How to reduce the potential difference between the neutral wire and the ground wire?
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Recently, I encountered a problem at work. Several analytical instruments require that their 230V single-phase operating power supply maintain a potential difference between the neutral and ground lines of no more than 2V. Please help analyze how to address this issue!
Simply repeat ground the neutral wire at the installation location
What was said upstairs doesn’t seem to comply with the standards, right? If this is done, what should the power system look like?
There are mainly two operating modes for low-voltage power supply systems in our country: the TN system and the TT system. 1. TN system: The neutral point on the low-voltage side of the transformer is directly grounded. The neutral wire N (commonly known as the “zero wire”) is then led out from the grounding point. In the system, the metal enclosures and frames of all electrical equipment are connected to the neutral wire for protection. 2. TT system: The neutral point on the low-voltage side of the transformer is directly grounded, and a neutral wire N is led out from the grounding point. In the system, the metal enclosures and frames of all electrical equipment are connected to ground for protection. The appeal explains that in our three-phase four-wire low-voltage power supply system, the N wire is grounded by itself. Since the N wire on the secondary side of the transformer is already grounded, grounding it again during use will not change the operation mode of the power system. If a simple action in daily life or at work could change the way the power system operates, then the operation mode of electricity would keep changing constantly, leading to complete chaos. Furthermore, if the first floor uses a 220V single-phase power supply for the instruments, the neutral wire must be grounded, and it is preferable to have it grounded multiple times.
I can state clearly that your explanation at the moment is perhaps plausible but unreasonable. Because our system is TN-S, rather than TN-C-S (a system without repeated grounding), it is incorrect to say that \"repeated grounding of the neutral wire at the installation site is sufficient.\" Since the grounding system cannot be changed, direct repeated grounding is not feasible. Perhaps what we need to do is find a way to balance the three-phase load or reconnect it to a three-phase balanced system; striving to reduce the potential difference between the neutral wire and the ground wire is the most effective approach.
A voltage gap protection device can be installed between the neutral wire and the ground wire; it activates when the voltage exceeds 2V, thereby reducing the voltage. Secondly, in terms of power supply, avoid using single-phase electrical equipment and strive to maintain a balanced three-phase load. A 220V power supply must be used; a 380/220V transformer can be employed for power supply.
Ensuring three-phase balance is the most crucial; increasing the cross-sectional area of the neutral wire helps reduce voltage drop. If that still doesn’t work, use a local TN-C-S system.
TN-S. Three-phase load balance – these are all standard practices. But it’s not aimed at the original poster’s question. My personal suggestion is to use a dedicated circuit, with a power supply coming directly from the substation to power the instruments. Additionally, it is recommended to use a 3-core cable, which is actually necessary as well; for example, 3*4. By the way, is the instrument room far from the substation? If it is, increase the cross-section further. For such a simple issue, the transformer side has redundant grounding. I don’t believe that a voltage difference of 2V can stump the electrical experts! :lol