CN115856708A - Cross interconnection grounding test method and system using coaxial cable - Google Patents
Cross interconnection grounding test method and system using coaxial cable Download PDFInfo
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Abstract
A cross-connect grounding test method and system using coaxial cables is characterized in that the method comprises the following steps: step 1, checking and confirming the connection relation between one end of each coaxial cable in the same joint well and two sides of a single-phase high-voltage cable joint and the connection relation between the other end of each coaxial cable and a cross interconnection grounding box; step 2, measuring the grounding circulation of the coaxial cable connected to any two-phase high-voltage cable in the three-phase high-voltage cables by utilizing the splayed coupling CT; and 3, calculating the grounding circulation of the single-phase high-voltage cable based on the measurement result of the step 2, and judging the grounding state of the single-phase cable based on the grounding circulation of the single-phase high-voltage cable. The method is simple and convenient, can be flexibly deployed, greatly improves the working efficiency of field maintenance personnel, and ensures the accuracy of the measurement result.
Description
Technical Field
The invention relates to the field of power systems, in particular to a cross-connection grounding test method and a cross-connection grounding test system by utilizing coaxial cables.
Background
At present, most of urban underground transmission lines are several kilometers or even dozens of kilometers, and in order to avoid the generation of overhigh circulating current of a cable metal sheath, the cable metal sheath cross transposition technology is generally adopted to inhibit the induced voltage of the metal sheath and reduce the circulating current. Because the operation environment of the cable is complex, the problems of multi-point grounding of the cable caused by water inflow of a grounding box, external protection layer breakage and the like often occur during operation, and the circulating current live test of the metal sheath of the cable needs to be carried out from the position of a single-core lead wire of a cross interconnection grounding system to master the operation state of the cable grounding system.
The positions of the traditional single-core lead of the cable are mainly the positions of a direct box lead, a copper plate of a grounding box and a cleat lead of a connector, and because the circuit is long, the test result of the grounding system for performing the circulation test on the coaxial cable by adopting the traditional method is not accurate enough, so that the potential safety hazard is easily brought to the circuit.
Background art document CN113640574A discloses an online monitoring device and a monitoring method for tunnel cable sheath grounding loop, wherein a first current transformer is installed at the ground of a high-voltage cable sheath grounding box or a cross interconnection box, each signal input channel of a current acquisition device acquires the grounding loop and the cable core current of the current sheath, analyzes and calculates the running state of a cable, and sends loop warning information based on that the digital grounding loop of the cable sheath is greater than the grounding loop threshold of the cable sheath.
Although the current transformer is disposed at the ground of the cross-connection box, in order to obtain a single-phase fault of the high-voltage cable, at least a plurality of current sensors need to be fixedly disposed on a plurality of phases of the high-voltage cable, which not only greatly increases the cost of the system, but also increases the complexity of the system. On the other hand, the measurement result can be used as an accurate index to represent whether the single-phase cable has a fault or not after operation and processing.
In addition, the connection lines between the cross-connect box and the high-voltage cables are relatively complex for various historical reasons. The deployment of multiple current transformers on each phase of the high voltage cable is only one ideal implementation. However, in the practical implementation process, for example, when the grounding box joint is covered by fireproof materials for historical reasons, such as fire hazard control, and the like, and is difficult to disassemble, it is difficult to add a current transformer in the connecting line. When the measurement possibility of multiple phases is lacked, and the measurement of the sheath layer circulation is realized by adopting a single CT (Current Transformer), the test value is the superposition of effective values of Current vectors of two cables of the coaxial cable, and is not the Current on the metal sheath of the single-phase cable actually, so the measurement error is larger. If the current transformer is connected at the positions of a direct grounding box lead, a grounding box copper plate, a connector claw and the like, the circuit of the measuring system is complex, and the measuring result is not accurate enough.
Further, even if the local maintenance personnel can observe the occurrence of the single-phase cable sheath layer fault from the appearance of the cable, the actual fault situation still needs to be known through multiple measurements. This detection method is not conducive to flexible and efficient fault measurement by field maintenance personnel.
In view of the above problems, a need exists for a novel cross-connect grounding test method and system using coaxial cables.
