1、 1. According to the market research, most of the current cable join protection products are only applicable for 35kV and in the medium and low voltage power system. The protectors for high voltage power system like 110kV and above are usually made from the following materials, which are not strictly required: 1) flame-retardant plastic (fireproof plate), 2) nylon fiber, 3) glass fiber reinforced plastic (AB pouring sealant), 4) quartz plate. Because the high capacity of high voltage and ultra-voltage system, huge amounts of energy will be released when breakdown fault happens. Currently, there is no better protector for high voltage cable joint in the market. The currently available cable joint protector for 110kV- 220kV is basically made from glass fiber reinforced plastic, epoxy and AB pouring sealant. The current fireproof protectors available are not explosive-proof and its price is cheap. Certain manufacturers pass it for explosion-proof protector and a large amount of users get cheated.
2、 2. Since 2006, the State Council and related departments have introduced laws and regulations regarding safe production in succession and make the claims of safety in production. In 2007, Byelaw Governing Reporting, Investigation and Handling of Production Safety Accidents (AnOrder by the PRC State Council No.493) re-divides the level of production safety accidents and rights of investigation and handling; in September 2011, Bylaw Emergency Handling and Investigation of Electric Power Safety Accidents (An Order by the PRC State Council No.555) further defines the electric power safety accidents, level of standard, rights of investigation and handling as well as enhances the legal responsibility of the accident; in November 2013, Guidance on the Prevention of Personal Injury Accidents of Electric Power (National Energy Safety 2013 No.427) was introduced by National Energy Administration.
3、 ① According to the 25 Key Requirements to Prevent Electric Power Production Major Accidents (Version in 2000) by State Grid, in order to prevent the fire accidents, Fire Control Rules for Electric Power Device (DL5027-93), DLGJ-1 54-2000 Cable Fire Prevention Measure and other regulations shall be implemented one by one.
4、 ② 25 Key Requirements to Prevent Electric Power Production Major Accidents
5、 3. Since the 25 Key Requirements to Prevent Electric Power Production Major Accidents was published by the former State Power Corporation, it has played an important role to prevent the major accidents caused by electric power production and guarantee the safe operation of power plants and power grids as well as reliable power supply. The number of various accidents declines. But as the quick development of national power industry and further deepening of power industrial system reform, units of high parameters and high capacity and power gird of ultra-high voltage and high voltage across the regions are gradually formed. New energy and new technology are constantly developing and there are new scenes and problems occurring in the safe production of power. There are new risks and problems confronting the safe production of power. Urgent requirements are brought up to supervise the safe production of power and prevent various kinds of accidents. From 2006, State Council and related departments have introduced a series of laws and regulations regarding safe production and put forward new requirements for the enterprises to produce safely. In 2007, Byelaw Governing Reporting, Investigation and Handling of Production Safety Accidents (An Order by the PRC State Council No.493) re-divides the level of production safety accidents and rights of investigation and handling; in September 2011, Bylaw Emergency Handling and Investigation of Electric Power Safety Accidents (An Order by the PRC State Council No.555) further defines the electric power safety accidents, level of standard, rights of investigation and handling as well as enhances the legal responsibility of the accident; in November 2013, Guidance on the Prevention of Personal Injury Accidents of Electric Power (National Energy Safety 2013 No.427) was introduced by National Energy Administration to put forward more requirements for safe production of power. Therefore, to further adapt to the supervision and management needs for the current safe production of power, implement the principle of “Safety First, Prevention First and Comprehensive Control”, complete the prevention measure for power production accidents, and effectively prevent the power accidents, State Energy Administration developed the 25 Key Requirements to Prevent Electric Power Production Major Accidents based on the former National Power Corporation's regulations as well as the conclusion of the power production accidents in recent years. Another 18 key requirements are added, including “prevent large fall-off of machine-network coordination and wind power device”, “prevent excitation accidents of generator”, “prevent power cable damage”, “prevent accidents in power dispatch automatic system, power telecommunication network and information system”, “prevent accidents in hydro-generator units (pump storage group)”, “prevent accidents in compensator for series capacitors and shunt capacitors”, “prevent device damage in the DV conversion stations and single & double pole forced outage accidents”, and “prevent personal injury accidents”.
6、 Its appendix also lists the key points that should be in line with the national laws, regulations and standards.
2. Fire Prevention
2.1 Strengthen the management of fire-fighting units and facility
2.2 Prevent cable fire
2.2.1 The choice and construction of the cables for new or extended projects shall be designed according to the regulations. The design is strictly carried out to prevent the cable fire and build the main body.
2.2.5 Non-buried cable joint shall be coated with flame-retardant materials. Oil-filled cable joint and high-intensity medium voltage cable joint shall be sealed with fire-and-explosion-proof box.
2.2.6 Try to reduce the number of cable joints. If necessary, cable joint shall be made according to the strict requirements and pass the quality control, then to be sealed with fire/explosion-proof box. The in-service joints in the transformer substation shall be gradually removed. During cable-cut and breakdown rescue, the joint shall be rearranged in the cable passage outside the station.
3. In recent years, as the development of national power gird construction and quick urbanization, the needs for high voltage cable at 110kV or above grows quickly. As the high voltage level of high voltage cables are mainly used in the key cities and key large corporations, once there is any problem happening to the quality, it may lead to major accident. The city power grid reformation project adopts more and more high voltage cables to dispatch the power these days, so the number of cable joints is growing accordingly.
4. In China, In large and middle cities like Beijing, Shanghai, Tianjin, Chongqing, Guangzhou, Shenzhen, Shenyang, Changchun, Chengdu, Zhengzhou, Shijiazhuang, Dalian, Nanjing, Wuhan, Changsha, Jinan, Qingdao, Xiamen, Zhuhai, the transmission and distribution system and power gird are huge, complicated and multiple with long distance of supply and high usage of cables. Meanwhile, due to the growth of large projects of 110kV, 220kV and 500kV, the cable routes for different environments are increased and the number of cable joints is also increased.
5. Because of the number limitation of current cable tunnels, now the cable joints are often installed together with other operating cable routes, which is the mixed use of cables defined by the State Grid. Under the influence of people, construction and operation environment, breakdown or explosion is unavoidable. The energy released in the cable joint fault may do harm to the cable routes, construction and people around it or even lead to the second accidents.
6. In October 2013, C phase cable joint of 220kV Huanqin Line A in Zhuhai had the short-circuit explosion. The fire caused the burn damage to the A and B phase; in January 2016, 220kV Huanqin Line A and B in Zhuhai also had short-circuit explosion, which needed 30 million RMB to change 266 sets of 220kV cable joints and led to power outage for more than 30 days. The economic loss is incalculable.
7. In the evening of June 5, 2013, explosion happened to a 500kV cross-river cable from Shanghai Power Company.