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WATER METERING 1 kV. Good analog circuit design techniques suggest the implementation of pulse-proof series resistors R1 and R2 to prevent the transceiver’s internal electrostatic discharge (ESD) circuitry from shunting the external transient voltage suppressor (TVS) diodes, which can occur when the TVS clamp voltage exceeds the trigger voltage of the internal ESD circuit. Also, a high-voltage capacitor, CHV, is used to divert the transient energy from isolated circuit ground towards protective Earth Also, a high-voltage capacitor, CHV, is used to divert the transient energy from isolated circuit ground (GNDISO) towards protective Earth (PE) which is commonly connected to equipment chassis. An optional high- voltage bleeder resistor, R HV , can prevent static charge build-up on GND ISO . Conclusion Modern POLCOR transceivers, such as the SN65HVD888, enable e-meter networks to perform cross-wire fault corrections automatically. This correction is typically performed at power-up and then latched for all further transceiver operations. The SN65HVD888 also has high ESD and electrical fast transient (EFT) immunity ratings. Adding external transient suppressors extends this immunity to severe lightning strikes. Texas Instruments provides a wide portfolio of RS-485 transceivers with high ESD and EFT ratings, some of which even contain integrated transient suppressors. MI References • Download the SN65HVD888 data sheet • Interface Circuits for TIA/EIA-485 (RS-485), Application Report (SLLA036), Texas Instruments, August 2008 • RS-422 and RS-485 Standards Overview and System Configurations, Application Report (SLLA070), Texas Instruments, May 2010 • TIA/EIA-485-A, Electrical Characteristics of Generators and Receivers for Use in Balanced Digital Multipoint Systems • TIA/EIA-TSB 89, Application Guidelines for TIA/EIA-485-A • DL/T 645-1997 Multi-function watt-hour meter communication protocol, People’s Republic of China, Ministry of Electricity ABOUT THE AUTHOR: Thomas Kugelstadt is a senior systems engineer with Texas Instruments. He is responsible for defining new, high-performance analog products and developing complete system solutions for industrial interfaces with robust transient protection. He is a Graduate Engineer from the Frankfurt University of Applied Science. 24 PROJECT H2O THE MADISON WISCONSIN ADVANCED METERING PROJECT Briefly put: Wireless AMI is making it possible for Madison Water Utility to provide metered readings from their customers in a more timely fashion; however the implementation of the project has had other (unexpected) benefits. Madison Water Utility (MWU), Wisconsin, recently finished upgrading customer water meters to a wireless AMI network that reads and transmits water consumption on an hourly basis. The project has seen more than 67 800 new metering systems installed in homes and businesses across Madison and allows MWU to remotely access and analyse meter data. ‘Over the next several months, we will be phasing in a new online tool that uses detailed data provided by the Project H2O system to give customers the information they need to monitor their own conservation efforts. Customers will even have the option to be alerted when usage goes over a specific number of gallons,’ says Robin Piper, Customer Service Manager for MWU. Reasoning for the move to AMI AMI was examined as an option as the utility wanted to move from semi-annual billing to a more regular billing schedule. The previous metering regime had seen three full time meter readers working on a rotational basis and covering readings across the six utility areas, which service more than 250 000 people across the city of Madison, village of Shorewood Hills, town of Blooming Grove, village of Maple Bluff, parts of the city of Fitchburg, the town of Madison and the town of Burke. As an added impetus to change the metering infrastructure, the remote reading registers which had been widely used in the previous metering programme were no longer being manufactured – hence, the reasons for replacement were two-fold in some cases. ‘We had originally wanted to provide a dollar threshold too, but have decided not to implement this notification now. We bill for multiple services and a dollar notification on water usage may confuse the customer when they receive their bill as water is only about 30% of the entire amount due. The current usage notifications can be set by day, week or month.’ The implementation of what became known as Project H20 was driven by the vision of providing monthly bills, and a desire to provide customers with more information on their water consumption. The utility determined the benefits of the move to an AMI system would include improved cash flow, better resource management, an opportunity to improve customer service, better access to data and the chance to become an industry leader. Additionally, the utility didn’t have sufficient clarity on the actual amounts of non revenue water (NRW) in the area and were confident that the increased amount of data would mean more clarity on where the water was being delivered. In 2011, about 76 million gallons of water were lost to consumer leaks; however, because of Project H2O, that’s been changing. The project has involved retrofitting 90% of MWU’s customers’ existing meters, using the services of a subcontractor and replacing 10% with new smart meters using MWU staff. The retrofitting was easily accomplished and the meters that were replaced were done so as part of MWU’s 12 year change-out schedule. One of the changes that has been implemented in terms of the billing is that the amount reported is in US gallons instead of hundred cubic feet (ccf ), as MWU wanted to help customers understand what they are using in practical terms, and not as an abstract value. The meter data has been integrated with the utility’s SCADA and GIS systems, and it was initially thought that this would require a project time-line of 5 years. However, MWU wanted to get the project up and running within a 24 month period and has successfully managed to do so. LESSONS LEARNED: Lesson 1: Effective communication is key MWU discovered that internal communication was as important as external communication. Says Robin METERING INTERNATIONAL ISSUE - 5 | 2014