Station cable test method

Abstract

The invention provides a station cable test method, which comprises the following steps: acquiring reflection coefficients and transmission coefficients of a to-be-tested cable and a reference cable, and establishing respective transmission functions including amplitude-frequency response and phase-frequency response; and comparing the transmission function of the to-be-tested cable with the transmission function of the reference cable, and calculating amplitude-frequency response change and phase-frequency response change so as to judge the performance state of the to-be-tested cable. The reference cable can be a new cable, an aged cable or a damaged cable, and determining whether the to-be-tested cable is good in performance, aged or damaged or not according to the comparison result and a preset threshold value. The performance of the cable for the transformer substation can be effectively evaluated, and stable operation of a power system is guaranteed.

Description

Technical Field

[0001] The invention relates to the field of power electronics technology and energy conversion technology, and in particular to a station cable testing method. Background Art

[0002] In substations, substation cables serve as a bridge connecting various devices and systems. Their performance status plays a vital role in the stability and safety of the entire system. Cables not only bear the heavy responsibility of power transmission, but also are responsible for the transmission of information. They are an indispensable part of smart grids and modern communication networks. However, with the continuous development of power systems and the advancement of smart grids, the use environment of cables is becoming increasingly complex, and problems such as cable aging and damage are becoming increasingly prominent, posing huge challenges to the stable operation of the system. Summary of the invention

[0003] The purpose of the present invention is to provide a substation cable testing method, which can effectively evaluate the performance of substation cables and ensure the stable operation of the power system.

[0004] To achieve the above object, the present invention provides a station cable testing method, comprising:

[0005] Acquire the reflection coefficient and transmission coefficient of the cable to be tested, and establish a transmission function of the cable to be tested according to the reflection coefficient and transmission coefficient of the cable to be tested, including an amplitude-frequency response and a phase-frequency response;

[0006] Acquire the reflection coefficient and transmission coefficient of the reference cable, and establish the transmission function of the reference cable according to the reflection coefficient and transmission coefficient of the reference cable, including amplitude-frequency response and phase-frequency response;

[0007] The transmission function of the cable to be tested is compared with the transmission function of the reference cable, and the amplitude-frequency response change and the phase-frequency response change of the cable to be tested relative to the reference cable are determined according to the comparison result;

[0008] The cable test result is obtained according to the amplitude-frequency response change and the phase-frequency response change.

[0009] Preferably, the amplitude-frequency response represents the gain or attenuation of the cable at different frequencies as follows:

[0010] H(f)=|S21| / (1-|S11| 2 )

[0011] Where H(f) is the amplitude of the transmission function at frequency f, |S21| is the amplitude of the transmission coefficient, and |S11| is the amplitude of the reflection coefficient.

[0012] Preferably, the phase frequency response represents the phase variation of the cable at different frequencies as follows:

[0013] φ(f)=∠S21-∠S11

[0014] Where φ(f) is the phase of the transmission function at frequency f, ∠S21 is the phase of the transmission coefficient, and |S11| is the phase of the reflection coefficient.

[0015] Preferably, the reference cable is a new cable, an aged cable or a damaged cable of the same model as the cable to be tested. The new cable refers to a cable that has not been put into use, the aged cable refers to a cable whose performance has degraded due to long-term use or environmental factors, and the damaged cable refers to a cable whose performance has changed due to physical damage.

[0016] Preferably, comparing the transmission function of the cable to be tested with the transmission function of the reference cable, and determining the amplitude-frequency response change and phase-frequency response change of the cable to be tested relative to the reference cable according to the comparison result, comprises:

[0017] Compare the amplitude-frequency response and phase-frequency response of the cable under test and the reference cable at the same frequency point;

[0018] Calculate the amplitude-frequency response change ΔH(f)=H_test(f)-H_new(f); where H_test(f) is the amplitude-frequency response of the cable to be tested, and H_reference(f) is the amplitude-frequency response of the reference cable;

[0019] Calculate the phase-frequency response change Δφ(f)=φ_test(f)-φ_reference(f); wherein φ_test(f) is the phase-frequency response of the cable to be tested, and φ_reference(f) is the phase-frequency response of the reference cable.

