Title :
UHF technique for identification of partial discharge in a composite insulation under AC and DC voltages
Author :
Sarathi, R. ; Koperundevi, G.
Author_Institution :
Dept. of Electr. Eng., Indian Inst. of Technol Madras, Chennai
fDate :
12/1/2008 12:00:00 AM
Abstract :
DC power transmission is gaining considerable importance and converter transformers form an important component in it. An insulation of these transformers is stressed by both ac and dc voltages. Particle contamination is one of the major problems in insulation structures as it generates partial discharges (PD). If a particle is moving between the ground electrode and barrier, the magnitude of partial discharges formed is less compared to that of its movement between two metal electrodes. On the other hand, when the particle is lying over the barrier insulation material, it does not lead to any partial discharge activities as observed under ac/dc voltages. Broadband measurement of UHF signals produced by partial discharges due to particle movement in transformer oil under dc voltages, at high applied electric fields, indicates that the frequency content of the signal lies in the entire UHF range of 300 MHz - 3 GHz. Narrow band measurements of UHF signal due to PD formed by particle movement, at 1 GHz, indicates that, in the presence of barrier, an increase in applied voltage results in increase in number of partial discharge pulses. This phenomenon occurs in converse in oil gap without any barrier. In the presence of barrier, the sequential movement of particle occurs and the magnitude of discharges increases with increase in applied voltage, irrespective of polarity of the dc voltage. The number of discharges that occur under ac voltage is high compared to the dc voltages.
Keywords :
DC transmission networks; composite insulating materials; partial discharge measurement; power transformer insulation; transformer oil; DC power transmission; barrier insulation material; broadband measurement; composite insulation; converter transformers; frequency 300 MHz to 3 GHz; insulation structures; narrow band measurements; oil gap; partial discharge; particle contamination; particle movement; transformer oil; Electrodes; Partial discharge measurement; Partial discharges; Particle measurements; Pollution measurement; Power transformer insulation; Power transmission; Pulse measurements; UHF measurements; Voltage; Partial discharges, UHF sensors, oil insulation, power transformer insulation;
Journal_Title :
Dielectrics and Electrical Insulation, IEEE Transactions on
Conference_Location :
12/1/2008 12:00:00 AM
DOI :
10.1109/TDEI.2008.4712677