A power supply and distribution system relay protection scheme optimization configuration method

Abstract

The application provides a power distribution system relay protection scheme optimization configuration method, relates to the technical field of relay protection, determines the power equipment loop of the system needing to be configured with relay protection, draws the power equipment time-current characteristic curve, the power equipment no-load starting thermal limit curve, the full-load starting thermal limit curve and the cable limit curve; obtains the relay protection curve of the loop where the power equipment is located under each voltage grade, and each voltage grade relay protection curve includes the tripping time-current curve of each level circuit breaker; each level relay protection curve is set level by level, and the main power distribution loop relay protection curve is adjusted to obtain and reversely calculate the parameter value. Each type of protection such as quick break, overload and motor locked rotor and the tripping relationship between the protections configured in each voltage grade in the whole power system are checked in the same coordinate system, so that the complete protection coordination value checking of each level is achieved, and the protection input value after checking is obtained by reversely calculating and adjusting each type of curve in the coordinate system.

Description

Technical Field

[0001] This invention relates to the field of relay protection technology, specifically to a method for optimizing the configuration of relay protection schemes in power supply and distribution systems. Background Technology

[0002] Large petrochemical plants typically have complex power distribution systems with a wide variety of electrical equipment. When configuring relay protection systems, multiple operating conditions must be considered, making it challenging to ensure both simplicity and reliability of the relay protection device configuration. Furthermore, electrical equipment within petrochemical production facilities often operates in high-risk environments such as high voltage, high temperature, high humidity, and high corrosion, and may even be within explosion hazard zones. Therefore, the proper configuration of electrical relay protection systems is crucial for promptly cutting off current in the event of faults such as short circuits, overvoltages, undervoltages, and overloads in the power distribution system and equipment, preventing the accident from escalating, and restoring normal operation as quickly as possible, thereby improving the reliability and stability of the power system.

[0003] Traditional petrochemical plant power supply and distribution system relay protection settings generally adopt the formula method, that is, according to the relevant formulas in national standards, such as "DL / T 584-2007 3-110KV power grid relay protection device operation procedure" and "GB 14285-2006 technical specification for relay protection and safety automatic devices", the reliability coefficient within a certain range is selected based on the fault point current calculation results, and the operating current setting value of the relay protection system is calculated.

[0004] However, the selection of a reliability coefficient is often difficult to determine due to the different types of electrical loads. An excessively high reliability coefficient can lead to untimely tripping of faulty equipment in hazardous areas of the oil and petrochemical industry, potentially causing disasters, or it can cause cascading tripping, expanding the scope of power system faults. Conversely, an excessively low reliability coefficient can cause malfunctions in electrical loads under normal operating conditions, resulting in safety accidents and economic losses.

[0005] Therefore, a new method for optimizing relay protection configuration is needed, which can more intuitively identify the problems with existing setting parameters and select the required setting parameter values ​​for protection. Summary of the Invention

[0006] Based on the problems existing in the traditional relay protection setting methods of power supply and distribution systems in petrochemical plants, the present invention provides the following technical solution:

[0007] 1. A method for optimizing the configuration of relay protection schemes in a power supply and distribution system, characterized in that:

[0008] Includes the following steps:

[0009] Step 1: Determine the electrical equipment circuits that require relay protection configuration in the system. The electrical equipment circuits include the main circuit and the successive circuits derived from the main circuit. The main circuit is either the main transformer circuit or the feeder circuit. The successive circuits include circuits related to the first voltage level, circuits related to the second voltage level, ..., circuits related to the Nth voltage level (N≥2). The voltage levels corresponding to the above voltage level-related circuits are the first voltage level, the second voltage level, ..., the Nth voltage level, respectively.

[0010] Assume that the circuit related to voltage level i contains transformer i, electrical equipment i, and cable i;

[0011] Step 2: Under a fixed coordinate system, plot the time-current characteristic curve of electrical equipment N, the no-load start thermal limit curve of electrical equipment N, the full-load start thermal limit curve of electrical equipment N, and the limit curve of cable N; obtain the relay protection curve of N-level electrical equipment, wherein the relay protection curve of N-level electrical equipment includes at least the tripping time-current curve of N-level circuit breaker.

