Standards applicable to UPS systems and installations

The question of standards relating to UPSs involves many aspects. There are safety, EMC compliance and performance considerations for the UPS equipment itself, and limitations for the equipment’s impact on the power network. Lead-acid batteries have their own regulations relating to selecting, safe operation, testing, maintenance and replacement. Further aspects of the UPS installation are also subject to regulation; these include environmental protection (IP) standards, wiring regulations, equipotential bonding and earthing, and other factors.

Below, we review the most important of these standards. Primarily, UPSs must comply with Low Voltage (LV) electromagnetic compatibility (EMC) directives as well as other regulations. This compliance is typically achieved through UPS Standard EN62040, which comprises three parts:

  • EN62040 – Part 1 (General and Safety Requirements)
  • EN62040 – Part 2 (EMC – Electromagnetic Compatibility)
  • EN62040 – Part 3 (Performance)

Part 1: General and Safety Requirements: The standard applies to electronic indirect AC converter systems with an electrical energy storage device in the DC link. Primarily, the UPS must ensure continuity of an alternating power source, but it may also serve to improve power quality and keep supplies within specified characteristics. The standard is applicable to movable, stationary, fixed and built-in UPSs for distribution systems up to 1000 Vac.

EN 62040-Part 1 is to be used in conjunction with EN60950:2006 “Safety of information technology equipment including electrical business equipment”. The standard also incorporates, by dated or undated reference, provisions from other publications – as do Parts 2 and 3 as described below.

Part 2: Electromagnetic compatibility. This EMC standard applies to single UPSs for installation in any operator-accessible area or in separated electrical locations, connected to either industrial or public low voltage networks. The EMC standard takes precedence over all aspects of the Generic standards and no additional testing is necessary.

Part 3: Performance. The performance requirements of this standard are for UPSs within the scope of EN62040-1. The standard applies to UPSs with:

  • Single- or three-phase, fixed frequency, 50/60 Hz AC output voltage
  • Single- or three-phase input voltage
  • Electrical energy storage device in the DC link, unless otherwise specified
  • With rated voltage not exceeding 1000 Vac
  • Movable, stationary, or fixed equipment

This standard’s specifics:

  • Equipment characteristics
  • Test methods
  • Minimum performance levels

UPS topologies and their impact on performance

The International Electrotechnical Commission (IEC) established IEC 62040-3 to define different UPS topologies and the measurements of performance. Cenelec, the European standards committee, adopted the IEC standard as EN 62040-3 – now recognised as the authoritative definition of three standardised UPS topologies:

  • Offline -VFD or Class 3 category
  • Line Interactive – VI or Class 2 category
  • On-line – VFI or Class 1 category

This classification is coded in three steps. The first is output dependency, where the UPS is either Offline (Dependent on mains Voltage and Frequency), Line Interactive (Dependent on mains Frequency variations, mains Voltage variations are regulated and Independent) or On-line (Output is Independent of Mains Voltage and Frequency variations).

The second step relates to the output waveform, classified as either non-sinusoidal or sinusoidal, and further differentiated according to harmonic content within IEC 61000-2-2 linear and non-linear load conditions specifications, as well as battery or mains operation.

The third step classifies UPS output dynamic performance during change of operation mode performance, step linear load performance, or step reference non-linear load performance – the last two relationships apply to both mains and battery mode.

According to the codes specified, the highest possible UPS classification is VFI-SS-111, which is only met by modern, true on-line, double-conversion UPSs.

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