[0020] Preferably, obtaining the cable test result according to the amplitude-frequency response change and the phase-frequency response change includes:

[0021] When the reference cable is a new cable, if ΔH(f) is less than the first amplitude-frequency response threshold and Δφ(f) is less than the first phase-frequency response threshold, the performance of the cable to be tested is good; if ΔH(f) is greater than or equal to the first amplitude-frequency response threshold and Δφ(f) is greater than or equal to the first phase-frequency response threshold, the performance of the cable to be tested is degraded.

[0022] Preferably, obtaining the cable test result according to the amplitude-frequency response change and the phase-frequency response change includes:

[0023] When the reference cable is an aged cable, if ΔH(f) is less than or equal to the second amplitude-frequency response threshold or Δφ(f) is less than or equal to the second phase-frequency response threshold, the cable to be tested is aged; if ΔH(f) is greater than the second amplitude-frequency response threshold and Δφ(f) is greater than the second phase-frequency response threshold, the cable to be tested is not aged.

[0024] Preferably, obtaining the cable test result according to the amplitude-frequency response change and the phase-frequency response change includes:

[0025] When the reference cable is a damaged cable, if ΔH(f) is less than or equal to the third amplitude-frequency response threshold or Δφ(f) is less than or equal to the third phase-frequency response threshold, the cable to be tested is damaged; if ΔH(f) is greater than the third amplitude-frequency response threshold and Δφ(f) is greater than the third phase-frequency response threshold, the cable to be tested is not damaged.

[0026] The present invention has the following beneficial effects:

[0027] By accurately measuring and comparing the reflection coefficient and transmission coefficient of the cable, the present invention can more accurately evaluate the performance status of the cable, including whether it is aged or damaged, and can detect problems at an early stage of cable performance degradation, so that maintenance or replacement measures can be taken in advance to avoid sudden failures. Based on this, regular testing of station cables can help ensure the stable operation of the cable system and reduce power system failures caused by cable problems. By promptly discovering and handling cable problems, it can reduce the wider range of damage and higher maintenance costs caused by cable failures. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required in the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0029] Figure 1 The present invention is a block diagram of a method for testing a station cable according to an embodiment of the present invention. DETAILED DESCRIPTION

[0030] The detailed description of the accompanying drawings is intended as an illustration of the current embodiments of the present invention and is not intended to represent the only form in which the present invention can be implemented. It should be understood that the same or equivalent functions can be accomplished by different embodiments that are intended to be included in the spirit and scope of the present invention.

[0031] See also Figure 1 , an embodiment of the present invention provides a station cable testing method, comprising:

[0032] Step S10, obtaining the reflection coefficient and transmission coefficient of the cable to be tested, and establishing a transmission function of the cable to be tested according to the reflection coefficient and transmission coefficient of the cable to be tested, including an amplitude-frequency response and a phase-frequency response;

[0033] Specifically, the test cable is measured using test equipment such as a network analyzer. The reflection coefficient represents the ratio of the signal reflected from the input end of the cable to the input signal, while the transmission coefficient represents the transmission efficiency of the signal through the cable. Based on the measured reflection coefficient and transmission coefficient, the transmission function of the cable to be tested can be calculated. The transmission function is a mathematical model that describes the signal transmission characteristics of the cable at different frequencies. The transmission function consists of two parts: amplitude-frequency response and phase-frequency response:

[0034] Amplitude-frequency response (H(f)): indicates the gain or attenuation of the cable at different frequencies;

[0035] Phase-frequency response (φ(f)): Indicates the phase change of the cable at different frequencies.

[0036] Step S20, obtaining a reflection coefficient and a transmission coefficient of a reference cable, and establishing a transmission function of the reference cable according to the reflection coefficient and the transmission coefficient of the reference cable, including an amplitude-frequency response and a phase-frequency response;

[0037] Specifically, similar to step S10, this step is to measure the reflection coefficient and transmission coefficient of the reference cable and establish the transmission function of the reference cable.

[0038] Step S30, comparing the transmission function of the cable to be tested with the transmission function of the reference cable, and determining the amplitude-frequency response change and phase-frequency response change of the cable to be tested relative to the reference cable according to the comparison result;

[0039] Specifically, by comparison, the amplitude frequency response change ΔH(f) and the phase frequency response change Δφ(f) of the tested cable relative to the reference cable are calculated.

