Recent content by yiefang

To PRC: Thanks for your answer. Just have a question, is necessary to carry out vacuuming until get below 3 torr & start counting for 36 hrs period. is there any calculation for a period of vacuum? let say this is old transformer & not all gasket was replaced. What is the best vacuum value to...

thanks for the answer. we already carried out the oil test and the result shows the ppm is 8.9 & dielectric strength >60KV. The IR shows acceptable value. The problem is, before this the winding only preserved with oil for around 90% portion only. is the winding still safe? Another thing, during...

complete set of oltc (diverter switch + tap selector)

Hi.. we have a generator transformer 350MVA which not be used for a 3 years. The last Furan analysis carried out found out the DP value is around 350. The transformer winding is still under oil without keep nitrogen. The OLTC diverter switch were removed before and only covered by blanketing...

Hi, i have a question on the replacement of On load tap changer. Usually what test to be carried out:- 1) Before replace the OLTC 2) During replace the OLTC 3) After complete the OLTC replacement.

rcwilson: We don't energize the transformer in wet condition..what i mean is we do a hot circulation for a 24 hrs period..and drain it back..after that we'll vacuum it to 36 hrs period..than we'll do filling up oil tx in vacuum condition..after everything ok which moisture is below 10ppm and BDV...

thank to all.. prc: Agreed with you..the purpose of the using hot oil circulation is for to release the moisture trap inside the winding..it will not release all the moisture..the vacuum process will not get out the moisture inside the winding..i am thinking after we energize the tx & put it in...

Dear All, We've a power transformer with capacity of ~ 400MVA. For the purpose of the repairing the transformer it cause the transformer were exposed with moisture for around 200 hours. Did anyone have a suggestion or opinion on the vacuuming process in order to remove the moisture inside the...

Dear All, FYI...We had a problem with 11KV/433v 2000KVA Cast Resin Transformer. The details of transformer are as follows: 1. Type: DYHK 2. Manufacturer: ABB 3. Rated Power : 2000 KVA 4. Rated Current: 105A-2666A 5. Insulation Class: HV/LV – F/F 6. Winding Material: HV/LV – Cu/Al 7. Insulation...