ZA200903974B - Smart electricity meter incorporating ripple control and electricity quota functions while providing automatic meter reading - Google Patents

Description

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SMART ELECTRICITY METER INCORPORATING RIPPLE CONTROL

AND ELECTRICITY QUOTA FUNCTIONS WHILE PROVIDING

AUTOMATIC METER READING

BACKGROUND OF THE INVENTION

This invention relates to a smart electricity meter, which can be remotely read, and which also provides the ability to remotely disconnect certain. ‘ circuits, such as geysers, while allowing both credit and pre-paid metering x to be incorporated in the same meter.

A need exists for smart electricity meters with multifunction capabilities, \ such as remote reading, the ability to remotely control certain circuits, such as geysers (i.e. ripple control), and the ability to introduce an electricity quota system, even if an electricity consumer operates on a pre-paid basis.

The current meters, including smart meters and meters providing automatic meter reading capabilities, do not have all of these functions, meaning that a separate ripple controller must then be installed, or meaning that quota : systems can not be implemented on pre-paid systems.

It is thus an aim of the present invention to provide multiple functions in the same smart electricity meter, being remote reading, remote ripple control of circuits such as geysers, an electrical supply quota system, pre-paid electricity supply, and normal on-account electricity supply. A further aim of the present invention is to provide improved user interaction via a convenient remote control and display, which will promote voluntary user controlled energy savings.

SUMMARY OF THE INVENTION

According to the invention there is provided an electronic electricity meter comprising: a microprocessor with an associated program memory, non volatile storage memory for storing data, including data relating to the amount of electricity consumed, a user display means connected to the microprocessor, a means to read the amount of electricity being consumed by at least one circuit monitored by the meter, the at least one circuit comprising a main load circuit; a wireless communications link to a central host computer via a data transmission network; and an integrated circuit switch to switch on and off the main load circuit remotely.

In an example embodiment, the meter has a unique identifying code, allowing the meter to be uniquely identified.

In an example embodiment, one or more additional circuit switches are provided to multiple load circuits, thereby combining ripple control capability into the meter.

In an example embodiment, a tamper sensing circuit is provided, which will detect when the unit is opened or moved, and which will then transmit an alarm message to a host for further action.

In an example embodiment, the meter communicates with a host system wirelessly, the host system extracting electricity consumption data remotely. The host is able to provide commands to the meter to remotely enable and disable one or more electricity supply circuits.

The host system may provide a quota system, where an amount of electricity is downloaded to the meter for a particular period, and, where the meter will disrupt the output mains supply circuits should this quota be exceeded.

The host system additionally enables a pre-paid electricity supply system, where an amount of electricity is downloaded to the meter as a credit, or as additional credit, in which case it will be accumulated to any existing credit, and, where the meter will disrupt the output mains supply circuits should the total credit be exceeded.

In an example embodiment, the meter communicates with a remote user device, the remote user device comprising a display to show the user's quota, if available, and the electrical energy consumption, without the user having to go to the actual meter.

In an example embodiment, the meter comprises a low frequency power line communications modem with a data rate below 50 kilobits per second, to allow controlling data to be transmitted along with the mains power line to a power line controlled switch on the same electricity supply circuit measured by the meter, therefore allowing remote loads to be switched on and off by the meter.

Alternatively, or in addition, the meter comprises a short range wireless modem operating in a license free band, including 2.4ghz, 433 Mhz, 860- 869Mhz bands, with a data rate below 100 kilobits per second, to allow controlling data to be transmitted along with the mains power line to a power line controlled switch on the same electricity supply circuit measured by the meter, therefore allowing remote loads to be switched on and off by the meter.

In a further embodiment, the meter may be monitored and controlled from a cellular phone, with the meter reading being able to be picked up from the meter, and circuits being enabled and disabled remotely via user input on the cellular phone.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows a basic circuit diagram of a smart electricity reader’ according to an example embodiment of the present invention, the circuit comprising a main processor, a display, a GSM communications module, and an integrated Watt hour measurement controller; :

Figure 2 shows a basic circuit diagram of a mains circuitry, a current transformer, circuit switching relays, and a step down mains transformer, associated with the reader shown in Figure 1, and

Figure 3 shows a basic circuit diagram of a remote console that can be used by user who is not in close proximity to the meter. :

DESCRIPTION OF PREFERRED EMBODIMENTS

The electrical energy being consumed is fundamentally metered via an electronic circuit, which determines the mains voltage, the current of the load, and then accumulating this over time to derive energy consumed on a kilowatt hour basis.

Referring first to Figures 1 and 2, a microchip PIC18F6628 processor is used (U3) to control the operation of the smart meter. This processor has an internal 96 kbytes flash memory for storing an operating program.