Disclosure of Invention
In order to solve the defects in the prior art, the invention provides a cross interconnection grounding test method and a system by utilizing coaxial cables, which realize the measurement of the grounding circulation of a non-fault phase by utilizing splayed coupling CT according to the connection structure of the coaxial cables between a single-phase high-voltage cable sheath layer lead and a cross interconnection grounding box, thereby judging the grounding state of the cables.
The invention adopts the following technical scheme.
The invention relates to a cross-connection grounding test method by utilizing coaxial cables, which comprises the following steps: step 1, checking and confirming the connection relation between one end of each coaxial cable in the same joint well and two sides of a single-phase high-voltage cable joint and the connection relation between the other end of each coaxial cable and a cross interconnection grounding box; step 2, measuring the grounding circulation of the coaxial cable connected to any two-phase high-voltage cable in the three-phase high-voltage cables by utilizing the splayed coupling CT; and 3, calculating the grounding circulation of the single-phase high-voltage cable based on the measurement result of the step 2, and judging the grounding state of the single-phase cable based on the grounding circulation of the single-phase high-voltage cable.
Preferably, the splayed coupling CT comprises two oppositely arranged magnetic induction rings; the first magnetic induction ring carries out electromagnetic induction on the first coaxial cable to generate first forward current or first forward voltage, and the second magnetic induction ring carries out electromagnetic induction on the second coaxial cable to generate second reverse current or second reverse voltage; the figure-of-eight coupling CT is used to achieve a superposition of the first forward current/voltage and the second reverse current/voltage.
Preferably, the output end of the splay coupling CT is connected with a measurement host computer to realize measurement of the output current or the output voltage of the splay coupling CT by the measurement host computer.
Preferably, the two adjacent phases are adjacent phases of the high-voltage cable which are judged preliminarily that no single-phase earth fault occurs, no single-phase cable sheath layer is damaged, and no single-phase cable cannot be measured.
Preferably, when the single-phase joint of the high-voltage cable is coated with the fireproof material, the single phase of the high-voltage cable is in a state that the single phase cannot be measured.
Preferably, the splayed coupling CT is an openable and closable structure; when the splayed coupling CT is in an open state, the splayed coupling CT can be unfolded into a magnetic material belt; when the splayed coupling CT is in a closed state, a first magnetic induction ring and a second magnetic induction ring which have the same cross-sectional area are formed.
Preferably, the cross section of the magnetic material strip is of a high-permeability core structure, and the magnetic material strip is made of a magnetic material.
Preferably, when the measurement result of step 2 is current superposition, the grounding circulation of the single-phase high-voltage cable is
Preferably, when the measurement result of step 2 is voltage superposition, the grounding circulation of the single-phase high-voltage cable is
In a second aspect, the invention relates to a cross-connect grounding test system using coaxial cables, the system being adapted to implement the steps of the method of the first aspect of the invention.
Compared with the prior art, the cross interconnection grounding test method and system using the coaxial cable have the beneficial effects that the splayed coupling CT is used for measuring the grounding circulation of the non-fault phase according to the wiring structure of the coaxial cable in the cross interconnection grounding system of the cable grounding system, so that the grounding state of the cable is judged. The method is simple and convenient, can be flexibly deployed, greatly improves the working efficiency of field maintenance personnel, and ensures the accuracy of the measurement result.
The beneficial effects of the invention also include:
1. the invention adopts the openable and closable design of the splayed coupling CT to replace a plurality of current transformers fixed in a test system. The design method greatly simplifies the process of testing circuits and data analysis and processing, saves a large amount of cost for fixing the current transformer, and simultaneously ensures the working efficiency of field maintenance personnel.
2. The method can obtain the single-phase cable condition only by single measurement and does not need multiple measurements, thereby not only facilitating the measurement, but also completely eliminating the system error in the multiple measurement process and improving the accuracy of the measurement result. In addition, when the single-phase fault is very definite, the measurement mode is more flexible and efficient.
3. When the problems that a current transformer is difficult to arrange on a single-phase coaxial cable due to various historical reasons or other problems that direct testing is difficult to achieve, such as outer protective layer damage and the like, exist, the conversion measuring method can achieve measurement of a non-fault phase and directly output a measuring result.
