Design and Implementation of Smart Billing and Automated Meter Reading System for Utility Gas

Design and Implementation of Smart Billing and Automated Meter Reading System for Utility Gas Muhammad Faheem Khan, Ahmed Zoha and Rana Liaqat Ali Department of Electrical Engineering, COMSATS Institute of Information Technology, Islamabad (CIIT)-Pakistan E-mail: faaheemkhaan@gmail.com, muhammad_fahim@comsats.edu.pk Abstract Billing automation systems for public utilities (e.g. electricity, gas and water) have been widely studied and implemented in developed countries across the world. But in Pakistan, this technology is still on its way to be implemented for domestic as well as for industrial consumers. This paper explores the design, implementation and application of billing automation system for gas consumers in Pakistan. For low gas consumption (domestic consumers), a prepaid meter has been designed which needs a prepaid card to keep the gas supply continue. Similarly for high gas consumption (industrial consumers), the gas meter is wirelessly connected with the regional billing office. In this way the billing office is able to directly communicate with the meter and records its gas consumption reading. Along with the gas, this system can easily be enhanced to measure the consumption of electricity and water. enters the meter readings in a computer to calculate the bills. Thirdly at the end, the bills (in paper form) are sent home to home (to gas consumers). The above stated process is manual and prone to defects and ultimately the consumers mentally and financially suffer in such billing system. Therefore to replace the manual and traditional billing techniques in Pakistan, we designed and implemented a cost effective, but still reliable, billing automation system for gas provider companies. As already discussed that analogue meters are already being used in Pakistan therefore in our system we modified an analogue meter and converted it into a digital gas meter. In this way the gas provider companies would not have to completely replace their existing setup facilities and they would be able to replace their existing billing methods with our automated system. 2. System Configuration There are three major modules of this system: 1. Introduction The Automated Meter Reading (AMR) was started in 1962 by AT&T, but this experiment was not successful. The modern era of AMR started in 1985; since then different techniques have been utilized to get better reliability and performance [9]. Therefore currently in developed countries, many successful AMR systems are being used to facilitate the consumers of water, gas or electricity. However in Pakistan, service provider companies (e.g. WAPDA, SNGPL, WASA, etc) are still using analogue meters and manual billing systems. Such type of billing method is being used both for domestic consumers as well as for industrial consumers. Basically using this system the bill is calculated in three steps. Firstly meter readers (human being) go home to home to manually record the meter reading. Secondly all readings are sent to regional billing office where data entry operator, 2.1. Analogue Meter with AMR Module This module incorporates separate designs for domestic consumers and industrial consumers. For domestic consumers we designed a prepaid billing system which excludes the human meter reader and data entry operator. While for industrial consumers, the gas meter is post paid but still the technique to record its reading is automatic. 2.2. Data Communication System This module has been specifically designed for industrial gas consumers, which wirelessly communicates with remotely operated gas meters and record their reading, which are ultimately sent to the regional billing office to calculate the gas consumption bills. 