Talking about the safety protection of underground power supply and electrical equipment in non-coal mines Li Dapeng non-coal mine production safety is inseparable from the underground, if the electrical equipment is damaged or the power supply is faulty, it will affect the safe production of the mine, in serious cases it will lead to equipment damage and personnel hurt. Therefore, we must strengthen the safety protection of underground power supply and electrical equipment, and should take reliable power supply technical measures and means based on on-site working conditions and the national mine power supply technical specifications, and formulate corresponding management regulations and systems to ensure that mine personnel and electrical equipment Safety. Non-coal mines refer to all metal and non-metal mines except coal mines (including stone coal), including: gold mines, lead cast mines, uranium mines, and copper mines. Non-coal mines are divided into open pit mines and underground mines. The production system of underground mines is relatively complex, including the processes of exploration, mining, cutting, and recovery. The entire production process involves rock drilling, blasting, ventilation, transportation, power supply, water supply and drainage, dust removal, and tailings disposal. Many production processes require the use of electrical equipment. Affected by the dynamic changes in the production process and the complex production environment, narrow mining and transportation lanes, humid air, and poor working conditions, electrical equipment, cables, and wires are vulnerable to scratching, squeezing, and corrosion, causing damage to the outer insulation layer. , Leakage, short circuit failure, resulting in equipment damage, personnel hazards of electric shock. In order to prevent accidents and ensure the safety of people and equipment, downhole power supply must adopt reliable protective devices and necessary safety measures. 1 Safety protection for downhole power supply 1.1 Safety protection for downhole substations Underground power substations can be divided into downhole central substations and downhole local substations according to the power supply area. 1.1.1 The downhole central substation is the core of downhole power supply. It is the hub connecting the surface substation and the underground substation. The substation is mainly equipped with a DC power supply and control system and a high voltage power supply system. Among them, the DC power supply and control system protect the high-voltage switch phase from external AC power. When the high-voltage switchgear is in operation or in a fault, the power supply can be quickly cut and closed, and an audible alarm is issued. The high-voltage power supply system is a function for transmitting power, power failure, and safety protection to output high-voltage cables, high-voltage transformers, or high-voltage motors. The protection of equipment mainly includes over-current protection, quick-break protection and under-voltage protection. The safety protection for operators is mainly the “five prevention†function that comes with equipment manufacturers. 1.1.2 Downhole local substations are located in the central location of the local underground electricity load, which has reduced the voltage drop of the power supply. The choice of location should be as much as possible to reserve a certain amount of room for expansion, to facilitate the use of electrical equipment capacity, and as much as possible to the cement surface of the wall reinforcement, and do the treatment of the waterproof project. The main function is to transfer the high-voltage power from the surface substation or downhole central substation to the isolation switch and transformer, and to step down the high voltage (10KV-6KV) to the low voltage (380V) for downhole use. Electrical equipment input power. 1.2 Safety Protection of Underground High-voltage Cables In accordance with the requirements of the relevant national departments, the new underground mine cables use flame-retardant cables in a unified manner. The old mines gradually eliminate ordinary cables and replace them with fire-retardant cables. In the event of a cable failure, the cable skin is affected by high temperatures and ignites other cables after the fire, thus expanding the scope of the accident. 1.3 Safeguards for Downhole Transformers The selection of downhole transformers must be in the form of explosion-proof, and it is a device that can still work normally without being affected by the harsh environment downhole. Usually we choose the KS11 series of mine transformers. Because the underground power supply adopts the three-phase three-wire neutral point ungrounded power supply mode, the equipment must be protected grounded or grounded, so that when the device has a leakage fault, the current flowing through the human body is also relatively small compared to other power supplies. By way of example, this type of power supply is relatively safe compared to downhole power supply. But it is also a troublesome thing, that is when the need for 220V power downhole for lighting or other equipment work must be step-down isolation transformer, the three-phase 380V AC power down to three-phase 220V AC power, and then take any two The single-phase 220V power supply is quite suitable for the device. 2. Safety protection against failure of electrical equipment in parallel 2.1 Avoiding electrical fire accidents Phase-to-phase short circuit between the power supply line and the electrical equipment. Overloading of the electrical equipment for a long time may cause the temperature rise of the current-carrying conductor to be too high, resulting in a fire. Electric sparks and arcs can ignite insulating materials, wooden supports, etc. and cause fires. The poor connection between the conductors, the increased contact resistance, and the local temperature increase caused by current flow are often the main causes of fire. The quality of the cable junction box and cable head is not high due to the sealing process, leaving an air gap. When the moisture invades, the explosion of the heated gas causes an explosion and causes a fire. The insulating oil of electrical equipment is used in a humid environment. The moisture in the oil absorbs moisture and the insulation performance decreases. Short-circuits between phases may occur, resulting in oil burning. Under the action of an arc, the insulating oil can decompose the mixed gas containing hydrogen and can be heated at high temperatures. Causes an explosion. The main measures for preventing electric fires are: 1 Correctly select and install electrical equipment and power supply lines, and strengthen maintenance and inspection during operation to prevent short circuit faults and overload conditions from occurring. 