Introduction

The present invention relates to a power source for use in installation of electricity meters, especially smart meters, at properties. In particular, the invention relates to a portable power source and methods of installing meters using the power source.

Background to the Invention

Most properties, residential and commercial, are connected to grid mains electricity, and nowadays interruptions in the power supply from the mains are few and far between. This is just as well for many electrically powered items are affected by loss of power, notably clocks and timers which if they do not reset automatically must have their clocks adjusted manually each time power is interrupted. In fact, more or less all electrical equipment can potentially be damaged by power interruptions.

Though power-outs are rare there can, nevertheless, be good reasons why it is necessary to disconnect a property from the grid, for example to allow essential maintenance to or upgrading of components of the mains electricity supply and associated equipment.

In the UK there is a government-imposed target to install smart meters in all domestic properties by 2020, and the installation process requires disconnection of power. Other electrical work at a property can similarly require power disconnection, and all such disconnections from electrical power are inconvenient.

It is known to provide uninterrupted power supply (UPS) devices, typically to protect individual pieces of equipment from sudden power loss or variation in power beyond certain limits. Often a UPS merely provides replacement power for long enough to shut down the equipment safely. It is also known to provide larger scale UPS units for a whole property that can similarly provide replacement power in the event of a disconnection or which can switch between alternative sources of power, for example between grid mains, solar power, generator power etc. These UPS units are expensive and rarely found in anything but the few biggest, remotest or most expensive properties. Also, they are located in series with the grid mains, so to install one requires disconnection at that time from the grid mains. A problem with carrying out work at a property, such as meter installation, is that hitherto it has been necessary to turn off the power for the duration of the work. During this time, there is no power to the property, lights are off and even low power consuming items cannot be used. Separate from any damage it may cause, the power disconnection is disruptive if anyone is inside the property. In addition, doing such work, e.g. meter installation, during the hours of darkness is restricted or awkward or requires additional lighting equipment. A further problem with typical known UPS devices is they have limited power output capacity and can supply power in series to just a few pieces of equipment. Individual UPS devices are also generally not suitable for whole property use, or where power demand is higher. It is clear from the prior art that there exists a need for improved and alternative power sources and associated methods of working at properties when disconnection from grid mains is required.

An aim of the present invention is to provide alternative such sources and methods. An aim of embodiments is to provide power sources and methods of using these that at least ameliorate one or more problems identified in the art. A further aim of preferred embodiments is to provide power sources and methods of using these that provide improvements in carrying out electrical work, such as meter installations, at a property when the grid mains must be disconnected.

Summary of the Invention

Accordingly, the invention provides a method of working at a property that comprises disconnecting the property from a mains power grid, for example installing an electricity meter such as a smart meter, the method comprising

(1 ) disconnecting the property from the mains power grid and connecting the property to a separate power source;

(2) carrying out the work, e.g. installing the smart meter; and

(3) disconnecting the separate power source and reconnecting the property to the mains power grid, e.g. via a newly installed smart meter,

wherein in steps (1 ) and (3) there is no interruption in supply of power to the property. An electrical power source for a property connected to a mains power grid is also provided by the invention, comprising:

(1 ) a source of AC power;

(2) electrical outputs to connect the source to power supply inputs at the property; and

(3) circuitry that in use detects when grid mains power to the property has been disconnected and switches on power supply to the property from the source without interrupting supply of power to the property. The invention offers an alternative to existing methods and apparatus and can provide notable advantages.

Details of the Invention

A method of working at a property that comprises disconnecting the property from a mains power grid, for example when installing an electricity meter such as a smart meter, hence comprises

(1 ) disconnecting the property from the mains power grid and connecting the property to a separate power source;

(2) carrying out the work, e.g. installing the smart meter; and

(3) disconnecting the separate power source and reconnecting the property to the mains power grid, e.g. via a newly installed smart meter,

wherein in steps (1 ) and (3) there is no interruption in supply of power to the property.

This enables installation work without power interruption, avoiding the disadvantages noted, and also enables such work during the hours of darkness and also while people are in the property - because of the effectively continuous electricity supply now made possible by the invention.

In a use, the method typically comprises connecting the separate power source in parallel with the grid mains. Power from the source can then be switched on to replace grid mains - no power disconnection is hence needed. The invention can hence provide a temporary power source during disconnection from the mains. Preferably the power source is connected in parallel to the grid mains by plugging it into a mains power socket (e.g. a double mains power socket) within the property. Such power sockets are typically easily accessible and numerous in properties and connection of the power source to the sockets is fast, simple and does not require any tools to make this connection.

Step (3) may further comprise a subsequent step of removing the separate power source from the property - it can then be used for work at another location. Step (1 ) typically comprises bringing the separate power source to the property; the unit is not located at or stored at the property but is portable and moves with e.g. an engineer between jobs. As described below in specific examples, the invention may comprise installing a new meter (i.e. an electricity meter) at the property using the power source, especially a smart meter. In use, the invention may thus comprise switching between the grid mains power supply and a battery-powered power source without interrupting the power supply to the property and reconnecting the property to the grid mains power supply via a (newly installed) smart meter.

The invention is especially suitable for use at properties having a conventional grid mains connection, e.g. made up of, in order, the grid mains, a mains fuse, a meter, one or more circuit breakers and/or a fuse board. Disconnection from the grid can include removing the mains fuse and/or operating the circuit breaker(s).

Alternatively, the work at the property may comprise repairing or replacing the main fuse. The main fuse and meter can be isolated from the power source and other power sockets within the property by opening the main circuit breaker.

