A three-dimensional visualization simulation method for substation DC system multi-point grounding fault

Abstract

The application discloses a three-dimensional visualization simulation method for substation DC system multi-point grounding fault, belonging to the operation and maintenance management field of the substation DC system. The method comprises the following steps: setting a three-dimensional engine for constructing a three-dimensional model of the substation DC system, and establishing the three-dimensional model of the substation DC system; adding / setting a fault point on each cable of the three-dimensional model of the DC system; for each fault point, establishing an association relationship with a state of a superior switch set; setting a grounding resistance of each fault point in sequence; calculating a voltage of a positive bus and a negative bus according to the grounding resistance and the state of the switch set associated with the fault point; and expressing the voltage in a three-dimensional visualization mode. The three-dimensional visualization display of the substation DC system multi-point grounding fault can help improve the maintenance work under the condition of the DC system fault, provide a basis for establishing a more complete digital twin of the DC system, and also provide a new type of DC system training method.

Description

Technical Field

[0001] This invention belongs to the field of substation DC system operation and maintenance management, and particularly relates to a three-dimensional visualization simulation method for multi-point grounding faults in substation DC systems. Background Technology

[0002] Currently, the control circuits, relay protection devices and output circuits, and signal circuits of substations are all powered by DC power; the system that supplies power to the above circuits, devices and power equipment is called a DC system.

[0003] DC systems are important systems in substations. To ensure the safe and economical operation of power plants and substations, a complete and reliable DC system is essential.

[0004] When the insulation level of the positive pole (also known as the positive busbar, or simply the positive busbar) or negative pole (also known as the negative busbar, or simply the negative busbar) of a DC system to ground decreases to a certain set value, it is collectively referred to as DC grounding.

[0005] If a DC system has only one grounding point, it will not cause direct harm to the DC system. However, in this case, the relay protection device may fail to operate or operate malfunctioning, posing an operational risk. The fault must be eliminated in time.

[0006] When a DC system experiences a multi-point grounding fault, it may cause a grounding short circuit, resulting in malfunctions or failures of relay protection, signaling, and automatic devices. It may even cause the DC fuse to blow, causing the protection and automatic devices and control circuits to lose power.

[0007] Currently, there are mature technologies for DC grounding resistance detection, and there are many DC grounding simulations conducted using schematic diagrams. However, there are no reports of DC grounding simulations achieved through three-dimensional visualization.

[0008] The invention patent application CN 106896293A, published on June 27, 2017, discloses a "Single-Phase Grounding Simulation Modeling System for Distribution Networks." This method simplifies complex network branches and can perform qualitative simulation analysis on mainstream fault location methods. Considering factors affecting single-phase grounding fault location in distribution networks, including line type, fault location, grounding resistance, and initial phase angle, it can simulate the current variation characteristics of the grounding fault itself, the current variation characteristics under different injection signal methods, the current variation characteristics under different input resistors / reactors, and related electrical quantity characteristics. This allows for the determination of the general variation law of fault characteristics when the neutral point is not grounded or grounded through an arc suppression coil. Furthermore, it can be used to verify single-phase grounding fault location and location methods in distribution networks. This system is only suitable for qualitative analysis of the transient and steady-state characteristics of a single-phase grounding fault (also known as single-point grounding) in a neutral-point ungrounded system and a neutral-point grounded system via an arc-suppression coil. It cannot display the operation of the DC system under multi-point grounding conditions in the current system and cannot realize three-dimensional visualization simulation of multi-point grounding faults in the DC system of a substation.

[0009] The invention patent application CN 114509958A, published on May 17, 2022, discloses a "Single-Phase Grounding Simulation System and Method for Distribution Networks Based on a Three-Segment Arc Resistance Model." This system includes a 220kV incoming line; a 66kV system with a single busbar branching off from the 220kV incoming line, and a grounding transformer installed on the 66kV busbar; an arc-suppression coil and a small resistor installed at the neutral point of the grounding transformer for simulating different grounding methods at the neutral point; feeders of different line types for simulating single-phase grounding in distribution networks with different line combinations; a 10kV system branching off from the feeders connecting to the load end; and distributed generation power sources connected to the grid on the feeders for simulating single-phase grounding in distribution networks with different distributed generation types, grid connection locations, and power capacity. The arc model on the feeders adopts a three-segment arc resistance model. This technical solution cannot establish a three-dimensional model of the substation DC system to display the operation of the DC system under multi-point grounding conditions in a three-dimensional visualization manner. Summary of the Invention

[0010] The technical problem to be solved by this invention is to provide a three-dimensional visualization simulation method for multi-point grounding faults in a substation DC system. It establishes a three-dimensional model of the substation DC system and displays the operation of the DC system under multi-point grounding conditions in a three-dimensional visualization manner.

