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1 Code of Practice 290 Issue 1 January 2004 Power Quality Contents 1 Introduction 2 Scope 3 Definitions 4 Elements of Power Quality 5 Power Quality Standards 6 Power Quality Measurement Standards 7 Practical application of standards 8 Documents Referenced 9 Keywords Appendices A to B Approved for issue by the Technical Policy Panel All Rights Reserved The copyright of this document, which contains information of a proprietary nature, is vested in Electricity North West Limited. The contents of this document may not be used for purposes other than that for which it has been supplied and may not be reproduced, either wholly or in part, in any way whatsoever. It may not be used by, or its contents divulged to, any other person whatsoever without the prior written permission of Electricity North West Limited. Electricity North West Limited. Registered in England & Wales. Registered No Registered Office: 304 Bridgewater Place, Birchwood Park, Warrington, WA3 6XG

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3 Amendment No. Date 0 Issue 1 Amendment Summary Brief Description and Amending Action 05/01/04 Prepared by: D M Talbot. Authorised by the Standards Steering Group and signed on its behalf by: P. J. Whittaker. CP290.doc Issue 1 05/01/04 DMT CP290 Page i of i

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5 POWER QUALITY 1. INTRODUCTION 1.1 This Code of Practice has been written to improve the understanding of power quality, and the practical application and interpretation of power quality standards. Electricity North West policy on power quality is detailed in EPD 290. This Code of Practice provides more detail on power quality standards and clarifies their relationship with industry standards and statutory requirements. It should be used as a reference for power quality and all power quality measurements with in Electricity North Wes must conform to this Code of Practice. 1.2 Power quality is an expression used to describe the deviation from a perfect power supply. A perfect power supply is one that is never interrupted, always within voltage and frequency tolerances and has a noise free sinusoidal waveform. 1.3 The types of disturbances that affect the power quality of supply are harmonics, supply interruptions (short and long term), flicker, under or over voltage. Each of these disturbances has different causes and effects. Some result from use of customers equipment, whilst others are a product of lightning strikes or system faults. 1.4 Disturbances can propagate up or down the system and could affect other customers. Customers who are supplied from a shared network may experience similar power quality problems depending on the immunity of their equipment. 1.5 Measuring equipment is available to measure all aspects of power quality. Should a problem be identified after monitoring has been completed, then network reconfiguration, reinforcement, mitigation or conditioning can be considered to ensure the standards are met. 2. SCOPE This Code of Practice is to provide guidance on the application of power quality. It will describe the elements of power quality, its causes, effects, measurement and standards, and the practical application of these standards. 3. DEFINITIONS 3.1 ESQCR (2002) Electricity Supply, Quality and Continuity Regulation (2002). 3.2 EMC Electro-Magnetic Compatibility. 3.3 IEC International-technical Committee. 3.4 EN European Norm. 3.5 BS British Standard. 3.6 BS EN British Standard European Norm. 3.7 Distribution Code - Distribution Code of Licensed Distribution Network Operators of Great Britain. 3.8 ER Engineering Report. 3.9 ETR Engineering Technical Report RMS Root Mean Square. CP290.doc Issue 1 05/01/04 DMT CP290 Page 1 of 15

