The underground environment of coal mines is complex and dangerous, and the safety and reliability of the power supply system are crucial. To prevent electrical accidents, ensure the safety of workers and the normal operation of equipment, the underground power supply system of coal mines must have complete protective measures.
1、 Overcurrent protection
Overcurrent protection is one of the basic protective measures in the power system, used to prevent the current flowing through the circuit from exceeding the design value, thereby avoiding equipment damage and fire accidents. The overcurrent protection in coal mines is mainly reflected in the following aspects:
Protecting equipment and circuits: When the current exceeds the preset safety value, the overcurrent protection device will quickly cut off the power supply to prevent electrical equipment and cables from overheating or burning. Overcurrent protection includes short-circuit protection and overload protection. Short circuit protection immediately acts upon the occurrence of a short circuit, cutting off the power supply; Overload protection operates when the current continuously exceeds the rated value but does not reach the short-circuit current.
Automatic reclosing function: In order to improve power supply reliability, overcurrent protection devices usually have automatic reclosing function. After detecting the disappearance of overcurrent in a short period of time, the power supply can be automatically restored, reducing the power outage time caused by faults. This function is particularly suitable for underground coal mines to avoid prolonged power outages caused by minor malfunctions, which can affect production and safety.
Coordination protection: In the underground power supply system of coal mines, multiple overcurrent protection devices need to be coordinated to make the protection devices near the fault point act first and avoid large-scale power outages. By reasonably setting the action time and current threshold of the protection device, the protection system can quickly and accurately locate and isolate faults.
2、 Leakage protection
Leakage protection is an essential safety measure in the underground power supply system of coal mines. The leakage protection device can detect leakage phenomena in the circuit and quickly cut off the power supply when dangerous currents flow through the human body or equipment casing, preventing electric shock and fire accidents.
Human safety protection: Due to high humidity and complex environment in coal mines, electric leakage is highly likely to occur, endangering the safety of workers. The leakage protection device can quickly cut off power before the leakage current reaches the human danger threshold, ensuring the safety of workers. The standard leakage protection device is generally set to a leakage current of less than 30mA, and the power supply is cut off before the human body feels the dangerous current.
Equipment protection: Aging or damage to the insulation of underground electrical equipment may cause leakage, leading to fire or equipment failure. The leakage protection device can detect small leakage currents and promptly cut off power to prevent accidents from occurring. Leakage protection devices not only protect individual devices, but can also be installed at different nodes of the entire power supply system to provide leakage protection.
Regular testing and maintenance: The leakage protection device needs to be regularly tested and maintained to ensure its sensitivity and reliability. Mine electricians should regularly test the working status of leakage protection devices and replace aging or damaged equipment in a timely manner. Through maintenance and testing, potential leakage hazards can be identified and resolved, improving the overall safety of underground power supply systems.
3、 Grounding protection
Grounding protection is the basic guarantee for the safe operation of electrical equipment, especially in coal mines where it plays an important role in preventing electrical accidents. Grounding protection is achieved by grounding the equipment casing and power system, allowing leakage current to quickly flow into the ground, avoiding electric shock to the human body and equipment damage.
Prevent electric shock accidents: Grounding protection can prevent the equipment casing from being electrified, avoiding electric shock accidents when workers touch the equipment. Even if there is an internal malfunction in the equipment, the leakage current will quickly flow into the ground through the grounding wire, protecting the safety of workers. The underground environment of coal mines is humid, and the insulation performance of electrical equipment is prone to decline, making grounding protection particularly important.
Reduce fault voltage: By grounding the system, limit the fault voltage within a safe range to prevent high voltage from causing harm to personnel and equipment. A good grounding system can effectively reduce contact voltage and step voltage, reducing the risk of accidents. In the underground power supply system, the grounding resistance should be maintained at a low value to enable the grounding current to be quickly and safely discharged.
Grounding system design: The grounding design of the underground power supply system needs to be based on the specific conditions of the mine. Usually includes multiple parts such as the main grounding grid, equipment grounding, and lightning protection grounding. The main grounding network should be arranged in the main power supply area of the mine to ensure reliable grounding of equipment. Equipment grounding should be connected to the main grounding grid using a grounding wire to prevent corrosion and aging of the grounding wire.
The safety of the underground power supply system in coal mines is directly related to the stability of mine production and the safety of workers. By implementing three major measures: overcurrent protection, leakage protection, and grounding protection, electrical accidents can be effectively prevented and the reliable operation of the power supply system can be guaranteed.
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