Overhaul and modernization cycle on TENT power plants, status report nov 2012

, News Serbia Energy

A combination of many years of experience, knowledge, professionalism, supported with enthusiasm asa “fuel” and a wish to show that our country has world class engineers and repairers, led to a huge success achieved in TPP “ Nikola Tesla B”. The technical team from TPPNT A and B, during the first rehabilitationphase of the block B1, repaired the fault on the generatorrotorin a very short time.That way, occurrence of major faultson the machine, which could occur infurther operation, was prevented. Also the risk of the block falling out from mode of operationwas prevented, in the longrun. Besides, considerable funds were saved.

What hasactually been done? In brief, it could look like this: When in early July,a fault was found on the generatorrotor of the block B1, the decision was madeon repairing it, having in mind how longthe block overhaulwould last. In early August, the Company “Alstom”, dismantledboth rotor caps, and then the technicalteam ofTPPNT diagnosedthe fault, and repaired itin late August.

On the rotor winding, a short circuit was detected in the inter winding insulation. The fault was repaired by insertingadditional insulation between the two windings. The fault itself was not dangerous, but if that had not been removed,  two copper windings making the coil would be welded togetherlater on, and that could cause both magnetic and thermalimbalance of the very rotor. It would increase vibrations in the rotor, and in some cases, depending on the place where the interwinding is located,it could also cause the damage of the groove insulation that leads to earthingof rotor windings, and that further causes the machine to beout of operation for six  to seven months- explains Mr. Ilija Zec, theengineer for generators and power unitof 6 kV in TPPNT A.

Whilereinstalling rotor caps, the successive control tests were performed by the experts of the Laboratory for testing and calibration of the Electrical Engineering Institute “Nikola Tesla” ofBelgrade, thus confirming the successful repair.

Fault repair wasvery simple, according to Mr. Zec,however it was first necessary to identify the fault. When the fault was found, thetechnicalteam of TPPNT undertook to solvethe problem. In “Alstom”,they even suggested toresumethe operation until 2014without prior repairing the inter winding damage,no matter the risk and after that the rotor would be transported to their factory for repair. Thus,everything was done “on home turf” , on the site, and the generator rotor is fully functional again.
Successfully performed job cameas aresultof the experience early gained on the rotors of the generator “#4” of TPPNT  in 1985 and “#6” two years ago on the same location, as well as on the rotor “# 3” of  TPPK.

Although the rotor on the TPP B is much larger than others in the Company, concerning the fact that we are talking about the same type of a rotor, we knew right on how to adequatelyapproach to solving of the problem – said Mr. Zec, not missing the opportunity to mentionthe merits of the other members of his team- ZoranTomić, Dejan Simić, Miloš Lazarević, Bojan Radojičić and Marko Cvijanović, whoperformed the repairtogether with colleagues from TPPNT B.

In the company TPPNT, during the previous period, a number of engineers and repairers gained experience by being part of teams that performed overhauls, by learning from others, and repairing faults by themselves, and now they can independently perform many interventions on their own, withoutany external assistance.

For repairing of this fault, they did not use any special tools. Everything was done by using the existing workshop tools, available on the location, and with the know-how of our team.

All this shows that TPPNT represents a big and serious school for everyone in there. All of us working with TPPNT, dealing with similar jobs, learned a lot and gained necessary experience and knowledge, so that we could compete the top world experts in diagnostics and maintenance of the equipment – said Ljubiša Mihailović, Director for Production inthe company TPPNT.

What matters most here is that the people from TPPNT succeededinrepairing the fault within relatively short time, and that the block will be putin operation with fully repaired generator rotor.

Source Serbia Energy Magazine