The grounding resistance of rural distribution transformers is often ignored, but it does relate to the safe operation of the transformer. Under normal circumstances, the smaller the grounding resistance, the better. Therefore, the grounding resistance of transformers requiring 100 kVA and above should not exceed 4 ohms. The transformer below 100 kVA should not exceed 10 ohms, but the grounding pole is buried for a long time. In the ground, it is easily damaged by soil erosion, which increases the grounding resistance. Therefore, the grounding resistance of the transformer should be measured periodically. In rural areas, the grounding resistance of the transformer is mostly measured by an insulation resistance meter. The measurement method is described as follows: Briefly describe the measurement method of grounding resistance of distribution transformer (1) Preparation before measurement 1. Should be selected in dry weather. 2. Before taking the necessary safety measures before measurement, disconnect the connection point between the transformer and the grounding pole. 3. Insert two grounding pins of not less than 500 mm in length into the ground so that they are not less than 400 mm deep. Try to make the grounding pole and the two grounding pins on the same line, and the distance between them is 20 meters. Connect the three terminals E, P, and C on the insulation resistance meter to the grounding pole of the transformer and the two grounding pins with special wires. The point P is required to be between the other grounding pin and the grounding pole of the transformer. (two) measurement 1. Place the insulation resistance meter horizontally and adjust the knob to adjust the zero knob so that the hands are at the zero position. 2. According to the grounding resistance required by the transformer and the actual situation on the site, put the override switch on the appropriate gear, start shaking the insulation resistance meter slowly, and rotate the dial of the potentiometer so that the pointer is at the zero position. Then speed up and shake at 120 rpm, and adjust the potentiometer knob to stabilize the pointer at zero. At this time, multiply the reading on the dial by the magnification to determine the grounding resistance of the transformer ground. 3. When the measured value is greater than the requirement, the cause should be found and resolved as soon as possible to meet the requirements. 4. When the measured value is less than 1 ohm, in order to eliminate the influence of wiring resistance and contact resistance, the connecting pieces of the two end buttons on the insulation resistance meter should be opened, and the wires are respectively connected to the grounding pole for measurement. Mattress Staple,Durable Furniture Staple,Houseware Sofa Staple,Rust Proof Hog Rings Nails Zhejiang Best Nail Industrial Co., Ltd. , https://www.beststaple.com