The easy way to build switchgear and controlgear assemblies in compliance with the regulations

Transcription

1 The easy way to build switchgear and controlgear assemblies in compliance with the regulations A guide for partially type-tested switchgear and controlgear assemblies in compliance with EN

2 What are the requirements? My name is Rocky, and I m looking forward to showing you the way through these guidelines. Contents Page EN is recognised as the established engineering practice for switchgear and controlgear assemblies 3 What are the bases of the agencies requirements? 4 Which control systems and installations are subject to EN ? 5 What is considered as a low-voltage switchgear and controlgear assembly - (ASSEMBLY) under EN ? 6 What is the difference between a TTA and a PTTA? 6 What does EN define? 8 Directives for the utilisation of other components as those applied for the type-test of a TTA permit a range of freedom 10 Type-tested components simplify work 10 The added value performed by the ASSEMBLY maufacturer requires safety verification 11 Calculation software simplifies verification of the temperature rise 12 Special care with short-circuit currents above 10 ka 12 Which tests must be performed on PTTA? 13 How can the expense for the technical verification of PTTA be minimised? 13 Important notes regarding national differences 13 Compilation of verifications and tests of TTA and PTTA 14 2 A Manufacturer s Declaration, a Type-testing Report and Routine Test Protocol are required as a safety verification.

3 Technical documentation must be available for review from the manufacturer. EN is recognised as the established engineering practice for switchgear and controlgear assemblies The legal requirements in the countries of the European Union (EU) and of the European Economic Area (EEA) require manufacturers and operators to ensure compliance with the established engineering practice in the construction and operation of electrical installations in order to ensure their safe operation. Existing standards are considered as established engineering practice and as the state of the art of technology. Compliance with these requirements is assumed when the applicable standards have been observed. For low-voltage switchgear and controlgear assemblies (ASSEMBLIES) the standard EN applies in the CENELEC area as the established engineering practice. Installations which are built and tested in compliance therewith are considered to be in compliance with the regulations. EN replaces earlier standards and reflects the technical progress which is expressed in higher rated currents, higher packing density, higher short-circuit withstand strength and an increased utilisation of electronic apparatus, among others. Low-voltage switchgear and controlgear assemblies are considered to be electrical equipment in the sense of the Low-voltage Directive and as apparatus in the sense of the EMC Directive of the EU. In accordance with this, a Declaration of Conformity is to be issued for them and they are to be identified with the CE-mark. The Declaration of Conformity must confirm that the ASSEMBLY complies with EN or exhibits an equal safety standard. The prerequisite for the Declaration of Conformity and the CE-marking is testing in accordance with EN and the preparation of compliant technical documentation. In accordance with the standard, a type-test and a routine test are to be performed and verified. The type-test report can refer either to a TTA (type-tested switchgear and controlgear assembly) which implies a complete type-test according to EN or to a PTTA (partially type-tested 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 tests. All technical documentation must be available from the manufacturer of the switchgear and controlgear assembly and it must be presented to the inspecting agencies for review on demand. It is beneficial that the routine test record be treated as a part of the scope of supply. The installation engineer must treat a switchgear and controlgear assembly as a product. He is responsible for the supply connections and their protection. The ratings of the ASSEMBLY must be provided on the nameplate or in the technical documentation of the manufacturer. For equipment and installations such as switchgear and controlgear assemblies which are subject to the Low-voltage Directive, it must be observed that the technical documentation has to be maintained within the Community for 10 years following the (last) manufacturing of the relevant product and that it is available to the national Agencies for review. In accordance with the rules of the national and local market-supervision agencies, the point in time and the cause for presentation of the verification documents may vary. 3

