Utility metering

Abstract

An apparatus has an input section arranged to receive values representative of the total instantaneous supply of electrical current as a function of time from an alternating voltage supply. Current waveforms comprising sets of values representative of the cyclic waveform of the electric current supply are obtained. A delta waveform generator calculates the difference between a current waveform and an earlier current waveform. An edge detector is arranged to detect an edge or edges in the delta waveform. An analysis section is arranged to identify at least one appliance load based at least on information on the edge or edges detected by the edge detector, and to determine the electrical energy consumed by said appliance load. Another apparatus has an input section arranged to receive values representative of the current supplied to an installation, such as a house. A store contains appliance data characteristic of the use of electricity by each of a plurality of appliances. A processor is arranged to analyse the received values to detect when an appliance is switched on and determine the fractional change in resistance of a heating appliance from the when it is switched on until it reaches its operating temperature. This information is used to identify what the particular appliance is, and to determine the electrical energy consumption by that appliance. A utility meter for metering the use of at least one utility supplied to a plurality of appliances is also disclosed. An input section is arranged to receive values representative of the use of a first utility. A store contains appliance data characteristic of the use of utilities by each of a plurality of appliances. A processor is arranged to analyse the received values and to determine information on the use of a second utility by each appliance, based on the received values and appliance data.

1 . A variable power load detector apparatus, for use in a non-intrusive electrical load meter for metering the use of electricity supplied to a plurality of loads, the apparatus comprising:
 an input section arranged to receive values representative of the total instantaneous supply of electrical current as a function of time from an alternating voltage supply;   a monitor section arranged to determine current waveforms comprising sets of values representative of the cyclic waveform of the electric current supply;   a delta waveform generator arranged to calculate the difference between a current waveform and an earlier current waveform, by subtracting the respective sets of values determined by the monitor section, to obtain a delta waveform;   an edge detector arranged to detect an edge or edges in the delta waveform; and   an analysis section arranged to identify at least one load based at least on information on the edge or edges detected by the edge detector.   
     
     
         2 . Apparatus according to  claim 1 , further comprising an event detector arranged to detect an event representing a change in the total electrical energy being supplied per cycle; and wherein the delta waveform generator is arranged to calculate the difference between the current waveforms before and after the detected event. 
     
     
         3 . Apparatus according to  claim 1  or  2 , wherein the edge detector is further arranged to determine information on the gradient of at least one of the edges. 
     
     
         4 . Apparatus according to  claim 1 ,  2  or  3 , wherein the edge detector is further arranged to determine information on the position of any edges in the delta waveform. 
     
     
         5 . Apparatus according to  claim 4 , wherein the analysis section is further arranged to determine the nominal full power of the at least one load based on the position of at least one detected edge. 
     
     
         6 . Apparatus according to any one of the preceding claims, wherein the edge detector is further arranged to determine information on the number of edges in the delta waveform. 
     
     
         7 . Apparatus according to any one of the preceding claims, wherein the analysis section is further arranged to identify at least one load based on the presently known powers of loads known to the apparatus. 
     
     
         8 . Apparatus according to any one of the preceding claims, wherein the monitor section is arranged to determine current waveforms for the whole or half of a cycle of the alternating electricity supply. 
     
     
         9 . Apparatus according to any one of the preceding claims, wherein at least one current waveform determined by the monitor section is a weighted mean over a plurality of cycles of the alternating electricity supply. 
     
     
         10 . Apparatus according to any one of the preceding claims, wherein at least one load has its power varied by a controlled switch; preferably said controlled switch comprises a TRIAC, an SCR or a thyristor. 
     
     
         11 . Apparatus according to any one of the preceding claims, wherein the analysis section is arranged to determine the electrical energy consumed individually by each load. 
     
     
         12 . Apparatus according to claim any one of the preceding claims, wherein the edge detector is arranged to:
 correlate the delta waveform with at least a subset of basis waveforms, each basis waveform having a known edge or edges;   identify the basis waveform corresponding to the highest correlation coefficient; and   detect an edge or edges in the delta waveform based on the known edge or edges in the identified basis waveform.   
     
