08-11-2012, 03:28 PM
Introduction to Utility Metering Tutorial
Utility Metering.pdf (Size: 1.81 MB / Downloads: 39)
THE MICROCHIP WEB SITE
Microchip provides online support via our web site at www.microchip.com. This web
site is used as a means to make files and information easily available to customers.
Accessible by using your favorite Internet browser, the web site contains the following
information:
• Product Support – Data sheets and errata, application notes and sample
programs, design resources, user’s guides and hardware support documents,
latest software releases and archived software
• General Technical Support – Frequently Asked Questions (FAQs), technical
support requests, online discussion groups, Microchip consultant program
member listing
• Business of Microchip – Product selector and ordering guides, latest Microchip
press releases, listing of seminars and events, listings of Microchip sales offices,
distributors and factory representatives
CUSTOMER SUPPORT
Users of Microchip products can receive assistance through several channels:
• Distributor or Representative
• Local Sales Office
• Field Application Engineer (FAE)
• Technical Support
• Development Systems Information Line
Customers should contact their distributor, representative or field application engineer
(FAE) for support. Local sales offices are also available to help customers. A listing of
sales offices and locations is included in the back of this document.
Technical support is available through the web site at:
Why Electronic Meters?
Electronic meters, as opposed to traditional mechanical and/or electromechanical
solutions in use, offer several additional advantages of interest to the utility market
including:
• Improved reliability and ruggedness
• Improved accuracy
• Support of nonlinear and low-power factor loads
• Ease of calibration
• Anti-tampering protection
• Automated meter reading
• Security
• Advanced billing (time-of-use, prepay, etc.)
Whether it is gas, water, heat or electricity being measured, some or all of these
features apply and are making the electronic meter the solution of choice in both new
(rapidly expanding) and existing (established) markets.
Implementing an electronic meter does not have to be a complex endeavor. This
document will guide you through the many options and solutions available from
Microchip Technology Inc.
Implementing an electronic energy meter, for example, can be as simple and inexpensive
as using a single dedicated energy measurement IC (MCP3905) and a display/counter
of choice. However, more advanced solutions are possible when adopting an 8 or 16-bit
microcontroller (MCU), or even a 16-bit Digital Signal Controller (DSC).
In the following sections we will illustrate in greater detail the advantages listed above.
RELIABILITY AND RUGGEDNESS
The absence of moving parts is a clear advantage of the electronic solution (also
referred to as a “solid state solution”), therefore, electronic meters can be designed to
withstand higher levels of mechanical stress. Meters can be placed outdoors, exposed
to the environment, in conditions and temperatures that can range with the seasons
and, depending on the latitude, can reach extreme values. While it is true that
electronic components are sensitive to temperature variations, these can be easily
taken into account and compensated.
Finally, the high integration (reduced component count) and small packages typical of
modern electronic devices make the electronic solution smaller and more reliable than
the mechanical/electromechanical equivalent.
IMPROVED ACCURACY
Meters are classified in terms of the accuracy of their measurements.
It is typical, for example, for a mechanical energy meter to have an accuracy of better
than 2%. By comparison, an average electronic meter may have an accuracy better
than 0.8%, while some will offer accuracy specifications of 0.5% and even 0.2%,
meeting for example, the more stringent American National Standard (ANSI)
C12.20-2002 specifications.
The accuracy of MCU or DSC-based designs may be specified by software parameters
that can be easily modified as requested by the application (upon installation) while
maintaining a single common hardware platform. This allows for a streamlined production
and economy of scale, both for the utility and meter manufacturer, as the same
product can be deployed in different regions and simply updated in the field.
NONLINEAR LOADS AND LOW-POWER FACTORS (ENERGY METERS)
Most electromechanical energy meters are designed on the simple assumption that
their load (the user application) is of a resistive nature (lights, heating elements and so
on), but today, this is increasingly becoming a wrong assumption. The proportion of
reactive (motors can account for up to 40% of total electricity usage) and nonlinear
loads is constantly growing, posing a burden on the electricity suppliers. Traditional
meters cannot adequately measure the energy consumption of systems with
low-power factors. Electronic meters can easily provide indication of active/reactive
power, and power factor instantaneous values, both alerting the user and providing the
basis for a tariff system that takes power factor into consideration.
EASE OF CALIBRATION
As mentioned above, temperature variations can be easily compensated in electronic
solutions, but similarly, any other mechanical/physical variation can be taken into
account. Electronic meters can use several technologies to provide nonvolatile
memories (EPROMs, EEPROMs, Flash, etc.) to store corrective/calibration
parameters.
These parameters can be periodically reviewed and updated (in the field) as necessary
to ensure that the required accuracy of the meter is maintained over time.