4 What are the bases of the agencies requirements? The requirements are based upon the Low-voltage Directive 73/23/EEC and the EMC Directive 89/336/EEC of the EU, as well as on their supplementation by Directive 93/68/EEC, which concerns the CE-marking. In its fundamental requirements, the Low-voltage Directive postulates the protection of persons, animals and property from the hazards and damage which may result from electrical apparatus. The EMC Directive states in Article 4: The apparatus referred to in Article 2 shall be so constructed that: a) the electromagnetic disturbance it generates does not exceed a level allowing radio and telecommunication equipment and other apparatus to operate as intended; b) the apparatus has an adequate level of intrinsic immunity of electromagnetic disturbance to enable it to operate as intended.... The central focus is on the protection of persons, animals and property as well as operation in the intended manner without malfunctions. 4

5 The EU Directives for low-voltage devices (73/23/EEC) and for Electromagnetic Compatibility (89/336/EEC) are valid in all countries of the European Union (EU) and of the European Economic Area (EEA) and in Switzerland ( Ordinance on electrical low-voltage equipment and Ordinance on electromagnetic compatibility ). Similar rules which are based to a great extent on the directives of the EU are valid or will soon be introduced in other countries, such as the Commonwealth of Independent States (CIS) or Australia. Which control systems and installations are subject to EN ? The standard cites (Subparagraph 1.1) - stationary or movable assemblies, - with or without enclosure, - for use in connection with generation, transmission, distribution and conversion of electric energy and for the control of electrical energy consuming equipment. EN does not apply to individual devices for which valid standards exist (motor starters in compliance with IEC 947, for instance). It follows from this that all electrical controls, distribution boards and switchgear and controlgear assemblies fall under EN It may not be concluded that EN is the sole standard to be applied. In the case of machine controls, for instance, additional requirements in compliance with EN (Electrical Equipment of Machines) must be fulfilled. 5

6 TTA are tested as a type and are frequently optimised for specific applications. PTTA consist of type-tested components, or such which are derived from them. What is considered as a low-voltage switchgear and controlgear assembly (ASSEMBLY) under EN ? 6 In accordance with EN , Subparagraph , a low-voltage switchgear and controlgear assembly is A combination of one or more low-voltage switching devices together with associated control, measuring, signalling, protective, regulating equipment, etc., completely assembled under the responsibility of the manufacturer with all the internal electrical and mechanical interconnections and structural parts ( ). Note 3 states: For various reasons, for example transport or production, certain steps of assembly may be made in a place outside the factory of the manufacturer. Thus, an ASSEMBLY is spoken of whenever low-voltage switching devices and protective and regulating equipment are involved. EN applies for ASSEMBLIES up to 1,000 volts a.c. and 1,500 volts d.c. What is the difference between a TTA and a PTTA? Type-tested low-voltage switchgear and controlgear assembly (TTA) EN Subparagraph : 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. A TTA is thus an ASSEMBLY which has been tested as a type (manner of construction) in compliance with EN Examples are LV distribution boards and Motor Control Centers (MCC). A worstcase configuration is tested (e.g. regarding temperature rise). TTA are designed for series production, whereby the individual TTA corresponds to the established type, but adapted to the specific application (e.g. number and performance of the outgoing circuits). TTA typically possess structural parts specific to the manufacturer such as plug-in modules, busbar systems, locking devices, etc., which are not available as universally-applicable components. TTA are typically applied with installations designed for control and distribution and with installations with high short-circuit current level. Partially type-tested low-voltage switchgear and controlgear assembly (PTTA) EN Subparagraph : 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 tests ( ).

