Earthing 310 Mixed ground: The mix ground consists of the feature of the one-point ground andmultiple-point ground. For example, the power in the system needs to use the one-pointground mode while the radio frequency signal requires the multiple-point ground. So, youcan use the following figure to earth. For the direct current (DC), the capacitance is opencircuit and the circuit is one-point ground. For the radio frequency signal, the capacitanceis conducive and the circuit adopts multiple-point ground.When connecting devices of huge size (the device physical dimension and connection cable isbig comparing with the wave path of existed interference), then there are possibility ofinterference when the current goes through the chassis and cable. In this situation, theinterference circuit path usually lies in the system ground circuit.When considering the earthing, you need to think about two aspects: One is the systemcompatibility, and the other is the external interference coupling into the earth circuit, whichresults in system error. For the external interference is not regular, it is not easy to resolve.Appendix 7.3 Thunder Proof Ground Method in the MonitorSystem The monitor system shall have sound thunder proof earthing to guarantee personnel safetyand device safety. The monitor system working ground resistance shall be less than 1Ω. The thunder proof ground shall adopt the special ground cable from the monitor controlroom to the ground object. The ground cable adopts copper insulation cable or wire and itsground section shall be more than 20mm2. The ground cable of the monitor system can not short circuit or mixed connected with thestrong alternative current cable. For all the ground cables from the control room to the monitor system or ground cable ofother monitor devices, please use the copper resistance soft cable and its section shall be
