THE ELECTRICAL ENERGY MEASURMENT DATA ACQUISITION ENGINEERING BASED ON SCDMA
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30-10-2010, 10:44 AM


THE ELECTRICAL ENERGY MEASURMENT DATA ACQUISITION ENGINEERING BASED ON SCDMA
Presented by
JAYAKRISHNAN S R
S7 E1
College Of Engineering, Trivandrum
2007-11 batch



.docx   THE ELECTRICAL ENERGY MEASURMENT DATA.docx (Size: 804.49 KB / Downloads: 141)

Abstract

The electrical energy measurement data is the basis of estimating electrical energy supply and sales related cost; also it is important information which analyzes the loss of electrical energy transmission and the efficiency of electrical energy consumption. The electrical energy measurement stations are not only distributed among buildings and the streets in the urban areas, but also have been disperses extensively in rural regions such as in the fields and along mountainous areas. Due to the features of dispersed measurement stations, it needs an efficient data-collecting network, which is with large capacity and coverage, to achieve the automatic collection of long-distance measurement data. SCDMA is a kind of wireless communication technique, where SCDMA stands for Synchronized Code Division Multiple Access. SCAMA cellular network is widely used in the engineering construction and have remarkably solved the base station selecting and signal coverage designs that are associated with SCDMA wireless network establishment, and they help to cope with the connection problems of electrical energy measurement data collection center, enhancing the real-time of electrical energy measurement data collection and building up excellent foundation for analyzing the loss of electrical energy transmission and the efficiency of electrical energy consumption.

Introduction
Due to the significance of the electrical energy measurement data in the electrical energy supply and sales chain, to realize the AMR (Automatic Meter Reading) is helpful to the exact management of energy consumption, and rapidly reflecting the market movement. Also AMR benefits constituting of the flexible electrical energy price policy, which can stimulate the rational consumption and energy saving.Electromechanical meters have technical, social, and management problems. The technical problems are manifested by the moving parts of an electromechanical meter, which cause wear and tear vis-à-vis its magnetic component whose operation depends on prevailing temperature. These culminate into errors which degrade the reliability and accuracy of the meter over time. The manual reading of electromechanical meter for the purpose of billing is fraught with many social and management problems.Some of these problems are possible lock-out of a meter from easy accessibility, human error in reading, gross inaccurate estimated reading, controversial billing, lack of information on detailed breakdown of energy consumption over a period of time, irregularities in billing time, tampering prone, high overhead cost of meter reading, and possible misplaced paper bill. The existing manual method of disconnecting the power lines to the meter has its own wagon of disadvantages ranging from exposure of the meter readers to corrupt practices,illegal reconnection of the power lines, bypassing of the energy meter, and very weak conditional access enforcement.There are millions of existing electromechanical energy meters in the developing worlds which may be difficult to discard by the introduction of a more enviable all digital electronic meters. Hence, a technique which can marry the advantages of digital electronic energy meter without significant modification of the existing meters will be most welcome.

Electromechanical energy meter

An electromechanical energy meter consists of a series connected load current sensing electromagnet, and a parallel connected load voltage sensing electromagnet. The two fluxes produce by the electromagnets induce emf in a disc resulting in an eddy current. The reaction between the fluxes and the eddy current causes a driving torque on the disc which makes it to rotate. Hence, electrical power is measured by the multiplying effect of the induced fluxes. The measured power is converted to energy by a set of five or six mechanical gearing system connected in tandem, with each carrying a dial ,driven by a rotating disc. Each dial is calibrated into ten divisions, and advances by 1/10th of a revolution for each complete revolution of its adjacent dial in the tandem. The energy consumed is recorded by counting the number of complete revolutions made by the rotating disc, a complete revolution measure a unit of electrical energy in KWh. Therefore, a typical electromechanical energy meter displays the energy consumed in units of KWh as 10000, 1000, 100, 10, 1, 1/10 digits.

