Revolutionary Smart-meter Software from HCC Embedded Reduces Hardware Cost and Development Time

Smart Meter File System uses structured database approach to maximize flash life and reduce power consumption 

 

Nürnberg, Germany 21 Feb 2014 – HCC Embedded today announced that it has developed an advanced file system, custom designed for the needs of smart-energy and smart-meter applications. HCC’s approach maximizes the life of flash, significantly reduces power consumption, and provides a deterministic ‘emergency write’ function, which reduces cost by allowing the on-board capacitor to be as small as possible. Collectively the file-system features can result in savings of many ‘cents’ for each meter, a highly significant cost reduction in high volume manufacture.

        The software is developed using high qualitydevelopment methodology and is rigorously compliant with the MISRA C:2004 coding standard.  The HCC‘Smart-meter File System™’ (SMFS™) requires less than 15kB program memory and less than 1.5kB of RAM on most 32-bit MCUs.

        Metering applications work with well-defined records that are more suited to a database approach. General-purpose file systems do not have any cyclic buffer logic for storing records and this adds complexity to applications. SMFS uses a structured database to reduce complexity of the application and improve the performance of the system in almost every way—speed, power consumption, and flash life.

Key features:

• Fail-safe data storage for guaranteed system recovery.
• Persistent data storage for 15 years or more.
• Minimal power consumption to preserve battery life.
• Minimum number of flash operations to preserve both the flash and the battery.
• Deterministic behavior in the event of unexpected reset.

        SMFS is available immediately for a range of 16 and 32-bit MCUs and SOCs, and thanks to HCC’s Advanced Embedded Framework, can easily integrate with any RTOS, toolchain or development board. 

Visit http://www.hcc-embedded.com/ for more information.

About HCC Embedded

        HCC Embedded is a leading supplier of advanced embedded middleware for storage and communication. Implementation is based on a strong process that produces robust, target independent software modules. The company offers an extensive family of products including fail-safe file systems, IPv4 & IPv6, USB software for host and device, flash translation layers, and eTaskSync verifiable scheduler.  Thanks to the Advanced Embedded Framework, HCC software will run seamlessly in most embedded environments regardless of OS, toolchain, or hardware.  All HCC Embedded products are distributed in full source form.

T & D - 33) Arrangements of LV Utility Distribution Networks (2)

Arrangements of LV Utility Distribution Networks

Continued from the previous part: Arrangements of LV Utility Distribution Networks (1)

The consumer-service connection

In the past, an underground cable service or the wall-mounted insulated conductors from an overhead line service, invariably terminated inside the consumer’s premises, where the cable-end sealing box, the utility fuses (inaccessible to the consumer) and meters were installed.

A more recent trend is (as far as possible) to locate these service components in a weatherproof housing outside the building.

Fig. C4: Widely-used American and European-type systems

Note: At primary voltages greater than 72.5 kV in bulk-supply substations, it is common practice in some European countries to use an earthed-star primary winding and a delta secondary winding. The neutral point on the secondary side is then provided by a zigzag earthing reactor,the star point of which is connected to earth through a resistor. 

Frequently, the earthing reactor has a secondary winding to provide LV3-phase supplies for the substation. It is then referred to as an “earthing transformer”.

A MCCB  - moulded case circuit breaker which incorporates a sensitive residual-current earth-fault protective feature is mandatory at the origin of any LV installation forming part of aTT earthing system.

The utility/consumer interface is often at the outgoing terminals of the meter(s) or, in some cases, at the outgoing terminals of the installation main circuit-breaker (depending on local practices) to which connection is made by utility staff, following a satisfactory test and inspection of the installation.

A typical arrangement is shown in Figure C5.

Fig. C5: Typical service arrangement for TT-earthed systems

A further reason for this MCCB is that the consumer cannot exceed his (contractual) declared maximum load, since the overload trip setting, which is sealed by the supply authority, will cut off supply above the declared value. Closing and tripping of the MCCB is freely available to the consumer, so that if the MCCB is inadvertently tripped on overload, or due to an appliance fault, supplies can be quickly restored following correction of the anomaly.

In view of the inconvenience to both the meter reader and consumer, the location of meters is nowadays generally outside the premises, either:

• In a free-standing pillar-type housing as shown in Figures C6 and C7
• In a space inside a building, but with cable termination and supply authority’s fuses located in a flush-mounted weatherproof cabinet accessible from the public way, as shown in Figure C8
• For private residential consumers, the equipment shown in the cabinet in.

Fig. C6 : Typical rural-type installation

In this kind of installation it is often necessary to place the main installation circuit-breaker some distance from the point of utilization, e.g. saw-mills, pumping stations,  etc.

Fig. C7: Semi-urban installations (shopping precincts, etc.)

The main installation CB is located in the consumer’s premises in cases where it is  set to trip if the declared kVA load demand is exceeded.

