Method for generating single-core cable cross interconnection simulation time domain reflection waveform

Abstract

The invention discloses a method for generating a single-core cable cross interconnection simulation time domain reflection waveform, and belongs to the technical field of cable fault simulation. The method is characterized by comprising the following steps: step a, setting waveform simulation parameters, and preprocessing the parameters; b, generating a transmitting pulse array P [] according to the simulation parameters set in the step a; c, generating a corresponding cross interconnection array Cr [] according to the simulation parameters set in the step a; step d, generating a simulation waveform array Rr [] reflected by the full length L of the cable according to the simulation parameters set in the step a; and e, adding the arrays in the steps b-d to obtain a final display waveform array W []. Through the generation method of the single-core cable cross interconnection simulation time domain reflection waveform, the length of the cable and the cross interconnection length and number can be randomly set, different waveform data can be generated, and the training requirements of testers can be met.

Description

Technical Field

[0001] The invention discloses a method for generating a single-core cable cross-connection simulation time domain reflection waveform, belonging to the technical field of cable fault simulation. Background Art

[0002] Because the voltage level of ultra-high voltage single-core cable is too high, the cable sheath is generally grounded by cross-connection to limit the induced voltage to a safe range. The identification and analysis of power cable fault ranging waveforms is an important part of cable fault detection technology, and it can easily become a difficulty in cable fault testing. Therefore, simulation training for ultra-high voltage single-core cable faults is an important means to train relevant technical personnel.

[0003] In the prior art, time domain reflection method is a method commonly used to measure low resistance, short circuit and open circuit faults of cables. At the same time, time domain reflection method can also be used to measure the length of cables, the propagation speed of electromagnetic in cables, and to distinguish the middle head, T-type joint and terminal head of cables. The basic principle of time domain reflection method is: during the test, a pulse signal is injected into the cable, and the pulse propagates along the cable to the impedance mismatch point, such as the short circuit point, the fault point, the middle joint, etc. The pulse is reflected and sent back to the measurement point to be recorded by the instrument. By analyzing the time characteristics of the signal, the distance of these impedance mismatch points can be obtained.

[0004] When using the time domain reflection method to measure a single-core cable with cross-connections, it is difficult to make fault judgments directly through the waveform due to the reflection of the cross-connection part. In order to strengthen the training of testers, a method based on the principle of traveling wave ranging is designed to simulate and generate time domain reflection waveforms of ultra-high voltage single-core cables with cross-connections. This technical solution to meet the training needs of testers has become an urgent problem to be solved in this field. Summary of the invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a method for generating a single-core cable cross-connection simulated time domain reflection waveform that can arbitrarily set the cable length and the length and number of cross-connections to generate different waveform data to meet the training needs of test personnel.

[0006] The technical solution adopted by the present invention to solve the technical problem is: the method for generating a single-core cable cross-connection simulation time domain reflection waveform is characterized by comprising the following steps:

[0007] Step a, setting the parameters of waveform simulation and performing parameter preprocessing. The parameters of waveform simulation include the total length of the cable L, the low-resistance fault distance L 低 , the distance of cross-connection L c and number s;

[0008] Step b, generating a transmission pulse array P_s[] according to the simulation parameters set in step a;

[0009] Step c, generating a corresponding cross-connection array C_r[] according to the simulation parameters set in step a;

[0010] Step d, generating a simulation waveform array R_r[] of the reflection of the full length L of the cable according to the simulation parameters set in step a;

[0011] Step e, adding the arrays in steps b to d to obtain the final display waveform array W[].

[0012] Preferably, in step a, when performing parameter preprocessing, the process includes: calculating the distance P of the cross-connected reflected pulses in the overall waveform array. C :

[0013]

[0014] And calculate the distance P of the full-length reflected pulse of the cable in the overall waveform array 全 :

[0015]

[0016] Where, L represents the total length of the cable, L c It represents the distance of cross-connection, V is the cable wave velocity, and T is a constant, which represents the time required to collect one point.

[0017] Preferably, in step a, when performing parameter preprocessing, the process includes: obtaining the intermediate value X of the waveform numerical value generated by simulation m :

[0018]

[0019] Among them, X i Indicates the minimum value of the waveform generated by the simulation, X a Indicates the maximum value of the waveform generated by the simulation.

