基于热路模型和瞬态伴随模型的直埋电缆暂态缆芯温升计算

Transient Temperature Rise Calculation of Buried Power Cable Based on Thermal Circuit Model and Transient Adjoint Model

随着电力负荷不断增大和供电可靠性要求的不断提高,准确和快速评估直埋电缆的暂态温升有助于提高动态增容和应急负荷工况的管理水平。根据温度场的唯一性,针对复杂的电缆结构和散热环境,建立了等效的二支路暂态热路模型。根据热路和电路的相似性,利用电路中的集总参数网络的瞬态分析方法,建立了热容支路的瞬态伴随模型,给出了暂态热路模型的节点导纳矩阵,根据节点热流写出了节点温升方程。由于暂态热路模型中热容和热阻参数不易计算,利用粒子群优化算法和暂态热路模型的瞬态分析法,通过与有限元和试验暂态温升数据的对比,优化获得了暂态热路模型的热容和热阻参数。由于直埋电缆热传递过程中的延迟特性,建立的暂态热路模型可分为短时模型和长时模型,提高了阶跃负荷下的暂态温升和周期性负荷下的暂态温升的计算精度。试验和有限元计算结果的对比证明了所建立的暂态热路模型具有较高的精度,有助于提高暂态负荷的管理水平。

As the power load and the demand of power supply reliability continue to increase, accurate and rapid evaluation of transient temperature rise is helpful to improvement in the management level of dynamic load and emergency load.According to uniqueness of temperature field, an equivalent two-branch transient thermal circuit model was provided to represent the complex cable structure and environment. Because of the similarity of electrical circuit and thermal circuit, a transient adjoint model of thermal capacity and nodal admittance matrix of the transient thermal circuit model were built by transient analysis method of lumped parameter network in circuit. The nodal temperature rise equation was built too. It is not easy to calculate the thermal capacity of thermal resistance of transient thermal circuit, therefore, the thermal parameters of transient thermal circuit model were obtained by adopting the particle swarm optimization and transient analysis method of transient thermal circuit model. The fitness function of particle swarm optimization is the sum of square of difference between transient thermal circuit model results and finite element analysis results or trial results. Because of the heat transfer delay characteristic of buried power cable, the transient thermal circuit model was separated to short time model and long time model. The transient temperature rise of step current and cyclic current can be calculated accurately and rapidly. The comparison of finite element analysis results and trial results prove that the transient thermal circuit model possesses high accuracy and is helpful to improvement in the management level of transient load.