[0012] Step 3: Under the fixed coordinate system, for transformer N, plot the inrush current point and fault curve of transformer N, and obtain the rated current of transformer N; mark the inrush current point of transformer N under the fixed coordinate system, and adjust the N-level transformer comprehensive protection setting curve; the N-level electrical equipment relay protection curve and the N-level transformer comprehensive protection setting curve together form the N-level relay protection curve corresponding to the N-level voltage level related circuit;

[0013] Step 4: Plot the time-current characteristic curve of electrical equipment N-1, the no-load start thermal limit curve of electrical equipment N-1, the full-load start thermal limit curve of electrical equipment N-1, the limit curve of cable N-1, the inrush current point of transformer N-1, and the fault curve of transformer N-1 under the fixed coordinate system. Based on the N-level relay protection curve, obtain the N-1 level relay protection curve.

[0014] Step 5: Repeat Step 4 to obtain the i-level relay protection curve step by step until the relay protection curves of the first voltage level related circuit, the second voltage level related circuit, ..., the N-level voltage level related circuit are all set, and obtain the first-level relay protection curve, the second-level relay protection curve, ..., the N-level relay protection curve.

[0015] Step Six: Based on the above-mentioned primary relay protection curve, secondary relay protection curve, ..., N-level relay protection curve, calculate the setting parameter values ​​of the above-mentioned relay protection curves in reverse.

[0016] Preferably, the tripping time-current curve of the N-level circuit breaker is located to the upper right of the time-current characteristic curve of the electrical equipment N, and to the lower left of the no-load starting thermal limit curve and the full-load starting thermal limit curve of the electrical equipment N.

[0017] Preferably, the tripping time-current curve of the N-level circuit breaker includes at least a continuous instantaneous region, a transition region, a short delay region, and a long delay region.

[0018] Preferably, the action time of the instantaneous zone is less than or equal to 0.2s and the action current ranges from 1.5 to 15I. eN , where I eN The rated current of electrical equipment N; the adjustable range of the operating current threshold value of the short delay zone is 1-10I. eN The operating current in the long delay region tends to be 1.1I. eN .

[0019] Preferably, the N-level electrical equipment relay protection curve also includes the N-level fuse fusing time-current curve, and the N-level fuse fusing time-current curve intersects with the N-level circuit breaker tripping time-current curve.

[0020] Preferably, the relay protection curve of the N-1 level electrical equipment shall at least meet the following conditions:

[0021] ① The relay protection curve for the N-1 level electrical equipment is located to the upper right of the relay protection curve for the N level electrical equipment;

[0022] ② The relay protection curve of the N-1 level electrical equipment is located to the upper right of the N-1 time-current characteristic curve of the electrical equipment;

[0023] ③The relay protection curve for N-1 level electrical equipment is located to the lower left of the N-1 full-load start-up thermal limit curve of the electrical equipment;

[0024] ④ There is a time delay between the N-1 level relay protection curve and the N level relay protection curve.

[0025] Preferably, the method for setting the time delay between the N-1 level relay protection curve and the N level relay protection curve is as follows: take any identical horizontal coordinate and adjust the difference between the vertical coordinates of the N-1 level relay protection curve and the N level relay protection curve.

[0026] Preferably, the delay is at least 0.02s.

[0027] Preferably, the N-level transformer comprehensive protection setting curve includes a high-voltage side comprehensive protection setting curve and a low-voltage side comprehensive protection setting curve, both of which are located above the N-level excitation inrush current point of the transformer.

[0028] Preferably, the electrical equipment in the step-by-step circuit is an electric motor.

