Engineering Recommendation G22

Transcription

1 PRODUCED BY THE ENGINEERING DIRECTORATE OF THE ENERGY NETWORKS ASSOCIATION Engineering Recommendation G22 Issue 3 Mains Signalling Systems Operating on the Low-Voltage Supply in the Frequency Range 3kHz to 148.5kHz energynetworks.org

2 2008 Energy Networks Association All rights reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior written consent of Energy Networks Association. Specific enquiries concerning this document should be addressed to: Engineering Directorate Energy Networks Association 18 Stanhope Place Marble Arch London W2 2HH This document has been prepared for use by members of the Energy Networks Association to take account of the conditions which apply to them. Advice should be taken from an appropriately qualified engineer on the suitability of this document for any other purpose.

3 Page 3 CONTENTS 1 INTRODUCTION PRINCIPAL FEATURES OF MAINS SIGNALLING BS EN THE STATUTORY POSITION European Directives and Use of Harmonised Standards The Electricity Act 1989 and The Utilities Act The Distribution Code and EN The Distribution Code and Access Rights Interference Observance of the Frequency Bands in BS EN PROVISION OF SERVICES Provision of services by DNOs Signalling outside customer premises by 3rd parties Signalling inside customer premises Power Quality Issues ADDITIONAL INFORMATION Common-mode devices Inadvertent Operation Complaints of Interference REFERENCES

4 Page 4 MAINS SIGNALLING SYSTEMS OPERATING ON THE LOW-VOLTAGE SUPPLY IN THE FREQUENCY RANGE 3 khz TO khz 1 INTRODUCTION The purpose of this engineering recommendation is to inform UK Distribution Network Owners (DNO) on the technical, conformance and regulatory aspects of mains signalling systems operating between 3 khz and khz on the low-voltage supply. This applies to use of such systems by the DNO and use by other parties who the DNO may wish to advise. Other users of mains signalling equipment may also find this useful. The title of this Engineering Recommendation has been modified from that in G22/2 in order to fit better with the European Standard and extended to include the frequency range in order to avoid any confusion with other powerline communication systems operating either on higher voltage sections of the electricity network or at higher carrier frequencies. This Engineering Recommendation applies only to the UK and the regulations currently in force and not to other countries where the harmonised standards may also apply. This Engineering Recommendation supersedes Engineering Recommendation G.22/2 as a result of: - further technical development of devices designed to use the electrical wiring installations of buildings or the Distribution Network Owners low-voltage network as a communication channel. - developments in international and national standards and legislation. This revision became necessary with the publication in 1992 of European Standard EN , which replaced the former British Standard on mains signalling. This was harmonised under the EMC Directive thus giving it a quasi-legal status in compliance matters relating to that Directive. At the same time The Utilities Supply and Works Contracts Regulations (Public Procurement.1992 SI No. 3279) came into force for large utility procurement contracts. To avoid conflict with this and possible later legislation, the technical specification contained in G22/2 is replaced in G22/3 by an appropriate reference to European Standards. These regulations have since been updated and replaced by, The Utilities Contracts Regulations 1996 (Statutory Instrument 1996 No. 2911) and an amendment, The Utilities Contracts (Amendment) Regulations 2001 (Statutory Instrument 2001 No. 2418). In addition BS EN has been revised in 2001 and the revised EMC Directive came into force in July 2007 as the Electromagnetic Compatibility Regulations: Statutory Instrument 2006 No This Engineering Recommendation has been examined to ensure that it meets the requirements of Regulation 12 of The Utilities Contracts Regulations 1996 (Statutory Instrument 1996 No. 2911). 4

