Calculate Single Cable Size

To calculate the cable size for a single load, select the load from the Loads List, then:

1. Click Cable Sizing in the Calculations section of the List Tools - Loads tab. If the load is supplied via a single cable, the Cable Sizing window is then displayed.

2. If the load is supplied via multiple cables, the Select Cable to Size window is displayed:

   

3. Select the cable that is to be sized and click OK. The Cable Sizing window is then displayed.

   Note:
   The first time that the Cable Sizing window is accessed the following disclaimer is displayed:
   
   
   
   The message can be viewed again from a link on the Cable Sizing window.

4. The layout of the window depends on the cable sizing standard selected in the Options window (AS, BS, IEC or NEC).

   Note:
   The layout of the window is also different if the selected load is supplied by a cable that was imported from ETAP (refer to Import from ETAP). Refer to Calculate Single ETAP Cable Size for further information.

   For example, if the IEC standard is selected, the following is displayed:

   

   Note:
   For further details of the Cable Sizing window, refer to the AVEVA Electrical Common Functionality User Guide.

   Note:
   If user-defined cable sizing equations from a spreadsheet are to be used, check the External Cable Sizing checkbox. Refer to External Cable Sizing for further information.

5. Whichever standard is in use, select the appropriate details on the Cable Sizing tab and complete the Cable Length field.

   Note:
   If no length is entered, cable sizing may still take place using the default length entered in the Preferences window, if Zero Length Cable Sizing is enabled in that window. Refer to Options for further information.

   Note:
   For the IEC standard, the minimum value that may be saved in the Permitted Volt Drop and Starting Volt Drop fields is 0.05.
   The maximum value permitted for the Permitted Volt Drop field is 20. The maximum value permitted for the Starting Volt Drop field is 30.

6. If the cable is in fact a group of cables created when an enhanced wiring rule was applied to the load (refer to Group Cables and Create Wiring for a Single Load for further information), then the Cable Length field is disabled, and a button is displayed next to it:

   

7. Click the button. The Set Cable Lengths window is then displayed:

   

8. The window lists the cable in the cable group. Enter lengths for each of them and click OK. The total of these lengths is then displayed in the Cable Length field.

9. From the External Situation list, select either Free Air or Buried Underground. The middle section of the tab then changes to display the fields relevant to the selected situation. For example:

   

   or:

   

10. The Fault Protection tab includes two further tabs, Short Circuit and Earth Current:

    

11. On the Short Circuit tab, complete the details as required, and click the Calculate Short Circuit button to calculate the minimum required core size.

12. On the Earth Current tab, enter the voltage factor at device value, and click Calculate Earth Fault Current to calculate the Earth Loop Impedance and Earth Fault Current values.

    

    Calculate Cable Size

13. To calculate the cable size, click the Size Cable button.

14. If the core size is not found for the specified installation configuration, a message will be displayed to inform the user of this. Adjust the cable details and try again.

15. Otherwise, the Sizing Result tab is then displayed:

    

16. The Running Condition, Starting Condition, and Fault Protection fields are completed automatically when the Size Cable button is pressed.

17. Clicking the up arrow next to the Core Size field, increases the size and re-calculates the sizing results.

    Specify De-Rating Factor

18. After the Size Cable button is clicked, the De-rating Factor section on the Cable Sizing tab displays calculated de-rating factor values, based on the cable installation configuration.

    

    The user can select a de-rating factor which will be used instead of the calculated value.

19. To select a de-rating factor, click the De-rating Factors button. The Derating Factors window is then displayed:

    

20. Select the required factor from the list. The list includes the de-rating factors that are part of the standard, and user-defined project specific de-rating factor set up using the Cable Sizing Configuration window (refer to Cable Sizing Setup).

    If a value is 1 then the rating will have no effect on the calculation.

21. Click Save. The selected factor is then displayed in the Chosen De-rating Factor field.

    • The Chosen De-rating Factor field value can only be set by the user to be equal to or less than the Calculated De-rating Factor field value.

    • The User Changed checkbox indicates whether or not a factor has been changed by the user.

    • If this field is blank when the Size Cable button is clicked, it will be automatically populated with the calculated value.

      Complete Sizing Fields

22. Finally, click the Update button on the Sizing Result tab.

23. If no suitable cable is found in the cable catalogue (see the table below), a message is displayed to inform the user of this. Either revise the cable details or add a suitable cable specification to the catalogue.

24. If a suitable cable is found in the catalogue, the following Project Cable Data fields are then completed: Cable Number (an automatically generated number), Cable Type and Core Size.

25. Clicking on the up arrow button on the Sizing Result tab will select a higher cable size from the cable catalogue. The application will then re-calculate the core size, current, voltage drop, and short circuit and earth fault calculations.

    

26. Click Save to save these details and exit the window.

    Note:
    In order for cable data to be selected from the cable catalogue, the following values in the window must match those of a cable or cables in the catalogue:

    Field name in Cable Sizing window	Cable Catalogue field name
    Core Grouping	CoreGrouping
    Single / Multi	SingleOrMulti
    Material	Material
    Insulation Type	InsulationType
    Core Size	CoreSize
    Units displayed next to Core Size field	CoreSizeUnits
    Screened	Screened
    Armoured	Armoured
    Earth Core	EarthCore
    Rated Voltage *	VoltageDesc *

    * If the Rated Voltage / VoltageDesc field has a value then it is used to find a valid value in the Cable Catalogue grid. If the field has no value then does not search for a valid value in the Cable Catalogue grid.

    * If the Rated Voltage / VoltageDesc field has a value then it is used to find a valid value in the Cable Catalogue grid. If the field has no value then does not search for a valid value in the Cable Catalogue grid.

    Note:
    For further information of the cable sizing calculations, refer to the AVEVA Electrical Common Functionality User Guide.

    Note:
    The maximum number of cables that may be connected to an equipment item may (optionally) be specified in Electrical Wiring Manager. If the sizing procedure attempts to connect a cable to an equipment item when the maximum number of cables has already been connected to that item, a message is displayed to inform the user of this.
    
    
    
    Refer to the AVEVA Electrical Wiring Manager User Guide for further information of this window.