Operation management and fire prevention of the ho

2022-08-03
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Cable line operation management and fire prevention

after the cable line is put into operation in the power system, the operation management department will take charge of the operation and maintenance, keep the cable and its auxiliary equipment in good condition all the time, ensure the safe and reliable power supply of the cable line, and improve the availability of the cable line

1. The basic task of operation management

the operation management of cable lines is multifaceted, and its most basic task is to ensure the safe power supply of cable lines and reduce accidents. The basic tasks can be summarized into the following two aspects

1.1 make the cable adapt to the needs of electricity and user power supply

the cable operation management department must closely monitor the operation status of the cable equipment to make the cable line always adapt to the needs of electricity and user power supply. The operation management personnel should keep the cable lines within their jurisdiction under control. The insulation, conductor and sheath of the cable must meet the operation requirements

(1) the insulation must be qualified. The insulation of the cable and its accessories must match the electrical insulation level, and its u0/u must be consistent with the neutral grounding mode of the system. Moreover, the insulation must have a certain margin to withstand the internal and external overvoltage that may occur in the system

(2) the conductor section shall be sufficient. It shall meet the requirements of long-term load current and short-circuit capacity. Long term overload operation of power cables is not allowed. Cable overload operation has three disadvantages: first, it accelerates insulation aging and shortens cable life; Second, serious overload may lead to thermal breakdown of cable insulation; Third, the overload operation increases the line loss of the cable, that is, it increases the power supply cost

(3) the cable sheath shall meet the operation needs. The cable sheath, including inner sheath, armor layer and outer sheath (outer sheath), shall adapt to the operating environment. First, qualified inner sheath shall be provided. Oil paper insulated cables and high-voltage XLPE cables shall have metal sheath. According to the pressure or tension of the cable during operation, there shall be corresponding armor layer structure. According to the media around the cable, there shall be corresponding outer sheath

1.2 create a good operating environment for cables

the causes of cable line failure can be divided into two parts. The first part is the internal factors of cables and accessories, such as insulation aging, sheath flooding, poor design, construction, manufacturing and material defects. The second part is about the running environment of cable lines. Two reasons, each accounting for about half. The cable operation management department should create a good operating environment for the cable line. Liangtieshan, chairman of Yiping coal mining group, also told Caixin that he was powerless to dispose of assets, so as to avoid accidents as much as possible and make the cable give full play to its power transmission function. The work in this area mainly includes the following items

(1) protect cable lines according to law to prevent damage by external mechanical forces. In accordance with the power law and the regulations on the protection of power facilities issued by the State Council, the operation management unit shall formulate relevant regulations in conjunction with local government departments to establish a management system for the protection of underground power cables. At the same time, sufficient cable protection personnel shall be allocated and a special department for cable protection shall be established

(2) protect the cable sheath from chemical corrosion or electrolytic corrosion. When the cable is directly buried, when the metal sheath is subject to chemical corrosion or electrolytic corrosion of stray current, the sheath will be perforated and moisture will invade. The insulation of the oil paper cable will be damaged immediately after water intrusion, and the cross-linked polyethylene cable will cause water branches after being immersed in water. The measure to prevent chemical corrosion is to control the pH of the soil, which requires the soil to be neutral, that is, the pH value is between 6 and 8

(3) the key factors affecting the diversification of raw material structure to prevent cables from being damaged are thermal mechanical force of oil price, vibration and ground subsidence. Due to the change of load and ambient temperature, the cable is subject to certain thermo mechanical force due to thermal expansion and cold contraction (generally referred to as thermal expansion). This kind of thermo mechanical force can sometimes cause damage to cables or accessories. When the cable crosses the bridge, it will inevitably be affected by the vibration. The uneven settlement of the ground will also pose a threat to the cable safety

2. Causes of cable line fire

from the situation of cable line fire, the causes of cable fire are analyzed as follows: first, it is caused by its own fault, and second, it is caused by external reasons, that is, the fire source or kindling comes from the outside

