1. Introduction Since the 1990s, a new type of pollution (electromagnetic waste pollution) has been placed on the environmental protection agenda. Unlike other types of pollution, electromagnetic waste pollution is not visible, tangible, or odorable. It is distributed in the air and lurks underground, causing malfunctions, breakdowns, and even damage to aircraft, ships, vehicles, and electrical and electronic products; it also harms human health, leading to various diseases. It is an invisible killer, a "sea, land, and air terrorist" in the "electromagnetic world." Furthermore, it is not bound by time, space, or national borders and can attack humanity at any time. The economic losses and harms caused by electromagnetic waste pollution are even greater than those caused by other types of pollution. For example, in the 1970s, the "air defense computer system" developed by the United States issued two emergency alarms during operation, indicating that the Soviet Union was about to attack the United States. This caused missiles at the base to be ejected from their silos and mounted on launch pads, bombers and fighter jets to start up, and soldiers to climb onto troop transport vehicles, preparing for battle. The scene was instantly chaotic, as if facing a major enemy. Later, the central control room discovered that the central computer had been falsely triggered by electromagnetic interference, resulting in a false alarm. For example, during a settlement process, a bank in New York City suddenly discovered it owed another bank a staggering $35 billion. Upon hearing this, the bank's general manager fainted from shock. After a thorough investigation, it was found that a computer malfunction, also caused by external electromagnetic interference, had occurred. In China, several years ago, CCTV reported on the situation near Baiyun Airport in Guangdong, where numerous paging stations caused strong electromagnetic interference, preventing passenger planes from taking off or landing. There are many other examples of the dangers of electromagnetic interference. Even more worrying is that in heavily guarded warehouses and military locations, even a small spark could cause explosions in oil depots or munitions depots. Strong high-frequency electromagnetic fields can also trigger automatic missile launches. The consequences of such incidents would be no less severe than the 9/11 attacks in the United States. Clearly, the serious electromagnetic pollution caused by electromagnetic waste has become a major public nuisance and hidden danger in the social environment, demanding the serious attention of governments and militaries worldwide. 2. The Meaning of Electromagnetic Compatibility Electromagnetic compatibility, as the name suggests, means "compatibility," "accommodation," or "tolerance." However, electromagnetic compatibility (EMC) does not refer to the compatibility between electricity and magnetism. Electricity and magnetism are inseparable and coexist in a physical phenomenon and environment. The International Electrotechnical Commission (IEC) defines EMC as: the ability of signals and interference to coexist without impairing the information contained in the signal. The purpose of studying electromagnetic compatibility is to ensure that electrical components or devices can function normally in an electromagnetic environment, and to study the mechanisms and preventive measures against the harm caused by electromagnetic waves to social production activities and human health. It is a highly comprehensive interdisciplinary science closely related to the electromagnetic environment. It is mainly based on electrical and electronic science theories to study and solve various electromagnetic pollution problems. Its theoretical foundation includes mathematics, electromagnetic field microwave theory, antennas and radio wave propagation, circuit theory, signal analysis, communication theory, materials science, biomedicine, electronic countermeasures, communication geology engineering, etc. In short, electromagnetic compatibility technology is a constantly developing new comprehensive discipline and a highly engineering-oriented applied technology. Electromagnetic compatibility (EMC) technology research has two characteristics: a. It involves a wide range of areas, including various electrical electromagnetic interferences in nature, as well as the design, installation, and electromagnetic interference between various electrical appliances and electronic equipment; b. It is technically difficult because the sources of interference are increasing and the propagation paths are also diverse. Electromagnetic interference problems are common in military, power, communication, transportation, and mining enterprises. Electromagnetic interference is very harmful to systems and equipment. In the power supply network of the power system, the impact load generated by the user's high-power electric arc furnace, if the electromagnetic compatibility problem is not considered in the design, may cause a great impact on the power grid, which will increase the potential harm that the electromagnetic field of the power grid may bring to the power system equipment and user electrical equipment. 