Lightning channel voltage drop metering method and system and medium

Abstract

The invention discloses a near-surface lightning channel voltage drop metering method and system and a medium. Relates to the technical field of lightning electric field measurement. The invention provides a near-surface lightning channel voltage drop metering method, which improves the metering method on the basis of the traditional technology, and provides a new technical concept that a near-surface thundercloud channel is equivalent to a finite-length electrified straight wire, and the voltage drop of the near-surface thundercloud channel is calculated according to Maxwell equations by using an infinitesimal method. Obtaining the electric field intensity of any point in the space; through the above technical concept, the scheme determines the auxiliary measurement point, constructs the auxiliary measurement model of the lightning channel, and achieves the on-site direct measurement of the voltage drop of the lightning channel through the geometrical relationship model between the auxiliary measurement point and the lightning channel, thereby improving the accuracy of the measurement result of the voltage drop of the near-surface lightning channel and the convenience of the measurement method.

Description

Technical Field

[0001] The present invention relates to the technical field of lightning electric field measurement, and in particular to a lightning channel voltage drop measurement method, system and medium. Background Art

[0002] It is of great significance to measure the voltage drop of the lightning channel near the ground. The voltage drop of the lightning channel near the ground is an important indicator for evaluating and predicting the safety of buildings, equipment and personnel struck by lightning. The voltage drop of the lightning channel near the ground will also directly affect the safe operation of the equipment and electrical systems connected to the channel. By measuring the voltage drop of the lightning channel, appropriate protection measures such as lightning rods and lightning protection devices can be selected and configured according to the design requirements to protect the equipment from damage caused by lightning. The voltage drop of the lightning channel is also crucial to the protection of buildings. Lightning channels with low resistance are more likely to attract and conduct lightning, thereby reducing the risk of buildings being struck by direct lightning. Measuring the voltage drop can help evaluate the effectiveness of the lightning protection system of the building and identify areas that may need improvement. Therefore, by measuring the voltage drop of the lightning channel near the ground, it can provide important data for studying lightning phenomena, predicting lightning activities and formulating relevant safety standards. Understanding the voltage drop of the lightning channel will help further study the physical process of lightning, the energy release mechanism and the remote impact of lightning.

[0003] However, the current means of measuring the voltage drop of near-ground lightning channels are still imperfect. Measuring the resistance of thundercloud channels is a relatively difficult task. Lightning channels occur in the air, usually at high altitudes and far from the ground. Due to the dangerous and unpredictable nature of lightning activity, it is very dangerous to directly approach thundercloud channels for measurement. This makes it very difficult to directly measure the voltage drop of lightning channels in actual scenarios. Thundercloud channels are usually located in complex atmospheric environments, including strong electric fields, extreme temperatures, high humidity, and strong winds. These factors can pose challenges to the selection and reliability of measurement equipment and techniques. There is currently no feasible method for directly measuring the voltage drop of near-ground lightning channels. Due to the complexity and dynamics of lightning channels, as well as the safety requirements for humans and equipment, it is extremely difficult to directly measure the voltage drop of lightning channels. Summary of the invention

[0004] In view of the problem that traditional methods cannot directly measure the voltage drop of near-ground lightning channels, the purpose of the present invention is to provide a method, system and medium for measuring the voltage drop of near-ground lightning channels, which equates the near-ground thundercloud channel to a charged straight wire of finite length, determines auxiliary measurement points, and constructs an auxiliary measurement model of the lightning channel. Through the geometric relationship model between the auxiliary measurement points and the lightning channel, direct on-site measurement of the voltage drop of the lightning channel is realized, thereby improving the accuracy of the measurement results of the voltage drop of the near-ground lightning channel and the convenience of the measurement method.

[0005] The present invention is achieved through the following technical solutions:

[0006] This solution provides a method for measuring voltage drop in a near-ground lightning channel, including:

[0007] Determine auxiliary measurement points and construct an auxiliary measurement model of the lightning channel; the auxiliary measurement model is a geometric relationship model between the auxiliary measurement points and the lightning channel when the lightning channel is equivalent to a charged straight wire of finite length;

[0008] The parameters of the auxiliary measurement points are obtained, and the parameters of the auxiliary measurement points are input into the auxiliary measurement model to obtain the lightning channel voltage drop.

