How to design the electric meter - 'qualified' The smart grid -

Balance of supply and demand

power companies face challenging tasks, i. e. , according to the fixed power supply electricity to meet the needs of highly variable. During the peak power demand is likely to be the usual several times, capital intensive, power plant, it is difficult to fully meet the demand for electricity. Provide incentive time-sharing electricity prices for consumers or for remote management of high-end equipment electricity time is a more effective way to controllable electric power supply and demand balance. To provide time-sharing electricity prices, power companies must clearly understand the user consumption power of time, that is to say, there must be connected to the power companies and users meter communication path.

why don't you use the wireless network?

apparently, wireless standards can be used for electric power meter communication, but there are some problems. It is suggested that using 2 based on ZigBee. 4 GHz technology, but in practice, in the 20 - 50 meters short range, they were unable to economic effective feedback the information to the power company. Add a mesh network can expand the range of Zigbee network, however, and in rural and suburban areas interference in larger structures, the distance between the meter is greater, for ISM2. 4 GHZ frequency wireless communication challenges. For example, a crowded multi-storey apartment building will have complex coverage and connectivity issues, installation and maintenance of the high cost of wireless network. The latest IEEE 802. 15. 4 g smart power company network ( 太阳) Standard aims to use a variety of frequencies to respond to these challenges, but has not yet prepared to large-scale deployment. Wireless network is the biggest defect need to use the scarce and precious spectrum, it can be very expensive and/or is not available at any time.

wire communication

the most obvious communication path is wire communication, why not when power is supplied from a signal?

for a long time, the power company has been using wire and power generation equipment to communicate and to provide voice communications between sub station, including adding a signal on the high tension line. These signals are usually using amplitude modulation or frequency shift keying, the average rate of 1 KB/s or less, low data transmission rate can realize long distance transmission of signals. This technique is used to cut cut out the integrity of the power distribution unit, check the power grid and for remote power and sub station provides basic voice communication. However, the number of meters to thousands, more than the power distribution unit this method cannot be effectively extended used in electric power company meter link.

in order to realize the communication with the meter, need a higher data rate and can be flexible semi-autonomous support of multi-user communication network technology. G3 - PLC controller narrow-band orthogonal frequency reuse ( OFDM) Wire communication standard specifically designed for this purpose, with the ability to overcome the special wire communication challenges. The standard reference to the multiple wireless technologies, such as OFDM communications, Reed ‐ Solomon forward error correction mechanism, such as Viterbi convolutional decoding time and frequency domain, and weaving technology and so on.

challenging wire itself, in many ways more noise than wireless channel. Wires are highly non-stationary noise, equipped with a Gaussian components ( Similar to the wireless) And the other is equipped with a non Gaussian pulse noise component ( With the wireless is very different) , which may be periodic or aperiodic ( FIG. 1) 。 Power line interference from other devices on the network, or other communication network can be divided into narrowband interference or broadband interference. Industrial machinery, washing machines, refrigerators, for example, the use of induction motor there are often many circulating stationary noise. Widely used in mobile phone and laptop charger switch mode power supply noise. Because the wire is physical media, they will be affected by the branch; Even in the same house, a certain point in the network impedance will and other parts of the impedance is quite different. Through to, shut off equipment can instantly change a certain point in the network impedance. Under normal circumstances, the scope of the wire impedance is 0. 1 to 200 & Omega; 。 In a nutshell, wire channel is complex and noisy. Figure 1 and figure 2 illustrates the G3 - PLC modems - in time domain and time Frequency domain noise must endure wire.

figure 1: the industrial architecture typical wire noise in time domain capture ( 一) The original wire and noise samples, b） G3 - PLC modems Cenelec ‐ A noise spectrum wire

: (figure 2 一) The original wire noise time frequency spectrograph noise of complex structure shows the wire. Pay attention to all kinds of cycle stationary noise component and its spectral content; ( b） G3 - PLC modems can see Cenelec ‐ wire noise in A band. Pay attention to between 62 and 72 KHZ frequency range 120/240 hz noise component is 50 db.

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