IEC 60364-5-55-2011 pdf free download – Electrical installations of buildings – Part 5-55: Selection and erection of electrical equipment – Other equipment.
551.2.2 The prospective short-circuit current and prospective earth fault current shall beassessed for each source of supply or combination of sources which can operateindependently of other sources or combinations. The short-circuit breaking capacity ofprotective devices within the installation and，where appropriate,connected to a system fordistribution of electricity to the public,shall not be exceeded for any of the intended methodsof operation of the sources.
NOTE Attention should be given to the power factor specified for protective devices in the installation.
551.2.3 The capacity and operating characteristics of the generating set shall be such thatdanger or damage to equipment does not arise after the connection or disconnection of anyintended load as a result of the deviation of the voltage or frequency from the intendedoperating range.Means shall be provided to automatically disconnect such parts of theinstallation as may be necessary if the capacity of the generating set is exceeded.
NOTE 1 Attention should be given to the size of individual loads as a proportion of the capacity of the generatingset and to motor starting currents.
NOTE 2 Attention should be given to the power factor specified for protective devices in the installation.
NOTE 3 The installation of a generating set within an existing building or installation may change the conditionsof external influence for the installation (see lEC 60364-1), for example by the introduction of moving parts, partsat high temperature or by the presence of inflammable fluids and noxious gases,etc.
551.2.4 Provision for isolation shall meet the requirements of Clause 537 for each source orcombination of sources of supply.
551.3 Protective measure: extra-low-voltage provided by SELV and PELV551.3.1 Additional requirements for SELV and PELV where the installation
is supplied from more than one source
Where a SELV or PELV system may be supplied by more than one source, the requirementsof 414.3 of lEC 60364-4-41 shall apply to each source. Where one or more of the sources isearthed, the requirements for PELV systems in 414.4 of lEC 60364-4-41 shall apply.
lf one or more of the sources does not meet the requirements of 414.3， the system shall betreated as a FELV system and the requirements of 411.7 of lEC 60364-4-41 shall apply.
551.3.2 Additional requirements where it is necessary to maintain the supply
to an extra-low voltage system
Where it is necessary to maintain the supply to an extra-low voltage system following the lossof one or more sources of supply, each source of supply or combination of sources of supplywhich can operate independently of other sources or combinations shall be capable ofsupplying the intended load of the extra-low voltage system. Provisions shall be made so thatthe loss of low-voltage supply to an extra-low voltage source does not lead to danger ordamage to other extra-low voltage equipment.
NOTE Such precautions may be necessary in supplies for safety services (see Clause 35 of IEC 60364-1).551.4 Fault protection (protection against indirect contact)
551.4.1 Fault protection shall be provided for the installation in respect of each source ofsupply or combination of sources of supply that can operate independently of other sources orcombinations of sources.
The fault protective provisions shall be selected or precautions shall be taken to ensure thatwhere fault protective provisions are achieved in different ways within the same installation orpart of an installation according to the active sources of supply，no influence shall occur orconditions arise that could impair the effectiveness of the fault protective provisions.IEC 60364-5-55 pdf download.