[0011] The technical solution of this invention is: to provide a three-dimensional visualization simulation method for multi-point grounding faults in a substation DC system, including setting up a three-dimensional engine for constructing a three-dimensional model of the substation DC system, characterized by the following steps:

[0012] 1) Establish a three-dimensional model of the substation's DC system;

[0013] 2) Add / set fault points on each cable segment of the DC system 3D model;

[0014] 3) For each fault point, establish its association with the status of the upper-level switch set;

[0015] 4) Click on multiple fault points in sequence and set the grounding resistance for each fault point in turn;

[0016] 5) Calculate the voltage to ground of the positive and negative busbars based on the grounding resistance and the status of the switch set associated with the fault point;

[0017] 6) Express voltage magnitude in a three-dimensional visualization;

[0018] The three-dimensional visualization simulation method for multi-point grounding faults in the substation DC system establishes a three-dimensional model of the substation DC system, constructs the correlation between the fault point and the status of the upstream switch set, determines the ground voltage of the positive and negative buses associated with the fault point, and displays the voltage of each branch in a three-dimensional mode using different colors according to the magnitude of the ground voltage, thereby realizing the display of the operation of the DC system under multi-point grounding in a three-dimensional visualization manner.

[0019] Specifically, the three-dimensional model of the substation DC system includes at least power supply, cables, DC circuit breakers, terminals, and DC loads; wherein, the power supply and DC loads adopt abstract models; the cables, DC circuit breakers, and terminals must use realistic models; the three-dimensional distribution of DC circuit breakers and terminals is consistent with the actual situation of the substation; the three-dimensional spatial distribution and connection relationship of cables are consistent with the actual situation; the cables are divided into a limited number of segments by DC circuit breakers, terminals, and loads.

[0020] Specifically, grounding in the DC system is detected on a branch-by-branch basis; fault points are set on a branch-by-branch basis, and a fault setting point is added to each cable segment of each branch.

[0021] Furthermore, the fault points are divided into positive busbar side fault points and negative busbar side fault points.

[0022] Specifically, in step 3), for any DC cable, it is composed of several DC circuit breakers and terminals connected in series through the cable; from the power source to the load, the DC cable is segmented by several DC circuit breakers and terminals; if both the DC circuit breaker and the terminal are regarded as switching elements, then a "sequence of elements" is formed from the power source to the load; the elements closer to the power source are ordered first; for any fault point, its preceding elements include several DC circuit breakers, and the preceding DC circuit breakers of any fault point form a "set".

[0023] Furthermore, in step 3), for the “set”, if any DC circuit breaker in it is in the open state, then the set is recorded as the open state; if every DC circuit breaker in it is in the connected state, then the set is recorded as the connected state; any fault point corresponds to a set state of DC circuit breaker, thereby establishing the association between the fault point and the set state of the upper-level DC circuit breaker.

[0024] Specifically, in step 4), when conducting the simulation, click on the fault point and input the grounding resistance; the resistance value range is 0 to 999 k ohms; select one point from all fault points and input the grounding resistance, which represents the resistance of that point or the branch cable to ground.

[0025] Furthermore, in step 5), for each fault point, if any of the switches in the associated set are in an open state, the grounding resistance of the fault point is not included in the calculation and the fault point is ignored; if any of the switches in the associated set are in an on state, the grounding resistance of the fault point is included in the calculation.

[0026] Furthermore, in step 5), let the grounding resistance of multiple fault points on the positive busbar side be R. x1 R x2 …R xn The grounding resistance of multiple fault points on the negative busbar side is R. y1 R y2 …R yn When the system is running normally, the voltage of the positive busbar to ground is U. + The voltage of the negative busbar to ground is U. - In a DC system, the balancing bridge resistors are R1 and R2, with R1 closer to the positive busbar and R2 closer to the negative busbar. The unbalanced bridge resistors are R3 and R4, with R3 closer to the positive busbar and R4 closer to the negative busbar. After grounding, the voltage between the positive busbar and ground is U1, and the voltage between the negative busbar and ground is U2. Therefore:

[0027] 1) Calculate R x1 R x2 …R xn The total parallel resistance R X ;

[0028] 2) Calculate R y1 R y2 …R yn The total parallel resistance R Y ;

[0029] 3) Let the ratio of the positive and negative busbar voltages to ground be K:

[0030]

[0031] but

[0032]

[0033] in

[0034]

[0035]

[0036]

[0037] U2=U1-(U + -U - ).

