EMI On The Digital Protective Devices & EMC Problem Caused By Lighting Strokes In Substations

AbstractIt's the first time in China that the digital protective devices will be installed near the high voltage equipments at a 500kV substation. This thesis describes the EMI on the signal cables when the substation encounters with the lightning strike.The first part of my thesis is to introduce a model of the grounding grid and use EMTP to calculate the distribution of the voltage along it when this substation encounters with the lightning strike, then establish a model of the multi-core cable with a single shielding to calculate the EMI caused by the unbalanced distribution of current and voltage on the grounding grid when this kind of cable is used between high voltage switch and the protective devices.The second part is of my thesis to build a practical grounding grid model in our lab and to exert the impulse currents to it by a Impulse Current Generator, and to measure the voltage on the node of the grounding grid and the EMI voltage of cables that lay on the grounding grid model.In the end, we got some real results and found the trend was coincident with our theoretic result. These results may give some suggestions to deal with the EMC problem in substation.