Dorman Smith PowerForm Low Voltage Factory Built Assemblies

Transcription

1 Dorman Smith PowerForm Low Voltage Factory Built Assemblies

2 Contents Introduction to the PowerForm Switchboard System 1 PowerForm Specification A Switchboard Specification A Switchboard Specification 6 Cast Resin Transformers 9 Packaged Substations 9 Loadline ACBs 10 Microprocessor Based Overcurrent Releases 10 Loadline HP Circuit Breakers 11 Loadswitch Fused Devices 11 Switchboard Standards 12 Dorman Smith Switchgear Introduction Continuous product development including new uprated specifications have provided the opportunity for Dorman Smith to update their low voltage factory built assembly range. This publication gives detailed information on Dorman Smith s extensive range of low voltage factory built assemblies and is intended to assist the design engineer and installer in the selection of equipment to meet today's stringent specifications. Dorman Smith's world class manufacturing facilities are dedicated to answering the individual needs of customers using the company's own unique refinement of Just In Time techniques to achieve total manufacturing flexibility. Such is the efficiency of the Dorman Smith UK plant, it won a Britain s Best factory award, and has been chosen by the DTI as a manufacturing reference plant for the UK and was also the subject of an Open University video on manufacturing. Dorman Smith's ability to design and manufacture reliable, durable products and to give advice on complex electrical circuit protection, has firmly established a Worldwide reputation for high quality and expertise. Located in Preston, Lancashire, Dorman Smith occupies a purpose built site totalling 19,000m 2 and is one of Britain s largest and most well respected manufacturers of low voltage switchgear, systems and associated distribution equipment. In addition, there are also manufacturing plants in Dubai and Riyadh, which service the Middle East markets. 31 EN :1999 (IEC :1999) Switchboard Standard 12 Internal Separation of Assemblies 14 UK National Annex Table NA1 16 Forms of Separation 17 Form Degrees of Protection 19 EN60529:1991 (IEC :1989) Degrees of Protection 19 Energy Management 20 Power Factor Correction 20

3 PowerForm Specification PowerForm Specification Certification The PowerForm Switchboard System has been fully tested and ASTA certified. Standards PowerForm is a fully type tested switchboard fully complying with IEC :1999 EN :1999 BSEN :1999 Mechanical Characteristics Degree of protection to EN (IEC 60529) is minimum IP3X with higher protection available. Internal degree of protection exceeds IP2X Functional unit interconnections PVC insulated All doors manufactured from 1.6mm steel and hinged All rigid busbar partitions made from perforated 1.5mm steel Frame Steel pre-treatment involves iron phosphate process for degreasing Paint finish in (Light Grey) Powder Coated polyester, colour RAL 7035 Standard frames available are as shown below Frame Widths (mm) Range Cable Access Steel (mm) Height (mm) PowerForm 25 Front Rear PowerForm 63 Rear A Busbar System Max Horizontal Phase Busbar Max Horizontal Neutral Busbar Max Vertical Phase and Neutral Busbar Max Short Time Current Busbars Max Peak Current 6300A Busbar System 2500A 2500A 1600A 50kA - 3 secs 105kA Rated voltage 415V a.c. Rated insulation voltage 690V a.c. Dielectric test voltage 2.5kV Nominal frequency 50 Hz Fully ASTA certified Busbar System Busbar Ratings A A A A A Busbar supports are flame retardant and high temperature glass reinforced. Rated voltage 415V a.c. Rated insulation voltage 690V a.c. Dielectric test voltage 2.5kV Nominal frequency 50 Hz Fully ASTA certified Busbar System Busbar Ratings A A A A Busbar supports are flame retardant and high temperature glass reinforced. Max Horizontal Phase Busbar 6300A Max Horizontal Neutral Busbar 10,000A Max Vertical Phase and Neutral Busbar 1600A Max Short Time Current Busbars 100kA - 1 sec Max Peak Current 220kA

