Faulting a Bus

There are three ways to fault a bus. The easiest way is to double-click on the desired bus. A fault will be placed on the bus using the options chosen on the ribbon and in the Short Circuit Options dialog box, which is available by clicking SC Options in the ribbon.

Figure 1: Faulting a Bus

The results are immediately displayed on the one-line. In this example, the faulted bus current is 16.952 kA, which is shown diagonally on the right side of the bus. The contribution from the upstream branch is 14.616 kA, and the motor contribution is 1.201 kA.

If text results are also desired, select the appropriate result window in the Text Output tab of the Short Circuit Options dialog box.

Another way to initiate a fault is to first select a bus (the bus will highlight) and then click Fault Bus(es). You can select more than one bus to fault if desired.

To fault all the buses (batch fault), click Fault Bus(es) without selecting any buses.

Changing the IEC Standard Time Interval

The following currents can be calculated in EasyPower:

• Initial (Momentary) current: This is the first cycle current. To display results for this current, click Momentary in the Short Circuit ribbon.
• Breaking currents for 0.02 seconds, 0.05 seconds, 0.1 seconds and >0.25 seconds: To display these values, click the corresponding buttons from the ribbon.

You can view up to 3 types of fault current values by time interval.

Figure 2: Short Circuit Results at Various Time Intervals

You can also view fault currents in various forms, such as by phase current values (A, B, C) or their symmetrical component values (positive sequence, negative sequence, zero sequence or 3 times the zero sequence).

Displaying Fault Currents by Current Type

You can also display fault currents as symmetrical rms, asymmetrical rms or as peak. To change the display current type, click SC Options in the ribbon, select the One-line Output tab, and select the desired type in Fault Current, as shown in the figure below. The following choices are available:

• Symmetrical: rms value of AC component.
• Asymmetrical: rms value of AC and dc components combined (total).
• Max Sym and (Max Asym): The maximum phase current amongst the three phases. Both AC symmetrical rms and asymmetrical rms values are displayed, the asymmetrical values appearing in parentheses.
• Max Sym and (Max Momentary Peak): The maximum phase current amongst the three phases. Both initial AC symmetrical rms (I_k”)and peak (Ip) values are displayed, the peak values appearing in parentheses.

The first three choices are applicable for any time interval, whereas the last choice is only applicable for the momentary (initial) currents.

Figure 3: Short Circuit Options for IEC

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