计及剩磁的空载变压器选相合闸研究

Research on unloaded transformer controlled switching considering residual flux

随机合闸空载变压器产生的励磁涌流容易引起电力变压器差动保护装置误动、绕组机械应力增大以及电能质量降低等问题。采用选相合闸技术来抑制空载变压器励磁涌流。实现空载变压器选相合闸的关键是有效预估变压器切除后铁芯中的剩磁。在分析选相合闸空载变压器原理的基础上,提出基于数值积分的铁芯剩磁测量方法。采用PSCAD/EMTDC软件对变压器空载合闸进行了仿真,仿真结果验证了选相合闸技术的有效性。搭建空载变压器选相投切试验平台,进行了空载变压器随机合闸、选相合闸试验。试验结果表明:与随机合闸相比,计及剩磁的空载变压器选相合闸能够有效地抑制励磁涌流,同时验证了剩磁测量方法的有效性。最后,针对三相联动断路器提出了相适应的空载变压器选相合闸策略,仿真结果验证了其有效性。

Random energization of unloaded transformers may generate inrush currents,which easily causes protective relay mis-operation,imposes sever mechanical stresses on the transformer windings and reduces power quality of the system.Controlled switching technology is used for suppressing these inrush currents.The key to realize controlled switching is the effective estimation of the residual flux in transformer core after a transformer de-energization.Based on the analysis of the theories of controlled switching unloaded power transformer,a method of measuring the residual flux based on numerical integration is proposed.Energization of unloaded transformers is simulated with PSCAD/EMTDC,and simulation results validate the effectiveness of the controlled switching technology.Unloaded transformer controlled switching test platform is built,and the tests of random and controlled switching are conducted.The experimental results indicate that the controlled switching considering residual flux is effective in suppressing the inrush current compared with random switching,and validate the effectiveness of residual flux measurement method.Finally,the suitable controlled switching strategy of unloaded transformer with gang-operated breaker is proposed,and simulation results validate its effectiveness.