A gas charging and discharging rate control method in an online SF6 device live emergency defect elimination process

Abstract

The application discloses a kind of gas filling and discharging rate control methods in online SF6 equipment live emergency defect elimination process, its steps include: step S1: setting sulfur hexafluoride electrical equipment compartment high pressure limit and low pressure limit;Step S2: by automatic control, obtain the volume of single replacement gas, carry out multiple single replacement gas according to certain frequency;Step S3: the temperature, pressure of SF6 gas filled in sulfur hexafluoride electrical equipment are controlled in real time, make the temperature of SF6 gas filled in sulfur hexafluoride electrical equipment consistent or close to ambient temperature, make the gas pressure of SF6 gas filled in sulfur hexafluoride electrical equipment in the safe range of electrical equipment operating pressure.The application has the advantages of simple principle, meet intelligent control demand, can guarantee safety and accuracy etc..

Description

TECHNICAL FIELD

[0001] The present application mainly relates to the technical field of SF6 gas insulated electrical equipment, in particular to a gas charging and discharging rate control method in the online SF6 equipment live emergency defect elimination process. BACKGROUND

[0002] In recent years, with the wide application of SF6 gas insulated electrical equipment in power systems, problems caused by old equipment occur frequently. Gas leakage defects caused by poor sealing of long-term operation of the equipment occur frequently. Once serious gas leakage occurs, personnel need to be arranged to continuously supplement gas to ensure the continuous operation of the equipment, so as to gain time for repair, and the whole maintenance operation is high in intensity and high in safety risk.

[0003] Due to the operation mode of the power grid, the above-mentioned equipment with problems cannot be processed in time or is forced to be shut down, causing loss of power grid load, and the safe and stable operation of the power grid is severely challenged. The conventional processing method needs to transfer the equipment to maintenance, recover SF6 gas in the high-voltage electrical equipment and vacuumize, flush in pure SF6 new gas after nitrogen flushing for several times, and restore operation after passing SF6 micro water detection and gas composition detection. The process is complex, a large amount of manpower and material resources are needed, there is a great operation risk in power restoration, and the power supply reliability of the power grid is affected.

[0004] At present, there are two main principles of recovery and storage of SF6 gas recovery devices, the first one is the refrigeration liquefaction principle: in the process of SF6 gas recovery, under a certain SF6 gas pressure, the temperature of SF6 gas is reduced to the saturation vapor temperature under the pressure by using a refrigeration unit, SF6 gas starts to liquefy into liquid, and is stored in liquid form. The advantage is fast recovery speed and fast liquefaction speed; the disadvantage is complex system process; the second one is the high-pressure liquefaction principle, that is, in the process of SF6 gas recovery, under the ambient temperature at that time, the pressure of SF6 gas is increased to the saturation vapor pressure under the temperature by using a compressor, SF6 gas starts to convert into liquid, and is stored in liquid form. When the temperature of SF6 gas (the temperature of SF6 gas after compression by the compressor can reach more than 80℃) exceeds the critical temperature 45.55℃, it cannot be liquefied, at this time, the high-temperature and high-pressure SF6 gas can only be converted into liquid after a period of time when its temperature drops below the critical temperature. The advantage is simple system, and the disadvantage is high system working pressure and low recovery efficiency.

[0005] The performance of SF6 gas recovery devices on the market has the following shortcomings:

[0006] (1) SF6 gas recovery device cannot process impurity gas in SF6 electrical equipment online;

[0007] At present, the on-site recovery treatment of the SF6 gas recovery device at home and abroad does not have the function of online treatment of moisture, decomposition products and other impurity gases in the electrical equipment.

[0008] (2) The SF6 gas recovery device has a single function;

[0009] At present, the SF6 gas recovery device at home and abroad has a single function; the main functions are recovery, refilling and vacuum pumping.

[0010] (3) The SF6 gas recovery device is large in size;

[0011] The initial design of the domestic SF6 gas recovery device limits its function mode to recovery or vacuum pumping or filling. If a large SF6 electrical equipment needs to be recovered and treated, more compressors, gas tanks and accessories are required, which are large in size.

[0012] Some practitioners have proposed a SF6 device live emergency defect elimination device, which can efficiently, safely and automatically adjust to improve the reliability of the device, and has high economic and social benefits. It is a SF6 gas micro water and single decomposition product in the running high-voltage switch. The purification treatment method adopted is mainly physical adsorption method; and the principle of "breathing" of oil-free compressor is used to dry the SF6 gas in the high-voltage switch gas chamber.

