GB2034987A - Distribution of electric power - Google Patents

Abstract

A main distribution station for the distribution of electric power includes a high voltage part (5) a medium voltage part (6) and at least one transformer (7, 8) connected between the parts. Each on part comprises multiphase feed sectors mounted so that they may be arranged together with corresponding additional feed sectors each forming a complete feed ring, wherein the high voltage feed ring is positioned axially above the medium voltage feed ring while the transformers are installed at the side of these rings. Apart from the transformers the entire main distribution station may be installed within a two storeyed tower in which the medium voltage part (6) is installed within the lower storey while the high voltage part (5) is located in the upper storey. A substation for the distribution of electric energy may include only a medium voltage part supplied by means of a cable, rather than by a transformer. <IMAGE>

Description

SPECIFICATION A main station and substation for the distribution of electric energy.

The invention relates to a main distribution station for the distribution of electric energy including a high voltage part, a medium voltage part and at least one high voltage transformer connected between said parts. The invention relates furthermore to a substation for the distribution of electric energy including only a medium voltage part to which the medium voltage is supplied by means of a cable.

Main distribution stations of the type mentioned above are constructed in general as out-door stations when a large energy concentration is concerned in which in view of the existing double line of the high voltage distribution network there are usually connected four incoming high voltage lines to a double rail system by means of disconnector switches and power switches. This double rail system has been connected to two orthreetransfor- mers feeding in their turn two or more medium voltage installations. The medium voltage installation is usually also constructed as a double rail system.

In view of the high voltage and having regard to the future supply of current one is inclined to construck the high voltage part of such a main distribution station for a much larger energy concentration than is desirable initially. A corresponding medium voltage concentration is undesirable in view of the distribution thereof. Consequently there originates moreover an unfavourable HV/MV cost ratio. Upon increase of the energy consumption there will then gradually be higher investment costs for the MV network than for the HV part. This implies however that within the first years a large part of the installed HV construction is used uneconomically and will only be utilised gradually more economically upon expansion of the MV network. One would very willingly avoid this initial overinvestment if there would exist appropriate other solutions for that purpose.

The increase of the energy consumption due to the population growth and urban expansion is still of such a degree that also due to the relatively large distance between main distribution stations a MV transport cable will soon reach its load limit whereupon a parallel cable has to be provided. Where finally a HV injection of energy will required this implies that the investment costs are made for means that will only be used for a short while. This is a possibility of expansion which one will accept in combination with the at that time relatively lower HV investment costs.

Having regard to the steadily increasing intermeshing due to the increase of energy consumption there is an increasing need of more simple main distribution stations and substations respectively by means of which HV energy may be injected in the medium voltage network at more locations than possible uptil now. As an illustration the following may be remarked: The energy injection half way a 10 KV cable instead of at the end thereof inplies that the maximum energy transport capability of the cable will in general be doubled.

However, the energy injection by means of the presently used main distribution stations at much more locations than usual at present is becoming more and more impossible in view of their large dimensions of sometimes even half a hectare or more. For municipalities that is the more prejudicial because the need of additional main distribution stations is increasing especially at such places.

The said large dimensions of the main distribution stations are required among others in view of the air insulation being economically the most suitable for high voltages in general 110 KV and more and the consequently relatively large parts such as power switches, coupling switches and disconnector switches of the HV part. The large surface area of the main distribution stations is also inspired by the double line and the double rail system usual in The Netherlands. The present HV distribution network has been constructed as a double line network almost everywhere due to, at least partially, the former function thereof as a coupling network. This means that in the main distribution stations usually four HV lines have been connected to a double rail system.Like it has been already remarked above to this double rail system there are connected two or three transformers feeding in their turn two or more MV installations which MV installations are usually also constructed as a double rail system. A limit at which the change over to the double rail system is made lies generally at about 10 MVA which limit is usually soon reached in the towns so that one becomes dependent on a double rail system also in these instances.

There are many good reasons for the application of double rail systems such as a load distribution of the stations that is as favourable as possible; the possibility of several voltage levels when in operation; expansion and maintainance without interruption of operation; a limitation of the short circuit power and afacilitation of the localising of earth faults. If however other solutions would be available for the aforesaid objects the construction engineers will inclined to drop the double rail system.

The present invention now provides a main distribution station and a substation of the type mentioned above in which there has been accounted for the ensemble of the above mentioned drawbacks of the existing means and the requirements as regards the easy and gradual expansion with respect to the HV installation as well as to the MV installation.