6 3.11 ENA Energy Networks Association DTI Department of Trade & Industry LV Low Voltage is defined in industry standards as a voltage whose upper limit of nominal rms value is 1kV, and in statutory requirements the definition is a voltage exceeding 50 volts but not exceeding 1000 volts MV Medium Voltage is only defined in industry standards as a nominal rms value that lies between 1kV and 35kV. Statutory requirements would consider the range of voltages quoted as part of the high voltage range and all references to mv should be considered as high voltage in this Code of Practice HV High Voltage is defined in industry standards as a nominal rms value that exceeds 35kV, whereas, in statutory requirements high voltage means any voltage exceeding LV. 4. ELEMENTS OF POWER QUALITY 4.1 Dips A sudden reduction or dip in the supply voltage is described by the duration of the retained voltage, i.e. the percentage of the supply voltage retained during the event. A dip is defined as a retained voltage of between 90% and 1% for between 10ms and 1 minute. A change in the supply voltage, resulting in a retained voltage of greater than 90% is not considered as a dip Voltage dips are unpredictable, random events and are caused by disturbances that occur on the system. The disturbances, which could be faults, can occur on all parts of the system and customer installations. Other dips may be caused by switching of large loads, such as starting of large motors. The propagation and frequency of dips will depend on the point at which the event occurred Most equipment manufactured should be resilient to some form of dips. However, some equipment may be more sensitive than others, such as electronic equipment (computers etc). It is possible to increase the resilience of electronic equipment to dips through re-design or specification. The resilience to dips is represented by the Information Technology Industry Council (ITIC) curve. Dips are plotted against the percentage of retained voltage and the duration. Dips that occur outside the boundary line are more like to cause a problem to electronic equipment. 4.2 Interruptions An interruption is when the voltage at the point of supply is lower than 1% of the nominal supply voltage A short interruption is up to three minutes duration and caused by a transient, permanent fault or outage. Transient faults will generally be in terms of seconds with the operation of reclosers. Although some customers initially affected by a permanent fault, may be restored by remote controlled switching within three minutes: assuming they are not within the faulty network A long interruption is greater than three minutes duration caused by a permanent fault or pre-planned outage. CP290.doc Issue 1 05/01/04 DMT CP290 Page 2 of 15

7 4.3 Flicker or Voltage Fluctuation Voltage fluctuations are changes in the voltage amplitude for a time, longer than the period of the voltage. Voltage fluctuations can occur once, several times, randomly or regularly. If the voltage fluctuation occurs at a frequency of approximately 0.005Hz 35Hz, a noticeable flicker will occur in electric lighting. This flicker will increase with the amplitude of the voltage fluctuation, but is also dependent on the frequency with which the voltage fluctuation occurs and on the type of lamp used The human eye is perceptive to this light flicker and the eye is more sensitive at a frequency of around 8Hz. However, once sensitised it may be difficult to satisfy a customer even though the flicker has been reduced Voltage fluctuation usually arises from rapidly changing customer loads, such as, resistance welders, arc furnaces and motor starting. 4.4 Harmonics Harmonic frequencies distort the sinusoidal supply waveform. The harmonic frequencies are integer multiples of the fundamental supply frequency. Using Fourier series analysis the individual frequency components of the distorted waveform can be described in terms of the harmonic order, magnitude and phase of each component. For example, with a fundamental supply frequency of 50Hz, then the 3 rd harmonic would be 150Hz and the 5 th Harmonic would be 250Hz Harmonics occur due to non-linear loads connected to the system. Typically, nonlinear loads are rectifiers, power supplies for electronic equipment and variable speed drives. These loads cause harmonic currents and when coupled with the network impedance result in harmonic voltages being produced Harmonic currents can cause increased loading of neutrals, overheating of transformers, nuisance tripping of circuit breakers, over-stressing of power factor correction capacitors and skin effect Neutral conductor over-heating In equally balanced three-phase systems with pure sinusoidal waveforms, then the current in the neutral will be zero. Some cable systems have been installed with half-sized neutral conductors with respect to the size of the phase conductors. However, the harmonics currents don t cancel out, in fact the odd multiples of three times the fundamental, the triple-n harmonics, add in the neutral conductor resulting in overheating Over-heating of transformers The eddy current losses increase with the square of the harmonic number. A transformer supplying computer equipment would have losses twice that of a transformer supplying an equivalent linear load. This may result in a higher operating temperature and a shorter transformer life Nuisance tripping of circuit breakers Customers may experience problems of nuisance tripping of circuit breakers caused by harmonics. The protection may not sum the high frequency components correctly, resulting in nuisance tripping CP290.doc Issue 1 05/01/04 DMT CP290 Page 3 of 15