5 Page 5 This Engineering Recommendation G22/3 was first redrafted in 1993, but publication was delayed for some considerable time pending clarification of how to treat regulatory statements in the European harmonised standard, for which there was no UK legislation. In the meantime G22/2 was withheld, but never withdrawn. Shortly after the 2001 revision of BS EN , the European Commission agreed with all three European standards organisations that regulatory statements would be removed from future harmonised standards and revisions of existing standards. So far there has been no further revision to the text of BS EN Guidance on how to interpret the current version of BS EN is given in Section Another more recent legislative change has been the introduction of the Communications Act As a result there is no longer any need for a Class License to operate systems which communicate over the DNO s network such as those for automatic meter reading and other applications. 2 PRINCIPAL FEATURES OF MAINS SIGNALLING The term 'mains signalling' implies the use of electrical power conductors to convey information in addition to power. The technique is by no means new, ripple control having been used for very many years but the development of reliable low-cost electronic components operating at higher frequencies and requiring much less power has widened the interest in the use of mains supply wiring as a transmission medium, both in buildings and on the distribution network. Mains signalling applications range from monitoring and control of the distribution network to automatic meter reading, load control and street lighting control. Within buildings it ranges in complexity from simple intercoms to building management systems. The type of mains signalling covered by this document operates below khz in order to avoid the European broadcast radio bands. There is no special frequency band allocated by regulatory authorities to this type of mains signalling, which has to observe existing electromagnetic compatibility (EMC) regulations. The European harmonised standard for mains signalling BS EN specifies limits, tests and measurement methods for injected signals and also specifies out-of-band limits above khz which are also compatible with the relevant harmonised product emission standard for EMC of information technology equipment, BS EN Compliance with these standards will significantly reduce the possibility of interference with other electronic systems. The great attraction of mains signalling is that virtually every building is wired for mains electricity so that using the same conductors as a communication channel offers a considerable reduction on the installation cost of a communication or control system. However, the mains is a hostile electrical environment for reliable communication and as a consequence early consumer equipment gained a reputation for inadvertent operation and a failure to communicate reliably between every node on the system. In most practical cases technical advances have since eliminated this, but nevertheless consumers and DNOs are advised to satisfy themselves by consulting the manufacturer that the equipment can deliver the appropriate quality of service for the intended application. 5

6 Page 6 Mains signalling has the disadvantage that all signalling systems on a network share a common medium and some form of separation is needed to avoid mutual interference. This separation may be achieved by: spatial separation of networks, with or without the use of filters to limit interchange of emissions; separation by frequency bands allocated to different types of application or; agreement on certain aspects of a common protocol such as; a means to control access via a method of contention resolution or, separate addressing mechanisms (not specified in BS EN ) 2.1 BS EN The main harmonised standard for mains signalling, BS EN specifies different bands for different applications. The band below 95 khz is reserved for use by or for electricity companies (i.e. DNOs in the UK). The band above 95 khz is for consumer use. Each band is subdivided into sub-bands. No distinction is made in this standard between the consumer s side of the supply terminals and the public supply network on the DNO s side. It should be noted that full permission of the DNO should always be sought for consumer equipment (i.e. belonging to a non-dno organisation) to be allowed to communicate across the network on the utility side of the supply terminals in addition to conforming to this standard in this respect. Similarly a system operating on the DNO side of the supply terminals may reach inside across the supply terminals to consumer premises. Interference with utility applications such as automatic meter reading is prevented by frequency separation and interference with other consumer within building applications such as energy management systems is protected by the access protocol, which is specified for the relevant sub-band in BS EN This access protocol prevents two compliant devices, even from different manufacturers systems, from transmitting at the same time on the same section of network. The only penalty is a slight increase in latency of the messages, which for the low duty-cycle applications that are most typical of this technology would have only a small effect on throughput. These two measures, frequency separation and access protocol, should normally be sufficient to prevent signalling installations interfering with each other or with other apparatus without necessitating the use of filters. It should be noted that, unlike the consumer band, there is currently no provision in the utility band (3 khz to 95 khz) for an access protocol or frequency multiplex system to allow the coexistence of multiple mains signalling systems on the same network sector. However spread-spectrum or frequency agile systems may be able to coexist with other systems. A second consumer sub-band is free of any access protocol requirements and was originally intended for pre-existing equipment and for applications using a continuous carrier frequency such a baby-alarms. Other than probability and spatial separation there are no special measures to prevent interference between different systems in this sub-band, but out-ofband emission limits must be observed together with regulations intended to prevent interference to other electronic equipment. Users of mains signalling equipment operating in this sub-band who experience interference from other users of this sub-band would be advised instead to consider using equipment designed to operate in the other band which has the access protocol. For more details on systems for use within buildings and for other commercially available systems the BEAMA Metering & Communication Association (BEMCA) may be consulted. 6

