A Study on the Hot Spot Temperature in 154kV Power Transformers

Abstract

-The life of a power transformer is dependent on the life of the cellulose paper, which influenced by the hot spot temperature. Thus, the determination of the cellulose paper's life requires identifying the hot spot temperature of the transformer. Currently, however, the power transformer uses a heat run test is used in the factory test to measure top liquid temperature rise and average winding temperature rise, which is specified in its specification. The hot spot temperature is calculated by the winding resistance detected during the heat run test. This paper measures the hot spot temperature in the single-phase, 154kV, 15/20MVA power transformer by the optical fiber sensors and compares the value with the hot spot temperature calculated by the conventional heat run test in the factory test. To measure the hot spot temperature, ten optical fiber sensors were installed on both the high and low voltage winding; and the temperature distribution during the heat run test, three thermocouples were installed. The hot spot temperature shown in the heat run test was 92.6℃ on the low voltage winding. However, the hot spot temperature as measured by the optical fiber sensor appeared between turn 2 and turn 3 on the upper side of the low voltage winding, recording 105.9℃. The hot spot temperature of the low voltage winding as measured by the optical fiber sensor was 13.3℃ higher than the hot spot temperature calculated by the heat run test. Therefore, the hot spot factor (H) in IEC 60076-2 appeared to be 2.0.

Effects of voltage harmonic on losses and temperature rise in distribution transformers

“…where k h and k e are constants of the core material and n is also material dependent (in the range from 1.5 to 2.5). To separate the no-load loss into eddy-current loss and hysteresis loss, B m in (14) is kept constant by maintaining the ratio (V/f) unchanged in (15). Apply this constraint for the ratio of r, then:…”

“…In addition, it is difficult to predict and locate the hottest spot in the transformer. One solution is to measure temperature rise in transformers windings with distributed optical fibre sensors embedded along the windings [13,14]. However, it is costly and so its application is limited to large rating station transformers.…”

Estimation of Loss of Life due to Hot Spot Development in Power Transformer using MATLAB

“…al. [7] have estimated the hot spot temperature in the power transformer by the optical fiber sensors and validated it by the conventional heat run test. Gouda et.…”

A New Support Vector Machine Model Based on Improved Imperialist Competitive Algorithm for Fault Diagnosis of Oil-immersed Transformers

“…In the past few years, some monitoring methods, including windings displacement [2] and hot spot temperature [3], were applied to detect faults of oil-immersed power transformers, however DGA is still a more convenient and effective online monitoring method comparing to the above methods [4]. If an oil-immersed transformer is subjected to electrical or thermal stress, some gases, emitting from its oil-paper insulation system, mainly including H 2 , CH 4 , C 2 H 6 , C 2 H 4 and C 2 H 2 , can be regarded as a symbol of a potential fault [5].…”