阅读说明：本技术 一种并联电容器保护方法 (Parallel capacitor protection method ) 是由 陈军潮 董捷 于 2019-10-31 设计创作，主要内容包括：本发明涉及了一种并联电容器保护方法，通过数据采集模块分别采集每相的放电线圈的二次侧电压瞬时值、对应相的电流互感器二次侧电流瞬时值，得到对应相的电容器的容抗值；监控主机在三相并联电容器成套装置初次启用时，得到容抗初始值；在运行过程中，得到容抗运行值；两个对应的容抗值进行比对，偏差超过阀值，监控主机即判定发生故障，断开三相母线与三相并联电容器成套装置的连接，即实现对三相并联电容器的保护。本发明的一种并联电容器保护方法，可判断并联电容器成套装置的健康状态，一旦有个别电容器单元损坏，在故障初期就能及时有效发现这种小故障，切除并更换故障电容器所在的并联电容器成套装置，防止故障扩大造成更严重的后果。(The invention relates to a parallel capacitor protection method, which comprises the steps of respectively collecting a secondary side voltage instantaneous value of a discharge coil of each phase and a secondary side current instantaneous value of a current transformer of a corresponding phase through a data collection module to obtain a capacitive reactance value of a capacitor of the corresponding phase; when the three-phase parallel capacitor complete device is started for the first time, the monitoring host obtains a capacitive reactance initial value; in the operation process, obtaining a capacitive reactance operation value; and comparing the two corresponding capacitive reactance values, judging that a fault occurs if the deviation exceeds a threshold value, and disconnecting the three-phase bus from the three-phase parallel capacitor complete device to protect the three-phase parallel capacitor. The parallel capacitor protection method can judge the health state of the parallel capacitor complete equipment, once individual capacitor units are damaged, the small fault can be effectively found in time at the early stage of the fault, the parallel capacitor complete equipment where the fault capacitor is located is cut off and replaced, and the more serious consequences caused by the expansion of the fault are prevented.)

1. A parallel capacitor protection method includes a three-phase parallel capacitor complete device connected with a three-phase bus; the method is characterized in that: the system also comprises a data acquisition module, a monitoring host and a switch arranged on the three-phase bus; the two ends of each phase of capacitor in the three-phase parallel capacitor assembly are connected with a discharge coil in parallel; each phase of bus of the three-phase bus is provided with a current transformer, and the data acquisition module is respectively connected with the secondary sides of the three-phase discharge coils in parallel and respectively connected with the secondary sides of the three-phase current transformers in series; the data acquisition module is in data transmission connection with the monitoring host, and the switch is in signal connection with the monitoring host; the specific protection method comprises the following steps:

respectively acquiring a secondary side voltage instantaneous value of a discharge coil of each phase and a secondary side current instantaneous value of a current transformer of each phase through a data acquisition module to obtain a capacitive reactance value of a capacitor of the corresponding phase;

when the three-phase parallel capacitor complete device is started for the first time, the monitoring host obtains capacitance reactance initial values corresponding to the three-phase capacitors through the step one;

thirdly, monitoring in real time by the monitoring host in the operation process of the three-phase parallel capacitor complete device, and obtaining the capacitive reactance operation values corresponding to the three-phase capacitors through the first step;

comparing the initial value of the capacitive reactance of the capacitor in the step two with the corresponding operational value of the capacitive reactance obtained in the step three, wherein the deviation of the two values exceeds a preset threshold value, judging that a fault occurs by the monitoring host, and sending a trip signal;

and fifthly, the switch receives a trip signal sent by the monitoring host, and the connection between the three-phase parallel capacitor complete device and the three-phase bus is disconnected, so that the protection of the three-phase parallel capacitor is realized.

2. A parallel capacitor protection method according to claim 1, characterized in that: the switch includes a disconnector and a circuit breaker.

3. A parallel capacitor protection method according to claim 1, characterized in that: the method for obtaining the capacitive reactance value in the first step specifically comprises the following steps:

a. converting the acquired voltage instantaneous value and current instantaneous value into digital quantity through A/D conversion to obtain a secondary side voltage value of a discharge coil of the digital quantity and a secondary side current value of a current transformer;

b. decomposing secondary side voltage values of the three discharge coils into fundamental wave voltage values and harmonic wave voltage values through fast Fourier transform; performing fast Fourier transform on secondary side current values of the three current transformers to decompose the secondary side current values into fundamental current values and harmonic current values;

c. multiplying the secondary side fundamental wave voltage value of the discharge coil by the transformation ratio of the discharge coil to obtain the terminal voltage value of a capacitor corresponding to the discharge coil; multiplying the secondary side fundamental wave current value of the current transformer by the transformation ratio of the current transformer to obtain the current value of a capacitor corresponding to the current transformer;

d. and dividing the terminal voltage value of the capacitor by the current value of the capacitor to obtain the capacitive reactance value of the capacitor.

