Reducing frequency domain spectroscopy measurement time for condition monitoring of transformer oil‐paper insulation using non‐sinusoidal excitations

Diagnostic challenges in dielectric loss assessment and interpretation: a review

“…In recent years, the increase of commercially available test equipment and further the improvement in understanding of associated physical phenomena, influence scientific communities and research engineers to apply the polarisation-based technique extensively in DDF measurement. This continuous rise of interest indeed facilitates interpreting the measurement in either the time or the frequency domain [13,14,17,34]. The dielectric phenomena observed under exposure to a considerable electric field are described by the polarisability of the material and are well-reported in the literatures [31,58,59].…”

“…Dielectric response or spectroscopy measurement has aroused the continual interest in diagnosing the deteriorated insulation of HV apparatus. On the basis of the polarisation of material, the measurement can be performed in either the time or the frequency domain [13,75]. In this technique, not only dielectric properties are determined at the service frequencies but also the loss factor or resistance is measured at non-service conditions (e.g.…”

“…Technically, using a Fourier or Laplace transform the responses are translated from the time domain to the frequency domain. In this technique, dielectric properties due to the physical process of polarisation are assessed and quantified over a wide range of frequencies [13,14,39]. For sinusoidal excitation, this method studies the measurement of the magnitude and phase of the current waveform.…”

“…For obvious reasons, condition assessment of materials needs to be performed regularly. In fact, regular monitoring or diagnosing of any system is presumed to reduce its outage times [1,[11][12][13][14]. This must necessarily be done at a considerable voltage level, so that electrical stresses from testing can simulate various effects that usually occur during operation [11,[15][16][17].…”

Physical Model for Frequency Domain Spectroscopy of Oil–Paper Insulation in a Wide Temperature Range by a Novel Analysis Approach

“…It is widely accepted that the dielectric response current in an alternating electric field is led by charge motions such as polarization and conduction [6], and these motions' characteristics are significantly different in the frequency domain. For polarization, related research indicates that the relaxation polarization types with relatively long polarization times, which will cause energy loss, mainly occur in the testing frequency range of FDS (usually from 10 −3 to 10 4 Hz) [7], and the generation of relaxation is due to the charge's barrier-hopping motions [8]; according to the dominant charge types, relaxation polarizations can be divided into space charge relaxation, interfacial relaxation, dipole relaxation and so on [9]. Meanwhile, the conduction process in dielectrics such as cellulose has been proven to be led by ions, and Dyre's work reveals that the conduction of polymers under AC voltage obeys the same mechanism as polarization, namely a trap-hopping motion of the charge [10].…”