Method and system for analyzing unbalanced voltage protection action of 10kV parallel capacitor device

Abstract

The invention discloses a 10kV parallel capacitor device unbalanced voltage protection action analysis method and system, and relates to the technical field of unbalanced voltage protection, and the method comprises the steps: analyzing the tripping condition of a capacitor device; carrying out field test diagnosis and three-phase unbalanced voltage calculation; and performing three-phase imbalance protection action simulation analysis. According to the invention, the tripping condition of the 10kV parallel capacitor device is analyzed through the system, and the root cause that the neutral point and the neutral point of the discharge coil are not short-circuited is accurately identified in combination with the field test and the accurate three-phase unbalanced voltage calculation, so that wrong tripping is effectively avoided, the reliability of the protection device is remarkably improved, and the service life of the device is prolonged. The device maintenance cost is reduced, the service life is prolonged, clear operation guidance is provided for operation and maintenance personnel, stable operation and continuous power supply of a power system are ensured, and when fault analysis and diagnosis are carried out, primary devices are analyzed one by one from outside to inside to ensure comprehensiveness.

Description

Technical Field

[0001] The present invention relates to the technical field of unbalanced voltage protection, in particular to a method and system for analyzing the action of unbalanced voltage protection of a 10kV parallel capacitor device. Background Art

[0002] The main function of the shunt capacitor is to improve the power factor by providing capacitive reactive power, thereby reducing losses and increasing system voltage. In response to an incident in which a three-phase unbalanced voltage protection action occurred during the switching process of a 10kV shunt capacitor device, through experimental diagnosis and theoretical calculation, a comprehensive analysis was conducted that the protection action was caused by the fact that the neutral point of the on-site capacitor and the neutral point of the discharge coil were not short-circuited. PSCAD was used to simulate and calculate the unbalanced voltage values ​​under the conditions of short-circuiting and not short-circuiting the neutral points of the capacitor and the discharge coil. The simulation calculation results under the condition of not short-circuiting were basically consistent with the protection recording data, reproducing the process of protection action. At the same time, the simulation concluded that the protection action would not be caused under the condition of short-circuiting, and finally relevant conclusions and suggestions were given based on the simulation calculation results.

[0003] At present, most of the primary equipment used in the AC power system is inductive equipment, such as transformers, reactors, and voltage transformers, which makes the entire power system inductive, consumes a lot of reactive power, and reduces the power factor of the system. In order to improve the power factor, the most mainstream method is to connect capacitor devices in parallel to the low-voltage busbar of the substation to improve the power factor of the load and improve the voltage quality by compensating for reactive power. Therefore, the safe and reliable operation of capacitor devices is a key part of substation operation and maintenance, especially in some key plants or areas with special requirements for power supply quality. However, with the large-scale promotion and use of parallel capacitor devices, the number of abnormal tripping of capacitor devices has also increased.

[0004] Aiming at an accident of "tripping as soon as it is put into operation" of a 10kV shunt capacitor device, the present invention conducts a detailed fault diagnosis and analysis of the tripping situation by combining protection recording, background SOE files, on-site inspection and test analysis results of electrical equipment, and uses electromagnetic transient PSCAD software for simulation verification, and finally determines the cause of the capacitor device tripping, providing a reference for handling related issues of abnormal tripping of shunt capacitor devices. Summary of the invention

[0005] In view of the above-mentioned problems, the present invention is proposed.

[0006] Therefore, the problem to be solved by the present invention is: how to solve the problem of analyzing the accident situation of "tripping as soon as it is thrown" in a 10kV parallel capacitor device.

[0007] To solve the above technical problems, the present invention provides the following technical solutions: a method for analyzing the unbalanced voltage protection action of a 10kV parallel capacitor device, comprising: analyzing the tripping condition of the capacitor device; performing on-site test diagnosis and three-phase unbalanced voltage calculation; and performing three-phase unbalanced protection action simulation analysis.