3. Main sources and hazards of electromagnetic pollution 3.1 Main sources of electromagnetic pollution The sources of electromagnetic pollution include: (1) lightning (including strong electromagnetic pulses such as nuclear explosions); (2) static electricity and all electrical actions (including normal and abnormal) processes. For example, these situations include: (1) satellite communication and intelligent aircraft navigation; (2) lightning protection for high-rise buildings, communication wireless towers, ultra-high voltage transmission lines, oil depots, port buildings, forests, and historical sites; (3) harmonics in factory automated production lines and electric traction power supply systems, large medical equipment, physical instruments, household instruments, power tools, mobile phones, remote control instruments, integrated modules, printed circuit boards, etc.; (4) the relative friction of insulating objects can also produce terrible electrostatic effects. For example, the relative motion between high-speed aircraft and the atmosphere, the entanglement of synthetic materials, the high-speed transmission of fluids (oil, natural gas, etc.), and the friction between chemical fiber fabrics and the human body. Due to the concealment of static electricity accumulation and the suddenness of the release process, the degree of harm caused is no less than that of harmonics and strong electromagnetic pulses. In short, wherever there are electromagnetic phenomena, there are EMC problems. In addition to atmospheric electromagnetic garbage sources (such as lightning), other electromagnetic garbage sources are all around us. With the advancement of science and technology, various electrical and electronic products, such as broadcasting, communication, and information technology equipment, engineering and medical equipment, electronic measuring equipment, and household appliances, are widely used. While these products benefit humanity, they also emit radiated and conducted electromagnetic interference, as well as electromagnetic interference generated by the discharge of static electricity from the human body. All of these pose a threat to other electrical products and human life. During operation, these products emit "electromagnetic waste" into the air through radiation, disturbing other electrical products; they inject "electromagnetic waste" into the ground through filters, forming ground currents and causing common-mode interference to other electrical products; and they transmit "electromagnetic waste" to the low-voltage power grid through power lines, disturbing the power grid. In other words, the source of electromagnetic waste comes from electrical and electronic products that emit strong electromagnetic interference signals. If the serious sources of electromagnetic waste are not addressed, the electromagnetic environment will become even worse. 3.2 Main Hazards of Electromagnetic Pollution 3.2.1 The Impact of Electromagnetic Pollution on the Human Body In recent years, the impact of electromagnetic pollution on human health has increasingly attracted people's attention. Scholars from Japan, Sweden, and the United States have proposed minimum permissible values ​​for magnetic field strength in human living environments. Internationally, the electromagnetic environment used by electrical and electronic products or systems is divided into two categories, A and B, with respective limits on electromagnetic emissions. Category A environments are industrial environments, including those with industrial, scientific, and medical radio frequency equipment; environments with frequent disconnection of large inductive or capacitive loads; and environments with high current and strong magnetic fields. Category B environments include residential areas, commercial areas, and light industrial environments, such as residential buildings, retail outlets, commercial buildings, public entertainment venues, and outdoor locations (e.g., gas stations, parking lots, amusement parks, parks, stadiums). The health hazards to humans are divided into somatic effects and population effects. Somatic effects are further divided into thermal and non-thermal effects. The mechanism of thermal effects is relatively well understood: after the human body is exposed to electromagnetic radiation, water molecules move rapidly with the change in the direction of the electromagnetic field, causing the body temperature to rise. If a large amount of radiation energy is absorbed, and the body's temperature regulation cannot dissipate the absorbed heat in time, it will cause a rise in body temperature and subsequently lead to various symptoms. However, the mechanism of non-thermal effects is not fully understood. These effects do exist, referring to situations where absorbed radiation energy is insufficient to raise body temperature, yet still causes physiological changes or reactions. These effects include diseases such as neurasthenia, and electromagnetic radiation can even cause cancer. Population effects are not observable in the short term; they may make humans smarter, or conversely, hinder human development. The effects of electromagnetic fields on the human body are related to their frequency. For a long time, scholars from various countries have held different views on whether power frequency electromagnetic fields affect the central nervous system. Numerous domestic and international occupational health surveys on high-voltage and ultra-high-voltage transmission lines and substations indicate that neurasthenia and memory loss are the most common symptoms among workers exposed to power frequency electromagnetic fields. Currently, it is believed that the effects of power frequency electromagnetic fields on the central nervous system are mainly caused by the electric field, a view supported by animal experiments. Regarding the relationship between power frequency electromagnetic fields and tumor development: many studies have found that while occupational exposure to electromagnetic fields may increase the risk of tumors, especially leukemia, lymphatic system tumors, and nervous system tumors, this risk is not high and is not statistically significant. However, it should be pointed out that if other strong