     
         13 . Method for detecting a variable power load, for use in non-intrusive electrical load metering, for metering the use of electricity supplied to a plurality of loads, the method comprising:
 receiving values representative of the total instantaneous supply of electrical current as a function of time from an alternating voltage supply;   determining current waveforms comprising sets of values representative of the cyclic waveform of the electric current supply;   generating a delta waveform by calculating the difference between a current waveform and an earlier current waveform, by subtracting the respective sets of waveform values;   detecting an edge or edges in the delta waveform; and   identifying at least one load based at least on information on the detected edge or edges.   
     
     
         14 . Method according to  claim 13 , further comprising detecting an event representing a change in the total electrical energy being supplied per cycle; and
 wherein the delta waveform is calculated as the difference between the current waveforms before and after the detected event.   
     
     
         15 . Method according to  claim 13  or  14 , further comprising determining information on the gradient of at least one of the edges. 
     
     
         16 . Method according to  claim 13 ,  14  or  15 , further comprising determining information on the position of any edges in the delta waveform. 
     
     
         17 . Method according to  claim 16 , further comprising determining the nominal full power of the at least one load based on the position of at least one detected edge. 
     
     
         18 . Method according to any one of  claims 13  to  17 , further comprising determining information on the number of edges in the delta waveform. 
     
     
         19 . Method according to any one of  claims 13  to  18 , further comprising identifying at least one load based on the presently known powers of loads being supplied with electricity. 
     
     
         20 . Method according to any one of  claims 13  to  19 , wherein the current waveforms are determined for the whole or half of a cycle of the alternating electricity supply. 
     
     
         21 . Method according to any one of  claims 13  to  20 , wherein at least one current waveform is an average over a plurality of cycles of the alternating electricity supply. 
     
     
         22 . Method according to any one of  claims 13  to  21 , wherein at least one load has its power varied by a controlled switch; preferably said controlled switch comprises a TRIAC, an SCR or a thyristor. 
     
     
         23 . Method according to any one of  claims 13  to  22 , further comprising determining the electrical energy individually consumed by each load. 
     
     
         24 . Method according to any one of  claims 13  to  23 , wherein the step of detecting an edge or edges in the delta waveform comprises:
 providing a set of basis waveforms, each basis waveform having a known edge or edges; 
 correlating the delta waveform with at least a subset of the basis waveforms; 
 identifying the basis waveform corresponding to the highest correlation coefficient; and 
 detecting an edge or edges in the delta waveform based on the known edge or edges in the identified basis waveform. 
 
     
     
         25 . Apparatus for metering the use of electricity supplied to a plurality of appliances, the apparatus comprising:
 an input section arranged to receive values representative of the total supply of electrical power as a function of time;   a transient detector arranged to detect the time at which an appliance is switched on from a change in the received values due to an increase in the electric power being supplied at that time;   an analysis section arranged to analyse the received values and to determine:   (i) a first value related to the resistance of said appliance at the time of being switched on detected by said transient detector; and   (ii) a second value related to the resistance of said appliance when operating in a steady state; and   a processing section arranged to identify said appliance based on at least said first and second values, and to determine the electrical energy consumed by said appliance.   
     
     
         26 . Apparatus according to  claim 25 , wherein the received values are measurements of current or measurements of current and voltage of the electricity supply. 
     
     
         27 . Apparatus according to  claim 25  or  26 , wherein each said value related to the resistance is one of: the current; the reciprocal of the current; the voltage divided by the current; the voltage multiplied by the current, and
 wherein said current values represent the current supplied to said appliance given by the total supply current minus the supply current before the switch on of said appliance detected by the transient detector. 
 
     
     
         28 . Apparatus according to  claim 25 ,  26  or  27 , wherein the processing section is arranged to calculate a classification value given by: the difference between the second value and the first value, divided by the first value. 
     
     
         29 . Apparatus according to any one of  claims 25  to  28  wherein the analysis section is further arranged to determine the time duration from when the appliance is switched on until the electrical power being used by the appliance has reached a steady state; and the identification of said appliance by said processing section is further based on said time duration. 
     