2 Install relay protection devices. 3 Make reasonable adjustments to various types of short-circuit protection devices to ensure that they are sensitive and reliable. 4 Take appropriate fire prevention measures at locations where electric fires may occur. 2.2 Avoid electric shock accidents Electric shock refers to the electric current passing through the body when it touches the live body or near the high voltage electrified body. Electric shock includes contact with normal live parts, electric shock, contact with electric leakage parts and no direct contact with electric equipment. In order to prevent the occurrence of electric shock accidents, the safe use of electricity must be strictly implemented during the design, manufacture, use and maintenance of electrical equipment. There are six main measures to prevent electric shock: First, make the human body unable to come into contact with or close to the charged body, such as fence gate isolation, set the locking mechanism, etc.; Second, underground electric equipment must be set to protective grounding; Third, in the underground high and low voltage power supply system In the installation of leakage protection devices; Fourth, the laying of underground cables in line with the provisions, and strengthen management; Fifth, the operation of high-voltage electrical equipment, must comply with safety procedures, the use of security tools; Sixth, hand-held electrical equipment should have good insulation . 2.3 to avoid the occurrence of power grid leakage fault The relative humidity in the underground roadway up to more than 65%, in this condition the operation of electrical equipment, although its insulation has taken some special measures, but leakage faults still occur. In particular, some low-voltage cables in mining areas are also damaged by rocks or ore that are often detached, and the outer insulation layer will be damaged, causing leakage accidents. There are six main measures for preventing leakage: First, the correct selection of electrical equipment models for underground power grids; Second, the use of neutral point insulation of the power supply system; The third is to take protective grounding measures; Fourth, the installation of a leakage protection device acting on the switch trip; Fifth, selective leak detection and protection devices are installed on high-voltage feeders. Sixth, leakage protection devices with leakage lockout or selective leak detection and protection devices are installed on downhole low-voltage feeders. If these two devices are not installed, they must be installed. Set up a leak detection device that automatically cuts off leakage feeders. Seventhly, selective leak detection and protection devices must be used together. They must not use the total leakage protection device with delay. The eighth is to prevent cables and electrical equipment from being immersed in water to prevent crowding. , stab and make the cable damaged; Nine is the wire connection must be tamped, no burr; ten is not to add additional components. 2.4 Avoiding Grid Current Failure All current flowing through an electrical device exceeds the rating of the device and are called overcurrent. There are many causes of over-current, such as short circuit, overload, and single-phase operation of the motor. Whether a short-circuit or an overload occurs, electrical equipment or cables will heat up and exceed the allowable limit, causing insulation damage. The main measures to prevent current failure are: 1 Use an overcurrent protection device. 2 Use the maximum three-phase short-circuit current of the distribution network to verify the breaking capacity and thermal stability of the switchgear and the thermal stability of the cable. 3 Use the minimum two-phase short-circuit current to verify the protective device's reliable operating coefficient. 4 Regularly check and adjust the overcurrent protection device used according to regulations. 5 When the load changes, adjust the setting value of the overcurrent protection device in time to ensure its reliability. 6 Strengthen routine maintenance and inspections. 3. Related systems and preventive measures First, establish and improve the equipment inspection system for underground substations, regularly inspect inspection equipment, find hidden equipment in a timely manner, and carefully fill in the equipment operation records, and find that equipment abnormalities should be handled promptly and decisively. The damage is reduced to the minimum level to ensure the normal operation of other equipment. The second is to develop inspection specifications for downhole transformers and downhole cables, and regularly look at the oil level and sound of the transformers, the degree of insulation of the cable sheaths, the connection of downhole grounding electrodes, and timely detection of failures and timely handling. The third is that the leakage protection switch should be dispatched by someone to debug and test periodically to ensure the reliability and sensitivity of its operation. To prevent equipment leakage due to not timely debugging can not cut off the power supply, endanger the safety of personnel and equipment. Fourthly, a downhole grounding resistance test report system was established to regularly detect the resistance of the downhole grounding resistance to ensure that it was within the qualified range to ensure the sensitivity of other equipment tripping. The fifth is to strengthen the operational training of operators and maintenance workers, improve their equipment maintenance skills, shorten the processing time of equipment failures, and ensure the efficient and safe operation of equipment. (Li Dapeng Shougang Tonggang Group Banshi Mining Company Shangqing Mine) Touch Kitchen Faucets,Touch Kitchen Faucets Price,Touch Kitchen Faucets Product Yuyao Zelin Sanitary Ware Co., Ltd , https://www.kitchen-sinkfaucet.com
Talking about Underground Power Supply and Safety Protection of Electrical Equipment in Non-coal Mines