carcinogenic factors are present in the production environment at the same time, the effect of power frequency electromagnetic fields cannot be ignored. The effect of power frequency electromagnetic fields on reproduction: Statistics show that the use of electric blankets in early pregnancy is associated with an increased incidence of miscarriage, but the incidence of miscarriage is reduced when electric blankets are used in mid-pregnancy. Nordstrom et al. reported for the first time abroad: A retrospective survey of 542 power plant workers found that the proportion of children with congenital malformations was increased in those whose fathers worked in high-voltage dispatch rooms. The effects of radio frequency electromagnetic fields on the human body: (1) Effects on the nervous system: After exposure to high frequency electromagnetic field radiation, an increase in the olfactory threshold and a prolonged dark adaptation event will begin to appear. It has been reported that long-term exposure to high-intensity radio frequency electromagnetic radiation may cause certain changes in electroencephalograms. (2) Effects on the cardiovascular system: After long-term exposure to high frequency electromagnetic fields, the incidence of hypotension or low blood pressure will increase. (3) Effects on the endocrine system: A hygiene survey was conducted on 160 female workers in a plastic factory in Shanghai who were frequently exposed to high field strength (engaged in high-frequency dielectric heating operations). It was found that these female workers had a significant increase in non-lactational lactation symptoms and a significant increase in menstrual cycle abnormalities. These were mainly caused by neuro-humoral disorders. Microwave electromagnetic fields can cause acute microwave radiation damage to the human body. When exposed to excessive microwave radiation, it may cause acute damage to several tissues and organs of the human body. Acute microwave damage generally includes headache, nausea, dizziness, insomnia, and local burning sensation from radiation. However, these symptoms usually disappear after a period of rest. Prolonged exposure to low-intensity microwave radiation can cause some physiological dysfunctions and fluctuations in biochemical indicators. Table 1 shows the public exposure limits (GB8702-88). [align=center] Table 1 List of maximum permissible exposure values ​​for the human body[/align] 3.2.2 Interaction of electromagnetic pollution from electronic and electrical products Electronic and electrical products are generally quite complex, and most have a wide variety of subsystems. External electromagnetic radiation and crosstalk between internal components, subsystems, and transmission channels seriously threaten the stability, reliability, and safety of products and their data. Statistics show that interference-related accidents involving electronic and electrical equipment account for approximately 90% of all accidents. Electromagnetic interference primarily manifests as electromagnetic radiation, which has two meanings. First, it refers to the unintentional interference generated by the main equipment and its auxiliary equipment, radiating or conducting to the outside world. This not only leaks to the outside but also exceeds the limits over a relatively wide frequency range, threatening radio broadcasts, televisions, and other household appliances. The other meaning of leakage refers to the leakage of useful information. While this may not be a strong signal, its impact is often determined from relative relationships. When interested in certain information, interceptors will use amplification, feature extraction, decryption, or decoding methods to obtain it. Even very small signals can be intercepted using modern information processing technology, and the harm caused by interception is no less than that caused by interference with equipment operation. Electromagnetic radiation also manifests as narrowband and broadband interference to surrounding electronic systems, potentially causing information leakage problems. The main types of interference caused by electrical equipment to the surrounding environment include: (1) Corona discharge: This is a high-frequency electromagnetic noise caused by the discharge into the air due to the large potential gradient on the conductor surface. The main components of its spectrum are below a few megahertz. Its intensity, expressed in dB, increases with the increase of the potential gradient. The potential gradient on the conductor surface depends not only on the voltage level but also directly on the equivalent surface area of ​​the conductor. (2) Spark discharge: This is caused by the destruction of local insulation, contamination of insulators, poor contact of fittings, etc. on the line. Its spectrum range may be as high as hundreds of megahertz, and its amplitude variation range is very large, possibly much greater than that of corona discharge. (3) Power frequency electric field: Its main form exists between the conductor and the ground. Its intensity mainly depends on the voltage level. For DC transmission lines, it is a pure electrostatic field. (4) Power frequency magnetic field: Because the power frequency is very low and the wavelength is very long (the wavelength of 50Hz is 6000km), it is still a near field even though it is far from the line. The magnetic field and electric field must be considered separately. Its intensity mainly depends on the current carrying capacity of the conductor. However, its attenuation with distance is very fast. (5) Passive interference: Transmission lines and their towers, even when not energized, will affect the propagation of electromagnetic waves (e.g., radar signals, shortwave communications, etc.), which is called passive interference. (6) Ground current: For the neutral line of an unbalanced three-phase AC system or the case where the ground is the loop of a DC transmission line, the ground current is sometimes quite considerable. If not handled properly, it will cause a rise in ground potential or corrosion of underground pipelines. The above-mentioned sources of interference may cause interference to different sensitive equipment. The effects of different sources of interference are different. It is worth noting that if not handled properly, the intensity of these interferences will increase with the voltage level of the line. And increasing the voltage is an inevitable trend of the transmission system. Therefore, corresponding high requirements are put forward for electromagnetic compatibility. 