Electrical risk factors and type of accident i, electrocution i, split into electroshocks and electric injuries. 2 electron shock currents: perceptive currents (average 1. 1ma for males and 0. 7ma for females), free of currents (average 16ma for males and 10. 5ma for females) and room tremors (approximately 50ma for duration). Human resistance: about 1000 000 when dry and about 500 800 when wet. 3. Type of electroshock: depending on whether the body with which the electroshock is touched is in a normal state of electrical charge, it is divided into direct and indirect exposure to electroshock; it can be divided into single-phase electric shocks, two-phase electric shocks and cross-step electroshocks, depending on the manner in which the body touches the body with the electroshock. Single-phase electric shocks accounted for more than 70 of all electrocution incidents. 4. Electricity injuries are thermal, chemical, mechanical, etc. Effects of electric currents. Electricity injuries include electric burns, electric branding, skin metalization, mechanical damage, electrophoid eye disease, etc。
Electricity burns. It's the most common electrical injury. Most of the electrocution incidents contained electrical burns. Electricity burns can be divided into electric burning and electric arc burns. Electrical fires and explosions1 and electrical fire explosions are fires and explosions caused by sources of electrical combustion. Hazardous temperatures, electric sparks and arcs generated by electrical installations in operation are the main forms of electrical combustion sources. (1) dangerous temperature: short circuits, overloads, leaks, poor exposure, iron heart overheating, heat dissipation, mechanical malfunctions, voltage anomalies, electro-thermal and lighting devices, electromagnetic radiation energy. (2) electric sparks and arcs: the sparks are interpolated discharges of electrodes, and the arcs are a collection of large quantities of sparks. They are divided into work and arc, accident and arc. 2. The explosion of electrical installations and circuits included an oil-impregnated transformer fire, an electrically motivated fire and a cable fire explosion. Iii. Thunder hazard 1, type of lightning, form of hazard and accident consequences (1) type of lightning:
3. Direct lightning (each discharge of a direct lightning strike includes a lead discharge, primary discharge, three phases of residual light), lightning sensor (including lightning static and lightning magnetic sensors), and ball thunder. (2) the hazard form of lightning is characterized by the high range of the thunder, the steepness of the thunder, the high impact, the high impact of the shock; and the destructive effect of the electrical, thermal and mechanical properties. (3) accidental consequences of the lightning hazard: fire and explosion, electrocution, destruction of equipment and facilities, massive power outage. Thunder parameters: thunderstorm day, thunder flow magnificence, thunder flow voltage, thunder flow expulsion. Iv. Equivalent hazards, the form and consequences of electrostatic hazards cause explosions and fires, may cause secondary accidents, and hinder production. 2. Characteristics of electrostatics: (1) mode of generation of electrostatics (exposure-separation, break-up, sensor-up, charge transport), solid electrostatics, human electrostatics (up to 10,000 v)
4 above), powder static, liquid static, vapour and gas static. (2) dispersion of electrostatics: neutralization, leakage. (3) impact factors of static power: materials and impurities, industrial equipment and industrial parameters. V. Radio-frequency electromagnetic field hazards refer broadly to electromagnetic waves with a frequency above 100khz. Hazard 1: the human body suffers varying degrees of harm from the absorption of radiation energy. 2. Production of sensor discharge caused an accidental detonation of the detonator. Vi. Types of damage to electrical installations: break-off, short circuits, abnormal patches, leaks of electricity, faulty locks, damage to electrical equipment or electrical components, etc. Hazards: fires and explosions, abnormally charged electricity, abnormally outages, safety-related system failure. Insulation: insulation of insulation material applied in engineering is generally not less than 107 m. Insulation material is typically subject to electro-resistance measurements using a mega-eat (sloop) watch. Insulation must not under any circumstances be less than
5. 1000 work volts. The screen protection and spacing: 1) the shield protection shall be of sufficient size to maintain the necessary distance from the body with the electrical charge. 2) the height of the shield shall not be lower than l. 7 m and the lower edge shall not exceed 0. 1 m. The height of the fence shall not be less than l. 2 m, the outdoor space shall not be less than l. 5 m and the distance between columns shall not be greater than 0. 2 m; for low pressure devices, the distance between the barrier and the naked conductor shall not be less than 0. 8 m. The height of an outdoor transformer fence should not normally be less than 2. 5 m. Covers, fences, etc., should be marked with signs such as "stopping, high pressure danger!" 3) spacing with electrical equipment: a high of 1. 2 m at the bottom of the visible workshop low-voltage distribution tank at the surface and l. 4 m in dark. The height of the surface at the bottom of the clearly charged table is 1. 8 m. Installation height of commonly used switch appliances l. 3l. 5 m; switch handles and construction
