CN216751311U - A GIS depressurization integrated system for thermal power plants - Google Patents

Abstract

The utility model discloses a GIS voltage reduction integrated system for a thermal power plant, which comprises: a factory alternating current 6.3kV unit and a factory GIS voltage reduction integrated unit; 6.3kV in the factory alternating current 6.3kV unit converges alternating current bus with power electronics vary voltage AC/DC current conversion equipment links to each other in the factory GIS step-down integration unit, through factory GIS step-down integration unit realizes step-down and power transmission, operates circuit breaker and isolator device supply power to factory 400V for the thermal power plant in the factory GIS step-down integration unit. According to the utility model, the 6.3kV/400V power electronic transformer is adopted, the occupied area is effectively reduced, the power electronic transformer is added into the GIS overall equipment, a factory GIS voltage reduction integrated system is constructed, and the regulation and control of the factory power link of the thermal power plant are more flexible.

Description

A GIS depressurization integrated system for thermal power plants

technical field

The utility model relates to a GIS step-down integrated system for thermal power plants, which adopts a 6.3kV/400V power electronic transformer to effectively reduce the floor space. Therefore, the regulation and control of the power consumption of thermal power plants is more flexible.

Background technique

Deploying gas-insulated metal-enclosed switchgear (GIS) in power plant stations has the advantages of high power supply reliability, less electromagnetic pollution, long maintenance period, and low operating noise. GIS is composed of circuit breakers, isolating switches, grounding switches, transformers, arresters, bus bars, connectors and outgoing terminals, etc. These devices or components are all enclosed in a metal grounded shell, which is filled with SF6 insulation with a set pressure inside. gas, so it is also called SF6 fully enclosed combined electrical appliances. GIS adopts advanced power electronic technology, microelectronic technology, sensing technology, digital processing technology, computer technology, control technology, and integrates the functions of monitoring, measurement, control, protection and wave recording.

Power electronic transformers have certain advantages in power quality regulation and harmonic suppression. Functional advantage. The volume of power electronic transformers is well controlled due to the use of high-frequency transformers.

At present, power plants generally use step-down transformers for power consumption. The step-down transformers occupy a large area and cannot be integrated with subsequent GIS equipment. The use of power electronic transformer + GIS equipment integrated step-down system can realize the coordinated integration of GIS step-down, easy installation and easy maintenance. Adding power electronic transformers to GIS equipment can also prolong the service life of power electronic transformers.

Utility model content

The purpose of this utility model is to provide a thermal power plant GIS step-down integrated system, which adopts a 6.3kV/400V power electronic transformer to effectively reduce the footprint, adds the power electronic transformer to the GIS overall equipment, and constructs a factory-use GIS. The step-down integrated system makes the regulation of power consumption in thermal power plants more flexible.

In order to achieve the above object, the utility model adopts the following technical scheme to realize:

A plant-use GIS step-down integrated system for a thermal power plant, comprising: a factory-use AC 6.3kV unit and a factory-use GIS step-down integrated unit;

The 6.3kV confluence AC bus in the factory AC 6.3kV unit is connected to the power electronic transformer AC/DC converter device in the factory GIS step-down integrated unit, and is realized by the factory-use GIS step-down integrated unit Step-down and power transmission, operate the circuit breaker and isolating switchgear in the factory-use GIS step-down integrated unit to supply power to the load of the factory-use 400V thermal power plant.

A further improvement of the utility model is that the factory AC 6.3kV unit includes: thermal power generator, thermal power unit factory 20kV/400V step-down transformer, 6.3kV factory busbar, 6.3kV factory load grid-connected circuit breaker and 6.3kV plant load;

The outlet of the thermal power generator is connected to the 20kV/400V step-down and high-voltage side of the thermal power unit factory, and the 6.3kV factory-use confluence bus is connected to the 20kV/400V step-down and low voltage side of the thermal power unit factory. The 6.3kV factory load is connected to the 6.3kV factory load busbar through the 6.3kV factory load grid-connected circuit breaker, and the 6.3kV factory load is connected to the 6.3kV factory load by closing the 6.3kV factory load grid-connected circuit breaker. powered by.

