IEC60076-5 Ability to Withstand Short-Circuit 3

[Linspire]

Hi guys,

I would like to seek clarification sentences on IEC 60076-5 2000 clause 3.2.7 Tap-changing equipment.

Where fitted, tap changing equipment shall be capable of carrying the same overcurrents due to short-circuits as the windings. However, the on-load tap-changer is not required to be capable of switching the short-circuit current.

What is the difference between tap changing equipment and on-load-tap-changer ?

 

[davidbeach]

The on-load-tap-changer is tap changing equipment, but not all tap changing equipment consists of on-load-tap-changers.

 

[Linspire]

Any figure or photo shows few part for tap changing equipment ?

Would like to clarify clause 4.1.2 Value of symmetrical short-circuit current, I and clause 4.1.5 Calculation of temperature. Does only these two formulas to be applicable for all transformer design ?

I saw few formulas that used by the manufacturer which not indicated as per 60076-5 2000. Maybe some engineer here have the lastest version of 60076-5 2006 ed 3.0 can help me clarify.

 

[ScottyUK]

On-load tapchangers:

http://www.reinhausen.com/en/desktopdefault.aspx/tabid-53/92_read-64/

Off-circuit tapchangers:

http://www.reinhausen.com/en/desktopdefault.aspx/tabid-223/

Reinhausen are among the very best in the business - there's a lot of information on their site if you take the time to read it.

 

[Linspire]

Ok,ScottyUK,
I would like somebody help me clarify the 3th post.

 

[prc]

1)Tap changing equipment -Two types Deenergised Tap Changer(DETC) and On-load tap changer(OLTC).With OLTC you can change tappings while transformer is in energised condition.What the standard mentions is OLTC is not expected to change tappings when transformer is carrying short circuit current.

2) You have to refer to latest standard IEC60076-5 ed3.0 2006. In Annexure A "Theoretical evaluation of the ability to withstand the dynamic effects of short circuit" more calculations and formulae are given to estimate the short circuit withstand strength of transformer windings.

 

[Linspire]

Thank you, prc.

I noticed that OLTC did have life times which mean limitation of number switching tappings (200-500k times).

Well, in practical ( energising state ), how often OLTC does switching per day.

 

[kssschsekhar]

Hi Linspire

In practice, Number of OLTC switching per day depends on

1. The location of the transformer
Power generation plant's, Grid transmission transformer's OLTC requires less operations
Distribution trasnformer in Substation (not in power plants) OLTC require more number of oeprations to meet require load flcuations
Utility transformer require more number of operations depends again on grid connectivity, local generation (if any) etc.,
2. substations' voltage variations, Power quality etc.,

For more information it is good to ask OLTC manufactuer's. Becuase they have their equipment operating data. In this MR, Germany may provide information with all statitics with country wise.

 

[Linspire]

Thank you for enlighten me,kssschsekhar.
I think OLTC is very sensitive equipment, and always change tap changing, I wonder does a OLTC can last for many years. may be 3 or 5 years ?

 

[Linspire]

Guys,

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Mind to share the tutorial or precise example.