油浸式配电变压器分布式热路模型

Distributed Thermal Circuit Model of Oil-immersed Distribution Transformers

变压器运行时的热点温度与其绝缘寿命息息相关,是变压器负载最关键的限制因素。为此以配电变压器的散热结构为基础,将变压器油看作绕组的外界环境重点关注绕组层间的散热过程,从而建立了油浸式配电变压器的分布式热路模型。通过该模型可计算出热点温度,获取热点位置。并以100、315和400kVA柱式变压器的相关参数为依据,对所建模型的准确性进行了校验。在额定运行条件下,模型计算结果与变压器温升试验报告中实测的绕组平均温升间的偏差在5%以内,验证了模型的准确性。负载导则法计算出的热点温度略高于模型计算值,而负载导则法留有一定裕度,因此对比结果进一步验证了模型的有效性。模型计算结果表明靠近铁芯与靠近油流的绕组温度较低,中间层绕组温度较高;额定运行条件下不同层绕组的最大温差可达10℃以上。

The hot spot temperature is closely related to the insulation life of transformer and is the most critical limiting factor for transformer loads. Consequently, we established a distributed thermal circuit model of oil-immersed distribution transformers based on the real heat dissipation structure of transformer. In the model, the transformer oil is regarded as the external environment of the windings and the heat dissipation process between the winding layers is mainly focused on.Therefore, both of the temperature and position of the hot spot can be obtained through the model. And the accuracy of the model is verified based on the parameters of the 100 kVA, 315 kVA, and 400 kVA pole-mounted transformers. In the rated operating conditions, the difference between model outputs and the measured average temperature rise of the windings obtained through the temperature-rising test report is small, which has proved the accuracy of the model. What is more, the hot spot calculation results of the model are slightly lower than the calculating values of the load guidance method. The comparison results further verify the effectiveness of the model for a certain margin exists in the load guidance method. The model outputs reveal that the temperature of the winding near the core and close to the oil flow is lower than that in the middle layer and the maximum temperature difference between the different layer winding can reach10 ℃ in the rated operating conditions.