Method for analyzing short-circuit characteristics of open triangular loop of capacitor voltage transformer

Abstract

The invention discloses a short-circuit characteristic analysis method for an open triangular secondary circuit of a voltage transformer, and the method comprises the steps: constructing an open triangular voltage secondary circuit short-circuit topology according to the position and type of a short-circuit fault of a field capacitive voltage transformer; a short-circuit-phase circuit part which comprises a high-voltage capacitor and a medium-voltage capacitor at a time is equivalent to a power supply and internal impedance one-port form; based on the secondary circuit short-circuit topology, establishing an open triangular short-circuit equivalent model; under the condition that the discharge gap between the low-voltage end of the primary winding and the ground is broken down or not broken down, the expression of the fault circulating current flowing through the loop is analyzed under the condition that the compensation reactance factor is not considered; and establishing an equivalent transmission circuit model of the capacitor voltage transformer, analyzing a short-circuit phase voltage expression, and analyzing the change characteristics of the secondary voltage of the short-circuit phase of the voltage transformer under the condition of considering the change of the grounding resistance or the interphase resistance. The problems that a systematic voltage transformer opening triangle short circuit fault feature analysis method is lacked and fault features are not clear are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of relay protection secondary circuits, and in particular to a method for analyzing short-circuit characteristics of an open delta circuit of a capacitor voltage transformer. Background Art

[0002] Capacitor voltage transformers (CVTs), as crucial measuring equipment in substations, convert primary voltage into secondary voltage, providing essential data for secondary equipment. A CVT has three secondary windings: two star windings and one open-delta winding. An open-delta secondary circuit is a three-phase voltage transformer whose secondary windings are connected end to end, but with one point left unconnected at the end, forming an open-delta. During operation, the CVT's open-delta winding may short-circuit due to wiring errors, circuit insulation degradation, or other factors. Typical short-circuit faults in open-delta windings fall into two categories: a short between the L and N leads of an open-delta winding, and a short-circuit in one or two phases. An open-delta short-circuit can cause a voltage increase on one phase, triggering the line's overvoltage protection and tripping the opposite side, resulting in a triple tripping of the circuit breakers on both sides. Promptly eliminating the potential for open-delta short-circuit failures can prevent faultless line tripping and enhance system safety and stability. However, existing technologies lack corresponding fault characteristic analysis methods, and the characteristics of open-delta short-circuit faults are unclear, making it difficult to provide theoretical support for on-site analysis and ensuring the timely elimination of hidden dangers. Therefore, it is necessary to propose a systematic open-delta short-circuit fault characteristic analysis method to provide a basis for such hidden danger analysis and ensure the timely elimination of related hidden dangers. Summary of the Invention

[0003] In order to solve the deficiencies in the prior art, the present invention provides a method for analyzing the short-circuit characteristics of an open-delta circuit of a capacitor voltage transformer, which solves the problems of lack of a systematic method for analyzing the fault characteristics of an open-delta circuit of a capacitor voltage transformer and unclear fault characteristics.

[0004] The present invention adopts the following technical solutions.

[0005] In one aspect, the present invention provides a method for analyzing characteristics of an open-delta short circuit of a capacitor voltage transformer, comprising:

[0006] Step 1: construct a short-circuit topology of the capacitor voltage transformer open delta voltage secondary circuit according to the short-circuit fault location and fault type;

[0007] Step 2: Equivalent the circuit portion of the short-circuited phase of the short-circuit topology, which includes the high-voltage capacitor and the medium-voltage capacitor, to a one-port form of a power supply plus an internal impedance;

[0008] Step 3: Based on the secondary circuit short-circuit topology, convert the various parameters of the capacitor voltage transformer to the secondary side and establish an open delta short-circuit equivalent model;

[0009] Step 4: Based on the established open delta short-circuit model, consider the breakdown of the discharge gap P between the low-voltage end of the primary winding and the ground, and do not take into account the compensating reactance factor. Analyze the expression of the fault circulating current flowing through the circuit and compare the phase relationship between the fault circulating current and the secondary voltage of each phase.

