Abstract Based on the laws and characteristics of electric shock accidents in rural areas in China, this paper puts forward the protection methods that should be adopted for low-voltage safety of rural power grids, and emphasizes on the quality tracking of leakage protectors and measures for strengthening operation and management.
Keywords: leakage protector, configuration method, quality tracking operation management
After the transformation of rural power grids, the county-level power supply sector extended the management of rural low-voltage power grids to household energy meters. The safety problems faced by rural power grids are mainly caused by electric shocks and burns of rural residents. How to raise the level of safe electricity in rural areas to a new level is an important issue that needs urgent research.
1 The regularity and characteristics of electric shock accidents in rural areas
According to many years of operating experience, the law of electric shock accidents mainly manifests in the following aspects:
1.1 There are more electric shock accidents in the countryside than in cities
Although the level of electricity safety in China is increasing year by year, the rate of deaths from electric shocks is still much higher than that of the economically developed countries in the world. Electric shock accidents mainly occurred in rural areas, and electric shock accidents in rural areas were six times as many as in cities. The main reasons are: poor electricity use in rural areas, poorly equipped electrical equipment and unreasonable installation, low technical standards, poor management, and lack of electrical safety knowledge among farmers.
1.2 Low-voltage electric shock accidents are more than high-voltage electric shock accidents
High-voltage power grids are not easily accessible; low-voltage power grids have large coverage and many electrical devices. Therefore, people have more opportunities to access them. Coupled with poorly equipped and poorly managed personnel, people who are paralyzed and lack knowledge of electrical safety have even more opportunities to contact.
1.3 Electric shock accidents are seasonal
Every year from June to September is the season of high incidence of electric shocks. The main reason is that summer and autumn are rainy and wet, and the insulation of electrical equipment is declining. In hot weather, people often don’t like to wear work clothes and use insulated protective gears, and the human body suffers from excessive perspiration and skin resistance. decline. In addition, during the busy farming season, rural electricity consumption has increased, people’s chances of accessing and operating electrical equipment have increased significantly, the disadvantages of various conditions, and the subjective paralysis has become a season of high concentration of electric shocks.
1.4 Frequently Occurrence Sites of Electric Shock Accidents
The single-phase electric shock accident has more than two phases (relative phase) electric shock accidents, and the accident points mostly occur at branch lines, access lines, ground climbing lines, joints, lamp caps, plug sockets, switchgear, control appliances, fuses, etc. . These are parts that are easily accessible to people and are prone to short circuits, grounding, and leakage.
1.5 Causes of Electric Shock in Rural Areas
1.5.1 Equipment is not qualified
The low-voltage overhead line is too low, the height to the ground and the distance to the building do not meet the requirements of the regulations; the fixed part of the low-voltage pole wire is unreasonable, the process is poor, and there is no insulator; the waste aluminum wire or wire is used as the wire; the joint is unqualified; The electrical equipment metal shell is not grounded or poorly grounded; the damaged or aged insulation wire is used as the household line or the electrical lead; the installation distance of the broadcast line and the power line does not meet the requirements and causes mutual connection; the screw base and the light bulb do not meet the standard requirements. In addition, the neutral wire and the phase wire are connected incorrectly to expose the metal screw of the lamp bulb; the one-way switch is incorrectly connected to the zero wire, so that the lamp head is electrified for a long time.
1.5.2 Equipment is in disrepair
Damaged or damaged insulation poles of lead wires and lead wires; Corrosion of lead pole wires, aging of joints and wires, resulting in broken wires and rods; electrical damp, insulation aging; protective earthing of the shell or disconnection of the neutral wire; rubber insulated wire protection The sleeves, flexible cable sheaths and insulation layers are broken, and the flexible cable joints' insulation dressings are improperly selected or loosely detached; the open type load switches (plastic cover gates), the insulating cover of the lamp caps and sockets, and the cover are lost or broken.
1.5.3 Illegal Operation
Suspend the power cord or repair the electrical equipment while galvanically connected; without cutting off the power supply, electrify the electrical equipment that has electrical leakage faults; install the house or lifting equipment under the overhead line without security measures; operate the equipment without power supply, and work without authorization on the power outage equipment; In violation of safety regulations, we will stop transmission of electricity when we make an appointment.
1.5.4 Self-disruption and illegal use of electricity
Attach the lighting of one line and one place; directly use the wire to hang and hook the overhead line to use electricity; privately set up the power grid for fish and electricity; use the old wire to pull the ground to climb the line and block the waist line.
1.5.5 Lack of safe electricity knowledge
Pull the broken live conductors with bare hands, and drag the person with bare hands; connect the three or four-pole plugs and sockets to the phase conductors, causing the shell of the electrical equipment to become live; climb the pole or transformer; Operate on the ground; wrap the conductor joints or damaged parts with non-insulators; connect the plugs with wires directly to the power line; do not use safe voltage for electricity in wet places; operate charged equipment at will.