A further improvement of the present utility model is that the integrated unit for GIS step-down includes: 6.3kV/400V power electronic transformer AC/DC converter, power electronic transformer high-voltage side filter capacitor, 6.3kV/400V power electronic transformer Voltage isolation DC-DC converter, low-voltage side filter capacitor of power electronic transformer and 6.3kV/400V power electronic transformer DC/AC converter;

The AC side of the 6.3kV/400V power electronic transformer AC/DC converter is connected to the 6.3kV factory busbar, and the 6.3kV AC power is passed through the 6.3kV/400V power electronic transformer AC/DC converter. The current transformer is converted into 8.9kV high-voltage direct current, and the 8.9kV high-voltage direct current is filtered by the high-voltage side filter capacitor of the power electronic transformer and transmitted to the 6.3kV/400V power electronic transformer isolation DC-DC converter. The 6.3kV/ The 400V power electronic transformer isolated DC-DC converter converts 8.9kV high voltage direct current into 565.5V low voltage direct current, and the 565.5V low voltage direct current is filtered by the low voltage side filter capacitor of the power electronic transformer and transmitted to the 6.3kV/400V power electronic The transformer DC/AC converter is converted into a 400V AC power plant after being inverted by the 6.3kV/400V power electronic transformer DC/AC converter, and the voltage conversion and voltage reduction are completed.

A further improvement of the utility model is that the 6.3kV/400V power electronic transformer isolation type DC-DC converter includes: a single-phase full-bridge inverter, an isolation type DC-DC converter filter inductance isolation type DC-DC converter filter capacitor, 6.3kV/400V high frequency transformer and single-phase full bridge rectifier;

The single-phase full-bridge inverter is connected in series to the high-voltage side of the 6.3kV/400V high-frequency transformer through the isolated DC-DC converter filter inductor and the isolated DC-DC converter filter capacitor. The full-bridge inverter realizes the conversion of electric energy from DC to AC, and the low-voltage side of the 6.3kV/400V high-frequency transformer is connected to the single-phase full-bridge rectifier.

A further improvement of the present invention is that the rated frequency of the 6.3kV/400V high-frequency transformer is 10 kHz, and the voltage is changed by changing the frequency; and the 6.3kV/400V high-frequency transformer can reduce the voltage by reducing the frequency.

A further improvement of the present invention is that the single-phase full-bridge rectifier realizes the conversion of electric energy from alternating current to direct current.

A further improvement of the utility model is that the 6.3kV/400V power electronic transformer AC/DC converter, the 6.3kV/400V power electronic transformer DC/AC inverter and the single-phase full-bridge inverter The single-phase full-bridge rectifier adopts high-power high-frequency IGBT components to achieve unit power factor operation or real-time power adjustment requirements according to the power load, and operate according to a given power factor.

A further improvement of the present utility model is that the integrated unit for reducing the voltage of the factory-use GIS further comprises: a 400V factory-use power transmission line isolation switch, a 400V factory-use power transmission line power generation side grounding switch, and a 400V factory-use power transmission line;

The 6.3kV/400V power electronic transformer DC/AC converter is connected to the 400V factory power transmission line through the 400V factory power transmission line isolation switch. The low-voltage alternating current with voltage conversion and step-down is transmitted to the 400V factory-use transmission line; the 400V factory-use transmission line isolation switch is used to isolate the power generation equipment from the power equipment, switch off operation, and connect and cut off the small current circuit. Function; the grounding switch on the power generation side of the 400V factory transmission line is close to the power generation side, and when the equipment close to the power generation side is repaired, it plays the role of releasing the static electricity of the repaired equipment and the circuit.

