Views
4 years ago

in-service partial discharge testing of generator insulation.pdf

in-service partial discharge testing of generator insulation.pdf

in-service partial discharge testing of generator

IN-SERVICE PARTIAL DISCHARGE TESTING OF GENERATOR INSULATION M. Kurtz and G. C. Stone, Ontario Hydro, Research Division Toronto, Canada IEEE Trans. Electr. Insul, Vol EI-14 No 2, April 1979 ABSTRACT Progressive degradation of high-voltage generator insulation, whether due directly to the erosive effects of internal or slot discharge or to other debilitating factors such as heat and vibration, may be detected and monitored as a function of time by in-situ partial-discharge tests. This paper describes new diagnostic test techniques for assessing the condition of generator insulation with a minimum of service interruption. An improved means of coupling or data acquisition is described, as well as a versatile single-channel pulse height analyzer with characteristics adequate for a field application of this type. Some typical test data are given. These studies were sponsored by the Canadian Electrical Association and are presented with their permission. are observed, together with a power-frequency trigger signal taken from one of the filter inputs, on an oscilloscope with a four-channel display as shown in Figure 2. The discharge patterns in Figure 3 are typical of a new and an old winding. Experience shows that as the magnitude of the highest partial discharge pulse increases, damage to the stator insulation also increases. INTRODUCTION Generator insulation systems, however perfect their initial state, inevitably degrade in service. Heat, thermal cycling, bar forces, vibration, mechanical shock, shrinkage of support structure such as wedges and spacers, and the presence of a high electric stress, act and interact to impair the integrity of the dielectric system. At some stage, partial discharges will start or begin to increase, providing an additional erosive aging factor. This usually occurs at abraded outer shielding, in cavities or delaminations, or in the end-turn structure. The number, magnitude and distribution of the partial discharge pulses can conceivably identify predominant aging mechanisms. Changes in these quantities, as a function of machine age, become a measure of cumulative insulation deterioration. “CONVENTIONAL” DIAGNOSTIC TEST A relatively inexpensive technique for the detection and display of partial-discharge pulses in generators has been developed and used by Ontario Hydro for over 20 years for the assessment of stator insulation condition [1]. In its present form, portable discharge-free coupling units, fabricated from approximately 2.5 m looped lengths of single conductor 27.6 kV concentric-neutral power cable are used, one for each phase of the generator as shown in Figure 1. The core conductors of the cables are connected to the generator’s respective terminals at any conveniently accessible point on the machine side of the disconnecting switch. The cable shields, the “low” sides of these high voltage coupling capacitors, are respectively connected, via lengths of shielded coaxial cable, to three five-stage RC high pass filters with a cut-off at about 30 kHz. After the machine is brought up to rated speed and voltage, the filter outputs Fig. 1: Cable-type portable partial-discharge coupling capacitors being connected to the three phase-conductors of a. machine prior to test. Fig. 2: Typical display showing the partial discharges from three phases of a machine and one power-frequency reference signal. Tests are usually done with the machine (a) isolated from the system, (b) synchronized at no load and (c) a full load. In many cases, a skilled operator can distinguish between pulses originating in the machine winding and external noise entering from the power (?). Large differences between the data for the (?) test modes may be caused by movement of bars in response to dynamic forces as the load changes. These movements result in a change in the contact resistance between the bar shielding paint and the iron in the (?). causing discharges in the slot to change. Such (?) are subject

PARTIAL DISCHARGE COURSE - Iris Power Engineering
Digital Partial Discharge Detector - Haefely Test AG
Honeycomb discharge generated with a single high voltage power ...
9530 Digital Delay / Pulse Generator 9530 Digital ... - Qbiclaser.com
Quantum Composer 9530 Series Pulse Generator
Van de Graaff Generator, High Voltage Discharge Sphere Electric ...
SD/HD Video & AES Test Generator - LYNX Technik AG
Best [PDF] The Official Guide to the GRE General Test, Third Edition Best Sellers Rank : #3 Textbooks#D#
experience with in-service partial discharge testing of generator
practical on-line partial discharge tests for turbine generators and ...
on-line partial discharge measurements on turbine generators ...
experience with partial discharge testing - Iris Power Engineering
epri 93 - experience with on-line partial discharge testing of motors ...
a new on-line partial discharge test for turbine generators
Partial Discharge Testing Finds Foreign Object.qxd - Iris Power ...
Using Partial Discharge and Flux Density Testing to Postpone Stator ...
continuous on-line partial discharge monitoring of generator stator ...
Cost/Benefit Analysis For Using Partial Discharge Testing
propagation of partial discharge and noise pulses in turbine
Partial Discharge Testing of Random Wound Stators ... - IEEE Xplore
A Perspective on Online Partial Discharge Monitoring for ...
pas trans 84 - application of partial discharge to hydrogen mtce.pdf
Partial Discharge - Iris Power Engineering
acoustic emission of multisource partial discharges - pta-krakow.agh ...
partial discharge testing: a progress report - Iris Power Engineering
partial discharge testing: a progress report - Iris Power Engineering
Pattern Recognition for Partial Discharge ... - Haefely Test AG
Partial Discharge Diagnostics and Electrical Equipment Insulation ...
Integrated Partial Discharge Testing and Monitoring Solutions