高载流容量电网的主变保护适应性分析

Adaptability analysis of transformer protection in power system with high current carrying capacity

本文分析高载流容量电网的满载负荷电流大幅上升对主变保护产生的系列影响,以实际工程为例,指出边、中开关选用高电流比的电流互感器将影响以固定门槛判别的保护的灵敏性和以故障分量为原理的差动保护的可靠性,且保护定值整定可能出现超过定值上下限的情形。线路载流容量大幅提升后,主变高压侧穿越性负荷电流远大于变压器额定电流,该特性可能造成常规差动保护的可靠性和灵敏性下降。结合工程实施,本文建议主变套管互感器配置主保护、后备保护作为保护冗余方案,以减小高载流容量、高电流互感器电流比的影响。

This paper analyzes the series of impacts on the transformer protection caused by the sharp rise of the full load current of the power grid with high current carrying capacity. Taking the actual project as an example, it points out that the selection of high transformation ratio current transformers for side and middle switches will affect the protection sensitivity judged by the fixed threshold and the reliability of the differential protection based on the fault component principle. At the same time, the protection setting may exceed the upper and lower limits of the setting value. After the current carrying capacity of the line is greatly increased, the through load current at the high-voltage side of the main transformer is far greater than the rated current of the transformer, which may cause the reliability and sensitivity of the conventional differential protection to decline. Combined with the project implementation, this paper suggests that the main protection and backup protection should be configured with bushing transformer as the protection redundancy scheme to reduce the impact of high current carrying capacity and high transformation ratio.