AUTOMATIC METER READING

INTRODUCTION : Since it is a tedious job to measure the meter reading of all customers, may it be electricity, water or gas. Some one must be employed to go to each client installation and then take reading on a book, then all the reading or collected data must be entered into a computer for processing. AMR is the solution to this problem. So, next comes what actually is this automatic meter reading ? Although there are various definitions, Automatic meter reading is generally regarded as the reading of a utility meter by a means that doesnot require physical access or visual inspection of the meter. AMR is usually used to collect data or readings of water meter, gas meter or electricity meter. They are used along telephone lines and also over electric power lines. Use of AMR depends on the utility that is making use of it. The data collected from the AMR can be transmitted over a variety of communication media including telephone, power lines, satellite, cable and radio frequency. Earlier AMR devices just collected meter readings electronically and matched them with accounts but as technology advanced, additional data could then be captured, stored and transmitted to the main computer and often the metering devices could be controlled remotely. And most important AMR are the transition from electro-mechanical energy meters to completely electronic meter. HISTORY : The primary driver for the automation of meter reading is not so much to reduce labour costs, but to attain or obtain data that is otherwise unattainable. Many meters, are located in areas that require an appointment with the home owner. Gas and electricity tend to be more valuable commodities than water, and need to offer actual readings instead of estimated readings can drive a utility to consider automation. While early systems consisted of walk-by, and drive by-AMR for residential, telephone based AMR secured well for commercial or industrial accounts. What was once a need for monthly data became a need for daily and even hourly readings of the meters. Consequently, the sales of drive by and telephone AMR has declined in the US, while sales of fixed network has increased. The US energy policy act of 2005 asks the electric utility regulators consider the support for a “Time based rate schedule to enable the electric consumer to manage energy use and cost through advanced meter and communication technology. So, the trend now is the use of advanced meters as a part of an advanced metering infrastructure. DEFINITION : AMR : - As given earlier, it is regarded as the reading of a utility meter by a means that does not require physical access or usual inspection of the meter. VARIOUS DEFINITIONS OF AMR : In particular AMR is defined as a technology of automatically collecting data from water meter or energy meter (i.e., gas, water, electricity) and transferring the data to a central database for billing and or for other analysis. this saves employee trips, and means that billing can be based on actual consumption rather than on estimate based on previous consumption, giving customers better control of their use of electric energy, gas usage or water consumption. When used with power line communication, AMR is a method where electronic data is transmitted over power lines back to the substation, then relayed to a central computer in the utility’s main office. This would be considered as a type of fixed network system – the network being distributed network which the utility has built and maintain to deliver electric power. Such systems are usually for electric meter reading. ELEMENTS OF AMR : Meter interface module. Communication system. Central office equipment. METER INTERFACE UNIT (MIU) : The AMR system starts with a meter unit it is a means of translating data from meter dials, into a digital form which is necessary in order to send digital metering data from the customer site to a central point. It is actually a electrical - optical interface with a RAM & program manor. COMMUNICATION SYSTEM : Used for the transmission or telemetry of data and control send signals between the meter interface unit and central office. It can be either a GSM network or Power line. A GSM network in AMR utilises the existing cellular network for data transportation which requires no additional equipment or software, resulting in a significant saving both in time and capital cellular technology utilises an encryption technique to prevent an outside source from receiving the transmitted data. The cellular network provides full two way communications, allowing scheduled reads, demand reads, alarm and event reporting, power outage reporting and power restoration reporting. PLCC is best suited for LT 440V network for detecting outages, tamper events and performing remote disconnect. It uses the same communication lines as communication media so ideally suited for rural or agricultural connections. Communication of HT side can be implemented using or via a choice of GSM. CDMA, RF or PSTN. CENTRAL OFFICE EQUIPMENT : The central office equipment includes Modems Central server Client software for data acquisition and data analysis. AMR COMMUNICATION : It is divided into 3 based on environment. Urban areas Rural areas Sub – rural areas. WORKING AND OPERATING PRINCIPLE : The remote automatic meter reading system is a host driven, multi-level network system consisting of a host central station (HCS), Data Concentrator unit (DCU) and meter interfacing unit (MIU) with built in flexibility and expandability. Each HCS, while working independently, can also be integrated with an existing corporate information management system through software interface. With additional hardware and software support, the HCS can function as a workstation in an existing local area network (LAN) and member of the entire system or several HCS can be connected together to form a network of their own. OPERATING PRINCIPLE : The Communication device for the PLC communication system is a built in power line Modem (PLM), which transmits and receives data over the power line. Both the MIU and the DCU contain the PLM device. The binary data stream is keyed onto a carrier signal by means of the frequency shift keying (FSK) technique. The central frequency is shifted to 0.3KHz to represent 1 or 0 of the power line by the PLM. At the receiving end, an identical PLM will detect the signal and convert it back to a binary data stream. Two way communication between DCU & MIU is essential in establishing a proper communication channel, for system synchronisation and status reporting. In AMR’s, transmission speed is not a great concern but reliability is important. The data rate of the PLC Channel is set at 600 bps, to ensure communication over a longer distance and reduced transmission error. Every MIU is also equipped with a repeater function. If required, the DCU can designate any MIU in a sub-system as a repeater to enhance communication with a particular MIU with the sensitive signal detection and sophisticated digital filtering technique, this PLC communication is highly immune to electrical noise and interference. PLC SCHEMATICS Power line communication