[0040] Step S40, obtaining a cable test result according to the amplitude-frequency response change and the phase-frequency response change;

[0041] Specifically, by comparing with a reference cable, it can be determined whether the cable under test has performance degradation, aging or damage.

[0042] Furthermore, the amplitude-frequency response indicates the gain or attenuation of the cable at different frequencies, as shown below:

[0043] H(f)=|S21| / (1-|S11| 2 )

[0044] Where H(f) is the amplitude of the transmission function at frequency f, |S21| is the amplitude of the transmission coefficient, and |S11| is the amplitude of the reflection coefficient;

[0045] Specifically, through this formula, we can calculate the transmission characteristics of the cable at different frequencies, which is crucial for evaluating the performance of the cable. For example, if the value of H(f) drops significantly within a certain frequency range, this may indicate that the cable has loss or damage within this frequency range. By comparing the amplitude-frequency response of the new cable and the cable to be tested, it can be determined whether the performance of the cable to be tested has degraded.

[0046] Furthermore, the phase frequency response represents the phase variation of the cable at different frequencies as shown below:

[0047] φ(f)=∠S21-∠S11

[0048] Where φ(f) is the phase of the transmission function at frequency f, ∠S21 is the phase of the transmission coefficient, and |S11| is the phase of the reflection coefficient.

[0049] Specifically, the measurement of phase-frequency response is very important for evaluating the phase stability of the cable and determining the propagation characteristics of the signal in the cable. In high-speed data transmission and precision measurement applications, the phase-frequency response test is essential because it can help identify phase offset problems that may cause signal distortion. By comparing the phase-frequency response of a new cable and the cable to be tested, it can be further determined whether the cable to be tested has performance degradation or damage.

[0050] Furthermore, the reference cable is a new cable, an aged cable or a damaged cable of the same model as the cable to be tested. The new cable refers to a cable that has not been put into use, the aged cable refers to a cable whose performance has degraded due to long-term use or environmental factors, and the damaged cable refers to a cable whose performance has changed due to physical damage.

[0051] Specifically, a new cable refers to a cable that has not been put into use. Its performance should be in the best condition and it has not experienced any form of performance degradation or damage. As a reference standard, the new cable can be used to compare the performance of the cable to be tested in its brand new state. By comparing the performance with the new cable, it can be determined whether the cable to be tested has maintained the performance level at the time of leaving the factory.

[0052] An aged cable is a cable whose performance has degraded due to long-term use or environmental factors (such as temperature, humidity, chemical corrosion, ultraviolet radiation, etc.). The transmission characteristics and electrical parameters of an aged cable will change over time, usually manifested as increased impedance, increased transmission loss, and decreased insulation performance. Comparing the performance of the cable to be tested with the aged cable can help determine whether the cable to be tested has experienced similar performance degradation.

[0053] A damaged cable refers to a cable whose performance has changed due to physical damage (such as mechanical damage, extrusion, cutting, thermal damage, etc.). A damaged cable may show significant performance degradation at a specific frequency, such as increased reflection coefficient, increased transmission loss, etc. By comparing the performance with that of the damaged cable, it can be determined whether the cable to be tested has suffered physical damage.

[0054] During the test, it is crucial to choose the right reference cable because the performance of the reference cable will directly affect the accuracy and reliability of the test results. The following are the scenarios for using different types of reference cables:

[0055] New cable as reference: used to determine whether the cable under test maintains the performance standards when it leaves the factory;

[0056] Aged cable as reference: used to evaluate whether the cable under test has similar performance degradation;

[0057] Damaged cable as reference: Used to detect if the cable under test has suffered physical damage.

[0058] Through this comparison method, the performance status of the tested cable can be evaluated more accurately, so that corresponding maintenance or replacement measures can be taken to ensure the stable operation of the power system.

