EPRI SE-240 modular open architecture metering goes commercial20 November 2000
Deregulation in electricity supply worldwide has precipitated new demands on the embryonic technology of remote residential metering. The new SE-240 meter concept developed by EPRI in Palo Alto, California, has now been brought to the commercialisation phase. Global Power Products will be the first licensee to introduce the SE-240 to the market.
The SE-240 solid state residential energy meter developed at EPRI (Electric Power Research Institute) over the last three years is remarkable for its versatility, modular open architecture and low cost. It has much in common with Bob Peddie’s CALMS and CALMU development in the UK, and has benefited from decades of field test programmes across the USA from New York to California.
The meter consists of a standardised platform that provides basic energy-use measurements along with plug-in modules that allow the meter to be tailored to the specific needs of a plethora of different service providers and customers.
Following the signing of an international manufacturing and marketing agreement with Global Power Products of Snellville, Georgia, the product is now set to commence full scale commercial production. “This agreement allows us to manufacture an innovative meter that will enable out customers to offer new energy services in deregulated markets,” commented Global Power president Mark Matyac.
Already, there are some 19 communications system modules manufacturers signed up to provide connection with modes of data and services transmission including two way wireless, broadband closed frequency networks, power line carrier, low earth orbiting satellite, hybrid fibre co-axial, telephone modem, cellular telephone, cable television, etc. There is even a CEBus standard, and Home Plug & Play module by Domosys Corporation in Canada. These are listed in Table 1 and more are expected. LAN or WAN integration is readily accommodated.
The open architecture allows the energy provider to select its preference from the widest range of AMR (automatic meter reading) technologies, power quality monitoring, energy management, appliance monitoring and home security functions.
The platform includes a set of ANSI Standard protocols for data transmission so that any vendor can manufacture compatible modules. This should help to avoid obsolescence as functionality and market requirements change.
The main barrier to such metering systems in the past has been the cost of the residential meter. To gain public acceptance it has to be cheaper than the familiar electromechanical meters generally used today as well as offering cost savings, simplified billing and payment, and access to tailored tariffs. The SE-240 is designed to be sold at a comparable cost to other electronic meters on the market while providing improved service capabilities through the incorporation of state-of-the-art electronics.
A hundred prototype SE-240 meters were produced by EPRI and supplied to 47 member utilities for testing and evaluation in addition to the 19 communications module vendors.
Two more meters have also been developed. One is a version of the SE-240 incorporating an internal 200 A disconnect switch, which can give remote disconnect capability. This version can also be integrated into a prepayment system. The other is designed for commercial and industrial applications as an open front end with integral current and voltage sensors, A/D converter and processing. This will be an unsocketed three phase version not dependent on an external current transformer.
EPRI conducted three surveys in the USA to determine what features were required by utilities and their customers. The first of these focussed on the needs of 61 member utilities selected to represent a wide range of sizes and demography. The second two surveys polled consumers from the viewpoint of corporate headquarters, and also of customers in the field to determine which value-added services might be of most interest.
It is a solid state, form “2S” 240 V single phase, three wire, energy meter. The SE-240 can be installed by simply replacing the existing meter, entailing only a short interruption of power supply. It is housed in a compact 170 mm diameter cylindrical casing some 90 mm deep with a 25 mm step to accept the semi-circular plug-in modules (see pictures on page 41). A six digit LCD display indicates energy consumption. Current and voltage are measured to derive energy flow into the household to an accuracy of 0.5 per cent or better in real energy terms.
The meter is fully functioning from 3 to 200 A and has a 12V interface. It is specified to work at temperatures down to -40ºC, but it is still expected to work, if sluggishly, at temperatures down to -50ºC.
Once the SE-240 has been installed, communications modules can be changed without removing the meter or interrupting residential power in any way. The module can be inserted with a dovetail slot locating its alignment to the plugs to the point where it can be secured by fasteners.
The communications protocol is given in Table 2. The specification of the ANSI Data communications, which are based on the ANSI standard C12.18 communications protocol and the information format specified in the ANSI standard C12.19 data tables are available on the SE-240 website (www.se240.com). ANSI C12.19 data tables are embedded in the main processor. This form of EEPROM backup means that all functions should start immediately once power is restored after an outage.
At the same time, the system has been designed to accommodate IEC standards requirements for marketing in Europe and other overseas markets.
Connecting a PC
RS-232 serial communications with the SE-240 meter are via ASA’s RS-232 module, which takes the form of a standardised semicircular plug-in module allowing immediate communication with the ANSI C12.18 data tables.
The RS-232 module contains an RJ-12 connector that not only provides two-way communications via a PC serial communication port, but also buffers the SE-240 pulse output which provides a KYZ contact closure for test meter purposes. Recommended PC software is Table Testbench by Nertec Design, Inc of Livermore, CA.
The RS-232 module allows communications module developers to get immediate hands-on experience with the SE-240 and make themselves familiar with the ANSI communications and standard data tables.
The new load disconnect option for the SE-240 allows for each of the 240V ac lines to be isolated from the load side through the use of a two-pole, 200 A latching type disconnect switch. The low-profile, internally mounted load-disconnect option is available without the need for an external enclosure and little change in the dimensions of the meter casing..
This module will facilitate the incorporation of a prepayment tariff function as well as providing the utility with a hedge against possible loss of revenue. Prepayment trials are expected to take place in the USA next year in spite of the known reluctance of many PUC’s to adopt this approach.
Control of the load disconnect is specifically timed for contact closure at or near zero crossing of the line voltage to maximise switch contact life. As switch performance changes with temperature over its life, the internal control of the switch adapts to the difference by altering the delay time so that zero crossing closure is maintained.
High and low duty versions are available. The low duty is rated to endure up to 8000 operations and the high-duty version is claimed to withstand up to 15 000 operations.
EPRI has signed up two companies in the US for commercialisation and full scale manufacture – Global Power Products, and Power Electronics Co, which is already offering the meters for sale.
Global Power President Mark Matyac is an ex Schlumberger specialist who, like the present EPRI product manager Larry Carmichael, was instrumental in executing the classic remote metering field trials in the USA. The former EPRI product manager Dave Richardson is reportedly heading up the Powell Industries commercialisation.
Global Power Products, formerly North American Power Products, are well known for their existing utility grade metering product lines such as the VT-2 utility grade sub-meter and the MACS (metering and communications system), acquired from Schlumberger Industries in 1995. The MACS system utilises spread spectrum frequency hopping to communicate PLC to a building’s centralised computer. They also own and manufacture the Aptech ARS 200 and ARS 400 Data recorders as well other former Aptech product lines.
The North American market boasts more than 110 million meters with another 3.5 million meters manufactured every year. Free evaluation meters were offered to all of the EPRI Advanced Metering Target utility members in March 1998. These were fitted a communications module of the utility’s choice.
Outside North America trials in Mexico are already being planned, but schedules for introduction to European markets are as yet uncertain. the ANSI protocols have already been mapped to meet IEC standards. In general, the increased profitability for service providers, better load scheduling for utilities, and reduced electricity bills for consumers that such systems promise to provide should find ready markets under most deregulation regimes.