Grounding of power transformers

The working ground, transformer shell ground, and arrester ground are shared and are called "trinity" grounding.

Share it. Our company has a shared grounding grid.

It can be made integrally grounded if the ground resistance is less than 4 ohms. Lightning protection grounding resistor

Pay attention to the transformers on the side of the road. They are all integrally grounded.

That is, for public use, the grounding resistance can be directly reduced to less than 4 ohms.

Nowadays, joint grounding is done, that is, protective grounding, working grounding, lightning protection grounding, anti-static grounding, and instrument grounding are all combined to form a grounding network. The advantage is that the entire plant is also at equal potential.

Nowadays, most of them are integrated. The key grounding resistance must meet the requirements and the grounding reliability must be high! I don’t know if there are any cases where the transformer was struck by lightning due to unreliable grounding when receiving lightning!

The working grounding, protective grounding and discharge gap of our company's transformers are all together~~~~~~~~~~

For transformers with a total capacity of 100kVA and above, the grounding resistance of the grounding device should not be greater than 4Ω, and the grounding resistance of each repeated grounding device should not be greater than 10Ω.； For transformers with a total capacity of less than 100kVA, the grounding resistance of the grounding device should not be greater than 10Ω, and the repeated grounding should not be less than 3 places.

Such a professional and profound question. . Check it out.

Generally, a common grounding network is used, but the grounding resistance cannot exceed 4 ohms, and grounding resistance must be tested regularly.

I use a shared grounding network, but the grounding resistance cannot exceed 4 ohms.

Thank you all for your replies and suggestions.

give reference: Power system neutral point operation mode The selection of the neutral point operation mode mainly depends on the insulation requirements of electrical equipment and the reliability of power supply when single-phase grounding. 1. The neutral point is directly grounded: In this operating mode, the non-faulty phase-to-ground voltage remains unchanged, and the insulation level of electrical equipment can be considered based on phase voltage. This has great economic and technical value for the 110KV ultra-high voltage system. In order to reduce equipment insulation requirements, my country's 110KV ultra-high voltage system usually adopts the direct grounding operation mode of the neutral point. 2. The neutral point is not grounded: Since the equivalent capacitance of each phase to ground is the same, the capacitance currents of the three phases to ground are symmetrical, and the voltage of each phase to ground is the phase voltage. When a single-phase grounding occurs, the line-to-line voltage remains unchanged, the non-faulty phase-to-ground voltage increases to √3 times the original phase voltage, and the faulty phase capacitance current increases to 3 times the original voltage. When a single-phase grounding occurs in an ungrounded neutral point system, the normal operation of the three-phase electrical equipment is not affected because the line voltage does not change. (But it should be eliminated as soon as possible) In (6~35KV) medium voltage systems, in order to improve power supply reliability, the neutral point ungrounded system is preferred. When the grounding current does not meet the requirements, That is, when the single-phase grounding capacitance current exceeds the specified value (30A for 6~10KV lines and 10A for 35KV lines), the neutral point should be grounded through impedance. 3. In low-voltage systems below 1KV, considering the use of single-phase loads, the neutral point is usually directly grounded. The grounding point of the conductive part of the TN system electrical equipment and the power grounding point have direct electrical connection (shared grounding electrode). TN——S: Three-phase five-wire wire system, high requirements for electric shock protection, explosion-proof and fire-risk environments, and situations where there are a large number of information equipment in the building. TN——C: Three-phase four-wire system, the PEN line generates voltage drop, conducts fault voltage, over-current protection also serves as ground fault protection, and the three-phase load is balanced. There is no direct electrical connection between the grounding point of the conductive part of the electrical equipment of the TT system and the grounding point of the power supply (each uses a grounding electrode). It is suitable for power consumption places outside the effective range of equipotential bonding, urban public power, and substations where the high-voltage neutral point is grounded with low resistance. The grounding point of the conductive part of the electrical equipment of the IT system is directly grounded, and the power end is not grounded or grounded through high impedance. It is used in places with high power continuity requirements, such as emergency power supply, hospital operating rooms, etc.

Nowadays, public grounding is used for networking! ! ! ! ! ! ! !

It is best to use a shared grounding grid. The grounding resistance is less than 4 ohms. If there is a PLC or DCS, the grounding resistance is less than 1 ohm. This effect is the safest.