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The influence of electric power system on the electromagnetic compatibility of automation equipment


2021-02-04

1. Overview

The secondary automation equipment of the power system is a part of the operating equipment of the power system. When discussing its electromagnetic compatibility, it should not be treated as an electronic device in isolation, but should be considered comprehensively and comprehensively in conjunction with the electromagnetic environment of the power system. . The ultimate goal of studying the electromagnetic compatibility of secondary automation equipment is to improve the ability of secondary automation equipment to resist various interferences, and at the same time reduce the degree of interference of the equipment to other surrounding equipment, so as to improve the reliability of system operation. However, the improvement of the equipment's anti-interference performance is not unlimited, and it is unrealistic both technically and economically. From the perspective of the large electromagnetic environment of the power system, only on the basis of in-depth research on the interference source and the interference coupling path, and a reasonable evaluation of the electromagnetic environment in which the secondary automation equipment is located, can its anti-interference performance be proposed. Reasonable requirements, and on this basis, research and improve its anti-interference ability and the degree of suppression of interference.

The electromagnetic compatibility problem has been strongly reflected in the power system: on the one hand, the power system is a powerful source of interference, which will produce various steady-state or transient interferences during its normal operation or failure, such as magnetic near high-current equipment. Try the transient disturbance during switch operation. On the other hand, with the widespread adoption of microelectronics technology, various secondary automation equipment with high sensitivity to interference plays an important role in the operation of the power system. They are greatly improving the degree of automation of the power system. At the same time, it will inevitably suffer from some interference from the inside of the power system or other influences, which may cause its work to malfunction, which becomes a hidden danger that affects the safe and reliable operation of the power system.

2. Description of electromagnetic compatibility of power system

  If the secondary device is discussed as a receiver of interference, the electromagnetic compatibility problem of the power system can be described as follows.

  The main interference sources that affect the secondary equipment through the conduction effect of various connecting lines or through the radiation effect of space are:

  a) Some natural disturbances such as lightning strikes, static electricity, etc.

  b) Transient interference during operation or system failure, such as: disconnector and circuit breaker operation, low-voltage loop relay action, common mode interference caused by short-circuit current during ground fault, etc.

  C) Steady-state interference during system operation: such as interference from power frequency electric fields near high-voltage facilities and electronic or communication equipment near magnetic sensors.

Among them, the most influential interference on the secondary equipment is the transient interference generated when the primary switch (isolating switch and circuit breaker) operates. On the one hand, this transient interference radiates outward in the form of a field, and passes through the secondary equipment. Coupling of external conductors (various loop connections, ground wires) or direct space radiation coupling into the interior of the secondary equipment, on the other hand, directly connected to the conductors (PT, CT, high-frequency carrier) of high-voltage facilities through the secondary equipment Channel, etc.) conduction into the secondary equipment, affecting the normal operation of the secondary equipment.

The way to solve the electromagnetic compatibility problem of the power system lies in: a) measuring and evaluating the electromagnetic environment of the system; b) taking necessary and reasonable measures in the system design and construction to slow down the effect of interference on the secondary equipment; c) improving the secondary equipment Its own anti-interference ability.

In fact, researchers at home and abroad have accumulated a large amount of data through years of hard work, and have formulated relevant standards and guidelines based on them to guide the design of power systems and the design of secondary equipment. However, with the recent development of power technology With the development of 2010, some new technologies have been widely used. The changes in the electromagnetic environment of the power system and the impact on the secondary equipment caused by this are worthy of further attention and research.  

3. Integrated automation technology and decentralized protection of substations

After years of development, the integrated automation technology of substations has reached a considerable level. From the initial centralized structure to the widely used decentralized structure, not only the degree of automation of the substation can be greatly improved, but also the construction cost of the system is directly reduced. However, the development of technology has also brought about changes in the operating environment of power automation equipment.

The early centralized structure only added the computer management function on the basis of the original secondary equipment configuration. The substation is equipped with the corresponding microcomputer protection device and microcomputer remote control device according to the scale, and is installed in the main control room. The control and signal volume of the system Upload via cable in the form of analog quantity. The main disadvantage of this structure is that resources cannot be shared and a large amount of cables cannot be saved. At the same time, because the control signal is transmitted in the form of analog quantity over long distances, the data is susceptible to interference from the scene. However, the secondary automation equipment is relatively in a control room with a better electromagnetic environment, and the electromagnetic disturbance encountered will be weaker. The distributed structure uses the control unit, the protection unit, and the data acquisition unit to be installed nearby the outdoor high-voltage switch or the indoor switch cabinet, and the signal is uploaded through the digital signal line or optical cable, which greatly reduces the design of the traditional substation. The connection length of the various analog control signals improves the anti-interference ability of the system signal transmission. However, for the secondary automation equipment, because it is lowered from the original control room with better conditions to the vicinity of the switchyard, it operates in an electromagnetic environment. Deteriorating, its anti-jamming performance also puts forward higher requirements. At the same time, due to the improvement of the functional integration of the secondary automation equipment itself, the probability of mutual coupling of the internal interference of a single device is increased, which makes the anti-interference design of the equipment face higher difficulties.