Disadvantages of electromechanical energy meter

Electromechanical meters have technical, social, and management problems. The technical problems are manifested by the moving parts of an electromechanical meter, which cause wear and tear vis-à-vis its magnetic component whose operation depends on prevailing temperature. These culminate into errors which degrade the reliability and accuracy of the meter over time. The manual reading of electromechanical meter for the purpose of billing is fraught with many social and management problems. Some of these problems are possible lock-out of a meter from easy accessibility, human error in reading, gross inaccurate estimated reading, controversial billing, lack of information on detailed breakdown of energy consumption over a period of time, irregularities in billing time, tampering prone, high overhead cost of meter reading, and possible misplaced paper bill. The existing manual method of disconnecting the power lines to the meter has its own wagon of disadvantages ranging from exposure of the meter readers to corrupt practices,illegal reconnection of the power lines, bypassing of the energy meter, and very weak conditional access enforcement.

Data acquisition system

Fig 1. depicts the block diagram of the system architecture of the integrated information technology system and electromechanical energy meter. The system architecture consists of five major units, namely, the electromechanical energy meter, the sensor unit, the conditional access monitoring and enforcement unit, the microcontroller unit, and the communication unit. All these units except the electromechanical energy meter constitute the information technology interface between the electromechanical meter and the energy central office. The sensor unit is the only invasive and retrofitted component to the meter. It consists of an infrared emitter diode on one side of the meter’s disc, a hole drilled on the disc which is of the size of the aperture of the emitter diode, and on the other side of the disc is an infrared phototransistor. The emitter diode emits light continuously which is only detected when the hole on the rotating disc align with the emitter and phototransistor. This occurs once per revolution resulting in the phototransistor generating a pulse per revolution . The train of pulses representing the energy in KWh is fed to the microcontroller via a signal conditioning circuitry. The microcontroller unit consists of an 8031 microcontroller, an MC146818 Real-Time Clock module, LCD display module, a 16-key keypad, and a software module. The 8031 microcontroller is responsible for counting the number of revolutions representing the energy consumed, information on the time stamp of consumed energy is available from the real time clock. The schedule for uploading of the integer value of the consumed energy unit for billing purpose is based on the real time clock. The 8031 generates all the control signals required by the relays, phototransistors, the communication unit, keypad, and the display module.











The display module displays the digital energy reading, and the bill, and deadline for bill settlement. The bill can be according to schedule or on demand. The keypad is used for requesting information from the energy central office and time information from the real time clock module. The software package developed in assembly language consists of various drivers, schedules, and host address number for uniquely communicating with the system. The conditional access monitoring and enforcement unit is responsible for cutting off remotely a defaulting consumer, monitoring of illegal attempt to reconnect, and reconnection remotely of the consumer. It consists of a contactor driven by relay activated by the microcontroller; it also has a phototransistor in the its enclosure for effecting tamper proof. If an unauthorized attempt is made to open the enclosure for illegal reconnection the phototransistor is activated which in turn alerts the microcontroller which obtains the time stamp information and uploads it to the energy central office. The feature is deactivated by a password for authorized reconnection. The communication unit is full duplex consisting of a gsm modem interfaced to the microcontroller for effecting bi-directional communicating channel between the microcontroller and the energy central office. A landline telephone modem can also be used, a conventional gsm with RS232 data cable is used in this project and implimentation. The only requirement is that your gsm service provider must support data. A smart card for prepayment and other conditional access feature can be included with this system. The performance of this integrated information technology and electromechanical meter synergy is impressive. Most of the features available from a fully digital electronic meter such as telemetering, tamper proof, loading information for effective planning and management are also available from this synergy. A patent application for this development is being processed.








Communication methods

The main characteristics of electrical energy measurement data acquisition are universal and dispersive. Due to the large amount of the measurement points, and the ruleless distribution of these points, remote automatic collecting of all these measurement points need a data collecting network which should be high efficient, and can provide large capacity and wider coverage. Currently there are some useful data transmission technologies, for example, optical fiber, all kinds of cable wide band networks, PSTN, power line carrier and wireless networks like GPRS, CDMA. But there are always some limitations when all these technologies are used in AMR.
The cable transmission technologies like fiber and all kinds of cable wide band networks can provide large transmission capacity, the signal loss is very low, and have strong anti-interfering capability and good real-time performance. But on account of the reason that the distribution of electrical energy measurement points is dispersive excessively, the high cost of building fiber or cable networks is unacceptable, and it is infeasible to construct fiber or cable lines in some area. Power line carrier networks can be built with the power lines, but power line carrier channel is bad, and there is variational impedance and un-divinable noise interference. The data transmission may be interfered easily. Furthermore, the band and transmission distance is limited. So if the functions of prepay is performed based on power line carrier networks, it is difficult to meet the requirement of real-time and reliability. The public networks like GPRS and CDMA distribute universally, which got high data transmission speed. But as a public network, these networks have to meet the personal communications first, so in some area in which the traffic is large, the band and real-time that electrical energy measurement data transmission need may not be insured.

