A method and system for monitoring leakage of power cables in substations

Abstract

A method and system for monitoring leakage of power cables in substations are proposed. A residual current difference calculation method based on space vector conversion is proposed. While ensuring the calculation accuracy, the data preprocessing step of double-end signal synchronization is saved. Then, a long-section power cable leakage fault type judgment mechanism based on double-end residual current and single-phase leakage current monitoring is established. Based on the three indicators proposed, namely, residual current difference, single-phase leakage current, and space vector circle radius change rate, the leakage state and type of the cable are accurately diagnosed. The analysis of simulation and measured data has verified the effectiveness and superiority of the algorithm. The present invention can provide useful assistance for leakage fault analysis of power cables in substations.

Description

Technical Field

[0001] The present invention belongs to the technical field of substations, and in particular relates to a substation power cable leakage monitoring method and system based on space vector composite judgment indicators. Background Art

[0002] Leakage faults are one of the main causes of fire accidents in high-voltage substations. Monitoring the leakage status of equipment in substations is the focus of substation operation and maintenance. The long-section power cables that carry the main energy demand of the load in the substation are more likely to have insulation problems than short cables in the station due to their long length (bridging the AC room and the switchyard) and relatively harsh laying environment, which makes them more likely to have leakage faults. Therefore, it is urgent to monitor the leakage status of long-section power cables, and through in-depth analysis of the monitoring data, accurately judge the cable leakage fault, and take targeted operation and maintenance measures in a timely and effective manner.

[0003] In actual field practice, residual current transformers (RCTs) are generally used to monitor the leakage status of equipment in substations, and to determine whether a leakage fault has occurred based on the monitoring data. Figure 2 As shown in the figure, the red ellipse is the location where the residual current of the cable is collected, that is, the installation location of the RCT. For the monitoring of the leakage of long-segment power cables, a double-end residual current monitoring method is required. RCTs are installed at the head end (M side) and the end end (N side) of the cable. The difference in residual current at both ends can reflect the leakage state of the power cable between the two monitoring points. The two monitoring points transmit the residual current data to the substation leakage monitoring system platform by remote communication, and the calculation and analysis of relevant leakage data are concentrated on the system platform.

[0004] At present, the research on leakage problems is mainly focused on the field of low-voltage distribution networks, and does not involve the detection and analysis of leakage faults in long sections of power cables in substations. In engineering practice, drawing on the monitoring experience of distribution network leakage faults, the monitoring of the leakage state of long sections of power cables in substations adopts the monitoring point distribution method of residual current at the head and tail ends. After synchronizing the signals at both ends, the difference between the residual currents at both ends is used to detect the leakage fault of the cable. However, the fault detection method based on residual current is only effective for unbalanced (including single-phase and two-phase) leakage faults, but it is powerless for three-phase leakage faults. Taking the single-phase leakage caused by water immersion in the cable trench as an example, in the single-phase leakage stage, the system can accurately detect the fault and alarm, and when the fault evolves into three-phase, the unbalanced current disappears, the residual current at both ends is greatly reduced, the difference between the residual currents at both ends will also be greatly reduced, and the alarm signal will disappear immediately. This situation seriously affects the judgment of the leakage fault by the substation operation and maintenance personnel, thereby delaying the opportunity to handle the fault. Summary of the invention

[0005] In order to solve the deficiencies in the prior art, the present invention provides a method and system for monitoring leakage of power cables in substations, and proposes a residual current difference calculation method based on space vector conversion, which saves the data preprocessing step of double-end signal synchronization while ensuring the calculation accuracy. Then, a long-section power cable leakage fault type judgment mechanism based on double-end residual current and single-phase leakage current monitoring is established. Based on the three indicators proposed, namely, residual current difference, single-phase leakage current, and space vector circle radius change rate, the leakage state and type of the cable are accurately diagnosed. The analysis of simulation and measured data has verified the effectiveness and superiority of the algorithm. This research result can provide useful help for leakage fault analysis of related equipment in high-voltage substations.

[0006] The present invention adopts the following technical solution.

[0007] A method for monitoring leakage of power cables in a substation, comprising the following steps:

[0008] Step 1, based on space vector transformation, calculate the residual current space vector of the long-section power cable leakage fault;

[0009] Step 2: Based on the space vector composite criterion, a comprehensive judgment is made on the leakage of the long section power cable.