8 4.4.7 Over-stressing of power factor correction capacitors It is possible for resonance to occur given the right combination of inductance, capacitance and harmonic frequency. When this happens, large voltages and currents are generated leading to catastrophic failure of the capacitor Skin effect High frequency harmonic currents flow on the outer surface of the conductor (350Hz and above), which causes additional losses and heating in the conductor Harmonic voltages cause voltage distortion, zero-crossing noise and over-heating of induction motors. Additional losses generated by harmonics cause induction motors to over-heat, which is similar to the problem previously identified with transformers. Electronic timers base their timing on zero-crossings. However, a distorted waveform may result in additional zero-crossings affecting the operation of these devices Inter-harmonics An inter-harmonic is a sinusoidal voltage whose frequency is not an integer multiple of the fundamental Experiments conducted previously in the UK have concluded that the most significant effect of inter-harmonics is on flicker levels. When the inter-harmonic voltage is superimposed on the supply voltage a beat frequency can be established. A beat frequency in the 8-10Hz range causes the most pronounced level of flicker. The level of inter-harmonic distortion necessary to cause flicker in excess of Pst = 1.0 is dependent upon the inter-harmonic frequency. Inter-harmonics with a frequency close to 40Hz or 60Hz and a magnitude above 0.1% of the fundamental voltage will result in values of Pst close to The levels of inter-harmonic necessary to distort the function of house hold electronic equipment is so high that the effects of flicker on lighting would be intolerable. Typically, the image on a TV screen only starts to experience distortion when the inter-harmonic magnitude reaches 1.5% and for other appliances (Hi Fi and PC) there was no noticeable reduction in output quality with inter-harmonics up to 5%. 4.5 Under Voltage and Over Voltage The voltage at the supply terminals shall comply with the ESQCR (2002). When the voltage is above the permitted variation it is referred to as an over voltage and below as an under voltage. 4.6 Voltage Unbalance The level of voltage unbalance in a three-phase system is expressed as a percentage between the rms values of the negative sequence component and the positive sequence component of the supply voltage. CP290.doc Issue 1 05/01/04 DMT CP290 Page 4 of 15

9 5. POWER QUALITY STANDARDS 5.1 Background European Directives are prepared by the European Commission to ensure consistency of approach and promote free trade within the European Union. The EMC Directive is supported by IEC EMC standards. CENELEC is the European standards making body and they have used the IEC standards to produce the EN standards. The British standards are based on the EN standard, resulting in a BS EN being produced. The IEC also produces Technical reports to clarify issues Once an IEC standard has been issued it is normally adopted as a BS EN. There is no requirement to adhere to an IEC standard, but if adopted as a BS EN then the standard is mandatory. All BS EN standards referenced are IEC and/or EN standards with the same numeric reference The Electricity Distribution Licence makes reference to the Distribution Code. The Distribution Code requires compliance with the ESQCR (2002) and specific Engineering Recommendations. The Engineering Recommendations make reference back to IEC and BS EN standards Other relevant documents, which focus on practical aspects of power quality, include ETR and ACE reports produced by the ENA. 5.2 Standards The BS EN series of standards and planning levels assist in achieving adequate power quality and in controlling it. While BS EN defines power quality in terms of voltage characteristics that can be supplied under normal conditions. Planning levels exist to limit disturbance levels exceeding compatibility levels and conversely immunity levels should remain above these compatibility levels. Figure 1: Summary of relationships between planning, compatibility and immunity levels. Probability Density Total supply network Compatibility Level Planning levels Immunity (test) levels Immunity levels of local equipment Disturbance CP290.doc Issue 1 05/01/04 DMT CP290 Page 5 of 15

