Title: Electricity distribution system, end user residence, and method

The invention relates to an electricity distribution system, arranged to provide low voltage to end users located at end user locations, for instance vehicles.

Such a system is known per se from practice. A known system is, for instance, arranged to provide airplanes with electricity during stopovers at airports.

It is typically desired that, after landing, airplanes are ready to take off again as soon as possible. Therefore, the period during which the airplane stands still at a respective gate of the airport needs to be as short as possible.

Airplanes standing still during a stopover, whose main engines have been switched off, are to be provided with electricity to feed several electricity -consuming parts. Typically, to this end, each airplane is provided, in the tail, with an auxiliary generator with respective auxiliary turbine, which burns fuel (for instance kerosene). It has been found that the greater part of airplane-related CO2 emission of an airport is caused by these airplane auxiliary generator/turbine systems. The auxiliary generators and turbines need to have a compact and lightweight design for use in airplanes, and are very inefficient (with efficiencies of maximally 15%). When an airplane needs to stand still relatively long, usually an external diesel generator is connected to the airplane. Such external diesel generators are rather sizeable, inefficient (with a maximum efficiency of 20%), little user-friendly, make a lot of noise and are, moreover, particularly environmentally harmful. WO2007/061622 describes an airplane support system with a mobile cart, arranged to convert a 3-phase 460 VAC (i.e. low voltage). The

cart is provided with a diesel generator to generate the low voltage, and may alternatively be supplied with low voltage via a power cable.

WO01/97360 discloses a battery charging system. Fig. 1 of this document merely shows a circuit breaker CBl and vehicle chargers provided with their own circuit breakers CB2, CB3. The present invention contemplates obviating above-mentioned drawbacks of known systems. In particular, the invention contemplates an entirely new electricity distribution system, with which electricity can be provided to end users, for instance vehicles, in a particularly efficient and environmentally friendly manner.

According to the invention, to this end, the system is characterized by the features of claim 1.

The system comprises:

- a first medium voltage line for providing medium voltage, wherein the first medium voltage line is provided with a number of branches; and

- several end user electricity providers associated with respective several end user locations, wherein each end user electricity provider is couplable to a said end user located (stored) at the respective end user location, and is arranged to provide low voltage to the end user. It is then particularly advantageous when the end user electricity providers are each couplable to a respective branch of the medium voltage line via a respective second medium voltage line to receive medium voltage, and are arranged to convert the medium voltage to low voltage to be provided to an end user. Use of the invention can take medium voltage to near the end users

(for instance airplanes, vessels, vehicles, mobile fairground attraction apparatuses or other end users), in particular utilizing the end user electricity providers. In this manner, local CO2 emission of, for instance, an airport (or other end user residence) can be reduced considerably (in some cases by as much as a factor of 10), in that activation of auxiliary generators

of end users during stationary end user condition can be avoided. Further, losses can be minimized, in particular when a large number of end user locations are served (as when used at an airport), particularly compared to the known systems which use only low voltage. To date, no one has conceived the idea of locally using medium voltage (instead of diesel generators or low voltage), probably because of fear of electrocution, risk of sparks, for instance near airplanes. The present invention overcomes this prejudice. According to an extra advantageous elaboration, each above-mentioned branch is provided with a safety device, in particular a high- voltage fuse, for the protection of a second medium voltage line coupled thereto. Preferably, each branch (in particular a respective second medium voltage line) is provided with a grounded shield. Thus, it is found that a surprisingly safe system is obtained, where risk of electrocution due to accidental cutting of a second medium voltage line is prevented. Thus, upon cutting of a second medium voltage line, first the grounded shield is touched, and only then a well protected, voltage-carrying medium voltage conductor of this line, which has been found to provide a high degree of safety (this has been established experimentally).

The invention further offers a method characterized by the features of claim 16. The method may, for instance, comprise a use of the system according to the invention.

In an advantageous manner, the method comprises a particularly environmentally friendly and user-friendly method of providing low voltage to end users located in a residence, for instance movable end users, vehicles, airplanes or vessels. An end user is coupled to a respective end user electricity provider, while the end user electricity provider receives medium voltage and converts it to the above-mentioned low voltage. According to a further elaboration, each end user and respective end user electricity provider may, for instance, be moved towards each other from a position away from each other in order to be intercoupled. According to a non-

limiting example, in the position moved towards each other, end user and respective end user electricity provider may be at a relatively short distance from each other, for instance a distance of less than 100 m, preferably shorter than 25 m and more in particular shorter than 10 m. The end user is in particular movable from and to an above- mentioned end user location.