[0010] Step 5: Based on the established open delta short-circuit model, consider the case where the discharge gap P between the low-voltage end of the primary winding and the ground is not broken down, take into account the compensating reactance factor, analyze the fault circulating current flowing in the circuit, and compare the phase relationship between the fault circulating current and the secondary voltage of each phase;

[0011] Step 6: Establish an equivalent transmission circuit model of the capacitive voltage transformer, analyze the short-circuited phase voltage expression, and analyze the change characteristics of the short-circuited phase secondary voltage of the voltage transformer while considering the change of the grounding resistance or phase-to-phase resistance.

[0012] More preferably,

[0013] In step 1, the fault location is the short circuit point in the open delta circuit. The fault type is determined based on the fault phase contained in the short circuit point and the secondary circuit grounding point; including short circuit between lead wires, short circuit of one phase winding and short circuit of two phase windings.

[0014] More preferably,

[0015] In step 2, the open voltage of the equivalent network of the short-circuited phase-one port is the short-circuited phase power supply. And the internal impedance, that is, the capacitance C corresponding to the equivalent impedance eq They are:

[0016]

[0017] C eq =C1+C2

[0018] Where C1 and C2 are the capacitance values of the high-voltage capacitor and medium-voltage capacitor of the capacitive voltage transformer after being converted to the secondary side. It is the voltage from the primary side to the secondary side during normal operation of the short-circuited phase. They are phases, namely A, B, and C phases.

[0019] More preferably,

[0020] In step 3, after converting the various parameters of the capacitor voltage transformer to the secondary side, an open triangle short-circuit equivalent model is established; the open triangle short-circuit equivalent model consists of all short-circuited phase power supplies And its internal impedance, n calculated primary winding leakage reactance X0, n open delta winding leakage reactance X4, n compensation reactance X Land grounding resistance or phase-to-phase resistance R in series; R is the secondary cable load through which the short-circuit current flows; n is the number of short-circuited phases, when short-circuiting a single phase, n=1; when short-circuiting two phases, n=2; when short-circuiting three phases, n=3.

[0021] More preferably,

[0022] In step 4, consider the breakdown of the discharge gap P between the low-voltage end of the primary winding and the ground, and do not take into account the compensation reactance X L Under the factors, the fault circulation I k The calculation formula is:

[0023]

[0024] Where, X C1 is the capacitive reactance of the high voltage capacitor, X C2 is the capacitive reactance of the medium voltage capacitor, X0 is the leakage reactance of the primary winding, X4 is the leakage reactance of the open delta winding, R is the grounding resistance or phase resistance, Short-circuit all phase power supplies series connection, n is the number of short-circuited phases, when short-circuiting a single phase, n = 1; when short-circuiting two phases, n = 2; when short-circuiting three phases, n = 3, " / / " indicates the parallel connection of two capacitive reactances; let Z2 = n*[-j(X C1 / / X C2 )+jX0+jX4]+R, according to the configuration of the capacitor voltage transformer parameters, Z2 is capacitive resistance, I k Should be ahead An acute angle.

[0025] More preferably,

[0026] In step 5, consider the case where the discharge gap P is not broken down and take into account the compensating reactance X L Under the factors, the fault circulation I k The calculation formula is:

[0027]

[0028] Where, X L To compensate the reactance, let Z3=n*[-j(X C1 / / X C2 )+jX0+jX4+jX L ]+R, according to the configuration of the capacitor voltage transformer parameters, Z3 is inductive resistance, I k Should lag-U Aoc An acute angle.

[0029] More preferably,

[0030] In step 6, short the phase secondary voltage The expression is:

[0031]

[0032] Where Z1=-j(X C1 / / X C2 )+jX0+jX L .

[0033] More preferably,

[0034] Consider the breakdown of the discharge gap P between the low-voltage end of the primary winding and the ground, without taking into account the compensation reactance X L Under these factors, when R changes from 0 to ∞, the phase difference between Z1 and Z2 changes from 0° to -90°; considering the case where the discharge gap P between the low-voltage end of the primary winding and the ground is not broken down, the compensating reactance X is included. L Under the factor, when R changes from 0 to ∞, the phase difference between Z1 and Z3 changes from -180° to -90°.

