watertight manner. At each end of these rods are arranged connecting joints or connectors for interconnection by brackets 5. To maintain enclosure rating the connecting means include not shown stocking of an elastic insulating material that is rolled over the finished joint. An example of elastic insulating material is silicone rubber. An example of connections is bolts or pins and socket.

In an embodiment the brackets 5 consist of cables and the connecting means of cable glands which watertight envelops a cable-shaped bracket. The enclosure is in this embodiment divisible or provided with an openable window. The cable is passed through the cable gland and connected to the circuit breaker after which the gland is tightened so that a watertight lead- through is accomplished. When all cables are installed the window is closed and sealed watertight with knobs screws or any other locking device. A gland comprises a strain relief for cables. A cable gland

comprises in an embodiment a screw joint for mounting in a plate. The gland is made of either metal or plastic and includes a lock nut and sealing ring for a tight seal to the plate. It protects the cable termination for mechanical stress, dirt and humidity. Inside the gland there is a rubber ring that holds the cable fixed.

The container 10 shown in Figure 3 contains a plurality of distribution switches 3. In the example shown there is room for three distribution switches. The container contains three not shown connections for incoming power at the left end. At the right end the container contains three connections 12 to transfer power. On the front in the example shown, the container contains three sets of connection means 13a, 13b and 13c for connecting an electrical cable for power distribution to an electricity consumer. According to the invention more distribution breakers may be contained in the same container as well as the container shown contains fewer than three distribution switches. An advantage of arranging a plurality of distribution switches in the same container is that the external brackets can be avoided. In this way a smaller number of connection points which must be isolated are achieved. On top of the container actuating means 14 is arranged for each distribution switch by which the distribution switch can be turned on and off. In the example shown the actuating means is designed as an elastic cover that encloses the distribution switch lever.

The inventive concept also includes a switchboard in which the entire electrical equipment is enclosed in a common container. Figure 4 shows an embodiment where a plurality of distribution switches 3 and a main switch 15 are disposed in a common container 10. In the example shown the container is openable with a not shown cover that fits into a frame 16 at the upper edge of the container. The cover consists in an embodiment of a window that may be transparent. The window closes against the frame with a sealing ring and one or more knobs so that a watertight joint is achieved.

The switchboard shown in Figure 5 includes a container 10 which

accommodates all electrical equipment. By accommodating all electrical equipment within the same enclosure the switchboard can be erected in a traditional way. Thus within the enclosure there is arranged a three-phase busbar system 21 to which each distribution switch 3 is connected. The busbar system transports the incoming current to the distribution switches. Each of the distribution switches distributes power to various electrical consumers via a waterproof connection cable 22 arranged through the container. The container is in the example shown divisible and comprises an upper part 10a and a lower part 10b. The parts are

assembled with a flange joint 17 which can be screwed or clamped with a bracket. The flange joint also includes an elastic sealing strip 18 which ensures that the container is waterproof. In an embodiment the flange joint is so arranged that the enclosure is hermetically sealed. In the example shown the upper part 10a is larger than the lower part 10b. The upper part is dome-shaped and encloses laterally the distribution switches and the switching equipment. By the cup-shape the upper part is brought to enclose an air pocket 19 which when the ground water rises will protect the electrical equipment if the flange joint should leak. Water is hindered by the air pocket to penetrate the dome-shaped upper part where all the electrical equipment is mounted. The material of the container and particularly the upper part can be metal or plastic. In an embodiment the upper part is made of a transparent plastic. The

switchboard can then be more easily inspected. In an embodiment the upper part comprises a plurality of elastic but dense ridges 23. The ridge encircles the operating means 9 of the distribution switches which then can be operated from outside the container. The cover is by its shape and elasticity of the material of choice so resilient that pressure differences on either side of the enclosure can be cancelled. In an embodiment the ridge comprises an openable window through which the operating means are accessible by opening the window.