In a specific example of the invention, described below in more detail, a method is provided for installing a smart meter at a property having one or more devices powered by electricity from a mains power grid, comprising

(1 a) connecting a separate power source in parallel with the grid mains;

(1 b) disconnecting the property from the grid mains and switching on supply of power from the separate source without interrupting supply of power to the one or more devices;

(2) installing the smart meter while providing power to the one or more devices at the property from the separate source; and (3) reconnecting the property to the grid mains via the newly installed smart meter and disconnecting the separate source without interrupting supply of power to the one or more devices. After meter installation, the method generally comprises removing the separate source from the property without interrupting supply of power to the property. As described elsewhere, the separate power source is preferably battery powered; the method suitably also comprises charging the battery from the grid mains prior to and/or after being used to supply power temporarily to the property. The source is then partly or fully recharged ready for subsequent use at a different property.

Also provided by the invention is power supply apparatus. Hence, an electrical power source for a property connected to a mains power grid is provided, comprising:

(1 ) a source of AC power;

(2) electrical outputs to connect the source to power supply inputs at the property; and

(3) circuitry that in use detects when grid mains power to the property has been disconnected and switches on power supply to the property from the source without interrupting supply of power to the property.

As described in more detail below, in preferred embodiments the apparatus comprises circuitry to synchronize the output from the power source with the grid mains phase prior to supplying power to the property from the power source. This smoothens switching to temporary power. A grid-tie inverter can be used - see elsewhere herein - commonly operating at approximately the following voltages and frequencies: 120V and 60Hz or 240V and 50Hz. Such inverters are known and may have wide voltage and frequency ranges and tolerances according to the nature of the local electrical grid mains supply. Once mains power is restored the apparatus can switch off. Hence, separately, it is preferred that the apparatus comprises circuitry that in use detects when mains power to the property has been reconnected and switches off power supply to the property from the source without interrupting supply of power to the property. Suitably, there is also circuitry to synchronize the output from the power source with the grid mains phase prior to reconnecting the property to the grid mains; this can smooth the reconnection to the grid. The source of AC power may be a generator but is more typically and preferably a DC battery (such as a DC rechargeable battery) in combination with an AC/DC inverter. Before the grid mains power to the property has been disconnected or after it has been reconnected, the grid mains power can be used to recharge the battery in the power source. The apparatus may therefore further comprise an inverter module comprising an inverter and a charger. The inverter module converts the DC battery power to AC power for supplying to the property when grid mains power is disconnected whilst charging the battery from the grid mains power when connected.

The power source is, as described above, suitable for connection to the property in parallel with the mains power grid. Electrical output to the property is preferably via one or more plugs each having outputs (e.g. pins) that can be plugged into conventional sockets inside the property. In preferred embodiments there are 2 plugs.

The plugs are typically standard mains electrics plugs (although it is noted that these may differ depending on the country in which the power source is to be used). For example, for use in countries such as the UK, the plug may be a Type G plug (as defined by the International Electrotechnical Commission) and comprise three rectangular blades in a triangular pattern.

For use in countries such as in the US and Canada, the plug may be a Type A plug with two flat parallel pins (outputs). The plug may also have an additional pin as an earth pin (Type B plug).

For use in most European countries (with the exception of UK, Ireland, Cyprus and Malta), the plug may comprise two round pins which can be accepted into 4.0 to 4.8mm round socket contacts (Type C plugs). The plug may also comprise an earth pin, socket or connector (Type D, E, F or J plugs).

For use in countries such as Australia or New Zealand, the plug may comprise two flat, angled pins to form a "V-shape" (Type I plugs). The plug also typically comprises a separate earth pin. Multiple sources can be connected simultaneously in parallel - all without power interruption. In the case that multiple sources are used in parallel, they are provided with a syncronising link (e.g. a cable) to ensure that the sources either all charge or all generate at the same time. Notably, the unit does not provide power to the mains grid, and circuitry and associated safety systems are suitably provided within the source to avoid it providing power to the whole grid. This might otherwise be a (low) risk in the event of a mains grid power failure during use of the source, for example its use in carrying out meter work as described elsewhere herein. For use of multiple sources at the same time to provide power to the same property, each source preferably comprises (i) a connector for connection of its control circuitry to that of the other source(s) and (ii) associated control electronics that provide for all sources simultaneously to provide power to the same property. Portable

Apparatuses of the invention are preferably portable, being sufficiently small and lightweight to be moved by a single person, such as an engineer visiting a property to carry out on-site work. The apparatus hence weighs typically 75 Kg or less, preferably 60 Kg or less, more preferably 50 Kg or less. Specific devices of the invention weigh approximately 25 Kg or less including battery, inverter, case, control systems and cables, and can hence easily be used and moved by one person. The apparatus may also comprise carry handles and/or wheels for further ease of manipulation and movement. Safety features and reconnection

Preferred apparatuses are adapted for safe use in domestic environments. For example, the apparatus is designed such that a live output (e.g. 240V AC, 50Hz in the UK) is not provided on exposed output plugs / pins, such as in mid air, if the plug is or plugs are disconnected from the property in use. Apparatus suitably comprises circuitry that in use detects connection of the power source outputs to the property and prevents generation of power from the source in the event that the connection is broken. Apparatus can be provided with two plugs, each with two (or three) output connectors or pins; circuitry of the apparatus detects when both (or all) are connected to the property and prevents switching on of live power until both (or all) are so connected, switching power off if either (or any) is disconnected. In apparatus with two (or more) plugs electrical output to the property and input for recharging the apparatus battery can be via one or more or all plugs. Further apparatus uses just a single plug with 2 or 3 pins (live and neutral or live, neutral and earth) and comprises circuitry to determine if the outputs of the one plug are connected to the property, for example by measuring resistance between neutral and earth; again, power is provided only when the measurement confirms both outputs are connected and switches power off if they are not. Still further apparatus comprises a mechanical switch as part of the plug that connects to the property socket; inserting the plug moves the mechanical switch into a position that allows power output from the source. Once the apparatus is connected its AC output is preferably synchronized with the AC grid mains (e.g. using a modified grid-tied inverter) and it is ready to generate power once the grid mains is disconnected. An optional feature of the apparatus is a generation Arm Switch. This switch allows the apparatus to only generate power when the mains grid is disconnected after being armed. As an alternative to a generation Arm Switch, the apparatus may comprise an input device (such as a keypad, NFC reader or NFID reader) to allow only authorised users to arm the device. When present it can prevent accidental generation of mains power outside of the property for example if the mains power fails externally to the property before the user wishes for the power source to supply power to the property.

