阅读说明：本技术 一种小电流接地系统接地故障快速选线方法 (Method for quickly selecting line of ground fault of low-current grounding system ) 是由 陈武 刘滔 陈绍忠 何述 余兰 李懿山 彭永顺 于 2019-10-16 设计创作，主要内容包括：本发明公开了一种小电流接地系统接地故障快速选线方法,采集小电流接地系统的三相电压和零序电压；对三相电压和零序电压进行逻辑运算以判断三相电压和零序电压是否异常；如果异常启动第一条线路接地保护拉路,控制出线断路器分闸,判断三相电压和零序电压是否异常,如果异常且第一条线路出线断路器在分位,则控制第一条线路出线断路器合闸,启动第n条线路接地保护拉路,过程和第一条线路接地保护执行动作相同,只是设置的延时出口时间滞后于前一条线路；其中n为正整数且2≤n≤N。本发明在馈线保护装置不改变原有功能的基础上,扩展接地故障时保护装置整组快速拉线选线功能；该方法无需额外的选线装置,成本低,且易于实现。(the invention discloses a method for quickly selecting a line of a ground fault of a small current grounding system, which comprises the steps of collecting three-phase voltage and zero-sequence voltage of the small current grounding system; performing logical operation on the three-phase voltage and the zero-sequence voltage to judge whether the three-phase voltage and the zero-sequence voltage are abnormal or not; if the first line grounding protection pull circuit is started abnormally, the outgoing line breaker is controlled to be switched off, whether the three-phase voltage and the zero-sequence voltage are abnormal or not is judged, if the first line grounding protection pull circuit is abnormal and the first line outgoing line breaker is in a switching-off position, the first line outgoing line breaker is controlled to be switched on, the nth line grounding protection pull circuit is started, the process is the same as the first line grounding protection execution action, and only the set delay outlet time lags behind the previous line; wherein N is a positive integer and N is more than or equal to 2 and less than or equal to N. On the basis that the feeder line protection device does not change the original function, the whole group of quick wire pulling and wire selecting functions of the protection device during the ground fault are expanded; the method does not need an additional line selection device, has low cost and is easy to realize.)

1. A method for quickly selecting a line of a ground fault of a low-current grounding system is characterized by comprising the following steps:

step S1, collecting three-phase voltage and zero-sequence voltage of the small current grounding system;

Step S2, performing logical operation on the three-phase voltage and the zero-sequence voltage to judge whether the three-phase voltage and the zero-sequence voltage are abnormal;

step S3, if the first line grounding protection pull circuit is started abnormally, the outgoing line breaker is controlled to open, and step S4 is executed; otherwise, the flow is ended;

step S4, executing step S2 to judge whether the three-phase voltage and the zero sequence voltage are abnormal, if the three-phase voltage and the zero sequence voltage are abnormal and the first line outgoing breaker is in a position separation state, controlling the first line outgoing breaker to be switched on, and executing step S5; otherwise, the flow is ended;

step S5, starting the nth line ground protection pull: after the n-1 line outgoing line breaker is switched on, the n line outgoing line breaker is controlled to be switched off in a delayed mode through the n line protection device t 2; step S2 is executed to judge whether the three-phase voltage and the zero sequence voltage are abnormal, if the three-phase voltage and the zero sequence voltage are abnormal and the n-1 line outgoing line breaker is in the off position, the n line outgoing line breaker is controlled to be switched on, and step S5 is executed repeatedly until all the line grounding protection in the low-current grounding system is pulled; otherwise, the flow is ended; wherein N is a positive integer and is more than or equal to 2 and less than or equal to N, and N is a main circuit of the low-current grounding system.

2. the method according to claim 1, wherein the step S2 specifically comprises: and if the two-phase voltage in the three-phase voltage is greater than or equal to the threshold value, the one-phase voltage is less than or equal to the threshold value, and the zero-sequence voltage is greater than or equal to the threshold value, judging that the three-phase voltage is abnormal.

3. The method according to claim 1, wherein the starting of the first line ground protection pull-out in step S3 specifically comprises: and the circuit breaker protection device for controlling the first line opens the positive power supply at the outlet, controls the main control switch to be closed, and controls the circuit breaker for controlling the first line outlet to be opened through the t1 delay outlet.

4. The method for quickly selecting the line of the ground fault of the small-current grounding system as claimed in claim 3, wherein the value of t1 is 0-999999 ms.

5. The method for quickly selecting the ground fault line of the small-current grounding system as claimed in claim 3, wherein the value of t1 is 0 ms.

6. The method according to claim 1, wherein the step S5 of starting the nth line ground protection pull-out specifically comprises: and the circuit breaker protection device for controlling the nth line opens the positive power supply at the outlet, controls the main control switch to be closed, and controls the outlet circuit breaker of the nth line to open through the t2 delay outlet.

