Power cable training simulation system based on multiple time scales

Abstract

The present invention proposes a power cable training simulation system based on multiple time scales. Based on three-dimensional virtual simulation, multiple time scales are used to expand various operation operating conditions. The operation conditions of the digital power grid are selected according to the operation requirements, including: the identification of power cables is simulated by the steady-state calculation model of the digital power grid, and the detection of the main insulation fault of the power cable is simulated by the transient calculation model of the digital power grid. This solves the problem that the traditional power cable operation simulation training does not take into account the actual power grid operation conditions, and the training personnel cannot truly feel the technical application results and usage skills in the operation, maintenance, inspection and test of the power cable.

Description

Technical Field

[0001] The invention relates to the fields of power training tools and virtual reality technology, and in particular to a power cable training simulation system based on multiple time scales. Background Art

[0002] Power cables are the carriers of power transmission. With the rapid development of clean energy in the country, the reliability of power cables used for ultra-high voltage, high voltage, medium voltage and low voltage has become increasingly important. Power workers need to continuously strengthen the skills training of power cable operation and maintenance, testing and inspection, and installation of various accessories. In response to the requirements of power workers for skill training in this area, corresponding power cable simulation tools have been developed.

[0003] Traditional power cable simulation tools are mainly offline learning methods such as playing video recordings or applying electronic courseware, or visiting training sites and work sites. Current power cable simulation tools use 3D virtual simulation technology to identify cables, detect power cable faults, and install various accessories. The installation of power cable accessories is carried out offline. According to the steps and requirements of the State Grid accessory installation, a 3D virtual operation scene can be established for trainers, and trainers can be guided to perform correct operations.

[0004] However, the existing technology only uses three-dimensional technology for offline power cable simulation development, which cannot enable trainees to truly experience the technical application results and usage skills in the operation, maintenance, inspection and test of power cables.

[0005] However, cable identification is carried out under the condition of power transmission, and must be correct, otherwise it will directly affect personal safety and equipment safety. There are many methods for cable identification, such as power frequency induction method, audio induction method and pulse current method, all of which involve the working state when the power system is in steady state operation. Similarly, when detecting the main insulation fault of the power cable, the three types of faults, open circuit fault, low resistance fault and high resistance fault, all involve transient operation analysis of the power system. Summary of the invention

[0006] In view of the defects and shortcomings of the prior art, the present invention proposes a power cable training simulation system based on multiple time scales to solve the problem that traditional power cable operation simulation training does not take into account the actual power grid operation conditions and cannot enable trainees to truly experience the technical application results and usage skills in the operation, maintenance, inspection and test of power cables.

[0007] Considering that cable identification is carried out under the condition of power transmission, it must be correct, otherwise it will directly affect personal safety and equipment safety. There are many methods for cable identification, such as power frequency induction method, audio induction method and pulse current method. These methods all involve the working state when the power system is in steady state operation. Similarly, when detecting the main insulation fault of the power cable, the three types of faults, open circuit fault, low resistance fault and high resistance fault, all involve transient operation analysis of the power system.

[0008] The present invention expands the three-dimensional virtual simulation used in the power cable operation skill training to multiple operating conditions, constructs the digital power grid required for training, and selects the operating conditions of the digital power grid according to the operation requirements. This expansion of multiple operating conditions using multiple time scales.

[0009] The present invention specifically adopts the following technical solutions:

[0010] A power cable training simulation system based on multiple time scales is characterized by: based on three-dimensional virtual simulation, multiple time scales are used to expand various operating conditions, and the operating conditions of the digital power grid are selected according to the operating requirements, including: the identification of power cables is simulated by the steady-state calculation model of the digital power grid, and the detection of power cable main insulation faults is simulated by the transient calculation model of the digital power grid.

[0011] Furthermore, the steady-state calculation model of the digital power grid starts from static voltage stability and performs analysis and identification based on power system flow calculation, and the step length of the simulation calculation is in seconds.