[0059] Further, comparing the transmission function of the cable to be tested with the transmission function of the reference cable, and determining the amplitude-frequency response change and phase-frequency response change of the cable to be tested relative to the reference cable according to the comparison result, includes:

[0060] Compare the amplitude-frequency response and phase-frequency response of the cable under test and the reference cable at the same frequency point;

[0061] Calculate the amplitude-frequency response change ΔH(f)=H_test(f)-H_new(f); where H_test(f) is the amplitude-frequency response of the cable to be tested, and H_reference(f) is the amplitude-frequency response of the reference cable;

[0062] Calculate the phase-frequency response change Δφ(f)=φ_test(f)-φ_reference(f); wherein φ_test(f) is the phase-frequency response of the cable to be tested, and φ_reference(f) is the phase-frequency response of the reference cable.

[0063] Further, obtaining the cable test result according to the amplitude-frequency response change and the phase-frequency response change includes:

[0064] When the reference cable is a new cable, if ΔH(f) is less than the first amplitude-frequency response threshold and Δφ(f) is less than the first phase-frequency response threshold, the performance of the cable under test is good; if ΔH(f) is greater than or equal to the first amplitude-frequency response threshold and Δφ(f) is greater than or equal to the first phase-frequency response threshold, the performance of the cable under test is degraded.

[0065] Specifically, when the reference cable is a new cable, ΔH(f) is the difference in amplitude-frequency response between the cable to be tested and the new cable at the same frequency, that is, the change in the amplitude of the transmission function, which indicates the difference in transmission efficiency between the cable to be tested and the new cable.

[0066] Δφ(f) is the difference in phase-frequency response between the cable under test and the new cable at the same frequency, that is, the change in the phase of the transmission function. It indicates the difference in signal phase change between the cable under test and the new cable.

[0067] The first amplitude-frequency response threshold is a preset threshold used to determine whether the amplitude-frequency response change is within an acceptable range. If ΔH(f) is less than this threshold, it is considered that the amplitude-frequency response of the tested cable does not change much and has good performance.

[0068] The first phase-frequency response threshold is a preset threshold used to determine whether the phase-frequency response change is within an acceptable range. If Δφ(f) is less than this threshold, it is considered that the phase-frequency response of the tested cable does not change much and has good performance.

[0069] When the reference cable is a new cable, if ΔH(f) is less than the first amplitude-frequency response threshold, it is considered that the amplitude-frequency response performance of the cable to be tested at this frequency point is good; if ΔH(f) is greater than or equal to the first amplitude-frequency response threshold, it is considered that the amplitude-frequency response performance of the cable to be tested at this frequency point is degraded; if Δφ(f) is less than the first phase-frequency response threshold, it is considered that the phase-frequency response performance of the cable to be tested at this frequency point is good; if Δφ(f) is greater than or equal to the first phase-frequency response threshold, it is considered that the phase-frequency response performance of the cable to be tested at this frequency point is degraded.

[0070] Based on the test results of amplitude-frequency response and phase-frequency response, if ΔH(f) and Δφ(f) of the cable under test at all test frequency points are less than the corresponding thresholds, it can be determined that the overall performance of the cable under test is good. If ΔH(f) or Δφ(f) at any frequency point exceeds the threshold, it is considered that the performance of the cable under test has deteriorated and may need maintenance or replacement.

[0071] Further, obtaining the cable test result according to the amplitude-frequency response change and the phase-frequency response change includes:

[0072] When the reference cable is an aged cable, if ΔH(f) is less than or equal to the second amplitude-frequency response threshold or Δφ(f) is less than or equal to the second phase-frequency response threshold, the cable to be tested is aged; if ΔH(f) is greater than the second amplitude-frequency response threshold and Δφ(f) is greater than the second phase-frequency response threshold, the cable to be tested is not aged.

[0073] Specifically, when the cable to be tested is a new cable, ΔH(f) is the difference in amplitude-frequency response between the cable to be tested and the aged cable at the same frequency, that is, the change in the amplitude of the transmission function, which reflects the difference in transmission efficiency between the cable to be tested and the aged cable; Δφ(f) is the difference in phase-frequency response between the cable to be tested and the aged cable at the same frequency, that is, the change in the phase of the transmission function, which reflects the difference in signal phase change between the cable to be tested and the aged cable.

[0074] The second amplitude-frequency response threshold is a preset threshold used to determine whether the amplitude-frequency response change of the tested cable indicates cable aging. If ΔH(f) is less than or equal to this threshold, it may indicate that the cable is aged.

