Partial discharge on-line measurements with continuous monitoring as invaluable tool for assessing insulation quality and maintenance planning (original) (raw)
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ADVANCES IN INTERPRETING PARTIAL DISCHARGE TEST RESULTS FROM MOTOR AND GENERATOR STATOR WINDINGS
On-line partial discharge (PD) testing has been used for decades to help maintenance personnel detect stator winding insulation problems in motors and generators. Specifically, the test can often find loose, delaminated, overheated, and contaminated windings, well before these problems lead to failure. As a result, on-line PD testing has become an important tool for planning machine maintenance. The test has also found use in determining the effectiveness of any manufacturing or repair work. With the advent of electrical noise separation technology developed in the 1970s and 1980s, reliable on-line PD testing and basic interpretation was made possible by plant engineering staff with moderate training. The result has been the widespread application of the so-called PDA and TGA tests on machines throughout the world. Over 50% of utility generators rated over 20 MW in the USA and Canada now use this technology. This widespread application has enabled the collection over the past ten years of a database with nearly 30,000 test results. The results of a statistical analysis of the PD results in this database shows that voltage class, machine cooling method, and type of partial discharge detector all are critical to interpreting test results, whereas machine power rating, insulation type and age of the winding are less important. Critical values of PD, which indicate significant risk of severe winding problems, are presented for different types of air-cooled and hydrogen-cooled machines. Thus comparison of test results to the database allows a rough assessment of the stator winding insulation condition, without having to wait a few years for a trend to establish itself. However, the best assessment of the winding condition is still obtained from the trend in PD on a single machine over time. A doubling of the PD magnitudes every 6 months, under similar operating conditions is a consequence of a rapid rate of insulation deterioration. This paper shows that the PD is affected by machine operating conditions. Thus to obtain valid trends in PD data, the testing should be performed under similar operating and environmental condition
Partial Discharge Theory and Technologies Related to Medium-Voltage Electrical Equipment
—Partial discharge (PD) monitoring is an effective on-line predictive maintenance test for medium-voltage (MV) motors, MV generators, and MV switchgear at 4160 V and above, as well as other electrical distribution equipment. The benefits of online testing allow for equipment analysis and diagnostics during normal production. Corrective actions can be planned and implemented, resulting in reduced unscheduled downtime. An understanding of the theory related to PD, and the relationship to early detection of insulation deterioration is required to properly evaluate this pre-dictive maintenance tool. This paper will present a theory to promote the understanding of PD technology, as well as various implementation and measurement techniques that have evolved in the industry. Data interpretation, corrective actions, and application to electrical distribution equipment will also be reviewed.
2007 9th International Symposium on Signal Processing and Its Applications, 2007
The Oil/Gas industry is facing two major problems with its aging electric power generators. First, the Oil/Gas industry experience long outages of these power generation units for re-winding, during a time when power is extremely needed. Second, these fixed-interval scheduled maintenance practices are very costly as on average they cost around US$1 million per machine. To address these problems, we propose to develop an effective, reliable and automatic signal processing based technique to monitor the insulation condition of electric machines.
Advantage of On-Line Partial Discharge continuous monitoring of medium voltage substation
2009 IEEE Electrical Insulation Conference, 2009
On-Line Continuous Partial Discharge measurements of medium voltage substations have not attracted the same attention in the electrical community as compared to similar PD measurements of rotating machines. The cost of an unexpected outage however may be considerably more significant of a main distribution bus than just for a single motor failure. This paper discusses pros and cons of PD measurements using multiple sensors for additional noise reduction and localizing PD activity for measurements made in higher frequency bands. The importance of continuous PD monitoring vs. periodic walk in PD measurements of switchgear is also discussed considering that PD activity in switchgear can have very unstable activity highly dependent on ambient conditions. Negative periodic PD tests in switchgear can result in a false sense of security. Case studies from field experience are presented to support the discussions.
Detection of Partial Discharge Activity in H.V Rotating Equipment
Insulation property play important role in H.V rotating machine. Detection and monitoring of partial discharge activity gives a information about quality of insulation. It gives a indication of insulation deterioration. Partial discharge detects the points of degradation of insulation. (i) HFCT (ii) HVCC (iii) TEV (iv) Rogowski Coil(RC) sensor are used for detection and monitoring of partial discharge activity. By using this sensors PD activity detect and monitor the condition of insulation of the machine without interrupting the running of machine.
