Transmission tower grounding disconnection-free resistance online measurement system and measurement method

Abstract

The invention, which relates to the technical field of tower grounding resistance measurement, discloses an on-line measurement system and measurement method for a grounding unwiring-free resistance value of a power transmission tower, comprising a central server, a plurality of communication control hosts and a plurality of grounding resistance measurement hosts. Each transmission tower is provided with a communication control host, a grounding resistance measurement host, four pairs of voltage transformers and current transformers. According to the power transmission tower grounding wire-disconnection-free resistance online measurement system and measurement method, distributed measurement big data is used for analysis, manual regular grounding resistance measurement work is effectively solved, high-precision voltage, current and phase measurement is achieved, and the measurement precision is improved. More accurate data and technical basis are provided for equipment operation and next-step line design and maintenance; according to the method, the line-unwrapping-free measurement of the grounding resistance of the power transmission line tower can be realized, whether the power transmission line is suitable for loop method measurement can be judged, and the measurement precision of the grounding resistance is improved by calculating compensation by using an iterative method.

Description

Technical Field

[0001] The invention relates to the technical field of pole tower grounding resistance measurement, in particular to an online measurement system and method for the resistance of a transmission pole tower grounding without wire untangling. Background Art

[0002] Lightning protection technology has always been a concern of the power system. As the connection hub of the power system, the transmission line tower is long, widely distributed, and the environment along the line is complex and changeable. It is easy to be struck by lightning. Its safety has received extensive attention from the power department. According to statistics, among the categories of transmission line faults, accidents caused by lightning strikes on transmission line towers have always been ranked first. Especially in remote mountainous areas, the incidence of lightning strikes on transmission towers is high, and the frequency of lightning strike accidents is also high, which brings huge economic losses and makes emergency repairs more difficult.

[0003] The grounding channel of the transmission line is composed of overhead lightning arresters, the tower itself, grounding down conductors, and grounding devices. The power department has taken corresponding measures to protect the transmission line towers from lightning strikes, such as reducing the grounding resistance of the transmission towers, erecting lightning arresters, and installing automatic reclosing devices. Reducing the grounding resistance of the transmission towers and erecting lightning arresters are widely used because of their easy implementation and obvious effects. However, the grounding devices of the transmission towers are exposed to the outdoor environment all year round. During the long-term operation, they are susceptible to corrosion from the environment and soil. The grounding down conductors are prone to failure due to corrosion and poor contact with the towers, which reduces the lightning protection effect of the grounding devices. The parameters in the grounding system will also change due to changes in external climate conditions and the years of operation. Therefore, periodic detection of the tower grounding system parameters has become an important task for the power inspection department. According to DLT 741-2019 "Overhead Transmission Line Operation Regulations", the grounding resistance of transmission line towers must be measured once every four years, which takes up a lot of manpower and material resources, and the measurement results are greatly affected by the skill level of the personnel.

[0004] The existing wire-free resistance measurement method relies heavily on the electrical model of the overhead ground wire of the transmission line and the adjacent towers. Ignoring this influencing factor will introduce measurement errors (clamp meter method increment) just like the loop method. Even if the grounding resistance of the adjacent multi-level towers does not meet the requirements, the measurement results of the base tower will be meaningless.

[0005] In addition, DL / T887-2004 "Measurement of Power Frequency Grounding Resistance of Towers" has detailed requirements for the number of parallel towers on the directly grounded lightning arrester in the line section where the measurement is located. As shown in the following table, it can be seen that when the clamp meter method is used to measure the tower grounding resistance, its scope of use has a one-to-one correspondence requirement for the grounding resistance and the number of parallel towers. However, in actual measurement, the number of parallel towers and the value of the tower grounding resistance may not correspond, which means that the line grounding resistance is not suitable for loop method measurement. However, in actual application, the value of the tower grounding resistance and the parallel tower number base need to be measured before the conclusion can be obtained, which affects the measurement speed and accuracy of the tower grounding resistance.

[0006]

[0007] Therefore, there is an urgent need for an online measurement system and method for the grounding resistance of a transmission tower without wire untangling, which can perform regular detection of the grounding resistance and provide accurate data and technical basis for equipment operation and the next step of line design and maintenance. Summary of the invention

[0008] In order to solve the problem of manual periodic measurement of grounding resistance, the present invention aims to provide a transmission tower grounding resistance online measurement system and method without wire untangling.