[0075] The second phase-frequency response threshold is a preset threshold used to determine whether the phase-frequency response change of the tested cable indicates cable aging. If Δφ(f) is less than or equal to this threshold, it may indicate that the cable is aged.

[0076] When the reference cable is an aged cable, if ΔH(f) is less than or equal to the second amplitude-frequency response threshold, it is considered that the amplitude-frequency response of the cable to be tested at this frequency point indicates that the cable may be aged; if ΔH(f) is greater than the second amplitude-frequency response threshold, it is considered that the amplitude-frequency response of the cable to be tested at this frequency point does not indicate that the cable is aged; if Δφ(f) is less than or equal to the second phase-frequency response threshold, it is considered that the phase-frequency response of the cable to be tested at this frequency point indicates that the cable may be aged; if Δφ(f) is greater than the second phase-frequency response threshold, it is considered that the phase-frequency response of the cable to be tested at this frequency point does not indicate that the cable is aged.

[0077] Based on the test results of amplitude-frequency response and phase-frequency response, if the ΔH(f) and Δφ(f) of the cable under test at all test frequency points are less than or equal to the corresponding threshold, it can be determined that the cable under test has aged. If the ΔH(f) and Δφ(f) of any frequency point are greater than the corresponding threshold, it is considered that the cable under test has not aged.

[0078] This method can effectively identify the degree of cable aging by comparing the performance parameters of the cable to be tested with those of a known aged cable, thereby providing a basis for cable maintenance and replacement.

[0079] Further, obtaining the cable test result according to the amplitude-frequency response change and the phase-frequency response change includes:

[0080] When the reference cable is a damaged cable, if ΔH(f) is less than or equal to the third amplitude-frequency response threshold or Δφ(f) is less than or equal to the third phase-frequency response threshold, the cable to be tested is damaged; if ΔH(f) is greater than the third amplitude-frequency response threshold and Δφ(f) is greater than the third phase-frequency response threshold, the cable to be tested is not damaged.

[0081] Specifically, when the reference cable is a damaged cable, ΔH(f) is the difference in amplitude-frequency response between the cable to be tested and the damaged cable at the same frequency, that is, the change in the amplitude of the transmission function, which indicates the difference in transmission efficiency of the cable to be tested relative to the damaged cable; Δφ(f) is the difference in phase-frequency response between the cable to be tested and the damaged cable at the same frequency, that is, the change in the phase of the transmission function, which indicates the difference in signal phase change of the cable to be tested relative to the damaged cable.

[0082] The third amplitude-frequency response threshold is a preset threshold used to determine whether the amplitude-frequency response change of the cable to be tested indicates that the cable is damaged. If ΔH(f) is less than or equal to this threshold, it may indicate that the cable is damaged. The third phase-frequency response threshold is a preset threshold used to determine whether the phase-frequency response change of the cable to be tested indicates that the cable is damaged. If Δφ(f) is less than or equal to this threshold, it may indicate that the cable is damaged.

[0083] When the reference cable is a damaged cable, if ΔH(f) is less than or equal to the third amplitude-frequency response threshold, it is considered that the amplitude-frequency response of the cable to be tested at this frequency point indicates that the cable may be damaged; if ΔH(f) is greater than the third amplitude-frequency response threshold, it is considered that the amplitude-frequency response of the cable to be tested at this frequency point does not indicate that the cable is damaged; if Δφ(f) is less than or equal to the third phase-frequency response threshold, it is considered that the phase-frequency response of the cable to be tested at this frequency point indicates that the cable may be damaged; if Δφ(f) is greater than the third phase-frequency response threshold, it is considered that the phase-frequency response of the cable to be tested at this frequency point does not indicate that the cable is damaged.

[0084] Based on the test results of amplitude-frequency response and phase-frequency response, if the ΔH(f) and Δφ(f) of the cable under test at all test frequency points are less than or equal to the corresponding threshold, it can be determined that the cable under test is damaged. If the ΔH(f) and Δφ(f) of any frequency point are greater than the corresponding threshold, the cable under test is considered to be undamaged.

[0085] This method can effectively identify whether the cable has suffered physical damage by comparing the performance parameters of the cable to be tested with those of a cable with known damage, thereby providing decision support for cable repair or replacement.

