With the development of the economy, China's power grid technology is also rapidly advancing, and 220kV substations have become the mainstream power supply station for urban power supply. However, in actual operation, overvoltage often occurs, posing serious safety hazards to the power supply system. In the actual operation of a 220kV substation, operating overvoltage and vibration overvoltage are the two highest frequency overvoltage phenomena. Due to the fact that overvoltage issues not only threaten the safety of power equipment, but also have a significant impact on the personal safety of power operators, research on overvoltage issues is of great significance.
Overvoltage prevention during operation of 220kV substation:
1. Improve substation management level
Establish a complete substation operation management system, standardize operating procedures, adopt current advanced computer technology and intelligent sensor technology, improve the automation and intelligence level of the substation, minimize manual operations, thereby reducing failure rates, improving operational safety, and improving the management efficiency of the substation.
2. Comprehensive improvement of 220 kV substation system equipment
In the process of power transmission, the preparation level of system equipment sometimes has a direct and significant impact on the prevention level of overvoltage phenomena in 220kV substations. The safe operation of the 220kV substation can be fully guaranteed, which is directly related to the purchase and construction of corresponding system equipment. This requires relevant technical personnel to comprehensively improve the preparation level of corresponding system equipment in order to better reduce the frequency of overvoltage safety faults in 220kV substations in daily work and life.
3. Follow the principles of emergency response for substation accidents
The most basic standard for emergency response to substation accidents is to strictly comply with the safety work regulations and on-site accident handling system formulated by the power industry, standardize the operational behavior at the accident site, and carry out specific accident handling in accordance with the specific regulations and emergency plans of each management department. Accident handling should follow the following steps: the first step is to correctly determine the cause of the accident and carry out emergency response; The second step is to isolate the faulty equipment and restore power to the faultless equipment; The third step is to take safety measures for the faulty equipment and wait for the team to handle it. The first two steps are the main contents of accident emergency response.
4. Increase the capacitance of the capacitor
On chip transformers are commonly used equipment in the operation of 220kV substations. Increasing the capacitance of a capacitor can be achieved through various methods, such as winding multiple resistance coils or inserting one coil into another. Meanwhile, as the capacitance increases, the potential difference of the coil will also undergo significant changes. Once overvoltage occurs in the operation of the substation, it may mean that the coils of the capacitors need to be reset. There is also a special situation where the capacitance of the capacitor increases, that is, there is a current interruption phenomenon during operation.
5. Reduce no-load current
The excitation current and core loss current constitute the no-load current of the transformer. In actual operation, the variation of no-load current can be increased or decreased by increasing or decreasing the iron core of the equipment. By reducing the current loss of the iron core and preventing its damage, the iron core can be effectively protected. In addition, using better quality cores is also very helpful.
6. Strengthen accident drills and summarize the experience and lessons learned after accidents occur
As the saying goes, this is perfection. Regularly conduct accident drills and training for employees to familiarize them with the accident handling process, master typical fault handling methods, familiarize themselves with various faults, and be able to handle accidents conveniently, quickly, and accurately. After each accident handling, a group meeting should be organized to discuss the experience and areas for improvement in the accident handling process, providing reference for future accident handling.
Suppression measures for overvoltage during no-load transformer operation:
1. Improving the iron core has a certain reducing effect on no-load current
Due to the fact that the loss current of the iron core and the magnetization current jointly constitute the no-load current, the loss current of the iron core will generate the loss current of the iron core, and the magnetization current will also generate magnetic flux. Therefore, the transformer iron core has an important impact on reducing the no-load current. By improving the quality of the iron core and re improving its structure, this problem can be solved. Due to the high magnetic permeability of cold-rolled grains, cold-rolled grains can be used instead of silicon steel sheets. During transformer maintenance, the iron core should be strictly maintained in accordance with relevant quality standards.
2. Entanglement
The 220kV transformer is an iron core type transformer. If its winding form is wound winding, the parasitic capacitance of the transformer will increase. Winding is the process of inserting another turn of the winding into an adjacent wire turn in a circuit, thereby increasing the longitudinal capacitance of the winding. The actual potential difference between adjacent turns also increases, so that when overvoltage occurs, the initial voltage can be evenly distributed between the turns of each wire.
3. Parallel resistor switch
At a certain moment when the current is cut off, the magnetic field energy in the inductor can be converted into electrical energy, thereby charging the capacitor. At this point, if the resistor and switch are connected in parallel, the magnetic field energy in the inductor can be released. Before the current closes, wait for the switch of the parallel resistor to close, then short-circuit the switch of the parallel resistor, and then disconnect the switch after the current closes. The potential in the inductor will generate current into the resistor, causing the magnetic field energy in the inductor to be consumed.
Conclusion
In recent years, with the rapid development of China's power grid technology, 220kV substations have become the hub of urban power supply. During the operation of a 220kV substation, resonance overvoltage or operating overvoltage is inevitable. Therefore, analyzing the generation principle, prevention and suppression measures of overvoltage during the operation of 220kV substations has important practical significance.