A further improvement of the present utility model is that the integrated unit for reducing the voltage of the factory-use GIS further comprises: a 400V factory-use transmission line circuit breaker, a 400V factory-use power transmission line center grounding switch, a 400V factory-use power transmission line load-side voltage transformer, a 400V factory-use power transmission line load-side voltage transformer, The grounding switch on the load side of the factory transmission line and the 400V factory load;

The 400V factory-use transmission line circuit breaker is connected in series with the 400V factory-use transmission line, which can close, carry and break the current under normal circuit conditions and can close, carry and break the abnormal circuit within a specified time. The role of the current under the condition; the 400V factory-use transmission line center grounding switch, close to the center of the transmission line, when the equipment close to the center of the transmission line is repaired, it plays the role of releasing the static electricity of the repaired equipment and the circuit; the 400V factory-use The voltage transformer on the load side of the transmission line realizes the voltage sampling on the load side, and is divided into protection and measurement voltage transformers; the 400V factory-use transmission line load side grounding switch is close to the transmission line load side, and the equipment maintenance on the transmission line load side When the 400V factory load is connected to the end of the 400V factory power transmission line, it plays the role of releasing the static electricity of the equipment to be repaired and the circuit; it is an electrical equipment.

A further improvement of the utility model is that the GIS equipment in the factory-use GIS depressurization integrated unit is all enclosed in a metal grounded casing, and the interior is filled with SF6 insulating gas with a set pressure.

Compared with the prior art, the present utility model at least has the following beneficial technical effects:

1. The utility model adopts the power electronic transformer comprising the high-frequency transformer in the described factory-use GIS step-down integrated unit to realize frequency conversion and voltage transformation, and the high-frequency transformer rated frequency is 10kHz, and the voltage level is reduced by changing the frequency, Compared with traditional transformers, it is smaller in size and easy to maintain.

2. The utility model adopts a power electronic transformer including an AC/DC converter device in the factory-use GIS step-down integrated unit, which can realize unit power factor operation or real-time power adjustment requirements according to the power load, according to a given power factor operation. Using high-power high-frequency IGBT components, the maximum short-circuit current that can be provided does not exceed 1.5 times of its rated current. The protection judgment logic is simple and efficient, and the factory load can be switched freely.

3. The utility model adopts a complete set of GIS power consumption units in the described factory-use GIS depressurization integrated unit, the GIS equipment is all enclosed in a metal grounded casing, and the SF6 insulating gas of the set pressure is filled in it, whether it is Circuit breaker, isolating switch or grounding switch will not generate high-voltage arc at the moment of opening and closing, which is safer and more reliable.

4. The utility model adopts a 6.3kV/400V power electronic transformer in the said factory-use GIS step-down integrated unit, which effectively reduces the footprint, adds the power electronic transformer to the GIS overall equipment, and adopts the power electronic transformer+GIS. The equipment-integrated step-down system can realize the coordinated integration of GIS step-down, which is convenient for installation and maintenance, and can also prolong the service life of power electronic transformers.

Description of drawings

Fig. 1 is a circuit diagram of a thermal power plant GIS depressurization integrated system of the utility model.

Description of reference numbers:

1—factory AC 6.3kV unit; 2—factory GIS step-down integrated unit;

1-1—thermal power generator; 1-2—20kV/400V step-down transformer for thermal power unit plant; 1-3—6.3kV plant busbar; 1-4—6.3kV plant load-connected circuit breaker; 1- 5—6.3kV plant load;

2-1—6.3kV/400V Power Electronic Transformer AC/DC Converter; 2-2—Power Electronic Transformer High Voltage Side Filter Capacitor; 2-3—6.3kV/400V Power Electronic Transformer Isolated DC-DC Converter ;2-3-1—single-phase full-bridge inverter; 2-3-2—isolated DC-DC converter filter inductor; 2-3-3—isolated DC-DC converter filter capacitor; 2-3 -4—6.3kV/400V high frequency transformer; 2-3-5—single-phase full-bridge rectifier; 2-4—low-voltage side filter capacitor of power electronic transformer; 2-5—6.3kV/400V power electronic transformer DC/AC Inverter; 2-6—400V power transmission line isolation switch; 2-7—400V power generation side grounding switch; 2-8—400V power transmission line; 2-9—400V power transmission line circuit breaker 2-10-400V factory-use transmission line center grounding switch; 2-11-400V factory-use transmission line load-side voltage transformer; 2-12-400V factory-use transmission line load-side grounding switch; 2-13-400V factory use load.