6. The distance of 150 mm shall be maintained between the structures to facilitate their operation. It is desirable to use a flat switch from the surface height of 1. 4 m. Clear plugs are 1. 3l. 8 m above ground altitude and 0. 20. 3 m in cover. Indoor lamps should be at a height greater than 2. 5 m; when practical conditions are not met, they may be reduced to 2. 2 m; and when less than 2. 2 m, appropriate safety measures shall be taken. When the lamps are located above the desktop, they are not accessible to people, and the altitude can be reduced to 1,5 m. Outdoor lamps should be above 3 m; they can be reduced to 2. 5 m when installed on walls. The minimum distance between cranes and route guides shall not be less than 1. 5 m for lkv and less than 1 kv, and not less than 2 m for 10kv. 4) spacing: in low-pressure operations, the distance between the human body and the tools it carries and the electric body should not be less than 0. 1 m. High pressure work, 10 kv to stop the working person and the tools and belts he carries
7 the distance of the electron shall not be less than 0. 7 m; line operation, 1. 0m. Indirect exposure to electroshock protection measure 1, the it system (protecting the site) connects the parts of the metal where electrical equipment may exhibit hazardous voltage in case of failure to the ground and the earth. (b) limiting failure voltage to safety through low electrical resistance; in 380v non-terrestrial low pressure systems, protection of ground resistance re4 is generally required; and for various off-site distribution grids. Tt systems: the distribution grid is directly connected to the ground and electrical equipment is shelled to the ground. The failure voltage on the leaking equipment shall be substantially reduced, provided that the remaining flow of electricity shall be protected or the excess current protection shall be installed. The work site is not a secure voltage. Mainly for low-pressure users, i. E. For small users who are not equipped with electrical transformers to introduce low-voltage power sources from outside. 3, tn systems (protected from zero) electrical equipment neutral in the non-electrical metal component of normal conditions and distribution grid points
Direct connectivity. It is equivalent to a traditional zero-protection system. Its first security function is to cut power quickly. These are tns, tncs, tnc. The tns system has the best safety performance and applies to sites with high explosive risk, high fire risk and other safety requirements. The plant's low-voltage distribution sites and civilian buildings should have a tncs system; the tnc system could be used in cases where electrical exposure is low and electrical equipment is simple. The protection of zeros is used in the distribution grid of the 220380 v-trill four-line distribution network of the low-pressure neutral point where the user is equipped with electrical transformers. Application of security requirements: 1) in the same zero-to-zero system, partial or individual equipment is generally not allowed to be located only and not zero; 2) repeat repeat location. 3) a single-phase short circuit of the pe line can be quickly cut off. Tn systems, handheld electrical equipment, end-line or interpolation circuits for mobile electrical equipment
The protective component shall ensure that the duration of the failure does not exceed 0. 4 s and the end line of the distribution line or fixed electrical equipment shall ensure that the duration of the failure does not exceed 5 s. 4) qualified place of work. Ground-based resistance should generally not exceed 4 and not exceed 10 in areas with high soil resistance rates. 5) pe and pen lines shall not be fitted with unipolar switches and smelters; pe and pen lines shall be protected against mechanical damage and chemical corrosion; pe feeder lines shall not be linked, i. E. The equipment's exposed conductor component shall not be used as a protective conductor. 6) the protection of the cross-section area. Pe has a mechanical shield of not less than 2. 5 mm2, no machine of not less than 4 mm2; pen is not less than 10 mm2 for copper, not less than 16 mm2 for aluminium and not less than 4 mm2 for cable cores; sl 16 is sl, 16sl 35 is 16 and sl 35 is sl/2. 7) power generation, primary and auxiliary
10 bits. Iii. Measures to prevent both direct and indirect exposure to electroshock1 and double insulation (1) classification of protective electrocution protection for electrical equipment: category o, category o, category oi and category, category, category. (2) dual insulation and enhanced insulation measures: insulation at work, protective insulation, dual insulation, enhanced insulation. Equipment with dual insulation and enhanced insulation is of the type and has a “back-to-back” sign. Work insulation is not less than 2 m, protection insulation is not less than 5 m, strengthening insulation is not less than 7 m. 2. Safety voltage: a combination of security measures for direct and indirect exposure to electroshock protection. (1) the limit and rating values for special low voltage are: 5 classes, 42v, 36v, 24v, 12v and 6v; the equipment supplied by special low voltage is classified; and the rating values are selected for: specially hazardous environment handheld tool 42v, click on dangerous environment handheld light 36v or 24v, metal containers, particularly wet environment handheld light 12v, water