7. the method for quickly selecting the line with the ground fault of the small-current grounding system as claimed in claim 6, wherein the value of t2 is greater than the n-1 st line execution time.

8. the method for rapidly selecting the ground fault line of the low-current grounding system according to any one of claims 1 to 7, wherein after the first line outgoing breaker is closed in step S4, t-time latch start is started.

9. The method as claimed in claim 8, wherein the t-time latch is larger than the sum of the execution times of all lines of the low-current grounding system.

10. The method for quickly selecting the line of the ground fault of the small-current grounding system according to claim 9, wherein the step S2 adopts a CPU or an FPGA to realize the logic operation of the three-phase voltage and the zero-sequence voltage.

Technical Field

The invention relates to the technical field of power system ground faults, in particular to a method for quickly selecting a line of a ground fault of a low-current ground system.

background

The small-current grounding system is a power system with a neutral point not grounded, grounded through an arc suppression coil or grounded through a high resistance, and most domestic power grids of 66kV and below adopt the grounding mode. Its main disadvantage is that it is not possible to quickly identify on which line the problem is when a single-phase earth fault occurs. Since the rise in the phase voltage caused by such a fault poses a great threat to the insulation performance of the system, the faulty line must be quickly detected and removed.

according to the requirements of scheduling procedures: when a point-to-ground condition occurs in an ungrounded system, the system must run for no more than two hours with a point-to-ground. In a power grid with a neutral point not grounded or grounded through an arc suppression coil, when a ground fault is found, when one phase is completely grounded, the voltage of the grounded phase is zero, and the other two phases are raised to be the line voltage. When not fully grounded, the voltage of the grounded phase decreases, while the other phase voltages increase. If the voltage is continuously grounded, the voltage indicated value is unchanged; such as intermittent grounding, the voltage indication increases, decreases, and sometimes is normal. When the grounding fault is found, the fault point is quickly searched and eliminated when the grounding fault operates. If the fault can not be removed immediately, the fault can be enlarged by breaking down the weak insulation part of the power system, and it is very important to find out the grounding fault line quickly and accurately.

The existing small-current ground fault processing method mainly comprises the following steps:

1. A manual pulling method, namely, a line which is likely to have a ground fault is judged through manual experience, and the line is manually disconnected; the method can break the lines which are not grounded, and the analysis and judgment time is long. The method not only influences the judgment, the patrol and the power restoration of the fault line, but also can cause the danger of electric shock of people and livestock if the treatment is not timely, and simultaneously greatly increases the workload of dispatching on-duty personnel and influences the reliability and the high-quality service of power supply.

2. The device line selection method has two modes for realizing small grounding line selection in an unattended substation, wherein one mode is that a protection device has a line selection function, and the other mode is a small grounding line selection device which is installed in a centralized manner. The method is mainly realized by using the line selection function of the device, but the method for performing small grounding line selection by using the line selection function of the protection device is inaccurate and cannot faithfully reflect a real grounding line; the centralized line selection technology needs to add a centralized small-current grounding line selection device, and the cost is high.

3. The main station line selection method and the fault indicator method are not mature, are difficult to realize, do not have the capability of popularization and application in the current power distribution automation development stage, and have the defects of inaccurate line selection and poor reliability.

disclosure of Invention

The invention provides a method for quickly selecting a line of a ground fault of a low-current grounding system, which expands the whole group of quick wire pulling and line selecting functions of a protection device during the ground fault on the basis that a feeder protection device does not change the original function; the method does not need an additional line selection device, has low cost and is easy to realize.

the invention is realized by the following technical scheme:

a method for quickly selecting a line of a ground fault of a low-current grounding system comprises the following steps:

Step S1, collecting three-phase voltage and zero-sequence voltage of the small current grounding system;

Step S2, performing logical operation on the three-phase voltage and the zero-sequence voltage to judge whether the three-phase voltage and the zero-sequence voltage are abnormal;

Step S3, if the first line grounding protection pull circuit is started abnormally, the outgoing line breaker is controlled to open, and step S4 is executed; otherwise, the flow is ended;

step S4, executing step S2 to judge whether the three-phase voltage and the zero sequence voltage are abnormal, if the three-phase voltage and the zero sequence voltage are abnormal and the first line outgoing breaker is in a position separation state, controlling the first line outgoing breaker to be switched on, and executing step S5; otherwise, the flow is ended;

Step S5, starting the nth line ground protection pull: after the n-1 line outgoing line breaker is switched on, the n line outgoing line breaker is controlled to be switched off in a delayed mode through the n line protection device t 2; step S2 is executed to judge whether the three-phase voltage and the zero sequence voltage are abnormal, if the three-phase voltage and the zero sequence voltage are abnormal and the n-1 line outgoing line breaker is in the off position, the n line outgoing line breaker is controlled to be switched on, and step S5 is executed repeatedly until all the line grounding protection in the low-current grounding system is pulled; otherwise, the flow is ended; wherein N is a positive integer and is more than or equal to 2 and less than or equal to N, and N is a main circuit of the low-current grounding system.

preferably, in step S2, specifically, the method includes: and if the two-phase voltage in the three-phase voltage is greater than or equal to the threshold value, the one-phase voltage is less than or equal to the threshold value, and the zero-sequence voltage is greater than or equal to the threshold value, judging that the three-phase voltage is abnormal.

preferably, the starting of the first line ground protection pull-out in step S3 specifically includes: and the circuit breaker protection device for controlling the first line opens the positive power supply at the outlet, controls the main control switch to be closed, and controls the circuit breaker for controlling the first line outlet to be opened through the t1 delay outlet.