[0010] Preferably, in step 1, the space vector can be expressed as the current amplitude |I m |The product of the spatial unit vector is in the form of:

[0011]

[0012] The space vector retains the size of the original three-phase system signal in terms of amplitude, and ignores the phase angle information in the A, B, and C directions of the three-phase system in terms of angle, retaining only the angular frequency that can reflect the periodic change of the signal.

[0013] In step 1, the radius of the space vector circle R M The rate of change is used as the basis for fault state evolution detection, and the calculation formula can be expressed as:

[0014] R M (t) = I mM (t)

[0015]

[0016] Where R M represents the radius of the residual current space vector circle at the beginning of the cable, t is the sampling point time, Δt is the sampling step, and the value of Δt is 0.00167s, l R Represents R M The rate of change.

[0017] Preferably, in step 2, the leakage state and type are judged based on three leakage indicators: ① the residual current difference indicator at both ends of the cable; ② the single-phase leakage current indicator (without loss of generality, the A-phase leakage current indicator is used here); ③ R M Rate of change R Indicator. The calculation criteria are as follows:

[0018] R M -R N >I T

[0019]

[0020] |l R |>l RT

[0021] Among them I T is the leakage judgment threshold value, which is 10mA, I MA is the current value of phase A M side, I e is the rated current value of the long section of power cable, I AgT1 Indicates the phase current alarm value, I AgT2 Indicates the phase current alarm value under heavy load, which is I AgT1 k times, there is I AgT2 = k*I AgT1 ; k is the current coefficient, ranging from 1.5 to 2.5; l RT For R M The change rate detection threshold is set to 0.5.

[0022] A power cable leakage monitoring system for a transformer substation comprises a space vector calculation module and a leakage comprehensive judgment module.

[0023] The space vector calculation module retains the amplitude of the original three-phase system signal, ignores the phase angle information in each direction of the three-phase system, and constructs the residual current space vector under the leakage fault as the basis for monitoring the evolution of the fault state;

[0024] The leakage comprehensive judgment module establishes the residual current differential current index, the single-phase leakage current index and the space vector circle radius change rate index, and uses the above three indicators to make a comprehensive judgment to judge the current leakage status of the cable, including the judgment of single-phase leakage fault, two-phase leakage fault and three-phase leakage fault.

[0025] The beneficial effect of the present invention is that, compared with the prior art,

[0026] The present invention adopts a substation power cable leakage monitoring algorithm based on a space vector composite criterion, performs a space vector transformation on the residual current monitoring result, and then calculates the difference of the residual current, which saves the data preprocessing step of the double-end signal synchronization in the traditional method while ensuring the calculation accuracy. Then, the residual current space vector circle radius change rate is calculated, and the space vector circle radius change rate, the residual current difference current, and the A-phase leakage current are combined to form a cable leakage fault type judgment mechanism, which can effectively realize the judgment of the three-phase cable leakage fault, and make up for the shortcomings of the existing method. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a flow chart of a method for monitoring leakage of power cables in a substation according to the present invention;

[0028] Figure 2 This is a schematic diagram of leakage monitoring of long-section power cables in substations;

[0029] Figure 3 It is a schematic diagram of the residual current space vector of single-phase and three-phase leakage fault;

[0030] Figure 4 Schematic diagram of the leakage state judgment mechanism in the present invention;

[0031] Figure 5 It is a simulation topology diagram of a long power cable of a substation in an embodiment of the present invention;

[0032] Figure 6 : is a residual current waveform diagram of the M and N sides in an embodiment of the present invention;

[0033] Figure 7 It is a spatial vector diagram of the residual current on the M side during a single-phase leakage fault in an embodiment of the present invention;

[0034] Figure 8When a single-phase leakage fault occurs R Schematic diagram of the changes;

[0035] Fig. 9 The residual current waveforms of the M and N sides after the fault evolution;

[0036] Fig.10 It is the spatial vector diagram of residual current on the M side after fault evolution;

[0037] Fig.11 After the fault evolves R Schematic diagram of the changes. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The embodiments described in this application are only embodiments of a part of the present invention, rather than all embodiments. Based on the spirit of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the protection scope of the present invention.