7 Page 7 3 THE STATUTORY POSITION 3.1 European Directives and Use of Harmonised Standards All products marketed in the European Union may be subject to European Directives. If a Directive applies to a specific product then it must comply with its essential requirements via the relevant national regulations. This product then is entitled to be CE-marked and placed on the market and put into service throughout the European Union without impediment. Therefore, in common with most other electrical apparatus, mains signalling systems have to comply with Directives and in particular the Electromagnetic Compatibility Regulations 2006 (Statutory Instrument 2006 No. 3418). The main essential requirement is that any electromagnetic disturbance generated by the apparatus must not exceed a level above which radio and telecommunications equipment or other equipment cannot operate as intended. Under these regulations manufacturers are entitled to have their own internal procedure to assess the compliance of their product with the regulations, with or without the involvement of an official notified body. If the apparatus is compliant the manufacturer is entitled to make a declaration of conformity to complete the process and fulfil the requirements of the regulation. However, as an alternative to his own assessment, the manufacturer can opt to have the apparatus tested against the relevant harmonised standard, such as BS EN , which is listed in the Official Journal under that Directive. If the apparatus passes the tests in the harmonised standard then it is presumed to be compliant with the essential requirements. For most manufacturers this is the preferred route to compliance and the right to use the CE-mark, and it is less subject to abuse and false declarations, but it is not mandatory under the regulations. CE-marking or compliance with the harmonised standard BS EN does not confer any right to use the apparatus on the DNO side of the supply terminals without permission from the DNO. It should also be noted that the emission limits in this and other EMC standards do not guarantee that interference will never be caused under any circumstances. As mains signalling apparatus must bear the CE-mark, which confers the right to unimpeded access to the UK market, no national regulation could override this by imposing further restrictions, or this would conflict with the essential requirements of the Electromagnetic Compatibility Regulations However, this does not preclude DNOs from making conformance to BS EN a condition in their own procurement process or to insist that apparatus installed on their distribution network by other users is compliant. Furthermore for certain large contracts the use of any alternative technical specification than the harmonised standard would have to meet the conditions of the Utilities Contracts Regulations 1996 and its 2001 amendment. For mains signalling equipment used on the distribution network, compliance with the harmonised standard BS EN has therefore been made a condition of the Distribution Code and this has been approved by Ofgem. BS EN has the status of a British Standard. The national foreword contained in British Standards states that compliance with a British Standard does not of itself confer immunity from legal obligations. 3.2 The Electricity Act 1989 and The Utilities Act 2000 Distribution licenses are issued by Ofgem under the Electricity Act 1989 as amended by The Utilities Act DNOs are obliged under their Licences, to observe a Distribution 7

