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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