[0039] A method for monitoring leakage of power cables in a substation, such as Figure 1 As shown, the following steps are included.

[0040] Step 1: Based on space vector transformation, calculate the residual current space vector of the long-section power cable leakage fault.

[0041] The space vector transform is derived from the Clarke transform and is mainly used in the field of permanent magnet synchronous motor control to simplify the analysis of the rotating magnetic field:

[0042]

[0043] Where α and β are the real and imaginary parts in the vector space coordinate system, and the zero-sequence component is not considered in the present invention. Then the space vector It can be expressed as:

[0044]

[0045] According to the principle of conservation of magnetomotive force, after the three-phase coordinates are converted to the two-phase stationary coordinates, the magnetomotive force remains unchanged, and the corresponding magnetomotive force magnitude and period are the same as the three-phase stationary coordinates. Therefore, the converted space vector can be understood as a vector circle whose radius remains unchanged as the angular frequency changes. If the expression of the three-phase current is:

[0046]

[0047] Where ω is the angular frequency, the corresponding space vector can be expressed as the current amplitude |I m|The product of the spatial unit vector is in the form of:

[0048]

[0049] It can be seen that the space vector retains the size of the original three-phase system signal in terms of amplitude, and ignores the phase angle information of the A, B, and C directions in the three-phase system in terms of angle, and only retains the angular frequency that can reflect the periodic change of the signal. In the transformation of the space vector, the application object must satisfy the sinusoidal distribution in the A, B, and C three-phase stationary coordinate system. Therefore, the present invention delays the M-side and N-side residual current monitoring signals by 0°, -120°, and 120°, processes them into three-phase symmetrical signals, and converts them into space vectors. After that, the residual current difference of the signals on both sides is calculated. Corresponding to the formula, the amplitude of the residual current |I mM |、|I mN | can be obtained from the sampled data. The application of this method can effectively avoid the influence of the phase angle difference (caused by the signal transmission delay) on the calculation of the residual current difference at both ends, and effectively save the data processing steps.

[0050] The residual current space vectors on the M side of single-phase leakage fault and three-phase leakage fault can be expressed as M1 , R M3 The space vector circle of Figure 3 shown.

[0051] Figure 3 Re and Im represent the real axis and imaginary axis of the vector coordinates respectively. The space vector trajectory of the M side before and after the fault type evolution forms a set of concentric circles. The residual current amplitude R of the single-phase leakage fault M1 Larger (outer circle), three-phase leakage fault R M3 When the leakage state does not change, the radius R of the residual current space vector circle on the M side is M When the single-phase leakage fault evolves into a three-phase leakage fault, R M There will be a significant decrease, as shown by the dotted arrow in the figure. M The rate of change is used as the basis for fault state evolution detection, and the calculation formula can be expressed as:

[0052] R M (t) = I mM (t)

[0053]

[0054] Where R Mrepresents the radius of the residual current space vector circle on the M side, t is the sampling point time, Δt is the sampling step length. Since the RCT sampling frequency in the actual substation is 0.6kHz (that is, one point is sampled every 30°), the value of Δt is 0.00167s. R Represents R M The rate of change.

[0055] Step 2: Based on the space vector composite criterion, a comprehensive judgment is made on the leakage of the long section power cable.

[0056] In order to accurately detect all types of leakage faults in long sections of power cables, the present invention Figure 2 Based on the traditional long-segment power cable leakage monitoring, the A-phase leakage current monitoring is added. Single-phase current CTs are installed on the M side and the N side respectively. mMA |、|I mNA |Subtract to get |I Ag |. The leakage status and type judgment mechanism of long-segment power cables, such as Figure 4 Before judging the leakage state and type, three leakage indicators need to be calculated: ① The residual current difference between M and N; ② The single-phase leakage current indicator (without loss of generality, the A-phase leakage current indicator is used here); ③ R M Rate of change R Indicator. The calculation criteria are as follows:

[0057] R M -R N >I T

[0058]

[0059] |l R |>l RT

[0060] Among them I T is the leakage judgment threshold value, which can be taken as 10mA, I MA is the current value of phase A M side, I e is the rated current value of the long section of power cable, I AgT1 Indicates the phase current alarm value, I AgT2 Indicates the phase current alarm value under heavy load, which is I AgT1 k times, that is, I AgT2 = k*I AgT1 k is the current coefficient, and its empirical value is 1.5-2.5. It can be selected according to the actual situation of different substations. The value is 30mA. RT For R M The change rate detection threshold is set to 0.5.

