Stator winding failures: contamination, surface discharge, tracking

Dymond, J.H.; Stranges, N.; Younsi, Karim; Hayward, J.E.

doi:10.1109/28.993182

Cited by 32 publications

(11 citation statements)

References 5 publications

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“…4(b). This discharge generates in the air gap, between the magnetic core and the side of stator bars [11]. As described above, the PD pattern was presented internal discharge at 8 kV in phase B.…”

Section: Test Results and Discussionmentioning

confidence: 99%

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Characteristics of Insulation Diagnosis and Failure in Gas Turbine Generator Stator Windings

Kim¹

2014

Journal of Electrical Engineering and Technology

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-In order to evaluate the insulation deterioration in the stator windings of five gas turbine generators(137 MVA, 13.8 kV) which has been operated for more than 13 years, diagnostic test and AC dielectric breakdown test were performed at phases A, B and C. These tests included measurements of AC current, dissipation factor, partial discharge (PD) magnitude and capacitance. ΔI and Δtanδ in all three phases (A, B and C) of No. 1 generator stator windings showed that they were in good condition but PD magnitude indicated marginally serviceable and bad level to the insulation condition. Overall analysis of the results suggested that the generator stator windings were indicated serious insulation deterioration and patterns of the PD in all three phases were analyzed to be internal, slot and spark discharges. After the diagnostic test, an AC overvoltage test was performed by gradually increasing the voltage applied to the generator stator windings until electrical insulation failure occurred, in order to determine the breakdown voltage. The breakdown voltage at phases A, B and C of No. 1 generator stator windings failed at 28.0 kV, 17.9 kV, and 21.3 kV, respectively. The breakdown voltage was lower than that expected for good-quality windings (28.6 kV) in a 13.8kV class generator. In the AC dielectric breakdown and diagnostic tests, there was a strong correlation between the breakdown voltage and the voltage at which charging current increases abruptly (P i1 , P i2 ).

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Section: Test Results and Discussionmentioning

confidence: 99%

“…The presence of discharges at the bar ends causes progressive degradation of the semiconducting and voltage grading paint surfaces [12]. The semiconducting and voltage grading paints are used to suppress surface discharge in the slot portion of the winding [11]. Consequently, when the phase B of No.…”

Section: Test Results and Discussionmentioning

confidence: 99%

Characteristics of Insulation Diagnosis and Failure in Gas Turbine Generator Stator Windings

Kim¹

2014

Journal of Electrical Engineering and Technology

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“…Failures of HV motor stator winding insulation usually occur due to defects in the groundwall or turn insulation, and the failure mechanism involves the gradual development of a weakness in the insulation. This weakness is usually caused by a trapped void that is gradually and continuously grows in size due to a combination of the above-mentioned operating stresses and corona or PD activity [9]. As stated earlier, Pi2 occurred more than 5kV and all motors with stand 2E+1kV the stator winding need not rewind.…”

Section: Resultsmentioning

confidence: 99%

Assessment of Insulation Deterioration in Stator Windings of High Voltage Motor

Kim¹,

Kong²

2012

The Transactions of The Korean Institute of Electrical Engineer

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-To assess the insulation deterioration of stator windings, diagnostic and AC breakdown tests were performed on the eleven high voltage (HV) motors rated at 6kV. After completing the diagnostic tests, the AC overvoltage test was performed by gradually increasing the voltage applied to the stator windings until electrical insulation failure occurred, to obtain the breakdown voltage. Stator winding of motors 1, 3, and 8 failed at above rated voltage at 14 kV, 13.8kV, and 16.4kV, respectively. The breakdown voltage of three motors was higher than expected for good quality windings in 6kV motors. Based on deterioration evaluation criteria, the stator winding insulation of eleven HV motors are confirmed to be in good condition. The turning point of the current, Pi2, in the AC current vs. voltage characteristics occurred between 5kV and 6kV, and the breakdown voltage was low between 13.8kV and 16.4kV. There was a strong correlation between the breakdown voltage and various electrical characteristics in diagnostic tests including Pi2.

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“…Sparking generally occurs during the starting condition [4,5]. Corona discharges and surface tracking [6] on contaminated winding can also cause sparking. The phenomenon of sparking and arcing could pose a hazard in explosive atmosphere [7].…”

Section: Introductionmentioning

confidence: 99%

Performance Analysis of Increased Safety HT Induction Motor with Higher Stator Coil Pitch for Classified Hazardous Area

Ahirwal

Chatterjee

2014

IJEEI

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The increased safety (Ex e) high tension (HT) motors are widely used in the petroleum industries and area where explosive atmosphere is present. The time t E and I A /I N ratio value is very important for Ex e motor. The time t E of rotor and or stator winding, I A /I N ratio and temperature rise can be affected by increasing the stator coil pitch. The coil pitch of stator were increased for three different ratings of three phase HT Ex e induction motors and redesigned for analyzing the temperature rise, t E and performance. The relevant tests were performed and performance characteristic of motor was compared with normal design motor.

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Stator winding failures: contamination, surface discharge, tracking

Cited by 32 publications

References 5 publications

Characteristics of Insulation Diagnosis and Failure in Gas Turbine Generator Stator Windings

Characteristics of Insulation Diagnosis and Failure in Gas Turbine Generator Stator Windings

Assessment of Insulation Deterioration in Stator Windings of High Voltage Motor

Performance Analysis of Increased Safety HT Induction Motor with Higher Stator Coil Pitch for Classified Hazardous Area

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