2.3. Data Logger Billing Office Software for Regional For regional billing office we designed software which automatically receives the meter reading from the remote consumers, calculates the bill and wirelessly transmits the gas bills to the consumers. In next section we would separately discuss domestic and industrial billing. devices. They are suitable for measuring natural gas and a variety of technical gases at up to 0 .5 bar. The approved gas temperature range is -20 °C to +50 °C [11]. Outlet Inlet Valve Mechanism 3. Domestic Billing: Currently in Pakistan, diaphragm gas meters are being used for domestic as well as for industrial users. These are of following specifications [6]: • Residential-class diaphragm meters are rated at the ½ inch Water Column (WC) differential. • Intermediate and large-capacity diaphragm meters can have both a ½ inch WC rating as well as a 2 inch WC differential rating. In our automated billing system, we implemented a prepaid billing method for domestic users. Here we utilized an already being used residential class analogue diaphragm meter. EEPROM Mechanical to Digital Encoder Prepaid Card Writer/Reader Processing Module Prepaid Balance Comparater Schmitt Trigger Keypad Digital Pulse Counter Diaphragm Back Chamber Fig.2. Internal Structure of Meter Inside the meter, a cast iron cylinder is divided into two compartments by a flexible diaphragm (Fig.2), which extends or retracts when the compartments are alternately filled or emptied. This motion operates the counter mechanism [13]. The digital meter has following specifications: Table 1. Specifications of Prepaid Gas Meter Specification Maximum flow rate Minimum flow rate Maximum working pressure Long term running property 3.2. Display Gas Supply Valve Fig.1. Block Diagram of Domestic Gas Billing Digital meter is primary part of domestic billing system; its hardware details are explained in following sections. 3.1. Internal Structure of Digital Meter Front Chamber Value 2.5 m3/h 0.016 m3/h 1 bar No pressure leakage under 15 kpa Counting Mechanism The counting mechanism is responsible to record the consumption of gas (in cubic meter per hour-m3/h). Then this reading is used to calculate the gas consumption bill. The higher the number of revolutions to measure a cubic meter, the faster the meter is operating, the greater potential for increased component wear resulting in reduced meter life. The measuring device may consist of pistons diaphragms or of a fan wheel driven by the pressure of the gas and connected to a counter mechanism [12]. It is a positive displacement meter operated by using mechanical divisions to displace discrete volumes of gas successively. All versions of positive displacement meter are low friction, low maintenance and long life Fig.3. Meter’s External Dial. edges of gears are not smooth that’s why the output pulses contain some ripples. Before inputting these pulses into pulse counter, this was very important to remove these ripples. Therefore we used pulse conditioning through Schmitt trigger. Amplitude The gas meter consists of a box divided in two compartments by a partition (Fig.2). Each compartment is itself divided by a central diaphragm; the gas passes successively in and out of these four compartments. The alternating motion of the diaphragm drives the assembly of gears. Then these gears rotate the wheels of digits (Fig.3) [13]. Fig.4. Meter’s Internal Gear Assembly Although the gas consumption is shown in digits (so digital output of meter) but like digital systems this output can’t be fed into some other digital systems to save it or read by AMR technology. Therefore it was necessary to digitize the analogue output of this meter. This is explained in next section. Fig.6. Digital Encoder and its Output 3.4. Pulse Conditioning In our case, the ripples have high frequencies as compared to the original waveform therefore we passed this waveform from the Schmitt trigger circuit to get a pure digital waveform (Fig.7). 3.3. Digitization Unfiltered Digital Signal Schmitt Trigger Amplitude The digitizing mechanism of an analogue meter is the primary conversion from conventional analogue method to a prepaid gas meter. Ultimately this feature greatly enabled the meter to communicate with other digital devices e.g. Remote Terminal Unit (RTU), Prepaid Card Reader etc. To digitize the meter, an encoder was designed which encodes (converts) the gas consumption into cubic meter. This was done by making precisely spaced holes in the main gear of the meter. Then one IR transceiver was fitted across the main gear. Now while operation, as the gear rotates, the encoder calculates the digitally calculates the gas consumption. Time Time Ripple Free, Filtered Digital Signal Fig 7. Schmitt Trigger, Filtering the Ripples In case if pulse conditioning is not used then as a result of one pulse the pulse counter triggers more than ten times because it also senses the ripples and take them as a complete logic. This results in wrong bill calculations. That’s why its is necessary to use Schmitt trigger so that as a result of one pulse, the pulse counter should count