It is further advantageous when each end user electricity provider is movable individually. This provider may, for instance, be provided with a windable and unwindable medium voltage cable, to be coupled to a main medium voltage line. At least one (and preferably each) of the end user electricity providers may, for instance, unwind a medium voltage line during movement towards an end user located at an end user location, and wind the medium voltage line during movement away from the end user.

Further elaborations are described in the subelaims. The invention will now be explained on the basis of an exemplary embodiment and with reference to the drawing, in which:

Fig. 1 schematically shows a system according to an exemplary embodiment of the invention;

Fig. 2 schematically shows an end user electricity provider of the system shown in Fig. 1;

Fig. 3 schematically shows a branch station of the system shown in Fig. 1;

Fig. 4 shows an example of a medium voltage coupling of the station shown in Fig. 3, in an uncoupled condition; and Fig. 5 shows the medium voltage coupling in a coupled condition.

In this application, like or corresponding features are designated by like or corresponding reference characters.

Fig. 1 schematically shows an example of an end user residence (in this case a vehicle residence), provided with several (for instance predetermined) end user locations to store several end users, in this case

vehicles P. These end user locations may be mutually physically separated locations, and/or comprise docks, landing stages (for boats), vehicle support platforms, locations on a parking lot or in a conference hall, or the like, and may have varying positions or, conversely, specific predetermined positions. Preferably, the end user locations are provided with specific markings (not shown), to indicate where each end user location is located. Further, different end user locations may be near one another, and/or at a relatively large distance from one another. At an airport, for instance, different platforms located at a distance from one another may be provided to store airplanes P, while each platform provides several locations to receive several airplanes.

The example shown in Fig. 1 particularly comprises a part of an airport, where airplanes P are located. The airport is provided with an exemplary embodiment of an electricity distribution system Kl, 3, K2, 10 to provide low voltage to the airplane P stored in the residence, at least at the above-mentioned end user locations. Only a part of the system Kl, 3, K2, 10 is shown in the Figure.

The above-mentioned low voltage to be provided to the vehicles P is preferably a voltage lower than 1 kV, in particular a voltage in the range of 100-500 V.

The end users (in this example: airplanes) P, for instance, stand still when they have been coupled to the electricity distribution system, for instance during a stopover at the airport. Each airplane P may be uncoupled from the electricity distribution system for the purpose of leaving (e.g. taxiing to a runway and taking off), the airplane leaving the respective (for instance predetermined) end user location.

The electricity distribution system Kl, 3, K2, 10 is particularly arranged to provide low voltage to end users (in this case vehicles) P located stationarily at end user locations, and comprises one or more first medium voltage lines Kl (in this case only one) for providing medium voltage.

The first medium voltage line Kl is preferably laid at least partly underground, for instance at the locations of branches 3. This line Kl may, for instance, be coupled to an electricity provider (not shown) (for instance a power station). Coupling between the medium voltage line Kl and electricity provider for the purpose of providing current to this line Kl may be carried out in different manners, for instance via a high-voltage grid, distribution stations and the like (not shown), which will be readily apparent to a skilled person.

Preferably, each first medium voltage line Kl is in itself a multi- phase line Kl, for instance a three-phase line which operatively provides three different phases of electricity ("power current"). Such line Kl are known per se from practice, and may, for instance, comprise a power cable, which is provided with different conductors 11, 12, 13 to conduct the different current phases (see Fig. 3). The conductors 11, 12, 13 are preferably surrounded by a suitable (optionally steel wire-reinforced) safety sheath, which sheath may, for instance, also comprise a grounding shield (surrounding the conductors). The conductors 11, 12, 13 are electrically insulated from one another (by means of a suitable insulating material). In addition, the medium voltage line Kl may, for instance, be provided with one or more neutral conductors, for instance a common neutral line N (e.g. a neutral conductor N surrounded by the safety sheath, which also serves as a grounding shield). This grounding shield may, for instance, be a closed metal (for instance lead) pipe under the safety sheath, or may consist of many thin parallel conductors (for instance copper conductors) under this same safety sheath, or may be designed in a different manner.

