Mains signalling systems

Details Mains signalling systems Mains signalling systems

1997-05-16

1999-06-15

Horabik, Michael

Communications: electrical

Continuously variable indicating

With meter reading

34031001, 34082518, G08B 2300

Patent

active

059126337

DESCRIPTION:

BRIEF SUMMARY
The present invention relates primarily to mains signalling systems, though it is also applicable to other systems having similar characteristics. (The term "main" applies primarily to the final consumer voltage portions of an electricity supply network, though the signalling can also extend over the higher voltage distribution parts of the network.) Such signalling is termed mains, mainsborne, or power line carrier (PLC) signalling.


Remote Metering

A major application of mains signalling is remote meter reading, operated by electricity generating and distribution companies (electricity utilities). The term "remote meter reading" refers to what is normally the major function of such systems, but they may also be concerned more generally with load and system control. Also, while they will usually be concerned primarily with electricity meters, gas and other meters can in principle be coupled to the mains for this purpose (preferably through electricity meters).
A typical simple remote meter reading system will have a central station or local controller (which can conveniently be located at a distribution transformer) which communicates over the mains with the meters (meter stations) of the various premises (largely household or domestic and small commercial) on the mains. Such systems have two major problems: noise and attenuation.
Mains noise arises from loads being switched on and off and the inherent characteristics of certain types of loads. The noise problem can generally be overcome by a variety of known techniques, such as error detection and correction techniques, requiring acknowledgement of reception, and repetition of lost messages. (Some of these techniques also deal with problems of message collision.)
Dissipation or attenuation at the preferred signal frequencies is significant; it is dependent on the particular operating conditions of the mains network and varies according for example to the loading of the network. The attenuation will often be irregular; there may for example be potential "dead spots", due eg to signal reflections, close to the signal source while communication to more distant locations is still reasonably reliable.
A system which largely overcomes these problems has been proposed in our earlier patent application Ser. No. PCT/GB94/01391, WO 95/01030. In that system, which we will for convenience call the "standard system", substantially all meters have a repeater function. The present system is a broadly a development of or improvement on that system.
The topology of the standard system will normally be branched. That is, the central station will normally be able to communicate directly with several meters, each of those will normally be able to communicate with several further meters, and so on. (The topology of the communication system is somewhat abstract, and must be distinguished from the physical or network topology of the mains network which supports the communication system. We will normally be concerned with the former, and will use the term "topology" alone for the former.)
A major feature of the standard system is that the message routing--ie the determination of the routes which messages take through the network--is determined substantially entirely by the central station. This is the only station with any significant knowledge of the topology of the system, and is also the only station which can initiate a message.
The central station includes, in each message, a route in the form of a meter list--a list of the meters through which the message is to pass. To read a meter (or otherwise communicate with it), the central station sends out a message to the meter, which inserts its reading into the message and sends it back to the centre| station. For present purposes, the route--the meter list--can be taken as remaining unchanged in the message throughout the message's journey to the destination meter and back again to the central station. (In fact, the standard system preferably uses slight variations on this.)


Topology Monitoring and Use

The standard system

REFERENCES:
patent: 4302750 (1981-11-01), Wadhwani et al.
patent: 4937569 (1990-06-01), Trask et al.
patent: 4968970 (1990-11-01), Laporte
patent: 5032833 (1991-07-01), Laporte

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