Characteristics of SCDMA technology

The SCDMA wireless broadband access system can provide both high-speed data and voice services to both fixed and mobile users in NLOS (non-line-of-sight) environments. Thanks to the aforementioned advanced technologies, SCDMA system offers a wider coverage, high spectrum efficiency (up to 15Mbps/5MHz), an efficient combination of high speed and low speed services, low cost terminals, support of high mobility applications, and N=1 deployment. Furthermore, the SCDMA system offers quality of service (QoS) to different types of traffic and grade of service (GoS) to different kinds of users.In contrast , SCDMA is designed to work in those (N=1 deployment) hostile environments thanks to the superb interference cancellation capability, the special design of the frame structure, and dynamic channel assignment schemes[1]. The primary design goal of a SCDMA system is for all users to be received by the base station at the same power level, and to make that power level as low as possible while still maintaining a high quality call. Any more power than needed adds unnecessarily to the overall noise level on the CDMA channel, and cuts down capacity With traditional hard handoffs, which are used in all other types of cellular systems, the mobile drops a channel before picking up the next channel. When a call is in a soft handoff condition, a mobile user is monitored by two or more cell sites and the transcodercircuitry compares the quality of the frames from the two receive cell sites on a frame-by-frame basis. The system can take advantage of the moment-by-moment changes in signal strength at each of the two cells to pick out the best signal.

System structure





Figure 2. Illustration of CHONGQING POWER





As shown in Figure 2. The SCDMA wireless broadband base station is connected with the electrical energy measurement data acquisition centre via IP network. After the electrical energy measurement data acquisition terminal and SCDMA data transfer unit powered on, they will get one IP address. By access that IP address, the electrical energy measurement data acquisition centre can send the control instructions to the electrical energy measurement data acquisition terminal. SCDMA wireless broadband access system has good NLOS transfer capability. Even The 400MHz system can achieve the coverage which radius is more than 50km. The main characteristics of electrical energy measurement data acquisition are universal and dispersive. Currently there are some useful data transmission technologies, for example, optical fiber, all kinds of cable wide band networks, PSTN, power line carrier and wireless networks like GPRS, CDMA. But there are always some limitations when all these technologies are used in AMR. Due to the large amount of the measurement points, and the ruleless distribution of these points, remote automatic collecting of all these measurement points need a data collecting network which should be high efficient, and can provide large capacity and wider coverage. Therefore, it is adapted to be used in the mountainous area. About the capacity, thanks to the small band distribution granularity, the SCDMA system can efficiently surpport the low band demanded services, and a single base station can surpport 300 parallel terminals at most. Accordingly the electrical energy measurement data acquisition system based on SCDMA wireless broadband access technology has the advantage of wider coverage, large user capacity and high efficiency.










Key technology

Smart antennas

Smart antenna is helpful to coverage expansion. With an 8 element antenna array, the beamforming gain can be as much as 18dB for downlink link budget. The smart antenna technology has strong interference cancellation capability as well.SinceSCDMA wireless broadband access technology uses TDD scheme, the nulling can be accomplished for both uplink and downlink to minimize the co-channel interference of neighboring base stations, enabling N=1 deployment.

CS-OFDMA

The SCDMA wireless broadband access system uses CS-OFDMA technology. CS-OFDMA stands for Code Spreading Orthogonal Frequency Division Multiple Access. It is a combination of OFDMA and SCDMA and hence has both benefits of OFDMA and SCDMA(which stands for Synchronous CDMA), that is the robustness of OFDMA to delay spread, and SCDMA is more resistant to intercell interference, which enables N=1 deployment.

