DC Absorption Test

[Addy71]

Does anyone have experience in performing the DC Absorption Test & its analysis?

I know it involves applying 2.5/5 KV DC to the winding insulation & recording the charging current for a set period (typically 1000 seconds) & then discharging through an external resistor for the same period, again recording the same. These are then plotted on log scales as a function of time.

I believe it is possible to calculate various time constants (ion migration, slow relaxation, interfacial polarization) from these, but I do not know how (& the basis for analyzing this data). Any information would be very helpful.

Regards,

Aditya

 

[Zogzog]

Check the NETA ATS.

http://www.netaworld.org

for durations and ratios.

What are you trying to acomplish? What are you testing?

 

[aolalde]

Addy71
Consider IEEE Std 43-2000.
Absorption Current(IA), per IEEE Std 43 "is the current resulting from molecular polarizing and electron drift, wich decays with time of voltage application at a decreasing rate from a comparatively high initial value to nearly zero , and depends on the type and condition of the bonding material used in the insulation system."

It is a straight line in a log-log current-time graph.

IA= Kt^(-n)

were:
K is a function of the particular insulation system and applied voltage.
t is the time of applied direct voltage.
n is a function of the particular insulation system.

 

[Addy71]

I am a NETA member, there is not mention of this test in its Maintenance Specifications.

Our company recently performed a no. of tests (tan delta, PD, RSO, DC hi-pot, etc. on a 30 year 200 MW generator while overhauling it. The client has now pulled out an old report done by TVA, USA where this test has been performed, along with non-linear analysis of insulation (never heard of that either). They are insisting that we perform the identical tests so as to get a comparison.

I've done both the tests but interpretation is a question. I've shown them IEEE 43, not interested. Seems TVA are experts in Residual Life Analysis & we have to copy them.

Lets see how things work out. I got a good paper through Electricpete's reference, will go through it & see.

Regards,

Aditya

 

[edison123]

pete

Could you pls mail me the paper on this ?

Thanks