(1) microcomputer protection, measurement and control devices
① hardware to take grounding, shielding, arc suppression (such as diodes across the coil), optoelectronic isolation, digital filtering, decoupling, software traps, self-checking and other measures to suppress or eliminate interference.
② device shell using conductive box, improve the grounding performance and anti-magnetic capability.
③ To the aging of components screening strict control to ensure the stability of its performance. Try to cut off a variety of electromagnetic coupling pathway. Pay attention to ensure that the photoelectric coupling device voltage level.
④ DC 220V power supply as far as possible. The use of non-stop power supply is appropriate to use on-line UPS or non-stop inverter power supply. If the use of AC power supply should be added low-pass filter and 1:1 isolation transformer to suppress and eliminate high-frequency interference signals.
⑤ For the protection and external circuit directly connected to the part, should be isolated through the optocoupler circuit.
⑥ If necessary, add a time delay module in the software to eliminate pseudo-remote signaling. For example, for the signal relay instantaneous contact action contact time 1: generally greater than 20ms, false telecommunication signal period T2: generally less than 12ms, choose a suitable telecommunication acquisition software delay time can be shielded from the corresponding telecommunication interference signal.
⑦ For more serious interference with the remote signal, try to change the "normally open" contact to a "normally closed" contact when conditions permit, and reduce the interference of external electromagnetic fields by applying a voltage at the input of the optocoupler.
⑧ Recommended fiber optic communication.
(2) design and operation management
① secondary circuit should be selected shielded cable, the spare core of the control cable grounding, enhance the shielding effect. The alignment of the input and output circuits should be separated from the strong and weak.
② For interference from the power supply circuit, power filters can be used to eliminate the two forms of electromagnetic interference conduction and magnetic field.
③ For the interference of the analog input circuit, the use of electrostatic shielding method to eliminate interference. Through the shielding body and the earth good contact,
the analog brought about by the strong electrical interference signal into the earth. Anti-accident measures require the secondary winding of the voltage transformer (star), three windings (open triangle) of the N phase must be separated, a point of grounding on the protection cabinet. The secondary circuit of the current transformer should have a grounding point.
④ For contact jitter interference, if necessary, can take the double contact acquisition, through logical judgment to eliminate false alarm signals.
⑤ The terminal rows of the strong and weak circuits should be arranged separately or separated by additional empty terminals.
⑥ Ensure that the grounding network is good, reduce the fault current caused by the ground potential rise.
⑦ shielding on the protective device must be well grounded
⑧ unused AC terminals should be shorted.
3 Recommendations
(1) substation has a complex electromagnetic environment, so the selection of equipment should be noted that according to the automation equipment manufacturer's guaranteed value, a reasonable determination of the automation equipment installation location or according to the application of automation equipment, the appropriate requirements for the level of anti-interference equipment. Immunity test is an important method to test the anti-interference ability of the equipment, IEC 61000-2-5 according to the equipment installation environment is divided into five test levels for selection, and the substation environment related to the level shown in Table 1.
The ratings in Table 1 are based on the degree of influence caused by the operation of the disconnecting switch, which is recommended. Compared with the disconnecting switch operation, the amplitude of the transient electromagnetic field caused by the circuit breaker operation is small, the dominant frequency is high, and the total number of pulses is small, so the test level can be adjusted downward appropriately. At present, the relevant national standards for fast transient interference test level requirements for "power plants, substations and factories in normal use of the measurement relays and protection devices should be prioritized to use Class III", but for special types of circuit breakers and load circuits with large inductance occasions the lack of specific guidance, therefore, should be strengthened in this area of research to guide the design selection and design of the circuit breaker. Therefore, the research in this aspect should be strengthened to guide the design selection and equipment manufacturing work. According to the practical experience of field operation, it is recommended that the automation equipments centrally arranged in the control room should reach the level of anti-rapid transient interference III. Decentralized layout in the switchgear or near the circuit breaker, and the circuit breaker breaking characteristics are prone to cause rapid transient process conditions of automation equipment required to achieve the level of anti-rapid transient interference IV.
(2) Strengthen the electromagnetic interference analysis and calculation technology and simulation technology research. The use of EMTP electromagnetic transient simulation and calculation software, CDEGS software package can analyze the transient response analysis caused by the circuit breaker breakers, but due to the generality of the above software package, coupled with more types of circuit breakers, so in the specific analysis of the transient interference problem is not able to meet the requirements of the design and development and testing, to be automated by the power workers **** the same efforts.
The place to change the voltage. In order to power plants to send out the power transmission to distant places, the voltage must be raised, into high-voltage electricity, to the user neighborhood and then reduce the voltage as needed. The work of this voltage rise and fall by the substation to complete. The main equipment of the substation is the switch and transformer. According to the size of the different, known as substation, distribution room, etc..