Additionally, the processor contains a 3936 byte static random access memory (RAM) used to store constants, stacks, and other dynamically changeable data. Semi-permanent paramaters, such as GSM number strings, SIM PIN and calibration data is stored in the internal serial electrically changeable memory (EEPROM) of 1024 bytes. This processor has a large number of general purpose input/output pins (GPIO pins), allowing it to drive the circuit switching relays (RL1 to RL4 in Figure 2) via. the relay coil buffers.

The processor (U3) also contains an internal UART used to interface to the

GSM GPRS modem (M1) via the serial transmit data (TXD) and receive data (RXD) signals. The processor (U3) operates with a 8 MHz crystal (X1) and a 5 volt DC power supply. The processor's I°C serial peripheral bus is used to drive the user display (LCD1). The processor (U3) controls the circuit switching relays via 4 output ports, being PAO to PA4. When these ports are at logic level 1, the corresponding relay is activated via one of the driver transistors (Q1 to 4) shown in Figure 2, thereby activating the relevant relay.

The user display (LCD1) is a 16 character by 2 line liquid crystal display with a serial I°C interface, such as the LCD162-12 from Digital Orbital. The software transmits a display address to the LCD module, this indicates the position of displayable characters transmitted to the display (LCD1), and will allow a character to be displayed at any of the top and bottom lines of 8 characters per line. The LCD incorporates a character generator, able to display fundamentally the ASCII character set in accordance with the standard 7 bit data being presented to the character generator. The character data is then transmitted to the LCD, with the character corresponding to the data then being displayed at the specific address.

The data being displayed will be the accumulated consumption in kilowatt hours, the current electricity energy being consumed, and the status of the remote activated circuits, being on and off for the main circuit, and circuits 1 to 3 (shown in Figure 2). Additionally, a display showing a downloaded quota will also be displayed, should this be enabled for the particular

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Turning back to Figure 1, a CS5460 single phase watt hour meter controller (U2) from Cirrus Logic is used to determine energy consumption Watt hours. This controller (U2) has 2 main high resolution analog to digital converters, these being used to determine the RMS value of the mains voltage, as well as the instantaneous current consumption presented by the particular load. By using the instantaneous voltage and current, the

CS5460 calculates the RMS voltage, the RMS current, and the instantaneous power. Power is derived by multiplying RMS current and voltage at a rate of 4000 calculations per second.

The CS5460 is a CMOS monolithic power measurement integrated circuit with an integrated energy computation engine. The CS5460 performs measurements of instantaneous current, instantaneous voltage, instantaneous power, energy, RMS current, and RMS voltage. The se measurements are output as 24-bit signed values. Instantaneous calculations are performed at a 4000 Hz rate whereas current RMS, voltage

RMS, and energy in Watt seconds are performed at a 1 Hz rate.

The CS5460 contains both a serial SDI compliant interface port, as well as an energy to pulse rate conversion interface pins. These are not used in this embodiment, only the serial SDI interface is used to set up the S5460 device, and to read the energy once every second. The CS5460 contains a number of internal configuration registers, which are largely set up at start- up. These set up the clock dividers, enabling the digital filters. The gain adjustments are made in order to compensate for gain in the current transformer, mains RMS input voltage changes, etc. The resistor based voltage divider of R11 and RB, as well as the similar network of R12 and R7 reduces the AC input voltage to the VIN+ and VIN- input pins to safe levels below 250 mV RMS. Resistors R13 and RO reduce the already low I_In current sensing voltage by a factor of 16.6. This will reduce a current transformer maximum output voltage of 3.3 Volts RMS for a mains current

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H2000/05,,, loading of 30 Amperes to less than 250 mV RMS at the I_IN+ pin of the | :

CS5460 device.

A current transformer (CT1), as shown in Figure 2, is used to derive an isolated, low voltage signal which is fully proportional to the current being consumed by the meter. The current transformer, type CSE187-L, has a : primary winding in series with the live mains conductor to the meter. The secondary winding provides an isolated RMS low voltage output proportional to the RMS current being consumed by the load attached to the meter at 110 mVolts per Ampere sensed on the mains side, and can sense up to 30 Ampere on the mains side. This provides the instantaneous load voltage. The low voltage signal is converted to a digital value by a high resolution analog to digital converter, integrated in the

CS5460. The output of this analog to digital converter is digitally filtered to provide a noise free digital representation of the instantaneous current.

