基于冻土校验的变电站接地网设计

Design of Substation Earthing Network with Frozen Soil Verification

研究和测试表明,土壤凝结成冻土时,其电阻率可增加5~1000倍。在冬季,土壤由浅入深逐步形成冻土高阻层,直到最大冻结深度;在春季反之,冻土高阻层由表入里的消散。在这个周期变化的过程中,冻土深度内的土壤电阻率产生剧烈变化,对变电站接地网的性能产生动态、显著的不利影响,提高了GPR和降低了接触电压允许值。当前,在变电站接地的工程设计中,对此鲜有相关的研究和应用。廊坊柳林220 kV变电站作为重点工程,采用分层土壤模型等效实际冻土条件,首次对接地网的性能进行了工程量化的评估和校验。测试结果表明,采用分层土壤模型等效的方式是可行的,冻土校验和评估涉及安全性评估,是必要的。

Studies and tests have shown that the resistivity of soil increase 5 to 1000 times when it condenses into permafrost.In winter,the soil gradually forms a high resistance layer downwards along vertical direction until the permafrost depth;in spring,the formed high resistance layer dissipates downwards.In the process of this cycle,the soil resistivity within the depth of the permafrost undergoes dramatic changes.And then,the impact that the performance of the substation earthing network by frozen soil will be significant.Currently,there are few relevant studies and applications in engineering design.Langfang Liulin 220 kV substation,as a key project,adopts a layered soil model,equivalent to actual frozen soil,and carries out the quantitative evaluation and verification of the performance of the earthing network for the first time.The test shows that it is feasible to adopt the layered soil model equivalent method,and it is necessary to carry out permafrost calibration and assessment,involving safety assessment.