[0020] Preferably, in step b, the transmitting pulse array is X p When the generated transmit pulse array P_s[X p ] is calculated as:

[0021] P_s[X p ]=X m +X1*sin((deg2rad(360 / P F )*X P ))

[0022] Among them, X mIndicates the middle value of the waveform generated by simulation, P F Indicates the total number of transmitted pulse arrays, X p is a variable, representing the transmitted pulse array, with a value of 0 to P F X1 is a constant, and its calculation formula is: X1 = X m *(e (F*G) ), F and G represent pulse width and gain respectively.

[0023] Preferably, in step c, the waveform value X generated by simulation C The cross-connect array C_r[X C ]for:

[0024] C_r[X c ]=X m +(e -(a*L) *X1*sin((deg2rad(360 / P cc )*(X c -P c ))))

[0025] Among them, X m Indicates the middle value of the waveform generated by simulation, P c Indicates the distance of the cross-connected reflected pulse in the overall waveform array. Xc is a variable, which means the distance of the reflected pulse in the overall waveform array. Its value is P c <X c <P c +P cc , a represents the inverse of the gain G, L represents the total length of the cable, X1 is a constant and the calculation formula is: X1 = X m *(e (F*G) ), F and G represent pulse width and gain respectively, P cc It represents the distance of the reflected pulse in the overall waveform array when the length of the cross-connection segment is 6 meters, and a represents the inverse of the gain G.

[0026] Preferably, in step d, the transmitting pulse array is X R When the reflection simulation array R_r[X R ]for:

[0027] R_r[X R ]=X m +X1*sin((deg2rad(180 / P F )(X P -P 全 )))

[0028] Among them, X R is a variable, and its value range is: 全 <XR <P 全 +P F , X1 is a constant, and its calculation formula is: X1=X m *(e (F*G) ), F and G represent pulse width and gain respectively, Xp is a variable representing the transmit pulse array, with a value of 0 to P F , P F Indicates the total number of transmitted pulse arrays.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] By means of the method for generating a single-core cable cross-connection simulation time domain reflection waveform, the length of the cable and the length and number of the cross-connections can be set at will, and different waveform data can be generated to meet the training requirements for test personnel.

[0031] In the method for generating time domain reflection waveforms for single-core cable cross-connection simulation, based on the principle of the traveling wave method, the reflection coefficient from the traveling wave to the impedance mismatch point is considered, and the subsequent reflection pulses are simulated. Different time domain reflection waveforms are simulated and generated according to different cable lengths, cross-connection lengths and numbers.

[0032] In the method for generating a time domain reflection waveform for a single-core cable cross-connection simulation, the fact that the reflection pulse width of an actual time domain reflection instrument is different in different ranges is taken into consideration, and the pulse width of the simulated transmission pulse data is also different in different ranges. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Flowchart of a method for generating time domain reflection waveforms for single-core cable cross-connect simulation.

[0034] Figure 2 Actual waveform diagram of the time domain reflection waveform simulated for a single-core cable cross-connect.

[0035] Figure 3 Simulation waveform diagram of time domain reflection waveform for single-core cable cross-connection simulation. DETAILED DESCRIPTION

[0036] Figures 1 to 3 The best embodiment of the present invention is shown below in conjunction with the attached Figures 1 to 3 The present invention is further described.

[0037] like Figure 1 As shown, a method for generating a single-core cable cross-connection simulation time domain reflection waveform (hereinafter referred to as the generation method) includes the following steps:

[0038] Step 1001, setting simulation parameters;

[0039] Set the parameters of waveform simulation, including the total cable length L and the low-resistance fault distance L 低 , the distance of cross-connection L c and number s.

[0040] Step 1002, obtaining the distance of the reflected pulse in the overall waveform array;

[0041] According to the simulation parameters set in step 1001, according to the number and distance of the cross-connections set, the distance P of the reflected pulse of the cross-connections in the overall waveform array is calculated. C :

[0042]

[0043] Among them, L c It represents the distance of cross-connection, V is the cable wave velocity, and T is a constant, which represents the time required to collect one point.

[0044] According to the set cable length, calculate the distance P of the full-length reflected pulse of the cable in the overall waveform array. 全 :

[0045]

[0046] Where L is the total length of the cable, V is the cable wave velocity, and T is a constant representing the time required to collect one point.

