Direct current (DC) power has two electrodes, a positive and a negative one, with the positive electrode having a higher potential and the negative one a lower potential. When these electrodes are connected to a circuit, they maintain a constant potential difference between the circuit's ends, thereby creating a current from the positive to the negative electrode. Simply relying on the difference in water levels cannot sustain a steady flow of water; however, by continuously pumping water from a lower to a higher level, a consistent water level difference can be maintained, resulting in a steady flow.
Direct current (DC) systems are applied in hydropower and thermal power plants, as well as various substation types. These systems primarily consist of battery banks, charging equipment, DC distribution panels, DC switchgear, DC power monitoring devices, and DC branch feeders, thereby forming a vast, widespread DC power supply network. This network ensures a safe and reliable power source for relay protection devices, circuit breakers, signaling systems, DC chargers, UPS systems, and communication systems, among other subsystems.
The working principles are divided into two types: one uses municipal electricity to convert AC to DC; the other utilizes DC power. Avionics ground power: 2 x 36V, Avionics power: 1, 400Hz variable frequency power: 7, 115/200V power: 2, 27V DC power: 5, 400Hz power: 12, Avionics power supply.
As AC power passes through the input switch to connect to the transformer, the city power voltage is converted to the designed voltage. It then enters the pre-regulation circuit, which is designed to initially stabilize the required output voltage. The purpose is to reduce the voltage drop across the high-power adjusting tube between input and output, decrease the power consumption of the high-power adjusting tube, and improve the efficiency of the DC power supply. The pre-regulation power supply is typically stabilized using a thyristor phase-shifting regulator and relay-switched transformer taps. After passing through the pre-regulation power supply and filter ①, the voltage is relatively stable with minimal ripple, becoming a low-voltage DC power. This is then accurately and quickly topped up by the high-power adjusting tube under the control circuit, resulting in a DC voltage with stable precision and performance that meets standards. It is then filtered through filter ② to obtain the required output DC power. To achieve the desired output voltage or current value, we need to sample and detect the output voltage and current values and transmit them to the control/protection circuit. The control/protection circuit compares and analyzes the detected output voltage and current values with the set values from the voltage/current setting circuit, then drives the pre-regulation circuit and high-power adjusting tube to ensure the DC power supply outputs the set voltage and current values. Additionally, if the control/protection circuit detects abnormal voltage or current values, it will activate the protection circuit, putting the DC power supply into a protective state.
Direct current (DC) power is supplied to various charging modules through a two-way alternating current (AC) input line that passes through a switching device, outputting a single AC line (or just a single AC input line). The charging modules convert the incoming three-phase AC power to DC power for battery charging, while simultaneously powering the closing busbar load. Additionally, the closing busbar is supplied with power for the control busbar via a voltage reduction device (which may not be required in some design schemes).
Each monitoring unit in the DC power system is managed and controlled by the master monitor, with information collected by the units sent to the master monitor for unified management via RS485 communication lines. The master monitor can display various system information, and users can also query system information and perform "four remote" functions through touch or button operations on the master monitor's display screen. System information can also be connected to a remote monitoring system via the master monitor's upper computer communication interface. In addition to the basic measurement units, the system can be configured with functional units such as insulation monitoring, battery inspection, and switch quantity monitoring to monitor the DC system.