[0012] Furthermore, taking power cables as training objects, we select line types, transformer types, generator types, switch types and load types to construct all digital power grids for training, and the modeling is as follows:

[0013] (1) Mathematical model of the generator set

[0014] The mathematical model of the generator set in steady-state operation is represented by two variables:

[0015] Method 1: The active power P and terminal voltage U are given, and the corresponding reactive power limit is given at the same time, that is, the maximum and minimum reactive power allowed to be emitted;

[0016] Method 2: Active power P and reactive power Q emitted;

[0017] (2) Transformer parameters and mathematical model

[0018] 1) Parameters and mathematical model of double-winding transformer

[0019] There are two types of transformer equivalent circuits, namely, Γ-type equivalent circuit and T-type equivalent circuit. In power system calculations, the approximate equivalent circuit of a double-winding transformer moves the excitation branch to the power supply side to form a Γ-type equivalent circuit.

[0020] 2) Parameters and mathematical model of three-winding transformer

[0021] When the winding capacities on the three sides are different, the rated capacity of the transformer is the rated capacity of the winding with the largest capacity on the high-voltage side; the second short-circuit test is carried out according to the rated current of the winding with the smallest capacity: first, the short-circuit loss needs to be converted to the value when the short-circuit test is carried out according to the rated capacity of the transformer; the rated current of the winding is proportional to its rated capacity, the short-circuit loss is proportional to the square of the current, and the short-circuit voltage is proportional to the current;

[0022] (3) Parameters and mathematical models of power lines

[0023] The power line model in the steady-state analysis of the power system uses the total resistance, reactance, susceptance, and conductance of each phase of the entire line to identify their equivalent circuits;

[0024] (4) Load model

[0025] In the steady-state analysis of the power system, the mathematical model of the load is identified by given active power and reactive power. The static characteristics of the load need only be taken into account when high calculation accuracy is required.

[0026] Furthermore, in the three-dimensional operation application, training simulations of various identification methods for power cables are provided, including: simulations of power frequency induction method, audio frequency induction method, and pulse current method.

[0027] Furthermore, based on the transient calculation model of the digital power grid, in the power cable transient detection training simulation, the transient simulation calculation can be allowed to run for any length of time to cooperate with the operation of the trainers; the electromagnetic transient simulation of the power system is equivalent to the determination of the time domain response of the dynamic system, including the mathematical model of the system itself and the corresponding numerical algorithm, and its mathematical model includes two parts: one is the constraint equations determined by the network topology of the system, namely the KCL and KVL equations; the other is the volt-ampere relationship equations determined by the characteristics of each component in the system; modeling the electromagnetic transient of the power system is to describe the characteristics of each component in the system using mathematical expressions, and finally express the power grid model in the form of node voltage equations.

[0028] Furthermore, line class, transformer class, bus class, generator class, circuit breaker class and load class are selected to construct all digital power grids for training, among which the modeling of circuit breaker class and line class is as follows:

[0029] (1) Circuit breaker model

[0030] 1) Circuit breaker model without considering dynamic characteristics

[0031] The circuit breaker uses the resistance insertion method to simulate the opening and closing operation, always keeping the node numbers at both ends of the circuit breaker unchanged, inserting a small resistor when the switch is closed, and inserting a large resistor when the switch is open; so that the admittance matrix can be modified when switching without changing the topological structure of the network;

[0032] The resistance switching when the circuit breaker is opened is performed when the current of the first opening circuit passes through zero after receiving the trip command;

[0033] 2) Circuit breaker model considering dynamic characteristics

[0034] The insertion resistance is corrected by simulating arc characteristics to simulate the circuit breaker breaking process: the arc resistance simulates the function of time and is fitted by an exponential function;

[0035] (2) Transmission line model

[0036] 1) Concentrated parameter model

[0037] Adopt π-node equivalent circuit model;

[0038] 2) Transmission line model considering resistance loss

[0039] For transmission lines that take losses into account, the concentrated parameter resistance approximation method is applied. The transmission line is divided into several small sections, and resistance is inserted in series between each small section for approximation.

[0040] Furthermore, in the transmission line model considering resistance loss, the line is divided into two sections, R / 4 is connected in series at both ends, and R / 2 is connected in series in the middle, that is, a concentrated resistance line model.

[0041] Furthermore, it also includes off-line operating conditions for simulating off-line installation and production of cable accessories.

[0042] Furthermore, it includes a learning mode, a practice mode and an assessment mode.