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

[0030] The present invention provides an optimized configuration method for relay protection schemes in power supply and distribution systems. It utilizes current-time curves to classify various electrical equipment, and uniformly displays and analyzes the normal operating current, abnormal operating condition tolerance limits, circuit breaker breaking time, and fault tolerance limits of the equipment to determine optimized relay protection configuration schemes for various petrochemical plant electrical equipment. It depicts complex relay protection inverse-time formulas and electrical equipment fault tolerance limits on a unified current-time graph, allowing for a clear view of existing parameter settings. By adjusting the curves on the current-time graph, the application program can back-calculate the required setting parameters for each protection. This allows for the verification of various types of protection, such as instantaneous overload and motor stall protection, as well as the tripping relationships between all protections configured in the entire power system, achieving complete verification of the coordination settings for each level of protection. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the time-current characteristic curve of a motor in an optimized configuration method for relay protection schemes in a power supply and distribution system.

[0032] Figure 2 This is a schematic diagram of obtaining the N-level relay protection curve based on the time-current characteristic curve of the motor in a method for optimizing the configuration of relay protection schemes in a power supply and distribution system.

[0033] Figure 3 This is a schematic diagram of the transformer integrated protection setting curve in an optimized configuration method for relay protection schemes in a power supply and distribution system, wherein circuit breakers are used on both the high-voltage and low-voltage sides;

[0034] Figure 4 This is a transformer comprehensive protection setting curve under the condition that the transformer uses a contactor on the low-voltage side in a method for optimizing the configuration of relay protection schemes in a power supply and distribution system.

[0035] Figure 5 It is a set parameter value obtained by inversion calculation in the optimization configuration method of relay protection scheme of power supply and distribution system;

[0036] Figure 6 This is a flowchart of a method for optimizing the configuration of relay protection schemes in power supply and distribution systems. Detailed Implementation

[0037] To make the objectives and technical solutions of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention.

[0038] In the description of this application, it should be understood that the terms indicating orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0039] Electrical equipment such as motors, transformers, cables, and distribution busbars are set with limit values ​​for normal operating current. If the operating current does not exceed the limit value of these power distribution equipment, there will be no faults such as short circuits or overloads, and these equipment will not be damaged or burned. However, if an excessive current flows through these electrical equipment, such as a short circuit current, the corresponding relay protection system must act in time to cut off the fault current.

[0040] Meanwhile, to ensure the selectivity of power grid relay protection, the settings of relay protection between upstream and downstream power grids (including same-level and upstream / downstream power grids) should follow the principle of hierarchical coordination and meet the requirements of selective protection. That is, when a downstream line or component fails, the relay protection settings for the faulty line or component must be coordinated with the relay protection settings for the upstream line or component in terms of sensitivity and operating time, to ensure selective fault isolation when a power grid fault occurs. When a short circuit occurs in equipment or a line in the power system, its relay protection should only disconnect the faulty equipment or line from the power system, and should not directly trigger the upstream power grid relay protection.

[0041] This invention provides a method for optimizing the configuration of relay protection schemes in power supply and distribution systems. Through graphical adjustment and parameter inversion, it facilitates obtaining relay protection at various voltage levels. Due to the extremely high complexity of actual power systems, only the simplest power model is described here, such as... Figure 6 As shown, this invention demonstrates the optimized configuration method for relay protection schemes in power supply and distribution systems.

[0042] Specifically, the following steps are included:

[0043] Step 1: Identify the electrical equipment circuits that require relay protection configuration in the system. This specifically includes the main circuit and the successive circuits derived from the main circuit. The main circuit includes transformer circuits or feeder circuits. The successive circuits include circuits related to the first voltage level, circuits related to the second voltage level, ..., circuits related to the Nth voltage level (N≥2). The voltage levels corresponding to the above voltage level-related circuits are the first voltage level, the second voltage level, ..., the Nth voltage level, respectively, with their voltage values ​​decreasing sequentially. The Nth voltage level is generally the lowest voltage level in the power supply and distribution system.

[0044] It is important to understand that in conventional power supply and distribution systems, there are multiple voltage levels. The commonly used voltage levels include the first voltage level (220kV), the second voltage level (110kV or 66kV), the third voltage level (35kV, 20kV), the fourth voltage level (10kV or 6kV), and the fifth voltage level (0.4kV, 0.38kV or 0.22kV). The fifth voltage level is generally the lowest voltage level in the power supply and distribution system. There must be a corresponding transformer assembly between any two adjacent voltage levels.