Dynamic channel allocation

For N=1 deployment, When we encounter the worst case scenarios where both terminals communicating with different base stations are located at the same places, we use a dynamic channel allocation (DCA) technique to handle such worst cases. The DCA technique first detects such cases and prevents both base stations from assigning the same channels to these two terminals by allowing communication between these two base stations via the backhaul.






Adaptive modulation

The SCDMA wireless broadband access system uses the QPSK, 8PSK, QAM16 and QAM64 modulations. These modulations are adopted depending on the channel conditions, power availability and the interference and noise level to optimize the spectrum and power efficiencies.

QoS and GoS

QoS stands for Quality of Service defining differentiation in the traffic handling. GoS stands for Grade of Service. Through the EMS, we can configure each terminal priority and each service priority.

Security and fraud protection

We have five steps of security and fraud protections as explained below:

Step 1: When the terminal tries to access the network, it must go through the authentication process through EMS.
Step 2: Since the signal delivered to each terminal is done via beamforming, such downlink signal will be extremely difficult to intercept.

Step 3: To access the internet, the terminal will also need to pass the PPPoE server with an account name and a password.

Step 4: The SCDMA system has another important security feature of binding the IP address, MAC address, and Equipment ID. If there is any mismatch of these three addresses, the IP packets will be dropped.

Step 5: The terminal which is assigned a network ID can only access to the specific network.





Design of SCDMA communication network for CHONGQING POWER

CHONGQING POWER SCDMA communication network(phase 1) was constructed with 400MHz SCDMA wireless broadband system, including 1 EMS(Equipment Management System) and 5 SCDMA wireless broadband base stations, which covered four districts of CHONGQING : BiShan, YongChuan, ShuangQiao and RongChang. Physiognomy of coverage area is mostly hill, and the total acreage is 4000sq.km. Phase Ⅰnetwork primarily covers the villages and towns in all the four districts, and the rigions in which there are service points.



Figure 3. Distribution of base stations in CHONGQING POWER SCDMA communication network(phase 1).





According to the electric wave transmission theory and the test data of SCDMA testing base station, we performed the electromagnetic wave spreading analysis, and utilized HATA model and COST-231 model to estimate the coverage area. With the reconnaissance to all the four districts, five station points was determined, including 4 sector stations and 1 omni direction station. The distribution of the five stations is shown in Figure 2, and the information of the stations is listed in Table 1. The coverage of phase Ⅰ network make that the outdoor signal power is more than -90dBm in 80% area of the four districts.


The holistic structure of CHONGQING POWER SCDMA communication network is illustrated in Figure 1. The electrical energy measurement data acquisition centre and SCDMA EMS are installed in the central apparatus room, via backhaul five base station access the Ethernet switch which is located in the central apparatus room. For the security of electrical energy measurement data, the SCDMA network is separated from the electrical energy measurement data acquisition centre by the fire wall.




Terminal interface



Figure 4. Work mode of SCDMA data transfer unit

As shown in Figure 3, SCDMA data transfer unit provides two interface mode : ethernet port and RS232 COM port. While the SCDMA data transfer unit connects with the electrical energy measurement data acquisition terminal via Ethernet port, the data transfer unit works as layer 2 device, and transfers and receives the ethernet data packets. In this case, the electrical energy measurement data acquisition terminal need support TCP/IP. While the SCDMA data transfer unit connects with the electrical energy measurement data acquisition terminal via RS232 COM port, the data transfer unit works as layer 3 device. By the embedded TCP/IP, the data transfer unit automatically setups the IP connect with the network, encapsulates the data received from the COM port in the IP packets, and sends these packets to the electrical energy measurement data acquisition centre. At the same time, the data transfer unit receives the IP packeds from the electrical energy measurement data acquisition centre, unencapsulates the data, and sends these data to the electrical energy measurement data acquisition terminal via COM port. In this case, the electrical energy measurement data acquisition terminal need not support TCP/IP.



Meter data collecting model

Based on the features of high efficiency, large capacity and wider coverage of SCDMA, the meter data collecting based on SCDMA utilize the model shown in Figure 5.


