Modem technology reduces remote reading costs22 January 1998
Meter reading is an issue in the supply and billing of any utility and there are several methods available for this, varying in degrees of complexity. Remote reading of electricity meters via a telephone line is increasing in popularity because of the low installation cost and high reliability of the equipment. In addition, the latest in low power electronic circuitry means that modems are now available which can be powered directly from the telephone line.
In the electricity sector, particularly in a liberalized market, there is a fundamental need to try to balance supply against demand in order to maintain a competitive position. A utility's ability to have rapid access to the usage data of their major customers opens the way towards innovative tariff structures with benefits for both users and suppliers.
In recent years, recovering this data via a modem and telephone line has proven to be both convenient and cost effective. In the UK, several Regional Electricity Companies (RECs) have enjoyed the benefits of line powered modems for meter reading in both customers' premises and substations.
The substantial numbers used confirm that they are easy to install and operate and have demonstrated long term reliability, an important factor in a cost sensitive market. The information can also be made available to the customer as a service to help them with their own energy efficiency programmes.
There are three principal ways of collecting data from utility meters. The most basic, and probably still the most common, is sending a meter reader with a pen and paper, or hand-held terminal. Although this may have the smallest initial financial outlay, the disadvantages are obvious. It is time consuming, open to human error and results in time-wasting if access to the meter is not possible at the time of calling.
Smart cards and prepayment schemes are a widely used alternative, but can be unpopular as it is the consumer's responsibility to ensure that they always have enough credit remaining.
Remote data collection is the third option. Although this requires a greater initial capital outlay, it results in a far more reliable and automated method of data collection and the payback period is relatively short. There are three main types of remote data collection: radio based; power line carrier; and telephone based. All have a part to play and will be used in ever increasing numbers over the next few years. To decide on the most appropriate system, financial and geographical considerations need to be taken into account.
Radio based systems tend to be appropriate where there is a high concentration of meters in a small geographical area. Readings from each meter are stored in local collection points known as concentrators. These can either poll the meters at regular intervals or receive information transmitted at random intervals by the meters. The stored data is sent to the central data processing centre as often as required either by using a more powerful radio link or by a fixed telephone line.
In the USA, a popular type of system uses "drive-by radio collection" rather than fixed concentrators. Here, a van is driven around the area polling the meters to recover and store the data. The main drawbacks of radio based systems are that they can be prone to interference and shielding by buildings or traffic, they can be disturbed by adverse weather conditions and have limited range.
Power line carrier methods convert the information from the meter into a signal that is superimposed onto the power carrying mains cable. This uses the existing electricity infrastructure so installation and maintenance costs are minimized. The main disadvantage of this method is that it can be difficult to get the information back through the high voltage distribution network beyond the local substation. Therefore most systems rely on concentrators located in substations and collect the data from these by telephone links. Because of this drawback, the system is also best suited to areas of high meter concentration.
However, there is a potential conflict of interest in a liberalized market where several suppliers may be servicing customers through the same substation but using data collection systems from different manufacturers.
Telephone based meter reading has many advantages. The telephone network is a proven infrastructure and is in widespread use. Installation is relatively easy, and it does not matter if the meters are spread over a wide area. The only prerequisite is that there is a telephone nearby.
With many modems used for telephone meter reading, a power supply – either mains or battery – is also necessary. Mains power cables, fuses, switched outlets and so on are extremely expensive to provide if not already in place, and batteries require replacing. However, the latest in low power electronic circuitry means that modems are now available which can be powered directly from the telephone line.
Both radio based and power line carrier systems are best suited to areas of high meter density. These would normally be domestic or small commercial customers whose premises would be equipped with the most simple type of meter. To take advantage of remote meter reading, add-on units to the meters would be needed, or the meters would need to be changed to types including communications facilities. This would also apply to larger industrial customers. These changes to the metering equipment make initial installation costs high except for new installations or as part of a routine meter replacement programme.
On the other hand, telephone based systems are generally best suited to larger customers who may already have sophisticated metering equipment. Many of these will already have a communications capability designed for either reprogramming or for downloading readings into a hand-held terminal. Modems now exist that could be connected directly to these meters, saving the costs of replacement and minimizing maintenance costs.