(1) there is a problem with the cable itself. First, the cable is improperly selected in terms of material and model, resulting in short service life, reduced insulation performance, phase to phase short circuit and fire accident. Second, the cable line section is not selected correctly, and the upgraded vicrylrapid reg; When the load current is continuously passed, the heating temperature will exceed the allowable working temperature, which will accelerate the aging of the insulation and cause fire in serious cases. Third, the cable insulation is damaged. Due to mechanical damage, poor contact, aging insulation or reaching the service life, or short circuit fault, fire will be caused

(2) combustion caused by external fire source or heating. The first is the fire caused by combustible materials caused by open fire operations such as electric welding construction. If the cover plate or pipeline is not sealed or sealed tightly, the pipe trench will be mixed with wood chips, oil products and other combustible materials. At this time, electric welding (cutting) will be carried out, and the welding slag and sparks will fall into the pipe trench, which will cause a fire and burn the cable. Second, the combustible dust accumulated on the cable is ignited by high temperature. If the combustible dust is scattered on the cable rack and cable, it will cause spontaneous combustion due to the high temperature on the cable surface or the baking of the hot air pipe due to the untimely cleaning. Third, the oil filled electrical equipment failed and the fuel injection caught fire. Due to the vibration of the transformer protection device, the transformer longitudinal data is greater than or equal to the transverse data. The transformer explodes and catches fire, burning the cable line. Fourth, the cable line caught fire in case of high temperature. In the turbine oil system of the power plant, if the oil leakage meets the high-temperature pipeline, it will cause a fire, which will ignite the cable line and burn the cable. Fifth, the cable laying direction and position are incorrect. If it is erected close to combustibles, oil and gas pipelines and buildings, it is easy to burn the cable lines in case of fire

3. Measures to prevent cable line fire

to curb cable line fire accidents, it is also necessary to prevent according to the three conditions of combustion. Preventive measures shall be taken from the following aspects:

(1) keep away from the control fire source and heat source. During the erection and layout of cable lines, they shall be as far away from steam and oil and gas pipelines as possible, and the distance between the lines and them shall be controlled. Reliable safety protection measures shall be taken if the distance is close or within 1m of the intersection. Cable lines shall not be laid in the pipe trench of combustible gas and liquid; If it is laid in the thermal pipe trench, thermal insulation measures shall be taken; Overhead cable lines shall not be arranged in places with fire and explosion hazards

(2) isolate inflammables and explosives. When laying cables, cable lines in cable sections susceptible to external fire shall be provided with fire-retardant trough, painted with flame-retardant materials, and set isolation measures with non combustible materials to prevent the spread of fire. For the cable trench near the oil filled electrical equipment, sealing measures shall be taken, and the outside shall be packaged. It is better to use buried laying or pipe laying

(3) close the holes of cable route. The cable route layout is very complex. The holes passing through the cable interlayer in the control room and the holes passing through the pipe trench and shaft must be sealed and filled with non combustible materials. The cable holes passing through the control cabinet box and the lower part of the instrument panel shall be tightly sealed with special refractory materials. It is strictly prohibited to use wood and other combustible materials for temporary plugging to prevent the fire from spreading everywhere through the cable line and causing serious consequences

(4) set fire separation according to the layout of cable lines. Firewalls and fire barriers shall be set in certain sections of the cable line to control the fire within a certain range and prevent it from spreading. Fire separation shall be set at the following parts of cable tunnel, pipe trench and bracket: the junction of different workshops and plants, the indoor access, the intersection of different voltage distribution devices, the cable way connection of different units and main transformers, and the connection between the tunnel and the main control room, centralized control room and control room. Firewalls with doors shall be set for separation. Firewall separation shall also be set every 100m for cableways with long distance. The cable shaft can be separated by fire-proof interlayer, and the fire-proof isolation section can be set at the middle joint of the cable to achieve the purpose of fire prevention

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