Low-voltage switchgear and controlgear assemblies - Part 2: Power switchgear and controlgear assemblies

Overview

IEC 61439-2:2020 is the product part of the low-voltage switchgear and controlgear assemblies series covering power switchgear and controlgear assemblies (PSC-assemblies). In data centres these are the main LV switchboards and motor control centres. The standard applies to assemblies with a rated voltage not exceeding 1 000 V AC or 1 500 V DC and a supply frequency not exceeding 1 000 Hz. Edition 3 was published on 22 July 2020 and runs to 103 pages.

The main changes in the 2020 edition are these: Annexes DD, EE and FF were added for assemblies used in photovoltaic installations; the rules on internal separation were tightened; and temperature-rise verification routes were introduced for large naturally cooled and actively cooled assemblies.

On internal separation, the abstract states that with a form of separation higher than 1, parts left live in a switched-off functional unit compartment must be protected to at least IPXXB. The rule aims to prevent contact with live parts in neighbouring compartments while working in one compartment during maintenance, and it matters in concurrently maintainable designs. The product part is used together with the series' general rules document IEC 61439-1 and is also available in Turkey as TS EN 61439-2.

The new temperature-rise routes are as follows: for naturally cooled circuits above 1 600 A, comparison with a reference design plus calculation; for actively cooled assemblies, a separate verification up to 1 600 A. The abstract also notes that the IP rating is considered when active cooling is present. As a limit, the details of the verification methods and the full definitions of the forms of separation are in the text and are not part of this record.

Key points

1. Applies to PSC-assemblies with rated voltage not exceeding 1 000 V AC or 1 500 V DC and frequency not exceeding 1 000 Hz.
2. Covers the main LV switchboards and MCCs in data centres.
3. Annexes DD, EE and FF were added for assemblies used in photovoltaic installations.
4. With form of separation higher than 1, parts left live in a switched-off functional unit compartment must be protected to at least IPXXB.
5. New temperature-rise verification: naturally cooled circuits above 1 600 A by reference design comparison plus calculation; actively cooled assemblies up to 1 600 A.
6. IP rating is considered with active cooling.
7. Edition 3, published 22 July 2020, 103 pages.

Using it in design

• On the main LV switchboard object, require form of separation (1-4b) as a catalogue field and default to Form 3b/4 for concurrently maintainable designs.
• Flag main busbars above 1 600 A as needing verified temperature-rise data from the vendor.
• For actively cooled boards, confirm with the supplier that the IP rating is also met under cooling.
• For PV-fed boards, write the scope of the relevant annex (DD, EE, FF) into the specification.

Who should read it

Data centre electrical designers, switchboard manufacturers and engineers writing specifications for main LV switchboards.

Related standards

• IEC 61439-1
• IEC 60364-5-53
• TS EN 61439-2

Publication details

Authors

IEC TC 121

Publisher

IEC

Year

2020

Document number

IEC 61439-2:2020

Document language

English

Source type

Standard

Access

Citation only

Licence

Copyright retained; citation only — the publisher’s terms apply to the original document

Citation