Technical column



Construction of EMC laboratory for power systems

       Electromagnetic Compatibility (EMC) means the ability of electrical and electronic equipment to function properly in their electromagnetic environment without causing unacceptable electromagnetic interference to anything else in that environment. With the development of electrical and electronic technology, electromagnetic compatibility has become a common concern in all countries in the world.

       The electrical and electronic equipment in the power system is concentrated, the electromagnetic environment is complex, and various electromagnetic interferences will occur or occur under normal and abnormal operating conditions, such as the transient process of switching operations and short-circuit faults; near high-voltage, high-current wires or equipment Electric and magnetic fields; radio frequency electromagnetic radiation; lightning; electrostatic discharge; voltage fluctuations, voltage dips and interruptions of the power supply network; harmonics; working signals and noises of electronic equipment, etc.

       Automation equipment operating in power systems is sensitive to electromagnetic interference. Secondary weak current equipment based on microelectronic technology and computer technology, such as relay protection, automatic control, telecontrol and communication devices, etc. are widely used in power systems. They have high sensitivity and are close to strong current equipment, so they are easy to disturbed. In my country's power system, interference events caused by switch operation, lightning, radiated electromagnetic field, power frequency magnetic field and other reasons frequently occur, resulting in malfunction of protection, malfunction of automation equipment, and even damage to components or equipment.

       With the development of the power system, the capacity of the power grid increases, the voltage level increases, the structure of the power grid becomes more complex, and the degree of automation and the sensitivity and reliability of the relay protection and automation system are required to be higher; on the other hand, due to the high-voltage electrical equipment manufacturing With the advancement of technology, information technology and computer technology, the structure and layout of traditional primary and secondary equipment are changing, and their development tends to be small and compact, integrated and intelligent. Such as distributed substation comprehensive automation equipment integrating relay protection, monitoring and communication functions; high-voltage intelligent switch integrating electronic control, monitoring and even protection; SF6 closed switchgear (GIS); high-voltage circuit breaker, isolating switch Compact combined outdoor switchgear, which is organically combined with individual components such as grounding switches, current and voltage transformers, etc., are all under development. Secondary equipment such as control and protection will be moved from the original control room with good environmental conditions to an open field or a place very close to the primary equipment, or even a combination of strong and weak current equipment, the electromagnetic environment will deteriorate, and electromagnetic compatibility The problem is more prominent.

       If the power system does not properly solve the electromagnetic compatibility problem, it will not only threaten safe and reliable production, but also be conducive to the adoption of new technologies and affect the development of the power system. Electromagnetic compatibility testing is the key to research and solve electromagnetic compatibility problems. In recent years, various domestic industries have successively built electromagnetic compatibility laboratories for different products, such as communications, automobiles, and home appliances. There are also various types of laboratories in foreign countries, but there is no EMC laboratory for power system automation equipment. In view of the urgent need for EMC in the power industry, an EMC laboratory for power system automation equipment is ready to be built. The completion of the laboratory provides the necessary conditions for the detection and research of electromagnetic compatibility of automation equipment in the power industry.


1. Design of electromagnetic compatibility laboratory for automation equipment

       Corresponding to the meaning of electromagnetic compatibility, electromagnetic compatibility testing includes two aspects: immunity (or electromagnetic susceptibility, EMS) test and electromagnetic disturbance (or electromagnetic emission, EMI) test. The immunity test is to simulate various types of interference that may occur during operation, and to check whether the equipment under test can withstand the specified electromagnetic interference level under the condition that the equipment under test is as close as possible to the actual operation. By adjusting the output of the interference level, the electromagnetic environment with different interference levels can be simulated. The electromagnetic disturbance (emission) test is to measure the electromagnetic disturbance level emitted by the equipment under test through external wires (power supply, signal/control, communication, grounding, etc. ports) or space (housing port) under actual operating conditions. Do not exceed the specified limits to avoid interference with other equipment or system operation. When conducting the above two tests, the actual effects of various anti-interference and emission suppression technical measures can be checked and compared.

        Since the laboratory is built for power system automation equipment, its product features are mainly considered during design, including:

(1) Various types of interference sources simulated are interference phenomena that often occur on site, such as primary switch operation transient state, secondary circuit operation transient state, lightning, electrostatic discharge, power frequency magnetic field, electromagnetic emission of handheld communication equipment, etc.

