火电厂中压电缆热稳定最小截面的一种估算方法

Estimation Method for Thermal Stability Minimum Section of Medium Voltage Cables in Thermal Power Plants

在火电厂6~10 kV厂用电系统中,电缆热稳定截面需要依据GB 50217—2018《电力工程电缆设计标准》中规定的方法进行反复验算后确定。当系统中回路较多时,计算量较大。给出了一种电缆热稳定截面的简化方法。通过对短路热稳定条件下电缆导体所允许最小截面的表达式进行变换,并对该表达式进行简化拟合,在系统电源供给短路电流的周期分量起始有效值已知的情况下,可通过求极小值的方式得到最小截面。通过一些工程实例,利用提出的估算方法进行了热稳定截面计算,并与传统推算方法对比。结果表明,估算方法结果准确,可有效减小计算量,提高设计效率。

In the 6-10 kV station service electrical system of the thermal power plant,the cable thermal stability section needs to be determined after repeated verification according to the method specified in GB 50217—2018 Standard for Design of Cables of Electric Power Engineering.When there are too many loops in the system,the work of calculation is very heavy.This paper presented a simplified method for estimating the cable thermal stability section.By transforming the expression of the minimum section of the cable conductor under short-circuit thermal stability conditions,and simplifying the expression,when the initial effective value of the periodic component of the system power supply short-circuit current is known,the minimum section could be obtained by finding the minimum value.By giving some engineering examples,this paper carried out the thermal stability section calculation by using the estimation method proposed,and compared with the traditional calculation method.The results show that the estimation method is accurate and can effectively lighten the workload of calculation and improve the design efficiency.