OLTC issues 5

[charlierod]

Wolud you mind installing an On Load Tap Changer in an existing 34.5/4/16 kV transformer to deal with voltage regulation problems instead of installing capacitor banks?
Potential problems with capacitors are resonance due to harmonics and switching transients. The only disadvantages with the OLTC would be installation and maintenance costs, do you see any other?

 

[charlierod]

There's an error in the original message. The transformer is two winding 34.5/4.16 kV.

 

[busbar]

Seems like a retrofit OLTC would be a project not for the faint of heart. [Adding a number of 5/8th-percent taps to an already assembled transformer sounds major.] Weigh other influences in the comparison, like nature of the load, desired voltage-stability time frame and {PF clauses in} utility tariffs, if applicable.

 

[jbartos]

Suggestion: OLTC reliability aspects should not be overlooked. OLTC is the only solution when it comes high no load voltages at downstream power distribution ends.

 

[charlierod]

busbar:

95% of the load are induction motors so improvements in voltage profiles are necessary to ensure proper operation.
Besides we must be prepared for possible system expansions

jbartos:

With respecto to your comment: "OLTC reliability aspects should not be overlooked. OLTC is the only solution when it comes high no load voltages at downstream power distribution ends", i have to say that actually we are facing undervoltages problems in MCC's supplied by this transformer. That's why i also mentioned capacitor banks as a solution.

If you guys know about a retrofit OLTC project already implemented,please let me know it would be very helpful.

 

[Alwaysexciter]

I would have to agree with Busbar that installing an OLTC on an existing unit may not be practical. However, you do often see an auto transformer installed ahead of an existing transformer to regulate primary side voltage.

Cost considerations would probably be the major issue.

 

[dpc]

A stand-alone three-phase step-type voltage regulator might be another solution. This would accomplish the same thing as an OLTC.

 

[jghrist]

An advantage of capacitors over either OLTC or stand-alone voltage regulators would be reduced feeder current and losses. Also the voltage profile would be flatter with capacitors, so that to maintain a particular voltage at the load, the source voltage does not have to be as high.

 

[jghrist]

Also, if the power supplier has a power factor penalty or charges a demand charge based on kVA, the capacitors would provide an economic advantage.

 

[jbartos]

Comment on charlierod (Electrical) Mar 19, 2004 marked ///\\jbartos:

With respecto to your comment: "OLTC reliability aspects should not be overlooked. OLTC is the only solution when it comes high no load voltages at downstream power distribution ends", i have to say that actually we are facing undervoltages problems in MCC's supplied by this transformer. That's why i also mentioned capacitor banks as a solution.
///Please notice that I referred to overvoltages not undervoltages when it comes to OLTC and overvoltage solutions, possibly voltage regulation solution. Capacitors can also be used to some extent and suitable applications; however, there are oscillation concerns.\\\