Method for replacing 10kV feed-out line protection device without power cut by depending on section switch

Abstract

The invention discloses a method for replacing a 10kV feed-out line protection device without power cut by depending on a section switch, which comprises the following steps of: switching on the 10kV section switch to change the operation mode of a main transformer in a station, and additionally arranging temporary overcurrent protection at the 10kV section switch, namely, calculating a temporary overcurrent protection constant value by adopting a new setting calculation principle; the main principle is that a temporary overcurrent protection constant value of an overcurrent I section is set according to 1.2 times of the maximum quick-break current in a line of a bus where 10kV replacement protection is located; the temporary overcurrent protection constant value of the overcurrent II section is set according to the maximum load current in the secondary daytime of the main transformer avoiding operation; the calculated fixed value IopI is installed in a temporary overcurrent protection device and used for replacing 10kV feed-out line protection originally, when a fault occurs on the line side, a 10kV feed-out line switch is tripped off through the temporary overcurrent protection device installed at a section switch, the fault is isolated, and therefore feed-out line protection is replaced without power failure, power failure caused to important users and resident loads is avoided, and the service life of the power supply is prolonged. Therefore, the power supply reliability of the power system is greatly improved.

Description

Technical Field

[0001] The invention belongs to the field of power system and automation thereof, and in particular relates to a method for replacing a 10kV feeder line protection device without power outage by relying on a section switch. Background Art

[0002] As the service life of power grid secondary equipment increases, the electronic components of relay protection devices gradually age, often causing equipment defects. If they are not modified in time, it will cause power grid operation risks. According to the provisions of 6.3.3.5.1 of the Equipment Plan

[2020] No. 72 document "Principles for Power Grid Production Technology Transformation of State Grid Corporation of China" issued by the Equipment Department of State Grid Corporation, "Protection and safety devices that have been in operation for 15 years or more or have serious design and manufacturing defects should be replaced." In the process of replacing traditional 10kV line protection, the line must be shut down for a period of time, which poses a huge threat to the safe operation of some important power loads. In order to meet the requirements of power supply reliability, avoid large-scale power outages and affect the power supply of important users, it is difficult to shut down some radial power supply lines (loads cannot be transferred) and power lines of important users. In this context, explore the transformation method of secondary equipment under the state of 10kV line power outage, strive to complete the replacement and acceptance of 10kV line protection without power outage, and control the operation risk within a controllable range. At the same time, formulating a set of practical work plans to reduce work risks, improve work efficiency and reduce work costs is of great significance to the safe operation of the power grid. Summary of the invention

[0003] The purpose of the present invention is to solve the problem in the prior art that as the operating years of power grid secondary equipment increase, the electronic components of the relay protection device gradually age, often causing equipment defects, which will cause power grid operation risks if not promptly modified.

[0004] In order to solve the above problems, the present invention provides a method for replacing a 10kV feeder line protection device without power outage by relying on a section switch, comprising the following steps:

[0005] S1: Before replacing the 10kV line protection device without power outage, close the 10kV section switch, and the operation mode of the main transformer in the station is changed to one main transformer with two busbars. The main transformer of the bus where the protection is replaced is switched to hot standby state, and the other main transformer is in operation, and the standby automatic switch is disabled;

[0006] S2: Temporary overcurrent protection is installed at the 10kV section switch, and the protection AC sampling values ​​(current and voltage values) are taken from the current and voltage transformers at the 10kV section switch;

[0007] Connecting the tripping circuit to the 10kV feeder switch that needs to be replaced not only realizes the convenience of collecting current and voltage values ​​for temporary overcurrent protection, but also ensures that only the corresponding 10kV feeder is tripped when the fault trips, minimizing the scope of fault power outage and satisfying the selectivity of relay protection professionals;

[0008] S3: The new setting calculation principle is used to calculate the temporary overcurrent protection setting value. The main principles are:

[0009] The temporary overcurrent protection setting value of overcurrent stage I is set at 1.2 times the maximum quick-break current of the bus line where the 10kV replacement protection is located;

[0010] The setting value of temporary overcurrent protection of overcurrent stage II is set according to the maximum load current of the main secondary of the main transformer during the day;

[0011] The protection action time is 0.2s later than the normal line protection action time. In this way, when other lines fail, although the temporary overcurrent protection will also collect the fault current, the protection of the corresponding line will be tripped first due to the time difference, avoiding the temporary overcurrent protection from erroneous action, causing the replacement protection line to be shut down by mistake. At the same time, it needs to be shorter than the main transformer backup protection time to avoid the corresponding temporary overcurrent protection from refusing to operate when the modified line fails, causing the main transformer backup protection to operate and expand the power outage range;

