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# IEC60909 vs IEC61363

## IEC60909 vs IEC61363

(OP)
Dear All,

The IEC60909 is usually used for short circuit calculations in industrial premises.
It is applicable for meshed and unmeshed networks; for 3 phase as well as unsymmetrical faults; for far or near to generator faults.
It seems that we can use it everywhere.
But there is another standard in the IEC world for short circuit calculations: the IEC61363. It should be used only for ships and isolated offshore installations.

I believe that 909 could be used in ANY project including marine and offshore installations. So why did we need the 61363? Can I forget this standard and use 60909 everywhere?

### RE: IEC60909 vs IEC61363

I think IEC 61363-1 it is a simplified version of 60909 for an unmeshed system and the supply voltages are generators located on the ship [shaft generators]. That means they are active and non-active components. This could be more accurate calculation method.
The IEC 60909 standard use a Thevenin voltage located on the short-circuit point. [equivalent voltage source cUn/√3]. The generators are represented only by their impedance [no active components]

### RE: IEC60909 vs IEC61363

(OP)
Thank you.
I dont understand last sentences. 909 replaces a generator by a voltage source (active component) and its impedance. So it behaves like 363. Why do you think 363 is more accurate?

### RE: IEC60909 vs IEC61363

IEC 60909-0- 2.3 Method of calculation-2.3.1 Equivalent voltage source at the short-circuit location:
The method used for calculation is based on the introduction of an equivalent voltage source at
the short-circuit location. The equivalent voltage source is the only active voltage of the system.
All network feeders, synchronous and asynchronous machines are replaced by their internal
impedances (see clause 3).
IEC 61363-1
Active components
The synchronous machines used on marine/offshore electrical installations comprise
synchronous generators, motors and condensers. Knowledge of the short-circuit current
produced by these machines is fundamental to the calculation of the short-circuit current of an
electrical system.
Considering the actual level of the excitation,initial load and frequency will conduit to a higher accuracy[10% more].

### RE: IEC60909 vs IEC61363

Mr farale
1. IEC 60909 "Short-circuit currents in three-phase a.c. systems"
Sub-clause 1.1 scope .... calculation method an equivalent voltage source at the short-circuit location is introduced... The calculation of the short-circuit impedance is in general based on the rated data of the electrical equipment and the topological of the system ...
{take note} This part of IEC 60909 does not deal with the calculation of short-circuit currents in installations on board ships and aeroplanes.
2. IEC 61363 "Electrical installations of ships and mobile and fixed offshore units. Part 1: Procedure for calculating short-circuit currents in three-phase a.c."
Clause 1 Scope and object ....This international standard outlines procedures for calculating short-circuit currents that may occur on a marine or offshore a.c. electrical installation... The calculation methods are for use on unmeshed three-phase alternating current systems.
{take note} ... e) having their neutral point connected to the ship's hull through an impedance ...
The calculation formulas and methods described produce sufficient accurate results to calculate the short-circuit current during the first 100ms of a fault condition. They can be used ...
{take note} for time periods beyond 100ms the controlling effect of system voltage regulators may be predominant.
3. In brief
Each standard is drafted for a particular intended application. They are not intended to be interchangeable or one replacing the other.
"{take note}" is inserted by the writer, it is not part of the original text in the standard.
Che Kuan Yau (Singapore)

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