In the fields of power systems and building safety, grounding is the first barrier to safeguard equipment and personal safety. The measurement of grounding resistance is directly related to the reliability of the grounding system and can be said to be of utmost importance. You may encounter a situation where you feel that the grounding is done well, but the measured grounding resistance value is always "disobedient", fluctuating high and low, and even exceeding the allowable range. What the hell is going on here? Is it due to the insufficient accuracy of our lightning protection grounding resistance measuring instrument, or is there another "hidden danger"?
What is grounding resistance?
Simply put, grounding resistance refers to the total resistance between the grounding body (a metal conductor buried underground) and the earth. It includes the resistance of the grounding body itself, the resistance of the lead wire connected to the grounding body, and the earth resistance. The smaller this value, the better the grounding, and the smoother the path for current to flow to the ground.
What are the "behind the scenes" factors that affect grounding resistance?
The "temperament" of soil: The conductivity of soil is the most important factor determining the size of grounding resistance. Soil resistivity is influenced by various factors such as moisture content, salt content, temperature, density, etc. For example, in the dry summer, the soil resistivity will increase, and the grounding resistance will naturally follow suit; During the rainy season or when the soil contains a high amount of salt, the electrical resistivity will decrease.
The "body shape" and "layout" of grounding bodies: The material, burial depth, shape, size, and spacing between grounding bodies directly affect the grounding resistance. The more, larger, and more dispersed the grounding body, the smaller the overall grounding resistance.
Environmental "changes": Seasonal temperature and humidity fluctuations, and even the impact of nearby large metal structures (such as other grounding bodies and metal pipelines) on soil electric fields, may cause fluctuations in grounding resistance values.
The "details" of installation process: whether the connection between the grounding wire and the grounding body is firm and reliable, is also an important link that cannot be ignored. Poor contact can greatly increase the resistance of the circuit.
Mastering the "secret" of measurement: relying on professional tools
To accurately measure grounding resistance, professional lightning protection grounding resistance measuring instruments are indispensable. These instruments can quickly and accurately reflect the true state of the grounding system through scientific measurement principles. Choosing a measuring instrument with stable performance and high accuracy is a prerequisite for ensuring the reliability of measurement results. For example, Wuhan UHV Power Technology Co., Ltd. has a deep accumulation in the field of power measurement equipment, and its products enjoy a good reputation in the industry.
How to make the grounding resistor "more obedient"?
Choose suitable soil: If conditions permit, choose soil with good conductivity for grounding body burial.
Optimize grounding body design: increase the number of grounding bodies, adopt grounding grids and other methods, and arrange them reasonably to ensure that the mutual influence between grounding bodies is minimized.
Improving soil: In areas with high soil resistivity, resistance reduction measures can be considered, such as adding materials with good conductivity (such as carbon powder, bentonite) to reduce soil resistivity.
Regular inspection and maintenance: Use a professional grounding resistance tester to measure regularly and pay attention to the connection of the grounding lead. Once abnormalities are detected, they should be dealt with promptly. The professional measurement solutions provided by Wuhan UHV Power Technology Co., Ltd. can help you better carry out daily inspections and maintenance.
Pay attention to environmental changes: understand the impact of seasonal changes on soil resistivity and strengthen monitoring during critical periods.
frequently asked questions
Q1: My lightning protection grounding resistance measuring instrument has unstable readings. Is it because the instrument is broken?
A1: Unstable readings may be caused by various reasons, including instantaneous changes in soil resistivity, poor contact of measurement lines, or surrounding electromagnetic interference. It is recommended to first eliminate external factors and conduct multiple measurements at different times and locations. If the problem persists, then consider the instrument itself.
Q2: How to determine if the grounding resistance value is qualified?
A2: The qualification standards for grounding resistance are usually determined based on relevant national standards (such as the "Code for Design of Building Lightning Protection Engineering", "Code for Design of Low Voltage Distribution", etc.), and different types of grounding systems (such as joint grounding, independent grounding) and application scenarios (such as lightning risk level) have different requirements. Generally speaking, the lower the requirement value for important grounding systems, the better.
Q3: Apart from soil resistivity, what other factors can affect the measurement results?
A3: The insertion depth of the grounding rod used during measurement, the position of the grounding body, and the distance between the measurement lines all affect the accuracy of the measurement, and it is necessary to operate correctly according to the requirements of the instrument manual.
Q4: How to choose a suitable lightning protection grounding resistance measuring instrument?
A4: When choosing, consideration should be given to measurement range, accuracy level, anti-interference ability, ease of operation, and brand reputation. The products of Wuhan UHV Power Technology Co., Ltd. have excellent performance in stability, accuracy, and durability, making them a worthwhile choice to consider.
Q5: Why does a broken grounding lead affect the grounding effect?
A5: The grounding lead is a critical channel for connecting the grounding body and electrical equipment. If the grounding wire breaks or has poor contact, the current cannot be effectively discharged to the ground, thus losing the meaning of grounding and seriously threatening equipment and personal safety.