[0061] like Figure 4 As shown in the figure, in actual engineering, the leakage monitoring system will calculate the leakage index once every fixed period of time. The current leakage status of the cable can be judged through the alarm indication issued by three indicators, namely the residual current differential current indicator, the A phase leakage current indicator, and the R M Rate of change R When an unbalanced (single-phase and two-phase) leakage fault occurs, the residual current difference between the M and N sides can clearly reflect the change of the unbalanced current. The corresponding residual current difference index and R M Rate of change R The indicator can also give an accurate judgment. When three-phase leakage occurs, if the event is evolved from an unbalanced fault, R M Rate of change R If the indicator is not set, the phase A leakage current indicator will respond to it.

[0062] Embodiment 1:

[0063] The simulation topology of the long section power cable of the substation is as follows: Figure 5 As shown. The low-voltage side of the transformer used is 0.4kV, the short-circuit loss of the low-voltage side load Pd=18.1kW, the short-circuit voltage percentage Ud%=6%, the parameters of the low-voltage side incoming busbar copper bar (cable) used are RL0=21.42mΩ, XL0=19.62mΩ, the load is 60kW main transformer air-cooled system (50% power (2 groups put into use), the power factor is 0.92), the power cable model is ZC-YJV22-0.6kV / 1kV four-core armored cable, and the length is set to 250m. Since insulation problems are prone to occur in the cable trench between the M-side AC room and the N-side switch field, the midpoint of the cable in this embodiment is 125m where the leakage fault occurs, and the power cable communication delay is set to 5ms (phase lag 90°). The leakage current sampling rate of the actual system is 0.6kHz. Taking the single-phase leakage fault with the highest probability as an example, the changing characteristics of leakage detection indicators in the whole fault process from single-phase leakage to three-phase leakage are discussed. The overall simulation time is 1s, a single-phase leakage fault occurs at 0.2s, and it evolves into a three-phase leakage fault at 0.4s.

[0064] When a single-phase leakage fault occurs, Figure 6 The figure shows the residual current waveforms on the M and N sides. 0.2s after the fault occurs, the residual current on the M side increases significantly, with its peak value reaching 57.4mA. The corresponding differential current on the M and N sides also increases accordingly.

[0065] The residual current on the M side is transformed into a space vector, such as Figure 7 As shown in the figure. The gray dots in the figure are the space vector points corresponding to the sampling points in the steady state, R M The smaller value is the normal state (inner circle), R MThe larger value is the single-phase leakage state (outer circle), and the circle connection line expresses the transient transition process from normal state to single-phase leakage. From the direction of the arrow, we can clearly see the process of the cable changing from normal state to single-phase leakage after the single-phase leakage occurs. At the same time, the R of the outer circle space vector point M The value is much greater than the leakage alarm threshold value I of indicator ① T With R N and (dashed circle).

[0066] The corresponding R M Rate of change R The calculation results are as follows Figure 8 As shown, during the transient transition process, l R The indicators have changed dramatically. In addition to the transition process, the stable state before and after the leakage occurs R The index is close to 0. R The detection threshold of the indicator is set to 0.5, which is determined by Figure 8 It can be seen that the l caused by the transition process R The indicator changes can clearly reflect the occurrence of single-phase leakage fault in the cable.

[0067] At the same location, the fault evolved at 0.4s, as shown in Fig. 9 The corresponding residual current waveforms on the M and N sides are shown. Consistent with the analysis in Section 2 above, the residual current on the M side suddenly decreases, which is close to the normal state 0.2s ago.

[0068] and Figure 7 similar, Fig.10 It is the spatial vector diagram of the residual current difference after the fault evolves. The outer circle is the single-phase leakage state, and the inner circle is the three-phase leakage state. The circle connection line and the arrow direction can clearly express the transient transition process from single-phase leakage to three-phase leakage.