[0013] However, in the above-mentioned online SF6 device live emergency defect elimination device, no one has paid attention to the influence of the SF6 gas charging and discharging rate on the insulation performance of the running high-voltage electrical equipment, thereby burying the safety hazard. SUMMARY

[0014] The technical problem to be solved by the present application is that in view of the technical problems existing in the prior art, the present application provides a gas charging and discharging rate control method in the online SF6 device live emergency defect elimination process, which has a simple principle, meets the intelligent control demand, and can guarantee safety and accuracy.

[0015] To solve the above technical problems, the present application adopts the following technical scheme:

[0016] A gas charging and discharging rate control method in the online SF6 device live emergency defect elimination process, comprising the following steps:

[0017] Step S1: setting the high-voltage limit value and the low-voltage limit value of the SF6 electrical equipment compartment;

[0018] Step S2: obtaining the volume of single gas replacement by automatic control, and performing multiple single gas replacement at a certain frequency;

[0019] Step S3: Real-time control of the temperature and pressure of the SF6 gas filled in the SF6 electrical equipment, so that the temperature of the SF6 gas filled in the SF6 electrical equipment is consistent or close to the ambient temperature, and the gas pressure of the SF6 gas filled in the SF6 electrical equipment is within the safe range of the operating pressure of the electrical equipment.

[0020] As a further improvement of the method of the present application: a pressure detection device is arranged at the sampling port position of the SF6 electrical equipment, and the internal pressure change of the equipment is monitored in real time, and the control of gas sampling and recharging is realized according to the real-time pressure state information.

[0021] As a further improvement of the method of the present application: in step S3, an SF6 pressure / temperature / density characteristic database is pre-set in the PLC, and the corresponding relationship among the pressure, temperature and density of SF6 is obtained by table lookup in the PLC to obtain real-time data of the gas.

[0022] As a further improvement of the method of the present application: under the premise that the temperature of the gas is unchanged, the pressure difference between the "charging" and "discharging" processes changes in the same way, so that the quality of the gas treated by "charging" and "discharging" is the same.

[0023] As a further improvement of the method of the present application: the single replacement gas volume m is related to the volume V of the SF6 electrical equipment and the settable high and low pressure difference ΔP, and the following equation is obtained:

[0024] m = (ΔP / P) × V × ρ (1)

[0025] In the equation, m is the single replacement gas volume, in kg; ΔP is the difference between the upper and lower limits of the rated pressure of the equipment compartment, in MPa; P is a constant, which is 1 MPa; V is the volume of the SF6 electrical equipment container, in L; and ρ is the density of SF6, which is the density value at the high pressure. Since the gas volumes treated by "charging" and "discharging" are the same, the total amount of gas actually treated M in one "charging-discharging" process is:

[0026] M = 2m = 2(ΔP / P) × V × ρ (2)

[0027] The "charging-discharging" cycle treatment adopts the recovery rate v of the SF6 compressor, and the time T required for one cycle of the breathing cycle treatment is calculated as:

[0028] T = M / v (3)

[0029] T is the time required for one "charging-discharging" process, in hours.

[0030] As a further improvement of the method of the present application: the single replacement gas volume is determined by the volume of the SF6 electrical equipment compartment to be treated and the settable pressure difference; and the gas treatment frequency is determined by the single replacement gas volume and the recovery rate of the compressor.

[0031] As a further improvement of the method of the present application: also provided is a gas storage tank pre-charged with qualified new SF6 gas at a certain pressure, when the gas pressure in the gas chamber to be treated is insufficient or needs to be supplemented, the gas chamber is directly supplemented with gas through the gas storage tank.

[0032] Compared with the prior art, the present application has the advantages that:

[0033] The gas charge and discharge rate control method in the online SF6 device live emergency defect elimination process of the present application has simple principle, meets the intelligent control requirement, and can guarantee safety and accuracy, and the gas pressure in the electrical device gas chamber should be ensured within the safe range when the gas is taken. That is, the gas pressure in the gas chamber during the gas taking and gas recharging process is not lower than the lower limit of safety, and is also not higher than the upper limit of pressure. Therefore, a pressure detection device is designed at the sampling port position to monitor the internal pressure change of the device in real time, and the gas sampling and recharging control is realized according to the real-time pressure state information. Finally, the safe operation of the electrical device can be guaranteed. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 is a flowchart of the method of the present application.