The switchboard of Figure 6 is placed in a well 1 built up of frames in a form-stable material such as plastic or metal. The well is provided with an openable cover arranged to resist external forces that may occur. In the example shown the enclosure comprises an upper trapezoedal part 10a and a lower part 10b forming foundation for a busbar system whereupon the distribution switches 3 are mounted. A schematically shown

connection cable 22 includes an insulated cable which passes through a gland 30 and is connected to the distribution switch. The insulation may consist of rubber or plastic. The other end of the cable is provided with an end fitting consisting of a sleeve with a sealed base which is clamped on the conductor and surrounded by a shrink tube to prevent water from entering the cable. In an embodiment the end fitting comprises a cable splice. The splice includes a sleeve with a common dense bottom in the middle. The connecting cable and the connected cable are inserted into each end of the sleeve which is clamped over the respective conductor and sealed with shrink tubing. The upper part of the enclosure contains one or a plurality of openable windows 25. In the example shown the windows are provided with hinges 26 and a locking device 27 which can be a knob or a screw joint. Between the window and the frame there is a seal which when the window is closed is compressed and creates a completely dense upper part of the casing. The upper part is held in place by a catching stripe or a system of hooks 29 which is held tensioned by eccentric locks 28.

The cable gland can be closer viewed in Figure 7 which is a detail of the encircled area shown in Figure 6. The cable gland comprises in the shown example a sleeve of plastic or other form-stable material. The connection against the lower part of the enclosure is made with a locknut and a seal ring 31. In the example the upper part 10a comprises a flange-shaped portion which abuts against the lower part with a sealing strip 18. The upper part further comprises a skirt-shaped portion 32 which abuts against the flange and extends down below the sealing strip and along the edge portion of the lower part. This configuration is advantageous in the event of leakage in the flange joint. By this design of the upper part an air pocket is trapped that prevents water to penetrate the upper part. Since the lower end of the skirt is on the same level as the lower portion of the lower part also the gland will be positioned inside the air pocket. Should leakage occur the contained electrical equipment is thus protected by the air pocket.

The enclosure is robust enough to withstand normal handling during assembly on site etc. The enclosure may have external terminals for a busbar system, connecting terminals for an outer incoming cable and a control unit for the closing and opening of the MCCB. All electrical equipment is protected and finger proof. The busbar system is designed for a load current of 400 A to 630 A. A switchboard according to the invention provides a flexible solution to the distribution of electric power. The enclosed equipment can easily be exchanged, expanded or replaced. Because of its ability to withstand external influences the solution also offers a good electricity supply and is thus society friendly.

Although advantageous the invention is not restricted to the embodiments shown but also contains development forms made by a person skilled in the art. It thus includes for example that the enclosure shown can also be placed above ground.

Claims

1. Low voltage switchboard for distribution of electric power to a

plurality of electric power consumers, comprising an electrical equipment containing switching equipment (11, 12, 13, 21, 22) and a plurality of circuit breakers (3, 15), and an openable enclosure (1) enclosing the electrical equipment, c h a r a c t e r i z e d i n that the enclosure comprises a watertight container (10) disposed with watertight connection means (11, 12, 13, 22) enclosing the circuit breakers.

2. Switchboard according to claim 1, wherein the circuit breakers

comprise a main switch (15) and a plurality of distribution switches (3).

3. Switchboard according to claim 1 or 2, wherein the enclosure

comprises a well (1) with a cover (2) arranged parallel to the ground surface and adapted to withstand the load of a vehicle.

4. Switchboard according to any of the previous claims, wherein the container (10) comprises an upper part (10a) and a lower part (10b) which are joined together by a flange joint (17).

5. Switchboard according to claim 4, wherein the upper part (10a) is dome-shaped and surrounding the electrical equipment whereby an increase of ground water creates an air pocket (19) in the upper part which prevents water penetration and thus protects the enclosed electrical equipment.

6. Switchboard according to any one of claims 4 or 5, wherein the upper part (10a) comprises an openable window (25) allowing service and access to the enclosed electrical equipment.

7. Switchboard according to any of the previous claims, wherein the electrical equipment comprises means for remote monitoring or remote control of the circuit breakers.

8. Method at distribution of low voltage electric power to a plurality of electricity consumers from a switchboard comprising an electrical equipment containing switching equipment (11, 12, 13, 21, 22) and a plurality of circuit breakers (3, 15), and an openable enclosure (1) containing the electrical equipment, c h a r a c t e r i z e d b y

protecting the circuit breakers against water penetration by providing in the enclosure a waterproof container (10) holding the circuit breakers.

9. Method of claim 8, wherein the method further comprises designing the container (10) to comprise an upper part (10a) and a lower part (10b), and forming the upper part cup-shaped and covering the electrical equipment whereby at container leakage and increase of ground water an air pocket (19) is formed in the upper part that prevents water penetration and thereby protecting the electrical equipment.

10. Use of a switchboard according to any of claims 1-7 or a method

according to claim 8 or 9, for the distribution of electric power to a plurality of electricity consumers in a mall or in a property.