Load Data

This dialog box includes the following areas and tabs:

See Common Tabs for information on the Location, Comments, Hyperlinks, Media Gallery, or Collected Data tabs.

Figure 1: Load Data Dialog Box

Connection Information

Option Description
ID Name

Uniquely identifies the equipment item. The program automatically assigns a name, but you can change it, if needed. The name can be up to 16 characters long.

For loads, the program automatically assigns the names L-1, L-2, L-3, and so on.

To Bus This is the ID name of the bus to which the equipment is connected. The base kV of the bus is indicated on the right.

Specifications Tab

Option Description
Load Class To specify the class of in terms of importance. You can select Essential, Critical, or Non-essential. This field does not affect analysis. It can be used in database query to distinguish a certain load class from others. See Advanced Query.
Load Model

Specified: Designates the Load Data field to a user-entered model. You can enter any combination of constant kVA, constant I, or constant Z load.

SCADA: Designates the Load Data field to an imported real-time SCADA model. Data can also be user input in the SCADA fields just like Specified data.

Power Type

Select the power type for the equipment. The options are:

  • NPS: Normal Power Supply. For example, a power supply that has no backup.
  • CPS: Critical Power Supply. For example, a power supply that includes an uninterrupted power supply backup.
  • EPS: Emergency Power Supply. For example, a power supply that uses a generator for backup.

Load Data

Any combination of constant kVA, constant current, or constant impedance loads may be modeled. Different types of loads can also be mixed and matched to model a specific type of equipment such as variable speed drives.
Load Unit Specifies the units that will be used for load data. Use the box to choose the unit.
Constant kVA/MVA Constant kVA load entered in MW and MVAR. Note that the term “constant kVA” seems to be an industry standard even though MVA seems to be the more common unit for large industrial uses. See also Notes on Power Factor.
Constant I Constant current load given in MW and MVAR. These values should be entered in per-unit.
Constant Z Constant impedance load given in MW and MVAR. These values should be entered in per-unit.
Scaling Factor Each load can be varied by applying a different scaling factor. This lets you model the actual panel or lumped load on a bus, then study different loading conditions. This allows quick “what if” studies and prevents errors that occur from data entry.
Demand Factor Demand factor for the load.
Code Factors NEC code factor for the load.

DC Load Specifications

Figure 2: DC Load Specifications

Option Description
Load Class To specify the class of in terms of importance. You can select Essential, Critical, or Non-essential. This field does not affect analysis. It can be used in database query to distinguish a certain load class from others.

Power Type

Select the power type for the equipment. The options are:

  • NPS: Normal Power Supply. For example, a power supply that has no backup.
  • CPS: Critical Power Supply. For example, a power supply that includes an uninterrupted power supply backup.
  • EPS: Emergency Power Supply. For example, a power supply that uses a generator for backup.
Load Value Rated load in kW or Amps.
Scaling Factor Ratio of actual load to rated load in percent. This is used in power flow calculations.
Load Type

Choose one of the following types:

  • Constant kW: The kW consumed remains constant even when terminal voltage changes.
  • Constant I: Constant current is drawn by the load even when terminal voltage changes.
  • Constant R: The resistance is constant, so the kW and current will vary based on the terminal voltage.

Harmonics Tab

Use the Harmonics tab to indicate whether this equipment item is introducing harmonics into your power system.

Figure 3: Harmonics Tab

Option Description
Load Type

The default is Linear, indicating the equipment does not produce harmonics. Choosing Harmonic makes the item an harmonic source and makes other fields in this tab available to edit.

Note:
For an adjustable frequency drive (AFD), the Load Type is always Harmonic.
For motors, the Load Type is Harmonic if the With Adjustable Frequency Drive (AFD) check box is selected on the Specifications tab of the motor; otherwise, it is always Linear.
Fundamental Amps

Use to set the fundamental amps. The options are as follows:

  • Equipment Rating sets Fundm Amps to the equipment rating of the item described in the Specifications tab. 
  • User Specified activates the Fundm Amps field, enabling you to specify a value. 

To use fundamental current calculated by power flow, select Calculated from Power Flow in the Summation Fundamental Voltage area of the Harmonics Options > Control dialog box.
Harmonic Spreadsheet

Use the spreadsheet to enter the harmonic spectrum produced by this item. You can enter up to 30 different harmonics in each equipment item. In the spreadsheet, enter the Harmonic Number (such as 5 for the 5th harmonic), the Harmonic Current in percent of the Fundamental Amps, and the Current Angle. By indicating the current angle, you can simulate transformer phase shift effects on rectifiers so appropriate canceling can take place. The harmonic may be integer or non-integer.
Library Load

Common harmonic spectra may be entered from the device library. For instructions on how to enter your own spectra information, see Harmonics with Spectrum™. After selecting a particular device library spectrum from the Mfr and Type lists, click Import, and that spectrum is entered into the harmonic spreadsheet.
Resistance Factor

EasyPower offers two methods for calculating RH:

  • Resistance varying with a power of the harmonic (R-EXP):

    • RH = RFund * H R-EXP

  • Resistance varying with a percent eddy current factor (%ECF):

    • RH = RFund * (1+ECF*H2)/(1+ECF)

EasyPower defaults all skin effect correction to R-EXP and a value of 0.5.

Typical Resistance Correction Factors
  R-EXP %ECF

Transformer

0.5-1.0

1.0-3.0

Utility

0.0-0.8

    -

Generator

0.3-0.6

    -

Line/Cable

0.5

    -

Reactor

0.5-1.0

0.8-3.0

Motor

0.2-0.4

    -

Other Tabs

See Common Tabs for information on the Location, Comments, Hyperlinks, Media Gallery, or Collected Data tabs.

More Information

Database Technical Reference Common Tabs
Notes on Power Factor  
Media Gallery  
     

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Help was last updated on 7/10/2017