LV grid transients - an encore

[Skogsgurra]

More than four years ago, I needed to know about real world transients on LV grids. See

http://www.eng-tips.com/viewthread.cfm?qid=207168

I am now trying to understand what IEC 60 439-1 actually says. My interpretation is here

http://www.gke.org/pub/files/IEC 60 439-1 transient.jpg

But that is a lot more than I or anyone else seems to have encountered IRL. Does anyone have any new experiences? Any recordings of "Killer Transients"?



Gunnar Englund

http://www.gke.org

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Half full - Half empty? I don't mind. It's what in it that counts.

 

[Skogsgurra]

No new data?

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[Skogsgurra]

Invisible? Am I?

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[LiteYear]

FWIW, here in Australia we manufacture electrical safety devices for mining environments and the standards we adhere to require withstanding 75%-120% of the nominal LV line voltage continuously, and 50% for 2 seconds. The only transients considered are dielectric tests - ie. voltage to earth.

For example, here is the LV part of the table for test voltages as required by AS/NZS 2081. It shows the maximum voltage of the power circuit, the power frequency voltage withstand level (1) and lightning impulse voltage withstand level (2). Values for U(m) are in V and for (1) and (2) are in kV.

|U(m)| (1) | (2) |
| 275 | 2.5 | N/A|
| 450 | 3.0 | N/A|
|1200| 4.0 | 10 |

The power frequency voltage withstand is for 1 minute and the lightning impulse is a 1.2/50us wavefront.

But as far as transients phase to phase go, I haven't heard anything about values greater than 120% nominal. But then again, it's not really my field.

 

[Skogsgurra]

Thanks, Liteyear!
Your answer is in line with our experience. I am beginning to doubt the validity of the IEC 60 439-1 standard. Where, and under what circumstances can such a transient occur?


Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.