4 A Switchboard Specification 2500A Switchboard Specification 25 4 PowerForm 25 Constructional Details Typical Arrangements 1. Typical arrangement 2500A busbar system 2500A, 50kA/3sec Busbars 5 Loadline HP changeover MCCBs Front access cabling High performance Loadline HP outgoing MCCBs 2. Typical Controlgear Compartment 1 Horizontal Busbar Positions 2

5 A Switchboard Specification 6300A Switchboard Specification 63 6 PowerForm 25 Constructional Details PowerForm 63 Constructional Details Typical Arrangements 3. Typical arrangement 6300A busbar system 6300A 100kA/1sec Busbars. 7 Selective forced air cooling to: - Busbars. - ACB Enclosure. 4 Pole withdrawable ACBs. Rear access cabling. High performance Loadline HP outgoing MCCBs. 4. Internal view showing 6300A Busbar Connections. 800mm Main Cubicle. 500mm or 800mm Cable Access Way. 5. View showing special Busbar arrangements 3 Horizontal Busbar Positions 4 5

6 A Switchboard Specification Packaged Substations 8 Special Arrangements 6. Insulated busbar components Certain essential installations may require insulated Busbars within the Busbar enclosure to ensure resilience of supply. To comply with this Dorman Smith can offer a totally insulated system. To comply with EN (IEC ) Form 4, UK Annex Types 1 and 4, the Busbar separation is achieved using insulated coverings. 6300A Busbar fully insulated. Joints also insulated using shrouds. Insulation by means of a durable polymeric coating. Cast-Resin Transformers IEC 726 Advantages and characteristics of cast-resin transformers. Excellent antipollution features and maximum safety All constructive materials and especially the insulating resin are self-extinguishing: they do not develop, in case of fire, toxic gases and they are moisture tolerant. Performances Cast-resin transformers are the best solution for all technical installation problems, thanks to their capability to withstand network impulsive voltage peaks,dynamic short-circuit, and overloads, with the optional addition of cooling fans for increasing rated capacity. Maintenance-free The high stability of the physical characteristics of the materials and the state-of-the-art technology reduce maintenance to the minimum. Where can cast-resin transformers be used? The electrical and physical properties of cast-resin transformers fit them for both civil and industrial use: hospitals, theatres, airports, subway, mines, off-shores platforms, nuclear power plants, vessels, industrial plants, etc. That is to say wherever there are fire or environmental pollution risks and where safety is a must. Maximum reliability The product offers the maximum reliability thanks to the computerised control of thermal processes, to the check of the chemical and the physical characteristics and to the measuring of the TG (Glasstransition) temperature of resin. Economy of installation Elimination of sumps for oil collection, reduced overall dimensions and an excellent distribution of weights allow cost reduction of the plant Fan assisted cooling system To assist with cooling, high current switchboards, an option is to force air cool the internal components. Packaged Substations Fan will cool ACBs. Also can cool Busbars. Air flow adjusted to suit final temperature requirements. Thermostatically controlled. Main and standby options. 7