8 Page 8 Code which has been approved by Ofgem. Whilst each DNO could put forward its own D Code, to date all licensed GB DNOs have opted to use a common D Code, colloquially known as the GB D Code. Independent Distribution Network Operators (IDNOs) might elect to propose their own D Code(s) or may choose to use the GB D Code. All references to Distribution Code elsewhere in this Engineering Recommendation refer to the GB D Code The Distribution Code and EN50065 Under the section on the Distribution Planning and Connection Code, DPC4.4.5 states that where users install mains borne signalling equipment it shall comply with European Standard EN as amended from time to time. This means that mains signalling apparatus installed on the DNO network must conform to the whole of BS EN (as appropriate to the equipment), not just BS EN A list of all parts of BS EN is given in Section 6. Some requirements in BS EN might be considered to be optional with respect to compliance with Electromagnetic Compatibility Regulations 2006 and CE-marking, but the Distribution Code implies that apparatus must comply with all requirements. BS EN :2001 contains certain regulatory statements, which are not directly enforceable in the UK without a regulation or law to support them. Such statements should be considered to be overruled by the regulations and code of practice referenced in this Engineering Recommendation. These regulatory statements are however broadly in line with these regulations. One example of a regulatory statement is in Clause 4.2 of the 2001 revision of BS EN With regard to the use of the higher injection level, this declares that the use of Class 134 equipment may require prior notification, or consent of, appropriate authorities. This is non-specific because ownership and operation of distribution networks differ from country to country and may even be split between organisations. If interference were to be caused by such a system, then action could be taken under the Electricity Safety, Quality and Continuity Regulations (see 3.3) The Distribution Code and Access Rights DPC4.4.5 also states that where a user proposes to use such equipment to superimpose signals on the DNO s Distribution System, the prior agreement of the DNO is required. The fact that this comes under the Distribution Planning and Connection Code implies that this applies only to the public supply network on the DNO s side of the supply terminals. The DNO would have no control over consumer apparatus on the consumer s side of the supply terminals unless there was a problem of interference, but such apparatus must be CE-marked to indicate compliance with the regulations. At this point in time the use of automatic meter reading systems using mains signalling in a competitive environment has not been addressed. It should be noted that to date Automatic Meter Reading (AMR) systems have used the utility band (3 khz to 95 khz) for which there is no standardised scheme for two or more systems to coexist on the same network sector. DNO s who give permission for their network to be used for this and similar applications should be aware of the commercial issues this might raise. 8

9 Page Interference There is an over-riding duty on the part of every user of an electricity supply to avoid interference with other users of the same supply or with the DNO s system. The DNO has power in regulation 26(1) of the Electricity Safety, Quality and Continuity Regulations 2002 (Statutory Instrument 2002 No. 2665) to insist on remedial works or to disconnect the supply if there is interference with his or any other distributor's network, or with the supply to any consumer's installation or street electrical fixture. 3.4 Observance of the Frequency Bands in BS EN It is in the interest of all users to respect the use of the appropriate frequency bands as specified in this standard. However, once apparatus has passed the specified tests in BS EN and subsequently been entitled to use the CE-mark, there is no prior mechanism to prevent a user from installing this apparatus inappropriately. For example apparatus designed to operate in the utility band might be purchased and installed by a consumer on consumer premises for a non-utility application without the knowledge of the DNO. The lack of any standardised protocol in the band might then lead to interference with other systems using the utility band. However the apparatus would not be conforming to the requirement in the Electromagnetic Compatibility Regulations 2006 to not cause interference, despite being CE-marked to denote conformance to the same regulations. In addition action could also be taken under the Electricity Safety, Quality and Continuity Regulations 2002 (see 3.3 above). 4 PROVISION OF SERVICES 4.1 Provision of services by DNOs A DNO may wish to use mains communication as part of a core business activity in relation to the carriage of electricity. However, if a communication service for a non-core business activity were to be provided to a third party, either directly or indirectly, it might be advisable to clarify the regulatory position with Ofgem. It might also be appropriate to check way leave agreements in relation to the intended application. This would also apply to signalling by third parties (Section 4.2). 4.2 Signalling outside customer premises by 3rd parties Since the introduction of the Communications Act 2003 there is no longer any prohibition of communication between customers over the DNO s network external to the supply terminals and neither is there no longer a need for a Class License, but other provisions of the Communications Act may apply. However users should be advised that use of the DNO s network is not allowed without prior permission from the DNO. The legal situation regarding access rights is detailed in Section A DNO giving permission for his network to be used by third parties would be entitled to levy a charge for use-of-system (see Section 4.1 for regulatory position). The DNO would be advised to take into account any additional operational overhead incurred in managing the network, particularly in repairing faults where there might be a conflict between the requirements pertaining to the carriage of electricity and operating a communications service with minimum downtime. 9