[0035] More preferably,

[0036] When R=0, the breakdown of the discharge gap P between the low-voltage end of the primary winding and the ground is considered, and the compensation reactance X is not included. L Factors, I k *Z1 voltage phasor is When R=∞, I k *Z1 voltage phasor is 0; when R=0, consider the case where the discharge gap P between the low-voltage end of the primary winding and the ground is not broken down, and include the compensating reactance X L Factors, I k *Z1 voltage phasor is When R=∞, I k *Z1 voltage phasor is 0.

[0037] More preferably,

[0038] I k *The direction of the Z1 endpoint trajectory is from the point corresponding to R = 0 to the point corresponding to R = ∞ along the phase change direction. The trajectory is a semicircle, and the line connecting the two points corresponding to R = 0 and R = ∞ is the diameter of the semicircle;

[0039] When the discharge gap P between the low voltage end of the primary winding and the ground is broken down or not broken down, I k * On the Z1 voltage phasor diagram, the open voltage of the short-circuited phase port with -I k *Z1 voltage phasors are superimposed to obtain the short-circuited phase voltage fault characteristics of the open delta secondary circuit of the capacitor voltage transformer.

[0040] Another aspect of the present invention discloses an electronic device, including a processor, characterized in that:

[0041] The processor is used to operate according to the instructions to execute the steps of the above-mentioned open triangle short circuit characteristic analysis method.

[0042] The present invention also discloses a computer-readable storage medium on which a computer program is stored, characterized in that the program is processed to execute the steps of the aforementioned open triangle short circuit characteristic analysis method.

[0043] The beneficial effect of the present invention lies in that, based on the characteristics of the existing open two-angle secondary winding, the present invention establishes a short-circuit model of the open triangle of the capacitive voltage transformer, analyzes the fault circulation current of the open short-circuit loop, draws the voltage phasor diagram under the change of grounding resistance or phase resistance, and systematically provides a fault characteristic analysis method for the short circuit of the open triangle secondary loop of the voltage transformer. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 Schematic diagram of the flow of the short-circuit characteristic analysis method of the open delta circuit of the capacitor voltage transformer;

[0045] Figure 2 This is a schematic diagram of the principle of a capacitive voltage transformer;

[0046] Figure 3 It is a schematic diagram of the short circuit of the open delta voltage secondary circuit of the capacitor voltage transformer;

[0047] Figure 4 It is the open delta short-circuit equivalent circuit diagram of capacitor voltage transformer;

[0048] Figure 5 The discharge gap P between the low-voltage end of the primary winding and the ground when the capacitor voltage transformer is open-delta short-circuited is broken down and I is not broken down. k *Z1 voltage phasor diagram;

[0049] Figure 6 The discharge gap P between the low-voltage end of the primary winding and the ground when the B and C phases of the open delta are short-circuited is broken down and I is not broken down. k *Z1 voltage phasor diagram. DETAILED DESCRIPTION

[0050] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. The embodiments described in this application are only part of the embodiments of the present invention, not all of them. Based on the spirit of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0051] The present invention proposes a method for analyzing the short-circuit characteristics of an open delta circuit of a capacitor voltage transformer. Figure 1 As shown, the following steps are included:

[0052] Step 1, such as Figure 2 and Figure 3 As shown, according to the short-circuit situation of the open-delta secondary circuit of the capacitor voltage transformer on site, a short-circuit topology of the open-delta voltage secondary circuit of the capacitor voltage transformer is constructed.

[0053] Depending on the fault phases included in the short-circuit point and the secondary circuit grounding point N600, the fault types include lead-out short circuit, one-phase winding short circuit, and two-phase winding short circuit. When the short-circuit point and N600 only include one phase, the transition resistance formed by the shorted phase winding and the cables in the loop forms a loop-like secondary circuit short circuit equivalent topology. When the short-circuit point and N600 only include two phases, the transition resistance formed by the two shorted phase windings and the cables in the loop forms a loop-like secondary circuit short circuit equivalent topology. When the lead-out short circuit occurs, the transition resistance formed by the three-phase windings and the cables in the loop forms a loop-like secondary circuit short circuit equivalent topology. Figure 3 It is a two-phase short-circuit situation;

