Installation of motor at far distance 1

[VMATHUR]

we wish to install a 3.3kV, 1250kW, Induction motor which will be started direct online.
The nearest 3.3kV source is at 600mtrs away, which is intern fed by 11/3.3kV, 10 MVA transformer 3.3kV Bus.

Please let us know is there any statutory requirement to limit the cable length or any other problem envisaged
for installation of the motor.

 

[ScottyUK]

Your 10MVA transformer is pretty big for a 3.3kV system, and so you should not see any significant voltage dip problem on the 3.3kV busbar caused by DOL starting this motor.

600m is not an unreasonably long distance, but you must ensure that the volt-drop through the cable at LRC is calculated to ensure that the motor able to produce sufficient starting torque. Use worst-case bus voltage for this calculation. I personally don't think you will find any problem with the motor you describe, unless you have a really awkward load.

The statutory requirements is really dependent on your own country's regulations. Is the 11kV system yours, or the utility's? You should consider any limitations from the utility regarding voltage fluctuation at the PCC, but with a 10MVA transformer you must be on a fairly robust 11kV system.

 

[sgelec]

as if the voltage drop is not above limits, please also check for short circuit at motor terminal in view of cable short circuit capacity, i have no idea about any sta--ry requirement.
thanks

 

[jbartos]

Suggestion: It may be a good idea to model the motor starting. There are motors that have very high locked-rotor currents (LRAs). Such motors can cause noticeable voltage dips and objectionable flicker.
Reference:
IEEE Std 141-1993 (Red Book) Section: 3.9.1 Motor Starting Voltage Sags