7 LV Protective Devices LV Protective Devices 10 Loadline ACBs Loadline Air Circuit Breakers and their accessories conform to the International Standards IEC 947, EN (harmonised in the 17 CENELEC countries), CEI EN and IEC 1000, and conform to the relevant CE directives: Low Voltage Directives (LVD) No. 73/23EEC Electromagnetic compatibility Directive (EMC) No. 89/336EEC The apparatus complies with the specifications of the regulations for on-board installations and is approved by the following Naval Registers: RINA (Italian Naval Register) Det Norske Veritas Bureau Veritas Germanischer Lloyd Lloyd s Register of Shipping Polskj Reiestr Statkow The constant increase in the technological and functional complexity of electrical installations makes it essential for every component - particularly those such as protection circuit breakers which are crucial to safety - to offer the highest levels of continuity of service and reliability combined with minimal maintenance requirements. Loadline Air Circuit Breakers were designed in line with the advanced plant engineering requirements, and features high resistance to mechanical, electrical and thermal stresses. Loadline Air Circuit Breakers represent the logical functional complement to the Loadline HP moulded case circuit breakers and have, like them, been designed for integration and perfect co-ordination with the different lines of low voltage products. Loadline Air Circuit Breakers are available in five different models: E1, E2, E3, E4 and E6, each of which benefits from the interchangeability of the various different versions of moving parts (with different breaking and rated current capacities) for the same fixed part. The rated uninterrupted currents range from 800 to 6300 A. The breaking capacities range from 40kA to 150kA (380/415 V a.c.). Loadline High Performance MCCBs Loadline HP circuit breakers and their accessories conform to the International Standards IEC 947-2, EN (harmonised in the 17 CENELEC countries), CEI EN and IEC 1000, while also conforming to the following EC directives: Low Voltage Directives (LVD) No. 73/23 EEC Electromagnetic Compatibility Directive (EMC) No. 89/336 EEC Loadline HP S4, S5, S6 and SX7 circuit breakers for alternating current protection can be fitted with overcurrent releases PR211/P and PR212/P featuring mircoprocessorbased electronic technology. This makes it possible to obtain protection functions which ensure high reliability, precise tripping and immunity to the influence of ambient conditions. The power supply required for correct operation is supplied directly by the releases s current transformers with one phase current 15% of their rated curents, even with only one phase powered. Just one adjustment is required for all the phases and neutral, and tripping of the release is simultaneous for all the poles of the circuit breaker with operating characteristics that are unaffected by ambients conditions. Operation of the release can be checked using a TT1 portable test device powered using normal batteries. 11 Microprocessor Based Overcurrent Releases Loadswitch Fuse Combination Protection PR111 PR112 Functions L S I G Overload protection with inverse long time-delay trip Selective short-circuit protection with inverse or definite short time delay Instantanious short circuit protection with adjustable trip current setting Earth Fault Protection RESIDUAL SOURCE GROUND RETURN The circuit breakers fitted with microprocessor-based releases offer load control, self-test and information transmission capabilities in addition to the traditional protection functions, enabling them to be interfaced with centralised control and supervision systems. Loadline offers all the components needed to build systems that are tailored to each installation, from field units to front ends (with standard communication protocols), from actuators to control systems. As a result, the work of specifiers and designers is considerably simplified when it comes to choosing the technical characteristics and performance required. All this is thanks to the fact that the selection criteria are common to both families of circuit breakers and use intuitive and easy-to-read codes and symbols. The new circuit breakers continue a tradition of switchear designed and manufactured paying particular attention to use and user interfacerelated aspects, with obvious advantages in terms of ergonomics, clarity and speed of identification. Loadswitch fuse Combination conform to EN (IEC ). 80kA RMS Fused Short Circuit Current 415V ac Rated Voltage Current ratings 32A to 800A 80kA RMS Fused Short-Circuit Current AC23A Utilisation Category Loadswitch has been designed to exceed the requirements of EN (IEC ) and to offer solutions demanded by our customers where ease of installations and ever increasing cable sizes are required. A full uninterrupted duty ensures that the unit can maintain full rated load indefinitely. A utilisation category of AC23A and short-circuit capacity of 80KA enables Loadswitch to be installed with confidence on any inductive or resistive load. The door handle can be padlocked off as standard. Up to three padlocks can be attached with ease. Thermal memory for functions L and S