[0008] As a preferred solution of the method for analyzing the unbalanced voltage protection action of the 10kV parallel capacitor device of the present invention, the analysis of the tripping situation of the capacitor device includes the situation that the 10kV parallel capacitor device trips as soon as it is put into operation. By retrieving the substation background SOE file, the operating status of the parallel capacitor device before tripping is checked. If it is shown that the parallel capacitor device has been in normal operating state before tripping, it is checked whether the comprehensive automation transformation work content is changed for the primary part. If not, on-site test diagnosis is performed.

[0009] As a preferred solution of the method for analyzing the action of unbalanced voltage protection of a 10kV parallel capacitor device of the present invention, the on-site test diagnosis includes analyzing according to the wiring diagram of the parallel capacitor device, and the causes of the three-phase voltage unbalanced tripping fault include internal faults of the capacitor causing large capacitance deviation, internal winding faults of the discharge coil, and reactor faults; if the tripping as soon as the device is thrown is not caused by internal faults of the capacitor causing large capacitance deviation, internal winding faults of the discharge coil, and reactor faults, then a three-phase unbalanced voltage calculation is performed to analyze the cause of the tripping as soon as the device is thrown.

[0010] As a preferred solution of the unbalanced voltage protection action analysis method of the 10kV parallel capacitor device of the present invention, the three-phase unbalanced voltage calculation includes analyzing the cause of the three-phase unbalanced voltage action of the capacitor device after preliminarily determining that the capacitor trip is not caused by the primary equipment parameters, and using the equipment parameters in the device, the bus voltage value and the three-phase unbalanced voltage protection principle to calculate and verify the three-phase unbalanced voltage value under the actual operating conditions. The initial unbalanced voltage is expressed as:

[0011]

[0012] Among them, U P is the initial unbalanced voltage, U O is the neutral point offset voltage, U A , U B , U C is the 10kV bus three-phase voltage, Y A , Y B , Y C is the admittance value of the three-phase capacitance.

[0013] As a preferred solution of the 10kV parallel capacitor device unbalanced voltage protection action analysis method of the present invention, wherein: the three-phase unbalanced voltage calculation also includes importing the actual bus voltage value and the capacitance admittance value into the calculation U P , the unbalanced voltage value is converted according to the transformation ratio of the discharge coil to determine whether the unbalanced voltage value exceeds the protection setting value. If the unbalanced voltage value does not exceed the protection setting value, the three-phase unbalanced protection action simulation is performed to analyze the cause of the tripping situation as soon as it is thrown.

[0014] As a preferred solution of the unbalanced voltage protection action analysis method of the 10kV parallel capacitor device of the present invention, the three-phase unbalanced protection action simulation analysis includes: if the field test diagnosis and the three-phase unbalanced voltage calculation do not find the cause of the tripping situation, then check whether the neutral point of the capacitor and the neutral point of the discharge coil are short-circuited, measure the primary impedance value of the three-phase discharge coil, and calculate the initial unbalanced voltage according to the impedance value, convert the measured discharge coil impedance value into an admittance value, and bring it into the initial unbalanced voltage formula together with the bus voltage value for calculation to obtain the initial unbalanced voltage U P , determine the initial unbalanced voltage U P The relationship between the unbalanced voltage value and the protection recording wave is that if the initial unbalanced voltage U P If the voltage is greater than the unbalanced voltage value in the protection recording, the tripping accident is caused by the protection action due to the failure to short-circuit the neutral points of the two.

[0015] As a preferred solution of the unbalanced voltage protection action analysis method of the 10kV parallel capacitor device described in the present invention, the three-phase unbalanced protection action simulation analysis also includes clarifying the cause of the protection tripping, and using the electromagnetic transient PSCAD software to perform simulation modeling analysis on the neutral point of the capacitor and the neutral point of the discharge coil under two working conditions: not short-circuited and short-circuited.

[0016] Another object of the present invention is to provide a system for analyzing the unbalanced voltage protection action of a 10kV parallel capacitor device, which can solve the problem of analyzing the unbalanced voltage protection action of a 10kV parallel capacitor device by constructing a system for analyzing the unbalanced voltage protection action of a parallel capacitor device.

