GB2465638A

GB2465638A - Current measuring device and system for monitoring energy usage

Info

Publication number: GB2465638A
Application number: GB0904324A
Authority: GB
Inventors: Mike Bird; Chris Poulton
Original assignee: ENERGENO Ltd
Current assignee: ENERGENO Ltd
Priority date: 2009-03-13
Filing date: 2009-03-13
Publication date: 2010-06-02
Anticipated expiration: 2029-03-13
Also published as: GB0904324D0; GB2465638B; WO2010103332A1

Abstract

A device 5, 6 for measuring current comprises sensor means for measuring amplitude and/or change in phase, means for generating a message in response to a change in these values, and means for sending the message to a server 9. The message includes information about the amplitude and/or the change in phase of the alternating current. The message may also include the time the change occurred, or the identity of the device. The message may be sent using a wired or wireless protocol to a gateway. A phase lock loop may be employed to generate an output signal. The server is configured to receive the message and determine energy usage from the information. A gateway 7 may be provided to send and receive messages from the server and the devices. Switching means may be included in the device to be controlled in response to messages from the server. The system allows energy usage to be attributed to specific appliances.

Description

Current measuring device

Description

The present invention relates to a current measuring device, particularly but not exclusively for use in monitoring energy usage.

Information about electrical energy usage in the home and in commercial buildings is extremely valuable. Not only is this information important to energy companies for billing, planning, etc., it can also be used by individuals for a number of different purposes. For example, individuals can analyse their energy usage in order to identify ways of increasing efficiency, such as by changing patterns of usage, replacing appliances and/or switching energy tariffs.

Thus, it can be useful to provide energy usage information which is detailed and/or provided in real time or near real time and which can be analysed appropriately and communicated to an appropriate recipient. For systems which are to be used by individuals rather than electricity companies, there may also be considerations relating to cost, ease of installation and ease of use.

Several factors to consider include: the number and placement of sensors, how these sensors measure energy usage, how the energy usage information is analysed in the various parts of the system and how the information is communicated between these various parts.

Systems for capturing information about energy usage are known.

US-A-4,858,141 describes a monitor in which analogue voltage and current signals are converted to digital format, processed to detect changes in certain residential load parameters, and logic is applied to identify individual appliances.

WO-A-2003/055031 describes a system for the remote acquisition of data and for the remote control of electricity meters which comprises a central server in bi-directional communication with a plurality of concentrators. To each concentrator, a set of electricity meters is connected. The intelligence of the system is distributed between the central server, the concentrators and the electricity meters.

GB-A-2451001 describes a smart metering system comprising an information display unit coupled for communication with at least one metering device and a memory device, for example by low power radio. The information display unit displays graphically or otherwise instantaneous energy consumption, historical energy consumption, etc. The present invention seeks to provide an improved system.

According to a first aspect of the present invention, there is provided a device comprising means for measuring amplitude and/or change in phase of an alternating current in a section of wiring, means for generating a message in response to a change in the amplitude and/or a change in the phase of the alternating current, the message including information about the amplitude and/or the change in phase of the alternating current, and means for sending the message to a server.

Thus, the device can provide pertinent information efficiently to a server, enabling analysis of energy usage by one or more electrical devices powered via the section of wiring. A single device or network of devices can then be used to flexibly monitor energy usage in a site such as a home or commercial building.

The generating means may be configured to include in the message information about the change in amplitude and/or the change in phase of the alternating current occurred. The generating means may configured to include in the message information identifying the device. The generating means may be configured to generate the message in response to a change of at least a predetermined level in amplitude and/or a change of at least a predetermined level in phase of the alternating current.

The sending means may be configured to send the message via the wiring to a gateway. The sending means may be configured to send the message according to a power line communication protocol. The sending means may be configured to send the message via a wireless communication link to a gateway.

The measuring means may comprise a phase lock loop configured to generate an output signal in response to a change in phase of an alternating current input signal.

The phase lock loop may comprise means for generating an error signal which is dependent on the difference between an input signal and a feedback signal, means for integrating the error signal, and means for generating the feedback signal with a frequency which is dependent on the integrated error signal, wherein the phase lock loop is configured so that the feedback signal varies until it has the same phase and frequency as the input signal, and wherein the output signal is the integrated error signal. The device may further comprise means for converting the output signal from an analogue to a digital signal.

The device may further comprise switching means and means for controlling operation of the switching means in response to receiving a message from the server including an instruction about operation of the switching means. The generating means may be configured to include in the message to the server information about status of the switching means.

According to a second aspect of the present invention, there is provided a device comprising a sensor configured to measure amplitude and/or change in phase of an alternating current in a section of wiring, a controller configured to generate a message in response to a change in the amplitude and/or change in the phase of the alternating current, the message including information about the amplitude and/or the change in phase of the alternating current, and a network interface configured to send the message to a server.

The sensor may comprise a phase lock loop configured to generate an output signal in response to a change in phase of an alternating current input signal.

According to a third aspect of the present invention, there is provided a server configured to receive a message from a device, the message generated in response to a change in amplitude and/or a change in phase of alternating current in a section of wiring and the message including information about the amplitude and/or the change in phase of the alternating current, and determine, from the information about the amplitude and/or the change in phase of the alternating current, the energy usage of one or more electrical devices powered via the section of wiring.