8 Switchboard Standards Switchboard Standards 12 Introduction EN :1999 Fundamentals of Separation This International Standard applies to low voltage switchgear and controlgear assemblies (type-tested assemblies (TTA) and partially typetested assemblies (PTTA)), the rated voltage of which does not exceed 1000 V a.c. at frequencies not exceeding 1000Hz, or 1500V d.c. This standard applies to assemblies intended for use in connection with the generation transmission, distribution and conversion of electric energy, and for the control of electric energy consuming equipment. The object of this standard is to lay down the definitions and to state the service conditions, construction requirements, technical characteristics and tests for lowvoltage switchgear and controlgear assemblies. Type Tested Assemblies (TTA) Section Section A low voltage switchgear and controlgear assembly conforming to an established type or system without deviations likely to significantly influence the performance, from the typical assembly verified to be in accordance with this standard. Partially Type Tested Assemblies (PTTA) Section Section A low voltage switchgear and controlgear assembly, containing both type-tested and non-type-tested arrangements, provided that the latter are derived (e.g. by calculation) from type-tested arrangements which have complied with the relevant test. In accordance with the Standard, separation of the various elements of an Assembly: busbars, functional units, terminals, can be claimed providing one or more of the following criteria are met: 1. Protection against contact with live parts belonging to adjacent functional units. The degree of protection shall be at least IP2X or IPXXB. As a minimum, finger contact with live parts in adjacent functional units is prevented. With Assemblies supplied by Dorman Smith Switchgear this is extended to include protection against finger contact between: functional units, adjacent busbars and busbar connections, and terminals as required for the particular form of separation being considered. The requirement is proven with the standard test finger. Typical Applications Form 1 - No separation Typical applications are places where the switchboard is in a secure location and where failure of the switchboard will cause little or no additional disruption to other areas being fed by the switchboard. Form 2 - Separation of busbars from functional units. Applications may well be the same as Form 1 but where it is important that a fault in the switchboard need not affect all functional units being fed from the same busbar system. 2. Protection against the passage of solid foreign bodies from one unit of an Assembly to an adjacent unit. The degree of protection shall be at least IP2X. The minimum requirement is proven by the standard test finger not being able to touch live parts in adjacent units and a 12mm ball not being able to pass between units. In practice a higher degree of protection may be required for horizontal partitions to prevent small objects form falling between compartments and should be identified in the contract specification. These two fundamental criteria are interrelated. Dorman Smith Switchgear will therefore ensure all these are fully met in respect of the particular form of separation offered. Form 3 - Separation of busbars from functional units and the functional units from one another but not their terminations. Should be applied where it is important to provide protection from internal live parts and where failure of functional units being fed from the same busbar would cause unacceptable disruption. Form 4 - Separation of busbars from functional units and the functional units from one another including their terminations. Should be applied where it is important to provide protection from internal live parts and where failure of functional units being fed from the same busbar would cause unacceptable disruption. Because all the terminations are separated it is possible to isolate and work on a single functional unit. 13 Methods of Construction Type Tests Section 8.2 Section 8 Type tests include the following: a) verification of temperature-rise limits (8.2.1): b) verification of the dielectric properties (8.2.2); c) verification of the short-circuit withstand strength (8.2.3); d) verification of the effectiveness of the protective circuit (8.2.4); e) verification of clearances and creepage distances (8.2.5); f) verification of mechanical operation (8.2.6); g) verification of the degree of protection (8.2.7). Dorman Smith have considerable experience in designing and constructing low voltage switchboard assemblies from the simplest panelboard to the most complex multi-cubicle control and distribution switchboard including HV/LV transformer to provide a packaged substation. The various methods of separation and construction offered by Dorman Smith from Form I through to Form 4 are illustrated in detail on pages can be seen from these diagrams a modular approach has been employed which enables the maximum number of permutations to be achieved within a highly cost effective frame work. If you would like more information on Dorman Smith Low Voltage Switchgear Systems our technical Sales Team will be pleased to assist and can upon request organise educational seminars and training for your staff on EN I and the UK National Annex.

9 Switchboard Specification Switchboard Specification 14 Internal Separation of Assemblies Section 7.7 Symbols used in Diagrams Barrier Terminal Device Busbar Form 3a Separation of busbars from the functional units and separation of all functional units from one another. Separations of the terminals for external conductors from the functional units, but not from each other. 15 Form 1 Terminals for external conductors not separated from busbars. No Separation. Form 3b Separation of busbars from the functional units and separation of all functional units from one another. Separations of the terminals for external conductors from the functional units, but not from each other. Terminals for external conductors separated from busbars. Form 2a Form 4a Separation of busbars from the functional. Terminals for external conductors not separated from busbars. Separation of busbars from the functional units and separation of all functional units from one another, including the terminals for external conductors which are an integral part of the functional unit. Terminals for external conductors in the same compartment as the associated functional unit Form 2b Form 4b Separation of busbars from the functional. Terminals for external conductors separated from busbars. Separation of busbars from the functional units and separation of all functional units from one another, including the terminals for external conductors which are an integral part of the functional unit Terminals for external conductors not in the same compartment as the associated functional unit, but in individual, separate, enclosed protected spaces or compartments.