The apparatus typically comprises a cable, or two cables, to connect to the sockets at the property. These can be a trip hazard. An option is to include circuitry to monitor for a trip that disconnects a cable, e.g. by monitoring the live output as described immediately above, so power can be switched off in such an event.

Another optional feature is a power output monitor; if this is too high, e.g. if the battery will be damaged by the output rate or if the battery is about to be dangerously discharged or exhausted then an alert may be triggered or the apparatus programmed to switch off before there is damage. An alert enables the user to turn off devices at the property to reduce the power output before damage is done or the battery discharged. This assists in avoiding loss of power from the apparatus before the work at the property, e.g. meter change, is finished.

A further option is protection against extreme shock, such as the apparatus being dropped; in the event of extreme shock a switch is tripped, disconnecting the battery, and the apparatus cannot be used until this has been reset. For when it is desired to reconnect the grid mains it is optional for the apparatus to comprise a reconnect arm switch. This activates circuitry in the apparatus, e.g. its control software, so the apparatus anticipates an imminent restoration of grid mains. For example, this may prompt the apparatus to ensure it is synchronized with grid mains - during disconnection the AC from the apparatus can become out of sync with the grid. One way to achieve this is to locate a phase resynchronization probe in association with the grid mains cables, e.g. on meter terminals, and linked to the grid- tied inverter, which adjusts the AC from the inverter (if necessary) to be synchronized with the grid; when the mains is reconnected this helps prevent a crash reconnection due to the respective ACs being out of phase. This feature is optional as it has been found that it is in practice effective to provide within the apparatus a detector of restored grid mains which when it does detect restoration of grid mains (e.g. by monitoring a combination of voltage and current) switches off AC from the apparatus. Even if there is some phase separation once the grid mains takes over there is nevertheless in effect no interruption to the property power supply; it is found that devices and lights remain connected to power throughout, a key advantage of preferred apparatus of the invention. Hence a further option, seen in preferred embodiments, is for the apparatus to be constantly ready for grid reconnection, and to revert to a charging mode once grid mains is restored.

Detection of grid mains may be achieved using conventional circuitry, e.g. incorporating a current limiter which switches off the apparatus AC output on an over current condition. In effect apparatus may include a circuit breaker to cut off power from the apparatus upon detection of mains grid. A combination of current limiter and circuit breaker may be used; the current limiter restricts the instantaneous current, whilst the circuit breaker disconnects the AC output in the event the inverter is slow to react. This will depend on the type of inverter being used. The power source may also comprise an anti-tamper switch which deactivates the power source if a user attempts to dismantle the power source or remove the case of the power source to access the batteries or other electronic components within the case. Source

The power source can be from a generator, e.g. petrol or diesel driven. The power source is preferably from a battery, and in general, all types of batteries with compatible output capacity are suitable for the source of AC power, such as lead- acid, lead-crystal, lithium ion, lithium polymer, and compatible with an associated charger if one is included in the apparatus. Additional batteries may be connected to the apparatus as an option to provide longer autonomy.

Power

For a given anticipated power consumption, more battery capacity will mean longer power output. Apparatus of the invention may be designed for various different uses, with different maximum output power available. To enable electrical work at a domestic location, a battery that can provide approximately 1 kilowatt hour of energy is suitable to allow, say, up to approximately 30 minutes or more of typical domestic power for using small electrical appliances and having lights switched on. As described elsewhere herein the apparatus may include a display to indicate battery level and/or an alert to advise that the battery is being consumed too quickly. The display may also be accompanied by a speaker to provide audible signals regarding the state of the device (e.g. low battery). The apparatus may have a socket to enable an additional battery to connect to it for longer autonomy. The apparatus may also include a plug to connect to a 12V power source to allow charging in a vehicle, e.g. further charging while being transported to its next destination. As battery technology develops smaller batteries with larger capacities will become available and will be suitable for the apparatus, improving these performances.

In typical use, again based on typical domestic power consumption research by the inventors, an apparatus may provide approximately 12-20 minutes of temporary battery power at each property visited during a single day and be used at up to 10 meter installations per day - noting that, at each property, when the installation of the meter is finished and the grid mains restored the apparatus can then be charged; at each new property prior to carrying out installation the apparatus can also be charged. Hence, in between use in meter installations (or other work requiring disconnection from grid mains) the apparatus battery can be charging. A data logger may also be included to record such parameters as duration of supplying power at each property, power consumption at each property, time to complete recharging and/or time between installations at respective properties.

A typical unit designed for 1 kW output can have a high output power alarm set for 1 kW output, being capable of safely generating twice that output, but with an overload cutout at e.g.1.5Kw (peak output current of -8.8A) leaving adequate safety margins.

Connect in Parallel

Preferred apparatus of the invention can be connected to the property electricity main in parallel with the grid main supply. An advantage is the apparatus is simply connected, e.g. plugged in, with no need to shut off the power; this can be contrasted with installation of a UPS device which sits in series with the equipment it powers and for which installation requires switching off power to the equipment or to the whole property. Further apparatus of the invention can additionally be connected to the same property, also in parallel. Hence, to provide more power to a given property or provide given power for a longer duration at the property two or more apparatus, a plurality, are connected to the property in parallel - a notable advantageous feature. For use where appropriate in any properties, especially in larger domestic properties and/or in SMEs without existing UPS devices installed, the invention enables provision of power using a plurality of apparatus. When used together, connection of the control systems of the respective sources is preferred to ensure all supply power to the property at the same time. A further option is for the batteries required to provide sufficient power during disconnection to grid mains to be housed in a small vehicle, such as a van or transporter.