only once. 3.5. Calculating the Gas Consumption Fig.5. Main Gear, Fixed Inside the Meter Using analogue to digital encoder, the meter provided the digital output shown in Fig.6. But as the The digital meter is supposed to output digital pulses. That is why in our existing meter we converted the revolution of gear into electrical pulses. In other words, at deeper level these pulses are responsible to 8.7cm calculate the gas consumption. In normal meters when one gear rotates one revolution, the counter indicates 1m3 gas consumption. But in digital meter one revolution of gas meter is equal to ten pulses.. Therefore when ten pulses are received to the processor of meter, it displays (on LCD) that 1 m3 gas has been consumed. This is also shown in following simple mathematical relationship: 1 revolution (of gear) = 1 m3 gas consumed 1 revolution (of gear) = ten electrical pulses So Ten electrical pulses =1 m3 gas consumed Note: As mentioned in previous paragraphs, that ripples are necessary to be eliminated. But if we don’t eliminate/reduce them (i.e. if we don’t use Schmitt trigger) then 1-gear revolution would be equal to more than ten electrical pulses. There may be case that 1gear revolution would be equal to 50 or more electrical pulses. Therefore the result would be an absolutely wrong calculation of gas consumption. 3.6. Gas Flow Control Valve If prepaid balance is not enough, the meter has ability to shutdown the gas supply by energizing its solenoid valve. This valve is specially designed to stop the flow of liquid/gas passing through it (Fig 8). This valve is operated at 12W Power (12 V, 1A). When gas supply is needed to stop, the controlling circuitry energizes the amplifier, resulting in activating the relay and turning OFF the valve. Internal Solenoid Outlet Inlet Fig.8. Gas Flow Control Valve 5.5cm Copper Contacts Fig.9. P-Card Layout Unlike many other prepay cards this card is reprogrammable. This feature is useful for the gas supplier company. Because after using, the customers would not throw the card and unloaded card would be returned back to the company. This would help in saving manufacturing cost of the card. Currently the manufacturing cost of this P-card is Pak Rupees: 45 (0.75 US$). 3.8. P-Card Programmer P-Card was designed to facilitate the gas provider company, which is providing gas to domestic consumers (with low gas consumption). This programmer would enable the company to reload/ reuse its P-cards. 3.9. P-Card Meter Charging To charge the prepaid gas meter, the P-card is inserted into the specific slot. The sensor inside this slot can identify that whether the card is inserted in proper way or not. Then password is entered using keypad, fixed at the front panel of meter. On entering correct password, the P-Card reader reads the balance in the memory of P-Card and then it copies all of the contents into the memory of the meter. In this way the initial balance into the memory of meter is added with the newer figures (Fig 10). After copying contents of the card, the P-Card Writer washes all of the contents the P-card, so that this can’t be used next time. 3.7. P-Card The P-Card is a reprogrammable contact smart card with memory. In the name P-Card, the P stands for Programmable and Prepaid. In digital gas meter, this card plays vital role because this holds gas units (meter cubes) in the form of digital numbers. It also holds an eight-digit password (Fig 9). While charging the meter, the copper strip establishes contact of card circuitry with meter circuitry. In this way it becomes very easy to charge/recharge the meter Processing Unit Fig.10. Meter Charging Process Through P-card 4. Industrial Billing 4.3. Data Logger Software As industries use larger amount of gas/day than a domestic user, therefore the prepaid meter was not feasible. That’s why we wirelessly connected the digital gas meter with the gas billing company. The different modules of industrial billing are discussed below. This part of automated billing is responsible to receive meter reading, calculate bill and then send back the bill to the consumer. It further consists of four parts (Fig.12 and Fig.14): 1. Data Receiver (Receives meter reading from consumer site) 2. Bill Calculator (Calculate gas bill at central gas billing office) 3. Bill and Notifications Transmitter (Dispatch gas bill to consumer site) 4. Software Information (Names of System & Authors) 4.1. Remote Terminal Unit (RTU) The RTU is a hybrid