[0047] Step 1003, obtaining the waveform value generated by simulation;

[0048] According to the minimum value X of the waveform generated by simulation i The maximum value X of the waveform generated by the simulation a , calculate the intermediate value X of the waveform generated by the simulation m :

[0049]

[0050] Step 1004, generating a transmit pulse array;

[0051] According to the simulation parameters set in step 1001, a transmission pulse array P_[] is generated. The transmission pulse array is X p When the pulse array P_s[X p ] is calculated as:

[0052] P_s[X p ]=X m +X1*sin((deg2rad(360 / P F )*X P ))

[0053] Among them, X m Indicates the middle value of the waveform generated by simulation, P F Indicates the total number of transmitted pulse arrays, X p is a variable, representing the transmitted pulse array, with a value of 0 to P F X1 is a constant, and its calculation formula is: X1 = X m *(e (F*G) ), F and G represent the pulse width and gain respectively. When the gain increases, the time domain reflection waveform of the single-core ultra-high voltage cable with cross-connection generated by simulation will become larger as a whole.

[0054] Step 1005, generating a cross-connect array;

[0055] According to the simulation parameters set in step 1001, the corresponding cross-connection array C_r[] is generated, and the waveform value X generated by the simulation is C The cross-connect array C_r[X C ]for:

[0056] C_r[X c ]=X m +(e -(a*L) *X1*sin((deg2rad(360 / P cc )*(X c -P c ))))

[0057] Among them, X m Indicates the middle value of the waveform generated by simulation, P c It represents the distance of the cross-connected reflected pulse in the overall waveform array, a represents the inverse of the gain G, Xc is a variable, which means the distance of the reflected pulse in the overall waveform array, and its value is P c <X c <P c +P cc , L represents the total length of the cable, and X1 is a constant. The actual length of the cross-connection segment is generally 6 to 7 meters. In this generation method, it is assumed that the length of the cross-connection segment is 6 meters, P cc Indicates the distance of the reflected pulse in the overall waveform array when the length of the cross-connection segment is 6 meters:

[0058]

[0059] Where V is the cable wave velocity and T is the time required to collect one point.

[0060] When multiple cross-connections are set, the simulation generates the same array as above, but the reflection coefficient e - ( a*L ) will decrease accordingly. e -(a*L)It is related to the distance of the cross-connection. The longer the distance, the higher the reflection coefficient e. -(a*L) Similarly, the algorithm will also consider the secondary reflection or multiple reflection of the cross-connection, generate its secondary reflection or multiple reflection array, and its reflection coefficient will also be reduced.

[0061] Step 1006, generating a simulation waveform array of full-length reflection of the cable;

[0062] According to the cable length L set in step 1001, a simulation waveform array R_r[] of the reflection of the full length of the cable is generated. This array simulates and generates a pulse reflected by the full length of the cable. The overall pulse length is basically the same as the transmitted pulse, and the length is P F , the starting point of the full-length reflected pulse is P 全 The transmit pulse array is X R When the entire cable length reflection simulation array R_r[X R ]for:

[0063] R_r[X R ]=X m +X1*sin((deg2rad(180 / P F )(X P -P 全 )))

[0064] The low-resistance fault waveform array can also be further simulated to obtain the set one, namely:

[0065] R_r[X R ]=X m +X1*sin((deg2rad(-180 / P F )(X P -P 全 )))

[0066] Among them, X R is a variable, and its value range is: 全 <X R <P 全 +P F , X1 is a constant, and its calculation formula is: X1=X m *(e (F*G) ), F and G represent pulse width and gain respectively.

[0067] Step 1007, obtaining the final display waveform array;

[0068] Add the arrays in steps 1004 to 1006 to obtain the final display waveform array W[], and the transmission pulse array is X W When the final display waveform array W[X W ]for:

[0069] W[X W ]=P_s[X P ]+C_r[X c ]+R_r[X R ]

[0070] Among them, P_s[X p ] is the transmitting pulse array X p The transmit pulse array, C_r[X C ] is the waveform value X C When the cross-connected array, R_r[X R ] is the transmitting pulse array X R The entire cable length reflection simulation array is shown. W is a variable, with a value between 0 and X W <P 全 +P F .

[0071] The final data W[X W ] is displayed in the display interface to obtain the final simulated waveform.

[0072] like Figure 2 The figure below shows the waveform of a real single-core cable with cross-connections collected using an actual time domain reflectometer. This cable has two cross-connections. Figure 2 The arrow a in the middle indicates the transmitting pulse, the arrow b indicates the first cross-interconnection reflection waveform, the arrow c indicates the second cross-interconnection reflection waveform, and the arrow d indicates the full-length reflection. Figure 3 It is a simulation graph generated by using the above steps 1001 to 1007. Figure 2 , Figure 3 The X-axis represents the distance in meters (m). The scale of the X-axis is related to the wave speed. When the wave speed is 200m / us, one scale is 1. The Y-axis represents the amplitude, which is a real number. Figures 2-3 In the example, each tick mark on the Y axis is 1.