In Use

As an example of the apparatus in use, an engineer brings an apparatus to the property in order to change an electricity meter. The engineer carries or wheels the apparatus into the property and plugs it into a standard socket, e.g. a standard mains double socket. The apparatus receives grid mains and starts to charge its batteries (if not fully charged). The engineer carries out preparatory work for the meter change. When this is complete the engineer ensures the apparatus is in a mode in which it will provide power to the property upon loss of grid mains. The engineer disconnects the property from the grid mains, usually a two step process in which the mains fuse is removed, and the main circuit breaker disconnected; upon loss of power for whatever reason the apparatus detects the loss of grid mains and switches on provision of AC power to the property. This occurs without power interruption for those at the property and is sufficient to provide power for a reasonable period for, say, lights and some low power devices. The engineer carries out the meter change and then reconnects the grid mains to the new meter; at this point the meter can be tested, if desired. With a valid mains supply present, the engineer can reconnect the property to the mains grid by reconnecting the main circuit breaker. At this point the apparatus detects the reconnection, ceases providing AC power to the property and reverts to a mode in which it is charging the battery from the newly reconnected grid mains; again, there is no power interruption. The apparatus is thus now recharging while the engineer completes the meter installation process, tidies up and completes post-installation work, and the apparatus will shortly be ready for the next installation at a different property.

Modes

The apparatus is suitably provided with one or more operating modes, for the user to select. One mode is "Charge only"; in this mode the apparatus will not provide power but charges its battery from grid mains. Another mode is "Generate only"; in this mode the apparatus will detect grid mains dropping out and switch to generating AC power for the property but will not charge its battery when the grid mains is connected. A further mode, in which the apparatus may generally be left as a default, is "Automatic"; in this mode the apparatus will charge from the grid when connected, will detect drop out of grid and switch to providing AC power and will detect reconnection of grid and switch off power generation and revert to charging its battery. In other embodiments, the apparatus comprises essentially a single mode in which it switches between states, e.g. between charging from the mains and supplying power to a property, dependent upon the inputs received from its connection to the property sockets rather than dependent upon manual mode selections; thus, for example in this single mode once plugged into the property sockets the apparatus charges and once it detects disconnection of the mains grid it switches to supplying power.

A preferred feature, nevertheless, is an "activate" option for the user via an input device (e.g. via a keypad, NFC reader or NFID reader as described above), whereby triggering this option places the apparatus is a sub-mode in which within a predetermined period of time it can switch to supplying power upon loss of mains power. Once the predetermined period is expired the apparatus will not switch to supplying power unless once again activated.

Typically, the sensor detects selection of the activated mode and maintains the apparatus in an activated mode for a time period of 2 minutes or less, for example 1 minute or less. In a specific embodiment, a sensor on the apparatus detects selection of the activated mode and maintains the apparatus in activated mode for approximately 30 seconds. This feature means a user can make the apparatus ready for a deliberate power disconnection while ensuring the apparatus is not permanently in the activated mode - as the activated mode can be unsafe in certain situations, especially if the apparatus is unsupervised for an extended period. For example, in the absence of an "activated mode" should grid mains power to the power source fail before the mains fuse has been removed or before the main circuit breaker has been opened (e.g. in the event of a power cut to the grid mains power), the power source would supply power to the entire grid network (e.g. to multiple properties rather than just the property in which the power source is located).

This risk is hence minimised by ensuring that the power source will only discharge power to the property if mains grid power to the power source is interrupted in the short space of time when the source is "activated". Features and Advantages

Apparatus of the invention hence provides a convenient portable power source that can be used to provide temporary electrical power to a property during work that requires disconnection from grid mains. Known UPS devices connect in series and have a socket for equipment to be powered; apparatus of the invention connect in parallel and don't require a socket. They just require a simple connection to the property mains power. In practice this can be achieved using a plug of the type used by devices to connect to the same circuit. Commonly these are standard 2-pin or 3-pin plugs. Preferably there are 2 plugs that must both be connected for the apparatus to function. Work at the property can be carried out without interruption to power supply. Such work can be carried out at night, extending the engineer's effective window. Such work can be carried out when people are in the property and using reasonable amounts of power; this use can be uninterrupted by the work e.g. at the electricity meter.

A notable advantage of the invention is that disconnection from and reconnection to the grid mains is enabled without any disruption in the power supply. During work on the property there can be effectively a seamless transition between the grid and the temporary source, meaning lights and devices with low power requirements can stay on continuously. An advantage of the invention is that the unit is designed to be connected in parallel with the power supply to the property from grid mains. It can be connected without having to disconnect any element of the existing power supply and circuitry. This can be contrasted with a UPS device, which is placed in series with a device/property it powers and protects.

The power source may also comprise an electronic transmitter/receiver for sending and/or receiving data (e.g. data collected by the data logger) from a remote server. The power source may also optionally comprise an internal clock and GPS so that it is able, for example, to transmit its location at a given time to the remote server. The transmitter may also be able to transmit information regarding the functioning of the power supply (such as changes in states and battery condition).

During work on the property that requires the power to be switched off, a power supply is now available for lighting for use by the engineer. Installation can take place in the evening as well as during the day. Installation can take place e.g. at weekends without disrupting family life.

Examples

The invention is now illustrated in specific examples with reference to the accompanying drawings, in which:

Fig. 1 shows a schematic, overview block diagram of the components of a power source according to a first embodiment of the invention;

Fig. 2 shows a schematic, detailed circuit diagram of the components of a power source according to a first embodiment of the invention;

Fig. 3 shows schematic views from the rear and side of a power source according to a first embodiment of the invention; Fig. 4 shows a schematic diagram of the electrical connection from a mains grid to a load connected to a power source of the invention;

Fig. 5 shows a graph of output power vs autonomy for a power source of the invention having approximately 600Wh battery capacity;

Fig. 6 is a schematic view of a power source according to a second embodiment of the invention;

Fig. 7 is a further schematic view of the power source according to the second embodiment of the invention; and

Fig 8. shows a schematic circuit diagram of the components of a power source according to a second embodiment of the invention;

First Embodiment

Power Source

Referring first to fig 3, an apparatus of the invention is a battery powered mains power source system to enable domestic electricity meter change without disrupting critical power to the house. It plugs into a UK domestic mains outlet socket using a conventional 3-pin plug connected to socket 12, is connected by pressing a connect switch, and while the grid mains is present charges its internal Li-ion battery.