Detailed ways

The technical solutions of the present utility model are further described in detail below through the accompanying drawings.

As shown in Figure 1, the utility model provides a thermal power plant GIS step-down integrated system, including: a factory AC 6.3kV unit 1 and a factory GIS step-down integrated unit 2; the factory AC 6.3kV unit 2; The 6.3kV confluence AC bus in the kV unit 1 is connected to the power electronic transformer AC/DC converter device in the factory-used GIS step-down integrated unit 2, and the step-down and For power transmission, operate the circuit breaker and isolating switchgear in the factory-use GIS step-down integrated unit 2 to supply power to the load of the factory-use 400V thermal power plant.

The factory AC 6.3kV unit 1 includes: thermal power generator 1-1, thermal power unit factory 20kV/400V step-down transformer 1-2, 6.3kV factory busbar 1-3, 6.3kV factory load grid-connected circuit breaker 1-4 and 6.3kV plant loads 1-5.

The outlet of the thermal power generator 1-1 is connected to the high voltage side of the thermal power unit factory 20kV/400V step-down transformer 1-2, and the thermal power unit factory 20kV/400V step-down transformer 1-2 low-voltage side is connected to the 6.3kV industrial busbars 1-3, the 6.3kV industrial loads 1-5 are connected to the 6.3kV industrial busbars 1-3 through the 6.3kV industrial load grid-connected circuit breakers 1-4, through The grid-connected circuit breakers 1-4 of the 6.3kV industrial loads are closed to supply power to the 6.3kV industrial loads 1-5.

The factory-use GIS step-down integrated unit 2 includes: 6.3kV/400V power electronic transformer AC/DC converter 2-1, power electronic transformer high-voltage side filter capacitor 2-2, 6.3kV/400V power electronic transformer Isolated DC-DC converter 2-3, power electronic transformer low-voltage side filter capacitor 2-4, 6.3kV/400V power electronic transformer DC/AC converter 2-5, 400V factory transmission line circuit breaker 2-9 , 400V factory power transmission line center grounding switch 2-10, 400V factory power transmission line load side voltage transformer 2-11, 400V factory power transmission line load side grounding switch 2-12 and 400V factory load 2-13.

The AC side of the 6.3kV/400V power electronic transformer AC/DC converter 2-1 is connected to the 6.3kV factory busbar 1-3, and the 6.3kV AC factory power is passed through the 6.3kV/400V power electronics The transformer AC/DC converter 2-1 is converted into 8.9kV high voltage direct current, and the 8.9kV high voltage direct current is filtered by the high-voltage side filter capacitor 2-2 of the power electronic transformer and transmitted to the 6.3kV/400V power electronic transformer isolation Type DC-DC converter 2-3, the 6.3kV/400V power electronic transformer isolation type DC-DC converter 2-3 converts 8.9kV high-voltage direct current into 565.5V low-voltage direct current, and the 565.5V low-voltage direct current passes through the power The low-voltage side filter capacitor 2-4 of the electronic transformer is filtered and transmitted to the 6.3kV/400V power electronic transformer DC/AC converter 2-5, and passed through the 6.3kV/400V power electronic transformer DC/AC inverter After 2-5 inversion, it becomes 400V AC factory power, and the conversion and voltage reduction are completed.