The main distribution station according to the invention is characterized in that the HV part as well as the MV part comprise at least one multiphase feed sector mounted in such a manner that it may be arranged together with corresponding additional feed sectors to form a complete feed ring, wherein the HV feed ring is positioned axially above the MV feed ring while the HV transformer is installed at the side of these rings, each one of said HV feed sectors consisting of a HV power switch, two rail sections to be connected to each other by means of the power switch and both extending over part of said feed ring, HV disconnector switches by means of which the two rail sections may be connected to the HV feed line and to the HV winding of the transformer, respectively, means for connecting the ends of the rail sections not connected to the HV power switch to corresponding ends of rail sections of other adjacent feed sectors in the feed ring, and said MV feed sector consisting of a rail section curved along the circumference part of a circle, a MV feed power switch capable of connecting the rail section to the MV winding of the transformer and to a feeding cable, respectively, MV outgoing power switches, each one of which being capable of connecting the rail section to an outgoing MV cable, coupling means for connecting the existing rail section to optional additional rail sections spatially adjoining the existing rail section in the MV feed ring to be formed.

In a preferred embodiment of the main distribution station according to the invention an end of the MV rail section is connected to the MV feed power switch while the MV outgoing power switches are connected uniformly distributed to the rail sections and each one of the MV power switches is installed outside the MV feed ring within an associated ring sector adjoining the M rail section.

Of one or more additional MV rail section(s) the free end of the existing rail section (s) not connected to the MV feed power switch is connected by means of a coupling power switch or disconnector switch to the spatially adjoining end of the additional MV rail section the other end of which is connected to the associated MV feed vacuum power switch and lor the side of the MV feed power switch of the existing rail section connected to the HV transformer or the cable, respectively, is connected to the corresponding side of a MV feed power switch of the at this end of the existing rail section spatially adjoining rail section the other end of which may be connected by means of a vacuum coupling switch to an additional spatially adjoining MV rail section.

A complete MV feed ring according to the invention consists of a plurality of for instance four rail sections curved along a part of a circle wherein the connections between two ends facing each other in the ring and belonging to two adjacent rail sections comprise alternately a coupling power switch or disconnector switch and two MV feed power switches arranged in series, respectively, the common junction of which is connected to the high voltage trans formerorthe cable, respectively. The medium voltage feed ring is furthermore provided with a plurality of MV earth switches for earthing each one of the rail sections and each one of the outgoing MV cables, respectively.

Apart from the transformers the entire main dis tribution station according to the invention having a same capacity as the present existing outdoor main distribution stations may be installed within a two storeyed tower or colomn having a diameter of about 6 m and a height of about 10 m. The MV part is then installed within the first storey on a level with the ground or entirely or partially dug in in view of the incoming and outgoing cables or limitations with respect to the height of buildings, while the high vol tage part is located at the second storey above the medium voltage part. The foundation may consist of a single pillar or of a steel plate frame continuing in the MV part of the house and carrying the floor of the second storey while the medium voltage ring is suspended from this frame within the first storey.The high voltage part may be located on a level with the high voltage supply lines for the stations of the country part of the high voltage network. In the towns where one has to apply high voltage cables large cellars are avoided in view of the radius of curvature of the high voltage cable. The required building ground in the order of magnitude of. 20 x 10 m including two transformers is very little when compared with the above mentioned usual main distribution stations having air lines. This is of very importance for at present high voltage distribution stations will have to be situated within cities having a high building density. The building may entirely be constructed in a factory out of prefabricated elements and installation parts.The installation parts such as rail sections and switches may however also easily be supplemented at any desired time thus creating the possibility of a gradually growth of both the high voltage part and the medium voltage part.

The building materials are reduced to a minimum whereas such a main distribution station shaped as a small colomn will hardly be experienced visually as out of place within the landscape or within the towns either. At a simiiar capacity of 40 MW the costs of a main distribution station according to the present invention will be considerably lower than for an above mentioned main distribution station insulated by the atmospheric air.

The inlet means for the lines and connections to the high voltage transformers may be constructed as arms integrated with the building, said arms carrying insulators, the same also applying to the inlet means to the high voltage lines. The station serves thereby also as a pylon.