[0038] Specifically, in step 6), after the voltage calculation is completed, if the voltage of a certain branch is greater than zero, the branch is highlighted in green in the 3D engine, and the color depth varies with the magnitude of the positive bus voltage to ground U1.

[0039] If the voltage of a branch is less than zero, the branch will be highlighted in red, and the color depth will vary with the magnitude of the negative bus voltage to ground U2.

[0040] If the voltage of a branch is zero, it will be displayed in gray.

[0041] Compared with the prior art, the advantages of the present invention are:

[0042] 1. The implementation of the technical solution of the present invention, since its grounding point can be set as needed, can clearly and intuitively observe the operation of the existing substation DC system under the condition of single-point or multi-point DC grounding faults in the substation DC system based on the grounding resistance and the status of the switch set associated with the fault point;

[0043] 2. The technical solution of the present invention calculates the voltage to ground of the positive and negative busbars by setting multiple grounding points and corresponding grounding resistances; it can display the operation of the DC system under multiple grounding point conditions and express the voltage magnitude in a three-dimensional visualization manner;

[0044] 3. The implementation of the technical solution of the present invention can help improve the maintenance work when a DC system fails, and provide a foundation for establishing a more complete digital twin of the DC system. It can also provide a new training method for DC systems. Attached Figure Description

[0045] Figure 1 This is a block diagram illustrating the method flow of the present invention. Detailed Implementation

[0046] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0047] Figure 1 The implementation of this technical solution mainly includes the following steps:

[0048] 1) Establish a three-dimensional model of the DC system of the substation. The three-dimensional model of the DC system of the substation mainly includes power supply, cables, DC circuit breakers, terminals and DC loads.

[0049] 2) Add fault setting points (hereinafter referred to as fault points) on each cable segment of the DC system three-dimensional model. The fault points are divided into positive bus side fault points and negative bus side fault points.

[0050] 3) For each fault point, establish its association with the status of the upper-level switch set;

[0051] 4) Click on multiple fault points in sequence and set the grounding resistance for each fault point in turn;

[0052] 5) Calculate the voltage to ground of the positive and negative busbars based on the grounding resistance and the status of the switch set associated with the fault point;

[0053] 6) Express voltage magnitude in a three-dimensional visualization;

[0054] By establishing a three-dimensional model of the DC system of the substation, the operation of the DC system under multi-point grounding conditions can be displayed in a three-dimensional visualization manner.

[0055] Specifically, the technical solution of this invention is described in detail below:

[0056] For step 1), a three-dimensional model of the DC system of the substation is established. The three-dimensional model of the DC system includes at least the power supply, cables, DC circuit breakers, terminals, and DC loads.

[0057] The power supply and DC load can be abstract models, while cables, DC circuit breakers and terminals must be real-world models.

[0058] The three-dimensional distribution of DC circuit breakers and terminals is consistent with the actual situation of the substation;

[0059] The three-dimensional spatial distribution and connection relationship of the cables are consistent with the actual situation;

[0060] The cable is divided into a limited number of segments by DC circuit breakers, terminals, and loads.

[0061] For step 2), set virtual fault setting points in the 3D engine.

[0062] In a DC system, grounding incidents are detected on a branch-by-branch basis. Therefore, fault points are also set on a branch-by-branch basis, with a fault setting point added to each section of cable in each branch.

[0063] In a DC system, each branch is divided into a positive bus (referred to as the positive bus) side and a negative bus (referred to as the negative bus) side. Therefore, fault points are divided into two categories: fault points belonging to the positive bus side and fault points belonging to the negative bus side.

[0064] For step 3), the DC cable connects the power source and the load. From the power source to the load, the DC cable is segmented by several DC circuit breakers and terminals.

[0065] For any DC cable, which is composed of several DC circuit breakers and terminals connected in series, if both the DC circuit breakers and terminals are regarded as switching elements, then a "sequence of elements" is formed from the power source to the load; the elements closer to the power source are listed first.