[0043] Furthermore, in the practice mode and assessment mode, multiple cables on the identified line are mixed or buried underground to increase the difficulty of identification for trainees; open circuit faults, low-resistance faults or high-resistance faults are pre-buried so that trainees can see the circuit or voltage waveform of the line and perform high-frequency partial discharge fault detection; with a virtual simulation module, trainees can experience the grid changes caused by their own operations from the operating conditions of the digital power grid; in the assessment mode, the line flow transfer status in the digital power grid is used to check whether the cables identified by the trainees are correct; the line fault point calculated in the digital power grid is used to check whether the cable main insulation fault point detected by the trainees deviates, and the degree of deviation.

[0044] The present invention and its preferred embodiment establish a high-fidelity training environment for power grid production and related practitioners based on operation, maintenance and test detection of the overall power grid and three-dimensional operation site, and provide a means of assessment that is closer to the actual network environment for the correctness of the training personnel's operations, thereby better improving the power cable operation skills of power grid company employees.

[0045] For example, the following functions can be achieved through the design of this system:

[0046] 1. When cable identification is required in operating conditions, various settings can be made for the identified lines in the digital power grid operating in steady-state conditions, and multiple cables on the identified lines can be mixed or buried underground to increase the identification difficulty for trainees.

[0047] 2. When detecting main insulation faults in power cables, various settings can be made for the lines under test in the digital power grid operating under transient conditions, pre-embed open circuit faults, low resistance faults or high resistance faults, so that trainees can see the circuit or voltage waveform of the line and perform high-frequency partial discharge fault detection.

[0048] 3. The establishment of a digital power grid increases the effect of virtual training simulation, allowing trainees to experience the changes in the power grid caused by their own operations from the operating conditions of the digital power grid, such as watching the flow transfer and waveform changes before and after a fault occurs on the digital power grid.

[0049] 4. By establishing a digital power grid, the assessment means of power cable operation skill training has been increased. The line flow transfer status in the digital power grid can be used to verify whether the cable identified by the trainees is correct; the line fault point calculated in the digital power grid can be used to verify whether the cable main insulation fault point detected by the trainees is deviated, and the degree of deviation.

[0050] It has established a high-fidelity training environment for power grid production and related practitioners for operation, maintenance and test inspection based on the overall power grid and three-dimensional operation site, and provided a means of assessing whether the trainees' operations are correct, thereby better improving the power cable operation skills of State Grid Corporation employees. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:

[0052] Figure 1 This is a schematic diagram of the instructor's operation before line identification in the digital power grid according to an embodiment of the present invention, wherein the left figure shows the state before the operation, and the right figure shows the state after the operation, the line switches to hot standby, and the power flow is transferred.

[0053] Figure 2 The embodiment of the present invention simulates a trainer identifying a route schematic diagram in a three-dimensional scene.

[0054] Figure 3 This is a schematic diagram of a line fault in a digital power grid according to an embodiment of the present invention.

[0055] Figure 4 This is a schematic diagram of simulating a trainer detecting a line fault in a three-dimensional scene according to an embodiment of the present invention.

[0056] Figure 5 The embodiment of the present invention simulates a trainer making a schematic diagram of a cable intermediate head in a three-dimensional scene.

[0057] Figure 6 A flow chart of power cable operation skill training provided by the system of an embodiment of the present invention. DETAILED DESCRIPTION

[0058] Hereinafter, the specific embodiments of the present application will be described in detail with reference to the accompanying drawings. According to these detailed descriptions, those skilled in the art can clearly understand the present application and can implement the present application. Without violating the principles of the present application, the features in the various embodiments can be combined to obtain new implementations, or certain features in certain embodiments can be replaced to obtain other preferred implementations.

[0059] In order to make the features and advantages of this patent more obvious and easy to understand, the following embodiments are specifically described in detail with the accompanying drawings as follows:

[0060] This embodiment combines the three-dimensional operation application program, the digital power grid calculation and visualization program with network communication. The instructor sends operation instructions to the trainee through the digital power grid calculation and visualization program, and receives the trainee's operation results from the three-dimensional operation application program for assessment; the trainee operates in the three-dimensional operation application program and can view the corresponding changes of the digital power grid from the digital power grid calculation and visualization program. To this end, the digital power grid is first established, and then the steady-state calculation of the digital power grid is used for the identification of power cables (the simulation step is 2 seconds), and the transient calculation of the digital power grid is used for the detection of the main insulation fault of the power cable (the simulation step is 200 microseconds), and finally the installation of various accessories is completed offline only in the three-dimensional operation application program.

