In the power system, grounding resistance is a crucial parameter that directly affects our electrical safety and the stable operation of equipment. Many people may feel unfamiliar with it, and even find it somewhat mysterious. But don’t worry, today we’re going to talk about what this’ grounding resistor ‘really is, why it’s so eye-catching, and how we can better measure and manage it.
What is the sanctity of grounding resistance?
Simply put, grounding resistance refers to the total resistance of current flowing from a grounding device (such as a grounding electrode) to the earth, and then passing through the earth to another grounding body (or spreading). You can imagine how high the “threshold” that electric current needs to pass through when returning to “home” (the earth) is. The lower the threshold, the easier it is for the current to ‘go home’, and the better the protection for equipment and personal safety.
What are the “behind the scenes” factors that affect grounding resistance?
Soil resistivity: This is the most significant influencing factor. The soil composition, humidity, and temperature vary greatly in different regions, directly leading to different electrical resistivity. Soil with high moisture and salt content has lower electrical resistivity, while soil with dry and sandy soil has higher electrical resistivity.
The size and shape of the grounding body itself: The larger and deeper the grounding body is buried, the larger the contact area with the soil, and the lower the resistance.
The contact between the grounding body and the soil: If the soil around the grounding body is not well compacted or there are gaps, it will increase the contact resistance, thereby increasing the total grounding resistance.
Stray currents in soil: When other currents pass nearby, they can also affect the grounding resistance of the grounding body.
The ‘weapon’ for measurement: grounding resistance meter
To understand how high your ‘threshold’ is, you naturally need tools at your disposal. The grounding resistance meter is our first choice. There are many types of grounding resistance meters on the market, which can accurately measure the resistance value of the grounding body through different measurement principles. For example, some use the three electrode method, while others use the double clamp method, both of which can help us quickly obtain data.
What “relatives” are associated with grounding resistance?
Personal safety: When equipment leaks electricity, a good grounding system can quickly guide the fault current into the ground, avoiding electric shock to the human body.
Equipment protection: Lightning strikes, static electricity, etc. can all cause damage to the equipment, and effective grounding can promptly dissipate these high-voltage charges.
Electromagnetic compatibility (EMC): Good grounding helps reduce electromagnetic interference and ensure the normal operation of electronic devices.
How can we do better? The path of improvement in grounding
Regular measurement: HV Hipot Electric Co., Ltd. suggests that grounding devices should be regularly measured for grounding resistance according to national regulations and equipment importance, in order to promptly identify potential issues.
Choose the appropriate grounding body: Based on the local soil conditions, select the appropriate grounding body material, size, and burial method.
Optimize soil: If conditions permit, soil resistivity can be reduced by improving the soil (such as adding conductive powder, graphite, etc.).
Multi point grounding: In some important places, using multi-point grounding can further reduce grounding resistance and improve safety.
Professional maintenance: For large power equipment and facilities, it is recommended to entrust a professional power technology service company, such as HV Hipot Electric Co., Ltd., to conduct regular grounding system testing and maintenance.
frequently asked questions
Q: How often should a grounding resistance meter be measured? A: It is generally recommended to measure at least once a year, and the measurement frequency can be appropriately increased when important equipment or environmental changes occur frequently.
Q: What is the qualified grounding resistance? A: National standards have clear regulations for different types of grounding systems, generally requiring no more than 4 ohms, and specific reference should be made to relevant technical specifications.
Q: Why does my grounding resistance measurement fluctuate greatly? A: This may be related to changes in soil moisture, the influence of nearby high-voltage lines, or poor grounding connections.
Q: Is there anything to pay attention to when using a grounding resistance meter? A: Before measurement, ensure that the instrument has sufficient power, correct wiring, and select the appropriate measurement mode.
Q: Which type of grounding resistance meter should I choose? A: According to your specific needs and budget, you can choose grounding resistance meters with different functions such as digital, pointer, and intelligent.