Technical Field

The invention relates to the field of parallel capacitors, in particular to a parallel capacitor protection method.

Background

The parallel capacitor is one of the most important reactive compensation equipment, is widely applied to a power system, and most of the substations are provided with a parallel capacitor complete device at present.

However, as nonlinear electricity loads (such as electric vehicle charging stations, electric motorcycle chargers, chemical plant electrolyzers, frequency converters and the like) are greatly increased, harmonic pollution of an electric power system is increased day by day and is affected by the harmonic pollution, and accidents such as fire and explosion of a parallel capacitor frequently occur; therefore, it is necessary to invent a method for preventing the spread of the accident.

Disclosure of Invention

In order to solve the technical problems, the invention provides a parallel capacitor protection method, which is used for judging the health state of a parallel capacitor complete device, and once individual capacitor units are damaged, the small fault can be timely and effectively found at the early stage of the fault, the parallel capacitor complete device where the fault capacitor is located is cut off, and the more serious consequences caused by the expansion of the fault are prevented.

The technical scheme adopted by the invention for solving the technical problems is as follows: a parallel capacitor protection method comprises a three-phase parallel capacitor complete device connected with a three-phase bus; the system also comprises a data acquisition module, a monitoring host and a switch arranged on the three-phase bus; the two ends of each phase of capacitor in the three-phase parallel capacitor assembly are connected with a discharge coil in parallel; each phase of bus of the three-phase bus is provided with a current transformer, and the data acquisition module is respectively connected with the secondary sides of the three-phase discharge coils in parallel and respectively connected with the secondary sides of the three-phase current transformers in series; the data acquisition module is in data transmission connection with the monitoring host, and the switch is in signal connection with the monitoring host; the specific protection method comprises the following steps:

respectively acquiring a secondary side voltage instantaneous value of a discharge coil of each phase and a secondary side current instantaneous value of a current transformer of each phase through a data acquisition module to obtain a capacitive reactance value of a capacitor of the corresponding phase;

when the three-phase parallel capacitor complete device is started for the first time, the monitoring host obtains capacitance reactance initial values corresponding to the three-phase capacitors through the step one;

thirdly, monitoring in real time by the monitoring host in the operation process of the three-phase parallel capacitor complete device, and obtaining the capacitive reactance operation values corresponding to the three-phase capacitors through the first step;

comparing the initial value of the capacitive reactance of the capacitor in the step two with the corresponding operational value of the capacitive reactance obtained in the step three, wherein the deviation of the two values exceeds a preset threshold value, judging that a fault occurs by the monitoring host, and sending a trip signal;

and fifthly, the switch receives a trip signal sent by the monitoring host, and the connection between the three-phase parallel capacitor complete device and the three-phase bus is disconnected, so that the protection of the three-phase parallel capacitor is realized.

Further, the switch comprises a disconnecting switch and a circuit breaker.

Further, the method for obtaining the capacitive reactance value in the step one specifically comprises the following steps:

a. converting the acquired voltage instantaneous value and current instantaneous value into digital quantity through A/D conversion to obtain a secondary side voltage value of a discharge coil of the digital quantity and a secondary side current value of a current transformer;

b. decomposing secondary side voltage values of the three discharge coils into fundamental wave voltage values and harmonic wave voltage values through fast Fourier transform; performing fast Fourier transform on secondary side current values of the three current transformers to decompose the secondary side current values into fundamental current values and harmonic current values;

c. multiplying the secondary side fundamental wave voltage value of the discharge coil by the transformation ratio of the discharge coil to obtain the terminal voltage value of a capacitor corresponding to the discharge coil; multiplying the secondary side fundamental wave current value of the current transformer by the transformation ratio of the current transformer to obtain the current value of a capacitor corresponding to the current transformer;

d. and dividing the terminal voltage value of the capacitor by the current value of the capacitor to obtain the capacitive reactance value of the capacitor.

The invention has the advantages that: the parallel capacitor protection method can judge the health state of the parallel capacitor complete equipment, once individual capacitor units are damaged, the small fault can be effectively found in time at the early stage of the fault, the parallel capacitor complete equipment where the fault capacitor is located is cut off and replaced, and the more serious consequences caused by the expansion of the fault are prevented.

Drawings

Fig. 1 is a schematic circuit diagram illustrating a parallel capacitor protection method according to an embodiment.

Detailed Description

For the purpose of enhancing the understanding of the present invention, the present invention will be described in further detail with reference to the accompanying drawings and examples, which are provided for the purpose of illustration only and are not intended to limit the scope of the present invention.