(2) Since the equipment is to be tested under simulated normal operating conditions, various input and output auxiliary quantities need to be applied, including voltage, current, switching value, analog value, etc. This point was fully considered during the construction of the laboratory. In addition to being equipped with corresponding instruments (such as relay protection testers, etc.), multiple connection channels of various types are also reserved (especially in the design of darkrooms), so that It is very convenient to provide enough auxiliary amount for the equipment under test, and it can also monitor whether its various functions are normal during the test in real time.

(3) The appearance and weight of the power system automation equipment are fully considered in the design of the laboratory, and a comprehensive design has been carried out in terms of load-bearing, space, and door size and form.

        The design of the laboratory is not only suitable for power system automation equipment products, but also suitable for other types of products, providing sufficient margin in terms of product size, weight and external auxiliary quantity. At the same time, in terms of test categories, the laboratory also takes into account the standard requirements of other types of products, and can conduct various tests according to general standards such as GB, IEC, CISPR, and EN.

       The test area is mainly composed of an anechoic room, shielded room, general test room and control room.

(1) The anechoic chamber is a standard 3 m anechoic chamber, which mainly provides a stable test site for studying the propagation and attenuation of electromagnetic waves. Radiation emission test and radiation sensitivity test can be carried out in accordance with IEC, GB, EN and CISPR standards

(2) The shielding room is a 6-sided fully shielded space, which plays the role of isolating the internal and external electromagnetic fields and provides a pure electromagnetic environment, which is convenient for various electromagnetic field analysis and research on the equipment without being affected by the outside world. At the same time, it can carry out radio frequency conducted immunity test and radio frequency conducted emission test according to IEC, GB, EN and CISPR standards.

(3) The general laboratory is a place for immunity tests, which can simulate various types of interference tests according to IEC, GB, EN and other standards, including: damped oscillatory wave immunity test, fast transient immunity test , surge immunity test, electrostatic discharge immunity test, power frequency magnetic field immunity test, pulse magnetic field immunity test, harmonic immunity test, voltage sag, short interruption and change immunity test, harmonic current emission limit value testing etc.

2. Anechoic chamber

        The anechoic chamber is the most important and most expensive test facility in the electromagnetic compatibility laboratory. The laboratory generally uses the standard 3m method anechoic chamber, mainly based on the following considerations:

(1) Both the 3m method and the 10m method are test schemes recommended by international standards, and the 10m method is very expensive, about 1 million US dollars higher than the 3m method. From the perspective of performance and price, the 3m method is more appropriate.

(2) The 3m anechoic chamber is the most constructed at home and abroad, and it is very mature in technology and can achieve high performance indicators.

(3) For automation equipment to operate reliably in the complex electromagnetic environment of the power system, its immunity index (that is, the degree to which the equipment can withstand external interference) is particularly important. The 3m method anechoic chamber is a standard test site for radiation immunity tests .

        The outer layer of the anechoic chamber adopts a double-layer 2mm galvanized steel plate as a shielding layer to block the mutual influence of the internal and external electromagnetic fields. Composite wave-absorbing material is used inside, that is, a wedge-shaped wave-absorbing material is added to the ferrite, so that the effective space and bandwidth of the darkroom can be greatly improved, and the frequency of the darkroom can reach 18GHz. The darkroom is equipped with an automatic turntable with a diameter of 2m and a load-bearing capacity of 2t, an automatic lifting tower of 1-4m antenna, a TV monitoring system, a smoke alarm system, etc., and a translational pneumatic non-threshold automatic door is used to ensure the long-term stability of the shielding performance of the door and the barrier-free access of the tested equipment. Enter the darkroom. At the same time, the darkroom is also equipped with various types of control cables and optical cables, which can provide various auxiliary quantities for various equipment tests, so as to better simulate the normal operation status of the equipment.

After the anechoic chamber is built, the shielding performance, field uniformity and normalized site attenuation tests are carried out by a third-party authoritative testing organization, and the results must meet its various performance indicators.

3. The main instruments and equipment of the laboratory

        In addition to the anechoic room, shielding room and control room, the laboratory is also equipped with the most advanced electromagnetic compatibility testing instruments at home and abroad, which can test the anti-interference ability of the equipment and the external emission of the equipment itself according to the highest level requirements stipulated by the relevant domestic and foreign electromagnetic compatibility standards. degree of electromagnetic interference. These facilities include:

(1) A full set of radiated immunity test system and radiated emission test system.