This single ended voltage, being I_RMS, is connected to IN+ of the

CS5460, which is the current input. The negative input of this differential signal is grounded. The voltage inputs (VIN+ and VIN-) pins come from the secondary of a 12 volt, centre tapped transformer (T2). Power is fundamentally derived in the CS5460 by multiplying the sensed RMS voltage and current. After suitable calibration, this provides the instantaneous power representation, in Watts. This becomes energy when accumulated over time, such as over an hour to represent watt hours, or kilowatt hours for higher consumption.

The secondary output voltage from the same transformer is further connected to the anode of 2 diodes, these being used to generate the DC supply voltage for the meter. A 7805 linear voltage regulator (REG1) provides the 5V DC regulated supply for the meter circuitry.

Referring back to Figure 1, communications to a host computer is via the use of a GSM modem module, M1, being a Telit GT864 quad band GSM modem. The trigger signal is an output from the PIC processor (U3) to the

GSM modem to switch the modem on and off. The GSM modem will remain switched on for most of the time to allow it to receive control messages. Alternative communications means to the host system may be accomplished by using the industry standard WiMax wireless communications means, using, for example, standard infrastructure from

Cisco. Many local governments and municipalities are considering implementing WiMax to provide connectivity infra-structure to residents in its region. The meter will then be able to utilize this infra-structure. An alternative will be to use medium to long range mesh based wireless communications, which may be dedicated to meter reading. In this case, a

TinyOnelite RF 433 MHz module from One RF Technology, embedded with their Mesh Protocol stack may be used. Each meter will be fitted with this module in place of the GSM modem (M1). The typical transmission distance will be up to 5 km line of sight, however, the mesh protocol will substantially extend this range by allowing messages to hop through modems in order to reach the host system, even though it may be situated more than 10 km away from the meter.

A software routine will firstly set up the Watt hour controller with values written to its gain registers, these values specific to the particular meter to derive an accurate Watt hour reading. This is required due to tolerances in components, including the current transformer and the voltage transformer.

A number of different calibration techniques exist and may be used. A simple calibration technique used is to first calibrate accurately the instantaneous power measured in Watts, by using 4 different known and accurate high wattage resistive loads, including using resistor banks, and changing the gain register values to reflect the correct load for the particular

RMS mains voltage being applied. For example, resistors providing loads of 25 Watts, 250 Watts, 2.5 kW, and 5 kW at 220 V RMS will provide a range of loads for calibration purposes. Variations from 220 V AC RMS must be factored into the reading, using the simple formula of W=l x V, and

W=MainsVoltage?/ load resistance. For example, using a resistive load of 22 ohms, the load will be 2200 Watts at 220 Volts RMS. At 210 V RMS the load will be 2004 Watts. A laboratory quality accurate AC volt meter must be used to measure the AC RMS voltage during the calibration process, this will facilitate accurate calibration.

In operation the software will read the energy consumed every second from the CS5460, this will then be accumulated to provide the amount of Watts used per minute, per hour, and for the complete duration of the metering period. The processor contains an internal timer, which will interrupt the processor every second, this in turn will allow software routines to accumulate registers every minute and every hour. The kilowatt hours consumed will be stored in EEPROM as the kWHour_register. This register can be read remotely via the GSM modem on command. This register can also be cleared remotely. The main registers contained in the

EEPROM memory are the kWatt_hours_consumed register, the Quota register, if used, and the kWatt_hour_credit register, if used.

The host will read a meter as follows: The particular meter will be called via a GSM data call. Upon answering, the meter will send the following data to the host. unique meter identification number, typically being a 10 digit number, the kWatt_hours_consumed register, and the kWatt_hour_credit register, if used.

Once the host has acquired this meter reading data, it will send the following to the meter: Quota if used, new kWatt_hour_credit (if used), and bytes, being ffh for on, and 55h for off, for each of the 4 circuits, thus allowing these circuits to be remotely switched on and off. If in any field a zero value is inserted, it will be regarded as a no-operation value, this function will therefore be disabled. In this way the meter reading is done remotely, an interrogation of the credit remaining is completed, and the remote control of quota, circuit switching and credit updating is accomplished.

If the meter is used in a pre-paid credit mode, it will continuously decrement the available credit in accordance to the actual measured electricity consumption. At zero, the meter will switch the main circuit relay (RL1 off).

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This embodiment of the meter does not provide for a local entry of credit, 4 such as a keypad being used to enter an encrypted electricity credit amount as per the current state of the art for pre-paid electricity meters. Therefore, credit can only be uploaded via the above GSM based data transaction.

Turning now to Figure 3, a remote console, which will allow the meter reading and status to be displayed to the user without having to be in close proximity to the meter is shown. This battery operated remote console contains a liquid crystal display (LCD), as well as a small keypad. It is linked to the meter via a short range 868 MHz wireless link, utilizing an

Aerocom ACA4486-5 wireless modem at both ends. The typical range is 100 meters. A PIC processor (I12C) is used to handle communications to and from the meter, to display the meter status as well as user input, and to. control a simple 8 key user keypad shown on the bottom left of the drawing.