[0017] To solve the above technical problems, the present invention provides the following technical solutions: a 10kV parallel capacitor device unbalanced voltage protection action analysis system, comprising a tripping analysis module, a diagnostic module and a simulation analysis module; the tripping analysis module is used to analyze the tripping situation of the capacitor device; the diagnostic module is used to perform on-site test diagnosis and three-phase unbalanced voltage calculation; the simulation analysis module is used to perform three-phase unbalanced protection action simulation analysis.

[0018] A computer device comprises a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, the steps of the above-mentioned 10kV parallel capacitor device unbalanced voltage protection action analysis method are implemented.

[0019] A computer-readable storage medium stores a computer program, which, when executed by a processor, implements the steps of the above-mentioned 10kV parallel capacitor device unbalanced voltage protection action analysis method.

[0020] The beneficial effects of the present invention are as follows: the unbalanced voltage protection action analysis method of the 10kV parallel capacitor device provided by the present invention systematically analyzes the tripping situation of the 10kV parallel capacitor device, combines field tests and accurate three-phase unbalanced voltage calculation, accurately identifies the fundamental reason that the neutral point and the neutral point of the discharge coil are not short-circuited, thereby effectively avoiding false tripping, significantly improving the reliability of the protection device, reducing the equipment maintenance cost and extending the service life, and providing clear operation guidance for the operation and maintenance personnel, ensuring the stable operation and continuous power supply of the power system. The present invention determines that the protection malfunction is caused by incorrect primary wiring of the capacitor device on site through on-site comparison and simulation calculation. When the discharge coil and the neutral point of the capacitor are not short-circuited, the zero-sequence voltage mainly reflects the imbalance of the primary winding impedance of the discharge coil, and the operating state of the capacitor cannot be monitored. Only when the discharge coil and the neutral point of the capacitor are short-circuited, because the capacitor impedance value is much smaller than the discharge coil, after being connected in parallel with the discharge coil, the zero-sequence voltage mainly reflects the imbalance of the capacitor capacitance. Therefore, in order to be able to discover the internal defects of the capacitor equipment in advance, it is necessary to short-circuit the neutral points of the two. Even when the discharge coil and the neutral point of the capacitor are short-circuited, the greater the impedance imbalance of the discharge coil, the greater the zero-sequence voltage value. Therefore, when selecting the discharge coil, in addition to conducting tests such as the ratio and volt-ampere characteristics, three-phase discharge coils with small impedance deviations should be selected as much as possible to reduce the initial unbalanced voltage value of the capacitor device. In response to this tripping accident, the equipment still "tripped as soon as it was put into operation" during the comprehensive self-renovation work without changing the primary wiring of the capacitor and ensuring that the secondary wiring was correct. Therefore, when conducting fault analysis and diagnosis, the primary equipment should be analyzed one by one from the outside to the inside to ensure comprehensiveness. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative labor.

[0022] Figure 1 This is a flow chart of a method for analyzing the unbalanced voltage protection action of a 10kV parallel capacitor device provided in the first embodiment of the present invention.

[0023] Figure 2 A wiring diagram of a parallel capacitor device for analyzing the unbalanced voltage protection action of a 10kV parallel capacitor device provided by the first embodiment of the present invention.

[0024] Figure 3 A three-phase unbalanced voltage protection principle diagram of the unbalanced voltage protection action analysis method for a 10kV parallel capacitor device provided in the first embodiment of the present invention.

[0025] Figure 4 This is an incorrect wiring diagram of an on-site parallel capacitor device according to a method for analyzing unbalanced voltage protection action of a 10kV parallel capacitor device provided by the first embodiment of the present invention.

[0026] Figure 5 This is a structural diagram of a 10kV parallel capacitor device unbalanced voltage protection action analysis system provided in a second embodiment of the present invention.

[0027] Figure 6 This is a PSCAD simulation model diagram of the unbalanced voltage protection action analysis method for a 10kV parallel capacitor device provided in the third embodiment of the present invention.

[0028] Figure 7 This is a three-phase unbalanced voltage waveform diagram under short-circuit conditions of the unbalanced voltage protection action analysis method for a 10kV parallel capacitor device provided in the third embodiment of the present invention.