Preferably, the first medium voltage line Kl operatively provides a voltage in the range of 1-50 kV, in particular 1-25 kV, more in particular 5-15 kV. This medium voltage is particularly an AC voltage and has, for instance, a (first) frequency of less than 100 Hz, for instance 50 Hz or 60 Hz. In case the medium voltage is provided via several conductors 11, 12, 13, as in

this exemplary embodiment, the above-mentioned medium voltage is a voltage between any two voltage-carrying conductors 11, 12, 13. In that case, the voltage per conductor can be determined in the known manner: with the three-phase current (with three conductors 11, 12, 13 to present the three- phase medium voltage), the voltage between each conductor and ground (i.e. the neutral conductor N) is the 1/V3 (square root of three) value of the total voltage (between any two conductors). So, in that case, the medium voltage per conductor 11, 12, 13 is lower than the total voltage provided by the first medium voltage line Kl. The first medium voltage line Kl comprises a number of branches 3. Each branch may be designed in different manners. Figs. 3-5 show examples of a local branch station 3 to provide such a branch (see below).

As Fig. 1 further shows, the system is, for instance, provided with several local end user electricity providers 10 associated with respective end user locations. In this case, one local electricity provider 10 is provided per end user location. Optionally, several electricity providers 10 may be provided per end user location. Further, for instance, one local electricity provider 10 may be arranged to provide low voltage to several end user locations. Each end user electricity provider 10 may, for instance, be arranged to provide powers in a range of approximately 50 to 800 kW, or in a different range.

According to a further elaboration, each branch 3 of the first medium voltage line Kl branches only one of the above-mentioned phases to a respective second medium voltage line K2. The second medium voltage line K2 is therefore preferably a single-phase electricity line.

Each above-mentioned second medium voltage line K2 may, for instance, comprise a cable, preferably a coax cable. Preferably, the cable K2 is at least partly movable relative to the branch 3. The cable K2 may be provided with only one line operatively carrying medium voltage, for

instance a central conductor of the coax cable. The coax cable K2 may further be provided with a respective neutral conductor which is electrically insulated from the voltage-carrying conductor, in a conventional manner.

In particular, the neutral conductor of the coax cable K2 is a part of a sheath of the coax cable, which part is electrically insulated from the central conductor of this cable K2. Preferably, this neutral conductor consists in itself of a large number of conductors, for instance at least 50 neutral conductors (for instance thin copper wires), which are provided in the sheath of the cable K2. The sheath of the coax cable K2 preferably comprises a suitable safety sheath, which is arranged to prevent mechanical damage of the cable K2.

Each above-mentioned second medium voltage line (or cable) K2 may have a relatively short design compared to a total length of the first medium voltage line. A length of this first medium voltage line Kl may, for instance, be kilometers. A maximum length of a second medium voltage line K2 may, for instance, be shorter than 1 km, in particular shorter than 200 m. In particular, each second medium voltage line has a length in the range of 10-200 m, in particular 10-100 m.

Each end user electricity provider 10 may be couplable to a respective branch 3 of the medium voltage line Kl via a respective second medium voltage line K2 to receive medium voltage (in particular only one phase thereof). Further, each end user electricity provider 10 may be arranged to convert the medium voltage received via line K2 to the low voltage to be provided to a vehicle P. The electricity providers 10 are each couplable to an end user (in this case: airplane) P located at the respective end user location (see also the example in Fig. 2), to provide the end user P with electricity (in particular the above-mentioned low voltage) in an intercoupled condition.

According to a further elaboration, the end user electricity provider 10 is further arranged to couple the end user P to an electricity

neutral conductor, which neutral conductor is provided via the above- mentioned second medium voltage line K2 and is operatively coupled to an above-mentioned neutral conductor N of the first medium voltage line Kl.

In addition, the end user electricity provider 10 may be arranged to couple the end user P to a separate, local ground line A (see Fig. 3); in this example, such a ground connection may be brought about via a branch station 3, in particular via the neutral conductor of the second medium voltage line K2.

End user electricity provider

A non-limiting example of a local electricity provider 10 ("low voltage station") is shown in Fig. 2.