Preferably, the value of t1 is 0-999999 ms.

Preferably, the value of t1 is 0 ms.

Preferably, the step S5 of starting the nth line ground protection pull specifically includes: and the circuit breaker protection device for controlling the nth line opens the positive power supply at the outlet, controls the main control switch to be closed, and controls the outlet circuit breaker of the nth line to open through the t2 delay outlet.

Preferably, the value of t2 is greater than the n-1 line execution time.

preferably, after the first line outgoing breaker is closed in step S4, the latch is activated for time t.

Preferably, the t-time latch should be larger than the sum of the execution times of all lines of the low-current grounding system.

Preferably, in the step S2, the CPU or the FPGA is used to implement the logic operation of the three-phase voltage and the zero-sequence voltage.

The invention has the following advantages and beneficial effects:

1. the circuit breaker protection device and the protection circuit pulling method are optimally combined, the protection circuit pulling of all circuits in the system can be quickly realized, and the response time can reach ms level; the invention realizes the full protection judgment processing of the earth fault, does not need manual intervention, has simple and reliable principle and accurate, efficient and quick judgment;

2. When the circuit breaker is used for processing faults, the time for disconnecting the circuit breaker is short, and the defect of disconnecting the non-grounded circuit is overcome by fast switching, so that normal power supply (equivalent to reclosing) of a normal circuit user is not influenced; the invention is simple and easy to realize, can realize the function only by upgrading the chip of the protection device, does not need to transform hardware and a loop, and has low transformation cost and low realization difficulty.

3. The invention is totally analyzed and processed by the substation end, and the result is uploaded through remote signaling to schedule the main station end, thereby reducing the workload of the scheduling and monitoring personnel of the main station end. And the circuit of looped netowrk power supply can realize earth fault fast investigation through setting up same protection definite value.

drawings

The accompanying drawings, which are included to provide a further understanding of the embodiments of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principles of the invention. In the drawings:

FIG. 1 is a flow chart of the method of the present invention.

fig. 2 is a logic block diagram of the first line ground protection pull circuit of the present invention.

FIG. 3 is a logic diagram of a second line protection pull according to the present invention.

Detailed Description

hereinafter, the term "comprising" or "may include" used in various embodiments of the present invention indicates the presence of the invented function, operation or element, and does not limit the addition of one or more functions, operations or elements. Furthermore, as used in various embodiments of the present invention, the terms "comprises," "comprising," "includes," "including," "has," "having" and their derivatives are intended to mean that the specified features, numbers, steps, operations, elements, components, or combinations of the foregoing, are only meant to indicate that a particular feature, number, step, operation, element, component, or combination of the foregoing, and should not be construed as first excluding the existence of, or adding to the possibility of, one or more other features, numbers, steps, operations, elements, components, or combinations of the foregoing.

In various embodiments of the invention, the expression "or" at least one of a or/and B "includes any or all combinations of the words listed simultaneously. For example, the expression "a or B" or "at least one of a or/and B" may include a, may include B, or may include both a and B.

Expressions (such as "first", "second", and the like) used in various embodiments of the present invention may modify various constituent elements in various embodiments, but may not limit the respective constituent elements. For example, the above description does not limit the order and/or importance of the elements described. The foregoing description is for the purpose of distinguishing one element from another. For example, the first user device and the second user device indicate different user devices, although both are user devices. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of various embodiments of the present invention.

it should be noted that: if it is described that one constituent element is "connected" to another constituent element, the first constituent element may be directly connected to the second constituent element, and a third constituent element may be "connected" between the first constituent element and the second constituent element. In contrast, when one constituent element is "directly connected" to another constituent element, it is understood that there is no third constituent element between the first constituent element and the second constituent element.

The terminology used in the various embodiments of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the various embodiments of the invention. As used herein, the singular forms are intended to include the plural forms as well, unless the context clearly indicates otherwise. Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which various embodiments of the present invention belong. The terms (such as those defined in commonly used dictionaries) should be interpreted as having a meaning that is consistent with their contextual meaning in the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein in various embodiments of the present invention.

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to examples and accompanying drawings, and the exemplary embodiments and descriptions thereof are only used for explaining the present invention and are not meant to limit the present invention.