Construction of transient voltage UWB on-line monitoring system in UHV GIL based on capacitive voltage division

The transient voltage process in UHV transmission system has a great influence on the insulation state of Gil equipment. Therefore, in order to monitor the transient voltage process suffered by the UHV GIL during its operation in real time, this paper constructs a transient voltage ultrawideband (UWB) online monitoring system based on capacitive voltage division, which is actual applied in 1100kV Sutong GIL utility tunnel project. The system included voltage sensor, monitoring terminal and storage and control unit. Capacitance sensing transformation is carried out on the cover plate of the GIL. Signal conversion and acquisition are implemented locally at the monitoring terminal, and uploaded to the upper storage control unit through optical fiber. The effective measurement bandwidth of the monitoring system ranges from 2.1Hz to 230MHz, the sampling rate is 250 MS/s, and the analog bandwidth is 100MHz. The abrupt voltage waveform can be accurately captured by customized steep trigger mode, and the recording time is not less than 100 ms. During withstand voltage test of the GIL, the transient voltage process caused by internal insulation breakdown is recorded successfully and accurately. The transient voltage duration is about 400us, the first abrupt change of voltage is about 120ns, and the instantaneous frequency excited by the abrupt change is close to 35MHz. Through in-depth analysis of transient voltage waveform, it is helpful to research the process of fault occurrence, identify the type of fault, and locate the breakdown location quickly and accurately, which provides strong support for the maintenance of UHV GIL.