[0009] In order to achieve the above object, the present invention is implemented through the following technical solutions: A transmission tower grounding resistance online measurement system without wire untangling comprises a central server, several communication control hosts and several grounding resistance measurement hosts. A communication control host, a grounding resistance measurement host, four pairs of voltage transformers and current transformers are installed on each transmission tower.

[0010] Preferably, the ground resistance measurement host is composed of the following structures connected in series: a battery circuit, a power amplification module, a sinusoidal measurement signal generation module, a CPU control core part, a filtering module, a signal conditioning module and an I / V conversion module.

[0011] Preferably, 4G / 5G wireless transmission is adopted between the communication control host and the central server.

[0012] Preferably, the ground resistance measurement host and the communication control host are connected via RS485 wired connection.

[0013] Preferably, each pair of voltage transformer and current transformer is connected to the ground resistance measurement host through a cable.

[0014] Preferably, Zigbee communication is adopted between adjacent tower communication control hosts.

[0015] The present invention also includes a method for measuring the resistance of a transmission tower grounding wire that does not require untangling by using the above-mentioned transmission tower grounding wire-free untangling online measurement system, comprising the following steps: Step 1: For the k-base towers installed with the transmission tower grounding free wire resistance online measurement system, the resistance is measured by the loop method, and its value is recorded as T k ; R 1~ R N is the grounding resistance value of each measured tower on the same line, R L2 ~ R LN is the equivalent resistance value of the overhead ground wire between the two towers, R eq is the equivalent ground resistance value of the non-tested tower. When the number of transmission line towers is large enough, this value approaches 0; Step 2: Assume that the overhead ground wire resistance of the entire line is much smaller than the grounding resistance value, which is recorded as 0, and do not consider the parallel grounding resistance value of each base tower where the equipment is not installed; Step 3, R is the phase quantity formed by the grounding resistance values ​​of each tower of the line, that is, R=[R1,R2,R3……R N ]; Step 4: Construct F(R) and F'(R) based on Newton's method -1 Compute the matrix: F ( R )=[ F 1( R ), F 2( R ), F 3( R )…… F N ( R )],and

[0016] F’ ( R ) is the above F ( R ) For each R k The matrix obtained by partial derivative is

[0017] F’ ( R ) -1 For the above F’ ( R ), that is, it satisfies: F’ ( R ) -1 · F’ ( R )=1 (5) Step 5, set R ( n ) n represents the nth iteration of the iterative expression; similarly, R ( n+ 1) n +1 indicates the n+1th iteration of the iteration; Build iteratively:

[0018] in:

[0019] Step 6, the initial value of the iteration, that is R k (0)= T k ; Substitute R(0) into the iterative form , and iterate multiple times; Step 7: When performing iterative calculations, for any branch k ,if

[0020] Then judge that due to R L2 ~ R LN and R eq The measurement method introduces a large error, that is, the line is not suitable for loop method measurement; Step 8: When performing iterative calculations, for any branch k, if

[0021] Right now R L2 ~ R LN and R eq are all small, then the above iterative method is used, and the result is convergent. The above iterative formula can be used to calculate the k The grounding resistance value of the base tower; when it is iterated to all branches When , the iteration ends, the result R k ( n +1) is what we are looking for, is the set calculation allowable error; Steps 7 and 8 are performed in no particular order.

[0022] Preferably, step 7 and step 8 are performed in sequence.

[0023] Preferably, the The value range is: 10 -3 .

[0024] Preferably, when the conclusion of step 7 appears, the line is measured using a three-pole method.

[0025] Compared with the prior art, the present invention has the following advantages: The transmission tower grounding resistance online measurement system and method of the present invention, by studying the distributed grounding online measurement system and using distributed measurement big data for analysis, effectively solves the problem of manual periodic measurement of grounding resistance, and provides more accurate data and technical basis for equipment operation and the next step of line design and maintenance through high-precision voltage, current and phase measurement.

[0026] The transmission tower grounding resistance online measurement system and method of the present invention can realize the line-free measurement of the grounding resistance of the transmission line tower, and can determine whether the transmission line is suitable for loop method measurement. At the same time, the measurement accuracy of the grounding resistance is improved by calculating compensation using an iterative method. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the composition of the online measurement system for the resistance of the transmission tower grounding wire without untangling the wire according to the present invention; Figure 2 Provide a schematic diagram of the measurement system equipment installation on each transmission tower; Figure 3 This is the structural connection diagram of the ground resistance measurement host; Figure 4 It is the equivalent circuit diagram of the transmission tower under test; Figure 5 It is an iterative change trend diagram of each data in Example 3; Figure 6 It is an iterative change trend diagram of each data in Example 4; Figure numerals: 1 communication control host, 2 ground resistance measurement host, 3 voltage transformer, 4 current transformer, 5 groove wiring. DETAILED DESCRIPTION

[0028] The object of the present invention is to provide a transmission tower grounding wire-free resistance online measurement system and method, and the present invention is further described below in conjunction with specific embodiments.