10 Switchboard Standards Switchboard Standards 16 UK National Annex The internal separation of Assemblies by barriers or partitions is specified in 7.7 and is subject to agreement between the manufacturer and the user. Table NA.1 gives additional information regarding different types of construction, based on typical practice in the United Kingdom. Other types of construction are not precluded, and it is not essential to adopt any of the listed types in order to comply with the requirements of the Standard. Table NA.1 However, in order to achieve agreement between manufacturers and users, it is recommended to adopt one of the listed types of construction. Form 2b Type 2 Internal Separation of Assemblies Section 7.7 Unit 17 Forms of Separation Table NA.1 Main criteria Sub criteria Form Type of Construction No separation Form 1 Separation of busbars from the functional units. Separation of busbars from the functional units and separation of all functional units from one another. Separation of the terminals for external conductors from the functional units, but not from each other. Terminals for external conductors not separated from busbars. Terminals for external conductors separated from busbars. Terminals for external conductors not separated from busbars. Terminals for external conductors separated from busbars. Form 2 Form 3a Form 3b Type 1 Type 2 Type 1 Type 2 Busbar separation is achieved by insulated covering, e.g. sleeving, wrapping or coatings Busbar separation is by metallic or non-metallic rigid barriers or partition. Busbar separation is achieved by insulated coverings, e.g. sleeving, wrapping or coatings Busbar separation is by metallic or non-metallic rigid barriers or partitions. Form 3b Type 2 Internal Separation of Assemblies Section 7.7 Unit Separation of busbars from the functional units and separation of all functional units from one another, including the terminals for external conductors which are an integral part of the functional unit. Terminals for external conductors in the same compartment as the associated functional unit. Terminals for external conductors not in the same compartment as associated functional unit, but in individual, separate, enclosed protected spaces or compartments. Form 4a Type 1 Type 2 Type 3 Type 4 Type 5 Type 6 Type 7 Busbar separation is achieved by insulated coverings, e.g. sleeving, wrapping or coatings. may be glanded elsewhere. Busbar separation is by metallic or non-metallic rigid barriers or partitions. may be glanded elsewhere. Bushbar separation is by metallic or non-metallic rigid barriers or partitions. The termination for each functional unit has its own integral glanding facility. Busbar separation is achieved by insulated coverings, e.g. sleeving, wrapping or coatings. may be glanded elsewhere. Busbar separation is by metallic or non-metallic rigid barriers or partitions. Terminals may be separated by insulated coverings and glanded in common cabling chamber(s). All separation requirements are by metallic or non-metallic rigid barriers or partitions. are glanded in common cabling chamber(s). All separation requirements are by metallic or non-metallic rigid barriers or partitions. The termination for each functional unit has its own integral glanding facility. Cable Form 4a Type 2 Internal Separation of Assemblies Section 7.7 Unit Cable

