Investigation on no load mechanical endurance and electrical degradation of a circuit breaker model under short circuit current interruption [Elektronische Ressource] / vorgelegt von Thanapong Suwanasri

Thanapong

Informations

• Publié par: rheinisch-westfalischen_technischen_hochschule_-rwth-_aachen
• Publié le: 01 janvier 2006
• Nombre de lectures: 27
• Langue: English
• Poids de l'ouvrage: 8 Mo

Extrait

Thanapong Suwanasri


Investigation on No-load Mechanical
Endurance and Electrical Degradation
of a Circuit Breaker Model under
Short Circuit Current Interruption














Investigation on No-load Mechanical Endurance
and Electrical Degradation of a Circuit Breaker
Model under Short Circuit Current Interruption




Von der Fakultät für Elektrotechnik und Informationstechnik
der
Rheinisch-Westfälischen Technischen Hochschule Aachen
zur Erlangung des akademischen Grades eines
Doktors der Ingenieurwissenschaften
genehmigte Dissertation


vorgelegt von


Thanapong Suwanasri, M.Sc.
aus Bangkok, Thailand


Berichter: Univ.-Prof. Dr.-Ing. Armin Schnettler
Univ.-Prof. Dr.-Ing. Hans-Jürgen Haubrich

Tag der mündlichen Prüfung: 8. Februar 2006

Diese Dissertation ist auf den Internetseiten der Hochschulbibliothek der
RWTH Aachen online verfügbar.

Acknowledgement

This thesis has been written during my time (2001-2005) as a scientific staff at the
Institute of High Voltage Technology of Aachen University of Technology. Within
these years, I have received a lot of help and support from many parties and I would
like to express my deep appreciation to them.
First of all I would like to thank Univ.-Prof. Dr.-Ing. Armin Schnettler for offering
me the opportunity to pursue my doctoral degree under his supervision, his
professional guidance, patience, encouraging, enthusiasm and support. Furthermore
I am extremely grateful to Univ.-Prof. Dr.-Ing. Hans-Jürgen Haubrich, who kindly
accepted the responsibility for being a co-supervisor.
My appreciation is extended to Univ.-Prof. Dr.-Ing. Rolf H. Jansen for his
encouraging and offering a chance for Thai students to study at RWTH-Aachen
University. Financial support from Siemens AG (Germany) during this research
project is specially acknowledged.
My thanks are also extended to my colleagues, especially Dr.-Ing. Christian
Cornelissen, Dipl.-Ing. Robert Dommerque, Dipl.-Ing. Lutz Hulka, Dipl.-Ing.
Michael Schmale, Dipl.-Ing Michael Schwinne, Dipl.-Ing Christoph Kahlen and all
the other colleagues for their impressive friendship and help during my work at the
Institute of High Voltage Technology.
I am indebted to all staffs in the workshop, especially Leo Künzer and Helmut
Liedecke, for their valuable help and prompt support throughout my work with their
great patience in the preparations of testing facilities in a laboratory.
My greatest gratitude must go to my parents and my brother, who has taken a good
care of my parents all the time and especially during my time in Germany, and my
best friend Miss Ruchada Wissanuwong. Their love, greatest motivation and
constant support have played a vital role behind my work and make me proud and
honor of being a part of the family.
Last but not least, I wish to thank Mr. Pornchai, Mr. Tonglor, Kittipong, Chadchai,
Chanchai, Cattareeya, friends in Aachen and in Thailand and the others who have
not been mentioned here for their encouragement as well as support.