Substation substation (Substation) is the assembly of some equipment to cut off or connect, change or adjust the voltage, in the power system, substation is the transmission and distribution of power assembly point, substation is mainly divided into: step-up substation, the main network substation, secondary substation, distribution station.
The substation is a power facility that transforms voltage, accepts and distributes power, controls the flow of power and adjusts the voltage in the power system, and it links the power grids of all voltage levels through its transformers.
The transformer is the transformer of the substation voltage conversion equipment, in addition to the substation equipment, switchgear to open and close circuits, convergence of the current bus, measurement and control of the transformer, instrumentation, relay protection devices and lightning protection devices, scheduling communication devices, etc., and some substations have reactive power compensation equipment. The main equipment and connection of the substation, according to its different functions and differences.
Transformer is the main equipment of the substation, divided into double-winding transformer, three-winding transformer and autotransformer that is, high and low voltage each phase **** with a winding, from the high-voltage winding in the middle of a head as a low-pressure winding out of the transformer. Voltage and winding turns is proportional to the number of turns, the current is inversely proportional to the number of turns.
Transformer can be divided into step-up transformer and step-down transformer according to its role. The former is used for power system transmission substation, the latter is used for the receiving end of the substation. The voltage of the transformer needs to be compatible with the voltage of the power system. In order to maintain a qualified voltage in different load conditions sometimes need to switch the transformer taps.
By tap switching transformer with load on-load voltage regulator transformer and no load voltage regulator transformer. Load regulator transformer is mainly used in the receiving end substation.
Voltage transformer and current transformer. Their principle of operation and transformers are similar, they will be high voltage equipment and bus operating voltage, high current that equipment and bus load or short circuit current in accordance with the prescribed ratio into the measurement instrumentation, relay protection and control equipment, low voltage and small current. In the rated operating conditions of the voltage transformer secondary voltage of l00V, current transformer secondary current of 5A or 1A. current transformer secondary winding is often connected to the load near short circuit, please note: never let it open circuit, otherwise it will be due to the high voltage and jeopardize the safety of the equipment and people, or make the current transformer burned.
Switchgear. It includes circuit breakers, disconnect switches, load switches, high voltage fuses, etc. are the equipment to break and close the circuit. Circuit breaker in the normal operation of the power system is used to close and disconnect the circuit fault in the relay protection device under the control of the faulty equipment and lines automatically disconnected, but also can have automatic reclosing function. In China, more than 220kV substations use more air circuit breakers and sulfur hexafluoride circuit breakers.
The main function of the disconnecting switch (knife gate) is to isolate the voltage when the equipment or line maintenance to ensure safety. It can not disconnect the load current and short-circuit current, and should be used in conjunction with circuit breakers. In the blackout should first pull the circuit breaker after pulling the isolation switch, power supply should first close the isolation switch after closing the circuit breaker. If misoperation will cause equipment damage and personal injury.
Load switch can disconnect the load current in normal operation without the ability to disconnect the fault current, generally used in conjunction with high-voltage fuse for 10kV and above voltage and infrequent operation of the transformer or outgoing line.
In order to reduce the footprint of the substation in recent years, the active development of sulfur hexafluoride closed combination of appliances (GIS). It is the circuit breaker, disconnecting switch, bus, grounding switch, transformer, outlet casing or cable terminal head, etc. were installed in their respective seals in the centralized composition of a whole shell filled with sulfur hexafluoride gas as an insulating medium. This combination of appliances has a compact structure, small size and light weight is not affected by atmospheric conditions, long service intervals, no electrocution and electrical noise interference and other advantages, with the development of the former 765kV has been put into operation in the substation. At present, its shortcomings are expensive, manufacturing and maintenance process requires high.
The substation is also equipped with lightning protection equipment, mainly lightning rods and lightning arrester. Lightning rod is to prevent the substation suffered a direct lightning strike will be lightning on its own discharge of lightning current into the earth. In the substation near the line when the lightning falls on the lightning wave will enter the substation along the wire, resulting in overvoltage. In addition, overvoltage can also be caused by circuit breaker operation. The role of the lightning arrester is when the overvoltage exceeds a certain limit, the automatic discharge to ground to reduce the voltage protection equipment discharge and rapid automatic arc extinguishing, to ensure the normal operation of the system. At present, the most used is zinc oxide lightning arrester. Simply put, there are several aspects of the substation requirements to do lightning protection, a direct lightning protection (mainly to protect the building and substation equipment), the second is the line lightning protection (to prevent lightning wave intrusion), the third is the control system lightning protection (many unattended rooms, divided into power and signal lightning protection)
Simply put, the lightning protection is to set up lightning rods and effective grounding (there are many requirements for independent grounding)
. >. Line lightning protection is mainly the installation of lightning arrester and effective grounding. Control system lightning protection is mainly to do equipotential and hierarchical protection.