     
         30 . Apparatus according to  claim 29 , wherein the analysis section is arranged to determine a further classification value related to: the total electrical energy supplied to the appliance from the time of switch on until the time steady state is reached, minus the product of the steady state power and the time from switch on until steady state is reached; and the identification of said appliance by said processing section is further based on said further classification value. 
     
     
         31 . Apparatus for metering the use of electricity supplied to a plurality of appliances, the apparatus comprising:
 an input section arranged to receive values representative of the total supply of electrical power as a function of time;   a transient detector arranged to detect the time at which an appliance is switched on from a change in the received values due to an increase in the electric power being supplied at that time;   an analysis section arranged to analyse the received values and to determine:   (i) the time when the electrical power being used by the appliance has reached a steady state; and   (ii) a classification value related to: the total electrical energy supplied to the appliance from the time of switch on until the time steady state is reached, minus the product of the steady state power and the time from switch on until steady state is reached;   a processing section arranged to identify said appliance based on at least said classification value, and to determine the total electrical energy consumed by said appliance.   
     
     
         32 . Apparatus according to any one of  claims 25  to  31 , wherein electricity is supplied to a plurality of appliances and said processor is arranged to determine information on the electricity usage by individual ones of said appliances. 
     
     
         33 . Method for metering the use of electricity supplied to a plurality of appliances, the method comprising:
 receiving values representative of the total supply of electrical power as a function of time;   detecting the time at which an appliance is switched on from a change in the received values due to an increase in the electric power being supplied at that time;   analysing the received values and determining:   (i) a first value related to the resistance of said appliance at the time of being switched on; and   (ii) a second value related to the resistance of said appliance when operating in a steady state; and   identifying said appliance based on at least said first and second values, and determining the electric energy consumed by said appliance.   
     
     
         34 . Method according to  claim 33 , wherein the received values are measurements of current or measurements of current and voltage of the electricity supply. 
     
     
         35 . Method according to  claim 33  or  34 , wherein each said value related to the resistance is one of: the current; the reciprocal of the current; the voltage divided by the current; the voltage multiplied by the current, and
 wherein said current values represent the current supplied to said appliance given by the total supply current minus the supply current before the switch on of said appliance. 
 
     
     
         36 . Method according to  claim 33 ,  34  or  35 , further comprising calculating a classification value given by: the difference between the second value and the first value, divided by the first value. 
     
     
         37 . Method according to any one of  claims 33  to  36 , further comprising determining the time duration from when the appliance is switched on until the electrical power being used by the appliance has reached a steady state; and wherein the identification of said appliance is further based on said time duration. 
     
     
         38 . Method according to  claim 37 , comprising determining a further classification value related to: the total electrical energy supplied to the appliance from the time of switch on until the time steady state is reached, minus the product of the steady state power and the time from switch on until steady state is reached; and wherein the identification of said appliance is further based on said further classification value. 
     
     
         39 . Method for metering the use of electricity supplied to a plurality of appliances, the method comprising:
 receiving values representative of the total supply of electrical power as a function of time;   detecting the time at which an appliance is switched on from a change in the received values due to an increase in the electric power being supplied at that time;   analysing the received values and determining:   (i) the time when the electrical power being used by the appliance has reached a steady state; and   (ii) a classification value related to: the total electrical energy supplied to the appliance from the time of switch on until the time steady state is reached, minus the product of the steady state power and the time from switch on until steady state is reached; and   identifying said appliance based on at least said classification value, and determining the total electrical energy consumed by said appliance.   
     
     
         40 . Method according to any one of  claims 33  to  39 , wherein electricity is supplied to a plurality of appliances and said method is arranged to determine information on the electricity usage by individual ones of said appliances. 
     
     
         41 . Apparatus for metering the use of a utility, the apparatus comprising:
 an input section arranged to receive values representative of use of a first utility; and   a processor arranged to analyse the received values and to determine information on the use of a second utility based on the received values; and   an output section for outputting said information.   
     
     
         42 . Apparatus according to  claim 41 , wherein said input section is further arranged to receive values representative of total use of the second utility. 
     
