Interferometric optical fiber sensors for measurements within oil-filled power transformers

Abstract

Optical fiber technology is able to answer the demanded development of EMI immune and harsh withstanding sensors for the Electric Power Industry, particularly applied to Power Transformers, and specifically for measurements within them. Apart from temperature, the other main magnitudes of interest are vibrations and partial discharges, which are studied here on the base of the interferometric sensors that we are developing for these purposes. This work is centered on the new concept of interferometric sensing by detecting multi-fringe outputs, which is applied for the measurement of each magnitude independently or both at the same time from only one probe. A high resolution read-out of the optical phase without ambiguity is demonstrated with this approach of demodulation and with the probes designed for monitoring inside power transformers. Results of in-field trials are presented for synchronous vibrations (100 Hz -2 kHz) of two power transformers. First results of calibration of acoustic sensing with these probes on the base of the same interferometric concept are also presented in order to apply them for the measurement of partial discharges by detecting ultrasounds (20 kHz -200 kHz). A multi-purpose exploitation of the sensor heads installed at the core and the windings of a power transformer is explored for detecting at the same time both, vibrations and partial discharge induced ultrasonic pulses. The multi-fringe interferometric output due to vibrations is proposed as a repetitive reference for the demodulation of the higher frequency asynchronous signals.

Power transformer testing

“…However, this measure does not reflect the winding temperature during a sudden increase in the load of the transformer. In order to monitor high-energy transformers, measurements of various physical magnitudes such as temperature [1][ [2] sound [3], gas [4], vibrations [5], partial discharge [6] are made here.…”

Аналіз Вібраційних Процесів Вузлів Турбогенераторів З Урахуванням Режимів Їх Експлуатації

“…У цьому разі перспективним для зняття вібраційних процесів є застосування ємнісних [12][13][14][15][16][17] або оптичних [18][19][20][21][22] сенсорів. Як показали проведені дослідження в [23] застосування ємнісних сенсорів з концентричними плоскопаралельними електродами має ряд переваг, серед яких те, що на їх технічні характеристики CURRENT ISSUES AND PROSPECTS FOR THE DEVELOPMENT OF SCIENTIFIC RESEARCH 308 не впливають хімічний склад, намагніченість та температура поверхні об'єкту дослідження.…”