Instead of the usual double rail system now a rail installation is applied offering like the double rail system maximum service capabilities. There will be no need for the rail to transport more than only 75% of the maximum transformer capacity, that is in case of the open or incomplete ring. In case of a break down in anyone of the components the power supply may always be continued by means of the remaining part of the ring. Power switches being most of all subiect to inspection may easily be taken part thanks to the arrangement thereof within a circle or ring sector outside the feed ring without blocking any line or transformer. Thanks to the arrangement within an outwardly enlarging circle or ring sector the length of the rail is not determined anymore by the broadest component of the field as for instance a vacuum switch. The length of the rail may thereby kept as small as possible. Moreover an expansion of the main distribution station to com plete ring installations is not an immediate neces sity. Like a single rail will suffice in the usual stations for capacities of less than 10 MVA in the station according to the present invention only a part of each ring may be installed initially. In this connection it should be remarked that an extension of the ring is possible while the station is in operation.

In the existing main distribution stations in which the insulation is provided by atmospheric air one could indeed also gradually expand the high voltage part with increasing energy consumption but in that case a much larger surface area should be available from the beginning onward in view of the maximum expansion to be expected.

In the main distribution station according to the present invention the arrangement of the installation parts is furthermore such that with respect to heat generation most heavily loaded parts such as rails and feed switches may be forcibly cooled very easily by means of a single cooling unit thus allowing for an over-loading of 300. Due to the annular shape having a small diameter of about 120 cm the rails are moreover extremely short so that there will occur only a slight heat generation. The MV installation will comprise a minimum of inflammable material if vacuum power switches are utilized therein and if the components capable of ruining the installation due to their explosive character, such as gas producing switches and end connections for wet cables are kept outside the installation and no oil switches are used therein.The rail sections and the vacuum switches connected thereto for the MS part will preferably be imbedded in an insulating material without any air gap. The outgoing fields of the medium voltage part may be connected to the medium voltage rail sections in fixed orwithdrawable manner without any air gap.

All operating means for the vacuum load switches for earthing the rail sections and the cables will preferably be coupled with each of the associated vacuum power switches in such a manner that before the earth load switch may be switched off the associated vacuum power switch has to be switched off completely and vice versa. This may simply be attained by controlling the switches by means of the same operating mechanism. All further required installation parts such as current transformers, capacitive voltage dividers for voltage indication, the connections to the cable end connections may be installed below or close by the side of the rail sections and the whole unit may be housed within a steel plate cupboard having the shape of a desk in which blind diagrams, reading indicators, amperemeters and volt meters are included. Thus a very compact distribution station is obtained.

Outside the house transformers are installed mounted on rails for very simple transportation this being particularly advantageous for the replacement and for the load adaptation.

The above mentioned problems entailed by the existing main distribution stations are now solved by the main distribution station according to the invention. By means of compact main distribution station according to the present invention there may easily be injected energy into an existing MV network at many more points than possible at present. In case of closed feed circuits the main distribution station according to the invention provides for an adequate replacement of the double rail system while both the medium voltage part and the HV part allow for a gradual extension whereby initial large investment costs becomes superfluous.

The invention provides also a substation for the distribution of medium voltage not fed by a high voltage part including a transformer but from a medium voltage cable connected elsewhere to a main distribution station or to another substation.

These substations only comprise the medium voltage part of the main distribution stations according to the present invention. Such substations allow for a MV energy injection at locations where as yet no need exists for an injection from a high voltage line.

If the energy consumption surpasses a certain limit such a substation may very easily be converted into a main distribution station. To that effect one only needs to construct the second storey and to install transformers. In view of the small surface area to be reserved one may easily account for such a conversion from the beginning onward.

The invention will now be elucidated in further detail with reference to the drawings in which embodiments have been despicted.

Fig. 1 shows a diagrammatrical vertical cross section partly in side elevation of a main distribution station according to the present invention; Fig. 2 shows diagrammatically a cross section partially in side elevation through the high voltage part of the main distribution station according to the present invention; Fig. 3 shows a top view of a partially installed high voltage part, a so-called T-installation of a main distribution station according to the present invention; Fig. 4 shows a completely closed feed ring corres ponging to Fig. 3 of a high voltage part, a so-called H-installation; Fig. 5 shows a top view of the medium voltage part of a main distribution station according to the present invention; Figs. 6 to 9 inclusive show extension possibilities of the medium voltage part of a main distribution station according to the invention;; Fig. 10 shows a partial vertical cross section through the medium voltage part along the line X-X in Fig. 5; Fig. 11 shows partially in cross section a substation according to the present invention.

In the figures to be discussed below the same reference numerals indicate the same parts of the main distribution station and the substation of the present invention.