[0029] Figure 8 This is a three-phase unbalanced voltage waveform diagram under the non-short-circuited condition of the unbalanced voltage protection action analysis method for a 10kV parallel capacitor device provided in the third embodiment of the present invention. DETAILED DESCRIPTION

[0030] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the accompanying drawings.

[0031] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0032] Example 1

[0033] Reference Figure 1 to Figure 4, which is the first embodiment of the present invention, provides a method for analyzing the unbalanced voltage protection action of a 10kV parallel capacitor device, including: analyzing the tripping condition of the capacitor device; performing on-site test diagnosis and three-phase unbalanced voltage calculation; and performing three-phase unbalanced protection action simulation analysis.

[0034] S1. Analyze the tripping condition of the capacitor device.

[0035] A 35kV substation has carried out comprehensive protection automation transformation work on the entire station. After the on-site work was completed, the operation and maintenance personnel put the 10kV parallel capacitor device into operation and it tripped as soon as it was put into operation. The on-site protection message showed that the three-phase voltage unbalance protection action was taken. The protection recording showed that the three-phase unbalanced voltage value was 18V, and the setting value of the three-phase voltage imbalance of the protection device was 9V and the setting time limit was 0.2s. By retrieving the substation background SOE file, it was shown that the parallel capacitor device had been in normal operation before tripping. In addition, the content of this comprehensive automatic transformation work only targeted the wiring part of the secondary equipment, and did not change the primary part.

[0036] If it is shown that the shunt capacitor device was in normal operation before tripping, and the comprehensive automation transformation work did not change the primary part, an on-site test diagnosis shall be carried out.

[0037] S2. Conduct on-site test diagnosis and three-phase unbalanced voltage calculation.

[0038] S2.1. On-site test diagnosis.

[0039] The model of the 10kV shunt capacitor device is TBB10-450 / 450-AKW. The device contains reactors, lightning arresters, discharge coils and capacitors, of which the capacitors are single star-connected. The wiring diagram of the shunt capacitor device is as follows: Figure 2 shown.

[0040] According to the wiring diagram of the parallel capacitor device, the main reasons that may lead to the "three-phase voltage unbalance trip" fault are as follows: 1) The internal fault of the capacitor causes a large deviation in capacitance; 2) The internal winding of the discharge coil has a fault, such as: winding breakdown, damage, etc.; 3) The reactor has a fault, such as: winding short circuit, open circuit or insulation damage. The above situations may cause a large change in the secondary voltage detected by the discharge coil, and the open triangle voltage exceeds the set value, which in turn triggers the three-phase unbalanced voltage protection action, and finally the capacitor group trips. In addition, damage to the external primary equipment and incorrect wiring may also be the cause of the protection device action.

[0041] Therefore, after the accident occurred, in order to verify the specific cause of the tripping accident, the operation and maintenance personnel first inspected the appearance of the parallel capacitor device after arriving at the scene, and no obvious fault point was found. Then, high-voltage test diagnosis was carried out on each device in the device in turn, and the diagnosis results are shown in Tables 1 to 5.

[0042] Table 1 Capacitance test value (μF)

[0043]

[0044] Table 2 Reactor DC resistance test value (mΩ)

[0045]

[0046] Table 3 Reactor reactance value (mH)

[0047]

[0048] Table 4 Discharge coil ratio

[0049]

[0050] Table 5ABC three-phase overall insulation and withstand voltage test

[0051]

[0052]

[0053] If the cause of "tripping upon startup" is not related to the primary equipment parameters, the three-phase unbalanced voltage calculation should be performed to analyze the cause of the "tripping upon startup".

[0054] According to the test data in Tables 1 to 5, the test data of each device in the parallel capacitor device meets the requirements of relevant national, industry and enterprise standards such as GB 50150-2016 "Electrical Equipment Handover Test Standard for Electrical Installation Engineering", DL / T596-2021 "Preventive Test Procedure for Power Equipment", and Q / CSG1206007-2017 "Power Equipment Maintenance Test Procedure". Therefore, for this tripping accident, it can be preliminarily judged that the cause of the capacitor device "tripping as soon as it is put into operation" has nothing to do with the parameters of the primary equipment.