The message may include information about the time when the change in amplitude and/or the change in phase of the alternating current occurred and wherein the server is configured to determine the energy usage of the one or more electrical devices from the information about the time when the change occurred.

The server may be configured to calculate the phase difference between voltage and current in the section of wiring by comparing the information about the change in phase of the alternating current with information about the change in phase of the alternating current at one or more earlier times.

The server may be configured to store an energy usage profile of one or more of the electrical devices, the energy usage profile including information about the amplitude and/or the phase of the alternating current at one or more times. The server may be configured to assign the change in amplitude and/or the change in phase of the alternating current to one or more of the electrical devices by determining whether the change in amplitude and/or the change in phase of the alternating current at one or more times matches any of a plurality of energy usage profiles of electrical devices. The server may be configured to read one or more of the plurality of energy usage profiles of electrical devices from a database.

The server may be configured to determine whether energy usage by one or more of the electrical devices matches any of a predefined plurality of energy usage conditions and, in response to matching the condition, send a message to a device comprising switching means, the message including an instruction about operation of the switching means. The server may be configured to determine whether energy usage by one or more of the electrical devices matches any of a predefined plurality of energy usage conditions and, in response to matching the condition, send a message to a user.

According to a fourth aspect of the present invention, there is provided a system comprising one or more of the devices and a gateway, wherein the gateway is configured to receive the messages from the one or more devices and to send the messages from the one or more devices to the server.

The system may further comprise the server, wherein the gateway is configured to receive the messages from the server and to send the messages from the server to the one or more devices.

The gateway may be configured to store the messages from the one or more devices and/or the messages from the server for sending at a later time.

According to a fifth aspect of the present invention, there is provided a method comprising measuring amplitude and/or change in phase of an alternating current in a section of wiring, generating a message in response to a change in the amplitude and/or a change in the phase of the alternating current, the message including information about the amplitude and/or the change in phase of the alternating current, and sending the message to a server.

The message may further include information about the time when the change in the amplitude and/or the change in phase of the alternating current occurred.

The method may comprise sending the message in response to a change of at least a Jo predetermined level in the amplitude and/or a change of at least a predetermined level in the phase of the alternating current.

The method may comprise measuring the change in phase of the alternating current by phase locking.

The method may further comprise controlling operation of switching means in response to receiving a message from the server including an instruction about operation of the switching means.

According to a sixth aspect of the present invention, there is provided a method comprising receiving a message from a device, the message generated in response to a change in amplitude and/or a change in phase of alternating current in a section of wiring and the message including information about the amplitude and/or the change in phase of the alternating current, and determining, from the information about the amplitude and/or the change in phase of the alternating current, the energy usage of one or more electrical devices powered via the section of wiring.

The method may comprise storing an energy usage profile of one or more of the electrical devices, the energy usage profile including information about the amplitude and/or the phase of the alternating current at one or more times. The method may comprise assigning the change in amplitude and/or the change in phase of the alternating current to one or more of the electrical devices by determining whether the change in amplitude and/or the change in phase of the alternating current at one or more times matches any of a plurality of energy usage profiles of electrical devices.

The method may comprise determining whether energy usage by one or more of the electrical devices matches any of a predefined plurality of energy usage conditions and, in response to matching the condition, sending a message to a device comprising switch means, the message including an instruction about operation of the switching means. The method may comprise determining whether energy usage by one or more of the electrical devices matches any of a predefined plurality of energy usage conditions and, in response to matching the condition, sending a message to a user.

According to a seventh aspect of the present invention, there is provided a computer program comprising instructions which when executed by a data processing apparatus perform the method.

According to an eighth aspect of the present invention, there is provided a computer-readable medium storing the computer program.

Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 shows an energy monitoring system in accordance with the present invention; Figure 2 is a schematic block diagram of a meter sensor in accordance with the present invention; Figure 3 is a schematic block diagram of circuitry included in the meter sensor shown in Figure 2 for measuring a change in phase of an alternating current; Figure 4 illustrates examples of input and output signals of the circuitry shown in Figure 3; Figure 5 is a schematic block diagram of a messaging manager included in the meter sensor shown in Figure 2; Figure 6 is a flowchart illustrating an example of a method by which the messaging manager shown in Figure 5 monitors an alternating current; Figure 7 is a schematic block diagram of a socket sensor in accordance with the present invention; Figure 8 is a schematic block diagram of a messaging manager included in the socket sensor shown in Figure 7; Figure 9 is a schematic block diagram of a gateway in accordance with the present invention; Figure 10 is a sequence flow diagram illustrating an example of energy monitoring and control in accordance with the present invention; Jo Figure 11 is a schematic block diagram of a server in accordance with the present invention; and Figure 12 illustrates examples of screenshots showing energy usage information produced by a user interface module included in the server shown in Figure 11.

Referring to Figure 1, a system I for energy monitoring in accordance with the present invention is shown. Alternating current (AC) electricity is supplied via wiring 2, such as electrical power cables, from a source 3 to one or more devices 4, hereinafter referred to as "appliances", which may consume electrical power.