7 PTTA are thus controls and installations which are not tested in their entirety as a type. They are compiled from components which are either type-tested (e.g. contactors, circuit breakers, load break switches, fuses etc.), or which are derived from type-tested arrangements (e.g. busbar system). The temperature rise, for example, can be derived (i.e. not measured), either - in accordance with HD 528 S2 (IEC 890; A method of temperature-rise assessment by extrapolation for partially type-tested assemblies (PTTA) of low-voltage switchgear and controlgear) or - with the aid of temperature-rise calculation software programs from enclosure manufacturers (which are based in turn on type-tests) or - based on similarity with previously manufactured (and measured) ASSEMBLIES. The essential difference between TTA and PTTA exists in the fact that TTA are optimised for specific (repetitious) applications and that, thanks to the measurement, it is possible to utilize the components to the limit of their load capacity. TTA are procured as complete installations from one manufacturer or built under his licence. In contrast to this, the PTTA construction method is typically selected by builders of switchgear and controlgear assemblies who opt for components from different manufacturers instead of the costly type-test and the commitment to one manufacturer. They derive the correct selection of the components for their specific application from the type-tests of the manufacturers and install them in accordance with the established engineering practice. This applies for single assemblies and also for series production. PTTA generally possess more reserve (e.g. with regard to temperature rise and the selection of the conductor cross sections), since the derivation is based on general rules (e.g. regarding the selection of conductors). TTA and PTTA are equal in regard to the fulfilment of safety requirements. 7

8 What does EN define? EN defines the design and construction requirements which must be fulfilled in order to achieve the safety objectives, the definitions which are significant for ASSEMBLIES, the referential environmental conditions, the test requirements, etc. EN thus represents an extremely useful set of instructions for the set-up and testing of ASSEMBLIES and forms a basis for communication between manufacturer, customer and agencies. The manufacturers and operators of ASSEMBLIES should become familiar with EN in order to meet their responsibility for the safety of the equipment. EN (Low-voltage switchgear and controlgear assemblies) is organised into the parts listed below: EN EN EN EN EN Part 1: Type-tested and partially type-tested assemblies. Part 2: Particular requirements for busbar trunking systems (busways) Part 3: Particular requirements for low-voltage switchgear and controlgear assemblies intended to be installed in places where unskilled persons have access for their use Distribution boards Part 4: Particular requirements for assemblies for construction sites (ACS) Part 5: Particular requirements for assemblies intended to be installed outdoors in public places Cable distribution cabinets (CDCs) for power distribution in networks There are supplements for some of these Parts which are integrated into the respective basic Part upon revisions of the standards. The following documents supplement EN for specific areas of technology: 8 HD 528 S2 (IEC 890) IEC 1117 A method of temperature-rise assessment by extrapolation for partially type-tested assemblies (PTTA) of low-voltage switchgear and controlgear. A method for assessing the short-circuit withstand strength of partially type-tested assemblies (PTTA)

9 The contents of EN , the fundamental part of the regulatory ordinance, are compiled below: 1. General 2. Definitions 3. Classification of ASSEMBLIES 4. Electrical characteristics of ASSEMBLIES 5. Information to be given regarding the ASSEMBLY 5.1 Nameplates 5.2 Markings 5.3 Instructions for installation, operation and maintenance 6. Service conditions 7. Design and construction 7.1 Mechanical design 7.2 Enclosure and degree of protection 7.3 Temperature rise 7.4 Protection against electric shock 7.5 Short-circuit protection and short-circuit withstand strength 7.6 Switching devices and components installed in ASSEMBLIES 7.7 Internal separation of ASSEMBLIES by barriers or partitions 7.8 Electrical connections inside an ASSEMBLY: bars and insulated conductors 7.9 Requirements for electronic equipment supply circuits 7.10 Electromagnetic compatibility 8. Test specifications 8.1 Classification of tests 8.2 Type-tests 8.3 Routine tests Annexes A (normative) Minimum and maximum cross-sections of copper conductors suitable for connection B (normative) Method of calculating the cross-sectional area of protective conductors with regard to thermal stresses due to currents of short duration C (informative) Typical examples of ASSEMBLIES D (informative) Typical arrangements of forms of separation by barriers or partitions E (informative) Items subject to agreement between manufacturer and user F (normative) Measurement of creepage distances and clearances G (normative) Correlation between the nominal voltage of the supply system and the rated impulse withstand voltage of the equipment H (informative) Bibliography ZA (normative) Other international publications cited in this standard with references to the relevant European publications 9