In Fig. 1 showing a cross section and a partial side elevation of the main distribution station according to the invention there has been shown a columnar house 1 divided into two storeys by means of a floor 2 supported by a pillar or frame 3 which pillar or frame may constitute as such the foundation of the main distribution station but may also be erected on a separate foundation. The house is covered with a roof 4. The house 1 has furthermore been provided with not shown doors, windows and stairs or ladders along the side walls. At a capacity of 40 MVA the breadth of this house amounts to about 6 m at a height of about 10 m.

In the second storey the high voltage part generally indicated by the reference numeral 5 has been mounted on the floor 2 whereas the medium voltage part 6 has been mounted in the first storey for instance on a level with the ground. In this instance this medium voltage part 6 has been indicated as a complete ring such only being the case in the final situation of the station, said ring being suspended from the frame 3 or being supported by the bottom of the house 1.

Outside the house there have been indicated diagrammatically two transformers 7 and 8.

Fig. 2 shows a cross section through the high voltage part 5 of the house and a top view of the transformers 7 and 8. Supporting arms 9 and 10 have been provided on the side wall of the house said arms serving for the inlet of the high voltage lines 11 and 12, which lines have been constructed as air lines. These supporting arms 9 and 10 may be integrated with the wall of the house. The three phase high voltage lines 11 and 12 have been fastened to insulators 13 and 14 from which a connection runs to the suspension insulators 15 and 16 suspended from the arms 9 and 10. The said suspension insulators are bushing insulators through which the high voltage is supplied to the high voltage part 5 by means of inlet conductors 17 and 18.

In this completed main distribution station the high voltage part 5 comprises straight three phase rail sections 19 to 22 inclusive that be connected to each other by means of high voltage power switches 23 to 26 inclusive that have been installed at the corners of a rectangle. Each one of the rail sections 19 to 22 consists of two aligned rail parts which may also be connected to each other so that there are eight half rail parts in total. The connections between the three phase inlet conductor 17 and 18 and the three phase rail sections 19 and/or 21, respectively, and between the rail parts of each of said sections are brought about by three way high voltage disconnector switches 27 and 29 only indicated diagrammatically at the junction between the inlet conductors, the rail sections and the rail parts.Similar three way high voltage disconnector switches 28 and 30 may connect the rail sections 20 and 22 or the rail parts thereof to the primary high voltage windings of the transformers 7 and 8 installed outside the house 1.

As the high voltage power switches there may be used SF6 filled switches.

In the station shown in Fig. 1 the connection between the three way disconnector switches 28 and 29 and the primary windings of the high voltage transformers 7 and 8 is provided by imbedded conductors indicated bythe reference numerals 31 and 32. This connection may however also be provided by means of arms corresponding to the arms 9 and 10 by means of which the high voltage lines 11 and 12 have been connected. These arms not shown in the figures may likewise be integrated with the house 5 and will thereby extend in a direction perpendicular to the direction of the shown arms 9 and 10 by means of which the air lines of the HS network have have connected.

In Figs. 1 and 2 the high voltage power switches 23 to 26 inclusive have only been indicated diagram matically, which switches comprise an operating mechanism located in the vertical houses 33 and 34 in Fig. 1. Within the bottom portion of these houses 33 and 34 there have been provided the switching elements for interrupting the connections between the four rail sections.

The current supply in the high voltage part leads from the high voltage lines 11 and 12 via the inlet conductors 17 and 18, the three way disconnector switches 27 and 29 coupled therewith to the two rail sections 19 and 21. The ends of these rail sections i.e. the outer ends of the rail parts of each section end in high voltage power power switches 23 and 24; and 25 and 26 respectively. The other sides of these power switches have been connectedtothe adjacent parts of the rail sections 20 and 22. These rail sections may be connected by means of three way disconnector switches 28 and 30 to the imbedded conductors 31 and 32 leading to the primary windings of the high voltage transformers 7 and 8, respectively.

Figs. 3 and 4 show expansion possibilities of the high voltage part in a. main distribution station according to the present invention.