is the most economically viable technology for transferring meter data to DCU. It actually makes use of an ASIC which accepts digital data of concerts it into FSK modulation and transmits it over the power line by sensing a zero crossing of 220V size wave and typical frequency used for freq modulation is 132KHz. SIGNAL, DATA AND INFORMATION FLOW : The MIU, is an intelligent device, which can collect, process and record power consumption data from electric meter. It picks up the pulse output of the meter and concerts the measurement of the meter into a digital format suitable for data processing. This it is possible to monitor the electrical load in real time. The MIU saves the data collected from the non volatile memory, and all data and setting are protected against power failure. It will automatically resume normal operation when power returns after a power failure. After receiving a multi-rate tariff command and loading the time-or-use table from the DCU, the MIU will process energy consumption data according to pre-set time intervals. It will update the peak values and their time of occurrence at each tariff rate providing real time information of electrical consumption for the information management system. Data stored in the MIU are transmitted to the CLU via the power line through the build – in power line moderns (PLM) communication initiated by the DCU, which polls the MIU by calling its address. Data received from different MIU’s are stored in the corresponding load data records in the flash memory of the DCU. The DCU supports communication with any upward equipment in conformity with RS-232 standard, eg a hand held computer. In most cases, the DCU communicates with the remote host central station through standard modern via the existing telephone line or GSM network. The host control system (HCS) is the control center of the system, where all the functions of the system are controlled and monitored. The HCS passed instructions and information requests onto the data concentrator unit (DCU) by calling their address (or the telephone no’s in case of a public switched networks) and the DCU will respond accordingly. The address codes (telephone No) of the DCU’s are stored in the HCS with sufficient mass storage theoretically all DCU’s can be covered by the HCS, in actual fact the maximum number of DCU’s can be connected to the HCS is almost 1000 as it will be limited by the required response time and efficiency of data management. In case of failure in self-diagnostics or any abnormal behavior of the MIU’s, the DCU can also make requests to report by dialing to the HCS the HCS will convert the data received into a test file compatible with the corporation’s existing meter reading management system, and store it in the hard disk drive. File transfer between the HCS and the corporation’s MIS system can be done through standard input / output ports, such as RS-232. AMR BLOCK The DCU and all the MIU’s and meters connected to it can be considered as a sub-system of the HCS. The sub system is set up with the DCU monitoring the low voltage power zone down stream of a distribution transformer. The DCU can be viewed as the front end of the sub system, collecting meter readings from all the MIU’s connected to it through the low voltage power line carrier (PLC) and communicating with the HCS through the communication channel. There are two types of MIU’s a single – channel type connected to a single meter only and a multi channel type, which can be connected up to 16 meters. In projects where meters are scattered in an open area single channel MIU’s are usually used for individual meters, but where projects are plugged together in a meter room or cabinet, Multi-channel meter interface units (MMIU) are most cost effectives. TYPES OF AMR : Hand held AMR In this type of AMR, a meter reader carrier a hand held computer with a built in or attached receiver / transceiver (radio frequency or touch) to collect meter reading from an AMR capable meter. This is some times referred as walk by meter reading since the reader walks by the location. Where meters are installed they go through their meter reading route. Hand held computers may also be used to manually enter reading & without the use of AMR technology as an alternate but this will not support exhaustive data which can be accurately read using the meter reading electronically. Mobile AMR Mobile or “Drive-by” meter reading is where a reading device is installed in a device. The meter drives the vehicle while the reading device automatically collects the meter readings. Often for mobile meter reading the reading equipment includes navigational and mapping features provided by GPS and mapping software. With mobile meter reading, the reader does not normally have to read the meters in any particular route order but just drives the service area until all meters are read components often consists of laptop or proprietary computer, software, RF receiver / transceiver and external vehicle antenna. Fixed networks. Fixed network AMR is a method where the network is permanently installed to capture meter reading. This method can consist series of antennas, towers, collectors, repeaters or permanently installed infrastructure to collect transmission of meter readings from AMR capable meters and get the data to a central computer without a person in the field to collect to it. Some fixed networks systems are also capable of being installed as a HYBRID AMR systems where mobile and fixed network are intermixed by design. In a hybrid system, part of the system is read by fixed network and parts may read by mobile or other technology or both. Utilities with low densities rural areas may not cost justify the fixed network infrastructure for parts of their service area, using it only for reading of a meter by both methods concurrently as a source of redundancy. In the event of failure of the network due to a natural disaster, sabotage, power failure or other network interruption the mobile reading system is available in their disaster recovery plan as an alternative means of data collection to the fixed network. LEVELS IN AMR : There are 4 levels in AMR system Level 1 – Meters. Level 2 – Communication. Level 3 – AMR Systems. Level 4 – Energy company processes. APPLICATION FIELDS : To Control congestion. For remote control services. To improve energy management. Low power. ADVANTAGE / BENEFITS OF AMR : Accurate meter readings, no more estimates. Improved billing. Improved security for premises. Tariff Control. Improvement in cost. Better and faster customer service Flag potential high consumption before consumer gets a high bill. Accurate measurements of transmission losses. More intelligence to business planning. Remotely connect / disconnect power supply through meter. DISADVANTAGES : Communication costs. Exceeded general cost. Malfunctions. Short life cycles of technology. Disturbance and virus attack etc., AMR COST : Doctor of technology Anssi Seppala has estimated the cost division of the cost of AMR project. 50% - Installation. 15% - Maintenance. 15% - Telecommunication. 10% - Reading system. 5% - Training and development. 5% - Others.