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L V Distribution Switchgear - Package Substations - Control Panels

IEC 61439 OVERVIEW

Verification of Low Voltage

Power Switchgear and Controlgear

Assemblies (PSC-Assemblies)

Prepared by Mike Harris - Technical Director

CONCLUSIONThe introduction of IEC 61439 and ultimately BS EN 61439 (February 2012), gives a defined route for both manufacturers, specifiers and customers to determine a solution for all PSC-Assemblies whether standard or bespoke that enables equipment to be designed and manufactured at an acceptable cost with guaranteed performance.Low voltage PSC-Assemblies, by nature of their application, may be installed for many years before they are called upon to operate close to the limit of their intended capability, for example, under planned expansion or fault conditions. As a result, any marginal performance may not be immediately evident.With a verified PSC-Assembly concerns of this nature are eliminated. The design is proven through a comprehensive design verification process which includes tests or other equivalent means. (See Table 2). Where methods other than test are used, de-rating factors are included to ensure the specified performance is achieved. This is essential assurance for user confidence.PSC-Assemblies fully meeting IEC 61439-2 ensures compliance with the Low-voltage Directive (LVD) and EMC Directives, and allows them to be CE marked.

TABLE 2:VERIFICATION METHODS COMPARED TESTINGTesting is still the best method of verification of compliance. Tests are valid either if performed by independent test establishments or by manufacturers following approved procedures. This will be the method by which manufacturers optimise their products, to minimise cabinet sizes etc, without affecting performance, reliability or safety. For standardised assemblies, testing offers the comfort of proven compliance for both the manufacturer and the end user, however, not all bespoke assemblies can be tested, as the costs are prohibitive. Other verification methods, as detailed below, can be utilised for these bespoke assemblies.

CALCULATION Calculations can, where permitted, be made to predict performance using established conventions. This method has the drawback of de-rating all published performance parameters and additional allowances for parameters such as temperature rise, to ensure the desired performance, reliability and security when operating at maximum load. For example, if a manufacturer has not conducted tests to demonstrate that a 250A MCCB in a specific compartment size meets the temperature rise limits, then the manufacturer can only rate the 250A device, in that compartment size, at 80% of it’s frame rating, i.e. 200A.This normally results in increased component ratings and enclosure sizes but in no way compromises performance, although plant room space utilisation factors are degraded and costs increased. AF Switchgear have conducted in-house temperature rise tests on all MCCB’s and ACB’s in standardised compartment sizes, so do not have to de-rate their equipment.

DESIGN RULESWhere permitted, this enables manufacturers to use data verified by testing to establish parameters for variants from the configuration tested. This can be the replacement of functional units from other manufacturers, where their performance values are equal or superior to the replaced units, or by units of a different rating within the same enclosure, using suppliers published data to calculate conformity. The manufacturer of the PSC-Assembly must however consider all performance parameters for each replacement unit.

NEW STANDARD TITLE PREVIOUS STANDARD

IEC 61439-0 Specifiers guide -

IEC 61439-1 General rules IEC 60439-1

IEC 61439-2 Power switchgear and controlgear assemblies

IEC 60439-1

IEC 61439-3 Distribution boards IEC 60439-3

IEC 61439-4 Assemblies for construction sites IEC 60439-4

IEC 61439-5 Assemblies for power distribution in public networks

IEC 60439-5

IEC 61439-6 Busbar trunking systems IEC 60439-2

TABLE 3: COEXISTENCE OF IEC 60439 WITH IEC 61439 SERIES

Only IEC 61439-1 (General Rules) and IEC 61439-2 (PSC-Assemblies) have been published at the outset. New standards for Busbar Trunking, Distribution Boards etc are under consideration, and relevant sections within IEC 60439 will remain valid for these items, until the publication of the appropriate standard within IEC 61439.

The table gives the comparison of the new and previous standards.

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PHOTO 1: CORROSION TEST TO IEC 61439 CLAUSE 10.2.2

INTRODUCTIONLV Switchgear in the UK is predominantly specified, designed and tested to BS EN 60439-1.BS EN 60439-1 only differs from IEC 60439-1 in that an informative National Annex is included, detailing typical Forms of Separation practices in the UK.In January 2009, IEC 60439 was superseded by IEC 61439 and this standard can now be used to specify new LV switchgear and controlgear, but as yet, the British Standard equivalent, BS EN 61439, has not been ratified, so BS EN 60439 is still current.Specifiers therefore currently have a choice, either continue to specify to BS EN 60439 and wait until it is superseded by BS EN 61439, which is now not likely until February 2012, or specify to IEC 61439 and benefit from the advantages and comfort that this new standard provides.This overview focuses on the advantages of the verification processes included in the new standard.