[0055] S2.2. Calculation of three-phase unbalanced voltage.

[0056] After preliminarily determining that the capacitor tripping was not caused by the primary equipment parameters, in order to further analyze the cause of the three-phase unbalanced voltage action in the capacitor device, the equipment parameters and bus voltage values ​​in the device were used in combination with the three-phase unbalanced voltage protection principle to calculate and verify the three-phase unbalanced voltage value under actual operating conditions.

[0057] The schematic diagram of three-phase unbalanced voltage protection in GB / T11024.3-2019 "Parallel capacitors for AC power systems with nominal voltage above 1000V Part 3: Protection of parallel capacitors and parallel capacitor banks" is as follows Figure 3 shown.

[0058] The capacitor is connected in an ungrounded star shape, and the discharge coil is connected in parallel at both ends of the capacitor. Their secondary sides are connected in an open triangle. When a capacitor fails, its capacitance will also change, causing an unbalanced capacitance of the relevant part of the capacitor bank. When the capacitance is unbalanced, it will cause the neutral point to shift, and an unbalanced voltage will be output through the open triangle. Under ideal conditions (when the bus voltage, three-phase reactance value and capacitance value are completely consistent), the open triangle voltage is 0V. When a capacitor or discharge coil fails, the open triangle voltage will increase, and when it exceeds the set value, it will trigger a protection action. This protection is called open triangle unbalanced voltage protection. It has simple wiring, high sensitivity, and strong phase indication ability. It can clearly point out the fault phase, which helps to quickly locate the fault and handle it, and effectively protect the capacitor bank. However, due to the certain differences in the three-phase bus voltage and the parameters of the capacitor itself, the setting value needs to consider the starting voltage imbalance caused by the three-phase system and equipment parameters to avoid false protection actions. According to the document "Estimation of the Initial Unbalanced Value of Parallel Capacitor Bank Protection", the initial unbalanced voltage UP is equal to 3 times the neutral point offset voltage U0 and can be calculated using the following formula (1):

[0059]

[0060] Among them, U P is the initial unbalanced voltage, U O is the neutral point offset voltage, U A , U B , U C is the 10kV bus three-phase voltage, U A =10.8×10 3 ∠0°V,U B =10.2×10 3 ∠241°V,U C =10.2×10 3 ∠119°V,Y A , Y B , Y C is the admittance value of the three-phase capacitor, Y A =jωC A , Y B =jωC B , Y C =jωC C , three-phase capacitance value C A , C B , CC See Table 1.

[0061] By importing the actual bus voltage value and capacitance admittance value into the calculation U P , the unbalanced voltage value is converted according to the transformation ratio of the discharge coil to determine whether the unbalanced voltage value exceeds the protection setting value. If the unbalanced voltage value does not exceed the protection setting value, the three-phase unbalanced protection action simulation is performed to analyze the cause of the "tripping as soon as it is thrown" situation.

[0062] By importing the actual bus voltage value and capacitance admittance value into the calculation, UP is approximately equal to 188V. According to the transformation ratio of the discharge coil, the unbalanced voltage value is 2.96V, which does not exceed the protection setting value (9V).

[0063] S3. Conduct simulation analysis of three-phase unbalanced protection action.

[0064] Through test diagnosis and theoretical calculation of unbalanced voltage value of each primary device in the capacitor device, no relevant reasons were found. Therefore, a more detailed investigation was conducted on the primary and secondary wiring of the parallel capacitor device. By comprehensively comparing the wiring of the parallel capacitor device on site with the unbalanced voltage protection schematic, it was found that the actual primary wiring part on site did not short-circuit the neutral point of the capacitor and the neutral point of the discharge coil, as shown below Figure 4 shown.

[0065] According to the capacitor wiring diagram, when the neutral point of the capacitor and the neutral point of the discharge coil are not short-circuited, the open triangle voltage detected on the secondary side of the discharge coil is not affected by the imbalance of the three-phase capacitance value, but is related to the primary impedance value of the discharge coil.