10 Figure 1, shows the probability density disturbance of the total supply network on the left side, while on the right the levels of equipment immunity to these disturbances. Generally, planning levels limit network disturbances exceeding the compatibility level. Immunity levels are set above the compatibility level to ensure functionally of equipment. The compatibility level is the point at which the disturbance will affect the functionally of equipment IEC/BS EN series: Electromagnetic Compatibility (EMC) Part 1 covers general considerations, fundamental principles, definitions and terminology of EMC Part 2 deals with classifications of electromagnetic environment and compatibility levels Part 3 details emission and immunity limits for terminating equipment Part 4 defines testing and measurement techniques used to assess equipment compliance to emissions and immunity to disturbances Part 5 describes installation and mitigation guidelines for building installation systems Part 6 contains generic immunity and emission standards for residential, commercial and industrial environments BS EN 50160: Voltage Characteristics of Electricity Supplied by the Public Distribution Systems The limits quoted in BS EN are in general more in line with compatibility levels and as such the Distribution Code shall be followed for distribution planning and power quality. Where the Distribution Code does not cover a power quality element then the limits set in BS EN should be used. Appendix A summarises the power quality standards, Engineering Recommendations and regulations and the compliance standards are highlighted in bold BS EN does not apply to abnormal conditions, as stated below. Conditions arising as a result of a fault or a temporary supply arrangement adopted to keep customers supplied during maintenance and construction work or to minimise the extent and duration of a loss of supply. In cases of non-compliance of a customer s installation or equipment with the relevant standards or with the technical requirements for connection of loads, established by the electricity supplier (with in the UK this is interpreted as the Distribution Network Operator). In cases of non-compliance of a generator installation with the relevant standards or with the technical requirements for interconnection with an electricity distribution system established by the electricity supplier (e.g. embedded generation). In exceptional situations outside the electricity supplier s control, as outlined in CP290.doc Issue 1 05/01/04 DMT CP290 Page 6 of 15

11 5.2.4 Voltage Harmonisation 5.3 The Distribution Code The CENELEC group responsible for voltage harmonisation has decided to extend the transition period for the tolerances in HD472 S1: Nominal voltage for low voltage public electricity supply voltage up to 1 January This means that the low-voltage tolerances for the UK will remain at 230 volts +10 % -6% until 1 January The Electricity Distribution Licence refers to the Distribution Code, which requires compliance with the ESQCR 2002 for frequency and voltage. While, for voltage disturbances and harmonic distortion then Engineering Recommendations P28, P29 and G5/4 shall be followed In other cases of variations and disturbances to the voltage, then the Distribution Code makes reference to Sections 2 and 3 of BS EN ESQCR (2002) ESQCR (2002) defines a frequency of 50Hz and low voltage supply of 230V with a permitted variation of ±1% for frequency and +10% or 6% for voltage, ±6% for high voltage operating below 132kV, but ±10% for high voltage operating at 132kV or above There is no clear guidance in the ESQCR (2002) on how these quantities are measured and under what operating conditions. BS EN shall be referred to when carrying out measurements of these quantities under normal operating conditions. The 10 minute mean rms value is dedicated to slow variations within the limits and voltages outside of these limits are categorised as either a voltage dip, flicker or over voltage and should be excluded from the 10 minute rms value The ESQCR (2002) refers to exceptional circumstances, but offers no clear explanation of this expression. BS EN should be used to interpret this statement as exceptional situations outside the electricity supplier s control, as stated below. Exceptional weather conditions and other natural disasters. Third party interference. Acts by public authorities. Industrial actions. Force majeure. Power shortages resulting from external events ESQCR (2002) permits the distributor to challenge the consumer in circumstances where connected equipment is causing unacceptable electrical interference on the distributors network. If after the expiry of the specified period the defective equipment has not been repaired or replaced, the distributor may disconnect the supply to the premises or other network or refuse to connect the supply until the problem is rectified. The distributor must restore the supply as soon as practical after the problem has been rectified. In cases where disputes cannot be resolved between the distributor and the consumer, the DTI inspector will investigate the circumstances and bring the dispute to a resolution. CP290.doc Issue 1 05/01/04 DMT CP290 Page 7 of 15

12 5.5 Engineering Recommendations and Technical Reports The power quality elements covered by engineering recommendation and technical reports are flicker, voltage unbalance, harmonics and inter-harmonics Flicker IEC Environment standards cover flicker for environment and compatibility levels. BS EN : Compatibility levels for low frequency conducted disturbance and signalling in public low voltage power supply systems. BS EN : Compatibility levels in industrial plant for low frequency conducted disturbances. BS EN : Compatibility levels for low frequency conducted disturbances and signalling in public medium voltage power supply systems IEC Defines the emission and immunity limits for flicker. BS EN : Limitation of voltage changes, voltage fluctuations and flicker in public low voltage supply systems, for equipment with rated current <= 16A per phase and not subject to conditional connection. BS EN : Limitation of voltage changes, voltage fluctuations and flicker in public low voltage supply systems, for equipment with rated current <= 75A per phase and not subject to conditional connection. IEC TR/ : Limitation of voltage changes, voltage fluctuations and flicker in public low voltage supply systems, for equipment with rated current greater than 16A per phase ER P.28 Planning limits for voltage fluctuations caused by industrial, commercial and domestic equipment in the UK. ER P.28 deals with planning limits for voltage fluctuations caused by industrial, commercial and domestic equipment in the UK. Three IEC standards mainly underpin ER P.28. BS EN which applies to stage 1 assessment in P.28, BS EN which applies to stage 2 assessment in P28 and IEC TR/ which applies to HV connections stage 3 assessment in P28. ER P.28 interprets these standards and there is no requirement to make direct reference. CP290.doc Issue 1 05/01/04 DMT CP290 Page 8 of 15