10 What must be observed in the and testing of a PTTA? Directives for the utilisation of other components as those applied for the type-test of a TTA permit a range of freedom EN states in Subparagraph 8.1.1: If modifications are made to the components of the ASSEMBLY, new type tests have to be carried out only in so far as such modifications are likely to adversely affect the results of these tests. This rule provides the manufacturer of a specific TTA a relatively wide range of freedom regarding the selection of the switchgear and other components. It is entirely feasible that devices other than those employed in the type-test may be installed without affecting the validity of the type-test, for example when: - the maximum temperature rise is not exceeded (e.g. through selection of devices of the same or lower power dissipation), - the insulation withstand strength is not lowered (e.g. through selection of devices of the same or better insulation), - the short-circuit withstand strength is maintained (e.g. through selection of circuit breakers with the same or higher breaking capacity and the same or more favourable let-through values). Type-tested components simplify work PTTA represent the majority of control systems or distribution boards in unit production. Observing established engineering practice, careful selection of products, and competent construction, the assembly of a control system which conforms to directives poses no problem and corresponds to the established practice of reliable switchboard manufacturers. The documentation of the component manufacturers are an essential support tool for project planners as well as the builders of ASSEMBLIES. In accordance with the Low-Voltage and the EMC Directive, all components must fulfil the relevant directives and be type-tested. The type-tests of the components are performed in compliance with the respective standards for the components (e.g. in compliance with EN for low-voltage switching devices) and not in compliance with EN (refer to EN Subparagraph 1.1: This standard does not apply to individual devices and self-contained components, such as motor starters, fuse switches, electronic equipment, etc., complying with their relevant standards ). The component manufacturers issue relevant Declarations of Conformity and identify the products for the EU with the CE-mark. The user of such type-tested components can assume that the relevant standards are fulfilled, provided that these components are installed in accordance with the manufacturer s specifications (those which form the basis of the type-test). This applies for the areas of the Low-voltage Directive as well as the EMC 10

11 construction, modification Directive. Among other things which deserve special attention are the manufacturer s specifications regarding load capacity with increased ambient temperature, the performance data for short-circuit stress, the safety distances from arcing apertures, etc. The job of the ASSEMBLY manufacturer is simplified if he can refer to type-tests or technical documentation from the component manufacturer for component subassemblies, as is the case with the MCS-Star provided by Rockwell Automation for motor starters of the Modular Control System (MCS). He is thus freed from the burden of selecting and dimensioning the components installed in the subassembly. The added value performed by the ASSEMBLY maufacturer requires safety verification While it is possible to rely upon the type-tests conducted for devices by the component manufacturer, the ASSEMBLY manufacturer bears the responsibility for work he has performed, such as selecting correctly-dimensioned conductors and their protection. Here, he can rely upon the relevant guidelines such as those set down in Harmonization Document HD , with consideration for the type of conductor, the temperature limit of the conductor insulation, the ambient temperature, the conductor loading and the method of installation. Which starter? Starter selection Helpful software tools such as MCS-Star produced by Rockwell Automation simplify the work of ASSEMBLY manufacturers. Circuit diagram Starter selection Catalog Nr. Function Star-Delta starter Mechanical locking Without mechanical locking Control type Short-circuit coordination Coordination Type "1" Control voltage V 50Hz 230V 50 / 60Hz V 50Hz 240V 50Hz / 277V 60Hz 170-C16NKF10-A1G-TY-E-X Motor protection Electrical motor protection relay, terminal 10 man. Current limiter Star-Delta time relay Electronic timer module, 30 seconds Assembly system Motor output at 400 /415 V 50 Hz 7.50 kw / 14.8 A 9.00 kw / 19.0 A 11.0 kw / 21.5 A 15.0 kw / 29.0 A Layout Assembly test Bills of Materials Circuit diagram Layout Project Terminate Circuit diagram Layout S00SEATX 11