[0054] Step 2: According to the Thevenin equivalence theorem, the circuit part of the short-circuit topology, which includes the high-voltage capacitor and the medium-voltage capacitor, is equivalent to a one-port form of power supply plus internal impedance, where the internal impedance is capacitive reactance. The opening voltage of the Thevenin equivalent port is And the capacitance C corresponding to the equivalent impedance eq They are:

[0055]

[0056] C eq =C1+C2(2)

[0057] Where C1 and C2 are the capacitance values of the high-voltage capacitor and medium-voltage capacitor of the capacitor voltage transformer after being converted to the secondary side. It is the voltage from the primary side to the secondary side during normal operation of the short-circuited phase. Phases are A, B, and C. eq It is the equivalent capacitance of high voltage capacitor and medium voltage capacitor in parallel.

[0058] Step 3: Based on the secondary circuit short-circuit topology, convert the various parameters of the capacitor voltage transformer to the secondary side and establish an open delta short-circuit equivalent model;

[0059] The conversion formula is:

[0060] U2=U1 / k(3)

[0061] Z2=Z1 / k2 (4)

[0062] Where k is the transformation ratio of the primary and secondary sides of the capacitor voltage transformer, U2 is the voltage after the primary side voltage U1 is converted to the secondary side, and Z2 is the impedance after the primary side impedance Z1 is converted to the secondary side. After converting the various parameters of the capacitor voltage transformer to the secondary side, the open triangle short-circuit equivalent model is established as follows: Figure 4 As shown, the open delta short circuit equivalent model consists of all short-circuited phase power supplies And its internal impedance, n calculated primary winding leakage reactance X0, n open delta winding leakage reactance X4, n compensation reactance X L and grounding resistance or phase-to-phase resistance R in series. R is primarily the secondary cable load through which the short-circuit current flows. The diagram shows a method that makes it easier to analyze short-circuit characteristics. n is the number of shorted phases. When shorting a single phase, n = 1; when shorting two phases, n = 2; when shorting three phases, n = 3.

[0063] Step 4: Based on the established open delta short-circuit model of the capacitor voltage transformer, the breakdown of the discharge gap P between the low-voltage end of the primary winding and the ground is considered, and the compensation reactance X is not taken into account. L Under the factors, the expression of the fault circulation flowing in the analytical circuit is: k The calculation formula is:

[0064]

[0065] Where, X C1 is the capacitive reactance of the high voltage capacitor, X C2 is the capacitive reactance of the medium voltage capacitor. For all short-circuited phases n is the number of shorted phases. When shorting a single phase, n = 1; when shorting two phases, n = 2; when shorting three phases, n = 3. “ / / ” indicates the parallel connection of two capacitive reactances. Let Z2 = n*[-j(X C1 / / X C2 )+jX0+jX4]+R, can be determined according to the configuration parameters of the capacitive voltage transformer, Z2 is capacitive resistance, I k Should be ahead An acute angle.

[0066] Step 5: Based on the established open delta short-circuit model of the capacitor voltage transformer, taking into account the case where the discharge gap P between the low-voltage end of the primary winding and the ground is not broken down, the compensating reactance X is taken into account. L Under the factors, the fault loop current flowing in the analytical circuit, the fault loop current I k The calculation formula is:

[0067]

[0068] Where, X L is the compensating reactance. Let Z3=n*[-j(X C1 / / X C2 )+jX0+jX4+jX L ]+R, can be determined according to the configuration parameters of the capacitor voltage transformer, Z3 is inductive resistance, I k Should lag An acute angle.

[0069] Step 6: Establish the equivalent transmission circuit model of the capacitive voltage transformer, analyze the short-circuited phase voltage expression, and the short-circuited phase secondary voltage The expression is:

[0070]

[0071] The expression of equivalent impedance Z1 is:

[0072] Z1=-j(X C1 / / X C2 )+jX0+jX L (8)

[0073] The equivalent impedance Z1 is capacitive when considering the breakdown or non-breakdown of the discharge gap P between the low-voltage end of the primary winding and the ground. k *Z1 voltage phasor diagram. The drawing method is to determine I when R=0 and R=∞ k * Z1 voltage phasor endpoints, and determine the change of I k * The direction of change of the phase of the Z1 phasor, I k *The direction of the Z1 endpoint trajectory is from the point corresponding to R = 0 to the point corresponding to R = ∞ along the phase change direction. The trajectory is a semicircle, and the line connecting the two points corresponding to R = 0 and R = ∞ is the diameter of the semicircle. Figure 5 For step 6, plot R from 0 to infinitely varying I k *Specific description of Z1 voltage phasor diagram.

