Substation Ac Loop Detection Technology

With the development of power system and application of digital equipments, the task of the adjustment and test for the secondary loop is quite heavy, especially with the building of new substation, replacing old equipments and substation maintenance. The secondary loop not only serves the measurement and metering of power system, but also it is important for relay protection.The paper firstly summarizes the present secondary loop test in substation, pointing out its characteristics and defects, and proposes a new substation ac loop test method. This method could test the secondary ac loop when the equipments are not powered on, and check the loop of CT, PT and their polarization.In order to deal with the difficulty of measuring weak current and voltage signals when the equipments is not powered on, the paper investigates the advanced weak signal detection and digital signal processing techniques, and proposes the plan on how to measure the ac weak signal in power system.Finally, the paper develops a test instrument that could measure weak current and voltage in power system, and it could check the ac loop in substation. The application of new method and test instrument could improve the ability of testing ac loop in substation, and it has the potential to be widely applied.