12 Calculation software simplifies verification of the temperature rise Harmonization Document HD 528 S2 (IEC 890) applies as the established engineering practice for the determination of the temperature rise in the switchgear cabinet with natural cooling. Suppliers of enclosures and cabinets provide software for temperature-rise calculation based on proven calculation methods and which allow verification of temperature rise and any cooling measures required without undue outlays for the user. The project planner takes the power dissipation of the components from the catalogues or databases of the product manufacturers, while the software ensures the correct sizing. In the event that similar control units (e.g. same cabinet size with comparable power dissipation of the components in a similar construction) are built successively, the verification for temperature rise can also be derived from the observance of similarity with the first system whose temperature rise was either measured or calculated. Special care with short-circuit currents above 10 ka ensured that either the limits of 10 ka and 15 ka respectively are not exceeded, or that the installation possesses the necessary robustness at higher levels of short circuit current. It is advisable to rely upon type-tested components and arrangements, even for PTTA where busbars are involved. The selection and application of the busbar in compliance with manufacturer s specifications (based on his type-test) ensures a design that conforms to requirements. In addition, Technical Report IEC 1117 provides instructions for the design of PTTA which is resistant to short-circuits, especially regarding connection of the equipment. Current limiting circuit breakers can eliminate the necessity for verification of short-circuit withstand strength. 12 EN exempts testing of short-circuit withstand strength at rated short-circuit currents below 10 ka. Nor is verification of the short-circuit withstand strength required for protection with currentlimiting devices such as current-limiting fuses or circuit breakers when the let-through current does not exceed 15 ka at rated breaking capacity. As a result, significant costs for testing are eliminated for many control systems and installations. Short-circuit currents of 10 ka presuppose the direct connection to a transformer with an output of approx. 400 kva (at 400 V secondary voltage and 6% short-circuit voltage) and are rare with smaller loads. Because of the hazards of short circuits, extreme caution regarding the short-circuit withstand strength should be taken and it must be

13 Which tests must be performed on PTTA? Careful routine testing ensures the safety of the individual ASSEMBLY. Software for calculation of temperature rise and short-circuit current are helpful support tools. Table 7 of EN lists the tests which are to be performed on PTTA (and TTA). In the selection of type-tested components, or those derived from them, and for the execution of calculations in compliance with recognised methods, verification may be achieved without difficulties. It is recommended that standardised protocols are prepared for the documentation of the tests or whenever available that protocol forms made available by professional societies are used. How can the expense for the technical verification of PTTA be minimised? Together with the selection of type-tested components for which no further verification is required since reference may be made to the type-test of the respective manufacturer, it is recommended to standardise the internal bespoke documentation and procedures for the services of the planning engineer and builder of ASSEMBLIES and to incorporate these standards into a quality assurance system. Given careful work in compliance with these internal standards, technical verification for all installations assembled in compliance with them is guaranteed. With sizing for which either standards or industry-specific table references are available, for example, it is recommended that these be incorporated. It may be anticipated that industrial societies will support their members increasingly in the fulfilment of this task. Important notes regarding national differences The standards and Harmonization Documents referred to in this brochure are cited with the numbers and designations in accordance with CEN- ELEC or IEC. The numbers and designations may deviate in some countries because of national systems. However, the national standards are identical in their contents and cite the documents 13 which form the basis at the European level in all cases.

