中文摘要：

为了保障直流系统的安全可靠运行，通常发电厂、变电站使用的直流系统绝缘监测装置是通过检测对称电桥的不平衡程度来反映直流母线的绝缘情况，但当正负母线绝缘均按比例下降时就失效。为此提出了采用常态下利用双不对称电桥实时监测直流系统绝缘的新方法以解决上述问题。同时针对变电站存在严重的电磁干扰易造成绝缘在线监测系统数据的波动大及工作不稳定的问题，在硬件与软件的设计上采用了多项抗干扰措施，如光耦隔离、开关电容滤波器以及数字滤波等，成功消除了测量的随机误差。在介绍了基于该方法的监测装置的设计与实现方法后，进行的实验结果验证了该方案的可行性和有效性。

英文摘要：

To ensure the reliability of DC system, the insulation status of DC bus must be entirely monitored online. Generally unbalanced degree of symmetrical bridge is used as a chief means for reflecting insulation of DC bus, however it becomes disabled when insulation of positive and negative poles of DC bus drops in the same proportion. A new method of real-time supervision for insulation of DC system is adopted in this paper, which uses double asymmetrical bridge in normal mode. The shortcomings of symmetrical bridge are overcome. As the severe electromagnetic interference in the substation, the urgent problem of data fluctuation and instability need to be solved. Therefore, integrated anti-interference methods are achieved in the design of hardware and software, such as opto-isolated technique, switched-capacitor filter, digital filter, etc. And the stochastic error is successfully eliminated. The design and realization of proposed method-based supervising instrument are introduced in detail. Experimental results have proved that the project is quite feasible and effective.