[0045] Each voltage level-related circuit includes its corresponding transformer circuit or feeder circuit, as well as several end-user electrical load circuits, which include common electrical equipment such as motors, lighting equipment, heaters, and other equipment.

[0046] In this embodiment, for the purpose of introducing the method, the case of multiple end-load circuits is not considered. Therefore, each voltage level-related circuit includes its corresponding transformer, electrical equipment, and cable. For ease of explanation, it is assumed that the i-th voltage level-related circuit contains transformer i, electrical equipment i, and cable i.

[0047] Step 2: Calculate the fault current at each point in the power system in each type of electrical equipment circuit, including the bus short-circuit current and the fault current of the electrical equipment; calculate the rated operating current of the electrical equipment, such as the rated current of the cable and the rated current of the transformer; in this embodiment, the electrical equipment is exemplified by an electric motor.

[0048] Based on the starting performance of motor N in the relevant circuit of voltage level N, the time-current characteristic curve, no-load starting thermal limit curve, and full-load starting thermal limit curve of motor N are plotted in a fixed coordinate system. For cable N, the rated current of cable N is obtained, and the limit curve of cable N is plotted in the Nth coordinate system, as follows: Figure 1 As shown in the image.

[0049] like Figure 1 The time-current characteristic curve of motor N shown is illustrated, where the horizontal axis represents the current value and the vertical axis represents the time value. Figure 1 Curve A in the figure represents the time-current characteristic curve of motor N, that is, the curve of the current of motor N changing with time after starting.

[0050] In curve A, when motor N is initially energized, the system starts operating from the origin. Since the motor rotor is still stationary at this point, the current rapidly rises to the right along curve A to its furthest point during startup. This current is called the peak starting inrush current, which is Ip in the diagram. At this point, Ip is greater than the motor's rated current, typically Ip = 10⁻¹⁴Ie (see motor datasheet for different motors), where Ie is the motor's rated current. As the motor rotor begins to rotate, the motor current moves to the left along curve A to reach the starting region, where it is Ia, the motor's starting current. The starting current is equal to 4⁻⁸.4Ie (see motor datasheet for different motors). After the motor has started, the motor current moves to the upper left along curve A, reaching the rated operating region, where the current is the rated current Ie. The time from startup to reaching the rated current In is Ta. Afterward, under normal conditions, the motor will continue to operate at the rated current Ie.

[0051] Under normal circumstances, motors are mostly started under light load. After starting, the motor is then operated under full load to reach its rated power.

[0052] exist Figure 1 In the diagram, curve B is the full-load starting thermal limit curve, with point P1 being the full-load starting thermal limit point. Since this point is not an absolutely fixed value, it is extended to form the full-load starting thermal limit curve. Full-load starting means starting the motor directly under full load. Generally, the starting current is very large, which can easily impact the power grid. The full-load starting thermal limit curve shows the limit time for the motor to start under full load at this current. If the motor operates under a fixed current for more than this time (i.e., the actual time minus the current point is above the right of the full-load starting thermal limit curve), the power grid is likely to burn out. For example, point P1 in the diagram is the full-load starting thermal limit point, with coordinates (295.1A, 2.81s). This means that under full-load starting, when the current through the motor is maintained at 295.1A, the longest duration is 2.81s. If it exceeds 2.81s (e.g., 3s, where coordinates (295.1A, 3s) are above the right of the full-load starting thermal limit curve), the motor is likely to burn out.

[0053] Curve C is the no-load starting thermal limit curve, where point P2 is the no-load starting thermal limit point. Since this point is not an absolutely fixed value, it is extended to the no-load starting thermal limit curve. Similar to the full-load starting thermal limit curve, the no-load starting thermal limit curve shows the limit time of the motor under the current when starting under no-load. If the motor operates under a fixed current for more than this time (i.e., the actual time minus the current point is in the upper right of the no-load starting thermal limit curve), the power grid is likely to burn out.

[0054] Curve D is the cable limit curve under the motor circuit, showing the limit time of the cable used in the downstream circuit under this current. When the current passing through the cable continues to exceed this time (i.e., the actual time-current point is above the right of the no-load starting cable time-current limit curve), the cable is prone to burnout.