[0029] The transmission tower grounding resistance online measurement system described in the present invention is a transmission tower grounding resistance online monitoring system, and the transmission tower grounding resistance online measurement method is a transmission tower grounding resistance online monitoring method. Example 1

[0030] A transmission tower grounding resistance online measurement system without wire untangling, such as Figure 1 As shown, it includes a central server, several communication control hosts and several ground resistance measurement hosts; among them, the ground resistance measurement host adopts a method of measuring the ground resistance of the tower without untangling the wires, realizing the online measurement of the ground resistance of the transmission line tower; the communication control host is used to communicate data with the central server; the central server analyzes and processes the received data, including data cleaning, filtering, calculation and storage. Figure 2 As shown, each transmission tower is equipped with a communication control host 1, a grounding resistance measurement host 2, four pairs of voltage transformers 3 and current transformers 4. The grounding measurement host 2 and the communication control host 1 are installed on the first-level cross arm of the tower, and the four sets of voltage transformers 3 and current transformers 4 are respectively mounted on the tower grounding down conductors and buried under the soil layer. The transformers and the hosts are connected by cables and routed along the tower groove 5 and fixed.

[0031] like Figure 3 As shown, the ground resistance measurement host is composed of the following structures connected in series: a battery circuit, a power amplifier module, a sinusoidal measurement signal generation module, a CPU control core part, a filter module, a signal conditioning module and an I / V conversion module.

[0032] The communication control host and the central server use 4G / 5G wireless transmission to achieve long-distance transmission of measurement data.

[0033] The ground resistance measurement host and the communication control host are connected via RS485 wired connection, thereby avoiding strong electromagnetic interference of the high-voltage transmission line at the tower and improving the reliability of data transmission.

[0034] Zigbee communication is used between adjacent tower communication control hosts.

[0035] Each pair of voltage transformers and current transformers is connected to the ground resistance measurement host through cables. Example 2

[0036] The method for measuring the resistance of a transmission tower grounding wire that does not require untwisting by using the online measurement system for the resistance of a transmission tower grounding wire that does not require untwisting described in Example 1 comprises the following steps: Step 1: For the k-base tower installed with the transmission tower grounding free wire resistance online measurement system, the resistance is measured by the loop method, and its value is recorded as Tk When multiple adjacent towers on the same line are installed with the transmission tower grounding free wire resistance online measurement system mentioned in the present invention, the iterative approximation algorithm can be used to improve the measurement accuracy of the tower, such as Figure 4 As shown, R 1~ R N is the grounding resistance value of each measured tower on the same line, R L2 ~ R LN is the equivalent resistance value of the overhead ground wire between the two towers, R eq is the equivalent ground resistance value of the non-tested tower. When the number of transmission line towers is large enough, this value approaches 0; In the prior art, according to the clamp meter method, a voltage is applied to the tower under test. U , and measure the magnitude of the current signal I 1. When a large number of towers are connected in parallel, U / I This is the grounding resistance value of the base tower. But in fact, this data will include the error of the clamp meter method increment.

[0037] For example, for R 1 branch, its grounding resistance is R 1. When using the clamp meter method to measure R When there is 1 branch, use the voltage transformer to R 1 branch voltage applied U 1. Use the current transformer to measure the current signal I 1. Assume T 1= U 1 / I 1, then according to circuit theory, we know that:

[0038] Considering the generality, then:

[0039] Measurement value T 1 and the grounding resistance value is R The difference between 1 is the measurement error. R L2 ~ R LN and R eq When it is large, the error introduced by this method is large, which is reflected in the fact that the grounding resistance value of the adjacent tower affects the measurement accuracy of the base tower.

