The commercial activities of informal street vendors in many of the world’s cities causes economic losses in the form of energy theft. In consequence power utilities are looking for technical solutions that correct these financial losses, and that offer a safe and effective electrical installation. They also hope to motivate a culture of responsible use of energy among users.
HOW TO AVOID LOSSES
CIDEC, Condumex’s research and development centre, designed and manufactured equipment that satisfies these requirements. The result is a cabinet which functions as a central point for distribution of energy on the street. It is connected to a 3-phase system from the power utility’s transfomer. Each phase is connected to eight 15 A electric connections rated at 127Vrms, so the equipment has 24 electric connections in total located at its lateral doors. Each connection is dedicated to one user, who generally has his own shop on the street.
The consumption of energy is measured by each phase through the use of 3 digital single-phase meters, also designed and manufactured by Condumex. The cabinet controls the supply of energy in all the 24 electric contacts. The control depends on the amount of credit in kWh units, which is downloaded to the system by means of a disposable memory card, similar to public telephone cards. When the credit is greater than 0 Wh, the cabinet still delivers energy. The credit is decremented every Wh, and when it reaches zero the cabinet’s internal electronic control commands the meter to disconnect its phase.
THE PILOT PROGRAMME
The equipment was installed in one of the most problematic zones – a street market located in the southern part of Mexico City. The first step consisted of burying all the electric cabling underground so as to avoid illegal connections in the future, given that the merchants can only obtain electricity through the cabinet. The street market can have some 300 different users in a typical day, so a total of 17 cabinets were installed in strategic locations.
After the installation was completed an intensive communication programme took place between all users to encourage adoption of the system. The service was offered free of charge for the first three months, and once the merchants had seen the functionality and safety of the cabinet for themselves they were persuaded to sign a service contract. This happened in July 2003.
Since then the system has been running successfully. The merchants that are connected to each cabinet co-operate with one another to pay the cost of each card. The cards are offered in money value, and the utility makes the conversion to kWh units based on the tariff at the time the sale is made.
LOOKING TO THE FUTURE
Condumex is designing two new versions of the cabinets. The first is still based on using 3 single-phase 1S class digital meters, but with some improvements. The cabinets have been made more robust to protect against vandalism, and there are more electronic functionalities like the collection of data via RF, as well as an improvement in the security of the transactions using a new smart card. The second model incorporates these improvements, but uses a 3 phase 16S class digital meter.
The consumption of electricity decreased by about 50% at the street markets where the cabinets were installed
These cabinets could be used throughout Mexico. Whether or not this happens depends mainly on strategic decisions made by the public power utilities, rather than on technical issues related to the equipment.