Derive Incident Energy Results Without an Upstream Device

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This article is useful in the following situations:
  • You are tasked with obtaining arc flash results in an application, where data gathering is incomplete or unavailable—for example, on the primary side of a transformer when you don't have the manufacturer’s type and style of the protective trip device.  (See figure 1 below.)
  • You have received the comment “No Valid Trip Device Found Upstream or in Bus Dialog” in the Arc Flash Hazard Report. (See figure 2 below.)

Data Missing from the Protective Device on the Primary Side of a Transformer
Figure 1: Data Missing from the Protective Device on the Primary Side of a Transformer

"No Valid Trip Device Found" Message
Figure 2: "No Valid Trip Device Found" Message

EasyPower has a User-defined Times option within the Bus Data dialog box that you can use to establish the arcing time duration for equipment when you don't know the specifications of a protective trip device that is upstream from an arcing fault event. This includes equipment such as panels, motor control centers (MCCs), switchgears, and automatic transfer switches (ATSs).

In the Database Edit focus, double-click on a bus and click on the Arc Flash Hazard tab. Under Trip Times for this Bus, change the option to User-defined Times, and then enter a desired arcing duration as shown below.

Entering bus user-defined trip time
Figure 3: Specifying the User-defined Times

When you select this option, the arc flash results are dependent upon the user-defined times rather than the characteristics of a protective trip device. We recommend you use the manufacturer’s published data  when it is available.    

Note: IEEE 1584 and NFPA 70E standards have a suggested guideline for “reasonable time” at a maximum of two seconds for arc flash calculations.



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