Appliances 4 can include fridges, freezers, dishwashers, washing machines, televisions, other audio-visual equipment, computers, heating systems, lights and industrial machines, for example. A meter sensor 5 is coupled, for example inductively or conductively coupled, to a section of the wiring 2 between the source 3 and most or all of the appliances 4. For example, the meter sensor 5 is situated near the standard electricity meter (not shown). Electricity is supplied to appliance(s) via a corresponding socket sensor 6. Alternatively, appliance(s) 4m+i. . . may be powered via a path which does not include a socket sensor 6. The meter and socket sensors 5, 6 each communicate with a gateway 7 by way of the wiring 2 and/or a wireless communication link 8. The gateway 7 communicates with a server 9 via a router 10 and the Internet 11. A computer 12 can also communicate with the server 9 via the router 10 and the Internet 11.

The meter sensor 5 monitors current, hereinafter referred to as "meter current", supplied to the collection of appliances 4 and the socket sensors 6 monitor currents, hereinafter referred to as "socket currents" supplied to individual appliances 4. In particular, the meter and socket sensors 5, 6 each monitor the phase and amplitude of the alternating current. Whenever a meter or socket sensor 5, 6 detects a change in amplitude and/or a change in phase of a meter or socket current, it sends a message to the gateway 7. This message includes information, hereinafter referred to as a "reading", about the amplitude and/or about the change in phase of the meter or socket current. In turn, the gateway 7 sends a message including the reading to the server 9.

The server 9 stores the meter and socket current readings received from the gateway 7 in a database 58 (Figure 11) and analyses the data in various ways. For example, the energy consumption of each appliance m connected via a socket sensor 6 can be calculated. Furthermore, the energy consumption of each appliance 4m+i 4 not connected via a socket sensor 6 may be inferred from a comparison of one or more meter current readings with a set of readings that are characteristic of a particular type of appliance. A user can view the energy consumption and related data by using the computer 12 or a different device, such as a portable device, connected to the server 9. The user can also control actions which the system I may carry out in response to particular conditions. For example, a socket sensor 6 may be used to switch off the electrical power to a particular appliance 4 in response to its energy consumption exceeding a certain value in a certain period of time. In this case, the server 9 sends a message to the gateway 7 including information identifying a particular socket sensor 6 and a switching instruction.

The gateway 7 then sends a message to the particular socket sensor 6 instructing the socket sensor 6 to switch off the power to the appliance 4. Other actions which the system I may carry out include sending messages to alert the user about energy consumption levels, for example via email or short message service (SMS). The server 9 receives information from different gateways 7 associated with different users. The server 9 also performs additional functions such as updating the software in the gateway 7, meter sensor 5 and/or socket sensors 6. Further details of how the system operates will be provided below.

Referring to Figure 2, the meter sensor 5 is shown in more detail. The meter sensor has circuitry for measuring a change in phase of the meter current, including a signal conditioner 12, phase lock loop (PLL) 13 and an analogue-to-digital (A/D) converter 14, and circuitry for measuring amplitude of the meter current, including a signal conditioner 15 and an A/D converter 16. The meter sensor 5 may also include circuitry 17 for harvesting power from the meter current and circuitry for generating and sending messages to the gateway 7, including a messaging manager 18 and an isolating transformer 19. In the meter sensor 5 shown in Figure 2, messages are sent to the gateway 7 via the wiring 2. An alternative or additional way of sending messages to the gateway 7 via the wireless communication link 8 may also be provided.

The amplitude and phase-change measuring circuitry 12, 13, 14, 15, 16 and the power harvester 17 are coupled to a section of the wiring 2 by way of a current -10 -transformer 20 which is inductively coupled to the live wire 21, i.e., the wire carrying the electrical current from the source 3 to the appliances 4. For example, the current transformer 20 may include two C'-shaped ferrite core parts (not shown) which can be clipped together to form a closed core around the live wire, with one of the core parts wound by a wire which is operatively connected to the measuring circuitry. Other ways of inductively coupling to the live wire 21 may also be used, such as by using a differently shaped transformer 20. The transformer 20 and other parts of the meter sensor 5 may be located in the same physical housing or in separate housings. If separate housings are used, they may be connected using insulated wiring. In many domestic and commercial buildings, the live wire 21 and neutral wire 22 are located in separate cables in between the electricity meter and the fuse box, thereby facilitating coupling of the current transformer 20 to the live wire 21 by the user.

Referring also to Figures 3 and 4, the phase-change measuring circuitry includes the signal conditioner 12 connected to the PLL 13 which is, in turn, connected to the A/D converter 14. The signal conditioner 12 converts an AC current from the transformer 20 into an AC voltage which acts as the input signal to the phase lock loop 13. The PLL 13 includes three elements connected in series: a phase comparator 23, a loop filter 24 and a voltage-controlled oscillator 25. The phase comparator 23 compares the phases and frequencies of two signals (the input signal from the signal conditioner 12 and a feedback signal from the voltage-controlled oscillator 25) and generates an error signal which is a function of the phase difference and/or frequency difference between the two signals. The loop filter 24 integrates the error signal. The voltage-controlled oscillator 25 generates a signal whose frequency is a function of the integrated error signal and this signal is fed back to the phase comparator 23. The circuit provides a negative feedback loop wherein the feedback signal is varied until it has the same phase and frequency as the input signal, as shown in the region between t1 and t2 in Figures 4B and 4C.