[0035] Figure 2 is a control flowchart in a specific application example of the present application.

[0036] Figure 3 is an SF6 pressure / temperature / density characteristic diagram in a specific application example of the present application. DETAILED DESCRIPTION

[0037] The present application will be further described in detail below in combination with the drawings and specific embodiments of the present application.

[0038] Since the internal pressure of the electrical device needs to be maintained within a safe range during operation, when the emergency defect elimination device is operated, the charge and discharge rate of the SF6 gas needs to be reasonably and effectively controlled, according to the safe range of the electrical device operating pressure and the volume of the gas chamber, a suitable power device is selected, so that the amount of gas replaced each time is not more than the safe range. It needs to be particularly pointed out that the method of the present application is mainly based on automatic charge and discharge equipment, and does not involve manual method, therefore the whole control process is an intelligent and automatic control process, which depends on the intelligent processing flow of PLC. In the automatic control process, the charge and discharge rate control of the gas needs intelligent processing.

[0039] As shown in Figure 1 and Figure 3 , a gas charge and discharge rate control method in an online SF6 device live emergency defect elimination process of the present application, which comprises:

[0040] Step S1: Set the high-voltage and low-voltage limits for the sulfur hexafluoride electrical equipment compartment;

[0041] Step S2: Obtain the volume of gas for a single replacement through automatic control, and perform multiple single gas replacements at a certain frequency;

[0042] Step S3: Real-time control of the temperature and pressure of SF6 gas in the sulfur hexafluoride electrical equipment, so that the temperature of SF6 gas in the sulfur hexafluoride electrical equipment is the same as or close to the ambient temperature, and the gas pressure of SF6 gas in the sulfur hexafluoride electrical equipment is within the safe range of the operating pressure of the electrical equipment.

[0043] In a specific application example, the present invention sets up a pressure detection device at the sampling port of the SF6 equipment to monitor the pressure changes inside the equipment in real time, and realizes the control of gas sampling and recharging based on the real-time pressure status information.

[0044] In a specific application example, in step S3, an SF6 pressure / temperature / density characteristic database is pre-set in the PLC. During actual operation, the PLC looks up the corresponding relationship between pressure, temperature and density in SF6 by looking up a table, thereby obtaining accurate real-time gas data.

[0045] In a specific application example, the present invention further adds a dedicated gas storage tank, which is pre-filled with qualified new SF6 gas at a certain pressure. When the gas pressure in the gas chamber being treated is insufficient or needs to be replenished, the gas can be directly replenished to the gas chamber through the dedicated gas storage tank.

[0046] In a specific example, the present invention utilizes the characteristic that changes in gas pressure of SF6 at the same temperature will lead to changes in density, based on the SF6 pressure / temperature / density characteristic curve (…). Figure 3 Under the premise that the gas temperature remains constant, the pressure difference changes in the "filling" and "releasing" processes are the same, so the gas quality is the same in both processes.

[0047] according to Figure 3 The densities of SF6 at 20℃ and at 0.6MPa and 0.5MPa are found to be ρ1 = 45g / l and ρ2 = 40g / l, respectively.

[0048] For SF6 in an inner container of the same volume (110L), when the gas pressure decreases from 0.6MPa to 0.5MPa, the change in the mass of the gas in the volume is as follows:

[0049] At 0.6 MPa, the mass of a 110 L volume of gas is: M1 = Vρ1 = 110 L * 45 g / L = 4950 g;

[0050] 0.5MPa, 110L volume gas mass is: M2 = 2Vp = 110L*40g / l = 4400g;

[0051] Then, the volume gas mass change is: M = M1-M2 = 4950-4400 = 550g;

[0052] The change is the suction process change, i.e. the single replacement gas volume. However, the replacement gas volume is only the theoretical value under the set volume, set pressure and difference at 20°C. In the specific field treatment, it is impossible to suck gas to the allowable stop pressure value in single replacement, and the volume of the gas chamber to be treated is not the same, the environmental temperature and the allowable pressure value are not the same, and the density difference is also irregular, so the above density difference calculation replacement gas volume has precision deviation. Therefore, according to the engineering actual experience value, the influence relationship between the density difference Δp and the pressure value ΔP is described by the following formula.

