دانلود رایگان ترجمه مقاله الگوی توزیع حرارت در ترانسفورماتور پر شده با روغن (نشریه IEEE 2015)

الگوی توزیع حرارت در ترانسفورماتور پر شده با روغن در موقعیت های متفاوت دمای داغ ترین نقطه

Heat Distribution Pattern of Oil-filled Transformer At Different Hottest Spot Temperature Locations

Abstract

Sustained high temperature on transformer insulation systems is one of the main causes of its accelerated degeneration. Continuous monitoring of transformer heat distribution could provide useful information on intensity and location estimation for hottest spot temperature (HST) development. Furthermore, faults will aggravate the formation of HST inside the transformer tank. However, there is difficulty in measuring and locating HST in many aged in-service transformer because there are no in-tank sensors installed. Thus HST can be monitored by observing the heat distribution pattern in the transformer. Therefore, this paper aims to investigate the effect of HST on the overall transformer temperature distribution and the heat distribution pattern associated with HST. The focus is on the effect of this heat distribution to the surface of transformer tank for condition monitoring purposes. Simulation of mineral oil-filled distribution transformer (ONAN type) was done by using Finite Element Method Magnetism (FEMM) 4.2 where particular interest was on the transformer cross section. Changes of heat dissipation at the inner and outer transformer body tank were analyzed. The results show that the continuous presence of HST increases oil temperatures as well as inner and outer tank surface temperatures. The existence of HST affects the whole temperature distribution pattern inside the transformer. Thus, the transformer HST can be used as indication of potential inside the transformer. The changes of surface heat near to the HST may also be useful in in-service monitoring the transformer condition.

1 Introduction

Transformer temperature is an important indicator used in transformer monitoring [1]. Every internal transformer fault contributes to the irregularities that may be associated to transformer internal temperature [2]. In their study, [3] have written that because the internal temperature of the transformer affects the external surface temperature, it may be difficult to identify HST at its beginning. However, when transformer temperature profiles are developed, the trends can reveal how temperature changes occurring within and around specific locations can eliminate this difficulty.

Transformer heat distribution normally shows that the temperature at the top of the transformer is higher than temperature at the bottom of the transformer [4]. Therefore, when the temperature gradients transformer is plotted from top to bottom, it will have a gradually decrease. This makes it appropriate to use oil temperature at the top of the transformer as estimation for the HST reading inside the transformer [5].

Transformer HST intensity and estimated location can be determined by monitoring the heat distribution. In their publication, [6] has presented that HST in transformers will normally be caused by overloads or faults and thus occurs around the transformer winding and assembly [6]. Furthermore, [7] have presented that harmonic current can also cause overloads and temperature increase.

This paper uses Finite Element Method Magnetism (FEMM 4.2) software to analysis temperature rise caused by HST around the transformer winding. Furthermore, the paper investigates the effect of different HST locations on the overall transformer heat distribution pattern. The HST simulation was done on 100 kVA mineral oil filled ONAN. A cross section of the transformer is developed from [8] and shown in Fig.1. Thus it is worth mentioning that the study focuses on the effect of different HST locations on heat distribution around the outer surface of transformer tank for condition monitoring purposes.