Feature Standards The IEC 61439 impact The current new IEC 61439 standard for low voltage switchgear and


controlgear assemblies switchgear has been working its way through the industry for some time. The importance of the standard and its implications for the planner, panel builders and end users are, however, becoming a little clearer. Mark Guest from Rittal comments


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n general, the safety requirements of electrical equipment are set today as general rules in the regu- lation of DIN EN/IEC, to observe the protection objectives for people and panels, and these rules are con- tinuously updated.


Appearing first in 1993, DIN EN 60439 regulated the different types of switchgear to one standard and classified them as TTA (type tested switchgear assemblies) or PTTA (par- tially type tested switchgear assem- blies). This classification led to a constant discussion on the merits of both TTA and PTTA.


The new standard DIN EN IEC 61439-1 are the general rules to the standard, which are referenced by all other sections, including IEC 61439-2, which relates to Power Switchgear and Controlgear assemblies (PSC). IEC 61439-2 defines the requirement of the detailed products more precisely. A low voltage switchgear system and controlgear assembly has to be a system consisting of: Enclosures


Climate Control Busbar (TS8, Ri4Power) (RiTherm)


Changes to the standard There are a number of significant changes between the IEC 60439 and IEC 61439 that the designer or panel builder must take into consideration to comply with the new standard. One is the replacement of TTA/PTTA with design verification, which is defined in the standard as ‘verifica- tion made on a sample of an assembly or on parts of assemblies to show that the design meets the requirements of the relevant standard’.


Design verification is achieved by the following, with examples: Testing • Mechanical properties – impact test (IK)


• Electrical – short circuit withstand values (Icw)


• Thermal test – effects of heat rise on devices within the PSC


Assessment, confirmation of the correct application of calculations and design rules, including use of appro- priate safety margins.


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• Clearances and creepage distances • Calculation of temperature rise only for PSC InA ≤ 1600 Amp


Structured comparison with a tested reference design • Temperature rise • Short Circuit withstand strength of protective circuit


Once the PSC has been assembled and the verification rules followed by the panel builder, the PSC has to go through routine verification – defined as ‘verification of each assembly performed during and/or after manufacture to confirm whether it complies with the requirements of the relevant assembly


standard’. Devices (RiLine60, PLS) (ABB, Terasaki, etc.)


Routine verification covers both perfor- mance and construction of the PSC. The effects of temperature rise in a PSC is a major change in the new standard and the most challenging for switchgear manufactures such as Rittal. To this extent, the company has invested in laboratories that can mea- sure and test the effects of heat rise up to 6300A. The data has been analysed and has led to the design of the Ri4Power switchgear system that fully complies with the new standard. The effects of heat on a device and its ther- mal rating can be quite significant between the IEC 61439 and IEC 60439, as highlighted here:


The standard describes the require-


ments and testing procedures for a com- bination of different devices, assembled in an enclosure, with a different opera- tion condition compared to the product standard. When the 100A device is fitted in an enclosure the nominal value of the device may change due to higher temperature


enclosure. The change in operation characteristics will reduce the nominal rating of the device to 82A Inc. Along with the heat effect on the devices there are set temperature limits within the standard, which must be adhered to if the PSC is to meet the standard. Temperature limits described in the standard:


• Copper busbar 105 K • Manual operating surfaces • Metal 15 K


• Insulating material 5 K •Terminals for external insulated con- ductors 70 K Rittal’s RPE design software takes into consideration the heat rise gener- ated in a PSC and compensates with the selection of the device such as the moulded case circuit breaker or air circuit breaker.


The IEC 61439 standard makes a clear distinction between the original manufacturer and the assembly manu- facturer. Definitions between the two manufacturers are:


Original manufacturer: ‘Organisation that has carried out the original design and the associated verification of an assembly in accordance with the relevant standard’.


Assembly manufacturer: ‘Organisation taking responsibility for the completed assembly’. In the case of the Ri4Power system, for example, it would make Rittal the original manufacturer who would be responsible for the design verification. Its customer would be the assembly manufacturer and would have to perform the routine verification tests as laid out in the new standard.


Difference in testing between the IEC 60439 and IEC 61439 The new standards have also detailed the forms of separation that apply within the PSC. The form rating describes the positioning in relation- ship to main busbars, functional units and device terminals.


For example, Form 4 lists the follow- ing instructions:


• Separation of busbars • Separation of all functional units from one another


• Separation of terminals for external conductors associated with a func- tional unit from the terminals of any other functional unit and the busbars


• Separation of the external conductors from the busbars


WINTER/SPRING 2013 Enclosure & Panel Building Solutions


generated within the


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