AC Hi-pot Sizing 1

[Cogenite]

I am looking to conduct an offline partial dischrge test on a synchronous generator. I need an AC Hi-Pot machine with a rating high enough to overcome the winding impedance and bring each phase winding up to phase voltage (10.4 kV). Can anybody tell me how to properly calculate the required output rating for the AC Hi-Pot machine to conduct the test? I had one rated for 3 amps, but it would blow its output fuses before the winding got to full voltage.

 

[Zogzog]

Here is a tip, get a VLF hipot and save the trouble and thousands of dollars.

 

[edison123]

Since you say phase voltage is 10.4 KV, I assume it is a big machine (over 200 MW ?) For such machines, the winding capacitance would be around 0.25 to 0.35 microfarad. I am sure you can do the math to get the current.

 

[dpmac]

In the US contact Advanced Testing Systems at

http://www.advtest.com

they have a number of trailer mounted series resonant test sets designed for generator testing.

 

[DTR2011]

phoenix also makes big units.

I've heard that VLF can be used, but has some other issues, depending on the PD sensing technology and means of coupling.

 

[Zogzog]

No problem with VLF at all and if you do the math for the size of the power supply needed at 0.1Hz compared to 60Hz you will see the advantages of VLF.

 

[benlanz]

The only trouble with VLF is that the PD results can not be compared to IEEE standards. You need power frequency to use the standards.

Benjamin Lanz
Vice Chair of IEEE 400
Sr. Application Engineer
IMCORP- Power Cable Reliability Consultants

 

[edison123]

Thank you benlanz. I was waiting for someone better than me to say that. VLF is touted as an easy way out in many cases where power frequency plays a crucial part in the test results and interpretation.

 

[Zogzog]

If you have a large data base of PD samples and VLF frequencies I dont see what the problem is.

 

[dpmac]

ZogZog,

Do you know of anyone or any firm who has a database (of any size) of PD values associated with VLF testing of generators?

If you get a chance, please forward the info to me.

Thank you.

 

[Zogzog]

IQ systems in California