[0053] According to the filling and discharging cycle treatment process:

[0054] The single replacement gas volume (m) is mainly related to the volume (V) of the sulfur hexafluoride electrical equipment and the settable high and low pressure difference (ΔP) of the sulfur hexafluoride electrical equipment. It can be obtained that:

[0055] m = (ΔP / P) x V x p (1)

[0056] In the formula, m is the single replacement gas volume, unit kg;

[0057] ΔP is the difference between the upper and lower limits of the rated pressure of the device compartment, unit MPa;

[0058] P is a constant, which is 1MPa;

[0059] V is the volume of the sulfur hexafluoride electrical equipment, unit L.

[0060] p is the SF6 density, which is the density value under the high pressure value

[0061] Since the gas volume of "filling" and "discharging" treatment is the same, the total amount of gas actually treated in one filling and discharging process (M) is:

[0062] M = 2m = 2(ΔP / P) x V x p (2)

[0063] The "filling-discharging" cycle treatment adopts the recovery rate v of the sulfur hexafluoride compressor, so the time T used in one cycle of the breathing cycle treatment can be calculated:

[0064] T = M / v (3)

[0065] In formula (3), T is the time required for one filling and discharging process, unit hour.

[0066] According to the formula (1), (2), (3), it can be known that:

[0067] The single replacement gas amount is mainly determined by the volume of the compartment of the sulfur hexafluoride electrical equipment to be treated and the settable pressure difference value; and the gas treatment frequency is determined by the single replacement gas amount and the compressor recovery rate.

[0068] As can be seen from the above, the present application studies the automatic air supplement strategy, formulates the execution air supplement process starting pressure and air supplement stopping pressure, and when the gas pressure in the electrical equipment is lower than the starting pressure, the system automatically starts the air supplement process, and when the pressure in the electrical equipment reaches the air supplement stopping pressure, the system stops air supplement. The process of the charge-discharge cycle treatment mode is as follows: the high and low pressure limits of the compartment of the sulfur hexafluoride electrical equipment to be treated are set, and the air is discharged to stop when reaching the low pressure limit, and the air is charged to stop when reaching the high pressure limit.

[0069] In order to illustrate the above method of the present application, a pressure container with a volume of about 110L is selected for testing, the rated maximum pressure is set to 0.6MPa, the rated minimum pressure is set to 0.5MPa, the pressure fluctuation interval is 0.1MPa, at the same time, in order to ensure that the maximum amount is reached each time, the air discharge stopping pressure is set to 0.5MPa, the air charge stopping pressure is set to 0.6MPa, and the compressor recovery rate is 10kg / h. The adsorbent usage amount of the treatment equipment is 12kg, and the maximum usage time (saturation time) of the adsorbent is 493.7h. The treatment of a larger micro water content (1000μL / L) has a target micro water content according to the standard GB / T8905-2012, and the operating humidity of the arc extinguishing chamber is not higher than 300μL / L (mass ratio is about 37.5ppm). According to the rated maximum pressure 0.6MPa, the rated minimum pressure 0.5MPa and the pressure fluctuation interval 0.1MPa of the combined electrical equipment.

[0070] According to the sulfur hexafluoride compressor recovery rate v used in the charge-discharge cycle treatment, the time T used in one cycle of the charge-discharge cycle treatment can be calculated (formula 3):

[0071] The relationship between the adsorption time (Tadsorption) of the adsorbent and the adsorbent usage amount (B) is:

[0072]

[0073] In order to ensure the safe operation of the SF6 electrical equipment, the gas pressure in the compartment of the equipment to be treated should be ensured within the allowable safe range during the replacement process. That is, the gas pressure in the chamber cannot be lower than the lower limit of safety, nor can it be higher than the upper limit of pressure when taking and charging the gas. Therefore, a pressure gauge is arranged at the sampling port to detect the gas pressure in real time, and the gas sampling and charging control is realized according to the real-time pressure state.

[0074] At the same time, considering the possibility of intermediate pressure value of the gas pressure in the processing compartment, a special gas tank is added to pre-charge a certain pressure of qualified new SF6 gas, when the gas pressure of the processing gas chamber is insufficient or needs to be supplemented, the special gas tank can directly supplement the gas chamber to ensure that the pressure is always maintained within the normal range during the replacement process.