[0055] Based on the motor time-current characteristic curve, the motor no-load start and full-load start thermal limit curves, and the cable limit curve, the N-level electrical equipment relay protection curve is obtained in the coordinate system in step two. The N-level electrical equipment relay protection curve includes at least the N-level circuit breaker tripping time-current curve, and may also include the fuse melting time-current curve, the time-current curve of the electrical equipment integrated protection device, etc.

[0056] like Figure 2 As shown in the figure, curve E between curves A and B is the circuit breaker tripping time-current curve after setting. By adjusting the curve type, value range, value setting, time delay, and accuracy of the overcurrent and instantaneous overcurrent protection parameters of each level of relay protection phase-to-phase, ground, and negative sequence protection, the set circuit breaker tripping time-current curve can be composed of various types of curves, including instantaneous, short-delay, and long-delay curves, between 0.01 seconds and 1K seconds. This clearly shows whether the circuit breaker tripping time-current curve can avoid the normal operating current value of the motor or other protected equipment throughout the entire time period, and also whether the circuit breaker tripping time-current curve is too large, which may lead to the risk of damage to the protected equipment or the possibility of over-tripping.

[0057] Specifically, such as Figure 2 As shown by curve E, the lower left of the circuit breaker tripping time-current curve at curve E represents the non-tripping region, which is the normal operating region where the circuit breaker closes to carry current. Any point on curve E indicates that when the duration of the current value passing through the circuit breaker reaches the limit time corresponding to that current value, the circuit breaker will trip. The upper right of curve E represents the tripping region, meaning that when time T enters the upper right of this curve (tripping region), the circuit breaker will inevitably trip.

[0058] Based on the time-current characteristic curve of the motor (Curve A), the tripping time-current curve of the circuit breaker (Curve E) is adjusted so that Curve E is located to the upper right of Curve A while being to the lower left of both Curve B and Curve C. The specific adjustment methods include instantaneous zone E1, transition zone E2, short delay zone E3, and long delay zone E4.

[0059] The adjustment principle of the instantaneous zone E1 is as follows: when the current through the circuit breaker and motor is too large, it will trip instantaneously to ensure circuit safety. The instantaneous zone E1 is actually a definite-time protection, meaning that its tripping time is a fixed value regardless of the current. The tripping time T of the instantaneous zone E1 is...E1 Less than or equal to 0.2s, tripping current I E1 Greater than or equal to 1.05I p Generally, it is 1.5-15I. e In this invention, the tripping time T of E1 E1 The value is 0.2. The transition region E2 is almost parallel to the full-load start-up thermal limit curve. It belongs to inverse-time protection and is the transition area between the instantaneous region E1 and the short-delay region E3. It is used to protect against overload and small-scale short circuits in the circuit. Generally, the larger the current, the shorter the tripping time. The adjustable range of the operating current threshold value of the short-delay region E3 is 1-10 times I. e The inverse time limit action time T can be adjusted. E3 It is adjusted and confirmed according to the actual situation; the short delay zone is mainly set to consider the selectivity between the upper and lower level protection nodes of the circuit. The short-circuit delay is actually for matching between the upper and lower levels. For example, if the short circuit point is below the lower terminal of the lower-level switch, if the upper-level switch does not have a short delay, the upper and lower level switches may operate simultaneously, which may cause the area connected to the upper-level switch to lose power. Once the lower-level switch operates, the short circuit point is cut off, there is no short-circuit current in the system, and naturally the upper-level switch will not operate. The delay is to allow the lower-level switch to operate first, and also to ensure that if the lower-level switch cannot interrupt the short-circuit current, the upper-level switch can reliably interrupt the short-circuit current after the delay, preventing the fault from escalating. The long delay zone E4 is for overload long delay, in which the operating current I under normal circumstances is... E4 It generally eventually approaches 1.1I. e Its action time T E4 It is adjusted and confirmed based on the actual situation.

