One-line Output Tab

To set short circuit options, from the Short Circuit focus, click SC Options. You can also access the options from within the Database Edit focus by selecting Tools > Options > Analysis Options > Short Circuit.

On the One-line Output tab, specify the options you want for controlling what is output to the one-line during the short circuit study.

Figure 1: One-line Output tab of Short Circuit Options Dialog Box

Option Descriptions
Option Description

Display Options

These options enable you to control what appears on the one-line while performing short circuit calculations.

Show Units

Select for short circuit results to appear with their corresponding units, such as kA, MVA, or pu for branch flows and kV(LL) or pu for voltages.

Show CT and Relay Symbols

Select for the symbols for CT and relays to appear in the one-line.

Show Branch Flows

Select to display branch flows during a short circuit. If these are not selected, only the bus fault current appears on the one-line.

Show All Remote V&I for Single Bus Faults

Select for the branch flows and bus voltages to appear on all branches and buses. With this option, you do not need to perform a separate Remote Bus V&I command.

One-Line Output Options

Decimal Precision

This sets the number of digits past the decimal point for values displayed on the one-line.

Display Units

Fault Current:

Enables you to choose the unit of fault current and the type of current. You can display the following types of currents on the one-line:

  • Symmetrical: Fault current without the DC component.
  • Asymmetrical: Fault current with both DC and AC components. The asymmetrical value is the maximum possible asymmetrical value in any phase. Asymmetrical currents are based on the following equation:

    • Iasym =  I sym [1 + 2e{-4πÁ / (X/R)}] 1/2

    Á= 0.49 - 0.1 e{-(X/R)/3}

    For interrupting duty currents, the asymmetrical value is based on the fault point X/R ratio, the No AC Decay (NACD) ratio, the contact parting time of the breaker, and whether the breaker is rated on a Total or Symmetrical basis. The NACD ratio consists of two factors dependent upon whether generation is Local or Remote. The equations and calculation procedures are too detailed for this discussion. For more information, see the Reference1 below.

    For 30 cycle faults no asymmetry is present, and the asymmetrical current equals the symmetrical current.

    Max Symmetrical and (Max Asymmetrical): This choice displays both symmetrical and asymmetrical branch flows.

    The following fault current units are available for display in the one-line:

    • kA
    • MVA
    • Per-unit

Remote Bus Voltage (Sym)

Voltages can be displayed as symmetrical voltage in either physical units (kV) or in per-unit values.
Voltage Sensitivity Highlighting

High/Low Voltage Remote Buses

This option highlights all buses on the one-line with voltages below a user-specified threshold value for a single fault. Voltage sensitivity studies are used to determine problem areas which may cause contactor dropout or equipment failure for critical areas such as boiler feed water pumps, ID fans or drive systems. Refer to the Control tab of the Short Circuit Options dialog box for setting the threshold value.

Both high and low voltage remote buses can be studied.

Vector Coordinates

Enables display format as:

  • Magnitude
  • Magnitude and Angle
  • Real and Imaginary

Default

In the Short Circuit Options Defaults dialog box, you can specify which default short circuit option settings you want to use. This affects the settings in the entire dialog box and is not limited to only the currently selected tab. These default settings are used for all new one-lines.

The options are:

  • Store Current Options as Default Settings: This stores all of the current short circuit options in your equipment defaults file.

  • Reset Current Options to Default Settings: This updates all of the current short circuit options based on those you stored previously in your equipment defaults file.

  • Reset Current Options to Factory Settings: This updates all of the short circuit options to match the defaults that are included in the initial installation of the EasyPower program.

Default settings specified here only affect ANSI settings.

Reference:
1 AC High Voltage Circuit Breakers Rated on a Symmetrical Current Basis, ANSI/IEEE Std. C37.010-1979.

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