[0061] 1. Power cable steady-state identification training simulation

[0062] The steady-state identification of power cables is performed under the condition of static stable operation of the power system. The stability of the power system refers to the ability of the system to maintain stable operation after being disturbed under given operating conditions. The stability of the power system includes three categories: power angle stability, voltage stability and frequency stability. This embodiment starts from static voltage stability and performs analysis and identification based on power system flow calculation. The power system flow calculation belongs to the category of steady-state analysis and does not involve the dynamic characteristics and transition process of system components. The step size of the simulation calculation can be in seconds.

[0063] Since power cables are the main training objects, line types, transformer types, generator types, switch types and load types are selected to construct all digital power grids for training. The modeling is as follows:

[0064] (1) Mathematical model of the generator set

[0065] As the most important component in the power system, the mathematical model of the generator set in steady-state operation is relatively simple, usually represented by two variables.

[0066] Method 1: The emitted active power P and terminal voltage U need to be given the corresponding reactive power limit, that is, the maximum and minimum reactive power allowed to be emitted.

[0067] Method 2: Active power P and reactive power Q emitted.

[0068] (2) Transformer parameters and mathematical model

[0069] 1) Parameters and mathematical model of double-winding transformer

[0070] There are two types of transformer equivalent circuits, namely, Γ-type equivalent circuit and T-type equivalent circuit. In power system calculations, the approximate equivalent circuit of a double-winding transformer often moves the excitation branch to the power supply side, that is, the Γ-type equivalent circuit is usually used.

[0071] 2) Parameters and mathematical model of three-winding transformer

[0072] When the three-side winding capacities are different, the rated capacity of the transformer is the rated capacity of the largest capacity winding (high-voltage side). Second, the short-circuit test is performed according to the rated current of the smallest capacity winding, not the rated current of the transformer. Therefore, it is first necessary to convert the short-circuit loss to the value when the short-circuit test is performed according to the rated capacity of the transformer. Among them, the rated current of the winding is proportional to its rated capacity, while the short-circuit loss is proportional to the square of the current, and the short-circuit voltage is proportional to the current.

[0073] (3) Parameters and mathematical models of power lines

[0074] Overhead lines generally have four parameters: resistance, reactance, conductance, and susceptance. In the power system steady-state analysis, the power line model can use the total resistance, reactance, susceptance, and conductance of each phase of the entire line to identify their equivalent circuits.

[0075] (4) Load model

[0076] Load characteristics refer to the law of how load power changes with changes in load terminal voltage or system frequency, and are therefore divided into voltage characteristics and frequency characteristics.

[0077] In the steady-state analysis of the power system, the mathematical model of the load is the simplest, which is marked by given active power and reactive power. Only when high calculation accuracy is required, the static characteristics of the load need to be taken into account.

[0078] Based on the above modeling design, the 3D operation application can provide trainers with training on various identification methods of power cables. There are many methods for cable identification. At present, the commonly used methods for identifying cable lines are: power frequency induction method, audio induction method, and pulse current method. The power frequency induction method is an alternating magnetic field induced by a 50Hz AC electric field around the cable running under the power frequency state. The induction coil wound on the silicon steel sheet is directly placed on the cable. The power frequency AC signal induced by the coil can be heard in the earphone. The greater the current transmitted in the cable, the greater the power frequency AC signal heard. The audio induction method is to pass an audio current signal between the conductor and the ground or between the two-phase conductors at one end of the cable. Since the conductor of the cable is not on the axis of the cable (specifically referring to the three-core cable), the magnetic field strength at any point around the cable is inversely proportional to the distance between the point and the energized conductor, and the magnetic field strength close to the energized conductor is significantly enhanced. Therefore, the cable to be found can be identified by measuring the changes in the magnetic field around the cable. The pulse current method is to inject pulse current into the conductor of the cable (the tail wires at both ends of the cable are disconnected from the power distribution equipment beforehand), and the corresponding phase of the cable conductor at the other end is connected to the system grounding wire. Due to the very complex on-site conditions, it is difficult to identify the cable with only one method. At this time, it is necessary to combine the above methods to improve the accuracy of cable identification.

[0079] Taking the construction of a digital power grid in a certain region as an example, the instructor conducts the operation of switching the first line of the digital power grid to hot standby, such as Figure 1 As shown, the flow of the first line is diverted to the second line, and the first line is put under maintenance. The trained personnel can be required to identify the first line.

