In the substation, relay protection, automatic devices, signaling devices, accident lighting and long-distance operation of electrical equipment generally use DC power, so the output quality and reliability of DC power are directly related to the safe operation and smooth power supply of the substation.
Purpose and necessity of DC system reconstruction
The DC system of the substation is called the heart of the substation, and it shows how important it is in the substation. The power system of Zhongyuan Oilfield was built in the late 1970s. Due to the limitations of the technical conditions at that time, some of the DC system equipment of the substations successively built were silicon rectifier capacitors to compensate DC power supplies, and some were KGCA with lead-acid batteries —50 / 98 ～ 360, KGCFA—75 / 200 ～ 360 silicon rectifier DC power supply, and some are BZGN-20 / 220 type cadmium nickel battery DC screen. Some of the substation DC equipment that has been put into operation earlier and runs for a long time are seriously aging, which poses a serious threat to the safe and reliable operation of the substation. For example, a certain 110kV substation has been tripped due to a DC system failure, resulting in a vicious accident of power loss at the entire station. Although no major accidents occurred at other stations, the DC system often has problems, and there are many defects. Some defects cannot be handled, which causes the DC system to be in a state of illness for a long time, resulting in failure to supply power to users.
With the rapid development of the power industry, in order to improve the power supply quality of the power grid, make the power grid safe and economical, and realize the automation of the power system, the requirements for the key equipment of the power control system, the control power supply, are also increasing. However, the original DC equipment adopts traditional phase-controlled power supply, which has low efficiency and large ripple coefficient, and is unsatisfactory in terms of electromagnetic radiation, heat radiation, and noise. In addition, the monitoring system is imperfect, and the 1 + 1 backup method is adopted. It is difficult to meet the technical requirements for the increasingly advanced instruments, controls, and automation equipment of the secondary circuit. In addition, because the phase-controlled power supply's floating charging voltage is easy to fluctuate, battery pulsation charging and discharging will occur, which will greatly damage the maintenance-free battery and affect battery life. Coupled with other equipment transformation and investment in new equipment, the original phase-controlled power supply can no longer meet the needs of Zhongyuan Oilfield's power system, and it is urgently necessary to carry out transformation and replacement to ensure the safe operation and stable power supply of electrical equipment. The intelligent high-frequency switching power supply has been widely used in many fields due to its small size, light weight, superior technical indicators, modular design, N + 1 hot backup method, and convenience for four remotes. Since the 1990s, high-frequency switching power supplies have been used in newly built or transformed power plants and substations in advanced foreign industrial countries, and all of their storage batteries have also been maintenance-free. In order to achieve the goal of Zhongyuan Oilfield's power grid equipment to reach the advanced level in the same industry, according to the actual situation of the power grid, the current advanced intelligent high-frequency switching power supply system is adopted for the transformation of DC system equipment.
Performance characteristics of intelligent high frequency switching power supply system
In order to ensure the quality of the intelligent high-frequency switching power supply system, we organized a number of technicians to inspect multiple manufacturers to understand the manufacturer's production process, scale, and experimental testing methods. After three comparisons, the technical transformation decision was made. Use GZDW-200 / 220 type operating power. It is a new type of four remote high frequency switching power supply specially developed for power system. It adopts high frequency soft switching technology and modular design. The output voltage is 220V and is equipped with standard RS? 232 interface, easy to interface with automation systems, suitable for various substations, power plants and hydropower stations. This device has the following performance characteristics:
1) Modular design, N + 1 hot standby, smooth expansion.
2) Perfect monitoring function, high intelligence, large-screen LCD Chinese character display, sound and light alarm.
3) Is the monitoring system equipped with standard RS? 232 interface, easy to access the automation system, implement four remote and unattended.
4) Automatic management and maintenance of the battery, real-time monitoring of the terminal voltage, charging and discharging current of the battery pack, automatic control of average, floating and regular maintenance.
5) With battery temperature compensation function.
6) The module can be plugged and unplugged under power, which is safe and convenient to replace.
7) The step-down method adopts a new type of high-frequency soft-switch stepless two-way voltage regulation, abandoning the traditional silicon stack step-down method, with high output voltage accuracy and fast dynamic response.
8) Adopt the latest soft switching power supply technology and adopt imported devices.