Fault Analysis Settings

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

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

Feeder Length: The length of the conductor feeding the device. 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, Transformer 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.

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 checkbox 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 @ Switchboard, Set Fault @ Transformer Primary, Set Fault @ Transformer Secondary, Set Fault @ Tap, Set Fault @ Bus Gutter, Set Fault @ Breaker, Set Fault @ UPS, Set Fault @ MCC, Set Fault @ Generator, and Set Fault @ Transfer Switch.

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

Checking the checkbox next to this button or pressing the button will open the Lock Fault dialog box. Use this dialog box to specify the fault value at the device, based upon the information that you know. See the Lock Fault Dialog Box section below for more information on setting the fault at the device.

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 Available Interrupting Current (AIC) rating for device. This value is not automatically calculated. It is important for the designer to specifically choose this value for all of the devices 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.

One-Line Devices--Custom AIC Rating example

Lock Fault Dialog Box

The Lock Fault dialog box is display 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 device.

One-Line Devices--Lock Fault Dialog Box

Line-to-Neutral Voltage: This field displays the line-to-neutral voltage of the device. This is the voltage used in the fault calculations.

Fault: The fault at the device.

Z: The impedance of the device.

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

X: The reactance of the device.

R: The resistance of the device.

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 device. An X/R Ratio of 5 is used. Use this when you know the Fault but not the X/R Ratio of the device. This setting is the most common choice.
Fault and X/R Ratio: Lock the fault at the device and specify the X/R Ratio. Use this when you know the X/R Ratio of the device.
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 or not the impedance in the downstream feeder is to be ignored. The fault the downstream device will be the same as the fault at this device. This setting is required by plan reviewers in some jurisdictions


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