The electricity provider 10 as such may, for instance, comprise an electronic control unit 14, which may, for instance, be provided with suitable hardware, software, a computer, processor, memory, user interface (e.g. with display, keyboard, control buttons and/or the like), which will be readily apparent to a skilled person. The control unit 14 may be configured to regulate, control, etc. various tasks of the electricity provider 10. According to a particularly advantageous elaboration, the end user electricity provider 10 is disposed movably relative to (for instance along or over) a respective end user location. An arrow T in Fig. 2 indicates such a movement. Then, it is further advantageous when the end user electricity provider 10 is automatically movable, in particular under the influence of a drive arranged to this end.

The movable end user electricity provider 10 may, for instance, comprise a frame, a watertightly sealable housing and/or the like, to which/in which various parts of the provider 10 are mounted.

Movement of the local provider 10 may be carried out in various manners. Thus, the provider 10 may, for instance, be disposed movably

along guide means, for instance rails or the like (not shown). In addition, the provider 10 may, for instance, be provided with one or more motor-drivable wheels to move the provider 10 over a ground surface W.

Optional remote control of the provider 10 may, for instance, be carried out by means of a centrally disposed control unit B, which transmits control signals to the provider 10 to make the provider 10 carry out a particular action, for instance a desired movement. Transmission of control signals - between the end user electricity provider 10 on the one side and, for instance, a control unit B located at a distance therefrom - may be carried out via suitable communication means 13, for instance with transmitter and receiver means (optionally wireless, or with the aid of communication via a voltage-carrying conductor, with the aid of Power Line Carrier). According to a further elaboration, remote control of the provider 10 may be carried out utilizing the second medium voltage line as a control signal transmitting means. In addition, the control unit B may comprise a remote control which can be carried manually (by just one person).

A preferred embodiment comprises a movable end user electricity provider 10, which is couplable to an above-mentioned branch 3 by means of a flexible, preferably windable and unwindable power cable serving as a second medium voltage line K2 (i.e. K2). The second medium voltage line K2 is preferably an above-mentioned coax cable. In the example, the end user electricity provider 10 is provided with a pulley 18 rotatable by a drive, for automatically winding and unwinding the power cable K2 during movement of the electricity provider. An arrow G in Fig. 2 indicates winding/unwinding of the power cable K2.

The end user electricity provider 10 is designed to convert the medium voltage supplied via the second medium voltage line (cable) K2 to an above-mentioned low voltage suitable for the vehicle P. To this end, the

provider 10 is provided with a suitable voltage converter 15, for instance comprising a transformer, voltage converter electronics and/or the like.

As said, the first and second medium voltage lines Kl, K2 preferably provide alternating current with a first frequency. Preferably, the end user electricity provider 10 is arranged to provide electricity (to an end user), which electricity has a frequency which is usable by a respective end user P.

An end user electricity provider 10 may be designed to provide voltages with different predetermined frequencies, if different end users P to be coupled need to receive voltages with such different frequencies.

The end user electricity provider 10 may, for instance, be arranged to generate from the alternating current a low voltage with a second frequency, and to provide this low voltage to a vehicle P, while the second frequency is a predetermined frequency which can be used by the end user. ■ According to a further elaboration, the second frequency differs from the first frequency. The voltage converter 15 may, for instance, be integrally provided with or coupled to one or more frequency converters (i.e. frequency transformers, frequency regulators) 16 known per se, to bring about the desired frequency adjustment. In particular for use in combination with airplanes, it is advantageous if the second frequency is higher than the first frequency. The second frequency (of the low voltage to be provided to the vehicle P) may, for instance, be higher than 100 Hz, for instance be in the range of approximately 200-500 Hz, and be, for instance, approximately 400 Hz. As already follows from the above, such a second frequency particularly depends on the frequency that can be processed by an end user P to be coupled.

According to a further elaboration, the end user electricity provider 10 may, for instance, be provided with a rectifier to convert the low voltage provided by the voltage converter 15 to a direct current. Such a rectifier may, for instance, be part of the voltage converter 15 (and may, for

instance, be coupled downstream to an above-mentioned transformer of the voltage converter 15).

According to a further elaboration, an above-mentioned optional frequency converter 16 may, for instance, be arranged to convert an above- mentioned DC voltage (provided by an optional rectifier) to AC voltage.