The keypad allows the user to switch any one of the circuits on and off remotely, especially circuits powering non-used appliances, such as geysers during certain times of the day, thereby reducing unnecessary electricity consumption. Additionally, it will allow the user to monitor their electricity consumption, available credit if a pre-paid implementation is used, and, should a quota system be used, what the allowed quota is.

An additional implementation will use a wireless or mains power communications based system to link the meter to remote on/off actuators or switches, without additional wiring, thereby allowing these to be remotely controlled by the meter. In such an implementation, an Insteon Power Line

Communications gateway will be used to link the meter to mains, and to allow communications to other Insteon switches on the mains cabling monitored by the meter. An Insteon EZIO2X4 switch can be used for example to switch off appliances when not in use, thereby reducing current.

Alternatively, short range industry standard wireless networking can be used, with devices controlling relays to power remote appliances on and . off. A wireless standard which is finding acceptance in the energy management sector is 150802.15.4, with a mesh protocol stack implemented to achieve broad building coverage and range.

The meter comprises a battery that will allow full operation of the meter without mains power being available, other than actual mains metering.

The meter also provides for automatic reporting of power outages, where the meter will communicate to the host system a loss of mains power, while it is being powered by its internal battery supply.

The meter may further comprise a wireless link to additional metering services, such as a water meter, to allow remote water metering via the same smart meter and communications link.

Claims (13)

CL ‘- TTT 2 . : C CLAIMS £2000,

1. An electronic electricity meter comprising: a microprocessor with an associated program memory; non volatile storage memory for storing data, including data relating to the amount of electricity consumed; a user display means connected to the microprocessor, a means to read the amount of electricity being consumed by at least one circuit monitored by the meter, the at least one circuit comprising a main load circuit; CL a wireless communications link to a central host computer via a data transmission network; and an integrated circuit switch to switch on and off the main load circuit remotely.

2. The electronic electricity meter of claim 1, wherein the meter has a unique identifying code, allowing the meter to be uniquely identified.

3. The electronic electricity meter of either claim 1 or claim 2, wherein one or more additional circuit switches are provided to multiple load circuits, thereby combining ripple control capability into the meter.

4. The electronic electricity meter of any one of the preceding claims, wherein a tamper sensing circuit is provided to detect when the meter is opened or moved, and if so, to transmit an alarm message to a host for further action.

5. The electronic electricity meter of any one of the preceding claims,

wherein the meter communicates with a host system wirelessly, the host system extracting electricity consumption data remotely.

6. The electronic electricity meter of claim 5, wherein the host system is able to provide commands to the meter to remotely enable and disable one or more electricity supply circuits.

7. The electronic electricity meter of either claim 5 or claim 6, wherein the host system provides a quota system, where an amount of electricity is downloaded to the meter for a particular period, with the meter disrupting the output mains supply circuits should this quota be exceeded.

8. The electronic electricity meter of any one claims 5 to 7, wherein the host system enables a pre-paid electricity supply system, where an amount of electricity is downloaded to the meter as a credit, or as additional credit, in which case it will be accumulated to any existing credit, and, where the meter will disrupt the output mains supply circuits should the total credit be exceeded.

9. The electronic electricity meter of any one of the preceding claims, wherein the meter communicates with a remote user device, the remote user device comprising a display to show the user's quota, if available, and the electrical energy consumption, without the user having to physically inspect the meter.

10. The electronic electricity meter of any one of the preceding claims, further comprising a low frequency power line communications modem with a data rate below 50 kilobits per second, to allow controlling data to be transmitted along with the mains power line to a power line controlled switch on the same electricity supply circuit measured by the meter, therefore allowing remote loads to be switched on and off by the meter.

1". The electronic electricity meter of any one of the preceding claims, further comprising a short range wireless modem operating in a license free band, including 2.4ghz, 433 Mhz, 860-869Mhz bands, with a data rate below 100 kilobits per second, to allow controlling data to be transmitted along with the mains power line to a power line controlled switch on the same electricity supply circuit measured by the meter, therefore allowing remote loads to be switched on and off by the meter. Co

12. The electronic electricity meter of any one of the preceding claims, . wherein the meter can be monitored and controlled from a cellular phone, with the meter reading being able to be picked up from the meter, and circuits being enabled and disabled remotely via user input on the cellular phone.

13. An electronic electricity meter substantially as herein described and illustrated. DATED THIS 8™ DAY OF JUNE 2009 BOWMAN GILFILLAN INC. (JOHN & KERNICK) FOR THE APPLICANT