[Edson da Costa Bortoni][March, 14 2007]Modern centralized metering systems are equipped with features that increase their potential applications – not only in reducing commercial losses but also in adding value to customer service.
Each year in Brazil the electric utilities lose billions of dollars as a result of commercial losses, which account for about 4.5% of the annual electric energy market. These losses are divided among the several companies in the sector, with percentages differing from region to region and even between utilities in the same region. Losses can vary from 1% up to 25% of annual revenues.
Commercial losses, which are associated with meter tampering, theft using illegal connections and errors in reading and measuring, have a significant impact in the tariff revision process, imposing the need for a gradual reduction of the loss rate over a certain period of time. As a result, electric utilities are forced to look for alternatives which will help reduce commercial losses, while at the same time investing in systems which will optimize the commercial management process.
In this respect, centralized metering systems (CMS) have become a very attractive alternative, mainly because of the use of recent technological improvements which offer features that effectively add value to the metering service, as well as reducing theft.
The use of bidirectional communication systems offers an array of opportunities, limited only by the imagination of those who use them. To have a direct communication channel with the end consumer and to be able to follow his consumption habits in detail is in itself a critical source of information that provides the opportunity to offer tailor-made services. These benefits are desirable in any market intelligence analysis and are readily available to those who have access to modern centralized metering systems.
Furthermore, a proportionate reduction in the marginal cost of investment will be obtained by increasing the number of features and alternative applications, considering that the cost of installing the meter will be evenly spread among the additional features. These benefits are in addition to accurate and timely consumption measurement. Some of the features that have been incorporated into centralized metering systems are presented below.
Disconnect and reconnect: This feature allows a consumer that is in default to be disconnected or reconnected automatically by operating a remote relay. This is a safe and cost-effective alternative to dispatching service personnel to the site.
Figure 1 – Application of the CMS in high theft areas
Time-of-Use Billing Options: Because these are electronic meters which are capable of linking consumption to a certain hour of the day and season of the year, the CMS allows for the implementation of hourly tariff mechanisms for low voltage residential and commercial customers.
Demand Side Management: The benefits of demand side management (DSM) are widely recognized, but because of technological barriers its implementation over the past 20 years has been slow. Today, CMS’s that utilize the existing utility infrastructure can provide DSM services to more customers without any additional investment. The CMS not only offers control of customer demand at peak hours or by region, but also offers economic benefits to those same customers.
Prepayment: With a CMS it is possible to install prepayment and load-limiting systems which use a combination of metering and remote disconnect resources. With a prepayment system, the amount of kWh purchased is transmitted to the meter and stored in its memory. The meter will count down, showing how much energy is available before reaching zero and disconnecting. Utility companies can adjust such systems to offer warnings in advance of shut-off to remind customers of their approaching limits. Load limiting systems function in a similar manner, whereby the utility company can remotely set a limit to the power delivered to each customer.
Reading Utility Meters: Pulses from water, gas and steam meters can also be monitored by electronic meters which provide additional benefits once this information has been transferred to the respective utilities. To that end it is necessary that the meters provide pulses relative to consumption. Conventional mechanical meters generally do not have that capability. Nevertheless, there are now solutions available that allow for pulses to be generated by conventional meters.
Meter Multi-functionality: In addition to the features described above, these systems allow the expansion of an array of measuring features which are not limited to the measurement of active energy. New features have been added such as capacity measurement, real, reactive and apparent energy in each phase or multiple phase, load profile, power factor, tension and current in each phase, V²h and A²h (useful when estimating technical losses), harmonic content (individually or THD) and evaluation of quality of supply.
APPLICATION IN AREAS WITH HIGH THEFT RATIOS
Although centralized metering is applicable in almost any segment of the electric energy market, including residential multi-family properties, commercial buildings and in remote location or rural areas, the use of these systems in areas that experience considerable energy theft is perhaps the main motivation for the application of this technology as it is known today. Given the significant amount of losses incurred by the utilities, any investment made in this area will be justified from an economic point of view.
Figure 2 – Example of a CMS installation
As a general rule, the installation philosophy of the CMS is dictated by the schematic as shown in Figure 1. In this case, the aerial cables connect Quadlogic’s Energy Guard to the individual consumers. The information gathered will travel to a concentrating unit via PLC or other technology and will be stored for collection later on by the utility.
In addition to the installation of this equipment away from customer homes, several security measures have been implemented to make it harder to tamper with the meters, thus further reducing the possibility of fraud and illegal connections. Among these measures the following stand out:
Tamper Detection: Devices sensitive to contact and light are installed inside the meter box. As a result, all customers connected to that meter will be automatically disconnected as soon as unauthorized opening of the box is detected.
Difficulty of Access: In order to make access more difficult and to intimidate potential violators, the meter box is installed on the utility pole above the medium tension lines.
Reverse Voltage Detection: In some cases a utility company can disconnect power to an individual customer, but that customer is still able to obtain power via an alternative clandestine feed. A solution to prevent this from happening is to feed neighboring consumer units with voltage in separate phases. In this situation, if someone attempts to install an illegal connection, a phase-to-phase voltage will appear in the terminals of the relay. By monitoring the voltage across the relay it is possible to detect the fraud, which will result in both customers being disconnected.
Losses in the Feeder: The verification of losses in the feeder, including both technical and commercial losses, can be better accomplished if the total energy supplied on the low voltage side of the distribution transformers is measured. By doing this, it is possible to determine the difference between the total energy supplied and the energy billed during a specific period of time. A significant difference in the net value greater than the technical losses estimated for that feeder and the part related to public lighting may be a strong indication that there is some kind of fraud in that area.
In conclusion, reductions in costs and commercial losses were the initial motivation for the adoption of centralized metering systems, because almost all investments made in this area have been easy to justify economically. Nevertheless, the use of two-way communication systems has brought about an array of opportunities for cost recovery, labor savings and improved customer service.
The increased availability of additional features has resulted in the reduction of the unauthorized use of energy. Likewise, the expansion in the number of alternative applications for the systems has also allowed for a reduction in marginal installation costs for this equipment, with a corresponding increase in the return on investment.