The provider 10 may, for instance, be provided with one or more (optionally detachable) connecting cables 11, each provided with a coupling part 12 which is detachably connectable to a voltage input of the vehicle P. The provider 10 may comprise storage means, for instance a reel, storage cabinet or the like, to store the connecting cable 11, when the cable 11 is not in use. The connecting cable 11 is coupled to an output of an above- mentioned voltage converter 15, or of an optional transformer 16, to provide the voltage provided thereby during use to vehicle P.

Further, the connecting cable 11 may couple an above-mentioned neutral conductor to the vehicle P. The provider 10 (electrically) couples this neutral conductor to a neutral conductor provided by the second medium voltage line (via an electrical connection which is not shown).

Above-mentioned coupling part 12 and voltage input pi may be designed in various manners, for instance comprising grounded plug means or the like. Further, the system may be provided with adapters which are suitable and intended for coupling the power cable 11 to different types of voltage inputs pi of different vehicles P.

The coupling part 12 may further, for instance, be provided with one or more control buttons, which may, for instance, be arranged to switch voltage on the power cable 11 on and off. The coupling part 12 may further, for instance, be provided with one or more indicating means to indicate whether the power cable 11 carries voltage, and/or to indicate how high the voltage is (and optionally, which frequency the AC voltage has).

A low voltage provided by the end user electricity provider 10 may further be used to provide various parts of the end user electricity provider

with electricity. Further, the provider 10 may be designed to generate different low voltages (from the medium voltage supplied), for instance a first low voltage for the benefit of a vehicle P coupled to the provider 10, and one or more second low voltages for 'private use'. A latter low voltage (for 'private use') may, for instance, comprise direct current (DC).

The end user electricity provider 10 may, for instance, be provided with one or more rechargeable batteries, to store electricity; these batteries are preferably rechargeable utilizing an above-mentioned (first or second) low voltage provided by the provider 10 itself. In this example, the end user electricity provider 10 is further, in an advantageous manner, provided with a cooling and/or heating device 17, which device 17 is arranged to provide a thermally conditioned cooling and/or heating medium to a vehicle P. According to a further elaboration, this medium is air. The cooling and/or heating device 17 is preferably fed by a low voltage provided by provider 10 itself. This device 17 may be designed in various manners, for instance with a cooling circuit, compressor, condenser, coolant pump and/or the like.

The end user electricity provider may be provided with an (optionally detachable) connecting hose 19 to supply the medium cooled and/or heated (at least, thermally conditioned) by the cooling and/or heating device, respectively, to the vehicle P. The vehicle P may be provided with a specific medium connecting point p2, which is in fluid communication with a cooling and/or heating circuit of the vehicle P, to connect the hose 19 (or a suitable connecting head of the hose 19) thereto.

Alternatively, the hose 19 may, for instance, be fed into the end user via a passenger entrance, to blow thermally conditioned air directly into the end user P. Alternatively, the return air may be fed back via another hose (not shown).

Branch

An above-mentioned branch 3 of the system may be designed in various manners. A branch of the present system is designed in each case to branch a single phase from the medium voltage, via a second medium voltage line K2 connected to the branch 3. Different branches 3 (see Fig. 1) may be arranged to branch mutually different phases from the first line Kl; however, such different branches do not need to be adjacent branches 3.

In addition, the branch may couple a neutral conductor of the second medium voltage line K2 (in particular a neutral conductor sheath part of this cable K2) to a neutral conductor N of the first line Kl. Further, it is preferred if the branch locally electrically couples the neutral conductor of the second cable K2 to ground (for instance a ground obtained locally near the branch, for instance via a ground connection A provided in the soil or via a ground conductor separately installed at the same time, for instance a PEN conductor). Thus, this neutral conductor of the medium voltage cable K2 is (operatively) grounded, which provides the system with a high degree of safety.

As Figs. 4-5 show, an above-mentioned branch 3 of the system may, for instance, be provided with one or more manually operable detachable couplings 5, to couple one or more second medium voltage lines K2 to the first medium voltage line Kl.

Alternatively, an above-mentioned branch 3 of the system and a second medium voltage line K2 may, for instance, be interconnected by means of a non-detachable coupling.

Further, an above-mentioned branch 3 may be provided with one or more safety devices, in particular a high-voltage fuse 4, for the protection of a second medium voltage line K2 coupled thereto.