11, down 6v. 3. Surplus electrical flows are protected and referred to as leak protection, which has the effect of preventing personal electroshocks, preventing fires caused by site failure and monitoring adjacent ground failure. (1) the rationale. The detection element, the intermediate, the three basic components of the implementing agency and the composition of the auxiliary power source and test device. (2) main technical parameters: rated residual movement current, rated residual non-action current, break time. The remaining mobile current values are rated at 13 levels, 0. 03a and below are highly sensitive and are used primarily to prevent various types of physical contact; 0. 03a and above 1a are medium-sensitivity to prevent electrical contact and leaks; and 1a and above are low-sensitivity to prevent electrical leakage and to monitor side-by-side accidents. The rated residual non-activated current may not be less than 12 of the rated residual movement current. Break time, divided into generic and time extension types, which apply only to indirect contact electric shock defence of in>003a
The difference between the length of the delay is 02s. (3) protection requirements for remaining electrical flows as protective devices. In the tn system, tnc systems must be converted to tncs, tns or local tt systems before they can be installed. In the tncs system, the remaining electrical flow is protected only in parts of the n line separated from the pe line. (4) equipment and sites for the remaining flow of electricity for protective devices must be installed. 1) end-of-pipe protection of mobile electrical equipment belonging to category i; electrical equipment for production; electrical machinery for construction sites; electrical devices installed outdoors; electrical equipment for temporary electricity; electrical outlets or circuits for power sources other than walled air-conditioning power outlets, such as institutions, schools, hotels, restaurants, enterprise units and homes; electrical equipment for swimming pools, fountains, baths; electrical medical equipment for which there may be direct contact with the human body in hospitals; and other. 2) lines to protect rural areas from the centralized installation of electrical meters; agriculture fan
Power distribution tanks for production equipment. (5) operation and management of the remaining electrical flow as a protective device. Six years of service and one call allowed. Electrical fire protection technologies i. Hazardous substances and hazardous environments (i) classification of hazardous substances, cluster 1 and classification of hazardous substances for explosive hazardous substances are grouped into three categories: categories (mine methane), categories (explosive gases, vapours) and categories (explosive dust, fibres, flyers). Category 2, category c, category c explosive gases are further classified into categories a, b and c, which are the most dangerous, according to the maximum test safety gap and the lowest incendiary current ratio. Grouping of 3 classes, classes, classes of explosive substances: 6 groups according to the induction temperature. (ii) hazardous environment 1, explosive gas environment (1) explosive gas environmental hazard site subdivision: the frequency and duration of occurrence of explosive gas mixtures are divided into sectors 0, 1, 2. Release
14. Levels of source and ventilation have a direct impact on the zoning. Ventilation is mainly natural and artificial, and its effectiveness is classified as “good” (good ventilation is marked by the concentration of hazardous substances in the mixture being diluted below the lower limit of the explosion). The iec and national standards divide ventilation into three levels: high, medium and low. (2) distinction of hazardous areas in explosive gas sites: principles. (3) range 2 of the explosive gas environmental hazard area, the explosive dust environment is divided into 20, 21 and 22 areas depending on the frequency, duration and thickness of the mixture. 3. Fire risk environments are divided into 21 regions, 22 regions and 23. Type of blast-proof electrical equipment and blast-proof electrical circuit 1 and blast-proof electrical equipment (1): classes, classes, classes. (2) equipment protection level (epl): ma/mb/ga/gb/gc/da
15,/db/dc(3) blast-proof structure of explosive electrical equipment: blast-proof, amplified, inherently safe, sealed, spark-free, positive pressure, etc. (4) marking of explosive electrical equipment: the selection of electrical equipment in ex (5) explosive hazard environment: based on the environment, type of equipment, etc. 2. The selection of the location, placement, conductor material, connection, etc. Of the explosive electrical circuits shall be based on the environmental hazard level. Area 1 distribution lines should be based on a copper core guide or cable, multiple copper core softlines or multiple copper core cables should be selected for severe vibrations, and aluminium core electric cables should not be used under mines. Area 2 power lines should use aluminum core guidance line or cable with an area of 4mm2 and above, and lighting lines may use aluminium core guidance lines or cables with an area of 25mm2 and above. Sectors 1 and 2 must have medium- and indirect headlines in the connector box, area 1 would be suitable for blast-proofing and area 2 would be enhanced. Thunder and static protection technology i
Mine-protective measure 1, mine-protective building category i (powder manufacturing workshop, acetylene station, storage depot, petrol-refining workshop, electric spark vulnerability), category ii (open steel closed gas tanks with explosive risk, electric spark vulnerability), and category iii mine-protective building. Categorization of mine-proof technologies: external, internal, mine-protected electromagnetic pulses. 3 the external mine-protective device of the mine-protective device (direct-fired): a flasher, pull-down line, ground-laying device; the range of protection of the flasher is determined by the roller method, the radius of the roller is determined by the type of mine-protective building, i. E. 30 m, ii, 45m, iii, 60m; the exclusive line for direct-attacking mines and the artificial ground-to-ground distance from the entrance to and exit from the building or along the side of the sidewalk is not appropriate to be less than 3 m; the impact-to-ground resistance of an independent flash rod should not be greater than 10; and the impact-to-surface resistance of each line with a bolt shall not be greater than 10. Internal mine-protective devices: shield conductors, level-to-digital connectors, bulge protectors (spds), mine shielders
