Insulation failure

Analysis of insulation failures of an HT motor at a thermal power station 10/241... 

A powerhouse (thermal) application is the most stringent application, as discussed in Section 7.19. Based on field data collected from various installations by different agencies the general insulation failures observed may be attributed to the following. 

Installation of bearings and pulleys Important checks at the time of commissioning Maintenance of electric motors and their checks Maintenance of bearings General problems in electric motors and their remedy Winding temperature measurement at site Analysis of insulation failures of an HT motor at a thermal power station... 

The third problem associated with water based varnishes is poor electrical insulation properties of the laminate after moisture conditioning. This problem is probably the most critical problem because insulation failures of the laminate can lead to electrical failure of the finished printed circuit board. This property is measured by conditioning the finished laminate in a high moisture environment and then testing the dielectric breakdown strength. ED24574 has excellent insulation resistance. This was achieved by a proprietary resin composition. 

The intentional sparks produced by these machines have also been blamed in a number of surgical drape fires. The high-frequency nature of these therapeutic electrical waveforms also makes it easier for them to become capacitively coupled to other tissue or conductive pathways. Burns due to such coupling and/or insulation failures during laparoscopic procedures are often the result. Since such burns are usually outside the surgeon s visual field, they often go untreated. 

The European safety standards stress an important principle called the singlefault concept that is at the core of safety philosophy. This principle states that even under a single fault (a wire coming loose, component failure, short/open circuit, insulation failure, etc.) at least one level of protection (basic insulation) must be... 

Indirect contact. Protection of personnel from hazards that may arise in the event of an insulation failure (single fault) between live parts and exposed conductive parts. 

PSB2 Prevention of short circuit from exposed parts PSB3 Prevention of short circuit, owing to insulation failure... 

The principle is that the live conductors are covered by two discrete layers of insulation. Each layer would provide adequate insulation in itself but together they ensure little likelihood of danger arising from insulation failure. This arrangement avoids the need for an earth wire. Double insulation is particularly suitable for portable equipment such as drills. However, safety depends on the insulation remaining in sound condition and the equipment must be properly constructed, used and maintained. 

Winokur P, Falkenberg E, Gerard G. Lead resistance telemetry insulation failure prognosticator. PACE 1985 8 A85-A339. 

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