Short-Circuit Currents in d.c. Auxiliary Installations in Power Plants and Substations - Part 2: Calculation of Effects
|Publication Date:||1 June 1997|
|ICS Code (Electricity. Magnetism. General aspects):||17.220.01|
This part of IEC 61660 describes a method for calculation of the mechanical and thermal effects on rigid conductors caused by short-circuit currents in d.c. auxiliary installations in power plants and substations. Such systems may contain the following items of equipment which act as sources, as well as contributing to the short-circuit currents:
- rectifiers in three-phase a.c. bridge connection for 50 Hz;
- stationary lead-acid batteries;
- smoothing capacitors;
- d.c. motors with independent excitation.
This standard provides a method which has wide application, and which gives results of sufficient accuracy. The calculation method is based on substitute functions, which cause approximately the same maximum stresses in the conductors and the same forces on the supports as the actual electromagnetic force.
The standardized calculation procedures of clauses 2 and 3 are applicable for the electromagnetic effect on rigid conductors and the thermal effect on bare conductors and electrical equipment, respectively.
For cables and insulated conductors, however, reference is made to IEC 60949 and IEC 60986, for example.
Only d.c. auxiliary installations in power plants and substations are dealt with in this standard.
In particular, the following points should be noted:
- The calculation of short-circuit currents should be based on IEC 61660-1.
- Short-circuit duration used in this standard depends on the protection concept, and should be considered in that sense.
- These standardized procedures are adjusted to practical requirements, and contain simplifications with safety margins. Testing or more detailed methods of calculation or both may be used.
- In clause 2 of this standard, only the stresses caused by short-circuit currents are calculated. Furthermore, other stresses can exist, such as those caused by dead-load, operating forces, or earthquakes. The combination of these loads with the short-circuit loading should be part of an agreement and/or given by standards, for example erection codes.