Separate consumer interface increases flexibility and security

According to RA Peddie, “History shows that when significant shifts take place in society, few people appreciate the nature and long term significance of the change, even though many are dimly aware that something is changing.” The traditional metering market has been slow to adopt new products using all-electronic, all-digital platforms. Utilities have been concerned that the latest technologies are chasing a hapless buyer, who may be convinced that he has found the answer to all his metering problems.

Electronics and computer technology also seem to be unlikely partners in an analogue world where voltages are usually abbreviated with at least a ‘k’ as a precursor to the ‘V’. However, the electricity supply industry (ESI) is rapidly embracing modern technology in its drive to improve efficiencies of operation, while giving an improved level of customer service.

This paper investigates the benefits of the split-meter concept, and the technologies that might be used in the implementation of split-metering. 

Metering Seen in a New Light

For the first three-quarters of this century, conventional electro-mechanical voltmeters, ammeters, and watt-hour meters dominated the monitoring of electrical power and energy. These meters perform their task satisfactorily, operate reliably, and have remained virtually unchanged for many years. 

However, there is a growing niche of applications where a more advanced device has advantages. This niche has fostered the development of the electronic meter. These electronic, microprocessor-based digital meters are now widely available. They have become affordable and their reliability has increased substantially by using automated manufacturing processes. The meter specifications have also been tightened up as the effects of surges, lightning strikes and environmental hazards have been addressed.

The familiar Ferraris meter is often mounted in a position for easy access by the meter reader. However, it is often not easy for the customer to access and read this meter, as it is usually mounted outside the premises in a weatherproofed area. Reading the meter dials to obtain the kilowatt-hour value is somewhat confusing to the average customer. The concept of the kilowatt-hour also seems to have little bearing on daily life, because of the term’s infrequent use.

The Application of Prepayment Systems

“If you can’t meter it, you can’t manage it”

This is the Two M rule introduced by WL Stebbins in his paper on Energy Monitoring and Metering Systems. Encouraging the customer to manage his or her own energy consumption is an effective way to implement a form of demand side management (DSM). Customer DSM can be implemented using a prepayment meter installed on the customer’s premises.

There needs to be a suitable method of managing the system. Controls are necessary to ensure that when the novelty of the prepayment product wears off, it does not lead to abuse of the product’s safety and security features for personal gain.

As reported in Metering International in 1996, Electricité de France (EdF) conducted a survey of 1500 customers to establish the overall response to prepayment metering. The main statistics from the study show that:

  • 94% were satisfied and had experienced savings
  • 89% were better equipped to monitor their electricity consumption, resulting in better budgeting
  • 50% had changed their electricity consumption habits to support saving
  • 85% viewed it as a user friendly system.

What makes the electricity prepayment system so attractive is that for the first time the customer can see electricity as a product. With the conventional billing system, and in particular where the customer is familiar with the use of electricity, he has begun to believe that electricity is a right and that the account he gets at the end of each month is an infringement of this right. The customer is probably suspicious of the accuracy of the meter reading, and he may not understand how the account was derived.

Fig 1: Typical Meter Liquid Crystal Display

With prepayment metering, electricity can now be purchased like any other product – that is, when it is desired, at a place of convenience and within budget. By placing the customer interface inside the consumer’s home (preferably in the kitchen) the consumer interacts with the measurement and control unit that measures energy consumption and stores available credit. The customer is made aware that he is consuming a product, in this case electrical energy.

Prepayment metering has the added advantage that it puts the customer in charge of his own usage and budgeting of electricity.

Prepayment Meter Design Drivers

“…very little has been done since the introduction of the microprocessor to provide the end user …. with useful information”

was a comment made by PM Kettless in his article on Metering for the Domestic Customer. The customer wants to pay as little as possible for electricity and he does not want to be surprised by unexpected billed amounts.