4. The method flexibly applies kirchhoff's law and electromagnetic induction law, so that the measurement result and the actual grounding circulation current to be judged are in a simple proportional relation. Furthermore, in the method of the invention, the simple proportional relation between the measurement result and the grounding circulation current in a single phase is confirmed through the derivation process, so that the error caused by the alternating current angle deviation of each phase current when a plurality of phases are superposed does not exist in the measurement result, and the one-to-one corresponding relation between the maximum amplitude of the measurement result and the maximum amplitude of the grounding circulation current is ensured. Therefore, the calculation and processing processes are greatly reduced, and the system configuration is simplified.
Drawings
Fig. 1 is a system configuration diagram of a cross-connect grounding test method using coaxial cables according to the present invention;
fig. 2 is a schematic diagram of testing a splay-coupled CT in a cross-connect grounding test method using coaxial cables according to the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. The described embodiments of the invention are only some, not all embodiments of the invention. All other embodiments of the invention that are not described in the present application and are obtained by the embodiments of the invention described in the present application without creative efforts should be included in the protection scope of the present application by those of ordinary skill in the art.
In a first aspect, the present invention relates to a cross-connect grounding test method using coaxial cables, the method comprising steps 1 to 3.
Step 1, checking and confirming the connection relation between one end of each coaxial cable in the same joint well and two sides of a single-phase high-voltage cable joint and the connection relation between the other end of each coaxial cable and a cross interconnection grounding box.
Fig. 1 is a system configuration diagram of a cross-connect grounding test method using coaxial cables according to the present invention. In the present invention, as shown in fig. 1, the connection between the high voltage cable sheath lead and the cross connection box can be realized by using a coaxial cable. In the prior art, in order to prevent the circulation abnormality of the sheath layer of the high-voltage cable, it is necessary to realize the connection by cross-connecting the ground boxes. There are also measures for this connection in the prior art.
Specifically, for each of the three phases of the high voltage cable ABC, there would be two end leads of the cable jacket layer in the joint well of the cable. The lead wires of each phase high-voltage cable are connected to different wires in one end of a corresponding coaxial cable. And the other end of the coaxial cable is led to the nearest cross interconnection grounding box, so that the cross interconnection grounding of the sheath layer lead is realized.
For historical reasons, the connection system of the cross-connected grounding box is earlier than the prior art which adopts the measurement technology of the circulating current of the current transformer on each coaxial cable. In the case of multiple maintenance or improvement of the cross-linked grounding box, various problems may exist in practical applications, such as the above-mentioned joints are fixedly wound with fireproof materials which are difficult to remove, and the like. This makes it difficult to properly install the current transformer at a desired position.
In order to solve the problems, the invention needs to check the accuracy and the effectiveness of the connection mode of the coaxial cable before measurement is realized. The inspection mode can be manual inspection realized by a maintenance person going to a joint well where the high-voltage cable is located and a cross interconnection grounding box on site. Of course, if there is a corresponding monitoring platform, the checking method may also be to monitor or monitor the effectiveness of the wire connection method through various remote monitoring systems.
On the basis, the invention also provides the following solution for realizing the detection of the circulating current of the cable sheath layer in the wiring mode.
And 2, measuring the grounding circulation of the coaxial cable connected to any two-phase high-voltage cable in the three-phase high-voltage cables by utilizing the splayed coupling CT.
In the invention, splayed coupling CT is selected to replace a plurality of current transformers so as to realize the test of the grounding circulation on the coaxial cable.
Fig. 2 is a schematic diagram illustrating a testing of a splay-coupled CT in a cross-connect grounding test method using coaxial cables according to the present invention. As shown in fig. 2, preferably, the splay-coupled CT includes two oppositely disposed magnetic induction rings; the first magnetic induction ring carries out electromagnetic induction on the first coaxial cable to generate first forward current or first forward voltage, and the second magnetic induction ring carries out electromagnetic induction on the second coaxial cable to generate second reverse current or second reverse voltage; the figure-eight coupling CT is used to achieve a superposition of the first forward current/voltage and the second reverse current/voltage.
It is understood that the figure-of-eight coupled CT in the present invention can be designed flexibly. It is not necessarily fixedly disposed in the circuit in which the coaxial cable is located. As shown in fig. 2, the splay-coupled CT is an openable and closable structure; when the splayed coupling CT is in an open state, the splayed coupling CT can be unfolded into a magnetic material belt; when the splayed coupling CT is in a closed state, a first magnetic induction ring and a second magnetic induction ring with the same cross-sectional area are formed.