[0069] The corresponding lR calculation results are as follows Fig.11 As shown, Figure 8 Similar, l R The index value is close to 0 before and after the fault evolution. Through the index threshold detection of 0.5, the leakage monitoring system can accurately capture the evolution of the cable leakage fault.

[0070] Furthermore, according to the leakage judgment mechanism, this embodiment collects statistics on the three indicator results of all leakage fault types, as shown in the following table.

[0071]

[0072] Note: / is close to 0, so it is not counted here.

[0073] The calculation results of the indicators in the table are all the maximum values ​​during the fault process. It can be seen from the data in the table that the leakage fault judgment mechanism proposed by the present invention can clearly indicate different leakage fault types, and the indication type results are consistent with Figure 4 The judgment mechanisms of different types are consistent.

[0074] Embodiment 2:

[0075] The effectiveness of the method proposed in the present invention is analyzed based on the leakage monitoring data of two long sections of power cables in a 500kV substation in Jiangsu Province in the second and third quarters of 2021. At the same time, the residual current differential method without timing (method one), the residual current differential method after timing (method two) and the method of the present invention (method three) are compared. Both method one and method two have been put into operation in the actual system. The corresponding data statistical results are shown in the following table.

[0076]

[0077]

[0078] According to the historical data of leakage monitoring, compared with other seasons, summer is the time when leakage accidents are most likely to occur due to its high temperature and humidity. In two quarters, there were actually 2 long-section power cable leakage incidents, one of which evolved from a single-phase leakage fault of phase A to a three-phase leakage fault. Therefore, the number of alarms that the system should issue is 3 times. When using method 1 to analyze historical data, 11 false leakage warnings occurred and no leakage warnings occurred. This is due to two reasons: first, the signal delay was not corrected, and the calculation error of the residual current difference between the two ends of the cable was large; second, due to the leakage threshold value I T The error rate is lower and the leakage alarm reaction is more sensitive. Compared with method one, method two adds the signal synchronization processing step, which greatly improves the detection accuracy of unbalanced leakage faults. However, both methods do not have the ability to detect three-phase leakage faults. Finally, the method proposed in the present invention was used to accurately detect two unbalanced leakage faults without the need for signal synchronization preprocessing. At the same time, it accurately reflects the fault evolution of one of the leakage faults, and analyzes the insulation status of the faulty power cable in more detail, which can effectively improve the accident handling efficiency of substation operation and maintenance personnel.

[0079] A power cable leakage monitoring system for a transformer substation comprises a space vector calculation module and a leakage comprehensive judgment module.

[0080] The space vector calculation module retains the amplitude of the original three-phase system signal, ignores the phase angle information in each direction of the three-phase system, and constructs the residual current space vector under the leakage fault as the basis for monitoring the evolution of the fault state;

[0081] The leakage comprehensive judgment module establishes the residual current differential current index, the single-phase leakage current index and the space vector circle radius change rate index, and uses the above three indicators to make a comprehensive judgment to judge the current leakage status of the cable, including the judgment of single-phase leakage fault, two-phase leakage fault and three-phase leakage fault.

[0082] The present disclosure may be a system, a method and / or a computer program product. The computer program product may include a computer-readable storage medium carrying computer-readable program instructions for causing a processor to implement various aspects of the present disclosure.

[0083] A computer-readable storage medium may be a tangible device that can hold and store instructions used by an instruction execution device. A computer-readable storage medium may be, for example, but not limited to, an electrical storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the foregoing. More specific examples of computer-readable storage media (a non-exhaustive list) include: a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), a static random access memory (SRAM), a portable compact disk read-only memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a floppy disk, a mechanical encoding device, such as a punch card or a raised structure in a groove on which instructions are stored, and any suitable combination of the foregoing. As used herein, a computer-readable storage medium is not to be interpreted as a transient signal per se, such as a radio wave or other freely propagating electromagnetic wave, an electromagnetic wave propagating through a waveguide or other transmission medium (e.g., a light pulse through a fiber optic cable), or an electrical signal transmitted through a wire.

[0084] The computer-readable program instructions described herein can be downloaded from a computer-readable storage medium to each computing / processing device, or downloaded to an external computer or external storage device via a network, such as the Internet, a local area network, a wide area network, and / or a wireless network. The network can include copper transmission cables, optical fiber transmissions, wireless transmissions, routers, firewalls, switches, gateway computers, and / or edge servers. The network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards the computer-readable program instructions for storage in the computer-readable storage medium in each computing / processing device.