17. For electrical transformation equipment, mine avoidance devices are often used as a device to prevent thunderwave intrusion. When normal, the shield remains insulated from the ground; when a thunderstorm arrives, the shield is pierced and the lightning is brought to the ground; when the shock wave passes, the shield automatically recovers the insulation. Zinc oxide shield is widely used. Ii. Equivalent protection (7 measures), environmental hazard level control, including: replacement of flammable media, reduction of concentrations of explosive gases, vapour mixtures and reduction of oxidizer content. Process control: is an important method of eliminating electrostatic hazards, including the selection of materials, limiting the speed of movement of materials, and increasing the process of electrostatic dispersion. 3. Electrostatic sites: basic measures. 4. Wetting 5, anti-static additives 6, electrostatic neutrals 7, prevention of electrostatic hazards in humans (enhanced static safe management). Electrical installation safety technology i, variable power station safety 1 and the location of the variable power station to avoid a flammable explosive environment, appropriate for establishment at an enterprise
18 above the wind side, with sufficient fire escape and open. 2. Building structures: fire-resistant buildings; door opening and setting: electrical distribution units should be open on both sides, and at least two doors should be available for high- and low-composed over 7 m and over 10 m. 3. Spacing, screen protection and isolation: up to 60 kg of fuel for indoor filling equipment is allowed to be installed at partition intervals on both sides, up to 60,600 kg at intervals with blastproof walls and above 600 kg at separate intervals. Channels: two exits at 6 m for high-assembly devices; additional exports at 15 m for low-assembly devices. 7 signs: the key areas are marked by “stopping, pressure danger!” ii. Installation of main transformer equipment safety1, electrical transformer (1) transformer: fireproof doors; oil-impregnated transformers installed in residential buildings with a single capacity not exceeding 400 kv a; 10 kv transformer shell doors should not be less than 1 m and walls should not be smaller
19 at < 08m (not less than 12 m when an operating switch is installed); the surface of a naturally ventilated transformer room shall be higher than 11 m above the outer surface; the outdoor transformer shall be installed not exceeding 315 kv a and not more than 315 kv a; the secondary lead shall be placed on the stage; the bottom of the transformer on the column shall not be less than 25 m above the ground level and the naked guidance distance shall not be less than 35 m below the ground level; the transformer table shall generally not be below 05m, the height of the fence shall not be less than 1. 7 m below, the shell shall not be less than 1 m below and the operational fence shall not be less than 2 m below. (ii) operation of transformers: high voltage side voltage deviations of operating transformers shall not exceed the rated value of ±5, maximum imbalance currents of low pressure shall not exceed the rated current of 25, and upper oil temperatures shall not normally exceed 85; the colour of the suction in the respirator shall be light blue; the air relative to the place where the dry transformer is installed
20 the humidity shall not exceed 70%. 2. High pressure switches: high pressure breakers, high pressure isolation switches and high pressure load switches (1) high pressure breakers: the most important and complex of the high pressure switches. There are powerful arc suppression devices capable of connecting and breaking load currents under normal conditions, as well as cutting off load and short-circuit currents in case of failure with relay protection. High-pressure breakers must be used in combination with high-pressure isolation switches or isolation plugs, with circuit breakers connecting and cutting out electrical currents, and separation switches or plugs cutting off power sources. Therefore, the circuit must be cut by pulling the breaker and then pulling the quarantine switch; the circuit must be connected by closing the isolation switch and then closing the breaker. Mechanical or electromagnetic locking devices are often installed in 10kv systems. (2) high pressure isolation switch: high pressure isolation switch abbreviated switch. The separation switch does not have a dedicated anti-arc mechanism, which cannot be used to connect and break load currents, let alone cut short circuit currents. The separation switch is used primarily to disconnect the power supply to ensure the safety of overhauling and downing operations; copper and aluminium conductors are required to connect with copper aluminium; and operating high pressure isolation switches do not exceed 75 temperature points and institutions should be flexible. (3) high pressure load switches: there are relatively simple arc suppression devices used to connect and break load currents; they must be used in conjunction with high pressure smelters, which cut short circuit currents; no combustible material should be present in front. Iii. Electronic transfer (boxes) 1, electronic transfer (boxes)