Figure 5. Meter data collecting model

In the electrical energy data collecting points that are concentrative like buildings, SCDMA collector collects the meter data via RS-485 bus, and the meter data will be transmited to AMR main station via SCDMA data transfer network. While the SCDMA data transfer unit connects with the electrical energy measurement data acquisition terminal via Ethernet port, the data transfer unit works as layer 2 device, and transfers and receives the ethernet data packets.




Meter reading mode of AMR main station

The protocol model of the electrical energy measurement data acquisition system based on SCDMA is illustrated in Figure 6 and Figure 7.



Figure 6. Protocol model(via RS232 COM port) of electrical energy measurement data acquisition system

In the case that the SCDMA data transfer unit connects with the electrical energy measurement data acquisition terminal via RS232 COM port, after the SCDMA data transfer unit powered on, it will get a IP address from the DHCP server, or it can use the static IP address which was set in the unit. After the electrical energy measurement data acquisition terminal powered on, it will register to the electrical energy measurement data acquisition centre(AMR Main Station),and the electrical energy measurement data acquisition centre will records the mapping of the electrical energy measurement data acquisition terminal identity and IP address. In this duration in which the terminal is active, the electrical energy measurement data acquisition centre will communication with the electrical energy measurement data acquisition terminal via that IP address.








Figure 7. Protocol model(via Ethernet port) of electrical energy measurement data acquisition system

In the case that the SCDMA data transfer unit connects with the electrical energy measurement data acquisition terminal via ethernet port, after the electrical energy measurement data acquisition terminal powered on, it will get a IP address from the DHCP server, or it can use the static IP address which was set in the terminal. In the electrical energy data collecting points that are concentrative like buildings, SCDMA collector collects the meter data via RS-485 bus, and the meter data will be transmited to AMR main station via SCDMA data transfer network. And then, it will register to the electrical energy measurement data acquisition centre, and the electrical energy measurement data acquisition centre will records the mapping of the electrical energy measurement data acquisition terminal identity and IP address. In this duration in which the terminal is active, the electrical energy measurement data acquisition centre will communication with the electrical energy measurement data acquisition terminal via that IP address.








Advantages

Smart automated processes instead of manual work

Customized rates and billing dates

Detection of tampering of Meters.

Accurate measurement of transmission losses

Better network performance and cost efficiency

Demand and distribution management.


Customer benefits

Precise consumption information.

Clear and accurate billing.

Better and faster customer service.

Flag potential high consumption before customer gets a high bill.

Prepaid use of electric power is possible.

Limitations

High establishment cost

In future use of scdma in tele-communication
may seriously affect the performance.

Server should be capable of processing large
amount of incoming data.

Software updation is necessary

Conclusions

SCDMA wireless broadband access technology is able to meet the demands of high efficiency, large capacity and wider coverage of electrical energy measurement data collecting network. Thanks to aforementioned advantages, in order to cover the wider area in which the measurement points distribute, we need only a small amount of base stations. There are 5,000,000 power users in CHONGQING, and within the framework of State Grid, the amount is more than 170,000,000. It will renovate the operation mode of electrical energy supply and sales chain if that the AMR to these meters is realized. And it is helpful to promote the innovation of electrical energy sales and improve the electrical energy utilization efficiency and consumption level.
A telemetering, tele-billing, and tele-conditional access was crafted into an existing electromechanical energy meter with only a simple sensor module retrofitted invasively to the electromechanical meter. The performance of this integrated information technology and electromechanical meter synergy was impressive with most of the features available from a fully digital electronic meter made available. A smart card could be included in this system for effecting pre-payment.

References

[1] Guanghan Xu, 2007, “Elucidate the evolution of TD-SCDMA from technology origin”, Telecommunications science, 2007(6):1-6.


Research Of The Electrical Energy Measurement Data Acquisition Engineering Based On ScdmaXiaomin XIE Chongqing Electric Power Corp., China


CDMA – An Access Method that Makes a Difference GuanghanXu, 2007, "Elucidate the evolution of TDSCDMA from technology origin", Telecommunications science, 2007(6):1-6.


An automatic smart telemetering tetebilling and tele-conditional access control of electrical energy by IBIYEMI T.S. Dept. of Information Engineering Covenant University, OTA, Ogun State, Nigeria

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