[0012] S3-1: Overcurrent I stage is the current quick-break protection, which is set according to the maximum short-circuit current of the three-phase busbar on the other side of the largest transformer of this line. The specific formula is as follows:

[0013]

[0014] I=1.2I opI

[0015] In the formula, I B Indicates the reference current on the 10kV side, Z max Indicates the maximum per unit value of 10kV busbar, Z K Indicates the maximum transformer impedance per unit value of this line, Z XL Indicates the per unit value of line impedance from line outlet to maximum transformer, K K Represents the reliability coefficient, the reliability coefficient ≥ 1.5. At the same time, when the time limit setting needs to be coordinated with the time of the lower-level opening and closing station, a time difference Δt can be added, and the value range of Δt is 0.2~0.3s;

[0016] S3-2: Overcurrent II stage is time-limited overcurrent protection, which is set according to the maximum daytime load current of the main secondary transformer in bypass operation. The specific formula is as follows:

[0017] I opII ≥K K I fmax

[0018] K k ≥1.3

[0019] In the formula, I fmax Indicates the maximum current value of the main secondary transformer during the day on this side;

[0020] S3-3: Check the sensitivity of overcurrent protection to the end of this line;

[0021]

[0022] In the formula, Indicates the short-circuit current when the end of this line is short-circuited;

[0023] S4: Set the constant value I opI It is installed in the temporary overcurrent protection device to replace the original 10kV feeder line protection. When a fault occurs on the line side, the temporary protection will trip the section switch to isolate the fault, so that the feeder line protection can be replaced without power outage.

[0024] In a preferred manner, in step S2, the tripping circuit is connected to the 10kV feeder line switch that needs to be replaced for protection in order to achieve the convenience of collecting current and voltage values ​​for temporary overcurrent protection, while ensuring that only the corresponding 10kV feeder line is tripped when a fault trips, minimizing the scope of fault power outage and satisfying the selectivity of relay protection professionals.

[0025] In the preferred mode, the deactivation of the standby automatic transfer mode means that the premise of replacing the protection device without power outage is to convert one main transformer into hot standby, which does not meet the charging conditions of the segmented standby automatic transfer mode. At the same time, in this mode, the main transformer standby automatic transfer mode cannot be enabled due to the tripping of the segmented switch, so the standby automatic transfer device needs to be deactivated.

[0026] In a preferred embodiment, the sensitivity of the line end refers to whether the set value calculated by the setting can satisfy the normal operation of the protection device when a fault occurs at the line end, and whether it responds to the fault condition at the line end.

[0027] Beneficial effects of the present invention: The research results of this project have significant economic value. First, by designing and working processes for replacing 10kV line protection without power outage, the time and scope of power outages caused by line protection replacement can be greatly reduced, thereby reducing potential economic losses. Secondly, by optimizing the design and work process, work efficiency and safety can be improved, and operation and maintenance costs and manpower input can be reduced. In addition, the research results can also be extended to other types of power line protection replacement work, with broad application prospects and potential economic benefits. At the same time, the research results of this project have significant social benefits. First, the design and work process for replacing 10kV line protection without power outage can greatly improve the reliability and safety of the power system, thereby ensuring the people's production and living electricity needs. Secondly, the research results can also promote technological innovation and progress in the power industry, improve the overall level of the power industry, and contribute to the country's economic development. In addition, replacing 10kV line protection without power outage can also reduce the impact on the environment, which meets the requirements of the national sustainable development strategy. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 A schematic diagram of a temporary protection wiring method for adding a temporary protection to the section switch of the present invention;

[0029] Figure 2 This is a schematic diagram of the main wiring diagram of the Liujia 66kV substation of the present invention;

[0030] Figure 3 This is a schematic diagram of a custom order before and after adjustment of the present invention. DETAILED DESCRIPTION

[0031] Embodiment 1:

[0032] The case background is the overhaul of Liujia 66kV#2 main transformer. The protection devices of 10kV Liangou Line 210, 10kV Liancheng Line 201, 10kV Jianye Line 207, 10kV Shifu Line 211, and 10kV Jianye Line 206 were replaced in sequence as planned. According to the theoretical analysis above, when there are multiple 10kV lines on the same section of bus that cannot be powered off, if there are conditions to replace the line protection in sequence without power outage, the method of installing temporary overcurrent in the section can be adopted, and its tripping circuit can be connected to the protection replacement interval outlet to ensure selectivity. At this time, the section temporary overcurrent and the protection of other non-stop lines on the bus section need to be coordinated in terms of setting, and there may be a risk of increased fault removal delay and insufficient sensitivity to faults at the end of the line. Figure 2 This is the main wiring diagram of Liujia 66kV substation.

