Introduction to some types of DC power supplies
In the industrial application process of DC power supply, with the continuous development of power supply voltage equipment, the types of DC power supply have become more diverse. When different types of DC power supply are used, the properties of non-electrostatic forces are also different. In terms of energy, The conversion and efficiency are also different.
The DC power supply has two positive and negative electrodes. The positive electrode has a high potential and the negative electrode has a low potential. When two electrodes are connected to a circuit, a constant potential difference can be maintained between the two ends of the circuit, thereby creating a current flow from the positive electrode to the negative electrode in the external circuit.
Chemical batteries (such as dry batteries, storage batteries, etc.). Non-electrostatic forces are chemical effects related to the dissolution and deposition of ions. When a chemical battery discharges, chemical energy is converted into electrical energy, and Joule heat is diffused in thermoelectric power sources such as metal thermocouples and semiconductor thermocouples. Non-electrostatic forces are diffusion effects related to temperature differences and electron concentration differences. When a thermoelectric source supplies power to an external circuit, the thermal energy is partially converted into electrical energy.
In the process of passing through a DC generator, the generation of non-electrostatic forces is affected by electromagnetic induction. When a DC generator supplies power, mechanical energy is converted into electrical energy and Joule heat.
In photovoltaic cells, the non-electrostatic force is the effect of the photovoltaic effect. When a photovoltaic cell is energized, light energy is converted into electrical energy and Joule heat.
Factors affecting DC system grounding
Because DC power supply is a polar power supply, it is the positive and negative poles of the power supply. And AC power is a non-polar power supply. In common power operating systems, the AC power supply has a real "ground", which is an important concept for power safety. In order to better protect the safety of the system and users, the surface layers of substations and power generation equipment will be grounded, and it is hoped that the impedance will be as small as possible.
But the grounding of DC power supply is completely different from that of AC power supply. The grounding of DC power supply only represents the concept of neutrality. If the insulation resistance value between the positive or negative pole of the DC power supply system and the ground drops to a certain set value or lower than a certain value, we say that the DC system has a positive ground fault or a negative ground fault.
So what are the factors that cause the DC power supply to be grounded? The main situations are as follows:
DC systems in power plants and substations connect many devices and complex circuits. During long-term operation, DC systems will inevitably be grounded due to environmental changes, climate changes, aging of cables and connectors, and problems with the equipment itself. Especially in the construction or expansion of power plants and substations, due to various problems in construction and installation, hidden dangers of power system failure will inevitably remain, and the DC system is a weak link. The longer the operation time, the greater the possibility of a system ground fault.
