Influence of the Load on the Impulse Frequency Response Approach Based Diagnosis of Transformer’s Inter-Turn Short-Circuit

Abstract

Frequency Response Analysis (FRA) is an Off-line condition monitoring technique for the transformers and is successful, in diagnosing mechanical faults and inter-turn short-circuits. Only limited literature is available for On-line FRA works, and the effect of the transformer's load on the fault diagnosing capability of FRA has not yet been analysed. Motivated by this research gap, an experimental investigation was done to analyze the effect of load on IFRA based inter-turn short-circuit diagnosis. A single-phase 1 kVA, 240V/240 V transformer supplying R and R-L loads and a three-phase 5 kVA, 440 V/440 V transformer supplying an induction motor at various load levels were tested. Inter-turn short-circuits were emulated in their windings and, the effectiveness of IFRA in diagnosing the same was investigated. Comparisons were made between the frequency response of the loaded transformers in their healthier conditions and emulated fault conditions, based on the transfer function plots and the statistical parameters. Investigations reveal that the loads alter the useful spectrum of IFRA. The frequency response of the healthier transformer itself varies based on the transformer's load and necessitates a careful focus on the sensitive frequency spectra for effective inter-turn short-circuit diagnosis in loaded transformers.

Diagnostic Value of Color Doppler Ultrasonography in Subacute Thyroiditis

“…This study suggests that the part with more blood flow signal distribution may be the lesion in the early recovery state, while the area with significantly reduced echo has less blood flow distribution due to heavy inflammatory reaction and obvious interstitial edema. Doppler measurement shows that the arterial blood flow in the lesion is characterized by low resistance and low speed [ 17 ]. At the same time, although some patients will have increased thyroid hormone levels in the blood in the early stage of the disease, the increase is mild, which is reflected in the limited echo reduction type, and the speed of the superior thyroid artery on the lesion side is not significantly higher than that of normal.…”

Detection of Interturn Short-Circuit Faults in Dry-Type Voltage Transformers Using the Pulse Voltage Method

“…Turn-to-turn short-circuit faults in dry-type air-core reactors were tested using the impulse voltage approach described in [23][24][25]. The authors of [26][27][28][29][30][31] used the impulse voltage method to inspect the turn-to-turn insulation of transformers. The impedance and inductive resistance of dry-type voltage transformers are substantially higher than those of other types of coil equipment; the impedance is too high to produce an oscillation test voltage, and the inductive resistance is too high to cause the oscillation frequency to be low, obscuring the detecting effect.…”

Extended Application for the Impulse-Based Frequency Response Analysis: Preliminary Diagnosis of Partial Discharges in Transformer

“…Both simulation and experimental works on transformer winding models were reported in the literature [15]- [17]. In the previous article of the authors, the influence of the load on the Impulse Frequency Response Approach based diagnosis of the inter-turn short-circuits in small scale transformers (1 kVA, 240 V/240 V, 1phase & 5 kVA,440 V/440 V, 3 phase) were reported [18]. The standardization of procedures for the electrical fault diagnosis is still, underway.…”