Enables you to choose the unit of fault current and the type of current. You can display the following types of currents on the one-line:
- Symmetrical: Fault current without the DC component.
- Asymmetrical: Fault current with both DC and AC components. The asymmetrical value is the maximum possible asymmetrical value in any phase. Asymmetrical currents are based on the following equation:
Iasym = I sym [1 + 2e{-4πÁ / (X/R)}] 1/2
Á= 0.49 - 0.1 e{-(X/R)/3}
For interrupting duty currents the asymmetrical value is based on the fault point X/R ratio, the No AC Decay (NACD) ratio, the contact parting time of the breaker, and whether the breaker is rated on a Total or Symmetrical basis. The NACD ratio consists of two factors dependent upon whether generation is Local or Remote. The equations and calculation procedures are too detailed for this discussion. For more information, see the Reference1 below.
For 30 cycle faults no asymmetry is present, and the asymmetrical current equals the symmetrical current.
Max Symmetrical and (Max Asymmetrical): This choice displays both symmetrical and asymmetrical branch flows.
The following fault current units are available for display in the one-line:
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