11 IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII Switchboard Standards Degrees of Protection 18 Form 4b Type 5 Internal Separation of Assemblies Section 7.7 Unit EN : 1991 EN : 1991 describes a system for classifying degrees of protection provided by enclosures of electrical equipment with a rated voltage not exceeding 1000V ac and 1500V dc. The markings used to indicate the degree of protection consist of the letter IP (Ingress Protection) followed by two characteristic numerals. The first characteristic numeral designates the degree of protection with regards to solid objects. The second numeral designates the degree of protection against the ingress of liquid. It is intended to provide indication of: a) Protection of persons against access to hazardous parts inside enclosures and protection of the equipment inside the enclosure against the ingress of solid foreign objects. b) Protection of the equipment inside the enclosure against harmful ingress of water. 19 First Number - Protection Against Solids Second Number - Protection Against Liquids Cable Protection of persons Protection against solid against access to IP Example foreign objects - Tests hazardous parts with: 0 No protection. non-protected Protection against IP Example Liquids - Tests Protection from water 0 No protection No protection Form 4b Type 6 Internal Separation of Assemblies Section 7.7 Unit Cable for future use Form 4b Type 7 Internal Separation of Assemblies Section 7.7 Compartment Full penetration of 50mm diameter sphere allowed. Contact with hazardous parts not permitted. Full penetration of 12.5mm diameter sphere not allowed. The jointed test finger shall have adequate clearance from hazardous parts. The access probe of 2.5mm diameter shall not penetrate. The access probe of 1.0mm diameter shall not penetrate. Limited ingress of dust permitted (no harmful deposit). Totally protected against ingress of dust. back of hand finger tool wire wire wire cm min. Protection against vertically falling drops of water. Protection against vertically falling drops of water with enclosure tilted 15 from the vertical. Protection against sprays to 60 from the vertical - limited ingress permitted. Protection against water splashed from all directions - limited ingress permitted. Protected against low pressure jets of water from all directions - limited ingress permitted. Protected against strong jets of water, eg. for use on shipdecks limited ingress permitted. Protected against the effects of immersion between 15cm and 1m. Protected against long periods of immersion under pressure. Protection against vertically falling drops of water. dripping up to 15 from the vertical limited spraying splashing from all directions hosing jets from all directions strong hosing jets from all directions temporary immersion continuous immersion EN : 1991 Unit For switchboard assemblies intended for indoor use EN : 1999 states that there is no requirement for protection against ingress of water (clause ) and that the IP references preferred for assemblies designated for indoor use are: IP00 IP2X IP3X IP4X IP5X Where some degree of protection against ingress of water is required the following table gives the preferred IP combination numbers:- List of Preferred IP References Compartment for future use Cable First Characteristic Numeral Protection against contact and protection against ingress of solid foreign Second Characteristic Numeral Protection against harmful ingress of water IP21 IP31 IP32 IP42 IP43 IP53 IP54 IP55 IP64 IP65