When the PLL 13 is "locked" in this way, any changes in the phase and/or frequency of the input signal result in an integrated error signal from the loop filter 24. Thus, as shown in the region between t1 and t2 in Figure 4D, the integrated error signal is a dynamic measurement of any changes in frequency and/or phase of -11 -the input signal and, ultimately, of the electrical current in the wiring 2. Such frequency and/or phase changes will occur whenever the reactance of the load changes, as shown in Figure 4A, for example when an appliance 4 is switched on or off. The integrated error signal from the loop filter 24 is passed to the A/D converter 14, which converts, with a particular sampling rate, the signal to a digital signal and passes this to the messaging manager 18.

Referring to Figure 2, the amplitude measuring circuitry includes the signal conditioner 15 connected to the A/D converter 16. The signal conditioner 15 filters and/or otherwise conditions the AC current from the transformer 20 and passes a signal to the A/D converter 16. The A/D converter 16 passes a digital signal indicative of the amplitude of the meter current to the messaging manager 18.

Referring to Figures 2, 5 and 6, operation of the messaging manager 18 will now be described. The messaging manager 18 includes, for example, one or more processors, a system clock, volatile and non-volatile memory, a network interface and/or a transceiver. The messaging manager 18 receives signals indicative of the amplitude and the change in phase of the meter current from the current measuring circuitry (step S601). These signals are analysed by a current monitoring module 26 which determines whether there is a change of at least a predetermined amount in the amplitude and/or phase of the meter current (in the latter case, whether the signal differs from zero by at least a predetermined amount) (step S602). The predetermined amounts are chosen so as to ignore most or all changes which are due merely to electrical noise, etc., and not to the effects of any changes in operation of an appliance 4 or in the characteristics of the supplied power.

Additionally, filtering will be carried out by the server 9 (Figure 1) as described below. The signals are monitored until a significant change in amplitude and/or phase is detected (i.e., more than the predetermined amount), in which case a message generating module 27 generates a message including information about the amplitude and/or the change in phase of the meter current (step S603). The message also includes information indicating the present time and an identifier of the meter sensor 5. Identifiers of the message type and of the software version of the meter sensor 5 may also be included in the message, as well as any other -12 -information which may be useful. The message is formatted using a markup language such as XML, thereby allowing flexibility as regards the number of fields and their contents. The message generating module 27 may also encrypt all or a part of the message. A message sending/receiving module 28 then sends the message to the gateway 7 via the wiring 2 (step 5604). Messages may also be stored in memory for sending at a later time.

The message may be sent using a protocol stack comprising the HomePlug 1.0 protocol or any other suitable power line communication protocol. In this case, the signals are passed through the isolating transformer 19 to the wiring 2 via a direct electrical connection to the live 21 and neutral 22 wires. These connections may be achieved in various ways. For example, an assembly may be provided which can be clipped onto the cable and which includes a screw which can be moved so as to penetrate the insulating sheath of the cable and make electrical contact with the wire. Of course, the assembly must be arranged so that the making of the connections is a safe procedure for the user. Furthermore, the meter sensor 5 may be provided with an indicator such as a light-emitting diode (not shown) to indicate to the user when the electrical connections have been made. Alternatively, the messaging manager 18 may pass signals to the wiring 2 via, for example, a transformer which is inductively coupled to the wiring 2.

The message sending/receiving module 28 may also receive messages from the gateway 7 which include software update information. Such messages are passed to the software updating module 29 which will store and verify the information, and update some or all of the software stored in the meter sensor 5.

The meter sensor 5 may also be provided with an alternative or additional way of sending messages to the gateway 7 via the wireless communication link 8. The wireless communication may be carried out using any suitable wireless protocol, such as Wi-Fi, ZigBee or another standard or a proprietary wireless protocol. In this case, the meter sensor 5 will include hardware (not shown), such as a radio transceiver and an antenna, and the message sending/receiving module 28 will include suitable software (not shown). -13-

Referring to Figure 2, the meter sensor 5 includes power-harvesting circuitry 17 which is connected to the current transformer 20 and which includes rectifying and filtering circuitry or other suitable elements arranged to supply a suitable direct current (DC) voltage to the power the meter sensorS. Rechargeable batteries (not shown) may also be provided to act as a power reservoir. The meter sensor 5 may also be provided without power harvesting circuitry 17, in which case power may be obtained by any standard means. The meter sensor 5 may also include other components (not shown), such as indicators to indicate the status of the meter sensor 5 and/or buttons to control various functions such as resetting the meter sensor 5 or connecting to the gateway 7.

Referring to Figure 7, the socket sensor 6 is shown in more detail. The socket sensor 6 includes many of the same or similar elements as the meter sensor 5 (Figure 2). In particular, the socket sensor 6 includes a signal conditioner 30, phase lock loop 31 and A/D converter 32 for measuring the change in phase of the socket current, a signal conditioner 33 and A/D converter 34 for measuring the amplitude of the socket current, and a power harvester 35. All of these elements are generally arranged in the same way as described earlier in relation to the meter sensor 5. The socket sensor 6 has a plug 36 and socket 37 to enable the socket sensor 6 to be plugged into a power socket and to enable an appliance 4 to be plugged into the socket sensor 6. The plug 36 and socket 37 may be integral to the socket sensor 6.

In any case, the plug 36 and socket 37 are electrically connected via live 38, neutral 39 and (where used) earth 40 wires. In contrast to the meter sensor 5 (Figure 2), a current transformer 41 is generally located inside the device housing and is permanently coupled to the live wire 38. The current transformer 41 may include a dosed ferrite core around the live wire, wound by a wire which is operatively connected to the measuring circuitry and the power harvester 35. Other ways of coupling to the live wire 38 may also be used, such as, for example, a direct electrical connection.