The 6.3kV/400V power electronic transformer isolated DC-DC converter 2-3 includes: a single-phase full-bridge inverter 2-3-1; an isolated DC-DC converter filter inductor 2-3-2; Isolated DC-DC converter filter capacitor 2-3-3; 6.3kV/400V high-frequency transformer 2-3-4; single-phase full-bridge rectifier 2-3-5. The single-phase full-bridge inverter 2-3-1 is connected in series with the isolated DC-DC converter filter inductor 2-3-2 and the isolated DC-DC converter filter capacitor 2-3-3. The high-voltage side of the 6.3kV/400V high-frequency transformer 2-3-4, the single-phase full-bridge inverter 2-3-1 realizes the transformation of electric energy from DC to AC, and the 6.3kV/400V high-frequency transformer 2-3 -4 The low voltage side is connected to the single-phase full-bridge rectifier 2-3-5. The rated frequency of the 6.3kV/400V high-frequency transformer 2-3-4 is 10kHz, and the voltage can be changed by changing the frequency. Compared with the traditional transformer, the volume is smaller and the maintenance is convenient. The 6.3kV/400V high-frequency transformer 2-3-4 realizes voltage reduction by reducing the frequency. The single-phase full-bridge rectifier 2-3-5 realizes the conversion of electric energy from alternating current to direct current.

The 6.3kV/400V power electronic transformer AC/DC converter 2-1, the 6.3kV/400V power electronic transformer DC/AC converter 2-5 and the single-phase full-bridge inverter 2 -3-1. The single-phase full-bridge rectifier 2-3-5 adopts high-power high-frequency IGBT components, which can realize unit power factor operation or real-time power adjustment requirements according to the power load, and operate according to a given power factor. Using high-power high-frequency IGBT components, the maximum short-circuit current that can be provided does not exceed 1.5 times of its rated current. The protection judgment logic is simple and efficient, and the factory load can be switched freely.

The 6.3kV/400V power electronic transformer DC/AC converter 2-5 is connected to the 400V factory power transmission line 2-8 through the 400V factory power transmission line isolation switch 2-6, and by closing the power transmission line The line isolation switch 2-6 transmits the low-voltage alternating current that has been transformed and stepped down by the power electronics to the 400V factory-use power transmission line 2-8. The 400V factory-use power transmission line isolation switch 2-6 plays the role of isolating power generation equipment and electrical equipment, switching off operation, and connecting and cutting off small current circuits. The grounding switch 2-7 on the power generation side of the 400V factory transmission line is close to the power generation side, and when the equipment close to the power generation side is repaired, it plays the role of releasing the static electricity of the repaired equipment and the circuit.

The 400V factory power transmission line circuit breaker 2-9 is connected in series with the 400V factory power transmission line 2-8, which can close, carry and break the current under normal circuit conditions, and can close, The role of carrying and breaking currents under abnormal circuit conditions. The 400V factory-use transmission line center grounding switch 2-10, which is close to the center of the transmission line, plays the role of releasing the static electricity of the equipment to be repaired and the circuit when the equipment close to the center of the transmission line is overhauled. The load-side voltage transformers 2-11 of the 400V factory-use transmission line can realize load-side voltage sampling, and are divided into protection voltage transformers and measurement voltage transformers. The grounding switch 2-12 on the load side of the 400V factory transmission line is close to the load side of the transmission line. When the equipment on the load side of the transmission line is overhauled, it plays the role of releasing the static electricity of the overhauled equipment and the circuit. The 400V factory load 2-13 is connected to the end of the 400V factory power transmission line 2-8, and is an electrical equipment.

The GIS equipment in the factory-use GIS step-down integrated unit 2 is all enclosed in a metal grounded casing, and the inside is filled with SF6 insulating gas with a set pressure, whether it is the 400V factory-use transmission line isolation switch 2-6 , 2-7 grounding switch on the power generation side of the 400V factory transmission line, 2-9 on the power generation side of the 400V factory power transmission line, 2-9 on the central grounding switch on the 400V factory power transmission line, 2-10 on the load side of the 400V factory power transmission line The grounding switch 2-12 will not generate high-voltage arc at the moment of opening and closing, which is safer and more reliable. The 6.3kV/400V high-frequency transformer 2-3-4 is used to effectively reduce the floor space. The power electronic transformer is added to the overall GIS equipment, and the power electronic transformer + GIS equipment integrated step-down system can be used to achieve GIS reduction. The integration of voltage and synergy is convenient for installation and maintenance, and can also prolong the service life of power electronic transformers.

