Fault Analysis Settings

This section describes the Fault Analysis area in the distribution equipment dialog boxes. This area is used to specify values related to fault calculation analysis. The information listed below is applicable to all distribution equipment unless otherwise indicated.

To manually specify a value, check the box next to it unless otherwise indicated. Use this when you know the value of a specific item or want to override what is calculated for you.

Feeder Length: The length of the conductor feeding the equipment. The value is automatically calculated if both connected devices are inserted on the drawing.

The label on this field depends upon the device type. The possible labels include Feeder Length, Primary Length, and Normal Feeder Length.

Bypass Feeder Length / Emergency Feeder Length: The length of the second conductor feeding a UPS or a transfer switch. The Normal Feeder Length corresponds to the device connected to Source 1. This feeder length corresponds to the device connected to Source 2. The value is automatically calculated if both connected devices are inserted on the drawing.

Feeder Length Settings: Press this button to open the Feeder Length Settings dialog box. Use this dialog box to specify how the feeder length is calculated and set the feeder length and building angle. See the Feeder Length Settings Dialog Box section below for more information.

Transformer Impedance %: The impedance through a transformer, as a percentage. The fault current on the secondary of the transformer decreases when the impedance percentage increases. Applies only to transformers.

Manually enter this value if you know what it should be. It can typically be obtained from the transformer manufacturer.

If you do not know the value, a default based upon the kVA of the transformer is used:

Transformer X/R Ratio: The X/R Ratio of the transformer. Applies only to transformers.

Manually enter this value if you know what it should be. It can typically be obtained from the transformer manufacturer.

A default value of 5 is used if you do not enter a value.

Set Fault @ <Device Type>: Press this button to set the fault at the device, in amps. This button is disabled if the box to the right is unchecked.

The label on this field depends upon the device type. The possible labels include Set Fault @ Panel, Set Fault @ Primary, Set Fault @ Secondary, and Set Fault @ Tap.

For transformers, the fault can be set at the primary and at the secondary.

Check the box next to this button to open the Lock Fault dialog box. Use this dialog box to specify the fault value at the equipment, based upon the information that you know. See the Lock Fault Dialog Box section below for more information.

Total Fault: The most recently calculated fault at the device, taking into account the fault from the utility and any motors in the project.

Recalculate Fault: Press this button to recalculate the Total Fault value. Does not apply to UPSs and generators.

<Device Type> AIC Rating: The ampere interrupting capacity (AIC) rating for the device. This value is not automatically calculated. It is important to specifically choose this value for all of the equipment in the project. Does not apply to generators or low voltage panels.

The label on this field depends upon the device type. The possible labels include Panel AIC Rating, Secondary Breaker AIC Rating, Device Tap AIC Rating, Tap AIC Rating, Bypass Breaker AIC Rating, MCC AIC Rating, TS AIC Rating, and AIC Rating.

When the Custom value is selected, a second AIC Rating field is available for manual input.

Feeder Length Settings Dialog Box

The Feeder Length Settings dialog box is displayed when you press the Feeder Length Settings button. It is used to set the feeder length calculation method or specify a feeder length manually.

Feeder Length Calculation Method: Sets how the feeder length is calculated. The values you can set vary depending upon the setting of this field.

Feeder Length: The calculated length of the feeder in feet and inches. This value can be set manually when the calculation method is set to Custom.

Building Angle: Sets the building angle relative to the alignment point when Feeder Length Calculation Method is set to Right Angles. See the How Building Angle Affects Calculations article in the knowledge base for more information about this setting.

Feeder Make-Up: The extra length of wire included in the feeder length to account for the wire used for distribution equipment connections. It is used in the fault calculation, voltage drop calculation, and takeoffs. The Set Default button allows you to change the Feeder make-up setting in the Distribution Equipment options section.

Lock Fault Dialog Box

The Lock Fault dialog box is displayed when you check the box next to the Set Fault button or press the Set Fault button. It is used to specify the fault at the equipment.

Lock: The values you can set vary depending upon the setting of this field. The other values are calculated based upon the ones you have locked.

Line-to-Neutral Voltage: The line-to-neutral voltage of the equipment. This voltage is used in the fault calculations.

Fault: The fault at the equipment.

Z: The impedance of the equipment.

X/R Ratio: The X/R ratio of the equipment.

X: The reactance of the equipment.

R: The resistance of the equipment.

Ignore Impedance in Downstream Feeder: Whether the impedance in the downstream feeder is ignored. The fault at the downstream equipment will be the same as the fault at this equipment. This setting is required by plan reviewers in some jurisdictions.