The immunity requirements for distributed equipment should be based on the electromagnetic interference data in the switching field. The data measured in the control room may no longer be applicable. The induced voltage of the control cable at the end of the switching field may be higher than that in the control field. The end of the room should be high.

In recent years, more and more high-voltage substation protections in our country have been transferred to the switchyard. The research work on the various effects of the powerful interference generated by the high-voltage switch operation on the protection equipment is also being actively carried out. In a series of test data Most of them are for the transient electric field and magnetic interference voltage and current on the secondary side of the PT/CT generated during a switching operation, the induced voltage on the parallel cable under the bus bar, and the AC 220V power supply of the substation. The test parameters involve waveforms, leading Frequency, intensity, etc. Judging from the actual test results during the primary switching operation of several 500kV substations under protection in our country, the interference voltage intensity on the secondary side is generally less than the highest level specified in the standard, and the frequency is higher than the requirements in the standard. The interference voltage on the 220V power supply should be larger. However, for secondary automation equipment, the most important thing is the interference situation at the secondary equipment port, and there is little accumulation of data on this aspect.

In addition, the impact of switching field transient electromagnetic field on automation equipment through spatial coupling is also a subject that needs to be studied in depth. For this type of device that needs to be placed in the switching field, as the design of the protection chamber gradually tends to use an unshielded design, the device itself The shielding design is even more important, and this aspect happens to be the weak link in the design and manufacture of our power automation equipment.  

  In the past few decades, the primary equipment of the power system as a source of interference has changed very little, and the secondary weak current equipment as a sensitive equipment has undergone huge changes in both design and layout. With the increasing degree of automation of power systems, the role of secondary automation equipment is becoming increasingly important. The reliability of secondary automation equipment is directly related to whether the power system can operate reliably, so the electromagnetic compatibility performance of secondary automation equipment has become more and more concerned. How to evaluate the electromagnetic compatibility performance of secondary automation equipment, the most important thing is to evaluate the electromagnetic environment in which it is located. With the changes in the environment of secondary automation equipment and the improvement of electromagnetic environment measuring instruments and technologies, the standards for evaluating its electromagnetic compatibility performance are constantly being improved. There is only one purpose of all these tasks, which is to ensure secondary automation equipment. Correct reliability at runtime.

1. Overview

The secondary automation equipment of the power system is a part of the operating equipment of the power system. When discussing its electromagnetic compatibility, it should not be treated as an electronic device in isolation, but should be considered comprehensively and comprehensively in conjunction with the electromagnetic environment of the power system. . The ultimate goal of studying the electromagnetic compatibility of secondary automation equipment is to improve the ability of secondary automation equipment to resist various interferences, and at the same time reduce the degree of interference of the equipment to other surrounding equipment, so as to improve the reliability of system operation. However, the improvement of the equipment's anti-interference performance is not unlimited, and it is unrealistic both technically and economically. From the perspective of the large electromagnetic environment of the power system, only on the basis of in-depth research on the interference source and the interference coupling path, and a reasonable evaluation of the electromagnetic environment in which the secondary automation equipment is located, can its anti-interference performance be proposed. Reasonable requirements, and on this basis, research and improve its anti-interference ability and the degree of suppression of interference.

The electromagnetic compatibility problem has been strongly reflected in the power system: on the one hand, the power system is a powerful source of interference, which will produce various steady-state or transient interferences during its normal operation or failure, such as magnetic near high-current equipment. Try the transient disturbance during switch operation. On the other hand, with the widespread adoption of microelectronics technology, various secondary automation equipment with high sensitivity to interference plays an important role in the operation of the power system. They are greatly improving the degree of automation of the power system. At the same time, it will inevitably suffer from some interference from the inside of the power system or other influences, which may cause its work to malfunction, which becomes a hidden danger that affects the safe and reliable operation of the power system.

2. Description of electromagnetic compatibility of power system

  If the secondary device is discussed as a receiver of interference, the electromagnetic compatibility problem of the power system can be described as follows.

  The main interference sources that affect the secondary equipment through the conduction effect of various connecting lines or through the radiation effect of space are:

  a) Some natural disturbances such as lightning strikes, static electricity, etc.

  b) Transient interference during operation or system failure, such as: disconnector and circuit breaker operation, low-voltage loop relay action, common mode interference caused by short-circuit current during ground fault, etc.

  C) Steady-state interference during system operation: such as interference from power frequency electric fields near high-voltage facilities and electronic or communication equipment near magnetic sensors.

