Electrical Grounding and Instrument Grounding
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This post was last edited by laoyier on 2009-6-4 17:48 In some engineering projects, the instrument major requires a "separate" grounding network, which is not connected to the electrical grounding network, and the grounding resistance is less than 1 ohm. However, there are also some projects that do not have such strict requirements and generally use a shared grounding grid. If the instrument requires a separate grounding grid, are there any specific requirements for the distance between it and the electrical grounding grid? Are there any relevant specifications or calculation formulas?
The grounding system is the lifeline of the three electrical systems. From an engineering perspective, major systems should be separated as much as possible. This is not only the philosophy of our Sanden people, but also a technical need! When it comes to philosophy, it is to simplify complex problems. However, with the needs of high integration and intelligence, even the world's top electrical companies like Siemens are unable to face this problem, let alone us? Speaking of technical requirements, the transmission system like Siemens connects the common terminals of all power supplies directly to the ground, which is unacceptable to ordinary instrument and control systems!
Since they are all protective grounding, just repeat the grounding. Make a separate grounding grid, which is also connected to the electrical grounding grid (because they are all on the earth).
It is true that the instrument grounding of some projects requires separate grounding. For example, the grounding of most control systems requires separate grounding and is less than 1 ohm. Only when the soil conditions are difficult to meet the low resistance requirements, comprehensive grounding measures should be considered.
Electrical grounding is generally made into a ground electrode, which generally protects people, while instrument grounding is generally used to reduce signal interference. Therefore, the two purposes are different and are generally not connected.
This is exactly what was said above, and it goes right down to the basics.
Again, let’s do equipotential. Something from this place or that place. Find a place to look at the plane: lol The key is to have the equipotential standards in place.
The main reason for the separation is that the electrical requirement for electrostatic grounding is less than 4 ohms, the neutral point of the transformer is 1 ohm, and the meter's is also 1 ohm. However, if the neutral point is displaced, there may be a voltage to the ground. If the meter's ground is connected to it, it will carry voltage, and this voltage will affect the normal use of the meter. However, if the whole factory's grounding grid is good and the grounding resistance is less than 0.5 ohms, then it doesn't matter.
My friend on the 5th floor said it right. Electrical grounding mainly protects people, while instrument grounding also plays a role in reducing signal interference. Of course, it also protects people. The two purposes are not exactly the same. Generally speaking, it is better not to connect them.
The 7th floor is not talking about the same situation.
DCS manufacturers require that no electrical high-voltage equipment be grounded within 110 square meters. This condition cannot be met at all, or is difficult to achieve.； We now float all the instrument grounds for a little grounding, and share a grounding grid with the electrical ground. As long as the grounding resistance of the grounding grid is small enough, there is no problem in use.
Well said, there is an essential difference between instrumentation and electrical
The ground of the instrument must be separate. If it is a public ground, that ground may not be zero potential. I have even encountered this situation. The potential of the ground is not zero. Even if the meter is connected, it cannot be measured accurately!
I think they should be separated so that they are not easily confused. Avoid voltage incoming
Electrical grounding and instrument grounding must be done separately in large projects. Otherwise, many inexplicable problems will occur in the instrument system in the future. in this regard * * It seems that there are no very specific regulations ； Our factory requires that the electrical grounding be less than 4 ohms and the instrument grounding be less than 2 ohms.
It is an inevitable trend that electrical and instrumentation will be compatible with each other in the future. Electricity cannot be automated without instrumentation. When the instrument is separated from the electrical system, it is an empty frame. I think the ground resistance is small and meets the requirements of the instrument, so it can be used.
There is so much to talk about here that I can’t finish it in one day! The key is to minimize the resistance between the two, so as to minimize the influence on each other!
Analog ground and digital ground must be connected separately
The grounding of electrical appliances and instruments should be separated. Grounding of instruments is mainly to prevent signal interference or even failure to work properly without grounding. I have encountered an E+H acid meter device that normally displays the pH value but a fixed value without a ground wire. Electrical equipment does not have this problem.