Load Flow Analysis in SKM

[Kanu_01]

I am new to load flow analysis.I have been told to maintain a voltage of 0.95 pu on my buses. I ran load flow studies on SkM and could see that there is much voltage drop on my buses. I have modelled utility as an infinite bus. What should I do to bring the voltage drop at my downstream buses within limits?

 

[Islander1]

Hi.

It is hard to know exactly what could cause your voltage drop, but I can suggest you to use larger cable sizes and if you have voltage regulator so you can also increase the tap ratio on the voltage transformers to keep the voltage within the limits.

Maybe you can post some single line drawings so we can see what you can do really to keep the voltage within the limits.

Thanks,

 

[dpc]

The critical step is making sure the loads are properly scaled. If the power flow is run at CONNECTED load for any type of industrial facility or large commercial building, problems like overloads and excessive VD are commonly seen in the model. You need to adjust the loads to reflect what you think the realistic maximum demand load will be.

 

[7anoter4]

First, you may reduce the Utility power as per IEC 60076-5 Table 2
For instance, for 7,2; 12; 17,5 and 24kV the maximum System short-circuit power is 500 MVA.
Check the transformers taps position. Reduce the line impedance by increasing the conductor cross section area, switch from aluminum to copper, fit capacitors and other [double- or more- parallel circuits, for instance].

 

[Kanu_01]

Thank you everyone.

 

[Kanu_01]

I have changed the tap of my transformer( negative tap) and voltage drop has reduced.

But I have one more concern, can it lead to over voltage situations?

 

[Kanu_01]

First, you may reduce the Utility power as per IEC 60076-5 Table 2
For instance, for 7,2; 12; 17,5 and 24kV the maximum System short-circuit power is 500 MVA.
Check the transformers taps position. Reduce the line impedance by increasing the conductor cross section area, switch from aluminum to copper, fit capacitors and other [double- or more- parallel circuits, for instance].

For voltages higher than 24kV, is it okay to choose 500MVA. How do you figure out the MVA rating for 1phase and X/R ratios for both 3ph and 1 phase?

 

[Kanu_01]

The critical step is making sure the loads are properly scaled. If the power flow is run at CONNECTED load for any type of industrial facility or large commercial building, problems like overloads and excessive VD are commonly seen in the model. You need to adjust the loads to reflect what you think the realistic maximum demand load will be.

I have modelled based on load list now. I have still kept utility as an infinite source though. I don’t think it will impact my load flow studies, but short circuit studies most definitely.