Among them, the most influential interference on the secondary equipment is the transient interference generated when the primary switch (isolating switch and circuit breaker) operates. On the one hand, this transient interference radiates outward in the form of a field, and passes through the secondary equipment. Coupling of external conductors (various loop connections, ground wires) or direct space radiation coupling into the interior of the secondary equipment, on the other hand, directly connected to the conductors (PT, CT, high-frequency carrier) of high-voltage facilities through the secondary equipment Channel, etc.) conduction into the secondary equipment, affecting the normal operation of the secondary equipment.

The way to solve the electromagnetic compatibility problem of the power system lies in: a) measuring and evaluating the electromagnetic environment of the system; b) taking necessary and reasonable measures in the system design and construction to slow down the effect of interference on the secondary equipment; c) improving the secondary equipment Its own anti-interference ability.

In fact, researchers at home and abroad have accumulated a large amount of data through years of hard work, and have formulated relevant standards and guidelines based on them to guide the design of power systems and the design of secondary equipment. However, with the recent development of power technology With the development of 2010, some new technologies have been widely used. The changes in the electromagnetic environment of the power system and the impact on the secondary equipment caused by this are worthy of further attention and research.  

3. Integrated automation technology and decentralized protection of substations

After years of development, the integrated automation technology of substations has reached a considerable level. From the initial centralized structure to the widely used decentralized structure, not only the degree of automation of the substation can be greatly improved, but also the construction cost of the system is directly reduced. However, the development of technology has also brought about changes in the operating environment of power automation equipment.

The early centralized structure only added the computer management function on the basis of the original secondary equipment configuration. The substation is equipped with the corresponding microcomputer protection device and microcomputer remote control device according to the scale, and is installed in the main control room. The control and signal volume of the system Upload via cable in the form of analog quantity. The main disadvantage of this structure is that resources cannot be shared and a large amount of cables cannot be saved. At the same time, because the control signal is transmitted in the form of analog quantity over long distances, the data is susceptible to interference from the scene. However, the secondary automation equipment is relatively in a control room with a better electromagnetic environment, and the electromagnetic disturbance encountered will be weaker. The distributed structure uses the control unit, the protection unit, and the data acquisition unit to be installed nearby the outdoor high-voltage switch or the indoor switch cabinet, and the signal is uploaded through the digital signal line or optical cable, which greatly reduces the design of the traditional substation. The connection length of the various analog control signals improves the anti-interference ability of the system signal transmission. However, for the secondary automation equipment, because it is lowered from the original control room with better conditions to the vicinity of the switchyard, it operates in an electromagnetic environment. Deteriorating, its anti-jamming performance also puts forward higher requirements. At the same time, due to the improvement of the functional integration of the secondary automation equipment itself, the probability of mutual coupling of the internal interference of a single device is increased, which makes the anti-interference design of the equipment face higher difficulties.

The immunity requirements for distributed equipment should be based on the electromagnetic interference data in the switching field. The data measured in the control room may no longer be applicable. The induced voltage of the control cable at the end of the switching field may be higher than that in the control field. The end of the room should be high.

In recent years, more and more high-voltage substation protections in our country have been transferred to the switchyard. The research work on the various effects of the powerful interference generated by the high-voltage switch operation on the protection equipment is also being actively carried out. In a series of test data Most of them are for the transient electric field and magnetic interference voltage and current on the secondary side of the PT/CT generated during a switching operation, the induced voltage on the parallel cable under the bus bar, and the AC 220V power supply of the substation. The test parameters involve waveforms, leading Frequency, intensity, etc. Judging from the actual test results during the primary switching operation of several 500kV substations under protection in our country, the interference voltage intensity on the secondary side is generally less than the highest level specified in the standard, and the frequency is higher than the requirements in the standard. The interference voltage on the 220V power supply should be larger. However, for secondary automation equipment, the most important thing is the interference situation at the secondary equipment port, and there is little accumulation of data on this aspect.

In addition, the impact of switching field transient electromagnetic field on automation equipment through spatial coupling is also a subject that needs to be studied in depth. For this type of device that needs to be placed in the switching field, as the design of the protection chamber gradually tends to use an unshielded design, the device itself The shielding design is even more important, and this aspect happens to be the weak link in the design and manufacture of our power automation equipment.  

  In the past few decades, the primary equipment of the power system as a source of interference has changed very little, and the secondary weak current equipment as a sensitive equipment has undergone huge changes in both design and layout. With the increasing degree of automation of power systems, the role of secondary automation equipment is becoming increasingly important. The reliability of secondary automation equipment is directly related to whether the power system can operate reliably, so the electromagnetic compatibility performance of secondary automation equipment has become more and more concerned. How to evaluate the electromagnetic compatibility performance of secondary automation equipment, the most important thing is to evaluate the electromagnetic environment in which it is located. With the changes in the environment of secondary automation equipment and the improvement of electromagnetic environment measuring instruments and technologies, the standards for evaluating its electromagnetic compatibility performance are constantly being improved. There is only one purpose of all these tasks, which is to ensure secondary automation equipment. Correct reliability at runtime.