4. Electromagnetic pollution protection measures and electromagnetic compatibility standards 4.1 Electromagnetic pollution protection The primary measure to suppress electromagnetic pollution is to find the pollution source; the second is to determine the path of pollution intrusion. There are two main modes: conduction and radiation. The focus of the work is to determine the amount of interference. Solving electromagnetic compatibility (EMC) problems should begin in the product development stage and continue throughout the entire product or system development and production process. Extensive experience both domestically and internationally shows that the earlier EMC issues are addressed during the research and development of a product or system, the more human and material resources can be saved. A key technology in EMC design is the study of electromagnetic interference sources; controlling electromagnetic emissions at the source is the fundamental solution. Controlling interference source emissions involves not only addressing the mechanism of EMC generation to reduce the level of electromagnetic noise, but also the widespread application of shielding (including isolation), filtering, and grounding technologies. Shielding primarily uses various conductive materials to create various shells connected to the ground to cut off the propagation path of electromagnetic noise formed by electrostatic coupling, inductive coupling, or alternating electromagnetic field coupling through space. Isolation mainly uses devices such as relays, isolation transformers, or opto-isolators to cut off the propagation path of electromagnetic noise in conductive form. Its characteristic is that it separates the ground systems of two circuit parts, cutting off the possibility of coupling through impedance. Filtering is a technique for processing electromagnetic noise in the frequency domain, providing a low-impedance path for electromagnetic noise to suppress electromagnetic interference. For example, a power supply filter presents high impedance to a 50Hz power supply frequency, but low impedance to the electromagnetic noise spectrum. Grounding includes grounding, signal grounding, etc. The design of the grounding body, the arrangement of the grounding wire, and the impedance of the grounding wire at various frequencies not only involve the electrical safety of the product or system, but also relate to electromagnetic compatibility and its measurement technology. Specific technical solutions can be summarized into the following categories: (1) Transmission channel suppression: Specific methods include filtering, shielding, bonding, grounding, and wiring. (2) Spatial separation: Location control, natural terrain isolation, azimuth control, and electric field vector direction control. (3) Time separation: Time sharing criteria, radar pulse synchronization, active time separation, and passive time separation. (4) Frequency management: Frequency control, filtering, frequency modulation, digital transmission, and photoelectric conversion. (5) Electrical isolation: Transformer isolation, photoelectric isolation, relay isolation, and DC/DC conversion. 4.2 Electromagnetic compatibility standards When an electrical or electronic device does not interfere with the normal operation of other devices due to the electromagnetic force generated by the power during operation, these devices are said to have electromagnetic compatibility. In summary: (1) It does not interfere with other systems. (2) It is not sensitive to the emissions of other systems. (3) It does not interfere with the system itself. 5. Conclusion The rapid development of electromagnetic compatibility (EMC) technology has also stimulated the demand for EMC standardization. Some developed countries are in a leading position in EMC technology research, standard setting, EMC testing and certification. In particular, since the promulgation of the European Community's legal directive on EMC (Directive 89/336/EEC), governments have begun to consider EMC issues from a commercial perspective and have taken corresponding measures to strengthen the formulation and implementation of EMC standards and regulations. Although China started its EMC work relatively late, relevant departments are stepping up their efforts to keep up with the pace of international EMC work. Because electromagnetic interference is ubiquitous and ever-present, it determines the practical necessity of EMC. Electromagnetic interference and its suppression are becoming increasingly prominent issues. In this century, EMC science will further absorb the theoretical essence of various professions and disciplines, give full play to its marginal and interdisciplinary characteristics to form a highly comprehensive and complete major discipline. At the same time, it will develop rapidly in EMC prediction, coordination, monitoring and application.