partial discharge test dry type Tx

[rainfire]

Hello

How important is it for a PD test to be carried out on a drytype transformer (11kv/400V)? Is it a nice to have or is it critical?

All other routine tests have been carried out ok.

 

[Zogzog]

Depends on what you mean by all routine tests.

IR?
DAR/PI?
TTR?
Winding resistance?
Pf?

Online PD testing is an effective means of detecting problems well before they occur in dry type transformers using magneticly coupled capactive sensors or high frequescy curent transformers.

When PD activity is found to exist further investigation is required to find the source, could be as simple as dirty windings (Clean it) or as bad as begining stages of insulation failure.

It all depends on what your budget and criticallity of the equipment is, regular on line PD testing can be a good indactor of when you need to do the "Routine" maintenance.

 

[rainfire]

When I say all routine tests have benn carried out, I refer to:

Temp Rise
Lightning impulse
24hr leakage
Voltage withstand
Over voltage withstand
Winding resistance measurement
Voltage ratio and vector measurement
No load loss and current measurement
Short circuit impedance measurement

I am struggling to ensure a fully complient PD test is carried out in accordance with BSEN60270.

I am just trying to realise its importance, especially since it is only carried out on Dry types.

 

[Zogzog]

Sorry, had to ask, for some people a routine testing for a transformer involves a megger test only or an IR scan.

Some of the tests you are describing sound like factory test terms, just curious where you got those from and who is doing the testing?

PD testing is done on oil filled also.

IEEE C57.127-2007 Guide for the Detection and Location of Acoustic Emmisions from Partial Discharges in Oil Immeresed Power transformers and reactors.

 

[ausphil]

As a factory routine test, PD is critical, as it will tell the purchaser how well the resin has been cast and cured (it is easy to skimp on resin content and have unacceptable curing temperatures, as well as not having sufficient vacuum pressures during casting)

Any anomolies in the resin (ie voids, holes etc) can be picked up using a PD test (if it is done correctly).

Past this point, as Zogzog points out, it can be an indicator of deterioration of the insulation, or an indicator of surface cleanliness.

Have a look at the SGB website. They have examples of online monitoring systems if you want to go to that extent.

Phil