As Fig. 3 schematically shows, a branch may, for instance, comprise a (preferably closable) branch station 3, which is disposed near the

first medium voltage line Kl; a part of the first medium voltage line Kl may, for instance, be fed through the station 3.

The branch particularly comprises a first branch line 8, provided with an output 28, coupled to a conductor 11 of the first medium voltage line Kl. Preferably, the branch also comprises a second branch line 9, which is coupled to a neutral conductor N of the first medium voltage line Kl. The second branch line 9 comprises an output 29. The electrical connection between each branch line 9, 10 and the respective transport conductors 11, N of the first medium voltage line Kl may be designed in various manners known per se to a skilled person.

Further, a separate local ground connection A is provided, which, in this case, is locally provided near the branch station 3. A connection 7 locally electroconductively connects the ground connection A to the neutral conductor, via the second branch line 9, so that the neutral conductor is grounded.

In the example, the above-mentioned high-voltage fuse 4 is provided in the first branch line 8. The high-voltage fuse 4 may be arranged to interrupt the first branch line 8 if a short-circuit current runs through it, for instance a short-circuit current having a value of approximately 5 times the nominal value of a current carried through this line 8, in particular when the current carried through the fuse exceeds a particular threshold value (for instance 5x100 Ampere, in particular 5x80 Ampere, or a different value). Use of such a high- voltage fuse 4 results in a particularly safe and reliable branch; moreover, such a fuse is in itself relatively inexpensive. The above-mentioned detachable coupling 5 may be designed in various manners and may comprise, for instance, coupling sleeves, coupling plugs, plug means and/or the like. Fig. 4 shows a condition in which the second medium voltage line (i.e. the flexible extension cable) K2 has come off the coupling 5, and Fig. 3 shows a coupled position.

Preferably, the configuration of the branch 3 is such that the second medium voltage line K2 only receives medium voltage if the medium voltage line K2 is locked to the branch station. This may be achieved in various manners. The present system comprises, for instance, a circuit breaker 51 which interrupts an electrical connection between the first branch line 8 and an output 28 of the branch station 3 if no medium voltage line K2 is coupled to the branch station (see Fig. 4).

The first branch line 8 may, for instance, be provided with a power- cutout switch 95, which is arranged to allow an electrical connection in this first branch line 8 only after it has been determined that the second medium voltage line K2 is coupled to the branch station in a desired (safe) manner (see Fig. 4). In the example, the power-cutout switch 95 is disposed behind (i.e. downstream with respect to) the fuse 4. Preferably, a detector 52 is provided to control the power-cutout switch 95.

The configuration is preferably such that the power-cutout switch 95 closes the first branch line 8 only after it has been determined that the circuit breaker 51 is closed completely. The power-cutout switch can be controlled to automatically interrupt the first branch line 8 as soon as the circuit breaker 51 is or has been opened. In this manner, it can be achieved that the circuit breaker 51 as such is not carrying voltage during coupling and uncoupling of a second medium voltage line K2.

The circuit breaker 51 may electrically interconnect the first branch line 8 and the output 28 of the branch station 3 if the second medium voltage line K2 is indeed coupled to the branch station (see Fig. 5). The circuit breaker 51 may be designed in various manners. In this example, the circuit breaker 51 as such has a substantially mechanical design, and comprises a movable electrically conductive bridge 59 to bridge an interruption in the branch line 8. Fig. 4 shows a first position in which the bridge 59 is moved away from the interruption in the branch line 8, such

that no medium voltage is available at the output 28. Fig. 4 shows a second position in which the bridge 59 makes electrical contact with the branch line 8 to bridge the interruption, such that the medium voltage is available at the output 28. In this example, the operation of the circuit breaker depends, in addition, on a medium voltage line locking system. The configuration is such that, if the second medium voltage line K2 is coupled to the branch station 3 in a predetermined manner safe for bystanders, the circuit breaker 51 can be operated to enable provision of medium voltage to the second medium voltage line K2 (via the output 28). In case the second medium voltage line K2 is not coupled to the branch station 3 in a particular manner, the circuit breaker automatically brings about interruption of voltage supply to the medium voltage output 28.