[0075] 1) According to the relationship between SF6 gas pressure and density, the theoretical calculation formula of the gas charging and discharging amount is obtained to provide theoretical support for the control strategy.

[0076] Taking a 110 volume container as an example, when the gas pressure decreases from 0.6MPa to 0.5MPa, the volume gas mass changes as follows:

[0077] At 0.6MPa, the 110L volume gas mass is M1=Vp1=110L*45g / l=4950g;

[0078] At 0.5MPa, the 110L volume gas mass is M2=2Vp=110L*40g / l=4400g;

[0079] Then, the volume gas mass change is M=M1-M2=4950-4400=550g;

[0080] 2) According to the charging and discharging amount, the charging and discharging rate control strategy is obtained, the internal pressure of the electrical equipment is detected in real time, and the charging and discharging stop control node is controlled through the upper and lower limits of the pressure, that is, the gas pressure in the gas chamber when taking gas and recharging gas cannot be lower than the safety lower limit, nor higher than the pressure upper limit. According to the rated maximum pressure 0.6MPa and the rated minimum pressure 0.5MPa of the combined electrical equipment, the pressure fluctuation interval is 0.1MPa.

[0081] The above is only a preferred embodiment of the present application, and the protection scope of the present application is not limited to the above-mentioned embodiments, and any technical solution falling within the concept of the present application shall fall within the protection scope of the present application. It should be noted that for ordinary skilled persons in the art, some improvements and decorations without departing from the principles of the present application shall be considered as the protection scope of the present application.

Claims

1. A method for controlling the rate of gas charging and discharging in an online SF6 equipment live emergency defect elimination process, characterized in that, The application comprises the following steps: Step S1: setting high and low pressure limits of a sulfur hexafluoride electrical equipment compartment; Step S2: obtaining a single replacement gas volume through automatic control and performing multiple single replacement gases at a certain frequency; Step S3: real-time controlling the temperature and pressure of the SF6 gas filled in the sulfur hexafluoride electrical equipment, so that the temperature of the SF6 gas filled in the sulfur hexafluoride electrical equipment is consistent or close to the ambient temperature, and the gas pressure of the SF6 gas filled in the sulfur hexafluoride electrical equipment is within the safe range of the electrical equipment operating pressure; In step S2, an SF6 pressure characteristic database, a temperature characteristic database, and a density characteristic database are pre-set in a PLC, the PLC obtains real-time gas data by looking up the corresponding relationship among the pressure, temperature, and density of the SF6 through a table lookup method; under the premise that the gas temperature is unchanged, the pressure difference between the "filling" and "discharging" processes changes in the same way, so the gas quality treated by the "filling" and "discharging" processes is the same; The single replacement gas volume m is related to the sulfur hexafluoride electrical equipment volume V and the set high and low pressure difference ΔP of the sulfur hexafluoride electrical equipment, and the following equation is obtained: m = (ΔP / P) × V × ρ (1) In the equation, m is the single replacement gas volume, unit: kg; ΔP is the difference between the upper and lower limits of the equipment compartment rated pressure, unit: MPa; P is a constant, which is 1 MPa; V is the sulfur hexafluoride electrical equipment volume, unit: L; ρ is the SF6 density, which is the density value under the high pressure; since the gas volumes treated by the "filling" and "discharging" processes are the same, the total gas volume M treated in one filling and discharging process is: M = 2m = 2(ΔP / P) × V × ρ (2) The "filling-discharging" cycle treatment adopts the recovery rate v of the sulfur hexafluoride compressor, and the time T required for one breathing cycle treatment is calculated as follows: T = M / v (3) T is the time required for one filling and discharging process, unit: hour.

2. The method of claim 1, wherein the method is used in a process of online SF6 equipment charged emergency defect elimination, and the method is characterized in that, A pressure detection device is arranged at the sampling port position of the sulfur hexafluoride electrical equipment to monitor the internal pressure change of the equipment in real time, and the gas sampling and recharging control is realized according to the real-time pressure state information.

3. The method according to any one of claims 1-2, wherein, A gas storage tank is further arranged, the gas storage tank is pre-charged with a certain pressure of qualified new SF6 gas, and when the gas pressure of the treated gas chamber is insufficient or needs to be supplemented, the gas chamber is directly supplemented with gas through the gas storage tank.

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