10 Page Signalling inside customer premises Enquirers considering the connection of ordinary consumer devices on the customer s side of the supply terminals should be advised to check that the apparatus is CE-marked and preferably whether it complies BS EN and other parts of BS EN as appropriate. The instructions provided by the manufacturer or supplier should give sufficient information and cautions regarding the installation and use of the apparatus. The BEAMA Metering & Communication Association (BEMCA) may also be consulted. 4.4 Power Quality Issues According to Issue 8 of the Distribution Code, DPC Sections 2 and 3 of BS EN 50160:1995 Voltage Characteristics of Electricity Supplied by Public Distribution Systems, as amended from time to time, contain additional details of the variations and disturbances to the voltage which shall be taken into account in selecting Equipment from an appropriate specification for installation on or connected to the System. Section 2.13 of BS EN 50160:1995 contains mains signalling requirements for the LV-network. In addition Section 3.13 contains mains signalling requirements for the MV-network, although this is outside the scope of G22/3 and outside the scope of BS EN Later revisions of BS EN contain identical text on mains signalling on the LV-network in sections 3.13 (2000 revision) and 4.13 (2007 revision). Mains signalling systems that already conform to BS EN should automatically meet the power quality requirements of BS EN 50160, Voltage characteristics of electricity supplied by public distribution networks. 5 ADDITIONAL INFORMATION 5.1 Common-mode devices The 1992 version of BS EN allowed use of the frequency band 3kHz to 9kHz for signalling in customers' premises under conditions authorised by the electricity supplier. This clause was inserted to permit the use of a common-mode signalling system manufactured and used in the UK. The 2001 revision of BS EN has removed this clause due to objections from other countries and the fact that this equipment had ceased manufacture. Reported problems in the 1990s with one particular residual current device resulted in the use of common-mode signalling (between line/neutral and earth) being discouraged in the revision of BS EN , which now states that common-mode signalling may now only be used under the following conditions: Common-mode injection devices may disturb the normal operation of residual current protection devices and causes serious safety hazards to the user. Therefore, on commonmode injection injection devices a clearly written warning (either on the product or on the leaflet) shall indicate: Due to safety reasons the use of this product is not allowed in the residential environment. Use of common-mode injection devices in industrial and commercial environments is under the responsibility of the installer and must be in accordance with the local regulations 10