13 5.5.2 Voltage unbalance IEC Environment standards cover voltage unbalance for environment and compatibility levels. BS EN : Compatibility levels for low frequency conducted disturbance and signalling in public low voltage power supply systems. BS EN : Harmonic Compatibility levels for public MV systems ER P29 - Planning limits for voltage unbalance Harmonics ER P29 deals with planning limits for voltage unbalance by industrial, commercial and domestic equipment in the UK. The levels are defined as a max of 1.3% for voltages up to 33kV and 1% for voltages not exceeding 132kV. For periods up to 1 minute the level may increase to 2% IEC Environment standards cover harmonics for environment and compatibility levels. BS EN : Limits for harmonic current emission (equipment input current to and including 16A per phase). BS IEC : Limitation of emissions of harmonic currents on low-voltage power supply systems for equipment with rated current greater than 16A. IEC/TR : Assessment of emission limits for distorting loads in MV and HV power systems ER G5/4 Planning limits for harmonic voltage distortion and the connection of non-linear equipment to transmission systems and distribution networks in the UK. ER G5/4 deals with planning limits for harmonic voltage distortion caused by non-linear loads. Three IEC standards mainly underpin ER P.28. BS EN which applies to LV connections (stage 1 G5/4), BS EN which applies to stage 2 (G5/4) and IEC TR which applies to HV connections (stage 3 G5/4). ER G5/4 interprets these standards and there is no requirement to directly reference these standards. ETR 122: Guide to the application of engineering recommendation G5/4 planning levels for harmonic distortion and the connection of non-linear load to supply systems in the UK. ETR 122 was published in December It provides guidance on the use of G5/4 in assessing the connection of non-linear loads. CP290.doc Issue 1 05/01/04 DMT CP290 Page 9 of 15

14 5.5.4 Appendix A: Summary of Elements of Power Quality and relating standards highlights the standards, Engineering Recommendations and regulations, which must be followed for power quality compliance and measurement. 6. POWER QUALITY MEASUREMENT STANDARDS 6.1 Measurement standards BS EN : Testing and measurement techniques Power quality measurement methods. This standard defines, in detail, the performance requirements for instruments for all types of disturbances for both compliance and indicative purposes BS EN : General guide on harmonics and inter-harmonics measurements and instrumentation, for power supply systems and equipment connected thereto. This standard defines measurement instruments for harmonic testing BS EN : Flickermeter Functional and design specifications Basic EMC publication. This standard gives the functional and design specification for flicker measurement BS EN 50160: Voltage characteristics of electricity supplied by public distribution systems. EN50160 details how the measurement should be carried out (period etc) The table in Appendix A highlights the standards, Engineering Recommendations and regulations, which must be followed for power quality compliance and measurement. 6.2 Instrument Classification Type A instrument Type A instruments are used where precise measurements are required in cases of verifying compliance with standards and resolving disputes Any Type A instrument must produce matching results within the specified accuracy This type of instrument must be used when providing voltage recordings, whether orally or written, to the customer or third party for compliance with power quality limits Type B instrument Type B instruments are used for surveys and troubleshooting where high accuracy is not required The manufacturer specifies the accuracy and aggregation method to be used for Type B instruments Reference should be sought to BS EN , BS EN , BS EN , BS EN 50160, ER P28, ER P29 and ER G5/4 when carrying out power quality measurements relating to compliance of standards and disputes. CP290.doc Issue 1 05/01/04 DMT CP290 Page 10 of 15

