We have also seen that the transformer needs three phases of electricity. One is the fire line, which has electricity, and the other is the zero line, which has no electricity. One is the electric wire, which guarantees safety. Therefore, it is necessary to connect all three phases of electricity to ensure the normal and safe operation of the transformer. Transformer in the use of the ground is to be buried, buried depth is it, is actually has a regulation, not deep, not shallow, after we need to measure control in a certain range. How much ground line of transformer bury after all is more reasonable? Let's take a comprehensive look at this:
There are two kinds of connection modes of ground wire of general transformer. One is direct grounding of ground wire or low impedance grounding, which is called large ground current system. The other is ground - line ungrounded, through the arc - suppression coil or high impedance grounding, known as a small earth current system.
(1) for 6 to 10 kv system, considering equipment insulation level according to the line voltage for the equipment cost impact is not big, in order to improve power supply reliability, generally adopt neutral point grounding or via arc suppression coil grounding way.
(2) for systems with 110kV or above, the main consideration is to reduce the insulation level of the equipment and simplify the relay protection device. In general, the neutral direct grounding method is adopted. In order to improve the reliability of power supply, measures such as setting up lightning conductor and installing automatic reclosing device are adopted.
(3) 20-60 kv system, is an intermediate case, generally a phase ground capacitive current isn't very big, the network is not very complex, equipment insulation level of increase or decrease in cost impact is not significant, so generally adopt neutral point via arc suppression coil grounding method.
(4) the neutral point of the power grid below 1KV shall be operated ungrounded. However, the system with 380/220v voltage adopts three-phase five-wire system. The zero line is to obtain electromechanical pressure and the ground line is to be safe.
The ground wire of the transformer must be buried safely, otherwise it is easy to have problems。 Many transformers have problems because they are not firmly buried, and some even have accidents because of ground wire problems! So it's better to be careful!
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