Lesson 1: Meter types – Electricity prepayment meters

We will only focus on “traditional” STS type electricity meters. Smart Wallet solutions will be covered in a separate course.

STS type prepayment electricity meters are functionally divided into integrated and split type meters. Of course they are are used both in single phase and three phase applications, the maximum current is usually 80A, although some meters are specified to work up to 100A; these maximum values are usually in order when the solutions are supplied for the use in residential solutions, as the main isolators and circuit breakers (CB) are 63A. More recently higher current three phase prepayment solutions have become available, ranging from 200A to 600A for applications of commercial & Industrial (C&I) users.

Integrated meters are the easiest to inspect and commission, however they are also the easiest to bypass, as they are generally situated inside the residential units. In an attempt to reduce the bypassing of meters, split meters were introduced, here the metering unit is ideally located within a securely locked metering panel outside the residential unit. The only access the tenant has to the meter is via a customer interface unit (CIU). The CIU’s communicate with the meter in various methods: wired, power line carrier (PLC) and/or radio frequency (RF). New constructions lend themselves to wired split solutions (which are substantially cheaper), as the communications cables can be installed during construction.

Unfortunately as the proliferation of suppliers and devices increases the connections standards to the meters also varies. Unlike standard billing meters, where the terminals are specifically designated and arranged in a known pattern (British Standard-BS/IEC), this is not the case for many of the prepayment meter in circulation. Always familiarise yourself with the specific product you are working with.

We will discuss the pairing on meters and CIU’s later – be aware that not all meter/CIU combinations are compatible. Of course this may be obvious e.g. a Landis & Gur CIU will not pair with a Hexing meter, however the situation is more confusing when two similar meters from the same manufacturer cannot use their respective CIU’s interchangeable. This is a key consideration when there is a need to replace faulty CIU’s in the field.