15 7. PRACTICAL APPLICATION OF STANDARDS Planning levels are set above compatibility levels to achieve adequate power quality. Connection of new loads should be checked against these planning levels. Connected loads should have been checked originally against these planning levels. The investigation of a voltage complaint may show that equipment has been connected without approval and should be checked against planning levels. 7.1 Network Design and connection of new loads Network design and connection of new loads must be carried out to the guidance within EPD Any measurements should be carried out in accordance with BS EN and a type A instrument to BS EN Connected loads Voltage complaints When a customer contacts Electricity North Wes to complain of under/over voltage, frequency or voltage distortion then initial investigations will be carried out to determine whether power quality limits have been breached (limits outlined in Appendix A) Corrective actions may be possible to restore some of the power quality elements back within limits without network reinforcement or further investigations. The supply voltage may be corrected through reconfiguring the network, by adjusting transformer tappings, and/or transferring loads to other feeders or phases (refer to ER P29 for voltage unbalance). High impedance or poor connections within the network can cause voltage fluctuations or flicker and attempts should be made to check all available connections by a suitable authorised person Network referral A network referral will be required should these attempts prove unsuccessful or unnecessary due to the nature of the power quality problem. In such cases, a Network Referral form must be completed in full and accompanied by supporting documentation (voltage chart etc). Any reconfiguration of the network should be included in the interim measures already applied on the network referral form together with any further supporting documentation carried out after the completion of these measures It is advisable to locate the source and treat the power quality problem at source, which is more effective than network reconfiguration or reinforcement. It may be useful to carry out investigations, under the referral process, to discover the source or cause of the voltage distortion through the aid of a type B indicative instrument. In all cases, once the source has been located, a type A instrument, must be used to verify the power quality limits. CP290.doc Issue 1 05/01/04 DMT CP290 Page 11 of 15

16 7.3 Enforcement The consumer may be challenged if the connected equipment is causing unacceptable electrical interference on the network. Every effort should be made to work with the consumer to identify the equipment causing the disturbance, explain the problems this equipment is causing to other consumers and discuss possible solutions. The supply may be disconnected under the due process of the ESQCR (2002), which is outlined in section 5.4.4, if the consumer is unwilling to realise a solution. 7.4 Practical Measurements It is important to use the correct type of instrument, as detailed in BS EN , BS EN , BS EN , and use BS EN50160 to determine how the measurements should be carried out and limits that should be used for compliance as outlined in Appendix A. Frequency ESQCR (2002) Voltage ESQCR (2002) Voltage Dips BS EN Flicker ER P28 Harmonics & inter-harmonics ER G5/4 Interruptions BS EN Voltage unbalance ER P The supply voltage, shall be measured by the type of instrument specified in BS EN , e.g. A type A instrument must measure the rms of 10 cycles for 50Hz systems with an accuracy of ± 0.1%. The instrument should be connected for a week and measure at 10 minute intervals (BS EN 50160). The supply voltage shall be measured as outlined in BS EN50160 and be within the limits specified in the ESQCR (2002). This philosophy can be applied to other power quality limits in that measurement should be carried out as outlined in BS EN Type A Instrument A type A instrument must be used when challenging a customer s complaint or for providing recorded data to a customer or third party, either orally or written. A type A instrument should be used in preference to a type B instrument, when a type B instrument has indicated the limits are close to being or have just been breached. It is important that in these situations a high accuracy type A instrument is used Type B Instrument A type B instrument is the only instrument to be used for indicative purposes or troubleshooting only. Consideration must be given when interpreting the recorded data and the accuracy of the instrument before carrying out a solution. On no account must the recorded data be released to a customer or third party, either orally or written. It may be that in some cases the limits are breached, but the instrument shows them within limits and in other cases the opposite may apply Existing instruments CP290.doc Issue 1 05/01/04 DMT CP290 Page 12 of 15