Aachen, in February 2006

Thanapong Suwanasri



Abstract
The demand on reducing circuit breaker failure, extending service life, increasing equipment
reliability and lowering the related operating and maintenance costs are nowadays of prime
importance for the electricity supply network. According to statistics, the major failure mode is
originated from operating mechanism, whereas interrupter has the highest percentage of failure
in high voltage component. Thus, the method to facilitate the assessment of internal
mechanical conditions by using commercially available devices without opening major parts
and the experimental investigation on electrical erosion inside the interrupter were performed
in this work.
The experimental investigation on the mechanical endurance of operating mechanism up to
6,000 no-load switching was performed with 110kV puffer type circuit breakers due to its
requirement of large driving energy for hydraulic operating mechanism. The conventional
measurement, e.g. coil current, contact timing, dynamic contact resistance and pumping motor
current as well as additional vibration technique were carried out in both laboratory and field
test. The investigation on electrical erosion focusing on aging of nozzle and electrode under
current interruption was performed with a reduced-size SF self-blast circuit breaker model and 6
synthetic test circuit, providing the current density comparable to that in the real circuit
breaker, because of the extensive use of nozzle ablation, the possibility for parameters
variation and the reduction of cost and time.
For mechanical investigation, the parameters were measured at the beginning as a reference
and also thereafter every 500 switching under normal and variable operating conditions, e.g.
variation of auxiliary supply voltage, hydraulic oil pressure and SF gas pressure. The test 6
result was verified by that from two of the same type circuit breakers and the theoretical
calculation for vibration result in the frequency-domain analysis. Subsequently, the on-site
measurement before and after maintenance and some simulated defects were executed. The
electrical aging investigation was performed by successive tests with constant energy stresses
until interrupting failure occurred. The effect of current amplitude, nozzle diameter, expansion
volume, arcing time and recovery voltage on mass losses, geometry changes of nozzle and its
influence on pressure build-up were investigated.
The analysis of vibration signals in a combination with the other supervised parameters
provides the useful information regarding the significant events occurring inside during circuit
breaker operation, e.g. motion start of mechanism and within pole, contact touching and
motion stop. The deviations of these measured values from the reference according to number
of no-load switching operations, variable operating conditions and some incorporated defects
were comprehensively determined. The relationship between the gradual changes in technical
status of the supervised components and the number of no-load operations is helpful for
selecting the proper maintenance method.
Regarding the electrical erosion of the nozzle and the electrodes, the mass losses per switching
and per energy; and the geometry change of nozzle especially between the arcing column and
the expansion chamber were investigated. Moreover, volume loss and mass loss along the
nozzle column; its effect on the pressure build-up reduction; and the dependences of mass
2losses on interrupting current amplitude, ∫idt and ∫i dt; have been determined. Furthermore by
applying the wear equivalent law, the allowable number of interruption in function of the
breaking current to rated short-circuit current ratio and the remaining lifetime can be
determined. This result will be used to verify the accuracy of simulation tools in order to
visualize the aging process, to evaluate the interrupter condition and to minimize the expensive
experiment tests.


Untersuchungen zur mechanischen Leerlauf-Dauerbeständigkeit und der elektrischen
Abnutzung eines Leistungsschaltermodells bei Lichtbogenbeanspruchungen
Kurzfassung
Die Verringerung der Komponentenausfallrate, die Verlängerung der Nutzungsdauer, die zu-
nehmende Zuverlässigkeit und die Senkung der Betriebs- und Instandhaltungskosten spielen
heute eine wichtige Rolle für das elektrische Versorgungsnetz. Bei Hochspannungs-Leistungs-
schaltern ist statistisch der Antrieb die Hauptursache eines Fehlers, während die Unter-
brechereinheit die höchste Ausfallrate der Aktivteile aufweist und bei modernen SF -Selbst-6
blasschaltern zudem einem Degradationseffekt unterliegt. Demzufolge wurden in dieser Arbeit
der innere mechanische Zustand eines Leistungsschalters mit Hilfe handelsüblicher Diagnose-
verfahren bestimmt und experimentelle Untersuchungen der elektrischen Abnutzung innerhalb
einer Unterbrechereinheit durchgeführt.
Bei der experimentellen Untersuchung der mechanischen Leerlauf-Dauerprüfung mit bis zu
6.000 Schaltungen wurde ein 110kV-Blaskolben-Leistungsschalter mit hydraulischem Antrieb
genutzt, da dieser Schaltertyp eine relativ große Antriebskraft besitzt und somit üblicherweise
eine höhere Ausfallrate aufweist. Messungen der Spulenströme, der Schaltzeiten, des dynami-
schen Kontaktwiderstandes und des Pumpenmotorstroms sowie die Vibrationscharakteristiken
wurden im Labor und bei den Vor-Ort-Messungen durchgeführt. Die experimentelle Bestim-
mung der Abnutzung der Düsen und der Elektroden bei Lichtbogenbeanspruchungen wurde
mit einem SF -Selbstblasschalter-Modell untersucht. Dabei wurden die geprüften Stromdichten 6
denen kommerzieller Selbstblasschalter angepasst.
Für die mechanische Untersuchung wurden die Messgrößen zu Beginn der Untersuchungen als
Referenz herangezogen. Nach jeweils 500 Schaltungen unter