[0009] Working principle of this scheme: Lightning channels occur in the air, usually at high altitudes and far away from the ground; due to the danger and unpredictability of lightning activities, it is very dangerous and difficult to directly approach the thundercloud channel for measurement; thundercloud channels are usually located in complex atmospheric environments, which poses challenges to the selection and reliability of measurement equipment and technologies; the traditional method is to obtain the empirical resistance of the lightning channel based on the lightning channel equivalent model, and then estimate the voltage of the lightning channel based on the current, but in different environmental scenarios, the lightning channel equivalent model is different, and the estimated voltage of the lightning channel also has a large deviation; in view of this, this scheme provides a near-ground lightning channel. The method for measuring the voltage drop in the lightning channel is improved on the basis of the traditional technology. This scheme provides a new technical concept: the near-ground thundercloud channel is equivalent to a finite-length charged straight wire, and the on-site direct measurement of the voltage drop in the lightning channel is realized according to the geometric relationship model between the auxiliary measurement point and the lightning channel, so as to obtain the electric field strength at any point in the space; through the above technical concept, this scheme determines the auxiliary measurement points, and constructs an auxiliary measurement model of the lightning channel, and realizes the on-site direct measurement of the voltage drop in the lightning channel through the geometric relationship model between the auxiliary measurement points and the lightning channel, thereby improving the accuracy of the measurement results of the voltage drop in the near-ground lightning channel and the convenience of the measurement method.

[0010] A further optimization scheme is that the auxiliary measurement point includes a first auxiliary measurement point and a second auxiliary measurement point;

[0011] The first auxiliary measurement point and the second auxiliary measurement point are both located on a vertical line A, and the vertical line A is parallel to the lightning channel.

[0012] A further optimization scheme is that the parameters of the auxiliary measurement points include:

[0013] The height h1 and field strength E of the first auxiliary measurement point 01 ;

[0014] The height h2 and field strength E of the second auxiliary measurement point 02 ;

[0015] The distance r between the vertical line A and the lightning channel.

[0016] A further optimization scheme is that the auxiliary metering model includes:

[0017]

[0018]

[0019]

[0020]

[0021] Among them, E i represents the heavy field strength at the same height as the i-th auxiliary measurement point on the lightning channel; h i Indicates the height of the i-th auxiliary measurement point; i = 1, 2; H is the height of the lightning channel; θ1 indicates the angle between the line connecting the highest point of the lightning channel and the first auxiliary measurement point and the vertical line A; θ2 indicates the angle between the line connecting the highest point of the lightning channel and the second auxiliary measurement point and the vertical line A; U is the surface lightning channel voltage drop. .

[0022] This solution also provides a near-ground lightning channel voltage drop measurement system, which is used to implement the above-mentioned near-ground lightning channel voltage drop measurement method, and the system includes:

[0023] A model building module, used to determine auxiliary measurement points and build an auxiliary measurement model of the lightning channel; the auxiliary measurement model is a geometric relationship model between the auxiliary measurement points and the lightning channel when the lightning channel is equivalent to a charged straight wire of finite length;

[0024] Acquisition module, used to obtain parameters of auxiliary measurement points;

[0025] The calculation module is used to input the auxiliary measurement point parameters into the auxiliary measurement model to obtain the lightning channel voltage drop.

[0026] A further optimization scheme is that the acquisition module includes a drone array and a control center

[0027] Each drone in the drone array includes: a drone body, an airborne control module, a laser radar three-dimensional imaging module, and an electric field measurement sensor module;

[0028] The airborne control module is used to adjust the position of the UAV according to the control instructions issued by the control center;

[0029] The laser radar three-dimensional imaging module is used to sense the three-dimensional space flight position of the drone;

[0030] The electric field measurement sensor module is suspended below the drone body and is used to sense electric field data;

[0031] The control center is used to obtain the electric field distribution of the auxiliary measurement point according to the three-dimensional spatial flight position of the UAV and the electric field data acquired by the UAV array, and the electric field distribution includes the position data and electric field data of the auxiliary measurement point.