17 7.5 Instrument accuracy Existing instruments that are outside the accuracy of a type A or B instrument may continue to be used until 1 st February Table 1 shows the variation of a voltage measurement at the upper and lower limits based on the accuracy of the measuring instrument. In situations where the supply voltage is around the voltage limits specified in the ESQCR (2002), then the actual voltage may be within the limits, but the instrument being used may record the voltage out of limits. This can result in unnecessary network reconfiguration or even network reinforcement and it is advisable to use a type A instrument (± 0.1%) in these cases. This philosophy can be applied to other power quality limits and measurements To verify compliance with power quality limits, once a solution has been implemented, further monitoring should be carried out by a type A instrument. Table 1: Voltage Measurement Instrument Accuracy Voltage limits (LV) -6% +10% 1% % % % % % % Instrument suppliers Any new power quality instrument purchased should be compared against either a type A or B instrument as detailed in BS EN and be able to carry out power quality measurements to BS EN The instrument type is dependent on the application as is detailed in section 6.2. Appendix B includes a list of power quality instrument manufacturers, but users should be aware that these instruments may be supplied to customers through third party electronic equipment suppliers. It should be noted that this is not a list of approved suppliers or an indication that the instruments they supply are either of type A or type B. It is the responsibility of the individual approving the purchase of an instrument or instruments to confirm compliance with the standards outlined. In addition, consideration should be given to the environment, downloading data (laptop or flashcard), interpretation and display of data (i.e. software, to BS EN501160) and service support. Assistance may be sought, if required, from the Power Quality & Development Manager, Policy and Standards, Asset Management. CP290.doc Issue 1 05/01/04 DMT CP290 Page 13 of 15

18 8. DOCUMENTS REFERENCED 8.1 The Electricity Safety, Quality and Continuity Regulations 2002 (ESQCR). 8.2 Electricity Distribution Licence. 8.3 The Distribution Code of Licensed Distribution Network Operators of Great Britain. 8.4 BS EN 50160: Voltage characteristics of public electricity distribution networks. 8.5 Engineering Recommendation P28: Planning limits for voltage fluctuations caused by industrial, commercial and domestic equipment in the United Kingdom. 8.6 Engineering Recommendation P29: Planning limits for voltage unbalance in the United Kingdom for 132kV and below. 8.7 Engineering Recommendation G5/4: Planning levels for harmonic voltage distortion and the connection of non-linear equipment to transmission and distribution systems in the United Kingdom. 8.8 HD472 S1: Nominal voltage, for low-voltage public electricity supply voltage. 8.9 BS EN Environment 8.10 BS EN : Compatibility levels for low frequency conducted disturbance and signalling in public low voltage power supply systems BS EN : Compatibility levels in industrial plant for low frequency conducted disturbances BS EN : Compatibility levels for low frequency conducted disturbances and signalling in public medium voltage power supply systems BS EN Limits 8.14 BS EN : Limits for harmonic current emission (equipment input current to and including 16A per phase) BS EN : Limitation of voltage changes, voltage fluctuations and flicker in public low voltage supply systems, for equipment with rated current <= 16A per phase and not subject to conditional connection BS IEC : Limitation of emissions of harmonic currents on low-voltage power supply systems for equipment with rated current greater than 16A IEC TR/ : Limitation of voltage changes, voltage fluctuations and flicker in public low voltage supply systems, for equipment with rated current greater than 16A per phase IEC/TR : Assessment of emission limits for distorting loads in MV and HV power systems BS EN : Limitation of voltage changes, voltage fluctuations and flicker In public low voltage supply systems, for equipment with rated current <= 75A per phase and not subject to conditional connection BS EN Testing and measurement techniques CP290.doc Issue 1 05/01/04 DMT CP290 Page 14 of 15

19 8.21 BS EN : Testing and measurement techniques General guide on harmonics and inter-harmonic measurements and instruments, for power supply systems and equipment connected thereto BS EN : Flickermeter Functional and design specifications Basic EMC publication BS EN : Testing and measurement techniques Power quality measurement methods BS EN Installation and mitigation guidelines BS EN Generic standards BS EN : Immunity for residential, commercial and light-industrial environments ETR 122: Guide to the application of engineering recommendation G5/4 planning levels for harmonic distortion and the connection of non-linear load to supply systems in the UK EPD 290: Power Quality. 9. KEYWORDS Compliance; ESQCR; Interruption; Licence; Measurement; Planning; System; Voltage CP290.doc Issue 1 05/01/04 DMT CP290 Page 15 of 15