In the event that the grid mains fails (or is switched off) the unit immediately switches on a mains generator circuit (inverter) powered from the internal battery, to provide 240V 50Hz mains power into the mains socket. When grid mains power is restored, the unit senses this and immediately switches back into a battery charging mode.

The unit has main body 17 within which are located the components described in more detail below with reference to fig.s 1 and 2. Its output is via two exterior mains cables with terminal plugs and attached to socket 12 - both must be plugged in, and the unit is designed so that if either of these is disconnected from the wall socket, the unit immediately switches off. This is to ensure that it is not possible to have live mains voltages present on the exposed pins of the mains plug(s). The unit cannot be switched on without both power plugs being connected.

There is detection of grid mains power. When the unit is in operating mode, generating mains voltages to power the home, it is possible for the grid power to be restored. The mains detection circuit detects this, preventing the unit from generating power to the grid, and preventing mains power surges into or out of the unit.

The unit has auxiliary battery connection 13 to permit the connection of an external battery for longer autonomy. The unit will charge this battery too if connected, when running on grid mains power.

The unit is rugged and portable with wheels 14 and handle 16 mounted on body 17 to assist in moving it about, with a total weight of approximately 25 Kg.

Referring to fig. 1 , the system 20 is constructed from 6 principal components, being a battery charger 2, a safety cut-out & overload protection 1 , a main unit battery 5, a safety disconnect 6, a control and user Interface 3 and an inverter (grid tie inverter, DC to mains) 4.

Referring to Fig. 2 for more detail, the system is isolated from the mains connectors (1 1 a, b) via relays RLY1 and RLY2. If mains is present on both mains inlets, the connect button (22d) can be pressed to energise both relays, which then remain energised by the mains powering isolated PSUs (22c). This provides a safety feature to disconnect the output in the event that one or other of the mains plugs is removed. With the system connected, the mains is sensed by the Grid-Tied Power inverter (26) and synchronised to it. Power is not generated at this stage, and with a mains power available indicator to the control unit (25a), If the Power/Mode switch (25b) is in the Charge or Auto position, the battery charger (21 ) is switched on, charging the batteries (23), and illuminating the Charging LED (25d). With this unit, it will not generate mains AC without the Arm switch (25i) being pressed first. When the Arm switch is pressed, the ARM light (25f) illuminates, indicating that on loss of mains, the system will seamlessly supply mains power to the output. If mains input is lost without the arm switch being pressed, the unit simply switches off and disconnects, requiring manual reconnection.

When supplying mains power, the control unit (25a) illuminates the Generating LED (25e) indicating the output is live. On reconnection of the mains one of two things happens: either the circuit breaker U3 (22a) disconnects the Inverter from supplying power - the inverter sends a message to the control module that this has occurred, and battery charging can resume if permitted by the position of the mode switch. Alternatively, the circuit breaker U3 will not disconnect, however the inverter will sense the mains present, and cease generating power, indicating this to the control module, allowing battery charging to resume if permitted by the position of the mode switch. If the circuit breaker opens, this has to be manually reset, which can be done at any time. Circuit breaker U4 (24) is a safety breaker for extreme overloads, and designed to open in the case of severe trauma (e.g. the unit being dropped down stairs) as a further safety measure.

Operating Features (on control panel, not all shown)

Power Switch (to turn the whole unit on and off Fig 2, 25b) .

Operating Mode switch (Fig 2, 25b) to select between Charge Only, Generate Mains Only and Automatic (auto-switches between charge / generate modes)

Battery status indicator - to provide an indication of how long the system will generate mains for.

Low Battery Alarm (Fig 2, 25g) - indicates when battery charge gets low

High Output Alarm (Fig 2, 25h) - indicates when generated mains power is above a key threshold

Overload cut-out (Fig 2, 22a) - switches the unit off / disconnects the mains output if an overload condition occurs.

Charging indicator (Fig 2, 25d) - shows unit is charging the battery from the grid mains, and/or shows charge rate.

Output Indicator (Fig 2, 25e) - shows the unit is generating mains power and/or indicates load output rate. Safety Features

Over / Under voltage protection (part of the battery charger 21 )

Output overload protection (part of Power Inverter 26 and safety and overload circuitry 22a, b, c)

Free-plug safety interlock (prevents live mains on exposed plug pins - part of safety and overload circuitry 22a, b, c)

Extreme shock protection (disconnects battery in the event of extreme shock to prevent possible shorts 24)

Arm switch to prevent accidental generation to mains grid in the event of incoming mains failure 25i

Overload protection 22 and re-sync circuitry within the power inverter 26 to prevent shock overload on reconnection of mains System Block Diagram

Referring generally to both Fig.1 and Fig.2, the interface Safety Cut-out and Overload Protection unit determines that the unit is plugged into a consumer mains outlet via its two cables. A small isolated current is passed from the live pin of one plug to the live pin of the other plug, and used to provide an indication that both plugs are connected to a mains socket. This enables the unit to be switched on and to charge the battery if mains is present, or to generate mains if the grid mains is disconnected. Overload protection is included via a circuit breaker 22a, so that in the event of a fault, the unit is safely disconnected.

The Battery Charger is under control from the Control and User Interface module and is switched on if the unit is in charging mode when grid mains is connected. It can safely charge the battery at a rate up to 3 x the battery capacity if the battery can tolerate it. Once the grid mains is restored, the internal battery is charged up as soon as possible ready for the next generation cycle.