[0032] A further optimization scheme is that the auxiliary measurement point includes a first auxiliary measurement point and a second auxiliary measurement point;

[0033] The first auxiliary measurement point and the second auxiliary measurement point are both located on a vertical line A, and the vertical line A is parallel to the lightning channel.

[0034] A further optimization scheme is that the parameters of the auxiliary measurement points include:

[0035] The height h1 and field strength E of the first auxiliary measurement point 01 ;

[0036] The height h2 and field strength E of the second auxiliary measurement point 02 ;

[0037] The distance r between the vertical line A and the lightning channel.

[0038] A further optimization scheme is that the auxiliary measurement point includes a first auxiliary measurement point and a second auxiliary measurement point;

[0039] The first auxiliary measurement point and the second auxiliary measurement point are both located on a vertical line A, and the vertical line A is parallel to the lightning channel.

[0040] A further optimization scheme is that the parameters of the auxiliary measurement points include:

[0041] The height h1 and field strength E of the first auxiliary measurement point 01 ;

[0042] The height h2 and field strength E of the second auxiliary measurement point 02 ;

[0043] The distance r between the vertical line A and the lightning channel.

[0044] A further optimization scheme is that the auxiliary metering model includes:

[0045]

[0046]

[0047]

[0048]

[0049] Among them, E i represents the heavy field strength at the same height as the i-th auxiliary measurement point on the lightning channel; hi Represents the height of the i-th auxiliary measurement point; i=1, 2; H is the height of the lightning channel; θ1 represents the angle between the line connecting the highest point of the lightning channel and the first auxiliary measurement point and the vertical line A; θ2 represents the angle between the line connecting the highest point of the lightning channel and the second auxiliary measurement point and the vertical line A; U is the surface lightning channel voltage drop.

[0050] The present solution also provides a computer-readable medium on which a computer program is stored. The computer program is executed by a processor to implement the above-mentioned method for measuring the voltage drop of a near-ground lightning channel.

[0051] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0052] The present invention provides a near-ground lightning channel voltage drop measurement method, system and medium; this scheme provides a near-ground lightning channel voltage drop measurement method, based on the traditional technology, the measurement method is improved, and this scheme provides a new technical concept: the near-ground thundercloud channel is equivalent to a finite-length charged straight wire, according to Maxwell's equations and using the differential element method, the electric field strength at any point in the space is obtained; through the above technical concept, this scheme determines the auxiliary measurement points, and constructs an auxiliary measurement model of the lightning channel, and realizes the on-site direct measurement of the lightning channel voltage drop through the geometric relationship model between the auxiliary measurement points and the lightning channel, thereby improving the accuracy of the near-ground lightning channel voltage drop measurement results and the convenience of the measurement method. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other relevant drawings can be obtained based on these drawings without creative work. In the drawings:

[0054] Figure 1 This is a flow chart of the method for measuring the voltage drop of a near-ground lightning channel;

[0055] Figure 2 This is a schematic diagram of the voltage drop measurement principle of the near-ground lightning channel;

[0056] Figure 3 Schematic diagram of the voltage drop measurement process of near-ground lightning channel. DETAILED DESCRIPTION

[0057] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments and drawings. The exemplary embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0058] At present, the measurement methods for the voltage drop of near-ground lightning channels are still imperfect. Measuring the resistance of thundercloud channels is a relatively difficult task. Lightning channels occur in the air, usually at high altitudes and far from the ground. Due to the dangerous and unpredictable nature of lightning activity, it is very dangerous to directly approach thundercloud channels for measurement. This makes it very difficult to directly measure the voltage drop of lightning channels in actual scenarios. Thundercloud channels are usually located in complex atmospheric environments, including strong electric fields, extreme temperatures, high humidity, and strong winds. These factors will challenge the selection and reliability of measurement equipment and technology. There is currently no feasible method to directly measure the voltage drop of near-ground lightning channels. Due to the complexity and dynamics of lightning channels, as well as the safety requirements for humans and equipment, it is extremely difficult to directly measure the voltage drop of lightning channels.