[0080] After the instructor assigned the identification of the first and second lines, the trainees performed the work in the three-dimensional work application and sent the identification results through the network to the digital power grid calculation and visualization program, such as Figure 2 shown.

[0081] 2. Power cable transient detection training simulation

[0082] When the power grid is in a stable operation state, certain faults will cause disturbances, such as power cable main insulation faults. At this time, the digital power grid calculation and visualization program performs transient simulation calculations with a step size of 200 microseconds. In reality, after calculating a certain length of disturbance, the system can generally reach an acceptable stable operation state, indicating that the fault has been handled and the system has re-entered a stable operation state. In the power cable transient detection training simulation, the transient simulation calculation can be allowed to run for any length of time to cooperate with the operation of the training personnel.

[0083] In principle, the main insulation fault detection methods of power cables can be divided into two categories: traveling wave method and impedance method. The impedance method measures and calculates the impedance from the fault point to the measuring end, and then writes and solves the fault point equation according to the line parameters to obtain the fault distance. The traveling wave ranging method uses the traveling wave characteristics of the signal propagating in the cable, records the round-trip time between the measuring point and the fault point, and obtains the fault distance through simple calculations.

[0084] The electromagnetic transient simulation of power system can essentially be attributed to the time domain response of the dynamic system, which includes the mathematical model of the system itself and the corresponding numerical algorithm. For the power system, its mathematical model consists of two parts: one is the constraint equation determined by the network topology of the system, namely the KCL and KVL equations; the other is the volt-ampere relationship equation determined by the characteristics of each component in the system. Among them, the first type of constraint equation is an algebraic equation, while the second type of equation may be an algebraic equation, a differential equation or a nonlinear equation. The electromagnetic transient modeling of the power system is to describe the characteristics of each component in the system using mathematical expressions, and finally the power grid model can be expressed in the form of node voltage equations.

[0085] Since power cables are the main training objects, we select lines, transformers, busbars, generators, circuit breakers and loads to build all digital power grids for training. The modeling of circuit breakers and lines is briefly described as follows:

[0086] (1) Circuit breaker model

[0087] 1) Circuit breaker model without considering dynamic characteristics

[0088] The circuit breaker uses the resistance insertion method to simulate the opening and closing operation. The node numbers at both ends of the circuit breaker are always kept unchanged. A small resistor is inserted when the switch is closed, and a large resistor is inserted when the switch is open. This method does not require changing the topology of the network, and is convenient for modifying the admittance matrix when switching.

[0089] Assume that the nodes on both sides of the switch are M and N, and the conductance inserted when closed is G C , when the switch is off, the inserted conductance is GO , then: i n+1 =G C u M,n+1 -G C u N,n+1 and i n+1 =G O u M,n+1 -G O u N,n+1 .

[0090] Assuming that the inflow node is in the positive direction, for the admittance matrix Y in Y·u=J:

[0091] M rows, M columns + G, M rows, N columns - G; N rows, M columns - G, N rows, N columns + G.

[0092] Usually, when the switch is closed, the inserted resistor is selected as R=10-7 ohm, and when the switch is open, the inserted resistor is selected as R=107 ohm.

[0093] The resistance switching when the circuit breaker is opened should be performed when the first opening circuit current passes through zero after receiving the trip command.

[0094] 2) Circuit breaker model considering dynamic characteristics

[0095] By simulating arc characteristics and correcting the insertion resistance, the circuit breaker breaking process can be simulated. The arc resistance simulation is a function of time and can be fitted with an exponential function.

[0096] (2) Transmission line model

[0097] 1) Concentrated parameter model

[0098] The π-type equivalent transient model of the line is the most common lumped parameter element equivalent transient model, including single π type and multi-π type, which is a method of using lumped parameter elements to approximate distributed parameter lines. The π-node equivalent circuit model is simple and suitable for short-distance lines or lines that do not consider the traveling wave process.

[0099] 2) Transmission line model considering resistance loss

[0100] For transmission lines that take losses into account, the method of lumped parameter resistance approximation is applied. Since the conductivity of overhead transmission lines to the ground is very small, ignoring it in engineering will not cause too much error. The transmission lines can be divided into several small sections, and resistances can be inserted in series between each small section for approximation.

