Sentec steps up to the Disconnect Challenge
Sentec’s product development team recently designed, prototyped and produced a 200A remote disconnect smart electricity meter for US metering giant Sensus. The project involved a number of tough challenges, with stringent technical specifications, physical size and cost points to be achieved.
“Sensus’ long-time partnership with Sentec provided a high level of confidence that a design in collaboration with Sentec would provide a high quality and reliable iConA metering product. Sensus’ confidence was rewarded with an industry-leading product that met all specifications and regulatory requirements, and that accelerated our time-to-market.”
Gregory Myers, Director, Electric Meter Engineering, Sensus
Designing an electricity meter rated to run at 200A is challenging enough, but this task involved stringent requirements:
- to be a “Smart” meter incorporating multiple communications interfaces
- the metrology capabilities of a commercial meter
- be able to mechanically disconnect the two power phases by radio control
- to fit within the space envelope of a standard kWh only meter
- a tight cost target that enables a roll out of remote disconnect meters to every residence
- to comply with ANSI limits that dictate a maximum temperature rise when running at rated current, (a level that many off-the-shelf switches approach when measured in isolation, let alone when fitted within the meter).
Sentec investigated the key issues that have caused previous products to fail, including the internal resistance, mainly resulting from resistance of the electrical contacts within the switch and the copper losses due to small cross-section busbars through the sensor region of the meter. We then proposed a series of design rules to meet Sensus’ needs from initial test all the way through to end-of-life (a requirement of ANSI).
The new meter included a modified approach to Sentec’s tried and tested Mobius sensing technology. Additional development included redesigning the magnetic actuator so that the force on the contacts of the switch was constant over a large distance. This novel actuation method led to a patent application being filed.
Sentec also redesigned the layout of the main switch contacts, passing the rigorous ANSI short circuit tests. This is also the subject of a patent application in its own right.
Apart from one radio communication board that Sensus required, every part of the meter was conceived and designed from scratch by Sentec.
Sensus’ 200A RD iCon meter is already operational in over one hundred thousand installations in North America. Along with passing all applicable American National Standards Institute (ANSI) testing, the switch performed very well during an independent disconnect switch study conducted by the National Electric Energy Testing Research & Applications Center (NEETRAC) on behalf of several utilities.
Furthermore Sensus has in its IP portfolio the new proprietary technology and IP developed by Sentec.
- Case Study
A Custom Smart Electricity Meter for the UK market
As part of this customisation challenge, they chose to incorporate Sentec’s Mobius current sensor, featuring sophisticated and accurate metrology and communications interface. It provides a highly…