An option (not shown) is to include a 12V input to the battery charger, so that the unit may charge the internal battery from a vehicle also.

The Control and User Interface module is at the heart of the unit. It allows the user to select the operating modes for the unit, typically via keyswitch:

Charge only - the system will draw power from the grid mains and charge the internal battery. If the grid mains fails, the unit simply switches off the charger without switching on the Inverter.

Generate Only - the unit will generate mains power to the output from the Inverter drawing power from the internal battery. If grid mains is present, the unit will switch off the Inverter and sit in an idle state.

Automatic - the unit automatically switches between charge and generate states according to the state of the Grid Mains.

The Control and User Interface may also have indications of:

Mains connection and Grid Mains Present

Charge and Charging rate

Mains Generation and Output rate

Battery charge status High output alarm (beeping sound and/or light)

Low Battery state (different beeping sound and/or light)

Overload disconnect (requires a reset from the operator) The inverter generates a mains AC voltage, drawing power from the system battery. The inverter is designed to sense the output voltage and current and to ensure the output remains within safe values, determining if grid mains is present or not and sending this indication to the Control and User Interface. The Inverter is a derivative of a Grid-Tied Inverter system such as used on Solar PV systems. It is modified such that it synchronises with the grid mains, and does not generate power whilst grid mains is present. When grid mains is lost, it is designed to freewheel, generating (for the UK) a nominal 230v AC at 50Hz, providing output power as required. This is exactly opposite to the conventional operation of a Grid-Tied Inverter, as generally they are designed to be completely synchronous with the mains shutting down if the grid mains is lost. The unit is prevented from generating power to the mains grid circuit in the event of external grid loss (i.e. a fault condition on the mains grid) by user training, and the disconnect arm switch needing to be pressed before disconnecting the grid mains.

The battery is a conventional battery of typically either Lead Crystal or Lithium-Ion chemistry. The capacity is chosen such that it is able to provide a maximum output to power the inverter to generate Mains AC Voltages and Currents as required. Typically this is >600 Watt-Hour capacity; fig. 5 is a de-rating curve that shows output time vs. output power for a battery with approximately 600Wh capacity. The battery selected is designed for a maximum output, and also for a maximum charge rate, such that in typical use, the system charge / discharge ratio is typically between 1 :2 and 1 :3.

The Safety Disconnect is an optional feature and included in this version of the power source. It prevents any disastrous consequences of battery misuse, fault, or overload. This may include a disconnect device such that excessive vibration or shock will disconnect the battery in the event of the system suffering trauma (for example being dropped down a flight of stairs). A manual reset is required if this disconnect system has been triggered.

Operation The unit is designed to provide temporary power to the home to keep up lights and other equipment whilst an electricity meter is changed.

The unit is plugged into a pair of mains sockets, and automatically provides power to the home when the mains circuit breaker is tripped. The incoming mains fuse can then be pulled out effectively isolating the meter from any mains AC. The meter can then be safely removed and replaced with a new one. The incoming mains fuse is replaced, and the meter checked for power. A re-sync probe is used (if fitted) to check mains is present and sync the inverter to the incoming mains. Once synchronised, an indication from the unit declares it is safe to reconnect the mains and it reverts to battery charging. An option for a power source version 2 is to include protection to allow instant re-connection to the mains without the re-sync probe.

The unit is designed to be as simple as possible to operate. There are essentially 3 states:

1 Charging

When the unit is plugged into the mains wall socket and switched on, it starts to charge the main batteries - if these are already charged, the batteries will be topped up. A battery charging light (if fitted) illuminates to indicate the charging status, together with a battery status indicator (if fitted) showing the charge remaining in the batteries. 2 Autonomy

Once armed (via a switch), then on disconnection of the incoming mains, the unit reverts to supplying mains to the property on condition that both mains plugs are connected. If one or other of the mains plugs are turned off, or disconnected the unit switches off.

The unit continues to supply mains power, giving warning of a low battery condition (if warning indicator is fitted), and switching off automatically if the battery is exhausted (low voltage disconnect), or if an overload condition exists. The unit gives an Indication (if fitted) of the output power being supplied together with an indication (if fitted) of remaining battery time. The unit also provides a warning (if warning indicator is fitted) of an abnormally high output power indication leading to short autonomy times. 3 Reconnection

To provide a safe reconnection to the incoming mains supply, a mains probe is used to detect the incoming mains supply at the meter before the main circuit breaker to the house is switched on. The unit provides an audible and visual OK signal to indicate it is safe to switch the main circuit breaker back on. This probe is used to sense the incoming mains, and provides 2 important safety features:

Prevent connection & power to the grid in the event there is no incoming mains Synchronisation of mains to prevent surges / overload conditions.

Once reconnection is safely achieved, the unit can revert to state 1 : Charging. Smart Meter Installation

Referring to fig. 4, the power source is used for a smart meter 28 installation as follows.

The power source 10 is connected in parallel with the grid mains connection 29 to the loads 30 at a domestic property. The source is plugged in and charges its batteries (unless already charged, in which case a trickle charge is provided to ensure the batteries remain fully charged). It is available to provide AC power to the property. Next, the disconnect arm switch is pressed, and the grid mains is disconnected from the property by breaking the connection at 31 b (between meter and property - preferred) or 31a (between mains and meter) and at that point the power source assumes providing AC power. The other of 31a and 31 b is then also disconnected, isolating the meter which is then replaced by a smart meter.

After installation main circuit breaker 31a is reconnected so that the new meter can be tested and once this is complete, and a valid incoming mains supply is determined, main fuse 31 b is reconnected, at which point provision of power to the property is once again from grid mains and the power source stops generating AC power and reverts to charging status. As it is connected in parallel the source can be unplugged, again without interruption to power to the property, and used for the next smart meter installation elsewhere.

Second Embodiment The invention also provides a further apparatus according to the invention, as shown in Figures 6 to 8.