[0059] In view of this, the present invention provides the following embodiments to solve the above problems:

[0060] Example 1

[0061] This embodiment provides a method for measuring voltage drop in a near-ground lightning channel. Figure 1 and Figure 2 As shown, including:

[0062] Step 1: determine the auxiliary measurement points and construct an auxiliary measurement model of the lightning channel; the auxiliary measurement model is a geometric relationship model between the auxiliary measurement points and the lightning channel when the lightning channel is equivalent to a charged straight wire of finite length; the auxiliary measurement points include a first auxiliary measurement point and a second auxiliary measurement point;

[0063] The first auxiliary measurement point and the second auxiliary measurement point are both located on a vertical line A, and the vertical line A is parallel to the lightning channel.

[0064] like Figure 3 As shown, the parameters of the auxiliary measurement point include:

[0065] The first auxiliary measurement point (i.e. Figure 3 The height h1 and field strength E of the drone monitoring point 1) 01 ;

[0066] The second auxiliary measurement point (i.e. Figure 3 The height h2 and field strength E of the drone monitoring point 2) 02 ;

[0067] The distance r between the vertical line A and the lightning channel.

[0068] Step 2: Obtain the parameters of the auxiliary measurement points, and input the parameters of the auxiliary measurement points into the auxiliary measurement model to obtain the lightning channel voltage drop.

[0069] The auxiliary metering model includes:

[0070]

[0071]

[0072]

[0073] Among them, E i represents the heavy field strength at the same height as the i-th auxiliary measurement point on the lightning channel; h i Represents the height of the i-th auxiliary measurement point; i=1, 2; H is the height of the lightning channel.

[0074] The auxiliary metering model also includes:

[0075] The voltage drop U of the surface lightning channel is:

[0076] exist Figure 2 A rectangular coordinate system is established at the point O shown.

[0077] dq=τdy

[0078]

[0079] Where τ is the charge density, C / m; ε0 is the dielectric constant; r0 is the distance from any point on the lightning channel to the first auxiliary measurement point, in meters.

[0080] The components on the x-axis are:

[0081]

[0082] For the above formula, we can unify the variables:

[0083]

[0084] Bring it into the dEx expression,

[0085]

[0086] Then integrate them,

[0087]

[0088] Similarly, we can get:

[0089]

[0090]

[0091] Using E x and E yThe expression of the electric field intensity E1 on the thundercloud channel is further simplified, at this time θ1=0, θ2=π:

[0092]

[0093] Thus, the relationship between the electric field E0 at the detection point and the electric field E1 on the wire is obtained:

[0094]

[0095] in

[0096]

[0097]

[0098] Where, E1 is the electric field strength on the lightning channel, kV / m; E0 is the electric field strength at the drone detection point, kV / m; H is the length of the lightning channel, m; h1 is the height of the detection point, m; r is the horizontal distance between the lightning channel and the drone detection point, m. h1 and h2 can be measured according to the altitude of the drone; r can be calculated according to the longitude and latitude of the drone and the longitude and latitude of the lightning strike point.

[0099] This scheme equates the near-ground thundercloud channel to a finite-length charged straight wire, and obtains the electric field intensity at any point in space based on Maxwell's equations and the differential element method.

[0100] By using the above method, the electric field E1 at the height h1 on the lightning channel and the electric field E2 at the height h2 on the lightning channel can be calculated; finally, the formula:

[0101]

[0102] Get the voltage U in the thundercloud channel.

[0103] This embodiment provides a new technical concept: the near-ground thundercloud channel is equivalent to a finite-length charged straight wire, and the electric field strength at any point in the space is obtained according to the Maxwell equations and the differential element method; through the above technical concept, this scheme determines the auxiliary measurement points and constructs an auxiliary measurement model of the lightning channel, and realizes the on-site direct measurement of the voltage drop of the lightning channel through the geometric relationship model between the auxiliary measurement points and the lightning channel, thereby improving the accuracy of the measurement results of the voltage drop of the near-ground lightning channel and the convenience of the measurement method.