[0101] Through experimental research, it is found that there is not much difference between dividing the line into two sections and more sections, so it can be divided into only two sections, with R / 4 connected in series at both ends and R / 2 connected in series in the middle, which is a concentrated resistance line model.

[0102] Taking the construction of a digital power grid in a certain area as an example, the instructor performed a line main insulation fault operation on one line in the digital power grid. Figure 3 The training personnel perform the operation in the 3D operation application as shown in the figure and record the distance of the fault point on the line. Figure 4 As shown, the identification results (line name and distance to the fault point) are sent to the digital power grid calculation and visualization program through the network, and the instructor can judge whether the trainee's operation is correct and the degree of correctness (i.e. the deviation from the set fault point) based on this.

[0103] 3. Cable accessories offline installation training simulation

[0104] This embodiment simulates the offline installation and production of cable accessories based on offline operating conditions. For example, according to the installation and production steps of cable accessories, the production steps of 35KV GIS cable head are shown in Table 1 below:

[0105] Table 1 Cable head production steps

[0106]

[0107]

[0108] In the 3D operation application, the corresponding 3D scene and virtual installation production process are established. The scene switching of the training process is as follows: Figure 5 As shown:

[0109] In the 3D operation application, the specific process of conducting power cable operation skill training is as follows: Figure 6 As shown, the following special functions can be provided in this embodiment:

[0110] 1. When cable identification is required in operating conditions, various settings can be made for the identified lines in the digital power grid operating in steady-state conditions, and multiple cables on the identified lines can be mixed or buried underground to increase the identification difficulty for trainees.

[0111] 2. When detecting main insulation faults in power cables, various settings can be made for the lines under test in the digital power grid operating under transient conditions, pre-embed open circuit faults, low resistance faults or high resistance faults, so that trainees can see the circuit or voltage waveform of the line and perform high-frequency partial discharge fault detection.

[0112] 3. The establishment of a digital power grid increases the effect of virtual training simulation, allowing trainees to experience the changes in the power grid caused by their own operations from the operating conditions of the digital power grid, such as watching the flow transfer and waveform changes before and after a fault occurs on the digital power grid.

[0113] 4. By establishing a digital power grid, the assessment means of power cable operation skill training has been increased. The line flow transfer status in the digital power grid can be used to verify whether the cable identified by the trainees is correct; the line fault point calculated in the digital power grid can be used to verify whether the cable main insulation fault point detected by the trainees is deviated, and the degree of deviation.

[0114] The system design provided in this embodiment can be stored in a computer-readable storage medium in a coded form and implemented in the form of a computer program. The basic parameter information required for calculation is input through computer hardware, and the calculation results are output.

[0115] Portions of its computer program may also be loaded onto other programmable data processing devices so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions executed on the computer or other programmable device for implementing the process. Figure 1 The steps of a specified function in a process or multiple processes.

[0116] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

[0117] This patent is not limited to the above-mentioned optimal implementation mode. Anyone can derive other various forms of power cable training simulation systems based on multiple time scales under the inspiration of this patent. All equal changes and modifications made according to the scope of the patent application of the present invention should be covered by this patent.

