IEC60909-1 or IEC61363 ? thread238-267182

[EddyWirbelstrom]

The following IEC short-circuit currents are required to specify breakers to IEC 62271.100 :
1) Peak short-circuit current ½ cycle after fault inception
2) rms value of a.c. current ( expressed as symmetrical breaking current Ib in IEC60909 )
3) d.c. current expressed as a percentage of the peak of the symmetrical breaking current.

Both the IEC 60909-0 and IEC 61363 methods calculate the above currents.

In an islanded radial system close to generators, above short-circuit currents 2) and 3) are more accurately calculated using the actual generator time-constants rather than the ‘standard’ time-constants in IEC60909 Section 4.5.2.1.
Should not the criterion for choosing between IEC60909-0 and IEC61363 be the proximity of large generators where high X/R ratios may result in short-circuit current zero crossing times beyond the contact parting time of standard circuit-breakers ? In this situation whether the installation is on a ship or on land why not use IEC61363 if the network in not meshed ?

 

[7anoter4]

IEC 60909-0/2001 1.1 Scope
It states:
"Short-circuit currents and short-circuit impedances may also be determined by system tests, by measurement on a network analyzer, or with a digital computer."
Therefore, it is permissible to employ data that are more accurate. However, this standard states also:
"This part of IEC 60909 does not deal with the calculation of short-circuit currents in installations on board ships and aeroplanes."
Instead of this IEC 61363−1:1998 states:
4.3 Basic assumptions
"Such a calculation is considered unnecessary for most practical engineering purposes, and accordingly beyond the scope of this standard."