Fig. 3 shows an embodiment in which one transformer may suffice provisionally. This is a so-called T-installation. In both the arms 9 and 10 there end again the voltage lines 11 and 12 these lines being suspended from the insulators 13 and 14, respectively. By means of the not shown suspended bushing insulators and the likewise not shown inlet con ductorsthe high voltage reaches the diagrammatically shown three way disconnector switches 27 and 29 which in this incomplete embodiment may provide a connection to the rail parts of the half rail sections 19 and 21. The inlet conductors 17 and 18 as well as the rail sections 19,20 and 21 have been housed in gas filled cases but may also be insulated in another way. The existing parts of the rail sections 19 and 21 again terminate in power switches 24 and 25.Between these power switches there extends a complete rail section 20 in the middle of which there has again been provided a three way disconnector switch at 28 capable of connecting the rail sections to the supply conductors leading to the transformer 7. In the present case this takes place by means of an arm 35 integrated with the building and having the same construction as the arms 9 and 10. From the bottom side of this arm 35 there have been suspended bushing insulators from which the conductors run to the primary winding of the high voltage transformer.

As indicated above Fig. 4 shows a high voltage part including a complete feed ring, a so-called H-installation. In this instance the rail section 22, like the rail section 20 ih Fig. 3, is connected to the prim an/ winding of the likewise not shown second high voltage transformer by means of an arm 36 and bushing insulators and the conductors running there through The other parts have been indicated by the same reference numerals as in the preceding figures.

A ring installation offers of course the maximum of possibilities as regards the operation. In case of a disturbance in anyone of the components the energy supply may always take place by way of the remain ing part of the ring. The power switch frequently being subject to inspection in view of the disconnec tion of short circuit currents may be taken apart without blocking any line or transformer. Moreover the installation has been designed such that there may be accounted for the fact that switches of a bet tertipe may be installed afterwards.

Fig. 5 shows a top view of a medium voltage part according to the invention. In the center there is again present the colomn or frame 3 from which the entire medium voltage part may be suspended. By means of the reference numerals 37,38,39 and 40 there have indicated the imbedded MV rail sections.

These sections have been entirely imbedded in an insulating material, vide Fig. 10 showing a vertical cross section along the line X-X in Fig. 5. In Fig. 10 right hand part the three phases R, S and T of the medium voltage rails have been indicated all three of which have been imbedded in the insulated material 50. To the rail section 37 in Fig. 5 in clockwise direction starting from the left hand lower end to the right hand upper end there have been connected a feed power switch 41, five outgoing power switches 42 to 46 inclusive leading to outgoing cables and a coupling switch 47. By way of the feed switch 41 current is supplied to the rail section 37 from the secondary low voltage winding of one of the transformers, which current may be supplied to the outgoing cables by means of each one of the outgoing switches 42 to 46 inclusive of the several medium voltage fields.The coupling switch 47 provides the possibility to connect the rail sections 37 and 40 to each other. The other rail sections 38,39 and 40 have been constructed in the same manner as the rail section 37 with the difference however that the current direction in the rail sections 38 and 40 runs opposite to the direction in the sections 37 and 39 assuming anyway a uniform loading of the ring. The sections 37 and 38 are connected to the one transformer by means of their feed switch 41 while the rail sections 39 and 40 are connected to the other transformer by way of their feed switch 41. In each end of the different switches turned away from the rail sections there has been provided an only diagrammatically indicated tube mechanism 59 by means of which each switch may be operated.By means of the same tube mechanism there may also be operated an earth load switch for earthing either one of the rail sections or the associated outgoing cable. It is preferred that the different switches consist of vacuum switches.

In Figs. 6, 7,8 and 9 there have been indicated expansion possibilities of the MV part of a main distribution station or a substation according to the invention, respectively. Initially one may start with one rail section according to the embodiment of Fig.

6 in which the same reference numerals indicate the same parts as in Fig. 5. In such a situation the feeding takes place by means of a feeding cable. In order to create the possibility to earth the feeding cable without simultaneously earthing the rail, one of the switches 42 to 46, inclusive is used as the feed switch. The feed switch 41 may then be omitted initially. In Fig. 6 there have also been shown earth load switches by means of which the rail section 37 and the different cables down the outgoing vacuum switches 42 to 46 inclusive may be earthed. These earth switches consist of vacuum load switches and have been indicated in the figures by means of the reference numeral 48. In Fig. 7 there has been instal led a second rail section 40 requiring in the represent case a second feeding cable to which again one of the right hand vacuum switches 42 to 46 inclusive is connected.Upon disappearance of one of the feedings the pertaining rail section may be fed by closing the coupling switch 47 by way of the not disturbed rail section.

Further extension'possibilities have been indicated in Figs. 8 and 9. For clearness sake most of the reference numerals at the several vacuum switches have been omitted in Figs. 8 and 9.

