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Safety guarantee of smart meters

As countries around the world compete to deploy intelligent transmission systems, how to ensure the safety of these systems has become an important issue. Although there are few specific standards for smart grid security protection, power companies have begun to make a big deal in the early stage of system deployment - equipping IT systems for data collection and analysis, using advanced communication technology to transmit data, and using endpoints (such as smart meters) and grid health monitoring system to generate raw data. Although the security issue has become a widespread concern in recent years, there is still much work to be done, especially the "endpoint" protection, such as the security protection of electricity meters and power grid sensors. This article outlines the threats faced by these endpoints and the security technologies to deal with these threats. Security threats There is no doubt that there are many security risks faced by smart grids, but they can be roughly divided into two categories. The first category is individual attack, which means that the target of the attacker is smart grid data to gain their own interests - for example, stealing electricity bills, or concealing the production of illegal drugs. The purpose of individual attack is not to disrupt the power grid management, but to gain the interests of an individual or group. The second type of attack refers to activities that pose a threat to society, including activities that attempt to disrupt the operation of the power grid. This may be an attack on the power grid itself (large areas misreport energy consumption, resulting in the tension of the entire power grid's capital chain); It may also be an attack on the society (for example, terrorist attack), resulting in power grid paralysis and user power failure. In case of power failure, production and financial losses will be immeasurable, especially in extremely hot and cold climates, and will pose a threat to human life safety.

Precautions for megohmmeter

1. It is forbidden to measure the insulation resistance in lightning or near the high-voltage equipment. It can only be measured when the equipment is not live and there is no induction electricity. 2. During telemetering, no one can work on the tested equipment. 3. The megohmmeter wires should not be twisted together. They should be separated. 4. It is forbidden to touch the megger with hands before it stops rotating or before the tested equipment is discharged. Do not touch the metal part of the lead when removing the wire. 5. At the end of measurement, discharge large capacitance equipment. 6. The insulation of the measuring flexible wire led from the megger terminal should be good, and the appropriate distance should be kept between the two conductors and between the conductor and the ground to avoid affecting the measurement accuracy. 7. In order to prevent the leakage resistance on the surface of the equipment under test, when using a megger, the intermediate layer of the equipment under test (such as the inner insulation between the cable shell cores) should be connected to the protective ring.

Difference between digital megohmmeter and pointer megohmmeter in practical application

Difference between the use of digital megohmmeter and pointer megohmmeter in practice 1. Accuracy: The accuracy of digital megohmmeter is generally 0.2 and 0.5, and 0.2 is higher than 0.5. However, the accuracy of the pointer megohmmeter is 1.5, which means that the small accuracy of the ammeter is 1.5% of the large range. For example, if the large range is 100A, the small accuracy is 1. It can be seen that the precision of pointer meter is far higher than that of digital display meter. But does the pointer watch have no merit? The directness of the pointer swing and its swing speed amplitude can sometimes objectively reflect the measured size; Although the reading of the digital meter is visible, the process of digital change seems particularly chaotic and is not easy to watch. 2. There are usually two batteries in the pointer megohmmeter, one is low voltage 1.5V, the other is high voltage 9V or 15V, and its black pen is positive compared with the red pen. Digital megohmmeter usually uses a 6V or 9V battery. In the resistance range, the output current of the pointer meter is much greater than that of the digital meter × 1 Ω gear can make the speaker emit a loud "da" sound × 10k Ω gear can even light up the light emitting diode (LED). 3. In the voltage range, the internal resistance of the pointer megohmmeter is relatively small compared with the digital meter, and the measurement accuracy is relatively poor. Some places with high voltage and low current can not even be accurately measured, because its internal resistance will affect the circuit under test (for example, the measured value will be much lower than the actual value when measuring the accelerating voltage of the TV picture tube). The internal resistance of the digital megohmmeter is particularly large, at least at the megohm level, which has a very small impact on the circuit under test. However, the extremely high output impedance makes it vulnerable to the influence of induced voltage, and the data measured in some places with relatively strong electromagnetic interference may be false. Therefore, it is particularly difficult for pointer megohmmeter to obtain particularly high accuracy. In addition to the influence of the full bias current error of the meter head and the error of the shunt divider resistance on the meter, there is also the so-called linear error, which is the error caused by the uneven sensitivity of the meter head. In today's society, more and more people use digital display meters to replace pointer meters, which has reached the goal of high accuracy and direct reading