[0066] Therefore, for any fault point, its preceding components must include several DC circuit breakers, and the preceding DC circuit breakers of any fault point form a "set".

[0067] For this "set", if any DC circuit breaker in it is in the open state, then the set is recorded as the open state; if every DC circuit breaker in it is in the connected state, then the set is recorded as the connected state; then any fault point will correspond to a set state of DC circuit breakers, thus establishing the association between the fault point and the set state of the upstream DC circuit breaker set.

[0068] For step 4), when conducting the simulation, click on the fault point and input the grounding resistance.

[0069] The grounding resistance can be 0 to 999 kΩ.

[0070] In this method, multiple grounding points can be set, that is, select one point from all fault points and input the grounding resistance, which represents the resistance of that point or the branch cable where that point is located to the ground.

[0071] For step 5),

[0072] For each fault point, if any one of the switches in the set associated with it is in the open state, the grounding resistance of the fault point is not included in the calculation and the fault point is ignored. If any one of the switches in the set associated with the fault point is in the closed state, the grounding resistance of the fault point is included in the calculation.

[0073] Let the grounding resistance of multiple fault points on the positive busbar side be R. x1 R x2 …R xn The grounding resistance of multiple fault points on the negative busbar side is R. y1 R y2 …R yn When the system is running normally, the voltage of the positive busbar to ground is U. + The voltage of the negative busbar to ground is U. -In a DC system, the balancing bridge resistors are R1 and R2, with R1 closer to the positive busbar and R2 closer to the negative busbar. The unbalanced bridge resistors are R3 and R4, with R3 closer to the positive busbar and R4 closer to the negative busbar. After grounding, the voltage between the positive busbar and ground is U1, and the voltage between the negative busbar and ground is U2. Therefore:

[0074] 1) Calculate R x1 R x2 …R xn The total parallel resistance R X ;

[0075] 2) Calculate R y1 R y2 …R yn The total parallel resistance R Y ;

[0076] 3) Let the ratio of the positive and negative busbar voltages to ground be K:

[0077]

[0078] but

[0079]

[0080] in

[0081]

[0082]

[0083]

[0084] U2=U1-(U + -U - )

[0085] For step 6), after the voltage calculation is completed, if the voltage of a certain branch is greater than zero, the branch will be highlighted in green in the 3D engine, and the color depth will vary with the magnitude of the positive bus voltage to ground U1.

[0086] If the voltage of a branch is less than zero, the branch will be highlighted in red, and the color depth will vary with the magnitude of the negative bus voltage to ground U2.

[0087] If the voltage of a branch is zero, it will be displayed in gray.

[0088] In summary, the technical solution of this invention establishes a three-dimensional model of the DC system of a substation, adds fault setting points to each cable segment of the DC system three-dimensional model, establishes the association relationship between each fault point and the status of the upstream switch set, sets the grounding resistance of each fault point in sequence, and calculates the voltage to ground of the positive and negative buses based on the grounding resistance and the status of the switch set associated with the fault point. This can display the operation status of the DC system under multiple grounding points and express the voltage magnitude in a three-dimensional visualization manner. This can help improve the maintenance work when the DC system fails, provide a foundation for establishing a more complete digital twin of the DC system, and also provide a new training method for DC systems.

[0089] This invention can be widely used in the field of operation and maintenance management or skills training of DC systems in substations.