In Fig. 8 there has been shown a further extension by means of a third rail section 39. In this situation a transformer provides the feeding to which effect both the right hand vacuum feed switches 41 are connected together to said transformer. For guaranteeing an undisturbed feeding for instance upon this disappearance of the transformer feed the existing cable feedings of the rail sections 37 and 40 may be maintained. Optionally an outgoing field may also be used for the rail section 39 in order to provide this rail section with cable feeding.

Finally Fig. 9 shows the completed MV part of a main distribution station or substation according to the invention, respectively.

Thereby a second transformer has been installed so that the entire installation may be fed by means of transformers. The feeding fields used for cable feeding may then again serve as outgoing fields.

From these figures the gradually expansion possibility of the MV part in a main distribution station according to the invention is clearly appa rent the same however also apply to a substation according to the invention. The medium voltage feed ring consisting of rail sections 37 to 40 inclusive may gradually be completed dependent on the increasing energy need within an area to be fed. Initially only one rail section will suffice and the coupling switch 47 as well as the feed switch 41 may be omitted.

Upon increase of the energy consumption one will connect a second feeding cable to the distribution station and install a further rail section, in Fig. 7 the rail section 40. It goes without saying that the extension is not limited to the form despicted in Fig. 7.

Instead of the rail section 40 there may also be installed a rail section 38 as a second section, vide Fig. 9.

In this case both the sections 37 and 38 may be fed either by a transformer or by way of cables. Fig. 8 shows the next step of the extension of the medium voltage part afterthe step shown in Fig. 7 while Fig. 9 shows the final completely installed medium voltage installation.

For the medium voltage part it applies that due to the very small rail length the heat generation is at a minimum. The rail sections 37 to 40, inclusive, may together with the connection and coupling means thereof completely be imbedded in a factory. The ringlike arrangement makes a forced cooling very well feasible. The coupling switches 47 between two adjacent rail sections within the feed ring as well as the other vacuum switches serve for safeguarding the rail but also as a protective switch for the transformer. These coupling switches as well as the rails need not carry more current than 75% of the max imum transformer load. It will be selfevident that all vacuum power switches are constructed as three phase switches in this case too.

Fig. 10 shows the arrangement of the vacuum power switches and load switches for earthing the cables and the rail sections of the medium voltage part in further detail. The figure represent a cross section through an outgoing field, that is to say the outgoing field including the switch 44 in Fig. SAt the right hand side this vacuum switch 44 is connected to a phase of the rail section 37. The rail 49 of this rail section has been imbedded completely in an insulation material 50 which as is also evident from Fig. 5 has been provided with a hollow part 51 projecting in left hand direction in which there will fit a boxlike end of a house 52 of insulating material. Within this house 52 there has been inserted the outgoing vacuum power switch 44. A current conductor 53 runs from this power switch in right hand direction through the hollow part 51 into an opening in the rail 49.Between the inner wall of the hollow part 51 and the outer wall of the necklike right hand end of the house 52 there has been provided a sealing material.

The house 52 is closed on the left hand side by a second house 54 of insulating material in which the operating means for the vacuum switch 44 and the earth switch 48 has been housed. The movable current conductor 64 of the switch 44 may move one of the switch contacts for connecting and disconnecting the switch 44. On the current conductor 64 the connecting means 55 for the outgoing cable 56 of a field have been indicated. This cable is likewise connected to the left hand movable current conductor 65 of the earth switch 48 with the aid of connecting means 57. The right hand current conductor of this earth switch has been connected to the earth rail 58.

The left hand movable current conductor 65 of the switch 48 is also connected to the operating means in the house 54. The operating means have been coupled to a tube mechanism 59 which may be changed over by means of a selector knob 60. By moving the selector knob in axial direction either the vacuum switch 44 or the vacuum switch 48 may be operated so that either the cable 56 is connected to the rail 49 or the cable 56 is earthed. Operating meansforthe alternate operation of the two vacuum switches may furthermore be realized in a very simple manner by means of this tube mechanism thus providing the necessary mechanical locking between the power switch and the earth switch in a simple way.

In Fig. 10 the vacuum feed power switches and the vacuum load earth switches for the rails of the phases S and T of the same field have only been indicated diagrammatically. It will be evident that the construction thereof corresponds to the embodi ments shown in cross section in Fig. 10.

In Fig. 10 there have likewise been shown the sus pension means for the rails and the vacuum switches as well asthe operating meansforthevac- uum switches. The whole construction has been housed in a desk 61, an elevated part 62 of which may for instance be used for housing amperemeters and voltmeters 63 as well as signalling means. For each of the rail sections 37 to 40 inclusive there may be applied a desk having a curvature running along the rail section.