[0074] In view of the characteristics of the existing open-delta secondary winding, the present invention establishes a short-circuit model of the open-delta capacitor voltage transformer, analyzes the fault circulation current of the open short-circuit loop, and draws the voltage phasor diagram under the change of grounding resistance or phase-to-phase resistance. It systematically provides a fault characteristic analysis method for the short circuit of the open-delta secondary circuit of the voltage transformer, provides a basis for such hidden danger analysis, ensures the timely elimination of related hidden dangers, and guarantees the safe and stable operation of the secondary circuit of the voltage transformer.

[0075] The present invention also protects an electronic device, comprising a processor; the processor is configured to operate according to the instructions to execute the steps of the aforementioned open delta short circuit characteristic analysis method.

[0076] The present invention also discloses a computer-readable storage medium on which a computer program is stored. The program is processed to execute the steps of the above-mentioned open triangle short circuit characteristic analysis method.

[0077] Example 1

[0078] Take the B and C phase open triangle short circuit as an example,

[0079] The circuit part of phase B and phase C, including the high-voltage capacitor and the medium-voltage capacitor, is equivalent to a single-port form of power supply plus internal impedance, where the internal impedance is capacitive reactance. The opening voltage of phase B at the Thevenin equivalent port is U Boc =(C1 / C1+C2)U B ,U Coc =(C1 / C1+C2)U C And the capacitance corresponding to the equivalent impedance is C eq =C1+C2.

[0080] After converting the various parameters of the capacitor voltage transformer to the secondary side, the short-circuit resistance between phases B and C is R, which is mainly the secondary cable load through which the short-circuit current flows. The capacitor voltage transformer circuit between phases B and C can be equivalent to U B with U C Two constant voltage sources, two calculated primary winding leakage reactances X0, two open delta winding leakage reactances X4, two compensation reactances X L And the series circuit of phase-to-phase resistance R.

[0081] When considering the breakdown of the discharge gap P between the low-voltage end of the primary winding and the earth, the compensation reactance X is not included. L Under the factors, the fault circulation I k for (U Boc +U Coc ) / {2*[-j(X C1 / / X C2 )+jX0+jX4]+R}. Let Z2=2*[-j(X C1 / / X C2 )+jX0+jX4]+R, according to the configuration of the capacitor voltage transformer parameters, Z2 is capacitive resistance, I k Should be ahead-U Aoc An acute angle.

[0082] According to step 5, considering that the discharge gap P between the low-voltage end of the primary winding and the ground is not broken down, the compensation reactance X is included. L Under the factors, the fault circulation I k for (U Boc +U Coc ) / {2*[-j(X C1 / / X C2)+jX0+jX4+jX L ]+R}. Let Z3=2*[-j(X C1 / / X C2 )+jX0+jX4+jX L ]+R, according to the configuration of the capacitor voltage transformer parameters, Z3 is inductive resistance, I k Should lag-U Aoc An acute angle.

[0083] The secondary voltage of phase B is: U dB =U Boc -I k *Z1; C phase secondary voltage is: U dC =U Coc -I k *Z1; the equivalent impedance Z1 is Z1=-j(X C1 / / X C2 )+jX0+jX L .

[0084] Draw the voltage phasor diagram when R changes infinitely from 0 phase and the gap P between the low voltage end of the primary winding and the ground is broken down and not broken down. Figure 6 As shown. In both cases I k *The point on the semicircular trajectory of the Z1 voltage phasor and the B phase voltage phasor U Boc And C phase voltage phasor U Coc The phasor variation characteristics of the secondary voltages of phases B and C are shown in Figure 1. This indicates that the fault characteristics of a two-phase short-circuit fault in an open delta circuit are: when the secondary circuit impedance is resistive-capacitive, the leading phase voltage increases, while the lagging phase voltage may increase or decrease with parameter changes; when the secondary circuit impedance is resistive-inductive, the leading phase voltage increases, while the lagging phase voltage may increase or decrease with parameter changes. This should be determined based on the specific circumstances.

