Gemini PLC BS Housing

Split prepayment meter in a BS housing using PLC technology, making installation easy and cost-effective.

Gemini PLC BS Housing The Gemini PLC meter is a compact, single-phase, keypad based, 80 Amp split prepayment meter in a BS 5685 standard housing. Communication between the meter and the customer interface unit is by means of Power Line Carrier (PLC) technology.

Split Metering Functionality

The split prepayment meter consists of two parts, the meter and the customer interface unit.

Communication between the meter and the customer interface unit is by means of Power Line Carrier communication, using existing household wiring. No additional communication wires are required.

The customer interface unit is a compact unit with a user-friendly keypad and display. It may be installed in any convenient location in the consumer's home where there is an electrical socket outlet.

The prepayment meter contains all critical metering, number decryption and load control functionality. It operates independently and is immune to any form of tampering on the customer interface unit.

The meter is usually installed in a secure, locked enclosure, typically a pavement kiosk or pole-mounted equivalent. It is outside the consumer's home to facilitate easy inspection by the utility at any time and to reduce the opportunity of fraud by tampering.

Principle of operation

A key feature of the Gemini PLC split prepayment meter is the ability to use standard household wiring for communication between the customer interface unit and the prepayment meter. This capability enhances retrofitting or replacement of conventional meters with prepayment meters in apartment blocks and housing estates.

The benefits include lower cost of installation as no new cabling needs to be laid, and speed of installation. The keypad or customer interface unit is simply plugged into any existing mains outlet and after a simple commissioning procedure, the unit communicates with the remote meter up to a distance of typically 200 metres.

The maximum communication distance is dependent upon network attenuation and interference.

Customer interface

The customer interface is connected by a power cord to an existing mains outlet in the household. Under normal conditions, when there is sufficient credit in the meter, the customer interface unit operates directly from mains voltage. However, in the event that the meter credit expires and the meter disconnects power to the house, the customer interface unit is fitted with two standard AA Alkaline batteries to allow the customer to re-enter a new credit voucher.

The customer interface has a large backlit display with configurable functionality. The customer or field technician can access meter parameters by entering specific register information using the keypad.

In addition, the customer interface unit has audible low credit warning tones that can be silenced with a keypress.

Meter status and diagnostic indicator

The meter includes a LED status indicator. This allows a technician to view the operational status of the meter without the need for specialised interrogation tools or having to gain access to the consumer's premises. Information such as tamper status, power limiting, commissioned status and credit status are available.

LCD display on the meter

The Gemini PLC meter model is fitted with a large clear display to enable field staff to read the meter parameters in a secure kiosk. This meter can be configured at the time of manufacture to show total kilowatt-hours consumed to date as a running total, while consumers are able to see the remaining kilowatt-hours or units of electricity remaining, on the customer interface unit display in their house.

Interrogation port

More detailed information and programming is achieved via the standard interrogation port at the rear of the meter. This is an optional model at request.

Optical interface

The Gemini PLC meter has an IEC 62056-21 compliant optical communications port. This allows the utility to access a variety of information stored inside the meter using an optical pick-up.

Tamper detection

The split configuration of Gemini PLC meters significantly reduces the risk of tampering, especially considering that the meter is installed in a remote, secure location. The meter is also mechanically sealed against tampering through the use of a factory-sealed screw plugs on the rear of the meter, and a utility-sealed wire seal on the front of the meter. The use of these mechanical seals ensures that there are visible signs of tampering if unauthorised entry is attempted.

In addition, the meter is equipped with a tamper sensor that will automatically disconnect the power to the load in the event of tampering.

The meter also has a feature allowing detection of Significant Reverse Energy. If the line and load wires are swapped during installation, the meter will continue to operate and decrement credit but can be factory programmed to tamper and disconnect the load should Significant Reverse Energy be detected.

Another anti-tamper feature comprises an interlocking mechanical design whereby two halves of the meter cannot be opened until the terminal cover of the meter has been removed. To do so, a utility seal has to be broken

Remote Access

The meter is capable of "upstream" communication to a concentrator at a kiosk, low-voltage distribution transformer or mini sub-station. This feature enables the Gemini PLC2 meter to be remotely accessed by the utility to check the remaining kilowatt-hours, if the meter has been tampered with, total kilowatt-hours used to date, maximum power limit and other useful parameters stored by the prepayment meter.

Communications capability can be implemented in two ways. A concentrator supplied by either Landis+Gyr or a third party, can be fitted into the secure enclosure to provide connectivity via wireless technology to a power utility's back office. As with all split prepayment meters, the Gemini PLC has an optical communications port and each meter in the enclosure is connected to the concentrator via an optical port reading device.

By means of the concentrator and the optical communication port, bi-directional communication is possible. A message can be sent to each meter to request information and prepayment vouchers (purchased by a specific consumer or generated for maintenance purposes) could be sent in a virtual payment process.

Prepayment / Credit feature

Using supplier-specific 20-digit STS prepayment vouchers which are unique to each meter, the Gemini PLC prepayment meter can be converted into a standard credit meter while retaining some of the useful features of a prepayment meter.

These include the anti-tamper facility, maximum power limit and remote customer interface unit for customer convenience. The meter can be switched between credit mode and prepayment mode when necessary, using a 20-digit STS prepayment voucher generated by Landis+Gyr's Suprima prepayment system.

Surge protection

The meter incorporates comprehensive, 30kA lightning surge protection.