Although the present utility model has been described in detail above with general description and specific embodiments, some modifications or improvements can be made on the basis of the present utility model, which is obvious to those skilled in the art. Therefore, these modifications or improvements made on the basis of not departing from the spirit of the present invention belong to the scope of protection of the present invention.

Claims (10)

1. The utility model provides a thermal power plant factory is with GIS step-down integration system which characterized in that includes: a factory alternating current 6.3kV unit (1) and a factory GIS voltage reduction integrated unit (2);

6.3kV in the factory alternating current 6.3kV unit (1) converges alternating current bus with power electronics vary voltage AC/DC current conversion device links to each other in the factory GIS step-down integration unit (2), through factory GIS step-down integration unit (2) realizes step-down and power transmission, operates circuit breaker and isolator device supply power to factory 400V for thermal power plant load in the factory GIS step-down integration unit (2).

2. The GIS voltage reduction integrated system for the factory of the thermal power plant as claimed in claim 1, wherein the factory alternating current 6.3kV unit (1) comprises: the system comprises a thermal power generator (1-1), a 20kV/400V step-down transformer (1-2) for a thermal power plant, a 6.3kV station busbar (1-3), a 6.3kV station load grid-connected circuit breaker (1-4) and a 6.3kV station load (1-5);

thermal power generator (1-1) exit linkage has thermal power plant factory is with 20kV 400V step-down change (1-2) high pressure side, thermal power plant factory is with 20kV 400V step-down change (1-2) low pressure side is connected with 6.3kV factory is with busbar (1-3), 6.3kV factory is with load (1-5) through 6.3kV factory is with load grid-connected circuit breaker (1-4) be connected to 6.3kV factory is with busbar (1-3), through closed 6.3kV factory is with load grid-connected circuit breaker (1-4), to 6.3kV factory is with load (1-5) power supply.

3. The GIS pressure reduction integrated system for the plant of the thermal power plant as claimed in claim 2, wherein the GIS pressure reduction integrated unit (2) for the plant comprises: the power electronic transformation system comprises a 6.3kV/400V power electronic transformation AC/DC converter (2-1), a power electronic transformer high-voltage side filter capacitor (2-2), a 6.3kV/400V power electronic transformation isolation type DC-DC converter (2-3), a power electronic transformer low-voltage side filter capacitor (2-4) and a 6.3kV/400V power electronic transformation DC/AC converter (2-5);

the 6.3kV/400V power electronic transformation AC/DC converter (2-1) is connected to the 6.3kV station bus (1-3) at the alternating current side, 6.3kV alternating current station power is converted into 8.9kV high-voltage direct current through the 6.3kV/400V power electronic transformation AC/DC converter (2-1), the 8.9kV high-voltage direct current is filtered through the power electronic transformer high-voltage side filter capacitor (2-2) and then transmitted to the 6.3kV/400V power electronic transformation isolation type DC-DC converter (2-3), the 6.3kV/400V power electronic transformation isolation type DC-DC converter (2-3) converts the 8.9kV high-voltage direct current into 565.5V low-voltage direct current, and the 565.5V low-voltage direct current is filtered through the power electronic transformer low-voltage side filter capacitor (2-4) and then transmitted to the 6.3kV/400V power electronic transformation DC/AC converter (2-5), the power is converted into 400V alternating current auxiliary power after being inverted by the 6.3kV/400V power electronic voltage transformation DC/AC converter (2-5), and variable current and voltage reduction are completed.

4. The GIS voltage reduction integrated system for thermal power plant according to claim 3, wherein the 6.3kV/400V power electronic transformation isolation type DC-DC converter (2-3) comprises: the system comprises a single-phase full-bridge inverter (2-3-1), an isolated DC-DC converter filter inductor (2-3-2), an isolated DC-DC converter filter capacitor (2-3-3), a 6.3kV/400V high-frequency transformer (2-3-4) and a single-phase full-bridge rectifier (2-3-5);

the single-phase full-bridge inverter (2-3-1) is connected in series with the high-voltage side of the 6.3kV/400V high-frequency transformer (2-3-4) through the isolated DC-DC converter filter inductor (2-3-2) and the isolated DC-DC converter filter capacitor (2-3-3), the single-phase full-bridge inverter (2-3-1) realizes the conversion of electric energy from direct current to alternating current, and the low-voltage side of the 6.3kV/400V high-frequency transformer (2-3-4) is connected to the single-phase full-bridge rectifier (2-3-5).