In other words, the splay-coupled CT can be carried around by cable maintenance personnel, and when a single-phase fault is found or it is desired to measure and determine the single-phase fault, the CT device can be taken at any time and measured for the corresponding phase. The fixed current transformer is completely replaced, and the problem that the fixed current transformer is difficult to install in the practical application process is solved.
Preferably, the cross section of the magnetic material strip is of a high-permeability core structure, and the magnetic material strip is made of a magnetic material.
In order to ensure that the CT measurement result is accurate and reliable and can fully realize electromagnetic induction, the magnetic material belt can be designed by adopting a high-magnetic-permeability core structure.
In the actual measurement process, the relation between the three ABC phases of the high-voltage cable can be considered, if in the three ABC phases, field maintenance personnel actually want to measure the grounding fault condition of the A-phase sheath layer, the splayed coupling CT can be sequentially wound on two non-fault adjacent phases, namely the B phase and the C phase. By this measuring method, the splayed coupled CT of the present invention can measure the first forward current/voltage and the second reverse current/voltage. And because the two magnetic induction rings of the splayed coupling CT have the same sectional area, the forward voltage/current and the reverse voltage/current are actually superposed, so that the superposed voltage or current is obtained and directly output.
Preferably, the two adjacent phases are adjacent phases of the high-voltage cable which are judged preliminarily that no single-phase earth fault occurs, no single-phase cable sheath layer is damaged, and no single-phase cable cannot be measured.
According to kirchhoff's law, in a power system, the sum of lead currents of a sheath layer of a three-phase high-voltage cable is 0 due to the action of a cross grounding box.
In addition, if a three-phase high-voltage cable is arrangedThe sheath layer current is respectively
、/>
、/>
If the coaxial cable of the phase A is arranged in the first magnetic induction ring and the coaxial cable of the phase C is arranged in the second magnetic induction ring, the actual core-through current in the magnetic induction rings can be obtained as
By simplifying equation (1), the core-through current is
（2）；
General formula of kirchhoff's law
When the value is substituted into the formula (2), the amplitude of the through-core current is ^ 4>
(ii) a It can be seen that the present invention enables the fault condition of a single faulted phase to be obtained by a single measurement.
Due to the law of electromagnetic induction, when the splay coupling CT has constant other parameters such as shape, the core-through current and the magnitude of the current or voltage output by induction are in a direct proportion relationship. In this way, the actual magnitude of the ground circulating current can be further obtained.
By the mode, when the conditions of single-phase earth fault, single-phase cable sheath layer damage, single-phase incapability of measurement and the like are preliminarily judged by field maintenance personnel, flexible CT access and measurement are carried out.
The preliminary judgment refers to judgment which is carried out in other ways without adopting the measuring way of the invention, and the judgment can comprise detection of the appearance of the cable sheath layer by naked eyes, and can also comprise preliminary conclusions obtained after acquisition of relevant data in a power grid, and the like. However, these determinations are all indirect determinations of the wiring state of the cable sheath layer relative to the method of the present invention, and are classified as preliminary determinations.
Preferably, when the single-phase joint of the high-voltage cable is coated with the fireproof material, the single phase of the high-voltage cable is in a state that the single phase cannot be measured.
It is understood that the reasons for the single-phase being unmeasurable as described above may be various, and the present invention is described only by taking as an example a current transformer in which a single-phase joint is covered with a fireproof material, so that the current transformer cannot be disassembled or fixed. In practice, any single phase unmeasured condition that may also be protected may be included within this range.
Preferably, the output end of the splay coupling CT is connected with a measurement host computer to realize measurement of the output current or the output voltage of the splay coupling CT by the measurement host computer.
It can be understood that the output end of the splay-coupled CT in the present invention is connected to the measurement host. The measurement host can implement the calculation of the measurement voltage or the measurement current so as to judge the measurement result. This part will be described in detail in step 3.
And 3, calculating the grounding circulation of the single-phase high-voltage cable based on the measurement result of the step 2, and judging the grounding state of the single-phase cable based on the grounding circulation of the single-phase high-voltage cable.