As will be apparent from Fig. 10 but also from Fig.

5 the rails may be kept very short because the vacuum switches are connected to these rails by means of the narrow ends thereof. That is why a shortening of the rail length is only possible when employing a circular feed rail having the fields placed on the outside. The part of the vacuum switches having a greater width are at a greater distance from the rails. The taking apart of the switch may very easily be carried out by pulling the switch out of the rails.

In Fig. 11 there has been shown a cross section of a substation according to the invention. This substation comprises only the first storey including the parts housed therein ofthe above described main distribution station. An important advantage of a substation according to the present invention is that it may be supplemented very easilyto form a main distribution station at a later date. To that effect only the frame 3 only shown in outline in Fig. 11 needs extension to the higher part. Onto this frame there has to be constructed a floor on which the high voltage part will then be installed. The house of course will also be made higher. The current supply to the high voltage part may then be carried out by means of an air line or also by means of a high voltage cable.In the latter case additional room for the transformers will not be acquired at all because the house is only made higher.

The substation comprises again a house 1 of which the foundation has been shown in the drawing as well as the rooms in which the cable end connections 62 for the different fields are present. The medium voltage part 6 has furthermore be constructed in the same manner as represented in the Figs. to 10 inclusive. The substation according to Fig. 11 may also be dug in into the ground partially or entirely. This may for instance be of advantage if an insufficient height is available or admissable for the expansion to a complete main distribution station built on a level with the ground.

The time at which one will convert a substation into a main distribution station is dependent on economical aspects determined by the growth. With regard to the presently known main distrbution stations one will go on with the expansion of the investment in the medium voltage part for a longer time in which case the initial capacity of the HV part of the main distribution station will be very high.

When starting fromthe substation according to the present invention as has been shown in Fig. 11 one will be much more inclined to convert such a substation into a main distribution station where the invention also provides for an adapted HV part. Neither the main distribution station nor the substation need to be built initiaily atthe full capacity thereof. The MV feeding cables for the substation may then be used as outgoing cables for instance as ring cables for the network stations. These cables may also be put into service for MV support points from the then created main distribution station. The vacuum switches of the then eliminated feeding cables may then again be used as such for the outgoing cables.

The invention being thus described it will be obvi ous that the same is not restricted to the embodi ments represented and discussed above without modifications and variations thereof are possible without departure from the spirit and the scope of the invention.

Claims (22)

1. A main distribution station including a high voltage part (HV) and a medium voltage part (MV) and at least a high voltage transformer connected between said parts, characterized in that the HV-part as well as the MV-part comprise at least one mul tiphasefeed sector mounted in such a mannerthat it may be arranged together with corresponding additional feed sectors to form a complete feed ring wherein the HV-feed ring is positioned axially above the MV-feed ring while the high voltage transformer is installed at the side of these rings, each one of said HV-feed sectors consisting of a HV-power switch, two rail sections to be connected to each other by means of the power switch and both extending over part of said feed ring, HV-disconnector switches by means of which the two rail sections may be connected to the HV-feed line and to the HV-winding of the transformer, respectively, means for connecting the ends of the rail sections not connected to the HV-power switch to corresponding ends of rail sections of other adjacent feed sectors in the feed ring, and said MV-feed sector consisting of a rail section curved along a circumference part of a circle, a MV-feed power switch capable of connecting the rail section to the MV-winding of the transformer or to a feeding cable, respectively, MV-outgoing power switches each one of which being capable of connecting the rail section to an outgoing MV-cable, coupling means for connecting the existing rail section to optional additional rail sections spatially adjoining the existing rail section in the MV-feed ring to be formed.

2. The main distribution station of claim 1 provided with a number of feed sectors, characterized in that, the HV-disconnector switch is a three way switch by means of which the HV-feed line and the HV-winding of the transformer, respectively, may be connected to one of the parts of a rail sector, facing each other or to both said parts and by means of which both said parts may be connected to each other.

3. The main distribution station of claim 1 or 2, characterized in that an end of the MV-rail section is connected to the MV-feed power switch and that the MV-outgoing power switches are connected uniformly distributed to the MV-rail section while each one of the MV-power switches is installed outside the MV-feed ring within an associated ring sector adjoining the MV-rail section.

4. The main distribution station of claim 1, 2 or3, characterized by a plurality of MV-earth load switches for earthing each one of the MV-rail sections and each one of the outgoing MV-cables, respectively.

