Prior to 1988 Eskom supplied electricity mainly to large customers like mines and municipalities. Although Eskom was at that stage already one of the largest electricity generators in the world, the only had about 120 000 customers and all of them were on billed accounts. In 1988 Eskom developed the “Electricity for All” concept intended to supply electricity directly to the large masses of domestic customers that did not have access to electricity at that stage. Some of the problems to overcome included the following:

• Many customers had to be supported by the smallest number of Eskom personnel. The system therefore had to operate with a low level of management and maintenance. The standard billed system simply required too much day-to day management to process accounts and to maintain connections and disconnections.
• Many of the areas where potential customers reside, had almost no infrastructure. There were no fixed addresses for customers, they did not have permanent jobs or bank accounts and there are no postal services in those areas. All these are requirements for a billed system to operate effectively.
• Many customers are illiterate and do not understand (or have the budget) to pay for fixed charges or bills that arrive only after the electricity has been consumed.

To address these and other problems, Eskom started the development of the basic prepayment system that is currently still in use. This system consisted of:

• Prepayments meters (also called Electricity Dispensers or EDs)
• Vending Machines where the customer can purchase electricity credit (known as Credit Dispensing Units or CDUs)
• Data Concentrators that managed the CDUs and collected the transaction data from the CDUs. (Also called System Master Stations or SMSs).

The first enquiry for electricity dispensers was issued in 1989. This enquiry was based on a very short specification produced by Eskom and every effort was made to keep the price of the electricity dispensers as low as possible. Contracts were issued to two manufacturers based on this specification for an original quantity of 10 000 meters.

The specification document was upgraded to become the more comprehensive NRS009 parts 1, 2 and 3 documents during 1990. Contracts were established with the existing two manufacturers and later increased to include a third, for meters based on the NRS009 specification. The project was also renamed to the “Eskom Electrification Project” at this time and the quantity increased to approximately 10 000 per manufacturer in 1991.

The South African Bureau of Standards produced the first national prepayment meter specification, SABS specification in 1990 with input from the NRS009 specification and it soon replaced the old NRS specification completely. The total contract was steadily increased to a total of 200 000 meters for 1993 and 300 000 per year from 1994 until the year 2000.

During 1993 Eskom also identified the need to standardise the vending systems to be able to sell electricity from one system to meters from various manufacturers. Eskom embarked on a program to standardise the EDs and the vending process and issued an enquiry for a vending system based on a draft specification and for EDs to accompany it. Soon thereafter development was started in conjunction with Conlog to design and build the new Common Vending System (CVS).

To enable the new vending system to transfer credit to all types of meters it was also necessary to develop a standard transfer medium and protocol to the meters. This was also part of the project and thus the “Standard Transfer Specification” STS was born. This Common Vending System and the STS meters form the basis of the prepayment system as it exists today in Eskom.

The specifications have been further improved over the years and are today adopted as the standard by electricity utilities in South Africa. South Africa is now seen as a world leader in prepayment technology and many other countries have adopted our standards as well.

The SANS1524 specification from the SABS was used as a major source during the development of the international IEC specification for payment meters. Further more, the STS standard has since been adopted by the IEC as well, and the STS Association is currently working on the development of STS2

To Prepayment Operation