Claims

1. A multi-time scale power cable training simulation system, characterized by: Based on three-dimensional virtual simulation, multiple time scales are used to expand the operating conditions of various operations, and the operating conditions of the digital power grid are selected according to the operation requirements, including: the identification of power cables is simulated by the steady-state calculation model of the digital power grid, and the detection of main insulation faults of power cables is simulated by the transient calculation model of the digital power grid; The steady-state calculation model of the digital power grid is analyzed and identified based on the static voltage stability and power system flow calculation, and the step length of the simulation calculation is in seconds; The steady-state calculation model of the digital power grid takes power cables as the training object, selects line type, transformer type, generator type, switch type and load to construct all digital power grids for training, and its modeling is as follows: (1) Mathematical model of the generator set The mathematical model of the generator set in steady-state operation is represented by two variables: Method 1: The active power P and terminal voltage U are given, and the corresponding reactive power limit is given at the same time, that is, the maximum and minimum reactive power allowed to be emitted; Method 2: Active power P and reactive power Q emitted; (2) Transformer parameters and mathematical model 1) Parameters and mathematical model of double-winding transformer There are two equivalent circuits of transformers, namely In the calculation of power system, the approximate equivalent circuit of the double-winding transformer moves the excitation branch to the power supply side, forming Type equivalent circuit; 2) Parameters and mathematical model of three-winding transformer When the winding capacities on the three sides are different, the rated capacity of the transformer is the rated capacity of the winding with the largest capacity on the high-voltage side; the second short-circuit test is carried out according to the rated current of the winding with the smallest capacity: first, the short-circuit loss needs to be converted to the value when the short-circuit test is carried out according to the rated capacity of the transformer; the rated current of the winding is proportional to its rated capacity, the short-circuit loss is proportional to the square of the current, and the short-circuit voltage is proportional to the current; (3) Parameters and mathematical models of power lines The power line model in the steady-state analysis of the power system uses the total resistance, reactance, susceptance, and conductance of each phase of the entire line to identify their equivalent circuits; (4) Load model In the steady-state analysis of the power system, the mathematical model of the load is identified by the given active power and reactive power. The static characteristics of the load need to be taken into account only when the calculation accuracy is required to be high; Based on the transient calculation model of the digital power grid, in the training simulation of power cable transient detection, the transient simulation calculation can be allowed to run for any length of time to cooperate with the operation of the training personnel; the electromagnetic transient simulation of the power system is equivalent to the time domain response of the dynamic system, including the mathematical model of the system itself and the numerical algorithm adapted thereto, and the mathematical model includes two parts: one is the constraint equations determined by the network topology of the system, namely the KCL and KVL equations; the other is the volt-ampere relationship equations determined by the characteristics of each component in the system; the electromagnetic transient modeling of the power system is to describe the characteristics of each component in the system using mathematical expressions, and finally express the power grid model in the form of node voltage equations; The transient calculation model of the digital power grid selects line type, transformer type, bus type, generator type, circuit breaker type and load type to construct and train all digital power grids, among which the modeling of circuit breaker type and line type is as follows: (1) Circuit breaker model 1) Circuit breaker model without considering dynamic characteristics The circuit breaker uses the resistance insertion method to simulate the opening and closing operation, always keeping the node numbers at both ends of the circuit breaker unchanged, inserting a small resistor when the switch is closed, and inserting a large resistor when the switch is open; so that the admittance matrix can be modified when switching without changing the topological structure of the network; The resistance switching when the circuit breaker is opened is performed when the current of the first opening circuit passes through zero after receiving the trip command; 2) Circuit breaker model considering dynamic characteristics The insertion resistance is corrected by simulating arc characteristics to simulate the circuit breaker breaking process: the arc resistance simulates the function of time and is fitted by an exponential function; (2) Transmission line model 1) Concentrated parameter model Adopt π-node equivalent circuit model; 2) Transmission line model considering resistance loss For transmission lines that take losses into account, the concentrated parameter resistance approximation method is applied. The transmission line is divided into several small sections, and resistance is inserted in series between each small section for approximation.

2. The multi-time scale based power cable training simulation system according to claim 1, characterized in that: In the 3D operation application, training simulations of various identification methods for power cables are provided, including: power frequency induction method, audio frequency induction method, and pulse current method simulation.

3. The multi-time scale based power cable training simulation system according to claim 1, characterized in that: In the transmission line model considering resistance loss, the line is divided into two sections, R / 4 is connected in series at both ends, and R / 2 is connected in series in the middle, that is, a concentrated resistance line model.

4. The multi-time scale based power cable training simulation system according to claim 1, characterized in that: It also includes offline operating conditions for simulation of offline installation and production of cable accessories.

5. The multi-time scale based power cable training simulation system according to claim 4, characterized in that: It includes learning mode, practice mode and assessment mode.

6. The multi-time scale based power cable training simulation system according to claim 5, characterized in that: In the practice mode and assessment mode, multiple cables on the identified line are mixed or buried underground to increase the difficulty of identification for trainees; open circuit faults, low resistance faults or high resistance faults are pre-buried so that trainees can see the circuit or voltage waveform of the line and perform high-frequency partial discharge fault detection; With a virtual simulation module, the trainees can experience the grid changes caused by their own operations from the operating conditions of the digital grid; in the assessment mode, the line flow transfer conditions in the digital grid are used to check whether the cables identified by the trainees are correct; the line fault points calculated in the digital grid are used to check whether the cable main insulation fault points detected by the trainees are deviated, and the degree of deviation.

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