11 Page Inadvertent Operation BS EN gives the following safety advice: Mains signalling must not be used to control equipment that could become a hazard to people or property if it inadvertently operates or fails to operate in any way. 5.3 Complaints of Interference Mains signalling compliant to BS EN is now a relatively mature technology with significant deployment in Europe and there is no history at all of it causing interference. BS EN was prepared with the object of limiting mutual interference between mains signalling systems or interference with other equipment, but it cannot guarantee complete freedom from interference in all situations. The mains signalling frequency bands are below the European broadcast bands and there are few radio services in the mains signalling bands. It should be noted that there is also a possibility of causing interference outside the mains signalling bands, but this is unlikely provided the out-of-band limits in BS EN are observed. There is also the possibility of interference with other electronic equipment via conducted disturbance, but CE-marking of such other equipment is also required to indicate compliance with the immunity requirements of the Electromagnetic Compatibility Regulations If a DNO were to receive a complaint of interference or mal-operation of a customer s equipment, which could be signalling apparatus or other equipment, the source of interference could be the DNO s own equipment, another customer s mains signalling system or other electronic equipment. If the source of interference could be identified the parties concerned should try to resolve this mutually in the first instance and, if necessary consult the manufacturer of the equipment. Checks might also be made to determine whether the victim equipment has appropriate immunity in line with the relevant harmonised standards. Mitigation measures such as the use of appropriate filters might also be considered, but care should be taken that these do not interfere with wanted signals. Part 2 of BS EN covers immunity of mains signalling apparatus and Part 4 covers filters for mains signalling. There are also generic standards for immunity and standards for specific technologies. For example immunity of information technology equipment is covered by BS EN 55024, although there are no requirements below 150 khz. If the problem is not mutually resolved then a complaint could be referred to Ofcom ( ). In a case of alleged conducted interference from a mains signalling system, a complainant might suggest that the supply does not meet the power quality requirements of the Distribution Code as detailed in BS EN and this might be raised with Ofgem. It should be noted that mains signalling systems that conform to BS EN should automatically conform to the mains signalling requirements in BS EN (See Section 4.4). If it is suspected that equipment causing the interference does not comply with The Electromagnetic Compatibility Regulations 2006, the apparatus may be incorrectly CE-marked, in which case this is a trading matter and now comes under the Department for Business, Enterprise and Regulatory Reform (BERR, formerly the DTI), through National Weights and Measures and the Trading Standards Departments of Local Authorities. The first port of call may be Consumer Direct at 11

12 Page 12 The lack of any history of interference complaints against mains signalling systems that are compliant with BS EN means there is no experience of the efficiency or scope of these mechanisms for reporting complaints of interference. 6 REFERENCES All references and links are correct at the time of issue. The Distribution Code The Electricity Safety, Quality and Continuity Regulations 2002 (Statutory Instrument 2002 No. 2665) The Electricity Act The Electromagnetic Compatibility Regulations 2006 (Statutory Instrument 2006 No. 3418) The Utilities Act The Utilities Contracts Regulations 1996 (Statutory Instrument 1996 No. 2911) The Utilities Contracts (Amendment) Regulations 2001 (Statutory Instrument 2001 No. 2418) The Communications Act Note: These may be amended from time to time. BEAMA Metering & Communication Association (BEMCA), Westminster Tower, 3 Albert Embankment, London SE1 7SL 12

13 Page 13 Standards referenced in this document British Standards (BSi) has the copyright of the English language versions of European Standards which may be purchased from Note: undated standards references are given below to cover future revisions. BS EN BS EN BS EN BS EN Voltage Characteristics of Electricity Supplied by Public Distribution Systems Information technology equipment. Radio disturbance characteristics. Limits and methods of measurement... Information technology equipment. Immunity characteristics. Limits and methods of measurement. Signalling on low voltage electrical installations in the frequency range 3 khz to 148,5 khz This standard is available in the following separate parts:- BS EN Part 1: General requirements, frequency bands and electromagnetic disturbances BS EN Part 2-1: Immunity requirements for mains communications equipment and systems operating in the range of frequencies 95 khz to 148,5 khz and intended for use in residential, commercial and light industrial environments BS EN Part 2-2: Immunity requirements for mains communications equipment and systems operating in the range of frequencies 95 khz to 148,5 khz and intended for use in industrial environments BS EN Part 2-3: Immunity requirements for mains communications equipment and systems operating in the range of frequencies 3 khz to 95 khz and intended for use by electricity suppliers and distributors BS EN Part 4-1: Low voltage decoupling filters - Generic specification BS EN Part 4-2: Low voltage decoupling filters - Safety requirements BS EN Part 4-3: Low voltage decoupling filters - Incoming filter BS EN Part 4-4: Low voltage decoupling filters - Impedance filter BS EN Part 4-5: Low voltage decoupling filters - Segmentation filter BS EN Part 4-6: Low voltage decoupling filters - Phase coupler BS EN Part 4-7: Portable low voltage decoupling filters - Safety requirements BS EN Part 7: Equipment impedance 13