[0086] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The selection of terms used herein is intended to best explain the principles of the embodiments, practical applications, or technical improvements in the market, or to enable other persons of ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. A station cable testing method, characterized in that: include: Acquire the reflection coefficient and transmission coefficient of the cable to be tested, and establish a transmission function of the cable to be tested according to the reflection coefficient and transmission coefficient of the cable to be tested, including an amplitude-frequency response and a phase-frequency response; Acquire the reflection coefficient and transmission coefficient of the reference cable, and establish the transmission function of the reference cable according to the reflection coefficient and transmission coefficient of the reference cable, including amplitude-frequency response and phase-frequency response; The transmission function of the cable to be tested is compared with the transmission function of the reference cable, and the amplitude-frequency response change and the phase-frequency response change of the cable to be tested relative to the reference cable are determined according to the comparison result; The cable test result is obtained according to the amplitude-frequency response change and the phase-frequency response change.

2. The method according to claim 1, characterized in that: The amplitude-frequency response shows the gain or attenuation of the cable at different frequencies as shown below: H(f)=|S21| / (1-|S11| 2 ) Where H(f) is the amplitude of the transmission function at frequency f, |S21| is the amplitude of the transmission coefficient, and |S11| is the amplitude of the reflection coefficient.

3. The method according to claim 1, characterized in that The phase frequency response shows the phase variation of the cable at different frequencies as shown below: φ(f)=∠S21-∠S11 Where φ(f) is the phase of the transmission function at frequency f, ∠S21 is the phase of the transmission coefficient, and |S11| is the phase of the reflection coefficient.

4. The method according to claim 1, characterized in that: The reference cable is a new cable, an aged cable or a damaged cable of the same model as the cable to be tested. The new cable refers to a cable that has not been put into use, the aged cable refers to a cable whose performance has degraded due to long-term use or environmental factors, and the damaged cable refers to a cable whose performance has changed due to physical damage.

5. The method according to claim 4, characterized in that The step of comparing the transmission function of the cable to be tested with the transmission function of the reference cable, and determining the amplitude-frequency response change and the phase-frequency response change of the cable to be tested relative to the reference cable according to the comparison result, comprises: Compare the amplitude-frequency response and phase-frequency response of the cable under test and the reference cable at the same frequency point; Calculate the amplitude-frequency response change ΔH(f)=H_test(f)-H_new(f); where H_test(f) is the amplitude-frequency response of the cable to be tested, and H_reference(f) is the amplitude-frequency response of the reference cable; Calculate the phase-frequency response change Δφ(f)=φ_test(f)-φ_reference(f); wherein φ_test(f) is the phase-frequency response of the cable to be tested, and φ_reference(f) is the phase-frequency response of the reference cable.

6. The method according to claim 5, characterized in that The obtaining of the cable test result according to the amplitude-frequency response change and the phase-frequency response change comprises: When the reference cable is a new cable, if ΔH(f) is less than the first amplitude-frequency response threshold and Δφ(f) is less than the first phase-frequency response threshold, the performance of the cable to be tested is good; if ΔH(f) is greater than or equal to the first amplitude-frequency response threshold and Δφ(f) is greater than or equal to the first phase-frequency response threshold, the performance of the cable to be tested is degraded.

7. The method according to claim 5, characterized in that The obtaining of the cable test result according to the amplitude-frequency response change and the phase-frequency response change comprises: When the reference cable is an aged cable, if ΔH(f) is less than or equal to the second amplitude-frequency response threshold or Δφ(f) is less than or equal to the second phase-frequency response threshold, the cable to be tested is aged; if ΔH(f) is greater than the second amplitude-frequency response threshold and Δφ(f) is greater than the second phase-frequency response threshold, the cable to be tested is not aged.

8. The method according to claim 5, characterized in that The obtaining of the cable test result according to the amplitude-frequency response change and the phase-frequency response change comprises: When the reference cable is a damaged cable, if ΔH(f) is less than or equal to the third amplitude-frequency response threshold or Δφ(f) is less than or equal to the third phase-frequency response threshold, the cable to be tested is damaged; if ΔH(f) is greater than the third amplitude-frequency response threshold and Δφ(f) is greater than the third phase-frequency response threshold, the cable to be tested is not damaged.

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