Fig. C8: Town centre installations

The service cable terminates in a flushmounted wall cabinet which contains the  isolating fuse links, accessible from the public way. This method is preferred for  esthetic reasons, when the consumer can provide a suitable metering and main-switch location.

Fig. C9: Typical LV service arrangement for residential consumers

Figure C5 is installed in a weatherproof cabinet mounted vertically on a metal frame in the front garden, or flush mounted in the boundary wall, and accessible to authorized personnel from the pavement.

Figure C9 shows the general arrangement, in which removable fuse links provide the means of isolation.

In the field of electronic metering, techniques have developed which make their use attractive by utilities either for electricity metering and for billing purposes, the liberalisation of the electricity market having increased the needs for more data collection to be returned from the meters.

For example electronic metering can also help utilities to understand their customers’ consumption profiles.

In the same way, they will be useful for more and more power line communication and radio-frequency applications as well.

In this area, prepayment systems are also more and more employed when economically justified. They are based on the fact that for instance consumers having made their payment at vending stations, generate tokens to pass the information concerning this payment on to the meters. For these systems the key issues are security and inter-operability which seem to have been addressed successfully now.

The attractiveness of these systems is due to the fact they not only replace the meters but also the billing systems, the reading of meters and the administration of the revenue collection.

What Do You Need To Know When Connecting Solar Electric System to the Utility Grid

n the past, most homes with solar electric systems were not connected to the local utility grid. It made sense to install solar electric systems in areas without easy assess to the power grid, where the option of extending a power line from the grid might cost tens of thousands of dollars.

In recent years, however, the number of solar-powered homes connected to the local utility grid has increased dramatically. These “grid-connected” buildings have solar electric panels or “modules” that provide some or even most of their power, while still being connected to the local utility. Owners of grid-connected homes can choose to supply a portion of their energy with solar energy, using the utility for power during the night or on cloudy days. Because of the up-front costs of installing a solar electric system, many of these homeowners initially install systems that meet about one quarter to one-half of their energy use.

Solar electric systems sometimes produce more electricity than your home needs. This extra electricity is either stored in batteries or fed into the utility grid. Homeowners can be given credit by their local power companies for the electricity produced at their homes through “net metering” programs.

Net metering

Simple scheme of connecting solar electric system to the grid

Grid-connected systems generally use a billing process called “net metering” or “net billing”. In this process, any energy generated by the solar modules that your home does not use immediately is sent to the utility grid.

However, when the solar electric system is producing less power than is needed, you can draw additional power from the grid. If your system is connected to the grid through a single electric meter, your meter can actually run backwards as you contribute excess energy to the utility.

The excess electricity is being credited to you at the same retail rate as the electricity you use from the utility. Your utility may require the use of two meters—one that meters your consumption of energy from the grid and the other that meters your contribution to the grid. In this case, your solar-generated excess energy could be credited at the retail rate or possibly at a lower wholesale rate, depending on the utility.

In addition, some utilities bill their customers according to a “time-of-use” rate system. Under this system, customers are billed at a higher rate during certain times of the day, such as during the sunniest daytime hours of summer when air conditioners are working at their peak. If this is the case with your utility, you may be able to “trade” your excess energy to the utility at these same rates.

You can therefore benefit from the fact that your solar electric modules produce the most power during those sunny summer days. When you need power from the utility during the off-peak periods, such as in the evening, the rate is usually lower. If you choose to have a grid-connected solar electric system, and your system produces enough energy in any given month so that you do not have to draw from the grid, you may still receive a small monthly bill. This is because many utilities charge monthly fees for meter reading. Again, check with your local utility.

Connecting to the grid

One of the most important steps in purchasing a grid-connected solar electric system is choosing a provider with experience. A good provider will also have a properly licensed electrical contractor, have enough years of experience to have demonstrated an ability to work with customers, and be able to compete effectively with other firms.

A good provider should be familiar with your local utility’s regulations on interconnection requirements. If your provider is not familiar with these requirements, check with your local utility, state energy office, or state or local Public Utility Commission for details.

Your solar electric provider should supply you with everything you need to run your system, including a specific type of inverter for grid-connected systems, batteries (if you want backup power), and a special electric meter. As mentioned already, some utilities require you to have one electric meter that runs both forward and backward. Other utilities require two separate meters: one for incoming power you receive, and one for power you generate that goes back into the system. These meters are sometimes paid for by the utility, but may be part of your provider’s price for the system.

As part of the installation of your solar electric system, you will need to sign an interconnection agreement with the utility company. Your solar electric provider may be able to handle the negotiations and paperwork with the utility, but this contractual agreement is between you and your local utility. Be sure to read the fine print in this agreement, which may differ considerably from one utility to another. It could range from a short one-page statement to a lengthy booklet. In either case, the fine print may contain references to liability issues that you will want to fully understand before signing the contract.

Also, be sure to speak with your homeowner’s insurance provider, because the solar electric system itself will need to be added to your policy. In many cases, you may have to add a rider to your policy for the grid connected system.