Stoneridge Engineering Home |
Thanks for the information, it was very useful for me. Well, now we are working toward the Over Haul of the generator, the visual inspection will be very important because there are traces of lubricant in the bushings. Perhaps will be necesary perform another test to the insulation system. I'll keep you inform of the results. And, thanks again for the tip, I'll signup right now. Raul Ugarte --Previous Message--
Lima - Peru
: --Previous Message--
: hi !
: I performed a Meg Ohm Test in several oppoortunities the stator and
: rotor of a hydrogen cooled generator (13.8 kV / 66 MW). Always with
: the rotr desacopled from the stator.
: Last week the test was performed with the generator totally mounted and
: with the hydrogen presurized (59oF / 28 PSIG).
: What criteria must I take to analyze the results? The hydrogen has a
: more or less capacitive behavior than air? Is the same, perform the test
: with hydrogen or air?
: The results indicates that the insulation levels are below the
: historical results of this machine.
: Thanks in advance for any clue !!!
: R. Ugarte
: :
: Hello Raul,
: Unfortunately, I'm not familiar with the type of tests that are required
: on a large hydrogen cooled generator. You may want to sign up (it's
: free) and then pose this question on the "Electric Power
: Engineering" Forums at the Engineering-Tips Forums site. This forum
: is populated by and for engineers who work in the electrical power
: industry and there are many there who will have the expertise. The
: Engineering-Tips Forum is at: http://www.eng-tips.com/
: As you know, hydrogen is used for its superior cooling, lower windage
: losses, and to inhibit oxidation/ozone in some horizontal
: turbogenerators. Unfortunately, hydrogen only has about 60% of the
: dielectric strength of air, but this deficiency is counteracted by using
: the gas under pressure. If you performed an insulation resistance (IR)
: test using a DC voltage, you shouldn't see much difference between air
: at STP and pressurized hydrogen testing. The slight increase in
: dielectric constant due to pressurized hydrogen should have virtually no
: impact on DC IR test results. If you were doing partial discharge (PD)
: testing using high voltage AC, you should also not see any much
: difference unless you were actually getting partial discharges within
: the insulation system.
: Since the IR is now lower than its historical level, the generator
: insulation may have degraded over time. Also, the insulation may have
: absorbed a bit of moisture during maintenance. The combination of these
: effects may account for reduced insulation measurements versus
: historical levels. However, you didn't mention whether the latest
: results were still within the manufacturer's specifications. Your best
: bet is to provide your test results and question to the turbogenerator
: manufacturer for a definitive answer. The experts on the
: Engineering-Tips Forum may also provide you with some more specific
: recommendations.
: Good luck and best regards,
: -- Bert --
:
:
Message Thread
« Back to index | View thread »