[0085] The present disclosure may be a system, method and / or 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.

[0086] A computer-readable storage medium can be a tangible device that can hold and store instructions for use by an instruction execution device. A computer-readable storage medium can 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 thereof. More specific examples (a non-exhaustive list) of computer-readable storage media 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 disc 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 thereof. As used herein, a computer-readable storage medium is not to be construed 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 an electrical wire.

[0087] 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, fiber optic transmission, wireless transmission, 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 to be stored in the computer-readable storage medium in each computing / processing device.

[0088] The computer program instructions for performing the operations of the present disclosure may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent 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++, and conventional procedural programming languages such as "C" language or similar programming languages. Computer-readable program instructions may be executed entirely 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 entirely 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., utilizing 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 personalized by utilizing the state information of the computer-readable program instructions. The electronic circuit may execute the computer-readable program instructions, thereby realizing various aspects of the present disclosure.

[0089] 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 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 by the scope of protection of the claims of the present invention.

Claims

1. A method for analyzing short-circuit characteristics of an open delta circuit of a voltage transformer, characterized in that: include: Step 1: construct a short-circuit topology of the capacitor voltage transformer open delta voltage secondary circuit according to the short-circuit fault location and fault type; Step 2: Equivalent the circuit portion of the short-circuited phase of the short-circuit topology, which includes the high-voltage capacitor and the medium-voltage capacitor, to a one-port form of a power supply plus an internal impedance; Step 3: Based on the equivalent secondary circuit short-circuit topology, convert the various parameters of the capacitor voltage transformer to the secondary side and establish an open delta short-circuit equivalent model; Step 4: Based on the established open delta short-circuit model, consider the breakdown of the discharge gap P between the low-voltage end of the primary winding and the ground, and do not take into account the compensating reactance factor. Analyze the expression of the fault circulating current flowing through the circuit and compare the phase relationship between the fault circulating current and the secondary voltage of each phase. Step 5: Based on the established open delta short-circuit model, consider the case where the discharge gap P between the low-voltage end of the primary winding and the ground is not broken down, take into account the compensating reactance factor, analyze the fault circulating current flowing in the circuit, and compare the phase relationship between the fault circulating current and the secondary voltage of each phase; Step 6: Establish an equivalent transmission circuit model of a capacitive voltage transformer, analyze the short-circuited phase voltage expression based on the fault circulation current, and analyze the change characteristics of the short-circuited phase secondary voltage of the voltage transformer while considering the change of the grounding resistance or the phase-to-phase resistance.

2. The method for analyzing short-circuit characteristics of an open delta circuit of a voltage transformer according to claim 1, characterized in that: In step 1, the fault location is the short circuit point in the open delta circuit. The fault type is determined based on the fault phase contained in the short circuit point and the secondary circuit grounding point; including short circuit between lead wires, short circuit of one phase winding and short circuit of two phase windings.

3. The method for analyzing short-circuit characteristics of an open delta circuit of a voltage transformer according to claim 1, wherein: In step 2, the open voltage of the equivalent network of the short-circuited phase-one port is the short-circuited phase power supply. And the internal impedance, that is, the capacitance C corresponding to the equivalent impedance eq They are: C eq =C1+C2 Where C1 and C2 are the capacitance values of the high-voltage capacitor and medium-voltage capacitor of the capacitive voltage transformer after being converted to the secondary side. It is the voltage from the primary side to the secondary side during normal operation of the short-circuited phase. They are phases, namely A, B, and C phases.

4. The method for analyzing short-circuit characteristics of an open delta circuit of a voltage transformer according to claim 1, wherein: In step 3, after converting the various parameters of the capacitor voltage transformer to the secondary side, an open triangle short-circuit equivalent model is established; the open triangle short-circuit equivalent model consists of all short-circuited phase power supplies And its internal impedance, n calculated primary winding leakage reactance X0, n open delta winding leakage reactance X4, n compensation reactance X L and grounding resistance or phase-to-phase resistance R in series; R is the secondary cable load through which the short-circuit current flows; n is the number of short-circuited phases, when short-circuiting a single phase, n=1; when short-circuiting two phases, n=2; when short-circuiting three phases, n=3.