14 Compilation of verifications and tests of TTA and recommendations for the practical execution with Seq Requirements Section TTA no. to be tested 1 Limiting excess Verification of compliance temperature of limiting excess temperature by testing (type-test) 2 Insulation withstand Verification of the insulation strength withstand strength by testing (type-test) 3 Short-circuit Verification of short-circuit withstand withstand strength strength by testing (type-test) 4 Efficiency of the Verification of the proper connection protective conductor between conductive parts of the switchgear and controlgear Proper connection between assembly and protective conductors conductive parts of the by inspection or resistance measurement switchgear and controlgear (type-test) assembly and protective conductors Short-circuit withstand Verification of the short-circuit withstand strength of the protective strength of the protective conductor conductor by testing (type-test) 5 Creepage distances and Verification of the creepage clearances distances and clearances (type-test) 6 Mechanical Verification of the mechanical function function (type-test) 7 Type of protection Verification of the type of protection (type-test) Subparagraphs 8 to 11 are routine tests 8 Wiring, Visual inspection of the switchgear and electrical function controlgear assembly, including the wiring and electrical function test where required (routine test) 9 Insulation Insulation test (routine test) Protective measures Inspection of protective measures and visual inspection of the continuous protective conductor connection (routine test) 11 Leakage resistance

15 PTTA (Table 7 from EN ) supplemented with PTTA. PTTA Verification of compliance of limiting excess temperature by testing or extrapolation of TTA Verification of the insulation withstand strength in compliance with Section or verification by insulation test in compliance with Section or verification of the leakage resistance in compliance with Section (refer to Seq. no. 11) Verification of short-circuit withstand strength by testing or extrapolation of similar type-tested arrangements Verification of the proper connection between conductive parts of the switchgear and controlgear assembly and protective conductors by inspection or resistance measurement Comments for PTTA Determination in accordance with HD 528 S2 or with the use of temperature-rise calculation software from enclosure manufacturers The verification of the insulation resistance (measurement at 500 V) will be the easiest to conduct in most instances. Not required up to 10 ka (or 15 ka let-through current respectively). Beyond this, use of type-tested busbar systems recommended. Extrapolation in accordance with manufacturer's documents and execution in accordance with IEC Verification of the short-circuit withstand strength of the protective conductor by testing or corresponding execution and arrangement of the protective conductor (refer to Section , last paragraph) Verification of the creepage distances and clearances Verification of the mechanical function Verification of the type of protection For PTTA, separate protective conductors must be provided (protective connections via constructional parts are not allowed) in such a manner that the influence of the electromagnetic forces of the busbars may be ignored (i.e., at a distance from the busbars). Use of type-tested components and special attention to the clearances from enclosures and other conducting parts. Observance of arcing spaces. Especially for plug-in modules and locking devices. Occurs rarely with PTTA or is covered by the use of type-tested components. Use of suitable type-tested enclosures and installation components. Installation of components in the switchgear cabinet surface in compliance with instructions of the component manufacturer for the relevant type of protection. Visual inspection of the switchgear and controlgear assembly, including the wiring and electrical function test where required Insulation test or verification of the See note regarding Subparagraph 2 leakage resistance in compliance with Section (refer to Seq. no. 11) Inspection of protective measures Visual inspection of the protective conductor connections and random sample tests of the threaded connections. Verification of the leakage resistance, See note regarding Subparagraph 2 if the test was not conducted in compliance with Section or (refer to Seq. no. 2 and 9) 15

16 More Than Ways To Make Automation Work Power devices Sensors Operator interface Motion Control Logic devices Communication products Application systems Circuit breakers Motor contactors and starters Motor protection Motor Control centers Power monitoring Limit, photoelectric and proximity switches Pressure and temperature controls Radio frequency identification Bar code Encoders Vision systems Push buttons and pilot devices Cam switches Message displays Operator panels, terminals AC and DC drives Drive systems Computer numerical controls General purpose motion control Programmable controlers Universal I/O Control and information processing Relays Terminal blocks Automation control networks Multivendor connectivity (MAP) Custom engineered control systems Batch control Burner management systems Distributed discrete manufacturing control SCADA Stamping press control systems Quality management SPG/SQC data collection and analysis Global support services Technical training Field engineering and service Repair and exchange services Technical support Publication PTSK EN, March 1999 Copyright 1998 Rockwell International Corporation. All rights reserved. Printed in Switzerland