1.5.6 Do not install leakage protector or use poor quality leakage protector
Before the agricultural reform, the installation rate of household security devices was very low, and the rural network circuit with large leakage currents chose the general current-type total security device to operate too much, and the setting value of leakage current was too large to protect personal safety. Although the installation rate of household security devices increased after the agricultural reform, many counterfeit and counterfeit products could be flooded into rural power grids, and electric shocks and injuries in rural areas continued to occur.
1.6 There are many electric shock accidents in rural overhead lines, access lines and temporary electricity lines
According to statistical data analysis, the number of electric shock accidents on the rural overhead lines, access lines, and temporary electric lines exceeded 70%. Among the many factors that constitute an electric shock accident, only one causes an electric shock accident of less than 10%, and more than 90% of electric shock accidents are caused by two or more factors. Therefore, it is very important to strengthen the education of electricity safety management and electricity safety knowledge.
It should be pointed out that before and after the rectification of rural power grids, the law of electric shock accidents may change. We should continue to analyze and sum up the laws in practice to provide a reliable basis for formulating and improving safety measures and ensuring safe use of electricity.
2 Leakage protector configuration and selection
We should combine the current situation of China's rural low-voltage power grids. We must not only do a good job of protecting electrical power, reduce electric shocks, but also increase the reliability of power supply. This is a comprehensive requirement for leakage protection. The facts have proved that: The adoption of a leakage protection grade protection method is the fundamental way to achieve the above requirements, and it is also an inevitable trend of China's leakage protection development. According to China's low-voltage power grid power supply, economic conditions and the production of leakage protection devices, the use of two-pole leakage protection in the low-voltage power grid is feasible and most effective.
First, the installation rate and operating rate of the last-stage leakage protector should be increased. The last-stage protection is to prevent direct contact with electric shock as its main objective. Each of its protection surfaces is small and does not interfere with other users. The high-sensitivity and fast leakage protection devices with a rated leakage current of no more than 30mA should be selected for mobile electrical equipment and power tools that are widely used by urban and rural households at household entrances. The leakage protector selected for single-phase power consumers shall also be equipped with over-voltage protection function to prevent the occurrence of abnormalities when the three-phase four-wire system zero line is disconnected and the receiver line is incorrectly connected to a 380 V line voltage. Overvoltage damage to household appliances. It is best to use a protector with leakage, overvoltage, and overload short-circuit protection so that all abnormal conditions of a single-phase consumer can be protected. For places where secondary damage may occur after electric shock, such as high-altitude operations or electrical equipment used on river banks, a fast leakage protection device with a leakage current of 10 mA may be installed.
The second level of protection is total system protection or branch protection. This protection device can be installed at the low-voltage outlet of a distribution transformer or at the beginning of each branch line. Its protection scope is the main line (or branch line), the down-home line and the in-home line of the low-voltage power grid, and it also serves as the end Grade leakage protector back-up protection. The rated leakage action current shall be determined based on the actual leakage current of the protected circuit and equipment.
The two-stage leakage protection device constitutes a leakage protection network, and the first-stage protection device provides direct contact protection for some occasions where the conditions are harsh and the danger of high electric shock is high. The second-stage protection device expands the leakage protection coverage. Improve the safety level of the entire low-voltage power grid. There should be a reasonable cooperation between the two levels of protection, and there should be a step difference between the leakage current and the operating time. It is recommended that the rated leakage current of the upper leakage protection device be 2.5 to 3.0 times the rated leakage current of the next stage, and the action time of the upper leakage protection device be increased by one action level compared to the next stage of the operation time, which is approximately 0.1 to 0.2 seconds. .
3 Leakage protector quality tracking
Leakage protector as a national electrical product that enforces safety certification, its quality is directly related to the safety of the user's life and property. Therefore, the quality of the leakage protector has always been the concern of the user. In particular, since the implementation of the “two reforms and one price†of rural power grids, the demand for leakage protection devices has increased rapidly. Many leakage protection devices with stable quality, good performance and complete functions have been widely used by users, but many poor quality products have also entered the agricultural industry. network. Therefore, we must strengthen and carry out supervision on the quality of leakage protection devices, implement dynamic management, improve the quality awareness of production operators, and prevent substandard and counterfeit products from entering the low-voltage power grid. Here are some suggestions on how to strengthen and standardize the quality supervision of leakage protection devices:
(1) Adherence to the safety certification of leakage protection devices and mandatory supervision and management are prerequisites and foundations for ensuring their quality. From the quality tracking of the products that have obtained the safety certificate, the stability of the product quality is obviously better than that of the products that have not been certified. This shows that carrying out the safety certification plays an important role in the future quality of the product. .