Preferably, when the measurement result of step 2 is current superposition, the grounding circulation of the single-phase high-voltage cable is
Preferably, when the measurement result of step 2 is voltage superposition, the grounding circulation of the single-phase high-voltage cable is
It can be understood that the current inductance and the voltage inductance in the present invention can be obtained in advance according to the characteristic parameters of the splay-coupled CT, for example, by obtaining the proportional relationship between the core-through current, the output voltage and the output current of the coupled CT through a preliminary test, so as to obtain the above-mentioned inductances. Since the above-mentioned acquisition method belongs to the prior art in the field of electromagnetic induction, it is not described herein.
In the invention, after the grounding circulation is obtained through calculation, the size of the grounding circulation can be judged. In a standard power system, according to the requirements of normative documents such as "design specifications of power engineering cables", when the grounding circulating current is less than 50A, the cable is judged to be normal, and if the grounding circulating current is between 50 and 100A, the cable is judged to be abnormal, and further maintenance is required. If the voltage is more than 100A, the single-phase cable is judged to be in a defect state, and operations such as cutting are needed.
Compared with the mode in the prior art, the coupling CT is sequentially installed on every two cables with the same axis of the high-voltage cable cross-connection grounding system, the output induced voltage or induced current of the secondary coil of the CT is tested, the circulation current of each branch of the high-voltage cable cross-connection grounding system is calculated and obtained by applying kirchhoff law and electromagnetic induction law, the state of the cable cross-connection grounding system is judged by detecting the circulation current, a cross-connection grounding box does not need to be disassembled, and the method is convenient to operate, high in efficiency and good in application prospect.
An embodiment provided in the present invention is specifically described for the above grounding test method. The invention carries out cross interconnection grounding test on a certain high-voltage cable cross interconnection grounding system from the coaxial cable.
Firstly, one end of each coaxial cable of the same connector well is checked and confirmed to be effectively connected to two sides of a single-phase high-voltage cable connector, and the other end of each coaxial cable is connected to the cross-connection grounding box.
And secondly, measuring the grounding circulation of the coaxial cables of two adjacent phases by utilizing the splayed coupling CT. In the process, the splayed coupling CT secondary output lead wire can be connected with a measurement host, the splayed coupling CT is sequentially arranged on any two-phase coaxial cables in the high-voltage cable cross interconnection grounding system, and the splayed coupling CT secondary coil is tested to output an induced current signal.
Specifically, this example performed three measurements in sequence, and obtained three measurement results, which are as follows:
installing the splayed coupling CT on the same-axis cables of the A and B high-voltage cable cross-connection grounding systems, and testing the effective value of the induced current output by the splayed coupling CT secondary coil
Is 1.641A;
installing the splayed coupling CT on the cables with the same axes of the B and C of the high-voltage cable cross-connection grounding system, and testing the effective value of the induced current output by the splayed coupling CT secondary coil
Is 4.593A;
installing the splayed coupling CT on the cables with the same axes of the C and A of the high-voltage cable cross-connection grounding system, and testing the effective value of the induced current output by the splayed coupling CT secondary coil
Was found to be 3.028A.
After obtaining the test results, the implementationAnd calculating and obtaining the circular current of each branch of the high-voltage cable cross interconnection grounding system by applying kirchhoff law and electromagnetic induction law. Specifically, the current of the cross-connection grounding system passing through the grounding grid of the direct grounding box is 0, and the three-phase branch currents of the cross-connection grounding system are respectively 0
、/>
、/>
If yes, then there is->
And respectively deducing the expressions of sheath layer currents corresponding to the three measurement results as follows:
wherein ,
the ratio of the proper amplitude of the output current of the splay-coupled CT to the feedthrough current, i.e., the current inductance, is dimensionless. The calculation is performed for equation (5), resulting in:
after calculation, the state of the circulating current of the cable grounding system is judged, and the condition I = MAX { | A |, | IB |, | IC | } = IB < 50A is adopted to judge that the cable grounding system is normal.
In a second aspect, the invention relates to a cross-connect grounding test system using coaxial cables, the system being adapted to implement the steps of the method of the first aspect of the invention.
It can be understood that the measurement host used in the present invention can be connected to the output end of the splay-coupled CT, and collects and processes the corresponding output result.
It is understood that, in order to implement each function in the method provided in the embodiments of the present application, the measurement host includes a hardware structure and/or a software module corresponding to the execution of each function. Those of skill in the art will readily appreciate that the present application is capable of hardware or a combination of hardware and computer software implementing the various illustrative algorithm steps described in connection with the embodiments disclosed herein. Whether a function is performed as hardware or computer software drives hardware depends upon the particular application and design constraints imposed on the solution. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present application.