Line powered technology
Line powering overcomes the traditional problem of finding a suitable power supply. Even electrical metering applications rarely have a mains voltage outlet near the meter. The need for power cables to be installed, which can often be expensive in typical meter locations, is avoided and the ongoing cost of batteries is eliminated.
It also overcomes some of the usual complaints with remote data collection by modem such as loss of the modem configuration setting or "locking up" due to loss of power. The elimination of one of the possible causes of system failure makes line powered meter reading inherently more reliable than using a conventionally powered modem. The development of the technology to its present level of sophistication means that telephone based meter reading is now a reality for gas and water metering applications as well as electricity meter reading.
The modems used in utility data collection are very different from the types used for computers, the main difference being their speed. In electricity metering applications, it is desirable to download the data in the shortest possible time. However, it is a misconception that a faster modem will result in the quickest download time and hence the shortest telephone connection.
The time taken for a modem to connect and become active increases with increasing speed. This means that for smaller quantities of data, a slower modem would offer the shortest telephone connection. The extremely short billing delay with a modem such as a V.21 (300 baud) means that for applications requiring the transfer of less than 120 bytes at a time this speed actually results in the shortest call time.
For applications requiring the transmission of between 120 and 520 bytes, the higher speed of a V22 (1200 baud) modem outweighs the 3.5 s connection time. Faster modems such as the V32 standard (9600 baud) do not offer any time saving until the quantity of data exceeds around 1.6 kB. As most electricity metering applications require the transfer of relatively small quantities of information, V21 or V22 modems are generally used.
Modems for such applications are constructed to industrial specifications rather than computer specifications. Many companies specialising in these types of modems, such as Jekyll Electronic Technology, produce a large variety of modems for industrial and utility applications and is able to customize modems.
Perhaps the principle disadvantage of telephone data collection is the necessity for a separate telephone line. The installation and running costs of this can often deter use of telephone data collection. However, modems have now been developed which share a phone line with an existing voice telephony line, saving installation and rental costs.
Such modems are ideal for utility meter reading applications where remote data collection over the telephone network is desirable but additional telephone lines cannot be justified. Jekyll's "PhantoModem" combines a line powered modem with the ability to share a telephone line.
The innovative technology uses the information provided by the "Caller Display" service to check the origin of all incoming calls and only responds when appropriate. In use, the incoming calls are checked against a list of numbers stored within the modem. Telemetry calls are thus identified and the modem answers before the parallel telephone rings providing a true "no ring call" facility. Once the modem has answered, it behaves like a conventional modem and no special additional communications software is needed.
If the incoming call is not identified as a telemetry call, the modem returns to its slumber mode and the parallel telephone rings as normal. Ordinary use of the telephone is not inhibited by the modem and the lifting of a parallel telephone whilst the modem is on line is detected and the modem shuts down to make the line available. The telemetry call can be re-established later.
These modems can also enable the user to access the meter if agreed by the supplier. This is particularly useful for energy management purposes in large facilities. The electricity company can offer this as an additional service and a benefit to both their customer and themselves. By programming the modem, they can control who can collect data from the meter, so if bills are unpaid, access can be denied.
The latest generation of electricity meters can also collect information from water and gas meters. Connection of a modem to such a meter means that data for all utilities could be collected over the telephone line with a single modem. However, a device is also available which can connect to several different meters and transmit all the data down the same telephone line. For many installations, this means that without any modification of the meters, a single modem together with the "select" unit can be used to read several meters and transmit the information down a telephone line, which it may be sharing with a normal telephone.
Some of the latest line powered modem products combine multiple utility meter reading facilities with line powering and even line sharing. This means that a single unit can collect information from several utility meters and transmit the information down a shared line to the utility providers. Customers can also dial up the unit to check on their power consumption.
Remote meter reading by telephone has already proved itself both technologically and financially. The adaptable nature of the technology and the ongoing research and development programmes in this area mean that whatever future developments in meter technology occur, data collection by telephone is set to remain a popular option.