Referring to Figures 7 and 8, the socket sensor 6 also includes a messaging manager 42 which, similar to that in the meter sensor 5 (Figure 2), is connected to the -14-measuring circuitry and is connected via an isolating transformer 43, to the live 38 and neutral 39 wires. In contrast to the meter sensor 5 (Figure 2), the electrical connections to the live 38 and neutral 39 wires are generally internal to the device housing and permanent. The socket sensor 6 may also include software and hardware (not shown) associated with an alternative or additional way of sending messages to the gateway 7 via the wireless communication link 8. The socket sensor 6 also has a switch 44, which is arranged so that it can make or break the part of the electrical circuit formed by the live wire 38, thereby enabling the power supply to an appliance 4 to be switched on or off. The switch 44 includes a solid-state or other type of relay and is operatively connected to and controlled by the messaging manager 42 as described below. The socket sensor 6 may not include a switch 44.

The messaging manager 42 includes a current monitoring module 45, message generating module 46, message sending/receiving module 47 and software updating module 48, which generally function in the same way as described earlier in relation to the meter sensor 5. However, the messages sent in response to a change in amplitude and/or phase of the socket current include additional information indicating the status of the switch 44, e.g., whether the switch is on or off.

Furthermore, the message sending/receiving module 47 may also receive messages from the gateway 7 which include instructions to switch on or off the switch 44.

Such messages are passed to a switching module 49 which responds by appropriately adjusting the control signal to the switch 44. The switching module 49 also provides information about the status of the switch to the message generating module 46.

The socket sensor 6 may also include other components, such as indicators and/or control buttons (not shown). Furthermore, in place of the switch 44, the socket sensor 6 may include circuitry arranged to set the power supply to the appliance 4 to a particular value between zero and a maximum value. Furthermore, the socket sensor 6 may be arranged so that it can be incorporated into an appliance 4. In this case, the socket sensor may not include the plug 36 or socket 37.

-15 -Referring to Figure 9, the gateway 7 is shown in more detail. The gateway 7 includes one or more processors 50, memory 51, network interface 52 and power line communication interface 53, operatively connected to each other by a bus 54.

The processor(s) operate under the control of software. The power line communication interface 53 is arranged to send and receive messages via the wiring 2 to and from the meter sensor 5 and socket sensors 6. The messages may be sent or received using a protocol stack comprising the HomePlug 1.0 protocol or any other suitable power line communication protocol. The gateway 7 includes a plug to enable it to be plugged into a power socket, thereby establishing the electrical connection with the wiring 2. Such a connection is also used for the power supply of the gateway 7. The gateway 7 may also include software and hardware (not shown) associated with an alternative or additional way of communicating with the meter and socket sensors 5, 6 via the wireless communication link 8. The network interface 52 includes a wired or wireless local area network interface, which is arranged to send and receive messages via the router 10 to and from the server 9.

These messages are sent and received using HTTP and TCP/IP protocols or any protocol or protocol stack which is suitable for communication with the server 9.

The gateway 7 is arranged to pass messages between the meter sensor 5 or socket sensors 6 and the server 9. Thus, the gateway 7 converts between the protocol stack related to the power line communication network and/or the wireless communication link 8 and the protocol stack related to the wired or wireless local area network. In addition, the gateway 7 may edit the headers and/or contents of any messages which are being passed, encrypt and/or decrypt messages, and/or it may combine a message with one or more other messages. However, analysis of meter or socket current readings etc. is generally performed by the server 9, as described below. When a message is received from the meter sensor 5, the gateway 7 may include an identifier of the gateway 7 in the message, may establish a TCP/IP connection with the server 9 and may send the message to the server 9 by using e.g. a HTTP POST method. In the event that a connection with the server 9 cannot be established, the gateway 7 may also store one or messages in memory 51 for sending at a later time. The gateway 7 may also carry out a corresponding process when passing messages from the server 9 to the meter or socket sensors 5, 6. In this case, -16 -the TCP/IP connection may be initiated by the server 9 or, alternatively, the gateway 7 may periodically connect to the server 9 and may receive any messages from the server 9 by using e.g. a HTTP GET method. Messages received from the server 9 may also be stored in memory 51 for sending to a sensor 5, 6 at a later time. The gateway 7 may also enable the user to change settings stored in the gateway 7, for example by connecting to a configuration web page. The gateway 7 can also receive messages from the server 9 including software update information and store, verify and use the information to update some or all of the software stored in the gateway 7.