[0085] The computer program instructions for performing the operation of the present disclosure may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-related instructions, microcode, firmware instructions, state setting data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages, such as Smalltalk, C++, etc., and conventional procedural programming languages, such as "C" language or similar programming languages. Computer-readable program instructions may be executed completely on a user's computer, partially on a user's computer, as an independent software package, partially on a user's computer, partially on a remote computer, or completely on a remote computer or server. In the case of a remote computer, the remote computer may be connected to the user's computer via any type of network, including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computer (e.g., using an Internet service provider to connect via the Internet). In some embodiments, an electronic circuit, such as a programmable logic circuit, a field programmable gate array (FPGA), or a programmable logic array (PLA), may be customized by utilizing the state information of the computer-readable program instructions, and the electronic circuit may execute the computer-readable program instructions, thereby realizing various aspects of the present disclosure.

[0086] 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, and any modifications or equivalent replacements that do 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.

Claims

1. A method for monitoring leakage of power cables in a substation, characterized in that: The following steps are involved: Step 1, based on space vector transformation, calculate the residual current space vector of the long-section power cable leakage fault; Step 2: Based on the space vector composite criterion, a comprehensive judgment is made on the leakage of long-segment power cables. The leakage status and type judgment depends on three leakage indicators: ① The residual current difference between the two ends of the cable; ② The single-phase leakage current indicator; ③ R M Rate of change Indicator; the composite criterion is: Among them, R M Represents the radius of the residual current space vector circle on the M side of the power cable, R N Indicates the radius of the residual current space vector circle on the N side of the power cable, I T is the leakage judgment threshold value, |I Ag | is the absolute value of the current difference on both sides of the power cable, I MA is the current value of phase A M side, I e is the rated current value of the power cable, I AgT1 Indicates the phase current alarm value, I AgT2 Indicates the phase current alarm value under heavy load. It represents the absolute value of the radius change rate of the residual current space vector circle on the M side of the power cable. For R M Rate of change detection threshold.

2. A method for monitoring leakage of power cables in substations according to claim 1, characterized in that: In step 1, the space vector can be expressed as the current amplitude |I m |The product of the spatial unit vector is in the form of: The space vector retains the size of the original three-phase system signal in terms of amplitude, and ignores the phase angle information in the A, B, and C directions of the three-phase system in terms of angle, retaining only the angular frequency that can reflect the periodic change of the signal.

3. A method for monitoring leakage of power cables in substations according to claim 1, characterized in that: The radius of the space vector circle R M The rate of change is used as the basis for fault state evolution detection, and the calculation formula can be expressed as: Where R M represents the radius of the residual current space vector circle at the beginning of the cable, t is the sampling point time, ∆t is the sampling step, and the value of ∆t is 0.00167s. Represents R M The rate of change.

4. A method for monitoring leakage of power cables in substations according to claim 1, characterized in that: In step 2, Leakage judgment threshold I T Take 10mA, I AgT2 =k* I AgT1 , k is the current coefficient, ranging from 1.5 to 2.5; the change rate detection threshold The value is 0.

5.

5. A substation power cable leakage monitoring system, running a substation power cable leakage monitoring method according to any one of claims 1 to 4, comprising a space vector calculation module and a leakage comprehensive judgment module, characterized in that: The space vector calculation module retains the amplitude of the original three-phase system signal, ignores the phase angle information in each direction of the three-phase system, and constructs the residual current space vector under the leakage fault as the basis for monitoring the evolution of the fault state; The leakage comprehensive judgment module establishes the residual current differential current index, the single-phase leakage current index and the space vector circle radius change rate index, and uses the above three indicators to make a comprehensive judgment to judge the current leakage status of the cable, including the judgment of single-phase leakage fault, two-phase leakage fault and three-phase leakage fault.

6. A terminal comprising a processor and a storage medium; characterized in that: The storage medium is used to store instructions; The processor is configured to operate according to the instructions to execute the steps of the method according to any one of claims 1 to 4.

7. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the steps of the method according to any one of claims 1 to 4 are implemented.

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