[0040] like R L2 ~R LN and R eq are all 0, that is

[0041] Based on Newton's method, construct the matrix iteration formula:

[0042] Step 2: Assume that the overhead ground wire resistance of the entire line is much smaller than the grounding resistance value, which is recorded as 0, and do not consider the parallel grounding resistance value of each base tower where the equipment is not installed; Step 3, R is the phase quantity formed by the grounding resistance values ​​of each tower of the line, that is, R=[R1,R2,R3……R N ]; Step 4: Construct F(R) and F'(R) -1 Compute the matrix: F ( R )=[ F 1( R ), F 2( R ), F 3( R )…… F N ( R )],and

[0043] F’ ( R ) is the above F ( R ) For each R k The matrix obtained by partial derivative is

[0044] F’ ( R ) -1 For the above F’ ( R ), that is, it satisfies: F’ ( R ) -1 · F’ ( R )=1 (5) Step 5, set R ( n ) n represents the nth iteration of the iterative expression; similarly, R ( n+ 1)n +1 indicates the n+1th iteration of the iteration; Build iteratively: ; in: ; Step 6, the initial value of the iteration, that is R k (0)= T k ; Substitute R(0) into the iterative form , and iterate multiple times; Step 7: When performing iterative calculations, for any branch k ,if

[0045] Then judge that due to R L2 ~ R LN and R eq The measurement method introduces a large error, that is, the line is not suitable for loop method measurement; Step 8: When performing iterative calculations, for any branch k, if

[0046] Right now R L2 ~ R LN and R eq are all small, then the above iterative method is used, and the result is convergent. The above iterative formula can be used to calculate the k The grounding resistance value of the base tower; when it is iterated to all branches When , the iteration ends, the result R k ( n +1) is what we want, The calculation tolerance is set.

[0047] In the above operation, step 7 and step 8 can be performed in any order or in sequence.

[0048] In actual operation, the The value range is: 10 -3 .

[0049] When the conclusion of step 7 is reached, the line is measured using the three-pole method. Example 3

[0050] A transmission line on which four sets of the transmission tower grounding resistance online measurement system described in Example 1 are installed has grounding resistance values ​​of 3.32, 4.39, 3.75, and 3.93 respectively measured based on the loop method. A method for measuring the grounding resistance of a transmission tower using the transmission tower grounding resistance online measurement system described in Example 1 includes the following steps: Step 1, that is T 1=3.32, T 2=4.39, T 3=3.75, T 4=3.93.

[0051] Step 2: Assume that the overhead ground wire resistance of the entire line is much smaller than the grounding resistance value, which is recorded as 0, and do not consider the parallel grounding resistance value of each base tower where the equipment is not installed; Step 3, Build R (0), then R (0) = [3.32, 4.39, 3.75, 3.93] Step 4: Construct F(R) and F'(R) -1 Compute the matrix: F ( R )=[ F 1( R ), F 2( R ), F 3( R )…… F N ( R )],and

[0052] F’ ( R ) is the above F ( R ) For each R k The matrix obtained by partial derivative is According to formula (4), the F’ ( R ) is calculated as

[0053] Will R (0) If

[0054] According to step 6: R (0) Bring in the iterative formula ,have to R (1) = [2.2950, ​​3.5006, 2.7984, 2.9999] Repeat steps 4 to 5.

[0055]

[0056] Will R (1) Bring in the iterative formula ,have to

[0057] Repeat steps 4 to 5.

[0058] at this time, R (3) R (2) If they are equal, the iteration ends. R 1=2.2950Ω, R 2=3.5017Ω, R 3=2.8016Ω, R 4 = 3.0026Ω The iterative change trend of each data is as follows Figure 5 As shown, it can be seen that with the increase of the number of iterations, the data gradually reaches a certain value. Example 4

[0059] A transmission line is installed with 4 sets of the transmission tower grounding resistance online measurement system described in Example 1, and its grounding resistance values ​​are measured to be 4, 0.2, 3, and 0.7 respectively based on the loop method. The method for measuring the transmission tower grounding resistance online measurement system described in Example 1 comprises the following steps: Step 1, that is T 1=4, T 2=0.2, T 3=3, T 4=0.7; Step 2: Assume that the overhead ground wire resistance of the entire line is much smaller than the grounding resistance value, which is recorded as 0, and do not consider the parallel grounding resistance value of each base tower where the equipment is not installed; According to step 3, build R (0), then R (0) = [4, 0.2, 3, 0.7] According to step 4 and formula (4), the F’ ( R ) is calculated as

[0060] Will R (0) If

[0061] According to step 6: R (0) Bring in the iterative formula ,have to

[0062] Repeat steps 4 to 5.

[0063]

[0064] Will R (1) Bring in the iterative formula ,have to

[0065] Repeat steps 4 to 5.