Referring to Figure 10, an example of energy monitoring and control in accordance with the present invention is shown. At step 51001, a socket sensor 6 detects a change in amplitude and/or phase of the socket current and, at step S 1002, it generates a message which includes an identifier (Device_ID) of the socket sensor 6, an identifier (Message_ID) of the message type, the status (Switch_Status) of the switch, the amplitude of the socket current, the change in phase of the socket current, and the time. At step S 1003, the message is sent from the socket sensor 6 to the gateway 7, which establishes a connection to the server 9 at step S 1004 and sends the message to the server 9 at step S 1005, the message including an identifier (Gateway_ID) of the gateway 7. At step S 1006, the meter sensor 5 detects a change in amplitude and/or phase of the meter current and, at step S 1007, it generates a message which includes an identifier of the meter sensor 5, an identifier of the message type, the amplitude of the meter current, the change in phase of the meter current, and the time. At step S 1008, the message is sent from the meter sensor 5 to the gateway 7. At step S1009, the gateway 7 attempts to establish a connection to the server 9 but this attempt is unsuccessful because, for example, the server 9 is busy. Therefore, at step SlOb, the gateway 7 stores the message and, at step SbOll, reattempts to establish a connection to the server 9 and, after successfully doing so, sends the message, including the identifier of the gateway 7, to the server 9 at step S1012. At steps S1013 to S1017, a second socket sensor 62 detects a change in the socket current and sends a message via the gateway 7 to the server 9. At step S1018, the server 9 determines that the second socket sensor 62 should be switched.

Therefore, at step S1019, the server 9 sends a message to the gateway 7 including an -17 -identifier of the gateway 7, an identifier of the socket sensor 62 to be switched and a switching instruction. At step S 1020, the gateway 7 sends a message to the socket sensor 62 including an identifier of the socket sensor 62 and the switching instruction. At step S1021, the socket sensor 62 switches.

Referring to Figure 11, the server 9 is shown in more detail. The server 9 includes a web server module 56, a data storage module 57, a database 58, a data processing module 59, a user interface module 60, a monitoring module 61 and a device software updating module 62. The server 9 may include one or more server computers and/or hardware such as processor(s), memory, storage and network interface(s).

The web server module 56 sends information to and receives information from the gateway 7 (Figure 1), the computer 11 (Figure 1), and other devices (not shown) such as a user's mobile telephone, an administrator computer and an energy company server. The web server module 56 may also carry out other functions, such as processing of messages, encryption or decryption of messages, access control, etc. Messages from the gateway 7 (Figure 1) including readings of meter and/or socket currents are passed to the data storage module 57, which stores the readings in an appropriate location in the database 58 dependent, for example, on the identifier of the gateway 7 included in the message.

The data processing module 59 reads data from the database 58, analyses the data in various ways and stores the results of the analysis in the database 58. For example, the data processing module 59 can calculate the phase difference between current and voltage by combining a reading of a phase change with previous readings of phase changes. Readings may also be filtered and/or averaged. Averaging over short time periods, e.g., one or more power line cycles, may be used, for example, when identifying appliances. Averaging over longer time periods may be used, for example, to determine frequency drift in the power being supplied, e.g., due to peak demand in the electricity grid. A change in amplitude can also be calculated by -18 -comparing an amplitude reading with a previous reading. Values of time, phase difference and amplitude for a particular appliance 4 or collection of appliances 4 can then be used to calculate power consumption, which, in turn, can be used to calculate energy usage in a specified period of time. In this case, the amplitude of the voltage can be taken to have a constant value determined by the standard supply voltage, e.g., 120 V, 220 V or 240 VAC.

The data processing module 59 "learns" the typical energy usage of an appliance 4 (Figure 1). In particular, vectors comprising values of time, phase difference and amplitude for a particular appliance 4 are built up over a period of time to produce a typical operating envelope for the appliance 4. This information about typical energy usage is stored in the database 58 and may be shared between different users.

The database 58 may also store typical energy usage information obtained from other sources such as, for example, from the manufacturer of the appliance 4.

The user can assign a particular appliance 4 (Figure 1) to a particular socket sensor 6 (Figure 1) by using a web interface provided by the user interface module 60. An appliance 4 may be identified by inputting the name and type of the appliance 4 and/or selecting the appliance 4 from a predetermined list. Any such information is stored in the database 58. Socket sensors 6 may be labelled so that they can be easily identified by the user. Thus, a user can obtain typical energy usage data for a plurality appliances 4 by successively connecting these appliances 4 to a single socket sensor 6. The learning process may also be interactive, with the user prompted to switch an appliance 4 off or on. Such an interactive learning process may also be used to obtain typical energy usage data for appliances 4 which are only connected via the meter sensor 5 (Figure 1), such as lighting, central heating systems, etc. The data processing module 59 uses typical energy usage data from the database 58 in various ways. For example, a typical operating envelope can be compared with new data to detect a potential malfunctioning of an appliance 4 (Figure 1).

Furthermore, a typical operating envelope can be used to automatically identify devices which have been connected via either a meter or socket sensor 5, 6 (Figure -19 - 1). Particularly in the case of data originating from the meter sensor 5, each reading will be associated with energy usage by one or more of a plurality of appliances 4.

In this case, the data processing module 59 will compare one or more readings with typical energy usage data for a series of devices in order to attempt to assign with a reasonable degree of certainty a particular reading to a particular appliance 4. The assignment or classification process may also take into account other factors such as correlations with readings from socket sensors 6 and any information provided by the user. Generally, this analysis is performed heuristically.

The user interface module 60 may also provide various other services to the user via a web interface. These include inputting basic profile information, such as type of house, name of energy company, etc., viewing and interpreting energy consumption data, and recording instructions to be carried out in response to particular power consumption levels or patterns.