Changes in electricity metering technology have led to a number of prepayment products that automatically disconnect a customer’s supply if pre-purchased electricity credits are exhausted. It appears that meter manufacturers are the natural drivers in the process of product development because of their leading role in this rapidly evolving technology.

One of the important design drivers of the prepayment meter is the user interface. The user interacts with this part of the meter, either to enter credit tokens or to read information displayed. The interface can also provide diagnostic information to service staff. The displays can be either simple LED (light emitting diode) or complex alphanumeric LCD (liquid crystal display) types with icons (see Figure 1 for a typical example). The display conveys status and operational information to the customer, which can be used to manage energy consumption more effectively.

Value Added Products

Anyone using energy regards it as an input expense. Customers are more concerned with the services provided by electricity such as heat, light and appliance operation, than they are with the number of kilowatt-hours they purchase. However, the customer is usually concerned by the cost of the kilowatt-hours at the time of the purchase of the credit or the payment of a bill.

There is a growing need for new ‘value added’ products and services from the utility service provider. The utility has a selection of tariffs to suit the various customer consumption profiles. Properly designed and implemented conservation and load management programmes can increase customer value, forestall loss of sales and provide ‘hedges’ against uncertain load growth. Potential DSM technologies must be evaluated against utility avoided costs to determine their cost effectiveness.

The customer may also be offered enhancements to the metering equipment – in particular the customer interface to the service provided. These sophisticated meters (or rather sophisticated devices, as metering is only one of the functions performed by modern electronic products) provide a selection of statistical data – remaining credit, days of usage, average usage and peak demand.

Split View

Some of the technological developments have been applied in an attempt to eliminate fraud. One such development is the separation of the customer or user interface unit (UIU) from the measurement and control unit (MCU) of a prepayment electricity dispenser (see Figure 2). In this case, the MCU is placed in a secure environment where it is difficult, for the customer to gain access to it to perpetrate fraud. This prevents the customer from bypassing the MCU or causing damage that may allow the partial measurement of energy consumption, or the free issue of energy credit units.

In an exercise to address the issue of the theft of electricity, the South African utility Durban Metro Electricity, together with the regional planning divisions and suppliers of cables and electricity prepayment meters, has successfully implemented a split-metering project. The split-meter comprises a UIU located in the customer’s dwelling, with the MCU being located remotely from the dwelling, usually at the top of the pole that supports the low voltage supply cables.

Multiple MCUs can be mounted into a single pole-top housing from which multiple dwellings can be reticulated (see Figure 3). The remote location of the MCU prevents tampering, as the customer can no longer gain access to the meter terminals to bypass the supply and load side terminals.

The Need for Split Metering

Split-metering technology has provided a useful solution to some of the problems experienced by utilities in managing non-technical losses.

Split Meter Interconnection

The decision as to which metering technology to apply is governed by the social climate. Some of the most sophisticated tokenless prepayment revenue management systems have been introduced to try to combat blatant fraud. However, strong social attitudes in some areas have made a mockery of attempts to introduce the latest technological solutions to metering energy consumed.

Tampering with prepayment meters is on the increase in some areas, given that the early generation meters are mounted inside the customer’s premises, and that meter readers are not required to visit the installation as they would for conventional meters.

Access to a customer’s premises to check on a meter has highlighted serious logistical problems. In some areas, a lack of structured addresses has hampered attempts to audit installations and to control fraud. Many utilities are mandated to investigate and check every meter (prepayment or otherwise) within a given period to minimise non-technical losses.

Customers are becoming more aware of their energy needs and finite budgets. They are looking towards more sophisticated information feedback products that enable them to minimise their monthly allocation for electrical energy.

In Conclusion

The split-meter communication platforms can be combined to control the utilisation of the often scarce energy resource through tokenless vending. All the usual benefits of the prepayment method can be retained, except that the purchased credit token can be delivered automatically to the MCU without customer intervention. The customer will then use the UIU as an information interface so that he is able to better manage his energy consumption.

This article is an edited version of a paper presented at the Mates ’99 Conference, Birmingham, UK.