We will be discussing an example of the generator failure mechanism which can lead to a quick (months!) insulation breakdown. Do you wish to know that it is?

Please join us on Thursday 04 May 2023, 11am Brazil time (3pm UK time). We will go through details and RCA of 2 generator breakdowns, with hope that it will help you to prevent such situation in the future.

Please join the training using the link below:  
https://meet.zoho.eu/UDSxeI82x6

NOTE:
Please remember to register before the meeting, as number of participants is limited. Chrome and Firefox do not require downloading any other add-ons or apps, therefore these are preferable web browsers. Other web browsers may require downloading additional files. Please check with your IT Department.

O post FREE WEBINAR: Generator failure – Root Cause Analysis (RCA) of 2 generators with insulation breakdown apareceu primeiro em Nishi.

Voltage classification of generators/motors:

• Low Voltage: Round or Enameled Wire / Voltage Class: 127/220/380/440/760 V.
• Medium Voltage: Rectangular Wire / Coils or Bars / Voltage class: 2,3/3,4/4,16/6,6/6,9 kV.
• High Voltage: Rectangular Wire / Coils or Bars / Voltage Class: 13,8/16,5/18,0 kV or higher.

Standardized offline electrical testing:

• Insulation Resistance (IEEE-43);
• Polarization Index (IEEE-43);
• Ohmic Resistance (IEEE-118);
• HypotAC/DC (IEEE-4 / IEEE-95);
• Step VoltageDC (IEEE-95);
• Surge Test (IEEE-522);
• Off-line Partial Discharges (IEEE-1434 / IEC6034-27-1);
• Delta Tangent (IEEE-286);
• Capacitance (IEC 60034-27-30);
• Corona in darkroom) (IEEE-1799).

Turn on the subtitles in your language and watch below in Nishi’s Youtube channel the live recording and learn more about the definition and application of each electrical test according to voltage level and how it is essential for a good diagnosis of the condition of the motor/generator winding.

Take part in upcoming live opportunities to ask questions and make comments directly with an expert on rotating electrical machines.

Get in touch directly with engineer Fabio Toshio and get your questions answered: fabio.toshio@nishi.com.br

Request a commercial proposal: E-mail: nishi@nishi.com.br

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In machines that work at high temperatures (close to the temperature limit of the insulating material), the insulation between the plates deteriorates over time, causing the appearance of eddy currents or “eddy currents”, which circulate between the plates of the core that are shorted. The temperature at this location can often be 30 to 40ºC higher than the average core temperature.

The test commonly used to detect possible “hot spots” is the “Loop Test”. We wind coils around the magnetic core where the number of turns is calculated to achieve a flux similar to the nominal flux. We leave the core fed until its temperature stabilizes, and by thermovision we evaluate the temperature differences.

If one or more points are identified where the temperature variation is above average (10ºC or more), these points must be investigated and/or repaired. The repair is done by completely disassembling the core, stripping the insulation material, applying the new insulation, and assembling it.

Learn more about the services provided by Nishi and contact one of our experts for information about maintenance and standards applied to electrical tests of rotating machines.

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To ensure the loss levels and yields of these machines, the generators are designed with coils formed by multiple rectangular conductors in parallel, insulated from each other (“strands”) and transposed along their length, which we call “Roebel” transposition. Each parallel conductor is designed with a small cross section because in this way the eddy currents are reduced (Fujita, Kabata – 2005).

The commonly used transpositions are 360º and 180º. Studies show that in the 360º transposition the losses by circulating current reach close to zero.

Access our blog and read more NISHISAN tips on corrective maintenance services and characteristics of electrical machines. Contact our team and ask all your questions about different coil and bar manufacturing projects for turbogenerators and hydrogenerators.

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More than 1.8 thousand participants are expected and 500 technical reports will be presented. Nishi will present solutions and services of predictive, preventive and corrective maintenance for producers of electric power generation.

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