[0104] Example 2

[0105] This embodiment provides a near-ground lightning channel voltage drop measurement system, which is used to implement a near-ground lightning channel voltage drop measurement method in embodiment 1. The system includes:

[0106] A model building module, used to determine auxiliary measurement points and build an auxiliary measurement model of the lightning channel; the auxiliary measurement model is a geometric relationship model between the auxiliary measurement points and the lightning channel when the lightning channel is equivalent to a charged straight wire of finite length;

[0107] Acquisition module, used to obtain parameters of auxiliary measurement points;

[0108] The calculation module is used to input the auxiliary measurement point parameters into the auxiliary measurement model to obtain the lightning channel voltage drop.

[0109] The acquisition module includes a drone array and a control center;

[0110] Each drone in the drone array includes: a drone body, an airborne control module, a laser radar three-dimensional imaging module, and an electric field measurement sensor module;

[0111] The airborne control module is used to adjust the position of the UAV according to the control instructions issued by the control center;

[0112] The laser radar three-dimensional imaging module is used to sense the three-dimensional space flight position of the drone;

[0113] The electric field measurement sensor module is suspended below the drone body and is used to sense electric field data;

[0114] The control center is used to obtain the electric field distribution of the auxiliary measurement point according to the three-dimensional spatial flight position of the UAV and the electric field data obtained by the UAV array, and the electric field distribution includes the position data and electric field data of the auxiliary measurement point.

[0115] The auxiliary measurement points include a first auxiliary measurement point and a second auxiliary measurement point;

[0116] The first auxiliary measurement point and the second auxiliary measurement point are both located on a vertical line A, and the vertical line A is parallel to the lightning channel.

[0117] The parameters of the auxiliary measurement points include:

[0118] The height h1 and field strength E of the first auxiliary measurement point 01 ;

[0119] The height h2 and field strength E of the second auxiliary measurement point 02 ;

[0120] The distance r between the vertical line A and the lightning channel.

[0121] The auxiliary measurement points include a first auxiliary measurement point and a second auxiliary measurement point;

[0122] The first auxiliary measurement point and the second auxiliary measurement point are both located on a vertical line A, and the vertical line A is parallel to the lightning channel.

[0123] The parameters of the auxiliary measurement points include:

[0124] The height h1 and field strength E of the first auxiliary measurement point 01 ;

[0125] The height h2 and field strength E of the second auxiliary measurement point 02 ;

[0126] The distance r between the vertical line A and the lightning channel.

[0127] The auxiliary metering model includes:

[0128]

[0129]

[0130]

[0131]

[0132] Among them, E i represents the heavy field strength at the same height as the i-th auxiliary measurement point on the lightning channel; h i Represents the height of the i-th auxiliary measurement point; i=1, 2; H is the height of the lightning channel; U is the surface lightning channel voltage drop.

[0133] The airborne control module adjusts the array distribution according to the flight position of the drone to bring it closer to the thundercloud; the laser radar three-dimensional imaging module senses the spatial flight position of the drone through the laser radar; the control center processes the data and generates an image of the thundercloud area. The electric field measurement sensor module is installed under the drone to form a spatial polyhedron array layout for measuring electric field data. The real-time electric field data obtained by the drone array is processed by the control center to obtain the electric field distribution.

[0134] Example 3

[0135] This embodiment provides a computer-readable medium having a computer program stored thereon. The computer program is executed by a processor to implement a method for measuring voltage drop in a near-ground lightning channel as described in Embodiment 1.

[0136] It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes. The schemes in the embodiments of the present invention may be implemented in various computer languages, for example, object-oriented programming language Java and literal scripting language JavaScript, etc.

[0137] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A lightning channel voltage drop measurement method, characterized in that: include: Determine auxiliary measurement points and construct an auxiliary measurement model of the lightning channel; the auxiliary measurement model is a geometric relationship model between the auxiliary measurement points and the lightning channel when the lightning channel is equivalent to a charged straight wire of finite length; The parameters of the auxiliary measurement points are obtained, and the parameters of the auxiliary measurement points are input into the auxiliary measurement model to obtain the lightning channel voltage drop.