5. The method for analyzing short-circuit characteristics of an open delta circuit of a voltage transformer according to claim 1, wherein: In step 4, consider the breakdown of the discharge gap P between the low-voltage end of the primary winding and the ground, and do not take into account the compensation reactance X L Under the factors, the fault circulation I k The calculation formula is: Where, X C1 is the capacitive reactance of the high voltage capacitor, X C2 is the capacitive reactance of the medium voltage capacitor, X0 is the leakage reactance of the primary winding, X4 is the leakage reactance of the open delta winding, R is the grounding resistance or phase resistance, Short-circuit all phase power supplies series connection, n is the number of short-circuited phases, when short-circuiting a single phase, n = 1; when short-circuiting two phases, n = 2; when short-circuiting three phases, n = 3, " / / " indicates the parallel connection of two capacitive reactances; let Z2 = n*[-j(X C1 / / X C2 )+jX0+jX4]+R, according to the configuration of the capacitor voltage transformer parameters, Z2 is capacitive resistance, I k Should be ahead An acute angle.

6. The method for analyzing short-circuit characteristics of an open delta circuit of a voltage transformer according to claim 5, characterized in that: In step 5, consider the case where the discharge gap P is not broken down and take into account the compensating reactance X L Under the factors, the fault circulation I k The calculation formula is: Where, X L To compensate the reactance, let Z3=n*[-j(X C1 / / X C2 )+jX0+jX4+jX L ]+R, according to the configuration of the capacitor voltage transformer parameters, Z3 is inductive resistance, I k Should lag An acute angle.

7. The method for analyzing short-circuit characteristics of an open delta circuit of a voltage transformer according to claim 6, characterized in that: In step 6, short the phase secondary voltage The expression is: Where Z1=-j(X C1 / / X C2 )+jX0+jX L .

8. The method for analyzing short-circuit characteristics of an open delta circuit of a voltage transformer according to claim 7, characterized in that: Consider the breakdown of the discharge gap P between the low-voltage end of the primary winding and the ground, without taking into account the compensation reactance X L Under these factors, when R changes from 0 to ∞, the phase difference between Z1 and Z2 changes from 0° to -90°; considering the case where the discharge gap P between the low-voltage end of the primary winding and the ground is not broken down, the compensating reactance X is included. L Under the factor, when R changes from 0 to ∞, the phase difference between Z1 and Z3 changes from -180° to -90°.

9. The method for analyzing short-circuit characteristics of an open delta circuit of a voltage transformer according to claim 8, characterized in that: When R=0, the breakdown of the discharge gap P between the low-voltage end of the primary winding and the ground is considered, and the compensation reactance X is not included. L Factors, I k *Z1 voltage phasor is When R=∞, I k *Z1 voltage phasor is 0; when R=0, consider the case where the discharge gap P between the low-voltage end of the primary winding and the ground is not broken down, and include the compensating reactance X L Factors, I k *Z1 voltage phasor is When R=∞, I k *Z1 voltage phasor is 0.

10. The method for analyzing short-circuit characteristics of an open delta circuit of a voltage transformer according to claim 9, characterized in that: I k *The direction of the Z1 endpoint trajectory is from the point corresponding to R = 0 to the point corresponding to R = ∞ along the phase change direction. The trajectory is a semicircle, and the line connecting the two points corresponding to R = 0 and R = ∞ is the diameter of the semicircle; When the discharge gap P between the low voltage end of the primary winding and the ground is broken down or not broken down, I k * On the Z1 voltage phasor diagram, the open voltage of the short-circuited phase port with -I k *Z1 voltage phasors are superimposed to obtain the short-circuited phase voltage fault characteristics of the open delta secondary circuit of the capacitor voltage transformer.

11. An electronic device comprising a processor; characterized in that: 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 10.

12. A computer-readable storage medium having a computer program stored thereon, characterized in that: The program is processed to execute the steps of the method according to any one of claims 1 to 10.

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