UV transformer grounding resistance rise hazard and preventive measures:
1. Reasons for UV transformer grounding wire and neutral wire breaking and grounding resistance increase:
(1) Because the grounding body is buried in a non-standard manner, the installation process is sloppy, the grounding body and the grounding wire connector are loose, and the earth is too dry, which may cause the grounding resistance to rise.
(2) Due to the insufficient understanding of the role and importance of the grounding wire during the design and installation of the UV transformer, the neutral line section selection is too small. When the three-phase load is unbalanced, the neutral current is too large and causes the blow. In addition, due to damage of external force or theft of the grounding wire, the grounding wire or the neutral wire may be broken.
2. Elevated phenomena and hazards
(1) The grounding resistance of the UV transformer grounding wire is increased, and the grounding wire is damaged and grounded. For example, phase B is grounded. At this time, a current flows through the transformer grounding wire, and the phase B voltage is applied to the ground and ground. On the resistor, when the grounding resistance is larger, the partial pressure on the grounding resistance is larger. At this time, if someone accidentally touches the transformer grounding wire or the neutral wire and the transformer casing, the human body will be connected in parallel with the grounding resistance. If the grounding resistance is large enough, the voltage applied to the human body will be high, causing people to get an electric shock. If the human body accidentally touches phase A or phase C, the voltage applied to the human body will be a line voltage of 380V, which will pose a greater threat to the human body. In addition, some users connect the neutral line of the transformer to the outer casing of the electrical equipment for protection grounding, and the equipment is not insulated from the ground. When phase B is grounded, the earth is at the same potential as B, and the phase voltage is applied between the earth and the neutral line. At this time, if the electric equipment is used, for example, the phase A or phase C power source is used, the voltage of the outer casing to the ground will rise to 220V. The relative ground voltage of the device will be 380V. At this time, if a person touches the outer casing of the electrical equipment, it will also cause electric shock. In addition, when phase B is grounded, there will be a current flowing from the earth into the casing back to the neutral line, which will not operate for some of the more demanding consumers.
(2) The grounding wire is broken, and the grounding wire near the transformer is broken. It is like the grounding resistance is raised to a large value. At this time, the earth potential is the grounding phase potential. All the phenomena are the same as when the grounding resistance is increased, but the damage is even greater. , no longer repeat here.
(3) When the neutral line of the three-phase four-wire power supply transformer is disconnected, at this time, due to the imbalance of the three-phase load, the load grounding point will be offset, and the grounding point potential is not zero, so that some phase voltages rise. Burn down the electrical equipment. When the ground wire is broken or the grounding resistance is increased, the grounding wire of the transformer arrester is disconnected or the grounding resistance is increased. When the lightning strikes over voltage, the arrester cannot discharge to the ground normally, causing damage to the arrester or transformer.
Shenzhen Haike Transformer Co., Ltd. is a professional manufacturer integrating scientific research, design, manufacture and sales of dry-type transformers, reactors, voltage regulators and special transformers. It has complete production and processing equipment and perfect testing and testing methods.