Problems dealing with ground resistance in automatic control systems
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Is it better to share the grounding system of the instrument system with the electrical grounding system, or to have a separate grounding system for the instrument system? There is a question involved. The connection resistance requires a ground resistance of 1 ohm. The instrument system is grounded separately, and the ground resistance is 4 ohms. A 1 ohm grounding resistance is easy to implement in actual construction. Which method is better?
It seems that the instrument requirement is 1 ohm and the electrical requirement is 4 ohm. It doesn't matter on site, the construction is the same. What we have done is unified grounding.
If we reduce the grounding resistance from 4 ohms to 1 ohm, how much difference can there be in the actual construction quantity? If we strictly follow the testing requirements, how much difference can there be between the cost to achieve 4 ohms and the cost to achieve 1 ohm? ? Because some people always report that it is too difficult to achieve 1 ohm.
It is better to have a separate grounding system for the instrument system! Meter requirement is 1 ohm.
It is better to ground the instrument system separately. Our company is doing a lightning protection grounding design for the DCS system power supply and the DCS system instrument grounding is connected together. I feel bad, and we are coordinating the reconstruction.
first question: Of course, it is better to ground the automatic control system separately. The reason is that it is okay to construct electrical grounding and automatic grounding at the same time. However, if it is an expansion or addition, the grounding resistance will be different, which is very detrimental to the automatic control system during lightning in summer. second question: The requirements for grounding construction are almost the same. The metal investment, labor input and earthwork volume of the project are almost the same. There is not much difference. The employer is making excuses or making excuses for the asking price. The only difference is: There may be differences in the selection of steel.
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Now the grounding of our DCS system is completely floated at the control cabinet end, and is connected to a node left for us by the electrical ground through a 90-square-meter cable. The entire electrical ground has a large circle of ground electrodes, and the ground resistance is a few tenths of ohms. It is said that separate grounding is required, but sometimes the on-site construction conditions do not allow it. For example, if there are no high-voltage electrical equipment within a few meters of the surrounding area, we cannot achieve this. Our approach seems to be theoretically feasible.