Use and safety precautions of megohmmeter

Core tip: When selecting a megohmmeter, you should also note that the scale value of some megohmmeters is not from zero, but from 1m ω Or 2m ω Start. This megger is not suitable for measuring the insulation resistance of low-voltage electrical equipment in a humid environment, because when the insulation resistance of electrical equipment is less than 1m ω The correct reading will not be obtained. 1. When using the megger, it should be placed stably to avoid shaking the generator handle and the meter body to affect the reading. If there is a megger with horizontal adjustment, adjust the horizontal position first. When selecting a megohmmeter, it should also be noted that the scale value of some megohmmeters is not from zero, but from 1m ω Or 2m ω Start. This megger is not suitable for measuring the insulation resistance of low-voltage electrical equipment in a humid environment, because when the insulation resistance of electrical equipment is less than 1m ω The correct reading will not be obtained. 1. When using the megger, it should be placed stably to avoid shaking the generator handle and the meter body to affect the reading. If there is a megger with horizontal adjustment, adjust the horizontal position first. 2. The special measuring wire for the instrument or two single-core multi-stranded flexible wires with high insulation strength shall be used, and stranded insulated flexible wires shall not be used. 3. Before measurement, open circuit test and short circuit test shall be conducted with a megger. That is, open the "L" and "E" terminals, shake the generator handle to reach the rated speed, and the pointer should point to the "∞" position; Then, short "L" and "E" and shake the handle. At this point, the pointer should point to the "0" position. 4. The electrical equipment to be tested must be powered on, and others are not allowed to approach the equipment to be tested during measurement. 5. Before measurement, the measured equipment must be short-circuited to the ground, especially capacitive electrical equipment, such as cables, large-capacity motors, transformers and capacitors. If it is not discharged, electric shock may occur. 6. During wiring, the "E" end shall be connected to the electrical equipment shell or ground wire, and the "L" end shall be connected to the conductor under test. When measuring the cable insulation resistance, connect the cable insulation layer to the "G" terminal. If the insulation resistance of the equipment is measured in wet weather, shielded terminals shall also be used and connected to the insulation support to eliminate the impact of leakage current on the insulation surface on the measurement of insulation resistance.

The research on key technologies for modular construction of new generation intelligent substation has passed the acceptance smoothly

Recently, the State Grid Corporation of China (SGCC) science and technology project "Research on Key Skills for Modular Construction of New Generation Intelligent Substation", led by the China Electric Power Research Institute, passed the acceptance smoothly. The project has completed all aspects of development, planning, manufacturing, installation and commissioning, which is conducive to the standardized, large-scale and high-quality construction of intelligent substations. "Research on key skills of modular construction of new generation intelligent substation" is the key work of State Grid Corporation of China during the "12th Five-Year Plan" period. The traditional construction form of substation has been unable to adapt to the new requirements, which restricts the improvement of the construction power, engineering safety quality and technological level of intelligent substation. The project has completed the research on key skills such as the overall modular construction scheme of intelligent substation, installed buildings and structures, modular secondary combination equipment, and secondary system information model specification library. Innovate and propose a new form of intelligent substation construction, research and develop prefabricated cabinet-type secondary combination equipment, select prefabricated optical and cable skills, and complete on-site wiring "plug and play"; Standardize the secondary equipment and system information model of the substation, and complete the centralized control of the secondary system information model; Select modular intelligent integrated equipment, optimize the main wiring and general layout, and form a typical modular construction plan for a new generation of intelligent substation. Selecting the skill form and construction form of intelligent substation can complete the useful connection of engineering planning, factory processing, civil construction, device commissioning and other links, and reduce the engineering construction cycle by about 50-60%. The benefits in terms of enclosure area, building area, number of panels and cabinets, and length of optical cables and other aspects are significant: the first batch of five modular construction smart substation pilot projects have an average saving of 14.24% in the enclosure area compared with the conventional project, 22.18% in the building area compared with the conventional project, 24.60% in the number of panels and cabinets, and 38.20% in the length of optical cables compared with the conventional project, The cable length is 28.43% less than that of conventional projects. In the modular construction of intelligent substation, many of the primary buildings and secondary equipment compartments use prefabricated components, factory processing and manufacturing, on-site installation and construction, reduce on-site wet work, complete environmental protection construction, improve construction power, and save a lot of engineering water and daily water. The project effect has been successfully applied to many intelligent substations in China. Through the research of this project, a number of forward-looking and practical skills effects have been formed, a number of independent intellectual property rights have been obtained, a number of smart substation skill specifications have been drawn up, and breakthroughs have been made in the modular construction of smart substations, which fundamentally promote the modular construction of smart substations with compact structure, functional integration, information integration and convenient operation and maintenance.

Problems in the development of domestic power test instrument industry

According to statistics, the electric power test instrument industry accounts for less than 4% of the output value of the electronic industry, while the output value of the electronic industry only accounts for about 3% of the world's total output value, but the added value brought by the new technology driven by the test instrument can account for 68% - 74% of the world's annual added value. 1. It is not only about money and people, but also about the accumulation of ideas, thinking and technology as well as the importance of national strategy to solve the problem of backwardness of domestic power testing instruments. 2. The level of power testing instruments directly affects the independent innovation ability and strategic layout of China's defense technology and related electronic industry. 3. The problem of electric power test instruments is also a concentrated reflection of the country's lack of software and hardware. The prosperity of test instruments cannot be separated from the improvement of relevant software and hardware strength. 4. To solve the problem of backwardness of test instruments, it needs the joint efforts of state-owned scientific research institutions and enterprises, as well as private and private enterprises, and the gradual establishment of a series of test systems from standards to architecture to concepts. Yangzhou Kaier Electric (www.yzkedq. com) is committed to the promotion and application of products and technologies of test equipment in the fields of transformer DC resistance tester, AC/DC test transformer, DC high-voltage generator, induction withstand voltage test device, etc.

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