[0033] Sectional protection temporary protection setting principle

[0034] When the protection devices of 10kV Liangou Line 210, 10kV Liancheng Line 201, 10kV Jianye Line 207, 10kV Shifu Line 211, and 10kV Jianye Line 206 are replaced, temporary protection is installed. When the line protection devices are replaced, the 10kV segment current is used to reflect the fault conditions of the 10kV line. The original 10kV segment setting is invalid, and the current 10kV segment protection setting is as follows:

[0035] The timing limit value is 2A 1S, the quick-break protection setting value is 5.76A 0.3S, and the CT ratio is 3000 / 5

[0036] Among them, the time-limited protection setting is set according to the maximum daytime load current of the #2 main and secondary transformers (the maximum daytime load current of the #2 main and secondary transformers is about 1000A, which is set at 1.2 times). The quick-break protection setting is set at 1.2 times the maximum quick-break current in the 10kVII section line (the maximum quick-break current is 209 cast steel wire 24A 0S, CT600 / 5). The time is coordinated with other lines without temporary protection, and at the same time coordinated with the main transformer backup protection to ensure that other lines without temporary protection can operate reliably when they fail. (The setting value of the overcurrent II section of the #2 main transformer is: 5.8A 1.5S, which is about 7.65A after conversion to the main and secondary transformers, the main primary CT is 600 / 5, and the main secondary CT is 3000 / 5). Custom orders before and after setting are as follows Figure 3 shown.

[0037] Embodiment 2:

[0038] A method for replacing a 10kV feeder line protection device without power outage by relying on a section switch, comprising the following steps:

[0039] S1: Before the replacement of the 10kV feeder line protection device without power outage, close the 10kV section switch, and the operation mode of the main transformer in the station is changed to one main transformer with two busbars. The main transformer of the busbar where the protection is replaced is switched to hot standby state, and the other main transformer is in operation, and the standby automatic switch is disabled;

[0040] S2: Install temporary overcurrent protection at the 10kV section switch, and its protection AC sampling value (current and voltage value) is taken from the current and voltage transformer at the 10kV section switch; at the same time, connect the tripping circuit to the 10kV feeder line switch that needs to be replaced;

[0041] S3: The new setting calculation principle is used to calculate the temporary overcurrent protection setting value. The main principles are:

[0042] The temporary overcurrent protection setting value described in overcurrent section I is set at 1.2 times the maximum quick-break current in the line of the bus where the 10kV replacement protection is located;

[0043] The temporary overcurrent protection setting value described in overcurrent stage II is set according to the maximum daytime load current of the main secondary of the main transformer in bypassing operation;

[0044] S3-1: The overcurrent I section is the current quick-break protection, which is set according to the maximum short-circuit current of the three-phase busbar on the other side of the largest transformer of this line. The specific formula is as follows:

[0045]

[0046] I=1.2I opI

[0047] In the formula, I B Indicates the reference current on the 10kV side, Z max Indicates the maximum per unit value of 10kV busbar, Z K Indicates the maximum transformer impedance per unit value of this line, Z XL Indicates the per unit value of line impedance from line outlet to maximum transformer, K K Represents the reliability coefficient, the reliability coefficient ≥ 1.5. At the same time, when the time limit setting needs to be coordinated with the time of the lower-level opening and closing station, a time difference Δt can be added, and the value range of Δt is 0.2~0.3s;

[0048] S3-2: The overcurrent II stage is a time-limited overcurrent protection, which is set according to the maximum daytime load current of the main secondary transformer in the bypass operation. The specific formula is as follows:

[0049] I opII ≥K K I fmax

[0050] K k ≥1.3

[0051] In the formula, I fmax Indicates the maximum current value of the main secondary transformer during the day on this side;

[0052] S3-3: Check the sensitivity of overcurrent protection to the end of this line;

[0053]

[0054] In the formula, Indicates the short-circuit current when the end of this line is short-circuited;

[0055] S4: Set the fixed value I opI It is installed in the temporary overcurrent protection device to replace the original 10kV feeder line protection. When a fault occurs on the line side, the temporary protection will trip the section switch to isolate the fault, so that the feeder line protection can be replaced without power outage.