Claims

1. A three-dimensional visualization simulation method for multi-point grounding faults in a substation DC system, comprising setting up a three-dimensional engine for constructing a three-dimensional model of the substation DC system, characterized in that... Includes the following steps: 1) Establish a three-dimensional model of the substation's DC system; 2) Add / set fault points on each cable segment of the DC system 3D model; 3) For each fault point, establish its association with the status of the upper-level switch set; 4) Click on multiple fault points in sequence and set the grounding resistance for each fault point in turn; 5) Calculate the voltage to ground of the positive and negative busbars based on the grounding resistance and the status of the switch set associated with the fault point; 6) Express voltage magnitude in a three-dimensional visualization; By establishing a three-dimensional model of the substation DC system, the correlation between the fault point and the status of the upstream switch set is constructed, the ground voltage of the positive and negative busbars associated with the fault point is determined, and the voltage of each branch is displayed in a three-dimensional mode using different colors according to the magnitude of the ground voltage, thereby realizing the display of the operation of the DC system under multiple grounding conditions in a three-dimensional visualization manner. In step 5), let the grounding resistance of multiple fault points on the positive busbar side be Rx1, Rx2, ..., Rxn, and the grounding resistance of multiple fault points on the negative busbar side be Ry1, Ry2, ..., Ryn. During normal system operation, the voltage to ground of the positive busbar is U+, and the voltage to ground of the negative busbar is U-. The balanced bridge resistors in the DC system are R1 and R2, with R1 closer to the positive busbar side and R2 closer to the negative busbar side. The unbalanced bridge resistors in the DC system are R3 and R4, with R3 closer to the positive busbar and R4 closer to the negative busbar side. After grounding, the voltage to ground of the positive busbar is U1, and the voltage to ground of the negative busbar is U2. Then: 1) Calculate the total parallel resistance RX of Rx1, Rx2, ..., Rxn; 2) Calculate the total parallel resistance RY of Ry1, Ry2, ..., Ryn; 3) Let the ratio of the positive and negative busbar voltages to ground be K: but in U2 = U1 - (U+ - U-).

2. The three-dimensional visualization simulation method for multi-point grounding faults in a substation DC system according to claim 1, characterized in that: The three-dimensional model of the substation DC system includes at least the power supply, cables, DC circuit breakers, terminals, and DC loads. The power supply and DC load are modeled using abstract methods. Cables, DC circuit breakers, and terminals must be represented by realistic models. The three-dimensional distribution of DC circuit breakers and terminals is consistent with the actual situation of the substation; The three-dimensional spatial distribution and connection relationship of the cables are consistent with the actual situation; The cable is divided into a limited number of segments by DC circuit breakers, terminals, and loads.

3. The three-dimensional visualization simulation method for multi-point grounding faults in a substation DC system according to claim 1, characterized in that: In the DC system, grounding events are detected on a branch-by-branch basis; fault points are set on a branch-by-branch basis, and a fault setting point is added to each cable segment of each branch.

4. The three-dimensional visualization simulation method for multi-point grounding faults in a substation DC system according to claim 1, characterized in that: The fault points are divided into positive busbar side fault points and negative busbar side fault points.

5. The three-dimensional visualization simulation method for multi-point grounding faults in a substation DC system according to claim 1, characterized in that: In step 3), any DC cable is composed of several DC circuit breakers and terminals connected in series via a cable; From the power source to the load, the DC cable is segmented by several DC circuit breakers and terminals; If both the DC circuit breaker and the terminal block are considered as switching elements, then a "sequence of elements" is formed from the power source to the load; Components closer to the power source are listed first; For any fault point, its preceding components include several DC circuit breakers, and the preceding DC circuit breakers of any fault point form a "set".

6. The three-dimensional visualization simulation method for multi-point grounding faults in a substation DC system according to claim 5, characterized in that... In step 3), for the "set", if any DC circuit breaker in it is in the open state, then the set is recorded as the open state; If every DC circuit breaker in the set is in a connected state, then the set is denoted as the connected state. Each fault point corresponds to a set state of DC circuit breakers, thus establishing the association between the fault point and the set state of the upstream DC circuit breakers.

7. The three-dimensional visualization simulation method for multi-point grounding faults in a substation DC system according to claim 1, characterized in that... In step 4), when conducting the simulation, click on the fault point and input the grounding resistance; Its grounding resistance ranges from 0 to 999 kΩ; Select one point from all fault points and enter the grounding resistance, which represents the resistance of that point or the branch cable to ground.

8. The three-dimensional visualization simulation method for multi-point grounding faults in a substation DC system according to claim 1, characterized in that... In step 5), for each fault point, if any of the switches in the set associated with it are in the open state, the grounding resistance of the fault point is not included in the calculation and the fault point is ignored. If any of the switches in the set associated with the fault point are in the closed state, the grounding resistance of the fault point is included in the calculation.

9. The three-dimensional visualization simulation method for multi-point grounding faults in a substation DC system according to claim 1, characterized in that... In step 6), after the voltage calculation is completed, if the voltage of a certain branch is greater than zero, the branch will be highlighted in green in the 3D engine, and the color depth will vary with the magnitude of the positive bus voltage to ground U1. If the voltage of a branch is less than zero, the branch will be highlighted in red, and the color depth will vary with the magnitude of the negative bus voltage to ground U2. If the voltage of a branch is zero, it will be displayed in gray.

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