Investigation of Ideal Anisotropic Material Properties for Outer Corona Protection Systems in Large Rotating Machines

Staubach, Axel; Schmidt, G.; Pohlmann, Friedhelm; Hirsch, Holger

doi:10.1109/eic.2018.8481019

Cited by 2 publications

(2 citation statements)

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“…Recently, the outer corona protection (OCP)of high-voltage electrical machines has received lots of attentions [76]. The OCPs can even out the unavoidable surface roughness and lead to uniform electric field distribution in the insulation system [77]. The impact of anisotropic OCP material is assessed by finite element method (FEM)in [78].…”

Section: Hydro Generatormentioning

confidence: 99%

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Survey of Insulation Systems in Electrical Machines

Hemmati

El-Refaie

2019

2019 IEEE International Electric Machines &Amp; Drives Conference (IEMDC)

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Insulating materials and insulation systems design have been gaining more attentions as more electrical machines tend to operate in harsher environments for various applications. Harsh environments include high temperature, humidity, erosion, low air pressure, etc. This paper discusses recent advances in insulation systems for electrical machines. Insulation tests as well as test standards that have been used to evaluate insulation systems and detect insulation failures will be discussed. Insulating materials used for a wide range of industrial applications such as wind turbine generators, aerospace hybrid/electric powertrain, and hydro generators have been summarized. For the emerging high-altitude, highvoltage aerospace applications, partial discharge and its impact on insulation systems will be discussed. Finally, polymer nanocomposite materials with excellent thermal conductivity and dielectric strength are highlighted as an outlook. SECTION I. Introduction Due to the continued growth of renewable energys, the number of electrical machines used worldwide has significantly increased. Insulation system is a very critical component of electrical machines. Insulation breakdown can lead to failures, which eventually result unpredicted downtime and negative financial impacts and in some applications can be a safety hazard. For some specific industries where uninterruptible operation is required, the unpredicted downtime is unacceptable. The unpredicted downtime for an offshore oil plant would be $25,000/h [1]. The dielectric strength of electrical insulation materials has been gradually improved over the years. By introducing new materials in the past 20 years for instance, the dielectric strength of ground-wall insulation nearly doubled [2]. Electrical, mechanical, thermal, and ambient stresses can cause insulation degradation which consequently leads to insulation failure [3], [4]. Insulation failure causes short circuits in the stator winding and consequently high currents could pass through the defected stator winding [5]. A survey on 1141 induction motors with power ratings above 200 hp shows that around 30% of motor failures are due to insulation failures [6]. With advances in sensors, digital signal processing, diagnosis methods and test standards, insulation failures can be detected [7], [8]. Through online estimation of material degradation and lifetime in early stages, insulation systems of electric machines can be protected from further aging while unpredicted downtime could be avoided through scheduled maintenance. Even though insulation system is a passive component in an electrical machine which does not produce torque, insulation build/thickness (which represents the key thermal resistance in electrical machine)can have significant impact on the machine cooling and hence electrical loading and torque production. There have been several efforts to minimize insulation thickness for design compactness, low manufacturing cost and high efficiency [3]. The two main functions of insulation systems in electr...

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Section: Hydro Generatormentioning

confidence: 99%

“…The impact of the parameters of OCP materials on electric field distribution is presented. In order to identify the ideal properties for OCP materials, a swarm optimization algorithm is adopted [77].…”

Section: Hydro Generatormentioning

confidence: 99%