Substation grounding is one of the critical measures to ensure the safe and stable operation of the power system. Below is a detailed explanation of substation grounding:
I. Grounding Type and Purpose
Workground earthing:
Objective: Ensure the normal operation of the power system.
Example: Transformer neutral grounding in a direct grounding neutral system stabilizes the ground potential of the power grid and reduces the ground insulation requirements.
Lightning Protection and Grounding:
Objective: To protect electrical equipment from lightning damage.
Example: Lightning rods (now referred to as air terminals) and lightning arresters' grounding facilitate the smooth conduction of lightning currents into the earth.
Ground Protection:
Objective: Ensure personal safety.
Example: Electrical equipment enclosures (including cable sheaths) are grounded to prevent the enclosures from becoming electrified, which could pose a risk to personal safety.
One-Point Grounding (also known as Electronic System Grounding):
Objective: Stabilize potential, prevent interference.
Grounding for power plant thermal control systems, data acquisition systems, computer monitoring systems, etc.
II. Grounding Equipment and Installation Requirements
Grounding Device
Natural grounding bodies: structural steel of buildings, steel rails of steel conveyors, buried metal pipelines (excluding pipelines for flammable liquids and explosive gases), and metal sheaths of cables radiating underground with a quantity of not fewer than two.
Grounding Rods: Available in two basic structures, vertical burial and horizontal burial. Common vertical grounding rods are steel pipes with a diameter of 50mm and a length of 2.5 meters, or angle steel with a size of 50×5.
Installation Requirements:
Maximize the use of natural grounding bodies to save on investment.
When the natural grounding body does not meet the requirements, an artificial grounding device should be installed as a supplement.
The arrangement of the artificial grounding device should ensure a uniform potential distribution near the grounding device to minimize contact and step voltages.
The grounding grid should be arranged to ensure uniform distribution of ground potential, in order to minimize contact voltage and step voltage.
III. Ground Resistance and Measurement
Ground Resistance:
Ground resistance is a critical indicator of the performance of grounding equipment.
The size of the ground resistance is affected by factors such as soil resistivity, the material, shape, size, burial depth of the grounding electrode, and the structure of the grounding grid.
Measurement Method:
Typically, specialized grounding resistance measuring instruments, such as a grounding resistance tester, are used.
Choose appropriate measurement points and operate according to the correct measurement method to ensure the accuracy of the measurement results.
Section 4: Maintenance and Management of the Grounding System
Regular inspections:
Regularly inspect the connection points of the grounding device for any signs of looseness, corrosion, or breakage.
Ensure that bolts in threaded connections are tightened, and if loose, secure them promptly.
Ensure the welding joints are intact and free of cracks or other issues.
Clear away debris
Clear away debris and weeds around the grounding device, ensuring good contact between the grounding electrode and the soil.
Measure Ground Resistance:
Regularly measure the grounding resistance to ensure it consistently meets requirements.
If a significant increase in grounding resistance is detected, it is necessary to promptly identify the cause and take appropriate measures.
Corrosion Detection:
Regularly conduct corrosion inspections to assess the degree of corrosion on the grounding electrodes and cables.
If severe corrosion is found, timely anti-corrosion treatment or replacement of grounding equipment should be conducted.
In summary, substation grounding is one of the crucial measures to ensure the safe and stable operation of the power system. By properly selecting and installing grounding equipment, regularly measuring the grounding resistance, and strengthening the maintenance and management of the grounding system, the performance of the grounding system can be effectively improved, thereby ensuring the safe and stable operation of the power system.