DC power has two electrodes, positive and negative. The potential of the positive electrode is high and the potential of the negative electrode is low. When the two electrodes are connected to the circuit, a constant potential difference can be maintained between the two ends of the circuit, so that in the external circuit A current flows from positive to negative. The difference between the water level alone cannot maintain a steady water flow, but with the help of the pump to continuously send water from a low place to a high place, a certain water level difference can be maintained to form a steady water flow.
The DC system is used in hydraulic and thermal power plants and various substations. The DC system is mainly composed of battery packs, charging devices, DC feeder panels, DC distribution cabinets, DC power monitoring devices, and DC branch feeders. A huge and distributed DC power supply network provides safe and reliable working power for relay protection devices, circuit breaker tripping and closing, signal systems, DC chargers, UPS, communications and other subsystems.
There are two working principles, one is to use mains power to convert AC into DC; the other uses DC.
AC to DC
When the mains voltage is converted into the designed voltage through the input switch and the transformer is turned on, it enters the pre-stabilizing circuit. The pre-stabilizing circuit is to perform preliminary voltage regulation on the desired output voltage, and its purpose is to reduce the high-power adjustment. The tube voltage drop between the input and output of the tube can reduce the power consumption of the high-power regulating tube and improve the working efficiency of the DC power supply. stabilize the voltage. After passing through the pre-regulated power supply and filter ①, the voltage obtained is basically stable and the DC current with relatively small ripple is passed through the high-power regulating tube controlled by the control circuit to accurately and quickly ask the top pressure, and the voltage regulation accuracy and performance will meet the standard. After the DC voltage is filtered by the filter ②, the output DC power that I need is obtained. In order to obtain the output voltage value or constant current value that I need, we also need to sample and detect the output voltage value and current value. And transmit it to the control/protection circuit, the control/protection circuit compares and analyzes the detected output voltage value and current value with the value set by the voltage/current setting circuit, and drives the pre-regulator circuit and the high-power adjustment tube. The DC stabilized power supply can output the voltage and current values we set, and at the same time, when the control/protection circuit detects abnormal voltage or current values, the protection circuit will be activated to make the DC power supply enter the protection state.
DC power supply
The two AC incoming lines output one AC (or only one AC incoming line) through the switching device to supply power to each charging module. The charging module converts the input three-phase AC power into DC power, charges the battery, and supplies power to the closing bus load at the same time. The closing busbar supplies power to the control busbar through a step-down device (some designs do not require a step-down device).
DC power supply
DC power supply
Each monitoring unit in the system is managed and controlled by the main monitoring unit, and the information collected by each monitoring unit is sent to the main monitoring unit for unified management through the RS485 communication line. The main monitor can display various information in the system, and the user can also query the system information and realize the "four remote" function on the main monitor display screen through touch or key operation. The system information can also be accessed through the host computer communication interface on the main monitor. Remote monitoring system. In addition to the comprehensive measurement basic unit, the system can also be equipped with functional units such as insulation monitoring, battery inspection, and switching value monitoring, which are used to comprehensively monitor the DC system.
Post time: Sep-06-2022