The second medium voltage line K2 comprises, for instance, a coupling piece 25 which can cooperate with the detachable coupling 5. The coupling piece 25 is, for instance, provided with a first connector part 25A to receive the medium voltage from the respective output 28 of the branch station 3, when the coupling piece 25 is retained by the coupling 5 (i.e. in the coupled position, as in Fig. 5). The present coupling piece 25 comprises a second connector part

(neutral conductor coupling part) 25B to make electrical contact with the output 29 of the second branch (neutral) line 9.

Preferably, the configuration of coupling piece 25 and coupling 5 (comprising outputs 28, 29) is such that, during coupling, first, electrical contact is made between the grounded neutral conductor parts 25B and only then between an above-mentioned first connector part 24A and voltage output 28.

The detachable coupling 5 may be provided with a locking system 55, 56 to lock the coupling piece 25 to the branch station 3, if the coupling piece 25 is in the coupled position. In this example, the locking

system comprises a retaining body 56 (for instance a housing or frame) which is movable (relative to the station 3), which can engage the coupling piece 25 (in this case a side of the coupling piece 25 remote from the output 28) and can keep it in the position coupled to the coupling 5. In this example, a handle 55 coupled pivotally to the branch station 3 is provided, which is coupled to the retaining body 56 via a pivot in order to move this body 56. Means of changing a position of the retaining body 56 may also be designed in a different manner. In this example, the locking system 55, 56 is also arranged to operate the circuit breaker 51, depending on coupling of the coupling piece 25.

In a non- limiting example, the coupling (output) 5 of the branch station 3 is provided with blocking means 52, 53, 54 designed to prevent operation of the circuit breaker 51 when the coupling 5 is not provided with a coupling piece 25. The blocking means may, for instance, have a mechanical design, or a wholly or partly electrical or electronic design. In this example, the system comprises a detector 52, which is arranged to detect whether a coupling piece 25 has been provided on the coupling 5 in a predetermined (desired) manner. The detector 52 may, for instance, be designed to detect the presence of a coupling piece (in the coupling 5), for instance utilizing optical, mechanical, or electrical detection means and/or in a different manner. In this example, the detector 52 can cooperate with the power-cutout switch 95 to control this switch 95. Control of the power-cutout switch may also be carried out in a different manner, which will be readily apparent to a skilled person. The blocking means further comprise, for instance, a device 53, 54 which cooperates with the operating means 55, 56, 57 of the circuit breaker 51. In this example, this device 53, 54 is designed to block operating means 55, 56, 57 depending on the detection carried out by detector 52. In this example, the device comprises, for instance, an actuator 53 which makes a blocking element 54 engage locking system 55 to prevent operation

of the locking system as long as the detector 52 detects no coupling piece 25. The actuator 53 can release locking system 55 automatically, by a suitable movement of the blocking element 54 when the detector 52 does detect a coupling piece 25. Control of such blocking means 52, 53, 54 may, for instance, be carried out by an (electronic) control Q suitable for this purpose.

As mentioned, the locking system 55, 56 may be arranged to operate the circuit breaker 51. In the non-limiting example, this operation can take place only after the locking system 55, 56 has been released by the blocking means 52, 53, 54, so when a coupling piece 25 of the second medium voltage line K2 is coupled to the branch station 3 in a suitable manner. In particular, the retaining body 56 is provided with a transmission part 57 to transmit movement of retaining body 57 to the bridge part 59 of the circuit breaker 51. Here, the bridge part 59 is provided with an electrically insulating wedge part 58, provided with a shear surface which transmission part 57 can engage; the configuration of wedge part 58 and transmission part 57 is such that a first translation movement of the transmission part 57 (with a coupling piece-locking movement of the retaining body 56) results in translation of the wedge part 58, such that the wedge part 58 moves the bridge part 59 attached thereto towards the voltage line 8. A reverse translation of wedge part 58 may, for instance, be carried out under the influence of spring means (not shown), or in a different manner.

Use

Use of the system shown in the Figures may comprise a method according to the invention. Here, one or more end users (in this case airplanes) P are coupled to one or more respective end user electricity providers 10, while the end user electricity providers 10 receive medium

voltage and convert it to the above-mentioned low voltage (in this case with a desired frequency).

