Electricity + Control 2019

ELECTRICAL PROTECTION + SAFETY

Table 2. As an example, Table E1 from IEC 61439-1 presents loading for an assembly with a rated diversity factor of 0.8.

facturer, to those outgoing circuits of an assembly that can be continuously and simultaneously load- ed, taking into account the mutual thermal influ- ences. Rated diversity factor can be stated: - For groups of circuits - For the whole assembly. The rated diversity factor multiplied by the rated current of the circuits shall be equal to or higher than the assumed loading of the outgoing circuits. The assumed loading of outgoing circuits shall be addressed by the relevant assembly standard. In addition to stating the rated diversity factor for a complete assembly, an assembly manufacturer may specify a different diversity factor for a group of related circuits within an assembly. The old IEC 60439-1 standard made provision for the use of certain conventional values, as Figure 1. An example of one of the general assembly drawings relating to Table E1 in IEC 61439-1. Actual loading is indicated by the figures in brackets e.g. [640 A]. Busbar section loading is indicated by the figure in brackets e.g. [320 A]

shown in Table 1 , for those instances where information regarding the actual currents was not available. The table was simple and easy to use in the absence of actual current loadings within the assembly. IEC 61439-1 uses a more elaborate series of general arrangement drawings and tables of an assembly equipped with a variety of functional units rated for a diversity factor of 0,8. These examples then show typical assembly/functional unit loading combinations that are possible. See Table 2 and Figure 1. It is important to note that while the IEC 61439 series of standards has been adopted in South Africa, the SANS 10142-1 Code of Practice for fixed electrical installations still refers to IEC 60439-1 and SANS 1973-1 standards. Hence they remain relevant and legal.

ELECTRICAL PROTECTION + SAFETY round up

New emergency lighting

- Protection against excessive battery discharge - LED charge indication light - Overcurrent protection - Quick-fit plug-in system - Four possible cable inlets, three on the side for tubes and one at the back - Optional ceiling-mounted version.

Beka Schréder has introduced its new DUISA range of emergency lighting with different signage options. The DUISA range is a quick-fit plug-in system with a three- hour battery back-up. Its high IP and IK ratings make the range suitable for indus- trial and commercial lighting needs. Key features include: - Degree of protection up to IP 65, IK 07 - Three-hour battery back-up - High-temperature resistant NiCd, NiMH rechargeable accumulators

Enquiries: Beka Schréder. Tel: +27 (0)11 238 0000, visit: www.beka-schreder.co.za

The DUISA range of emergency lighting with IP 65 protection rating is suitable for industrial applications.

Electricity + Control

JUNE 2019

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