(2) Conducting tracking and supervision of leakage protector quality is an effective measure to promote and ensure product quality. The monitoring and monitoring of leakage protector quality is carried out in order to dynamically supervise the quality of the leakage protector in order to judge its quality. Therefore, the quality tracking and supervision of the leakage protector is the main link for the quality supervision of the leakage protector. To track the quality of leakage protectors should mainly do the following aspects:
1) Guarantee the quality of the quality of the follow-up inspection agencies to extract the authority of the test and technical assessment. The quality of the quality assurance follow-up agency's verification testing capability and its reliability review will directly affect the accuracy of its follow-up product quality assessment. Therefore, ensuring the quality of the quality supervision authority is the key to carrying out quality tracking and supervision.
2) Further intensify efforts to track and supervise the quality of certified products. Quality follow-up and supervision should adhere to the "three publics" (fair, fair, open) and "three unifications" (unified supervision standards, unified supervision methods, unified inspection items) Principles, ensure the seriousness of quality tracking and supervision. To carry out quality tracking and supervision must have strict and standardized working procedures, and clearly define the conditions for participating in quality tracking products and relevant information that companies should provide, publicly disclose the items of leakage current protector quality tracking test, the standards adopted and the principles of technical evaluation, and publish sampling The method and quantity. For example, in Zhejiang Province, the quality tracking test for leakage protectors has been carried out for many years. From 1999, Henan Province firstly recommended users of grass-roots county bureaus to the provincial bureaus according to their use conditions, and the provincial bureau commissioned the testing agency to test the qualifications. The two provinces currently conducting quality tracking tests are conducted according to national standards, and the selected projects highlight the main features of the leakage protector.
3) Promptly announce product quality inspections and propose quality improvement suggestions for the tested products are an important part of quality tracking and supervision.
4) Periodically reviewing quality improvement products after quality improvement is another important part of quality tracking and supervision. It is an effective measure to promote product quality defects by manufacturers to improve product quality. It can also reflect production, technology, and quality management levels of production companies. For example, in Zhejiang Province, products with quality defects in the inspection are randomly sampled and rechecked after 3 to 6 months of quality improvement suggestions, and the quality of the re-inspection is announced.
(3) Strengthening the legal system and insisting on the use of laws to carry out quality supervision is also an important method to ensure the quality of leakage protectors.
Strengthening and improving the legal awareness of quality supervision departments and producers and operators is the basis and the first condition for carrying out legalization and standardization of quality supervision. It is directly related to whether quality supervision can be conducted in accordance with the law, whether legal protection can be used to protect the reputation and use of qualified products. The rights and interests of the people, therefore, insist on relying on the law to carry out quality supervision has a very effective role in promoting product quality improvement. The quality supervision department reminds and warns the user to use qualified brand products preferentially to protect the qualified product manufacturing enterprises while preventing and cracking down counterfeit products. In addition, the quality of the leakage protector is linked to the legal liability that should be borne. For example, in Zhejiang Province, the forthcoming local regulation “Measures for the Treatment of Electric Shock Compensation in Zhejiang Provinceâ€, it has been clearly stated that the production and management of electrical products that endanger personal safety will be The investigation of legal liability for leakage protection devices is one of them, and it is recommended that countries should also issue corresponding laws and regulations.
(4) Timely enhancement of quality information feedback and increase of science and technology investment are important means to improve and ensure product quality.
The quality supervision department and the use management department shall strengthen the monitoring of the quality status of the leakage protection devices that have been put into operation and the investigation of the company's after-sales service, and provide feedback on the information, and timely feedback the operation and quality of the leakage protection devices to the production enterprises. Actively support and encourage the development of new products by production companies and scientific research institutions, and constantly improve the function of leakage protection devices.
(5) It is recommended to set up a National Association of Earth Leakage Current Protectors and specify the units with test conditions to conduct annual sampling tests on the products of leakage protection device manufacturers entering the rural network, and to announce the recommended production plants and product models for product quality, Comprehensive monitoring of prices, after-sales services, etc., should prevent counterfeit and counterfeit products from flowing into the rural network, and also stop unfair competition with low prices and low quality.
