关于plc的中英文翻译

PLC Studies in China as a Contribution to the Development

of International Standards

The sources of disturbance are both radiated and conducted:

- the emission of electromagnetic noise which can interfere with radio communications for safety or military use, or disturb the radio amateurs; - conducted differential and common mode currents can penetrate in any equipment connected to the network in which PLC is working. The disturbances have two types of origins:

- the signal source asymmetry, due to the coupler asymmetry;

- the unbalance of the Low Voltage Distribution Network (LVDN) and as a result an common mode to differential mode conversion.

The conversion from differential to common mode due to the network unbalance has been analysed in various paper, as for instance in [1]. Different mitigation solutions have been also been proposed in the literature [2, 3, 4], but the research work must be further continued.

3. Standardization at international level

Concerning EMC problems, at an international level, two types of standards must be developed:

- a product standard;

- a network standard.

3.1 The product standard

The product standard should be an amendment of the CISPR22 standard and is the task of the Subcommittee CISPR/I/.

A first idea was to extend the concept of Longitudinal Conversion Loss (LCL) specific for symmetric telecommunication pairs of wire to the non symmetric power network.

Measurements performed in various power networks, as those shown in Fig. 1, have given a large spread of LCL values [5].

It was not possible to arrive to a consensus for the concept based on the LCL value, to be used for the calculation of a voltage limit at the ports of the equipment connected to the network, although that this concept has been well-established for the case of telecommunication lines. After about 4 years of work and a whole series of documents at CD (Committee Draft) stage, the concept did not find the requested qualified majority for approval by the CISPR/I/ although that it found majority approval within the working group. It was decided to re-start the work evaluating a new basis.

A New Work Item Proposal (NWIP) was prepared by the French national Committee and approved in April 2005 [6]. The work will not be focused any more on the LCL value, but will try to:

- describe the typical electricity installations where it is intended to connect PLC equipment;

- identify the potentially disturbed services/equipment for each typical section of electricity installations described above;

- assess the level of protection currently provided by the CISPR22

for each equipment/service;

- set radiated and conducted limits for emissions of each typical section of electricity installation when PLC is operating.

The work started in June 2005 and is currently in progress.

3.2 Network standard

The European Commission has issued in 2001 the Mandate 313 which gives CENELEC and ETSI the task to develop a standard, to define emission limits for all communication networks including PLC [7].

Different limits have been proposed by various countries (Germany, UK, Norway) and entities (CENELEC, FCC, BBC). The differences between the various proposals were quite large and it was not possible to reach a consensus.

A Joint Working Group ETSI/CENELEC has produced several drafts, which have all failed to be approved by the National Committees.