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 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 devices are inserted on the drawing.

The Feeder Length Settings button will 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 on setting the feeder length.

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 kVA

Default Transformer Impedance %

0 - 100

1.75%

112.5 - 300

2%

500

2.5%

750+

5.75%

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 not checked.

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.

Transformers can set the fault at the primary and at the secondary.

Checking the box next to this button will 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 on setting the fault at the equipment.

Total Fault: The most recently calculated fault at the device. Press the Recalculate Fault button to recalculate the 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:

distribution-equipment--aic-rating

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.

distribution-equipment--feeder-length-settings

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 when the calculation method is set to Right Angles. The Set Default button allows you to change the Building angle setting in the Distribution Equipment options section.

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

Default: The default calculation method for the project. The Set Default button allows you to change the Feeder length calculation method setting in the Distribution Equipment options section.
Right Angles: Set the building angle for the feeder length calculation.
Straight Line: Calculate the feeder length using a straight line.
Custom: Set the feeder length manually.

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.

distribution-equipment--lock-fault

Line-to-Neutral Voltage: This field displays 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.

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.

Fault: Lock the fault at the equipment. An X/R Ratio of 5 is used. Use this when you know the Fault but not the X/R Ratio of the equipment. This setting is the most common choice.
Fault and X/R Ratio: Lock the fault at the equipment and specify the X/R Ratio. Use this when you know the X/R Ratio of the equipment.
Z and X/R Ratio: Specify the impedance (Z) and X/R Ratio.
X and R: Specify the reactance (X) and resistance (R).

Ignore Impedance in Downstream Feeder: Whether the impedance in the downstream feeder is to be 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


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