5. The GIS voltage reduction integrated system for thermal power plants according to claim 4, characterized in that the rated frequency of the 6.3kV/400V high-frequency transformer (2-3-4) is 10kHz, and voltage change is realized by frequency change; and the 6.3kV/400V high-frequency transformer (2-3-4) realizes voltage reduction by reducing frequency.

6. The GIS voltage reduction integrated system for the thermal power plant factory according to claim 4, wherein the single-phase full-bridge rectifier (2-3-5) realizes conversion of electric energy from AC to DC.

7. The GIS voltage reduction integrated system for the thermal power plant factory according to claim 4, wherein the 6.3kV/400V power electronic transformation AC/DC converter (2-1), the 6.3kV/400V power electronic transformation DC/AC converter (2-5), the single-phase full-bridge inverter (2-3-1) and the single-phase full-bridge rectifier (2-3-5) adopt high-power high-frequency IGBT components to realize unit power factor operation or operation according to given power factor according to real-time power regulation requirements of electric loads.

8. The GIS pressure reduction integrated system for the plant of the thermal power plant as claimed in claim 3, wherein the GIS pressure reduction integrated unit (2) for the plant further comprises: 400V station power transmission line disconnecting switches (2-6), 400V station power transmission line power generation side grounding switches (2-7) and 400V station power transmission lines (2-8);

the 6.3kV/400V power electronic transformation DC/AC converter (2-5) is connected with the 400V station power transmission line (2-8) through the 400V station power transmission line disconnecting switch (2-6), and low-voltage alternating current subjected to power electronic transformation, transformation and voltage reduction is transmitted to the 400V station power transmission line (2-8) by closing the power transmission line disconnecting switch (2-6); the isolating switch (2-6) of the 400V station service transmission line plays a role in isolating power generation equipment and electric equipment, switching operation and communicating and cutting off a low-current circuit; the grounding switch (2-7) on the power generation side of the 400V station power transmission line is close to the power generation side, and plays a role in releasing static electricity of the equipment to be repaired and a loop when the equipment close to the power generation side is repaired.

9. The GIS pressure reduction integrated system for the plant of the thermal power plant as claimed in claim 8, wherein the GIS pressure reduction integrated unit (2) for the plant further comprises: the system comprises a 400V station power transmission line breaker (2-9), a 400V station power transmission line center grounding switch (2-10), a 400V station power transmission line load side voltage transformer (2-11), a 400V station power transmission line load side grounding switch (2-12) and a 400V station power load (2-13);

the 400V station service transmission line circuit breakers (2-9) are connected in series with the 400V station service transmission lines (2-8) to play a role in closing, bearing and opening current under the condition of a normal loop and closing, bearing and opening current under the condition of an abnormal loop within a specified time; the center grounding switch (2-10) of the 400V station-use power transmission line is close to the center of the power transmission line, and plays a role in releasing static electricity of the equipment to be repaired and a loop when equipment close to the center of the power transmission line is repaired; the load side voltage transformers (2-11) of the 400V station power transmission line realize load side voltage sampling and are divided into voltage transformers for protection and measurement; the 400V station service transmission line load side grounding switch (2-12) is close to the transmission line load side, and plays a role in releasing static electricity of the equipment to be repaired and a loop when equipment on the transmission line load side is repaired; the 400V service load (2-13) is connected to the tail end of the 400V service transmission line (2-8) and is power utilization equipment.

10. The thermal power plant service GIS step-down integrated system according to claim 9, wherein the service GIS step-down integrated unit (2) is characterized in that GIS devices are all enclosed in a metal grounded enclosure, and a set pressure of SF6 insulating gas is filled in the enclosure.

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