Referring to Figures 12A and 12B, examples of energy usage information provided by the user interface module 60 in the form of screenshots are shown. The screenshot in Figure 12A shows energy usage by different categories of appliance 4 (Figure 1) in a period of seven days. The user may also choose to view total energy usage, energy usage by individual appliances 4 or categories of appliances 4 and/or energy usage in different time periods. Information may also be presented in other graphical or tabular forms. Other measures of energy usage such as financial cost or environmental (C02) cost may also be used. The tariff period (e.g., peak or off-peak) during which energy has been consumed may also be shown. The user can also choose to have information sent periodically to an email address or to an energy company. Furthermore, energy usage data can be compared with corresponding data for different time periods, for different homes or buildings or for alternative, e.g., more efficient, appliances 4. For example, the screenshot in Figure 12B shows a comparison of energy usage in a particular month with corresponding data for the previous year. The user can also view or choose to receive additional information such as, for example, methods of running appliances 4 more efficiently, financial benefits of replacing particular appliances 4 and/or opportunities to save money by switching to a different tariff or a different energy -20 -company. Data can also be provided to energy companies for planning purposes, e.g., allowing energy companies to vary tariffs so as to encourage off-peak energy consumption.

The user interface module 60 also enables the user to record instructions specifying actions to be carried out in response to particular conditions. Examples of these actions include switching on or off a socket in response to particular levels of energy usage, at particular times, e.g., when off-peak tariffs apply, or in response to particular patterns of energy usage by other appliances 4 (Figure 1), e.g., so that peripheral devices will switch on or off when a main device is switched on or off.

Sockets may also be switched on or off in response to dynamic demand regimes applied by an energy company, e.g., temporarily turning off a fridge or a battery charger at times of peak demand. Other examples include alerting the user by email or SMS, for example, about high, low or abnormal energy usage. The monitoring module 61 compares new energy usage data in the database 58, and other parameters, such as the time, with the conditions recorded in the instructions and carries out the corresponding action whenever the conditions are satisfied. For example, the monitoring module 61 may generate a message instructing a particular socket sensor 6 to switch off. This message will be passed to the web server module 56, which will send the message to the gateway 7 (Figure 1) as described earlier.

Finally, the device software updating module 62 monitors the software versions of meter sensors 5, socket sensors 6 and gateways 7 (Figure 1) present in the system 1, for example by reading software version identifiers included in the messages from the devices. When newer versions of the software are available, the device software updating module 62 may cause the web server module 56 to send the new software to the device in a series of messages.

It will be appreciated that many other modifications may be made to the embodiments hereinbefore described.

-21 -For example, there may be no meter sensor 5 included in the system I or there may be no socket sensors 6 included in the system 1. There may also be more than one meter sensor 5 included in the system 1. There may also be more than one appliance 4 connected via one or more socket sensors 6.

Furthermore, the network and devices via which the gateway 7 communicates with the server 9 may differ. For example, the network may include an Ethernet local area network, a wireless local area network and/or a mobile telecommunications network. Additional network devices may also be present. There may be no router 9 included in the system I and/or the gateway 7 and server 9 may be connected to the same network. The computer 12 may not be included or it may communicate with the server 9 via a different network.

The sensors 5, 6 need not send information to the server, but may store the information for retrieval at a later time, e.g., by the user connecting a memory stick or other storage device to the sensor 5, 6. Thus, the sensors 5, 6 need not include a sending means, e.g., need not include a network interface.

An appliance 4 may also be replaced by a device which is a generator of electricity, such as, for example, a solar panel or wind turbine. In this case, one or more of the sensors 5, 6 may be replaced by special sensors which are capable of monitoring power generation.

A display device may also be provided which receives messages from the server 9 via the router 7 and the wiring 2 and/or the wireless link 8, the messages including pre-selected information and alerts, and which displays this information on an LCD or other type of screen.

Monitoring of polyphase electrical power can also be performed by using one or more sensors 5, 6 arranged to measure the alternating current in a plurality of live wires.

Other types of devices, such as gas and water meters, and fire and intruder alarms, may also send information to and be controlled by the server 9.

