Mechanism And Protection Method Studies Of Induced Over-Voltage On Cable By Lightning Stroke In Substations

The electromagnetic environment in substations consists of power-frequency and transient electromagnetic fields, and the electromagnetic interferences on the secondary system under these cases, such as short circuit, lightning stroke and switching operation. And the reliability of secondary system critically affects the performance and safety of substations. Therefore the interference potential difference between the core wire and the shielding sheath on the end of secondary cable generated by grounding potential difference and grounding potential rising is discussed in this thesis when lightning current is injected into the grounding grid by the arrester's downlead.There parts are included in this thesis. The first is to introduce coupling theory and coupling model about the secondary cable in substation. Then is to establish the model of the grounding grid and use ATP-EMTP to calculate the distribution of the voltage along it after lightning stroke. The third parts is to get impedance parameter of cable based on geometric parameter of cable, and establish the distributed parameter model of the secondary cable, and use ATP-EMTP to calculate interference potential difference between the core wire and the shielding sheath. Finally protection method is got.After the computation, the following conclusions are obtained: the potential near the injected node dropped fast after lightning current is injected to the grounding grid. The potential of the grounding grid and interference potential difference between the core wire and the shielding sheath on the end of secondary cable is increased when...