[0073] Depend on Figure 3 and Figure 2 By comparison, the pulse width of the transmitted pulse is basically the same, and the full-length reflection and cross-interconnection reflection distances of the two waveforms are consistent. Figure 2 The measured waveform has small fluctuations in the straight line segment because the measured cable impedance does not match the point. Figure 3 The simulated waveform has no fluctuations and is a constant straight line segment. However, the waveform generated by the simulation is basically similar to the measured waveform in the cross-connection and full-length reflection parts. Therefore, the simulated waveform generated by this generation method can meet the requirements of test training.

[0074] The above is only a preferred embodiment of the present invention, and does not limit the present invention in other forms. Any technician familiar with the profession may use the above disclosed technical content to change or modify it into an equivalent embodiment with equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the technical solution of the present invention still belongs to the protection scope of the technical solution of the present invention.

Claims

1. A method for generating a single-core cable cross-connection simulation time domain reflection waveform, characterized in that: The steps include: Step a, setting the parameters of waveform simulation and performing parameter preprocessing. The parameters of waveform simulation include the total length of the cable L, the low-resistance fault distance L 低 , the distance of cross-connection L c and number s; Step b, generating a transmission pulse array P_s[] according to the simulation parameters set in step a; Step c, generating a corresponding cross-connection array C_r[] according to the simulation parameters set in step a; Step d, generating a simulation waveform array R_r[] of the reflection of the full length L of the cable according to the simulation parameters set in step a; Step e, adding the arrays in steps b to d to obtain the final display waveform array W[].

2. The method for generating a single-core cable cross-connection simulation time domain reflection waveform according to claim 1, characterized in that: In step a, when performing parameter preprocessing, it includes: calculating the distance P of the cross-connected reflected pulse in the overall waveform array C : And calculate the distance P of the full-length reflected pulse of the cable in the overall waveform array 全 : Where, L represents the total length of the cable, L c It represents the distance of cross-connection, V is the cable wave velocity, and T is a constant, which represents the time required to collect one point.

3. The method for generating a single-core cable cross-connection simulation time domain reflection waveform according to claim 1, characterized in that: In step a, when performing parameter preprocessing, it includes: obtaining the intermediate value X of the waveform numerical value generated by simulation m : Among them, X i Indicates the minimum value of the waveform generated by the simulation, X a Indicates the maximum value of the waveform generated by the simulation.

4. The method for generating a single-core cable cross-connection simulation time domain reflection waveform according to claim 1, characterized in that: In step b, the transmit pulse array is X p When the generated transmit pulse array P_s[X p ] is calculated as: P_s[X p ]=X m +X1*sin((deg2rad(360 / P F )*X P )) Among them, X m Indicates the middle value of the waveform generated by simulation, P F Indicates the total number of transmitted pulse arrays, X p is a variable, representing the transmitted pulse array, with a value of 0 to P F X1 is a constant, and its calculation formula is: X1 = X m *(e (F*G) ), F and G represent pulse width and gain respectively.

5. The method for generating a single-core cable cross-connection simulation time domain reflection waveform according to claim 1, characterized in that: In step c, the waveform value X generated by simulation C The cross-connect array C_r[X C ]for: C_r[X c ]=X m +(e -(a*L) *X1*sin((deg2rad(360 / P cc )*(X c -P c )))) Among them, X m Indicates the middle value of the waveform generated by simulation, P c Indicates the distance of the cross-connected reflected pulse in the overall waveform array. Xc is a variable, which means the distance of the reflected pulse in the overall waveform array. Its value is P c <X c <P c +P cc , a represents the inverse of the gain G, L represents the total length of the cable, X1 is a constant and the calculation formula is: X1 = X m *(e (F*G) ), F and G represent pulse width and gain respectively, P cc It represents the distance of the reflected pulse in the overall waveform array when the length of the cross-connection segment is 6 meters, and a represents the inverse of the gain G.

6. The method for generating a single-core cable cross-connection simulation time domain reflection waveform according to claim 1, characterized in that: In step d, the transmit pulse array is X R When the reflection simulation array R_r[X R ]for: R_r[X R ]=X m +X1*sin((deg2rad(180 / P F )(X P -P 全 ))) Among them, X R is a variable, and its value range is: 全 <X R <P 全 +P F , X1 is a constant, and its calculation formula is: X1=X m *(e (F *G) ), F and G represent pulse width and gain respectively, Xp is a variable representing the transmit pulse array, with a value of 0 to P F , P F Indicates the total number of transmitted pulse arrays.

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