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Load Profile and Communication Channel Characteristics of the Low Voltage Grid

This paper explores the communication channels between the substation and households on the low-voltage grid, analyzing their varying quality based on location, load profile, and time. The study focuses on a meter reading system in Ronneby, Sweden, using statistics to estimate channel quality and develop a channel model. The results are combined with convolutional codes, diversity, and modulation methods for efficient communication.

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Load Profile and Communication Channel Characteristics of the Low Voltage Grid

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  1. Load Profile and Communication Channel Characteristics of the Low Voltage Grid Lars Selander, Lund University, Sweden Tonny I. Mortensen, NESA A/S, Denmark Göran Lindell, Lund University, Sweden Lars Selander www.enersearch.se/goto/ises7pub.html

  2. Introduction (1) Communication on the low-voltage grid • The communication is going on between the substation and the households, not between households • The communication link between the sub station and household number i is defined a communication channel, Ci • The quality of each channel varies. Not only geographically but also with different loads and in time Sub station 10kV / 0.4kV C1 C3 C2 C4 Lars Selander www.enersearch.se/goto/ises7pub.html

  3. Noise Ni(t) Transfer function Sub station Household i Hi(f,t) Introduction (2) Project description • In this paper we have observed a typical application used on the low-voltage grid. A meter reading system in Ronneby, Sweden • With statistics from this system the quality of the channels has been estimated and been compared to loads, time and location in the grid • Further measurements and these results will give a channel model • Combined with convolutional codes, diversity and modulation methods (QAM, PSK). Non-coherent, coherent detection Lars Selander www.enersearch.se/goto/ises7pub.html

  4. Outline • Introduction • The IDAM system • A measure of the channel quality • The time-variant behavior of the channel quality • Channel quality at specific locations in the grid • The effect of the load profile on the channel quality • The influence of an impairment source on the channel quality • Summary • URL: http://www.enersearch.se/goto/ises7pub.html Lars Selander www.enersearch.se/goto/ises7pub.html

  5. Customer 0,4kV 10kV Meter MFN CCN The IDAM System (1) • IDAM, a meter reading system • Concentrator & Communication Node (CCN), Multi Function Node (MFN) • Each hour all the meter values are read • The communication is made up of transactions, a control-flow consisting of a request (CCN) and a reply (MFN) • Failed transactions are re-transmitted to ensure no lack of data Fig 1. A schematic of the IDAM System. Lars Selander www.enersearch.se/goto/ises7pub.html

  6. The IDAM System (2) The implementation in Ronneby, Sweden Sub station 10kV / 0.4kV Cable-box Fig 2. A map of the low-voltage grid in Patorp. Lars Selander www.enersearch.se/goto/ises7pub.html

  7. A Measure of the Channel Quality • For each hour IDAM counts • ei , the number of failed transactions on channel i • Ni , the total number of transactions on channel i • The channel impairment indicator is defined as: • Piis a measure of the quality of the communication channel between the sub station and household i • A small Pi corresponds to a good channel and a large Pi to a bad channel • Pi can also be viewed as the estimated probability that a transaction fails Lars Selander www.enersearch.se/goto/ises7pub.html

  8. The time-variant behavior of the channel quality The average channel quality for the whole grid ”Bad” Channel Decreasing Channel Quality ”Good” Channel Fig 3. The average, P, of all estimated channel impairment indicators, Pi, for each hour during a day. Lars Selander www.enersearch.se/goto/ises7pub.html

  9. Channel Quality at Specific Locations in the Grid The average channel quality associated with each cable-box Sunday Monday Decreasing Channel Quality Increasing distance to the sub station Fig 6. The average of the channel impairment indicators associated with each cable-box in the grid (24-hour average) for a week in February. Lars Selander www.enersearch.se/goto/ises7pub.html

  10. Load profile and Channel Quality Load profile (the energy-usage in the area) and the average channel quality for the whole grid Fig 7. The average, P, of all channel impairment indicators, Pi, and the load profile. The load profile is shown with bars and the parameter P as a line. Lars Selander www.enersearch.se/goto/ises7pub.html

  11. The Influence of an Impairment Source (1) Description of the load • A moveable load • Designed to be used to test the effect of loads on the grid • Contains a set of industrial machines: • Voltage source inverter • Induction motor • Synchronous generator • Heaters • Welding unit Lars Selander www.enersearch.se/goto/ises7pub.html

  12. The Influence of an Impairment Source (2) The average channel quality when the load was connected to the sub station Load location Load active. At this time, half the area needed a transmission Decreasing Channel Quality Fig 8. The average, P, of all estimated channel impairment indicators, Pi. The load was on 10-12 am and 13-15 pm. Lars Selander www.enersearch.se/goto/ises7pub.html

  13. The Influence of an Impairment Source (3) The average channel quality when the load was connected to cable-box 0447 Load active Load location Decreasing Channel Quality Fig 9. The average, P, of all estimated channel impairment indicators , Pi. The load was on 8-9 am, 10-11 am, 12-13 pm and 14-24 pm. Lars Selander www.enersearch.se/goto/ises7pub.html

  14. The Influence of an Impairment Source (4) The average channel quality associated with some cable-boxes on the low-voltage line where the load was connected Decreasing Channel Quality Fig 10. The average, Pcb, of the channel impairment indicators associated with cable-box 447 and 446. The black bars correspond to March the 27th and the white bars to March the 13th. Lars Selander www.enersearch.se/goto/ises7pub.html

  15. Summary • The quality varies in time and the behavior is about the same each day • The worst channel is found during the evening • An increase of the energy used tend to decrease the channel quality • The load tested caused a decrease of the channel quality. The actual interference depended on the distance between the load and the channel • We want to achieve higher bit rates and more reliable communication Lars Selander www.enersearch.se/goto/ises7pub.html

  16. Overall Channel Quality(2) The average channel quality in February and May Max Median Min Fig 4. The collected data of the parameter P in February (a) and May (b). Shown is, for each hour (0-23) during respective month, the median (crosses) and the minimum and the maximum values. The three largest and the three smallest values are plotted with dots in the graphs. Lars Selander www.enersearch.se/goto/ises7pub.html

  17. Overall Channel Quality(3) The number of houses in need of a re-transmission each hour Corresponds to 30% of the total area Decreasing Channel Quality Fig 5. The number of houses experiencing a re-transmission each hour, i.e. ei is not equal to zero. Lars Selander www.enersearch.se/goto/ises7pub.html

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