20 APPENDIX A: SUMMARY OF ELEMENTS OF POWER QUALITY AND RELATING STANDARDS Elements of power quality Voltage Characteristics of electricity supplied by public distribution systems (BS EN 50160) Other relevant EN standards (Electromagnetic Compatibility) Regulations/Engineering Recommendations etc Measurement Standard Class Intervals Accuracy Range Frequency 50Hz ±1% for 99.5% of year 50Hz +4/-6 for 100% of time BS EN Hz, limits Hz, in exceptional circumstances could be 47-52Hz (Dist.Code), 50Hz ±1% (ESQCR) A BS EN B Man. Spec 10 sec ±0.01Hz Hz Man. Spec Hz Voltage Magnitude ±10% for 95% of week, 10 min (between +10/-15%) HD %/-6% LV, ±6% HV, ±10% for 132kV & above (ESQCR) A rms over 10 cycles BS EN B rms over period spec by Man. ±0.1% 0%- 200% ±0.5% 0%- 150% Voltage dips Retained Voltage: 90% to 1% Duration: 10ms 1 min. BS EN , BS EN , BS EN Reference to BS EN50160 (Dist. Code) BS EN A B Refer to BS EN Flicker Long term flicker severity 1 for 95% of time. BS EN (Pst <1 & Plt <0.65), BS EN (Pst <1 & Plt <0.65),BS EN Reference to P.28 (Dist. Code), P.28 Stage 2 Pst < 0.5, Stage 3 Pst <1 and Plt <0.8. BS EN A B BS EN None specified BS EN None specified 0-20 (Pst) None specified CP290.doc Issue 1 05/01/04 DMT CP290 Page A1 of 2

21 Harmonics 2 nd 2%, 3 rd 5%, 4 th 1%, 5 th 6%, 7 th 5%, 9 th 1.5%, 11 th 3.5%, 13 th 3%, 17 th 2%, 19 th & 23 rd 1.5%, (6 th,8 th,10 th,12 th,14 th,15 th,16 th,18 t h,20 th,21 st,22 nd &24 th all 0.5%) THD <= 8% (up to 40 th ) BS EN , BS EN , BS EN , BS EN , BS EN , BS EN Reference to G5/4 (Dist. Code) G5/4 400V THD 5%, 400V+ to 20kV THD 4%, 22kV to 400kV 3%. Percentage of harmonic voltage more stringent (increases higher the voltage) than EN50160 BS EN A B EN BS :2002, Class 1 Man. Spec EN BS :2002, Class 1 Man. Spec Twice values in BS EN , class 3 Man. Spec Interharmonics Level under consideration BS EN , BS EN , BS EN , BS EN , BS EN G5/4 Inter-harmonic frequency in Hz and Voltage distortion as %. <80Hz 0.2%, 80Hz 0.2%, 90Hz 0.5%, >90 & < % BS EN A EN BS :2002, Class 1 EN BS :2002, Class 1 Twice values in BS EN , class 3 B Man. Spec Man. Spec Man. Spec Interruptions Short duration : 3 min Long duration : > 3 min BS EN Short duration : 3 min Long duration : > 3 min (Ofgem) BS EN A B Refer to BS EN Voltage Unbalance 2% for 95% of 10 min rms of week, 3% in some areas BS EN , BS EN Reference to P.29 (Dist. Code) P.29 nominal levels of 1.3% up to 33kV and 1% 33kVto 132kV, short periods (1 minute) may reach 2% BS EN A B rms over 10 cycles, evaluated of sym. comps, see EN (±0.15% neg. and zero sequence) Man. Spec 0-5% CP290.doc Issue 1 05/01/04 DMT CP290 Page A2 of 2

22 APPENDIX B: POWER QUALITY INSTRUMENT SUPPLIERS Alpha Electronics Ametek Power Instruments AVO International Chauvin Arnoux UK Ltd Elcomponent Ltd Enercom Ltd Fluke (UK) Ltd IMH Technologies Ltd LEM HEME Ltd CP290.doc Issue 1 05/01/04 DMT CP290 Page B1 of 1