It should be noted that, since the process of measurement and calculation in the present invention is greatly simplified, the performance requirement for the measurement host is significantly reduced compared to the prior art.
The cross interconnection grounding test method and the system have the beneficial effects that compared with the prior art, the cross interconnection grounding test method and the system utilizing the coaxial cables realize the measurement of the grounding circulation of the non-fault phase by utilizing the splayed coupling CT according to the connection structure of the coaxial cables between the lead of the single-phase high-voltage cable sheath layer and the cross interconnection grounding box, so that the cable grounding state of the fault phase is judged. The method is simple and convenient, can be flexibly deployed, greatly improves the working efficiency of field maintenance personnel, and ensures the accuracy of the measurement result.
Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and not for limiting the same, and although the present invention is described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: modifications and equivalents may be made to the embodiments of the invention without departing from the spirit and scope of the invention, which is to be covered by the claims.
Claims (10)
1. A cross-connect grounding test method using coaxial cables, the method comprising the steps of:
step 1, checking and confirming the connection relation between one end of each coaxial cable in the same joint well and two sides of a single-phase high-voltage cable joint and the connection relation between the other end of each coaxial cable and a cross interconnection grounding box; step 2, measuring the grounding circulation of the coaxial cable connected to any two-phase high-voltage cable in the three-phase high-voltage cables by utilizing the splayed coupling CT;
and 3, calculating the grounding circulation of the single-phase high-voltage cable based on the measurement result of the step 2, and judging the grounding state of the single-phase cable based on the grounding circulation of the single-phase high-voltage cable.
2. A cross-connect grounding test method using coaxial cables as claimed in claim 1, wherein:
the splayed coupling CT comprises two magnetic induction rings which are arranged in opposite directions;
the first magnetic induction ring performs electromagnetic induction on the first coaxial cable to generate first forward current or first forward voltage, and the second magnetic induction ring performs electromagnetic induction on the second coaxial cable to generate second reverse current or second reverse voltage;
the figure-of-eight coupled CT is used to realize the superposition of a first forward current/voltage and a second reverse current/voltage.
3. A cross-connect grounding test method using coaxial cables as claimed in claim 2, wherein:
the output end of the splayed coupling CT is connected with a measurement host machine so as to realize the measurement of the output current or the output voltage of the splayed coupling CT by the measurement host machine.
4. A cross-connect grounding test method using coaxial cables as claimed in claim 3, wherein: and the two adjacent phases are adjacent phases of the high-voltage cable which are judged preliminarily that no single-phase earth fault occurs, no single-phase cable sheath layer is damaged, and no single-phase cable can not be measured.
5. A cross-connect grounding test method using coaxial cables as claimed in claim 4, wherein:
when the single-phase joint of the high-voltage cable is coated by the fireproof material, the single phase of the high-voltage cable is in a state that the single phase cannot be measured.
6. A cross-connect grounding test method using coaxial cables as claimed in claim 3, wherein:
the splayed coupling CT is an openable structure; and the number of the first and second electrodes,
when the splayed coupling CT is in an open state, the splayed coupling CT can be unfolded to be a magnetic material belt;
when the splayed coupling CT is in a closed state, a first magnetic induction ring and a second magnetic induction ring with the same cross-sectional area are formed.
7. A cross-connect grounding test method using coaxial cables as claimed in claim 6, wherein:
the cross section of the magnetic material strip is of a high-magnetic-conductivity core structure, and the magnetic material strip is made of magnetic conductive materials.
8. A cross-connect grounding test method using coaxial cables as claimed in claim 2, wherein:
when the measurement result of the step 2 is current superposition, the grounding circulation of the single-phase high-voltage cable is
wherein ,
the current inductance of the splayed coupling CT;
9. A cross-connect grounding test method using coaxial cables according to claim 2, characterized in that:
when the measurement result of the step 2 is voltage superposition, the grounding circulation of the single-phase high-voltage cable is
wherein ,
voltage inductance of the splay-coupled CT; />
10. A cross-connect grounding test system using coaxial cables, characterized in that:
the system is adapted to implement the steps of the method of any one of claims 1 to 9.
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