5. The main distribution station of claim 3, characterized in that the free end of an existing MV-rail section(s) not connected to the MV-feed power switch of one or more additional MV-rail section(s) is connected by means of a coupling power switch to the spatially adjoining end of the additional MV-rail section the other end of which is connected to the associated MV-feed power switch and/orthe side of the MV-feed power switch of the existing MV-rail section connected to the HV-transformer or the cable, respectively, is connected to the corresponding side of a MV-feed power switch - of the at this end of the existing MV-rail section spatially adjoining rail section, the other end of which may be connected by means of a coupling power switch to an additional spatially adjoining MV-rail section.

6. The main distribution station of claim 5, characterized in that the additional MV-feed power switches and the coupling power switch are installed within an external ring sector adjacent to the rail section.

7. The main distribution station of anyone of the preceding claims, characterized in that all rail sections and power switches of the MV-part have been embedded in an insulating material.

8. The main distribution station of anyone of the preceding claims, characterized in that all said MV-switches are vacuum switches.

9. The main distribution station of anyone of the preceding claims, characterized in that a complete HV-feed ring consists of four HV-power switches installed atthe corners of a rectangle, said switches being connected to each other by means of straight rail sections and that the HV-disconnector switches are connected to the middle portions of said rail sections.

10. The main distribution station of anyone of the preceding claims, characterized in that a complete MV-feed ring consists of a plurality of rail sections curved along a circumference part of a circle wherein the connection between two ends facing each other in the ring and belonging to two MS-rail sections adjacent to each other in the ring comprises alternately a coupling power switch or two MV-feed power switches arranged in series, respectively, the common junction of which is connected to the HVtransformer.

11. The main distribution station of anyone of the preceding claims characterized in that the high voltage part and the medium voltage part are located within a tower-like two-storeyed house in which the high voltage part is installed within the second storey and the medium voltage part is installed within the first storey, both said parts being supported by a central frame mounted axially with respect to the feed rings within the house, said frame carrying the floor of the second storey and serving as the suspension for the MV-feed ring.

12. A substation for the distribution of medium voltage characterized by at least one multiphase feed sector being installed in such a way that it may be arranged together with corresponding additional feed sectors to form a complete feed ring in which each sector consists of a rail section curved along the circumference part of the circle; a feed power switch capable of connecting the rail section to a MV-feed cable; outgoing power switches each of which being capable of connecting the rail section to an outgoing field; coupling means for connecting the existing rail section to additional rail sections spatially adjoining the existing rail section in the feed ring to be formed.

13. The substation of claim 12 characterized in that an end of the rail section is connected to the feed power switch and that the outgoing power switches are connected in a uniform distribution to the rail section, each one of the said power switches being installed outside the feed ring within an associated ring sector adjoining the rail section.

14. The substation of claim 12 or 13 characterized by a plurality of earth load switches for earthing each one of the rail sections and each one of the outgoing cables, respectively.

15. The substation of claim 15 characterized in that the free end of the existing rail section(s) not connected to the feed power switch of one or more additional rail section(s) is connected by means of a coupling power switch to the spatially adjoining end of the additional section the other end of which is connected to the associated feed power switch and/or the side of the feed power switch of the existing rail section connected to the MV-feed cable is connected to the corresponding side of the feed power switch of the at this end of the rail section spatially adjoining rail section, the other end of which may be connected by means of a coupling power switch to an additional spatially adjoining rail section.

16. The substation of claim 15 characterized in that the additional feed power switches and the coupling power switches are installed within an external ring sector adjacent to the rail section.

17. The substation of anyone of claims 12-16 characterized in that all rail sections and switches have been imbedded in an insulating material.

18. The substation of anyone of claims 12-17 characterized in that all said switches are vacuum switches.

19. The substation of anyone of claims 12-78, characterised in that a complete feed ring consists of a plurality of rail sections curved along the circumference part of a circle wherein the connection between two ends facing each other in the ring and belonging to adjacent rail sections comprises alter namely a coupling power switch and two feed power switches arranged in series the common junction of which is connected to the MV-feed cable

20. The substation of anyone of claims 12-19 characterized in that the feed ring is-installed within a circular house in which the ring is supported by a central frame mounted axially with respect to the ring within the house.

21. A main distribution station substantially as hereinbefore described with reference to Figures 1 to 10 of accompanying drawings.

22. A sub-station substantially as hereinbefore described with reference to Figure 11 of the accom panying drawings.