SKM Result - Negative Voltage Drop

[buddy91082]

We are running a low voltage (<600v) drop study in SKM and are coming up with a few values with a negative voltage drop. Curious as to why the results might be coming up with a negative % voltage drop result on some of the buses and feeders and the negative % results means.

Thanks.
b

 

[HamburgerHelper]

Closely bundled and long cables on lightly loaded feeders?

On long sections of transmission lines, if they are lightly loaded or open ended, the voltage swings up from the Ferranti effect.

Depending on how strong your grounding is, imbalanced load can cause overvoltages on some of your phases.

 

[buddy91082]

This is for 480v, 60hZ three phase feeders within a building 200'-300' long. The feeders are lightly loaded.

 

[HamburgerHelper]

Calculate the surge impedance loading of your cables and compare that with your load.

 

[ciy]

Maybe you in-service some capacitors in your system.

 

[waross]

Power factor correction at the end of the feeders?
The cable capacitance on an unloaded or very lightly loaded cable?
Single phase loading will cause a voltage drop on the neutral which will be a voltage rise on the unloaded phases.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[magoo2]

What load are you simulating and what is its power factor?

 

[EddyWirbelstrom]

All of the above responses are valid.
Are you referring to the branch voltdrop or bus volt drop ?
PTW reports bus voltdrop in percentage with respect to the nominal voltage.
eg. If the bus nominal voltage is 415V and the bus loadflow volts are 425V, then the reported LF VD% is +2.4%.