China has entered the development period of large power grids, large units, high voltage and high automation. With the rapid development of the economy, the demand for electricity is also growing rapidly, and UHV transmission has gradually entered the construction of China's electric power. UHV transmission energy meets the basic requirements of large-capacity, long-distance, high-efficiency, low-loss, low-cost transmission, and can effectively solve the current low-transmission capacity, low economic efficiency, poor safety and stability of the 500kV ultra-high voltage grid. The problem, therefore, the construction of UHV power grid has become an inevitable trend of China's power development. 1 Overview Power system stability refers to the ability of each synchronous generator in the power system to maintain and resume synchronous operation after being disturbed. Only when the generators are running synchronously, that is, under the stable operation state of the power system, the power generated by the generator is constant, the phase angle difference between the electromotive force phasors of each generator, the generator electromotive force and each busbar The phase angle difference of the voltage and the phase angle difference of each bus voltage phasor remain constant. Assuming that the generators in the power system are not operating synchronously, the active power output from the generator is not constant. The voltage of the busbars of the entire system and the power of the transmission lines are not fixed, and a large swing will occur. If the power of each generator and the amplitude of each bus voltage swing are not attenuated after the system is disturbed, the power amplitude is getting larger and larger, and the voltage amplitude is getting lower and lower, the power system control device cannot restore the generator to synchronize, not When the bus voltage is restored to a value close to the disturbance, the generators in the power system lose synchronization and the power system loses stability. 2 Stability of UHV transmission network The UHV grid is part of the entire grid, and the stability analysis method for the UHV-UHV grid is not fundamentally different from the HP-UHV grid. UHV transmission is to transport large-capacity power from power generation bases or power plants to the load center over long distances. The parameter characteristics of the UHV transmission line are determined by its transmission capacity and the associated parameters of the transmitting and receiving systems. Therefore, the transmission capacity of the high-voltage transmission line is limited by the voltage stability limit and the power angle stability limit. 3 Stability principle of UHV grid UHV transmission delivers more power than ultra-high voltage lines. If the UHV transmission line is suddenly interrupted, it will cause a large power shortage to the grid system, which will seriously affect the safe operation of the next-level 500kV grid. In order to ensure the safe and stable operation of the entire power system including the UHV grid, the double-back UHV transmission line is usually used to deliver the power of the delivery system or the power generation center to the remote load center. The power delivered by the UHV transmission line during actual operation is the same as that of the UHV transmission, and must meet the requirements of the power system's power angle stability. According to the performance characteristics of the aforementioned UHV transmission, these stability requirements are as follows: 1) When a serious fault occurs in a transmission line or a three-phase short-circuit fault occurs near the transmission line, the relay protection and the circuit breaker operate normally, the fault line is tripped, and the fault is cut out, and the power system should be able to maintain transient stability. 2) After the fault line trips and cuts out the fault, the remaining one line can keep the transmission power of the original double-circuit line within the static stability limit range, have a certain static stability margin, and restore the stable operation of the power system within a short time. To ensure that the operating personnel can re-adjust the power system flow after the fault, the power system can restore the static stability margin of normal operation. 3) After the fault line is cut off, the remaining one line keeps the transmission power of the original double-circuit line within the small interference voltage stability limit, and leaves a certain stability margin. 4) Under the large-scale operating conditions of the power system, a single order occurs in the UHV transmission receiving end system The large unit trips, according to the UHV transmission line for increased power transmission and the distribution of power after the fault, leaving a short static stability margin, short-term active and reactive transmission margin required for voltage stability, to ensure the receiving end The voltage is within the stability margin control range. 4 Economic comparison of transmission The comparison between EHV transmission and UHV economy is generally compared by comparing the transmission costs used to deliver the same power and the same distance at two voltage levels: one is to compare their initial investment costs according to reliability indicators. How much; the other is to compare the life cycle. Through analysis and reliability analysis, it can be seen that the transmission capacity of a 1100kV UHV transmission line can reach more than 4 times that of a 500kV conventional transmission line, while in the comparison of operation and maintenance costs of lines and substations, UHV transmission is required. The cost is much less than the ultra-high pressure. The power loss and power of the line is about 1/6 of the 500kV line. Clearly, UHV transmission has obvious advantages in terms of operating costs. 5 Conclusion Electricity is related to the basic industry of China's national economy and people's livelihood. In China's power development, the State Grid and a power transmission company undertake important tasks of safeguarding national energy security, optimizing energy resource allocation, and promoting national economic and social development. On the basis of carefully analyzing the development status and trends of China's power industry and power grid, we deeply realized that accelerating the construction of a strong national smart grid grid based on UHV power grids to achieve efficient allocation of resources and promote the efficient development and utilization of China's energy and It is of great significance to improve the overall efficiency of the power industry. Liquid Cooling Servo Motors,Cnc Router Servo Motor,Metal Milling Servo Motor,Ac Spindle Servo Motor Zhejiang Synmot Electrical Technology Co., Ltd , https://www.synmot-electrical.com