12 Energy Management Energy Management 20 Power Factor Correction Introduction Harmonics Introduction 21 Electrical installation sizing must be carried out according to the apparent power S which, defined as the product of the voltage and the current (V x I) is expressed in [VA]. When there are ohmic loads, the apparent absorbed power is utilised completely as active power and is dissipated in heat, whereas when there are other loads, such as motors. welders, fluorescent lamps. transformers. etc., a part of the apparent absorbed power, called reactive power Q, is utilised only to energise the magnetic circuits. It cannot therefore be used as active power to carry out work. Types of Power Factor Correction Distributed power factor correction Distributed power factor correction is, in fact, the best technical solution since capacitor and user equipment follow exactly the same path during daily service of loads, so the cosφ setting becomes automatic and systematic. Apart from this, with local power factor correction it is not only the supply authority which benefits from reactive energy saving, but also the whole internal distribution system of the user. ln industrial installations, for example, the saving which can be made with distributed power factor correction, is not just a question of tariffs, but is also noted in sizing all the MV/LV substations with the The ratio between the active power and the apparent power expresses the power factor (cosφ) or the dephasing between voltage and current when the user absorbs reactive power. The power factor is equal to 1 when all the apparent absorbed power is active, whereas it is less than 1 when the apparent absorbed power consists of partly active power and partly reactive power. This means that user equipment with a low power factor requires more apparent power from the network (and therefore more current) than a corrected loads Another advantage with regard to distributed power factor correction, is its simple and cost-effective installation since the capacitor and load are connected and disconnected simultaneously and can use the same protections against overloads arid short-circuits. Centralised power factor correction Centralised power factor correction is cost-effective in the case of installations with several heterogenous loads operating on an occasional basis, so there is high installed power and fairly Iow average energy absorption by loads in simultaneous service. With centralised power factor correction, the bank power is notably less than the user with a higher power factor. Therefore the voltage drops and energy losses are higher, the lower the power factor. To keep down voltage drops and power losses it is therefore necessary to size the installations considering the higher current due to the low power factor, and this is to the detriment of the installation s costeffectiveness. For these reasons, companies supplying electrical energy increase the price of electricity for users with a low power factor. overall power which would be required for distributed power factor correction, taking into account, too, that the kvar cost of a high-powered capacitor is less than that of small capacitors. The bank can be connected permanently only if the reactive energy absorption is fairly regular during the day, otherwise it must be switched to prevent having cosφ in advance. When the reactive power absorption is highly variable during operation of the installation, automatic regulation is required with the bank split up into several steps. Manufacturers are increasingly being asked to provide for oversized neutral capabilities in their products. This is to cater for all anticipated increased current in the neutral system. The increased current is a result of harmonics being introduced onto the system, by modern day equipment such as, variable speed drives, static Recommendations Obtain information about the harmonic current for all equipment to be installed; Consider the effect of source impedance of ups and standby generator systems - they can be much higher than the impedance of the main transformer and cause more severe voltage distortion; Eliminate the source of harmonics by specifying low harmonic versions of switch mode power supplies, variable speed drives and high frequency ballasts; The Effects of Harmonics The effects of harmonic voltages are malfunctions in sensitive equipment such as the sensing circuits of circuit breakers and ups switches. The effects of harmonic current are overheating in conductors, transformers, motor coils and capacitors. When harmonic loaded single phase circuits on different phases are brought together in a distribution board, the third harmonic components and all the odd rectifiers, microwave ovens, personal computers, etc. This can result in severe overheating e.g. in cabies, busbar, enclosures, transformer coils, etc. Therefore, Industry, commercial premises, offices and homes, may all be affected, and with the growth of use of such equipment, the problem will escalate. Calculate the harmonic voltage and current at critical parts of the system, phase and neutral conductors; Design the installation, including proper sizing of neutral conductors, to accommodate harmonic currents where they occur; Separate circuits supplying harmonic generating loads from those supplying loads which are sensitive to harmonics; multiples (triplen harmonics) add together in the neutral. In severe cases the neutral current can exceed twice the phase currents. In such cases a double size neutral busbar is often specified. However, it may be necessary to double rate busbar and circuit breakers in the main distribution board as well. In a large installation the main circuit breaker could be rated at 4000 A. Finding an acb to take an 8000A neutral conductor can be difficult. BSRIA (Building Services Research Association) has been working with the industry to find the extent and severity of power quality problems related to harmonic currents. It has found widespread problems and believes that unless designers and operators are more aware of the problems, and take action to avoid them, they will become critical. Specify transformers and filters to remove harmonics; Follow guidelines for identification of harmonic problems including surveys, measurement methods and diagnosis; Safety considerations are paramount and the correct choice of instruments is also emphasised so that they will measure harmonic frequencies. Fortunately, diversity of the harmonic loads leads to a certain amount of cancellation since the harmonic currents of different loads are rarely in perfect phase. The solution may require modelling software to predict the neutral current. A range of solutions is available, from U.P.S. to avoid interruptions, through isoiating and phase shift transformers to passive and active filters.

13 All of the above information, including drawings, illustrations and graphic designs, reflects our present understanding and is to the best of our knowledge and belief correct and reliable. Users, however, should independently evaluate the suitability of each product for the desired application. Under no circumstances does this constitute an assurance of any particular quality or performance. Such an assurance is only provided in the context of our product specifications or explicit contractual arrangements. Our liability for these products is set forth in our standard terms and conditions of sale. ALR, AMP, Dorman Smith, Dulmison, Hellstern, Raychem, and SIMEL are trademarks of Tyco International Ltd. Argentina Phone: Fax: Australia Phone: Fax: Brazil Phone: Fax: Canada Phone: Fax: France Phone: Fax: Mexico Phone: Fax: Thailand Phone: Fax: United States of America Phone: Fax: Tyco Electronics EPP /01 Dorman Smith Switchgear Ltd Energy Division Blackpool Road, Preston, PR2 2DQ, UK Phone: Fax: Tyco Electronics Raychem GmbH Energy Division Haidgraben 6, Ottobrunn/Munich, Germany Phone: , Fax: