The main grounding network of power plants and substations plays a decisive role in ensuring the safe operation of power equipment and personal safety. The grounding resistance value is an important technical indicator of the grounding grid. Due to the significant difference between the design value and the actual value of the grounding resistance, in order to have a true and accurate grasp of the grounding resistance of the grounding grid, it is necessary to measure the grounding resistance of the grounding grid. This is of great significance for accurately estimating the safety of substations and ensuring the safe operation of the power system.
When measuring grounding resistance, the following points should be noted:
1. Generally, the grounding device being measured should be disconnected from the lightning protection wire.
2. The current pole and voltage pole should be arranged in a direction perpendicular to the line or underground metal pipeline.
3. It should be avoided to measure the grounding resistance immediately after rain. When measuring grounding resistance, it is best to do so in spring with low rainfall or winter with lower temperatures, when the soil moisture content is the lowest, the temperature is the lowest, and the electrical resistivity is the highest.
4. When using AC ammeter and voltmeter methods, the electrode arrangement should be arranged in a triangular shape, and a high internal resistance voltmeter should be used for the voltmeter.
5. The distance between the tested grounding body E, voltage pole P, and current pole c should meet the requirements of the measurement method.
6. The cross-sectional area of the connecting wire used: the current wire is greater than 2.5mm, the voltage wire is not less than 1.5mm, and the current circuit should be suitable for the measured current value The resistance of the wire connected to the tested grounding body E should not exceed 2% to 3% of R. The test lead should be insulated from the grounding body.
7. The voltage pole lead and current pole lead of the instrument should be kept at a distance of at least 1m to avoid interference with themselves.
8. The measurement should be repeated 3-4 times and the average value should be taken.
9. When using a hand cranked grounding resistance meter for measurement, interference is found, and the rotation speed of the grounding resistance meter can be changed.
10. When the sensitivity of the instrument is too high during measurement, the position of the electrode can be raised to insert it shallower into the soil. When the sensitivity of the instrument is insufficient, water can be injected into the insertion points of the voltage and current poles to moisten them and reduce the resistance of the auxiliary grounding rod.
11. The measured current should be greater than 20A as much as possible to ensure measurement accuracy.
12. When measuring grounding resistance on live equipment, special attention should be paid to: when disconnecting and restoring the grounding lead, insulated gloves must be worn.
13. It is strictly prohibited to touch the grounding wire that is disconnected from the ground.
14. It is strictly prohibited to measure the grounding resistance of the grounding grid during thunderstorm weather or when a grounding fault is found in the substation booster station.
ZC-410B-5A-XP high current grounding characteristic tester is a specialized instrument for measuring the grounding resistance of the grounding grid and the grounding conductivity between the grounding point. The instrument adopts frequency conversion anti-interference technology, which does not require high current measurement. It can accurately measure 50Hz data in a strong interference environment of the substation. The measurement results are displayed on a large LCD screen and come with a micro printer that can be printed out. The instrument can simultaneously measure the grounding impedance and grounding resistance, which can more accurately reflect the actual characteristics of the grounding grid.
Kvtester Electronics Technology Co.,Ltd. is a high-tech enterprise specializing in power testing, testing, research and development, production, and sales of testing equipment. It has been engaged in the electrical testing industry for many years, and its products are of high quality. We welcome customers to come and purchase. Service hotline: 0086-27-81778799, to learn more, visit the official website: www.kvtester.com