     
         43 . Apparatus according to  claim 42 , wherein said second utility is supplied to a plurality of appliances and said processor is further arranged to determine information on the usage of said second utility by individual ones of said appliances. 
     
     
         44 . Apparatus according to  claim 43 , wherein the processor is arranged to determine information on the use of the second utility by each specific appliance based on inference of the most probable appliance or combination of appliances to be operating based on the received values. 
     
     
         45 . Apparatus according to any one of  claims 41  to  44 , wherein the processor is arranged to determine information on the use of the second utility further using known characteristics of the or each appliance to which said second utility is supplied. 
     
     
         46 . Apparatus according to any one of  claims 41  to  45 , wherein said received values represent the supply of a utility as a function of time. 
     
     
         47 . Apparatus according to  claim 46 , wherein one of said utilities is electricity and the input values represent at least instantaneous current of the supply, optionally both instantaneous current and voltage of the supply. 
     
     
         48 . Apparatus according to any one of  claims 41  to  47 , wherein the first and second utilities respectively comprise one of the following pairs: water and electricity; electricity and oil; or gas and electricity. 
     
     
         49 . Method for metering the use of a utility, comprising:
 receiving values representative of use of a first utility; and   analysing the received values to determine information on the use of a second utility based on the received values; and   outputting said information.   
     
     
         50 . Method according to  claim 49 , wherein further comprising receiving values representative of total use of the second utility. 
     
     
         51 . Method according to  claim 50 , wherein said second utility is supplied to a plurality of appliances, and wherein said method further comprises determining information on the usage of said second utility by individual ones of said appliances. 
     
     
         52 . Method according to  claim 51 , wherein the analysing process comprises determining information on the use of the second utility by each specific appliance based on inference of the most probable appliance or combination of appliances to be operating based on the received values. 
     
     
         53 . Method according to any one of  claims 49  to  52 , wherein information on the use of the second utility is determined further using known characteristics of the or each appliance to which said second utility is supplied. 
     
     
         54 . Method according to any one of  claims 49  to  53 , wherein said received values represent the supply of a utility as a function of time. 
     
     
         55 . Method according to  claim 54 , wherein one of said utilities is electricity and the input values represent at least instantaneous current of the supply, optionally both instantaneous current and voltage of the supply. 
     
     
         56 . Method according to any one of  claims 49  to  55 , wherein the first and second utilities respectively comprise one of the following pairs: water and electricity; electricity and oil; or gas and electricity. 
     
     
         57 . A computer program comprising computer-executable code that when executed on a computer system, causes the computer system to perform a method according to any one of  claims 13  to  24 , or  3  to  40 , or  49  to  56 . 
     
     
         58 . A computer-readable medium storing a computer program according to  claim 57 . 
     
     
         59 . A computer program product comprising a signal comprising a computer program according to  claim 57 . 
     
     
         60 . An apparatus for metering the use of a utility supplied to a plurality of appliances, the apparatus comprising:
 an input section arranged to receive, from a sensor, values representative of the total utility being used as a function of time, and to receive time data on the actual time of each sensed value;   a store containing appliance data characteristic of the use of the utility by each of a plurality of appliances;   a processor arranged to analyse the received values and time data, based on the appliance data, and to determine information on the use of the utility by each appliance; and   an output section for outputting said information;   wherein the processor is arranged to determine information on the use of the utility by each appliance based on inference of the most probable appliance or combination of appliances to be operating at a particular time and the most probable magnitude of consumption of the utility by each respective appliance, based on the received values, time data and appliance data; and   wherein the inference uses an inference technique selected from Bayesian inference, neural networks and fuzzy logic.   
     
     
         61 . The apparatus of  claim 60 , in which the processor is arranged to use the inference to calculate a probability of the plurality of appliances being in a particular state. 
     
     
         62 . The apparatus of  claim 61 , in which the processor is arranged to:
 use the inference to calculate a plurality of probabilities, each probability being a probability that the plurality of appliances are in a respective state; and   determine that the plurality of appliances are in the state with the highest probability.