[0066] The iterative change trend of each data is as follows Figure 6 As shown in the figure, it can be seen that with the increase of the number of iterations, the data gradually diverges and fails to reach a certain value, that is, the circuit is not suitable for loop method measurement. The reason is that Figure 4 In, R L2 ~R LN The larger the value of Req is, the larger the measurement error will be when measuring using the loop method.

Claims

1. A transmission tower grounding resistance online measurement system without wire untangling, characterized by: It comprises a central server, a plurality of communication control hosts and a plurality of ground resistance measurement hosts. Each transmission tower is equipped with a communication control host (1), a ground resistance measurement host (2), four pairs of voltage transformers (3) and a current transformer (4).

2. The online measurement system for the grounding resistance of a transmission tower without wire untangling according to claim 1 is characterized by: The ground resistance measurement host is composed of the following structures in series: a battery circuit, a power amplifier module, a sinusoidal measurement signal generation module, a CPU control core part, a filter module, a signal conditioning module and an I / V conversion module.

3. The online measurement system for the grounding resistance of a transmission tower without wire untangling according to claim 1 is characterized in that: The communication control host and the central server use 4G / 5G wireless transmission.

4. The online measurement system for the grounding resistance of a transmission tower without wire untangling according to claim 1 is characterized in that: The ground resistance measurement host and the communication control host are connected via RS485 wired connection.

5. The online measurement system for the grounding resistance of a transmission tower without wire untangling according to claim 1 is characterized by: Each pair of voltage transformers and current transformers is connected to the ground resistance measurement host through cables.

6. The online measurement system for the grounding resistance of a transmission tower without wire untangling according to claim 1 is characterized by: Zigbee communication is used between adjacent tower communication control hosts.

7. A method for measuring the resistance of a transmission tower grounding wire without untangling the line using the online measurement system for the resistance of a transmission tower grounding wire without untangling the line as described in claim 1, characterized in that: The following steps are involved: Step 1: For the k-base tower installed with the transmission tower grounding free wire resistance online measurement system, the resistance is measured by the loop method, and its value is recorded as T k ; R 1~ R N is the grounding resistance value of each measured tower on the same line, R L2 ~ R LN is the equivalent resistance value of the overhead ground wire between the two towers, R eq is the equivalent ground resistance value of the non-tested tower. When the number of transmission line towers is large enough, this value approaches 0; Step 2: Assume that the overhead ground wire resistance of the entire line is much smaller than the grounding resistance value, which is recorded as 0, and do not consider the parallel grounding resistance value of each base tower where the equipment is not installed; Step 3, R is the phase quantity formed by the grounding resistance values ​​of each tower of the line, that is, R=[R1,R2,R3……R N ]; Step 4: Construct F(R) and F'(R) -1 Compute the matrix: F ( R )=[ F 1( R ), F 2( R ), F 3( R )…… F N ( R )],and ； F’ ( R ) is the above F ( R ) For each R k The matrix obtained by partial derivative is ； F’ ( R ) -1 For the above F’ ( R ), that is, it satisfies: F’ ( R ) -1 · F’ ( R )=1 （5） Step 5, set R ( n ) n represents the nth iteration of the iterative expression; similarly, R ( n+ 1) n +1 indicates the n+1th iteration of the iteration; Build iteratively: ； in: ； Step 6, the initial value of the iteration, that is R k (0)= T k ; Substitute R(0) into the iterative form , and iterate multiple times; Step 7: When performing iterative calculations, for any branch k ,if ； Then judge that due to R L2 ~ R LN and R eq The measurement method introduces a large error, that is, the line is not suitable for loop method measurement; Step 8: When performing iterative calculations, for any branch k, if ； Right now R L2 ~ R LN and R eq are all small, then the above iterative method is used, and the result is convergent. The above iterative formula can be used to calculate the k The grounding resistance value of the base tower; when it is iterated to all branches When , the iteration ends, the result R k ( n +1) is what we want, is the set calculation allowable error; Steps 7 and 8 are performed in no particular order.

8. The method for measuring the resistance of a transmission tower grounding wire without untangling the wire according to claim 7, characterized in that: Step 7 and step 8 are performed in sequence.

9. The method for measuring the resistance of a transmission tower grounding wire without untangling the wire according to claim 7, characterized in that: Said The value range is: 10 -3 .

10. The method for measuring the resistance of a transmission tower grounding wire without untangling the wire according to claim 7, characterized in that: When the conclusion of step 7 is reached, the line is measured using the three-pole method.

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