The device generates a mains output power supply (for the UK = ~240vAC @ 50Hz) to enable the continual provision of mains power to a home for the duration of a mains electricity meter change.

As shown in Fig.6 and Fig. 7, the device comprises a casing (30) in which the electronic components of the device are housed. The casing is provided with a first extendable handle (36a), a second handle (36b) and wheels (not shown) to facilitate transport of the device.

The casing comprises a main body portion (32) and a lid (34) which are connected via hinges to allow the user to open the lid and access the interior of the casing. The casing also comprises four clasps (38) for ensuring that the lid remains closed during transport of the device.

Fig. 6 shows a view of the interior of the casing (30) when the lid (34) is open. From this, the plugs (1 1 a, 1 b), the Display (27) and RFID Reader (25a) can be seen.

Fig. 8 is a schematic circuit diagram showing the electronic components housed within casing (30).

The device comprises a conventional lithium-ion battery (23), chosen such that is able to provide a maximum output to power the inverter module (26) to generate mains AC voltages and currents as required (for the UK ~240vAC at 50Hz). Typically, this is sufficient to generate an output of around 1 kW for 10 minutes, with a maximum output of around 1 .5kW. The battery (23) selected is designed for a maximum output, and also for a maximum charge rate, such that in typical use, the system charge to discharge ratio is typically between 2:1 and 3:1. The battery (23) is also chosen for safe operation under all normal eventualities. An example of a battery suitable for use in the device is manufactured by Ronda Batteries (Model 18650, 14.8V, 5600 mAh Li- Ion pack; 6 of these batteries being arranged as 3 parallel strings of 2 batteries in series, i.e. forming a 29.6v battery of 16,800mAh capacity). The device also comprises an Inverter Module (26) comprising an inverter/charger which is able to act both as an inverter to convert the DC power provided by the battery (23) into AC power for supplying to the property as well as a charger for using the AC grid mains power to charge the battery. For use in the UK or elsewhere in Europe, the inverter is able to provide an AC power output of a true sine wave having a voltage of 230V (+1-2%) at a frequency of 50Hz (+/-0.1 %). An example of a suitable inverter/charger is available from Victron Energy (Module: Multiplus C24/800/19), having an AC output which is adjustable in the ranges 210V to 245V and 94V to 143V at either 50Hz or 60Hz depending on the variant. It will readily be appreciated that for use in other countries, the inverter is set or selected to provide the correct voltage and frequency to match the grid power supply in that country (e.g. US - 120V, 60HZ; Japan - 100 V, 50Hz 60Hz).

The device also contains an electronic Control Module (25) which receives electrical inputs from a variety of sensors of the device (e.g. Sense 1 , Sense 2, Safety Detect, NFID or Keypad (25a)) and sends electrical outputs to the inverter/charger, display and other components of the device (e.g. Display (27), Beeper, GSM Module). An example of a suitable control module is manufactured by HAOYU (model HY- LPC1 788-CORE).

The device is connected to the mains via a conventional double mains wall socket using two mains cables and plugs (1 1 a, 1 1 b). If either of these are disconnected from the wall socket, the unit immediately switches off. This is to ensure that it is not possible to have live mains voltages present on the exposed pins of the mains plugs. The device cannot be switched on without both power plugs being connected.

As can be seen from the schematic electrical diagram (Fig. 8), when the two mains input connectors (1 1 a, 1 1 b) are connected to the household ring main, power is sensed via the two transformers Sense 1 and Sense 2. These are used to wake up the processor in the Control Module (25a) which then analyses the mains voltage frequency and relative phases. Assuming that the mains voltage is within limits and the phase of the two mains connections is matching, the Control Module (25) enables the Safety Disconnect Relay 2 (22b) and powers the Isolated DC-DC converter to connect the Safety Disconnect Relay 1 (22a). If a loop mains connector to mains connector exists, this is sensed by the Safety Detect Opto-lsolator. If one of the mains connection cables (11a, 11 b) are removed from the wall socket, the DC current through the live connections (from the isolated DC-DC converter and Relay 1 coil) is broken, and Relay 1 (22a) is released disconnecting the Inverter Module (26) from the mains grid power. The Safety Detect Opto-lsolator indicates this to the Control Module (26) which in turn releases the Safety Disconnect Relay 2 (22b). This disconnects the unplugged mains pins from the other mains connection, ensuring that the exposed pins are voltage free and safe.

The device is protected from use by unauthorised individuals by means of an RFID card/tag reader (25a). As an alternative to the NFID Reader, a keypad may be used.

An RFID card is issued to a trained operator and is verified to the unit via a data link. Presenting the RFID card enables the unit to be put into a power generation mode. Without the RFID card being presented, the unit will only be able to charge the internal batteries.

Presentation of an authorised RFID card to the reader activates the device for a set time period (e.g. 30 seconds). In this activated state, the device will discharge its battery power to the property (through the two mains cables and plugs ( 1 a, 11 b)) when it detects that the main grid power has been disconnected. If the set time period elapses without the mains grid power from being disconnected, the device will revert to its charging only mode. If the mains grid power is disconnected without the device being activated, the unit will simply switch to standby. This prevents the system from inadvertently generating power to the grid before the user wishes for the device to provide power to the property.

The device also comprises a Display Panel (27) and a beeper, which may indicate to the user:

• Mains connection and Grid Mains Present

· Mains voltage and frequency

• Battery Charging rate and status

• Mains Generation Time and Output current / power

• Estimate of "Time to Discharged" when providing power

• Estimate of "Time to Charged" when charging

· Internal temperatures

• High output alarm (with beeping sound) • Low Battery state (with different beeping sound to high output alarm)

• Overload disconnect

The unit features an internal clock and GSM based communications module. This enables it to record details about its operation at preset time intervals and when a change of state occurs whilst it is switched on. System operation data is recorded by the device at preset time intervals (e.g. every 10 seconds) whilst powered up and also when a change of state occurs.