[0056] In step S2, the tripping circuit is connected to the 10kV feeder line switch that needs to be replaced to facilitate the collection of current and voltage values ​​for temporary overcurrent protection, while ensuring that only the corresponding 10kV feeder line is tripped when a fault trips, minimizing the scope of fault power outage and satisfying the selectivity of relay protection professionals.

[0057] The deactivation of the standby automatic transfer mode means that the premise of replacing the protection device without power outage is to convert one main transformer into hot standby, which does not meet the charging conditions of the segmented standby automatic transfer mode. At the same time, under this mode, the main transformer standby automatic transfer mode cannot be enabled due to the tripping of the segmented switch, so the standby automatic transfer device needs to be deactivated.

[0058] The line end sensitivity refers to whether the set value calculated by the setting can satisfy the normal operation of the protection device when a fault occurs at the line end, and whether it responds to the fault condition at the line end.

[0059] The above embodiments are only used to illustrate the technical solution 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 they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for replacing a 10kV feeder line protection device without power outage by relying on a section switch, characterized in that: The following steps are involved: S1: Before the replacement of the 10kV feeder line protection device without power outage, close the 10kV section switch, and the operation mode of the main transformer in the station is changed to one main transformer with two busbars. The main transformer of the busbar where the protection is replaced is switched to hot standby state, and the other main transformer is in operation, and the standby automatic switch is disabled; S2: Install temporary overcurrent protection at the 10kV section switch, and its protection AC sampling value (current and voltage value) is taken from the current and voltage transformer at the 10kV section switch; at the same time, connect the tripping circuit to the 10kV feeder line switch that needs to be replaced; S3: The new setting calculation principle is used to calculate the temporary overcurrent protection setting value. The main principles are: The temporary overcurrent protection setting value described in overcurrent section I is set at 1.2 times the maximum quick-break current in the line of the bus where the 10kV replacement protection is located; The temporary overcurrent protection setting value described in overcurrent stage II is set according to the maximum daytime load current of the main secondary of the main transformer in bypassing operation; S3-1: The overcurrent I section is the current quick-break protection, which is set according to the maximum short-circuit current of the three-phase busbar on the other side of the largest transformer of this line. The specific formula is as follows: I=1.2I opI In the formula, I B Indicates the reference current on the 10kV side, Z max Indicates the maximum per unit value of 10kV busbar, Z K Indicates the maximum transformer impedance per unit value of this line, Z XL Indicates the per unit impedance of the line from the line outlet to the maximum transformer, K K Represents the reliability coefficient, the reliability coefficient ≥ 1.

5. At the same time, when the time limit setting needs to be coordinated with the time of the lower-level opening and closing station, a time difference Δt can be added, and the value range of Δt is 0.2~0.3s; S3-2: The overcurrent II stage is a time-limited overcurrent protection, which is set according to the maximum daytime load current of the main secondary transformer in the bypass operation. The specific formula is as follows: I opII ≥K K I fmax K k ≥1.3 In the formula, I fmax Indicates the maximum current value of the main secondary transformer during the day on this side; S3-3: Check the sensitivity of overcurrent protection to the end of this line; In the formula, Indicates the short-circuit current when the end of this line is short-circuited; S4: Set the fixed value I opI It is installed in the temporary overcurrent protection device to replace the original 10kV feeder line protection. When a fault occurs on the line side, the temporary protection will trip the section switch to isolate the fault, so that the feeder line protection can be replaced without power outage.

2. The method for replacing a 10kV feeder line protection device without power outage by relying on a section switch according to claim 1 is characterized in that: In step S2, the tripping circuit is connected to the 10kV feeder line switch that needs to be replaced to facilitate the collection of current and voltage values ​​for temporary overcurrent protection, while ensuring that only the corresponding 10kV feeder line is tripped when a fault trips, minimizing the scope of fault power outage and satisfying the selectivity of relay protection professionals.

3. The method for replacing a 10kV feeder line protection device without power outage by relying on a section switch according to claim 1, characterized in that: The deactivation of the standby automatic transfer mode means that the premise of replacing the protection device without power outage is to convert one main transformer into hot standby, which does not meet the charging conditions of the segmented standby automatic transfer mode. At the same time, under this mode, the main transformer standby automatic transfer mode cannot be enabled due to the tripping of the segmented switch, so the standby automatic transfer device needs to be deactivated.

4. The method for replacing a 10kV feeder line protection device without power outage by relying on a section switch according to claim 1, characterized in that: The line end sensitivity refers to whether the set value calculated by the setting can satisfy the normal operation of the protection device when a fault occurs at the line end, and whether it responds to the fault condition at the line end.

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