Detection of Stator Winding Insulation Failures:On-line and Off-line Tests

The aim of this paper is to present a comprehensive review of the scientific literature in this field, including not only research papers but also existing standards for off-line tests.

Experlments for the Ufe Assessment of Generator Bars

In order to estimate the remaining life of a hydro power plant generator bars in Iran, one  new and  four old stator ban of the generator are tested under combined electrlca], thermal and mechanical aging stresses. Partial discharge quantity (total integrated charge of the ban in cooling-down period) before and during the aging is used for the life assessment.

Online Monitoring – Early detection and diagnosis of initiating damages in turbo generators

To minimize loss of revenue, it is helpful to use online condition monitoring and diagnosis systems to receive information about the state of the machine during operation. This will lead to condition based maintenance with extended operating periods in between stand stills.

On-Line Partial Discharge Measurement in Hydrogen-Cooled Generators

Hydrogen-cooling has many advantages, but one of the important features is the suppression of partial discharge (PD) activity by the hydrogen gas at high pressure. On-line PD testing is widely used to determine the condition of the insulation in air-cooled windings, but there has been some controversy about the effectiveness of on-line PD testing to detect insulation problems in hydrogen-cooled machines. This paper will present a statistical summary of on-line PD measured on over 1000 hydrogen-cooled turbine generators

Partial Discharge Detection During Electrical Aging of Generator Bar Using Acoustic Technique

Partial discharge is of the most powerful and important means to diagnose insulation health in generator bar. There are many methods available to detect the PD activity in generator bar. Acoustic detection as a partial discharge detection method has wide range of applications. Acoustic method versus electrical detection methods has several advantages such as immunity against electromagnetic fields. In this paper, an air-cooled generator bar (15.75  kV nominal voltage) is aged under electrical stress. Electrical aging test is carried out according to IEEE 1553-2002.

 PD Detection and Localization bv means of Acoustic Measurements on Hydogenerator Stator Bars

Acoustic partial discharge detection appears useful for the location of PD sources within various kinds of insulating systems. The usefulness of such a method to locate discharge sources in hydrogenerator stator bars is illustrated. The adopted measuring procedure, based on two piezo-electric transducers positioned on a bar, allows the identification of the discharge site position within an error range of ~2 cm

PD-Source Recognition in Generator Bars using a High-Voltage Coaxial-Type High-Pass Filter

A high-voltage coaxial-type high-pass filter is reconstructed and used to detect different impulse forms in generator bars. The test results of an old generator bar shows simultaneous occurrence of different discharge impulse forms. In this paper, the error of the band-pass filter used for PD measurement in delaminated aged bars is presented. It is essential to measure both discharge magnitude and discharge pulse forms to minimize the error.

Practical Application Of Stator Winding On-Line Partial Discharge Monitoring In The Petrochemecal Industry

The stator winding insulation in petrochemical plant motors and generators have been assessed using routine on-line partial discharge (PD) testing for at least 20 years, starting in chemical plants in the US Gulf Coast. Case studies from petrochemical industry machines are presented to show how machines with insulation  problems can be identified using both the trend in PD over time and the absolute magnitude of the PD.

Recent Developments In IEEE And IEC Standards For Off-Line And On-Line Partial Discharge Testing Of Motor And Generator Stator Windings

IEEE and the International Electrotechnical Commission (IEC) have created standards called recommended practices or technical specifications to address offline and online PD measurement using electrical diagnostic equipment, and optical measurement of surface PD. They explain testing objectives and principles, discuss commonly-used methods for measuring PD, and provide guidance for data interpretation.

What Can Go Wrong During Stator Coil Partial Discharge Measurments According To IEC 60270

Spurious PD could be due to proximate sparking of imperfectly earthed objects, loose connections in the area of the high voltage, electromagnetic radiation, contact noise, broadband noise or loosely applied slot simulating earthing fixtures. Various international standards recommend adjustment of frequency bandwidth to acquire genuine PD signals by enhancing the signal-to-noise ratio. IEEE Std. 1434-2000, suggests an acquisition frequency of 2 MHz with adjustable bandwidth.

Pulse Sequence Analysis of Partial Discharge during Accelerated Aging of Generated Bars

In this work, PD monitoring during accelerated aging of generator bars is experimented, pulse sequence analysis of the PD signals is applied for data processing and the aging process of the generator bars is studied. The results show that the method is capable to clarify the aging phase of the test objects containing multiple PD sites.