Testing and Monitoring Methods for Stator Insulation Systems
A breakdown of the electrical insulation system causes catastrophic failure of the electrical machine and brings large process downtime losses. To determine the conditions of the stator insulation system of motor drive systems, various testing and monitoring methods have been developed. This paper presents an in-depth literature review of testing and monitoring methods, categorizing them into online and offline methods, each of which is further grouped into specific areas according to their physical nature. The main focus of this paper is on testing and monitoring techniques that diagnose the condition of the turn-to-turn insulation of low-voltage machines, which is a rapidly expanding area for both research and product development efforts. In order to give a compact overview, the results are summarized in two tables. In addition to monitoring methods on turn-to-turn insulation, some of the most common methods to assess the stator's phase-to-ground and phase-to-phase insulation conditions are included in the tables as well.
NEW TOOLS FOR DIAGNOSTIC MEASUREMENTS ON ELECTICAL ROTATING MACHINES
michael.krueger@omicron.at Rotating machines are important and expensive assets in electric power systems. Recurring diagnostic measurements on the electrical insulation of stator and rotor are important to ensure the safe operation and prevent unexpected outages and serious failures. Common practise for the insulation diagnosis is the measurement of the Polarisation Index (PI), the measurement of the capacitances and dielectric losses and the measurement of partial discharges (PD). Innovative tools like the dielectric response analysis or the partial discharge measurement with synchronous multi-channel systems enable a more detailed analysis of the insulation quality and the location of faults. The dielectric response analysis of the insulation with Polarisation / Depolarisation Current (PDC) and Frequency Response Spectroscopy (FDS) can detect moisture and ageing problems much better than measuring the PI only. With PD systems which can measure simultaneously at different points, ...
The Impact of Insulation Monitoring and Diagnostics on Reliability and Exploitation of Service Life
2006
SUMMARY The progress in automation and information technology has led to substantial improvements of existing and introduction of totally new monitoring and diagnostic systems. Normally those systems are applied for costly pieces of equipment as gas insulated substations (GIS), power transformers and power cable systems. Since the dielectric properties are the main criteria regarding the service performance of this type of equipment, insulation monitoring and diagnostics are considered mainly. The application of those systems is also of special interest with respect to insulation coordination. Insulation monitoring and diagnostics generally aims at two fields of application, first the detection of incipient faults and secondly exploitation of service life. The detection of incipient faults is mainly of interest to reduce the failure rate furthermore thus decreasing the outage time as far as possible, since a failure during operation in the equipment under consideration mostly causes...
Measurement and Detection of Partial Discharge in Power Systems
Power systems are the life line of the 8.3 billion people who currently inhabit the world. As the population of the world increases the need for power system protection and maintenance and up gradation is of grave importance to both electrical utility companies as well as end consumers. In the context of power system protection, insulation plays a pivotal role in isolating the transmission lines from the external environment in which they were present. This makes the study of insulation or dielectric breakdown even more important because transmission lines run into several hundreds and in some cases thousands of kilometres. Hence we shall be enlisting the need for partial discharge detection devices; so that insulation failure can be detected on line and be given attention by engineers for due replacement and or maintenance. Most incipient faults are due to partial discharge and this phenomenon has many effects on the health of the system, hence measurement and detection are an important step in taking corrective action
A survey of testing and monitoring methods for stator insulation systems in induction machines
2008 International Conference on Condition Monitoring and Diagnosis, 2008
A breakdown of the electrical insulation system causes catastrophic failure of the electrical machine and brings large process downtime losses. To determine the conditions of the stator insulation system of motor drive systems, various testing and monitoring methods have been developed. This paper presents an in-depth literature review of more than 20 existing methods, including the most common methods to assess the phase-to-ground, phase-to-phase, and turn-to-turn insulation conditions. The methods are categorized into as online and offline methods, each of which are further grouped into specific areas according to their physical nature. The paper focuses on turn-to-turn insulation testing and monitoring of low-voltage machines, which is a rapidly expanding area for both research and product development efforts. Finally, a new approach to online monitoring of turn-to-turn insulation faults for low-voltage induction motors is recommended.