4 Leakage protector operation management
To make the installed leakage protection device play a proper role in protection, it is necessary to strengthen the operation and management of the power grid. The power departments at all levels should pay attention to this work. Especially during and after the rectification of rural power grids, the county electric power department maintained and used household electric meters for rural households. The related safety issues prompted them to vigorously strengthen management. All power departments at or below the provincial level, including township (town) power stations, shall be equipped with special (part-time) personnel to manage grid safety and leakage protection devices. When using a certain product, the user must test the function and performance of the product before use. Only products that pass the functional performance test can be allowed to be installed on site. The county-level power departments should be equipped with the necessary test equipment and qualified personnel to ensure the implementation of this measure. At the same time, a leakage protection device maintenance point shall be established separately or in segments to ensure timely repair of the damaged leakage protection device. The county and township power departments shall regularly check the operation of the leakage protector. The last stage leakage protector belongs to the user's assets, and the power department is responsible for propagating, guiding, inspecting, supervising its installation and use, and accelerating popularization. In order to ensure quality and facilitate management, the conditions can be uniformly purchased and installed in a unified manner so as to build a file. The total leakage protector is the asset of the power sector, and should use the leakage total (branch) protector with a high rate of operation and reasonable coordination with the final stage of protection. Every installation and commissioning of the total leakage protector shall be clearly operated by the responsible person, equipped with trial running records, correct recording of commissioning test conditions, regular trial jumping conditions, tripping during operation, restoration of power transmission time, causes of failure and abnormalities. Situation and so on. The county-level power sector should also provide field test equipment equipped with leakage protection performance indicators for the township power supply stations and organize training for rural electricians. The Township Power Supply Institute conducts an on-site test of the actual leakage current and the total leakage protector performance of the power distribution station every year, and makes records and evaluations to ensure that the total leakage protector is in good condition.
For the installation and operation of the leakage protector, the county-level power departments shall make the following provisions for township-level power supply stations and users:
(1) Each farmer and unit that uses electricity is required to install a leakage protector in accordance with regulations; otherwise, no power supply will be provided.
(2) All newly installed leakage protectors must comply with national standards, have national certification marks, and their technical parameters can be matched with the protected equipment. Do not purchase unqualified products.
(3) The overlap of the tripping of the leakage protector is unsuccessful. It is necessary to find out the reason to eliminate the fault before transmitting power, and it is forbidden to send power forcibly. It is not allowed to energize in the unprotected state.
(4) No person shall remove or remove the earth leakage protector under any pretext. Otherwise, no electricity will be supplied. All the consequences shall be the responsibility of the dismantled person.
(5) Persons who have caused personal injury, death, or equipment damage in violation of regulations shall be given criticism, education, punishment, and criminal responsibility, depending on the circumstances.
The installation and operation data of the leakage protector should be collected, summarized, saved and reported as follows:
(1) The township power supply station shall establish a total leakage protector ledger, a final leakage protector statistical table, and ensure that it is in line with the site. Six months or one year for collection, the summary accounts should include: number of transformers in each district, number of low-voltage outgoing lines, number of leakage protection devices installed, number of models, manufacturer, date of manufacture, and total installed leakage protection rate of the township. The number of damaged replacements, the number of new installations, the number of end-stage leakage protectors and the installation rate, etc. The summary table is reported to the county-level power department, and a file is kept for a long time.
(2) The township power supply station shall respond to the total leakage protector test run every month and record it for summary. The summary accounts shall include: the total number of leakage protection relays of various models and the number of permanent fault trips, the classification of failure causes, the annual summary records of twelve months will be summarized annually, and one annual summary will be reported to the county-level power sector, and one shall remain. Long-term preservation.
(3) The township power supply station shall conduct a summary of the total leakage protector performance test records once a year. The summary subjects shall include: the rated leakage current of the various types of total leakage protection devices, the number of unqualified current failures, the number of exceeding the operating current, and the rated leakage current The number of operating hours under the standard exceeds the number of standard units, and the number of rated tripping currents, the number of failed rated currents, the number of abnormally exceeded operating hours under the rated operating current, and the number of failed locking functions are added. Field records are generally kept for three years to facilitate comparison before and after. The annual report sums up to the county-level power department, and a file is kept for a long time.
(4) The county-level power department shall also report and report to the municipal power department after receiving the township-level report. The municipal-level power department shall submit the report to the provincial bureau when receiving the county-level report. The province, city, and county shall keep the subordinates for long-term preservation. Reports and summary reports. In this way, it is possible to comprehensively grasp the status quo and operational status analysis and existing problems of leakage protectors at all levels of the power sector, and to provide a reliable basis for decision-making at higher levels.
In addition, when a personal injury or death accident occurs within the protection scope of the leakage protector, the site should be protected before the accident investigation and the leakage protector must not be removed. The power department shall check the performance of the leakage protector and the implementation of the management regulations. If the function and performance of the leakage protector are normal, the dead zone of the leakage protector cannot be ignored, such as the possibility of electric shock between phases or phases. In order to improve the safety of the electric leakage protection of the electric leakage protector and ensure the reliability of the electric supply, in addition to strengthening the management of the electric leakage protector itself, it is also necessary to strengthen the management of the low-voltage electric network so that the level of the rural electric network equipment after the reform can be improved. The safety level has a qualitative leap.