• Regularly recorded data points e.g.:

o Serial Number, User and Location

o Mains status (connected, Voltage, Frequency, Input /Output power) o Temperatures (internal, battery etc.)

o Battery status (voltage, current, charge state)

• State change

o Time & Date with above data and:

o New State (Mains connected, Charging, Enabled, Autonomy, Low battery, High Current, Over Current Disconnect, Fault, Power Standby)

The device is programmed to send usage data at preset intervals (e.g. once per day at set time or once per week etc.) to a remote server and also to receive commands from the server.

The device has a weight of 25kg or less and is portable with wheels and a handle to assist in moving the device. The total weight allows it to be handled by one person.

In use, the device is plugged into a pair of mains sockets and provides power to the home when the mains circuit breaker is tripped. The incoming mains fuse can then be pulled out, effectively isolating the meter from any mains AC. The meter can then be safely removed and replaced with a new one. The incoming mains fuse is replaced, and the meter checked for power (see Fig. 4).

The device automatically detects reconnection of the grid mains power and prevents excessive current in or out of the device on in the case of a crash re-connection of grid mains. By doing so, the device prevents generation of power to the connected mains grid. When the device is plugged into the mains wall socket, this is detected by current supplied to the device from the mains grid. If a valid connection to mains is detected, the device will switch on and conduct a number of tests to ensure that the mains grid power being supplied to the device is within predetermined tolerances (e.g. voltage, frequency). Once the device has determined that the mains grid power is within predefined tolerances and is therefore acceptable, it will start to charge its main batteries (if these are already charged, the batteries will be topped up / trickle charged to ensure that they remain fully charged). A battery charging indicator on the Display (27) shows the charging status, together with a battery status indicator showing the charge remaining in the batteries.

With the correct mains applied, the Control Module (25) will then connect the Input Relay (23a) to the Inverter Module (26), which will perform its own mains sensing, matching phase, and beginning to charge the battery (23). The device is then in the basic charging mode and ready to be activated.

The display at this point indicates charging and the Control Module (25) will be looking for a valid RFID security card (or valid PIN code if a keypad is fitted) to go into charge mode.

The device is designed to be operated by trained personnel only, and as such requires a valid RFID card to be presented for it to be used. This device is able to download a list of authorised RFID cards via a secure data link to an authorising server and therefore only RFID cards which have been remotely authorised on the server are able to activate the device. Without this authorisation, the device will not switch to discharging mode.

If an RFID security card input is read, the Display (27) will begin a countdown timer (typically 30 seconds) which is the time in which the operator will have to disconnect the incoming mains via the Main Fuse to the property (Fig. 4, 31 a), or the Main Input Circuit Breaker (Fig. 4, 31 b). If the mains grid power is not disconnected within the countdown timer, the Control Module (26) will issue beeps to the beeper to indicate the end of the countdown and revert to the simple charging state. If the mains grid power is disconnected from the device at this point will simply cause the unit to shut down. The activated state is entered into only when a valid RFID card is presented to the RFID reader (25a). This state will only last until either 30 seconds has elapsed since the RFID card was presented unless the incoming mains is switched off within this 30 second window, in which case the discharging state is entered. In the activated state, the Battery (23) of the device are still being charged from the mains supply.

With the mains power disconnected within the enabled countdown timer, the Inverter Module (26) will simply supply mains power out to the mains connectors (11a) via the Safety Disconnect Relay 1 (22a). The device then provides power to the property and will continue to do so until either: a) mains grid power is restored, (b) the Battery (23) is exhausted, or (c) the output power limit is exceeded and the unit shuts down.

During discharging mode, the Display (27) will show remaining estimated time at the current power drain, output power, and other information, with beeps providing a rough audible indication of output power (faster beeps = higher power).

When incoming grid mains power is restored, the Inverter Module (26) limits any excess current from a phase mismatch, and rapidly realigns to the new grid mains phase, eventually reverting to battery charging.

Once activated (with a valid RFID card), upon disconnection of the incoming mains supply, the device will discharge its batteries to the property, provided that both mains plugs (11 a, 11 b) are connected to the wall socket. If one or other of the mains plugs are turned off, or disconnected, the unit will switch off the output, with an indication, and after a time revert to a standby mode.

The device will continue to supply power to the property until one of the following events occurs:

• Output current draw limit is exceeded (unit turns off)

· Excessive internal temperature is reached (high temperature alarm is indicated first, both on the Display (27) and through the Beeper)

• Internal Battery voltage is too low (low battery alarm is indicated first, both on the Display (27) and through the Beeper)

• Incoming Grid Mains is restored (device reverts to Battery Charging mode) During discharging, the device provides the user of an indication of the output power being supplied together with an indication of remaining battery time at the current load via Display (27). When this estimated remaining time falls below 3 minutes, the device gives an audible and visual warning of low battery life. A warning (audible and visual) will also be provided in the case of an abnormally high output power.

When grid mains power is reconnected to the property, the device detects this. The device then suspends discharging its battery power and reverts to charging the battehes from the grid mains power.

This re-connection tolerates with random Mains Phase difference between generated Mains and incoming Grid Mains, including 180° out of phase.

To provide a safe reconnection to the incoming mains supply, the device prevents surges to and from the grid mains via internal current limiting. When the device is discharging mains voltages to power the property, it is possible for the mains grid power to be restored at random. The device is designed to limit the power flowing in or out of the system, preventing mains power surges into or out of the device when the mains grid is restored. The system will synchronise with the incoming mains grid power and revert to battery charging.

After disconnection from the property, and a programmed interval has elapsed, the device reverts to a low power state, minimising power draw to conserve battehes. The device will wake up the GSM module at pre-determined intervals for checking messages / communications etc., and automatically switches on upon re-connection to the mains. The Low Power State, should be sufficient to remain operational for at least 4 weeks.

The invention hence provides a power source and a method of installing a meter at a property using the power source while providing uninterrupted power to the property.