[0066] In order to verify whether the tripping accident was caused by the failure to short-circuit the neutral point of the capacitor and the neutral point of the discharge coil, the primary impedance value of the three-phase discharge coil was first measured, and the initial unbalanced voltage was calculated based on the impedance value. The impedance value of the discharge coil is shown in Table 6. The measured impedance value of the discharge coil was converted into an admittance value, and it was substituted into formula (1) together with the bus voltage value for calculation. The initial unbalanced voltage UP was equal to 22V, which was slightly larger than the unbalanced voltage value (18V) in the protection recording. Therefore, it was initially suspected that the tripping accident was caused by the failure to short-circuit the neutral points of the two, resulting in the protection action.

[0067] Table 6 Discharge coil impedance test value (mΩ)

[0068]

[0069] Example 2

[0070] Reference Figure 5, which is the second embodiment of the present invention, is different from the previous embodiment in that it provides a 10kV parallel capacitor device unbalanced voltage protection action analysis system, including: a tripping analysis module 100, a diagnosis module 200 and a simulation analysis module 300.

[0071] The trip analysis module 100 is used to analyze the tripping situation of the capacitor device.

[0072] The diagnosis module 200 is used for performing field test diagnosis and three-phase unbalanced voltage calculation.

[0073] The simulation analysis module 300 is used to perform simulation analysis of three-phase unbalanced protection action.

[0074] If the functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the methods described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk, etc., which can store program codes.

[0075] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute instructions), or in conjunction with such instruction execution systems, devices or apparatuses. For the purposes of this specification, "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in conjunction with such instruction execution systems, devices or apparatuses.

[0076] More specific examples of computer-readable media (a non-exhaustive list) include the following: an electrical connection with one or more wires (electronic device), a portable computer disk case (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be a paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, deciphering or, if necessary, processing in another suitable manner, and then stored in a computer memory.

[0077] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, a plurality of steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0078] Example 3

[0079] Reference Figure 6 to Figure 8 , which is the third embodiment of the present invention, is different from the previous two embodiments in that: it is used to verify and illustrate the technical effects adopted in the present invention, so as to verify the real effect of this method.

[0080] In order to further clarify the cause of the protection tripping, the electromagnetic transient PSCAD software was used to perform simulation modeling analysis under two working conditions: the neutral point of the capacitor and the neutral point of the discharge coil were not short-circuited and short-circuited. Figure 1 Build a parallel capacitor device model and import relevant parameters of reactors, capacitors, discharge coils and other equipment, such as Figure 6 shown.

[0081] The neutral point of the capacitor and the discharge coil is short-circuited.

[0082] In the simulation model, Ea, Eb, and Ec are used to monitor the voltage at both ends of the discharge coil. The three-phase unbalanced voltage (3 times the zero-sequence voltage 3U0) is calculated by the vector of the three-phase voltage. The built-in component Summing / DifferencingJunctions of PSCAD is used to calculate the vector sum of Ea, Eb, and Ec, and the RMS component is used to calculate the effective value of the three-phase unbalanced voltage E0. The final waveform obtained by simulation is as follows: Figure 7shown.

[0083] In the simulation, the closing time of the circuit breaker is set to 0.1s. From the simulation waveform, it can be seen that the unbalanced voltage reaches its peak value due to harmonics or inrush current at 0.1s after the circuit breaker is closed. After 0.2s, the unbalanced voltage stabilizes at about 149V. According to the discharge coil ratio, the three-phase unbalanced voltage 3U0 is converted to 2.34V, which is basically consistent with the theoretical calculated value (2.96V). At the same time, it can be seen from the waveform that after the capacitor is switched on, both the unbalanced voltage value and the fluctuation time do not exceed the setting value and setting time limit of the protection. Therefore, under this operating condition, it will not cause protection action.