The electricity provider 10 is, for instance, coupled to a branch station 3 with a respective (at least partly unwound) second medium voltage line K2, utilizing the respective coupling piece. Here, the coupling piece 25 is connected to the coupling 5, such that the locking system 55, 56 is released by the blocking means 52, 53, 54. Then, the locking system can be operated to retain coupling piece 25 in the coupled position, which also results in operation of the circuit breaker 51, and then in operation of the power-cutout switch 95 (under the influence of the detector 52), so that the second medium voltage line K2 is also electrically connected to the voltage-carrying first branch line 8 (via output 28 and first connector part 25A). This results in the condition shown in Fig. 5, where the medium voltage supplied via a conductor of the first medium voltage line Kl reaches the second medium voltage line K2 via first branch line 8, fuse 4, closed power-cutout switch 95, closed circuit breaker 51 and output 28. In this condition, the neutral conductor of the second medium voltage line K2 is electrically coupled by the branch station 3 to the (locally grounded) neutral conductor N of the first medium voltage line Kl, and thus grounded on itself.

During use, each end user P and respective end user electricity provider 10 may, for instance, be moved from a position away from each other towards each other in order to be intercoupled, and, in the position moved towards each other, may preferably be at a distance shorter than 100 m from each other, preferably shorter than 25 m and more in particular shorter than 10 m.

In particular, an end user electricity provider 10 may move towards an airplane P, for instance utilizing an above-mentioned remote control B. Here, the end user electricity provider can unwind the respective medium voltage line K2.

The electricity provider 10 is, for instance, coupled to the end user P via the means intended and suitable for this (in this case a low voltage cable 11 and coupling part 12). The distance between electricity provider 10 and end user P may then be relatively short, for instance a distance of less than 50 m, in particular less than 10 m.

Preferably, the low voltage cable 11 can couple a local grounding through to the end user P, automatically, for instance via a neutral conductor. During coupling of the low voltage cable 11 to the vehicle, then preferably, first, electrical contact is made between a grounded neutral conductor part of the cable 11 and the vehicle P, and only then between a low voltage-carrying part of the cable 11 and the vehicle P.

The electricity provider 10 provides low voltage to the vehicle P, by converting medium voltage obtained via the second medium voltage line K2 to low voltage. Optionally, the end user electricity provider 10 may provide the end user P with a cooled or heated medium, for instance for the purpose of feeding a temperature conditioning system of the vehicle.

After a desired electricity provision, for instance prior to leave of the end user P (i.e. leave from the end user location), the end user electricity provider 10 may, for instance, move away from the vehicle P; in the process, medium voltage line K2 may be wound again.

According to a further elaboration, the medium voltage line K2 may carry voltage at least during winding and unwinding to provide the electricity provider with electricity.

In this manner, end users, for instance vehicles, airplanes, or other end users, can be provided with electricity (comprising a particular voltage with a desired frequency) in a particularly efficient manner. In this manner, emergency power units of end users may be prevented from being activated, for instance during stopovers, which considerably reduces the local emission of undesired poDutants. The present system is particularly safe to use, and energy-saving.

It will be readily apparent to a skilled person that the invention is not limited to the exemplary embodiments. Various modifications are possible within the framework of the invention as set forth in the following claims. The term "a" may, for instance, mean only one, or a plurality. Thus, for instance, different end user electricity providers 10 may be coupled to different branches 3, or to one and the same branch 3.

Further, a vehicle may, for instance, be provided with low voltage by only one (external) end user electricity provider 10, or by two or more end user electricity providers 10 (for instance if the vehicle is provided with several low voltage inputs).

End users may, for instance, comprise vehicles, airplanes or vessels. In particular, each end user is movable to a predetermined end user location, to temporarily reside at the end user location (to be stored there), to then leave the end user location. Further, the end users may comprise mobile fairground attraction apparatuses, caravans, trailers, market end users, conference stands, and other end users. Also with such end users, the present invention can obviate local nuisance of use of (diesel) generators. According to a further elaboration, for instance, several second medium voltage lines K2 may run along one another over a particular distance, and may, for instance, be intercoupled with coupling means, for instance tie-wraps or belts.

Further, an end user electricity provider 10 may, for instance, be provided with multi-phase current (for instance three-phase current), by supplying different phases via different (separate) second medium voltage lines K2 to the end user electricity provider 10. In this case, the end user electricity provider may be arranged to convert the separately provided multi-phase medium voltage current to multi-phase low voltage.