of hardware and software and contains many functional modules. The RTU is providing connectivity with outer world by GSM network (GSM modem is incorporated). The main function is to provide generic solution for telemetry and telemetics. Currently it is being used for remote monitoring (remote data acquisition) and remote control (turning ON/OFF the gas meter). Start Master Controller No GSM Modem working Yes Equipment Reporting Available SIM Space No Yes No Display and Turn On Buzzer SMS Received Low Battery Level Yes SMS Presence Detector No Display and Turn On Buzzer Fig.11. Overview of Industrial Billing Find SMS location in SIM Memory Read New SMS 4.2. Data Communication System The RTU transmits data (meter reading) using GSM network of any mobile service provider. For this purpose a Subscriber Identity Module (SIM) is used. After transmission, the data is received in the central/regional billing office. The GSM Modem uses specific antenna to wirelessly transmit the data to the central/regional billing office. Following are the specifications of antenna. Table 2. Specifications ofOmni GSM Power Antenna3db GSM Model Antenna Frequency Range 890-960 MHz Gain 3dBi peak Impedance 50 ohms Beam Pattern 360 Degrees Wind Survival Rating 100kph Verify Password of RTU No Display “Error” Yes Take Action Change Password Activate AMR Module Turn On/Off Gas Meter Record Meter Reading AMR’s Recording Module Record Time Record Temperature Transmitter Data Fig.12. Software Flow Chart of RTU Prepaid Card Writer/Reader EEPROM Mechanical to Digital Encoder Processing Module Prepaid Balance Comparater Schmitt Trigger Keypad Digital Pulse Counter Display Gas Supply Valve SIM Card GSM Modem Remote Terminal Unit Fig.13. Hardware Flow Chart of RTU Meter Communication Server SIM Number Data Receiver Storing Raw Data Display Meter Serial Number Meter Current Reading Date and Time of Meter Current Temperature Data Receiver Database Monthly/Annual Graph Display Bar or Pie Graph Gas Consumption Graph Total revenue graph Gas Bill Amount Notifications Time and Date Previous Reading Current Reading Difference of Readings Current Bill Transmission Bill and Notification Transmitter Adjusting Last Date of Bill Submission Fig 14: Hierarchy Chart of Data Logger Software View publication stats This paper explored separate billing solutions for domestic and industrial gas consumers. For domestic consumers we designed a prepaid billing system while for industrial ones we designed a postpaid but wirelessly (GSM) controlled billing system. Such system minimizes the human intervention in meter reading, bill calculations and bill delivery which ultimately reduces many defects, currently existing in conventional manual billing systems. This system was specially designed for Pakistan but can also be implemented in any other country, where initially manual billing is being used. 6. References EEPROM RTU Master Controller 5. Conclusion [1] B. S. Koay, S. S. Cheah, Y. H. Sng, P. H. J. Chong, P. Shum, Y. C. Tong, “Design and Implementation of Bluetooth Energy Meter”, Nanyang Technological University, ICICS-PCM, 15-18 Dec 2003, 3A6.7, Singapore pp.1474-1476 [2] T. Meek, P. Chilese “Remote Meter Reading by Radio - A European Perspective” Schlumberger Industries, UK. pp 196-198 [3] Carl Brasek “Urban Utilities Warm Up to the Idea of Wireless Automatic Meter Reading” IEE Computing & Control Engineering December / January 2004/05, pp.11-13 [4] Yan Liu, Rochelle A. Fischer and Noel N. Schulz, “Distribution System Outage and Restoration Analysis Using A Wireless AMR System”, 2002 IEEE, pp. 871-874 [5] Tian Yew Lim and Tat-Wai Chan “Experimenting Remote Kilowatthour Meter Reading Through Low-Voltage Power Lines at Dense Housing Estates” IEEE Transactions on Power Delivery, VOL. 17, NO. 3, July 2002. pp. 708-711 [6] Paul G. Honchar Sensus Metering Systems DuBois Pan “Diaphragm Meters Applications, Installations and Maintenance” 43rd CGA Gas Measurement School, June 1-3, 2004. [7] Terry Chandler “The Technology Development of Automatic Metering and Monitoring Systems” Terry Chandler Director of Engineering Power Quality Thailand LTD and Power Quality Inc USA [8] http://www.energycite.com/amr.htm [9] www.elster-instromet.com/en/diaphragm_meters [10] http://www.dncustoms.gov.vn/web_Eglish/BIEU_ THUE/E_HTM/E9028.htm [11] http://www.pipelineandgastechnology.com/0106u tilityoperations.html [12] http://www.dncustoms.gov.vn/web_Eglish/BIEU_ THUE/E_HTM/E9028.htm