[0084] In addition, the impedance of the primary coil of the discharge coil was changed to study whether its imbalance would cause protection action. Under the condition that the capacitor and the neutral point of the discharge coil were short-circuited, the impedance value of the B-phase discharge coil was set to 5000Ω and 6000Ω for simulation calculation, and the converted unbalanced voltage values ​​were 3.5V and 4.35V. The results show that the imbalance of the discharge coil does affect the unbalanced voltage value, but the degree of influence is limited. Under normal wiring and the protection setting value has a certain margin, it will not cause protection action. However, in order to further reduce the impact of the discharge coil on the unbalanced voltage, when selecting the discharge coil, the impedance test of the primary coil should be carried out, and three-phase discharge coils with similar impedance should be selected as much as possible.

[0085] The neutral point of the capacitor and the discharge coil is not short-circuited.

[0086] After short-circuiting the neutral point of the capacitor and the neutral point of the discharge coil in the model, the non-short-circuited working condition is simulated. Without changing other parameter settings, the waveform of the three-phase unbalanced voltage effective value E0 is as follows: Figure 8 shown.

[0087] From the simulation waveform, we can see that the unbalanced voltage value is stable at around 1187V. According to the discharge coil ratio, 3U0 is converted to around 18.7V, which is close to the data monitored by the protection recording (18V) and the actual calculated value (22V).

[0088] Therefore, through simulation analysis of the two working conditions, the protection recording under the actual field working conditions is basically consistent with the simulation calculation results, which verifies the correctness of the above conjecture and determines that the tripping accident was caused by the neutral point of the capacitor and the neutral point of the discharge coil not being short-circuited. At the same time, the simulation also verifies that short-circuiting the neutral point of the capacitor and the neutral point of the discharge coil will not trigger the protection action.

[0089] Through the diagnosis and analysis of the causes of the capacitor device protection action, the following conclusions were drawn:

[0090] The main purpose of three-phase unbalanced voltage protection is to be able to promptly detect faults in equipment such as capacitors, reactors, and discharge coils. When the protection is activated, the relevant equipment in the device should first be tested and diagnosed.

[0091] The present invention finally determined through on-site comparison and simulation calculation that the protection misoperation was caused by incorrect on-site primary wiring of the capacitor device. When the discharge coil and the neutral point of the capacitor are not short-circuited, the zero-sequence voltage mainly reflects the imbalance of the impedance of the primary winding of the discharge coil, and the operating status of the capacitor cannot be monitored. Only when the discharge coil and the neutral point of the capacitor are short-circuited, because the impedance value of the capacitor is much smaller than that of the discharge coil, after being connected in parallel with the discharge coil, the zero-sequence voltage mainly reflects the imbalance of the capacitor capacitance. Therefore, in order to be able to detect internal defects of the capacitor equipment in advance, it is necessary to short-circuit the neutral points of the two.

[0092] Even under the condition that the discharge coil and the neutral point of the capacitor are short-circuited, the greater the impedance imbalance of the discharge coil, the greater the zero-sequence voltage value will be. Therefore, when selecting the discharge coil, in addition to conducting tests such as transformation ratio and volt-ampere characteristics, three-phase discharge coils with small impedance deviation should be selected as much as possible to reduce the initial unbalanced voltage value of the capacitor device.

[0093] In view of this tripping accident, the equipment still tripped as soon as it was put into operation, even though the primary wiring of the capacitor was not changed and the secondary wiring was correct during the comprehensive reconstruction work. Therefore, when conducting fault analysis and diagnosis, the primary equipment should be analyzed one by one from the outside to the inside to ensure comprehensiveness.

[0094] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. 10kV shunt capacitor device unbalanced voltage protection action analysis method, characterized by: include, Analyze capacitor device tripping conditions; Conduct on-site test diagnosis and three-phase unbalanced voltage calculation; Conduct simulation analysis of three-phase unbalanced protection action.

2. The 10kV parallel capacitor device unbalanced voltage protection action analysis method according to claim 1, characterized in that: The analysis of the capacitor device tripping situation includes the situation where the 10kV parallel capacitor device trips as soon as it is put into operation. By retrieving the substation background SOE file, the operating status of the parallel capacitor device before tripping is checked. If it is shown that the parallel capacitor device has been in normal operating status before tripping, it is checked whether the comprehensive automation transformation work content has been changed for the primary part. If not, on-site test diagnosis is carried out.

