Dry type transformer grounding modes
Time：2024-11-21 Auther：ZTelec-www.ztelectransformer.com
Dry type transformer grounding modes
1. Neutral grounding method
The neutral grounding method is the most commonly used grounding method. In dry type transformers with voltage grades of 220kV and below, the neutral ground method is usually used.
The method of neutral grounding is to install the current transformer on the neutral point of dry type transformer to realize the functions of current detection and overcurrent protection. At the same time, the neutral point of the transformer is grounded by connecting the ground wire to the ground pole.
2. Shell grounding method
The shell of the dry type transformer also needs to be grounded, which mainly is for insulation protection of the transformer and to ensure personal safety.
The shell is grounded by connecting the ground cable to the transformer shell and then to the ground pole. This method is one of the protective measures for transformer grounding and is mainly to protect the surrounding environment of the transformer.
3. Control box grounding method
Grounding is also required in the control box of the dry type transformer. This method is mainly aimed at the insulation protection of the equipment in the control box and the safety of personnel.
The control box is grounded by connecting the ground cable to the control box and grounding it through the ground pole. If there are multiple devices inside the control box, each device needs to be grounded independently.
The role and importance of grounding:
Prevent potential difference: Through grounding, you can ensure that metal parts such as the iron core of the transformer and the box are always at the same potential, which can avoid the potential difference caused by strong magnetic field and prevent the occurrence of gap discharge.
Protection device: Grounding can protect the device from damage caused by lightning and overvoltage and ensure the safe operation of the device.
Personnel safety: Grounding can prevent the occurrence of leakage electric shock accidents and protect the personal safety of operators.
Announcements
1. The grounding resistance should be smaller than the specified value
The ground resistance of the dry type transformer should be less than the specified value. In general, for dry type transformers with voltage levels of 220kV and below, the ground resistance should be less than 10 ohms.
2. The cross-sectional area of the ground cable should be reasonable
The cross-sectional area of the grounding cable should be properly designed based on transformer capacity, grounding resistance, and conductor length. Generally, the cross-sectional area of the ground cable must be greater than or equal to 16mm².
3. The ground cable must be reliable
The grounding cable must be securely connected to ensure proper grounding. The contact resistance between the ground point and the grounding electrode should be less than the specified value to ensure the quality of the grounding.
4. Independence of the ground cable
The ground wires of each part of the transformer should be independent of each other. They should not be grounded in series to ensure the safe and stable operation of the transformer.
Causes and solutions of poor grounding
Improper device installation: If the device is improperly installed, for example, the grounding resistance is large, the grounding fault may occur. The solution is to redesign the installation scheme, strengthen the quality of the grounding line, and reduce the grounding resistance.
Material aging: Dry type transformer after a long time of use, the material may age, resulting in a decline in the quality of the grounding line. The solution is to replace the aging material in time and check whether the grounding resistance meets the specified value.
External factors: If the ambient humidity around the transformer is large or the transformer is exposed to high temperature, high pressure and other adverse environments for a long time, the grounding effect of the transformer may also be affected. The solution is to improve the level of environmental management, establish a standardized environmental management system, and regularly carry out systematic testing and maintenance.