Characteristic to be verifiedIEC 61439-1Clauses or sub clauses

Verification options available

Testing Calculation Design rules

Strength of material and parts:Resistance to corrosionProperties of insulating materials:Thermal stabilityResistance of insulating materials to normal heatResistance to abnormal heat and fire due to internal electric effectsResistance to ultra-violet (UV) radiationLiftingMechanical impactMarking

10.210.2.210.2.310.2.3.110.2.3.210.2.3.3

10.2.410.2.510.2.610.2.7

YES

YESYESYES

YESYESYESYES

NO

NONONO

NONONONO

NO

NONONO

NONONONO

Degree of protection of enclosures 10.3 YES NO YES

Clearances and creepage distances 10.4 YES YES YES

Protection against electrical shock and integrity of protective circuits:Effective continuity between the exposed conductive parts of the ASSEMBLY and the protective circuitEffectiveness of the assembly for external faults

10.5

10.5.210.5.3

YESYES

NOYES

NOYES

Incorporation of switching devices and components 10.6 NO NO YES

Internal electrical circuits and connections 10.7 NO NO YES

Terminals for external conductors 10.8 NO NO YES

Dielectric properties:Power-frequency withstand voltageImpulse withstand voltage

10.910.9.210.9.3

YESYES

NONO

NOYES

Temperature-rise limits 10.10 YES YES YES

Short-circuit withstand strength 10.11 YES YES YES

Electromagnetic compatibility (EMC) 10.12 YES NO YES

Mechanical operation 10.13 YES NO NO

IEC 61439 OVERVIEWVerification of Low Voltage Power Switchgear and Controlgear Assemblies (PSC-Assemblies)

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TABLE 1: DESIGN VERIFICATION OPTIONS

IEC 61439IEC 61439 supersedes IEC 60439 and introduces the principles of Verified Assemblies. These replace the existing categories of Type Tested Assemblies (TTA) and the ambiguous category of Partially Type Tested Assemblies (PTTA) included in IEC 60439.IEC 61439 recognises three equal and alternative methods of verification that can be used by manufacturers to ensure compliance with the standard’s requirements. These are:

• Testing• Calculation• Design Rules

Testing includes either independent tests by approved testing bodies, or tests conducted by individual manufacturers, following approved procedures. Where methods of verification, other than testing, are used to demonstrate compliance with the standard, de-rating factors must be included.Refer to “Table 1: Design Verification Options”, for eligible verification methods applicable to each of the design criteria.Refer to “Table 2: Verification Methods Compared”, for further details.

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A F Switchgear LimitedNunn Brook Road, Sutton-in-Ashfield, Nottinghamshire NG17 2HU, England

Tel: 01623 555 600 Fax: 01623 55 800 E-mail: sales@afswitchgear.co.uk

L V Distribution Switchgear - Package Substations - Control Panels

Established in 1974, AF Switchgear have unrivalled experience in the design and manufacture of cost effective electrical switchgear and control applications.

MV/LV Equipment • MV Switchgear • MV Ring Main Units • MV/LV Package Substations

Complete MV/LV packages can be offered incorporating 11KV MV switchgear in either stand alone or close coupled to the LV equipment.

LV Distribution Switchgear • Main LV Switchgear • Generator and UPS Input/Output Switchgear • Sub-Distribution Switchgear

All switchgear configurations and forms of separation can be provided, manufactured in accordance with BSEN60439-1. All switchboard designs are type tested up to 6300A with ASTA/KEMA certification.

Power Distribution Units (PDU’s) • Available with Integral Static Transfer Switches • Hi-Isolation Transformers • Intelligent Metering and Final Circuit Monitoring Systems

Configurations available to suit all installation, performance and power monitoring requirements.

Containerised Solutions • Steel or GRP enclosures • Fully tested before despatch • Rapid installation and commissioning

Entire plant rooms containing combinations of HV substations, LV switchgear, standby generators and UPS’s. Built and tested off site, with their own low maintenance, weatherproof housing.

Control Panel and Systems • Motor Control Centres (MCC’s) • Direct On-Line, Star Delta, Soft Start and Variable Speed Drives • Compartmented and Wardrobe Designs

Equipment can incorporate a wide range of intelligent system controls with conventional relay logic, PLC systems, SCADA, live mimic and BMS systems.

Support • Routine service and maintenance • 24/7 call out facility

• Thermal imaging

Support contracts and services tailored to suit any requirement.

Performance, Quality and ReliabilityOur expertise in switchgear and control systems remains at the forefront of technology. This results from continued research and development and being regularly specified by consulting engineers to participate in major electrical projects for the UK, European and worldwide markets.Accreditation to ISO 9001:2000 and ASTA/KEMA certification demands strict control and audit of the procedures used throughout every aspect of company operation.