3. The 10kV parallel capacitor device unbalanced voltage protection action analysis method according to claim 2, characterized in that: The on-site test diagnosis includes analysis based on the wiring diagram of the parallel capacitor device. The causes of the three-phase voltage imbalance tripping fault include internal faults of the capacitor causing large capacitance deviation, internal winding faults of the discharge coil, and reactor faults. If the tripping as soon as the power is turned on is not caused by internal faults in the capacitor that result in large capacitance deviation, faults in the internal windings of the discharge coil, or faults in the reactor, the three-phase unbalanced voltage calculation is performed to analyze the cause of the tripping as soon as the power is turned on.

4. The method for analyzing the unbalanced voltage protection action of a 10kV parallel capacitor device according to claim 3, characterized in that: The three-phase unbalanced voltage calculation includes analyzing the cause of the three-phase unbalanced voltage action of the capacitor device after preliminarily determining that the capacitor tripping is not caused by the primary equipment parameters, and calculating and verifying the three-phase unbalanced voltage value under the actual operating conditions by using the equipment parameters in the device, the bus voltage value and the three-phase unbalanced voltage protection principle. The initial unbalanced voltage is expressed as: Among them, U P is the initial unbalanced voltage, U O is the neutral point offset voltage, U A , U B , U C is the 10kV bus three-phase voltage, Y A , Y B , Y C is the admittance value of the three-phase capacitance.

5. The method for analyzing the unbalanced voltage protection action of a 10kV parallel capacitor device according to claim 4, characterized in that: The three-phase unbalanced voltage calculation also includes the step of importing the actual bus voltage value and the capacitance admittance value into the calculation U P , the unbalanced voltage value is converted according to the transformation ratio of the discharge coil to determine whether the unbalanced voltage value exceeds the protection setting value. If the unbalanced voltage value does not exceed the protection setting value, the three-phase unbalanced protection action simulation is performed to analyze the cause of the tripping situation as soon as it is thrown.

6. The method for analyzing the unbalanced voltage protection action of a 10kV parallel capacitor device according to claim 5, characterized in that: The simulation analysis of the three-phase unbalanced protection action includes: if the field test diagnosis and the three-phase unbalanced voltage calculation do not find the cause of the tripping situation, then check whether the neutral point of the capacitor and the neutral point of the discharge coil are short-circuited, measure the primary impedance value of the three-phase discharge coil, and calculate the starting unbalanced voltage according to the impedance value, convert the measured impedance value of the discharge coil into an admittance value, and bring it into the starting unbalanced voltage formula together with the bus voltage value for calculation to obtain the starting unbalanced voltage U P , determine the initial unbalanced voltage U P The relationship between the unbalanced voltage value and the protection recording wave is that if the initial unbalanced voltage U P If the voltage is greater than the unbalanced voltage value in the protection recording, the tripping accident is caused by the protection action due to the failure to short-circuit the neutral points of the two.

7. The method for analyzing the unbalanced voltage protection action of a 10kV parallel capacitor device according to claim 6, characterized in that: The three-phase unbalanced protection action simulation analysis also includes clarifying the cause of the protection tripping, and using electromagnetic transient PSCAD software to perform simulation modeling analysis under two working conditions: the neutral point of the capacitor and the neutral point of the discharge coil are not short-circuited and short-circuited.

8. A system using the 10kV parallel capacitor device unbalanced voltage protection action analysis method as claimed in any one of claims 1 to 7, characterized in that: It comprises a trip analysis module (100), a diagnosis module (200) and a simulation analysis module (300); The tripping analysis module (100) is used to analyze the tripping condition of the capacitor device; The diagnostic module (200) is used to perform on-site test diagnosis and three-phase unbalanced voltage calculation; The simulation analysis module (300) is used to perform simulation analysis of three-phase unbalanced protection action.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of the 10 kV parallel capacitor device unbalanced voltage protection operation analysis method according to any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method for analyzing the operation of unbalanced voltage protection of a 10 kV parallel capacitor device according to any one of claims 1 to 7 are implemented.

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