2. A lightning channel voltage drop measurement method according to claim 1, characterized in that: The auxiliary measurement points include a first auxiliary measurement point and a second auxiliary measurement point; The first auxiliary measurement point and the second auxiliary measurement point are both located on a vertical line A, and the vertical line A is parallel to the lightning channel.

3. A lightning channel voltage drop measurement method according to claim 2, characterized in that: The parameters of the auxiliary measurement points include: The height h1 and field strength E of the first auxiliary measurement point 01 ; The height h2 and field strength E of the second auxiliary measurement point 02 ; The distance r between the vertical line A and the lightning channel.

4. A lightning channel voltage drop measurement method according to claim 3, characterized in that: The auxiliary metering model includes: Among them, E i represents the heavy field strength at the same height as the i-th auxiliary measurement point on the lightning channel; h i Indicates the height of the i-th auxiliary measurement point; i = 1, 2; H is the height of the lightning channel; θ1 indicates the angle between the line connecting the highest point of the lightning channel and the first auxiliary measurement point and the vertical line A; θ2 indicates the angle between the line connecting the highest point of the lightning channel and the second auxiliary measurement point and the vertical line A; U indicates the voltage drop of the surface lightning channel. .

5. A lightning channel voltage drop measurement system, characterized in that: A method for measuring voltage drop in a lightning channel according to any one of claims 1 to 4, the system comprising: A model building module, used to determine auxiliary measurement points and build an auxiliary measurement model of the lightning channel; the auxiliary measurement model is a geometric relationship model between the auxiliary measurement points and the lightning channel when the lightning channel is equivalent to a charged straight wire of finite length; Acquisition module, used to obtain parameters of auxiliary measurement points; The calculation module is used to input the auxiliary measurement point parameters into the auxiliary measurement model to obtain the lightning channel voltage drop.

6. A lightning channel voltage drop measurement system according to claim 5, characterized in that: The acquisition module includes a control center and a drone array; Each drone in the drone array includes: a drone body, an airborne control module, a laser radar three-dimensional imaging module, and an electric field measurement sensor module; The airborne control module is used to adjust the position of the UAV according to the control instructions issued by the control center; The laser radar three-dimensional imaging module is used to sense the three-dimensional space flight position of the drone; The electric field measurement sensor module is suspended below the drone body and is used to sense electric field data; The control center is used to obtain the electric field distribution of the auxiliary measurement point according to the three-dimensional spatial flight position of the UAV and the electric field data acquired by the UAV array, and the electric field distribution includes the position data and electric field data of the auxiliary measurement point.

7. A lightning channel voltage drop measurement system according to claim 6, characterized in that: The auxiliary measurement points include a first auxiliary measurement point and a second auxiliary measurement point; The first auxiliary measurement point and the second auxiliary measurement point are both located on a vertical line A, and the vertical line A is parallel to the lightning channel.

8. A lightning channel voltage drop measurement system according to claim 7, characterized in that: The parameters of the auxiliary measurement points include: The height h1 and field strength E of the first auxiliary measurement point 01 ; The height h2 and field strength E of the second auxiliary measurement point 02 ; The distance r between the vertical line A and the lightning channel.

9. A lightning channel voltage drop measurement system according to claim 8, characterized in that: The parameters of the auxiliary measurement point include: The auxiliary measurement model includes: Among them, E i represents the heavy field strength at the same height as the i-th auxiliary measurement point on the lightning channel; h i Represents the height of the i-th auxiliary measurement point; i=1, 2; H is the height of the lightning channel; θ1 represents the angle between the line connecting the highest point of the lightning channel and the first auxiliary measurement point and the vertical line A; θ2 represents the angle between the line connecting the highest point of the lightning channel and the second auxiliary measurement point and the vertical line A; U represents the surface lightning channel voltage drop.

10. A computer readable medium having a computer program stored thereon, characterized in that: The computer program is executed by a processor to implement a lightning channel voltage drop measurement method as described in any one of claims 1 to 4.

Images