(2) Various conduction immunity test instruments.

(3) The electromagnetic field scanner is an electromagnetic interference near-field scanning device aimed at the product design and development stage. It can easily detect the position and intensity of radiation sources in circuit boards or small devices, and visualize them with two-dimensional or three-dimensional color graphics. display. Potential problems can be discovered in time to avoid various losses caused by modification after product design is completed.

4. Laboratory work

       During the construction of the laboratory, the electromagnetic compatibility test should be carried out step by step, and multiple sets/sets of various project tests should be carried out for automation devices such as power system relay protection, telecontrol monitoring and other types of equipment, and multiple copies should also be given. Test reports, which include new product development or product finalization tests. During the test, not only problems were found, but also problems were solved in a timely manner. These tasks can greatly enrich the experience of EMC testing for technicians. The laboratory has a strong technical force, and electromagnetic compatibility professionals who are familiar with power system automation equipment can not only accurately assess the performance of the equipment, but also provide help for improving the electromagnetic compatibility performance of the equipment.

       The laboratory construction is based on the power system, but also takes into account the product needs of other fields, and can provide the same services for information technology equipment, household appliances, power tools and other products.

       The laboratory can also hold various lectures and conferences to popularize EMC knowledge and obtain good social benefits from it. The laboratory is managed and operated in accordance with the nationally recognized laboratory standards and combined with EMC characteristics, and all instruments and equipment should pass the measurement of the measurement unit.

       The laboratory can provide good services for the power system and the whole society in the following aspects:

(1) Measure various electromagnetic interference sources and phenomena in power systems and other systems and study their characteristics in time domain, frequency domain and propagation mode;

(2) Evaluate the electromagnetic environment of the power system and its impact;

(3) Carry out the evaluation of electromagnetic compatibility between the primary and secondary equipment of the power system;

(4) Carry out various electromagnetic compatibility testing tests;

(5) Study the electromagnetic compatibility detection method for equipment;

(6) Anti-interference measures for research equipment;

(7) Study measures to control electromagnetic emissions of equipment;

(8) Conduct pre-tests at each stage of equipment development, so that the electromagnetic compatibility of equipment can be controlled at the initial stage of development;

(9) Carry out experimental research on the characteristics of electromagnetic compatibility protection components;

(10) Provide training for EMC technicians.


Electromagnetic Compatibility ( EMC ) testing requirements and solutions for relay protection and automation products :

       The electromagnetic compatibility requirements of relay protection and automation products are basically divided into two parts: electromagnetic susceptibility (EMS for short) and electromagnetic interference (EMI for short)

Among them, EMI includes:

1) Harmonic current emission limits (IEC 61000-3-2/ GB 17625.1)

2) Voltage fluctuation and flicker (IEC 61000-3-3/ GB 17625.2)

3) Limits of radio frequency conducted emissions (IEC 60255-25/ GB/T 14598.16)

4) Radiated emission limits (IEC 60255-25/ GB/T 14598.16)

EMS includes:

1) 1MHz burst immunity test (IEC 60255-22-1/ GB/T 14598.13)

2) Electrostatic discharge (ESD) immunity (IEC 60255-22-2/ GB/T 14598.14)

3) Radio frequency electromagnetic radiation immunity (IEC 60255-22-3/ GB/T 14598.9)

4) Electrical fast transient/burst immunity test (IEC 60255-22-4/ GB/T 14598.10)

5) Surge (shock) immunity (IEC 60255-22-5/ GB/T 14598.18)

6) Conducted disturbance immunity induced by radio frequency field (IEC 60255-22-6/ GB/T 14598.17)

7) Power frequency immunity (IEC 60255-22-7/ GB/T 14598.19)

8) Auxiliary power supply port voltage dips, short interruptions, voltage variations and ripples (IEC 60255-11/ GB/T 14598.11)

9) Power frequency magnetic field immunity (IEC 61000-4-8/ GB/T 17626.8)

10) Pulse magnetic field immunity (IEC 61000-4-9/ GB/T 17626.9)

11) Harmonic and interharmonic immunity (IEC 61000-4-13/ GB/T 17626.13)


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