Claims

-23 -Claims 1. A device comprising: means for measuring amplitude and/or change in phase of an alternating current in a section of wiring; means for generating a message in response to a change in the amplitude and/or a change in the phase of the alternating current, the message including information about the amplitude and/or the change in phase of the alternating current; and means for sending the message to a server.
2. A device according to claim 1, wherein the generating means is configured to include in the message information about the time when the change in amplitude and/or the change in phase of the alternating current occurred.
3. A device according to claim I or 2, wherein the generating means is configured to include in the message information identifying the device.
4. A device according to any preceding claim, wherein the generating means is configured to generate the message in response to a change of at least a predetermined level in amplitude and/or a change of at least a predetermined level in phase of the alternating current.
5. A device according to any preceding claim, wherein the sending means is configured to send the message via the wiring to a gateway.
6. A device according to claim 5, wherein the sending means is configured to send the message according to a power line communication protocol.
7. A device according to any preceding claim, wherein the sending means is configured to send the message via a wireless communication link to a gateway. -24-
8. A device according to any preceding claim, wherein the measuring means comprises a phase lock loop configured to generate an output signal in response to a change in phase of an alternating current input signal.
9. A device according to claim 8, wherein the phase lock loop comprises: means for generating an error signal which is dependent on the difference between an input signal and a feedback signal; means for integrating the error signal; and means for generating the feedback signal with a frequency which is dependent on the integrated error signal; wherein the phase lock loop is configured so that the feedback signal varies until it has the same phase and frequency as the input signal; and wherein the output signal is the integrated error signal.
10. A device according to claim 9, further comprising means for converting the output signal from an analogue to a digital signal.
11. A device according to any preceding claim, further comprising: switching means; and means for controlling operation of the switching means in response to receiving a message from the server including an instruction about operation of the switching means.
12. A device according to claim 11, wherein the generating means is configured to include in the message to the server information about status of the switching means.
13. A device comprising: a sensor configured to measure amplitude and/or change in phase of an alternating current in a section of wiring; a controller configured to generate a message in response to a change in the amplitude and/or a change in the phase of the alternating current, the message including information about the amplitude and/or the change in phase of the -25 -alternating current; and a network interface configured to send the message to a server.
14. A device according to claim 13, wherein the sensor comprises a phase lock loop configured to generate an output signal in response to a change in phase of an alternating current input signal.
15. A server configured to: receive a message from a device, the message generated in response to a change in amplitude and/or a change in phase of alternating current in a section of wiring and the message including information about the amplitude and/or the change in phase of the alternating current; and determine, from the information about the amplitude and/or the change in phase of the alternating current, the energy usage of one or more electrical devices powered via the section of wiring.
16. A server according to claim 15, wherein the message includes information about the time when the change in amplitude and/or the change in phase of the alternating current occurred and wherein the server is configured to determine the energy usage of the one or more electrical devices from the information about the time when the change occurred.
17. A server according to claim 15 or 16, configured to calculate the phase difference between voltage and current in the section of wiring by comparing the information about the change in phase of the alternating current with information about the change in phase of the alternating current at one or more earlier times.
18. A server according to any one of claims 15 to 17, configured to store an energy usage profile of one or more of the electrical devices, the energy usage profile including information about the amplitude and/or the phase of the alternating current at one or more times.

-26 -
19. A server according to any one of claims 15 to 18, configured to assign the change in amplitude and/or the change in phase of the alternating current to one or more of the electrical devices by determining whether the change in amplitude and/or the change in phase of the alternating current at one or more times matches any of a plurality of energy usage profiles of electrical devices.
20. A server according to claim 19, configured to read one or more of the plurality of energy usage profiles of electrical devices from a database.
21. A server according to any one of claims 15 to 20, configured to determine whether energy usage by one or more of the electrical devices matches any of a predefined plurality of energy usage conditions and, in response to matching the condition, send a message to a device comprising switching means, the message including an instruction about operation of the switching means.
22. A server according to any one of claims 15 to 21, configured to determine whether energy usage by one or more of the electrical devices matches any of a predefined plurality of energy usage conditions and, in response to matching the condition, send a message to a user.
23. A system comprising: one or more devices according to any one of claims I to 14; and a gateway; wherein the gateway is configured to receive the messages from the one or more devices and to send the messages from the one or more devices to the server.
24. A system according to claim 23, further comprising: a server according to any one of claims 15 to 22; wherein the gateway is configured to receive the messages from the server and to send the messages from the server to the one or more devices.

-27 -
25. A system according to claim 23 or 24, wherein the gateway is configured to store the messages from the one or more devices and/or the messages from the server for sending at a later time.
26. A method comprising; measuring amplitude and/or change in phase of an alternating current in a section of wiring; generating a message in response to a change in the amplitude and/or a change in the phase of the alternating current, the message including information about the amplitude and/or the change in phase of the alternating current; and sending the message to a server.
27. A method according to claim 26, wherein the message further includes information about the time when the change in the amplitude and/or the change in phase of the alternating current occurred.
28. A method according to claims 26 or 27, comprising sending the message in response to a change of at least a predetermined level in the amplitude and/or a change of at least a predetermined level in the phase of the alternating current.
29. A method according to any one of claims 26 to 28, comprising measuring the change in phase of the alternating current by phase locking.
30. A method according to any one of claims 26 to 29, further comprising controlling operation of switching means in response to receiving a message from the server including an instruction about operation of the switching means.
31. A method comprising: receiving a message from a device, the message generated in response to a change in amplitude and/or a change in phase of alternating current in a section of wiring and the message including information about the amplitude and/or the change in phase of the alternating current; and determining, from the information about the amplitude and/or the change in -28 -phase of the alternating current, the energy usage of one or more electrical devices powered via the section of wiring.
32. A method according to claim 31, comprising storing an energy usage profile of one or more of the electrical devices, the energy usage profile including information about the amplitude and/or the phase of the alternating current at one or more times.
33. A method according to claim 31 or 32, comprising assigning the change in amplitude and/or the change in phase of the alternating current to one or more of the electrical devices by determining whether the change in amplitude and/or the change in phase of the alternating current at one or more times matches any of a plurality of energy usage profiles of electrical devices.
34. A method according to any one of claims 31 to 33, comprising determining whether energy usage by one or more of the electrical devices matches any of a predefined plurality of energy usage conditions and, in response to matching the condition, sending a message to a device comprising switching means, the message including an instruction about operation of the switching means.
35. A method according to any one of claims 31 to 34, comprising determining whether energy usage by one or more of the electrical devices matches any of a predefined plurality of energy usage conditions and, in response to matching the condition, sending a message to a user.
36. A computer program comprising instructions which when executed by a data processing apparatus perform a method according to any one of claims 26 to 35.
37. A computer-readable medium storing a computer program according to claim 36.