[0060] Based on the above principles, the circuit breaker tripping time-current curve E can be adjusted in the coordinate system. In addition, a fuse blowing time-current curve can also be set, such as... Figure 2 As shown in curve F, a fuse is a common current protection device. When the current exceeds the set value for a certain period of time, the heat generated by the fuse itself melts the fusible element, thus breaking the circuit. The fuse's fusing time-current curve reflects its fusing nature, that is, under what conditions it will blow. Simultaneously, the fuse has an inverse-time characteristic, meaning that the larger the current, the shorter the fusing time. Therefore, the fuse's fusing time-current curve itself is also an inverse-time-current curve. Generally, the circuit breaker has already tripped before the fuse blows, unless the current is too large (or there is a short circuit), and the current value exceeds the intersection of curve E (circuit breaker tripping time-current curve) and curve F (fuse fusing time-current curve) shown in the figure. At this point, the fuse blows instantaneously, protecting the circuit.

[0061] Step 3: In a fixed coordinate system, for transformer N, plot the inrush current point and fault curve of transformer N according to the parameters provided by the transformer manufacturer, and obtain the rated current of transformer N; mark the inrush current point of transformer N and the cable N curve in the fixed coordinate system, and adjust the comprehensive protection setting curve of the N-level transformer. For example... Figure 3 As shown, the N-level transformer's integrated protection setting curve includes a high-voltage side integrated protection setting curve and a low-voltage side integrated protection setting curve. Circuit breakers are used as relay protection devices on both the high-voltage and low-voltage sides. Simultaneously, contactors and fuses can also be used as relay protection devices on the low-voltage side, such as... Figure 4 As shown in the image.

[0062] The transformer has the function of stepping up or stepping down voltage. Therefore, there are separate integrated relay protection devices for the high-voltage side and the low-voltage side. The integrated protection setting curves of the high-voltage side and the low-voltage side are both located above the N-level excitation inrush current point of the transformer. The N-level electrical equipment relay protection curve and the N-level transformer integrated protection setting curve together form the N-level relay protection curve corresponding to the N-level voltage level related circuit.

[0063] Step 4: Obtain the starting performance of motor N-1 in the circuit above the Nth voltage level, i.e., the (N-1)th voltage level. Plot the time-current characteristic curve, no-load starting thermal limit curve, and full-load starting thermal limit curve of motor N-1 in a fixed coordinate system. For cable N-1, obtain the rated current of cable N-1 and plot the limit curve of cable N-1 in the N-1 coordinate system. Based on the protection curve of the N-level electrical equipment, the time-current characteristic curve, no-load starting thermal limit curve, full-load starting thermal limit curve of motor N-1, and the limit curve of cable N-1, obtain the relay protection curve of the N-1 level electrical equipment. The relay protection curve of the N-1 level electrical equipment must at least meet the following conditions:

[0064] ① The relay protection curve for N-1 level electrical equipment is located to the upper right of the relay protection curve for N-1 level electrical equipment; ② The relay protection curve for N-1 level electrical equipment is located to the upper right of the N-1 time-current characteristic curve of the motor; ③ The relay protection curve for N-1 level electrical equipment is located to the lower left of the full-load starting thermal limit curve; ④ Measure the difference in the vertical axis between the same horizontal axis of the relay protection curve for N-1 level electrical equipment and the relay protection curve for N-1 level electrical equipment, and calculate the time delay of the action of the two adjacent protection levels. The time delay is at least 0.02s.

[0065] For transformer N-1, the inrush current point and fault curve of transformer N-1 are plotted according to the parameters provided by the transformer manufacturer, and the rated current of transformer N-1 is obtained. The inrush current point and cable N-1 curve of transformer N-1 are marked in a fixed coordinate system, and the comprehensive protection setting curve of N-1 transformer is adjusted in combination with the comprehensive protection setting curve of N-1 transformer.

[0066] Because protection systems can sometimes malfunction, and in some cases, a brief, instantaneous surge in current occurs in the power system, the relay protection system does not need to operate. This surge is likely very short-lived and harmless. In such cases, the relay protection system needs to be programmed with a delay to prevent frequent malfunctions that could cause the system to trip repeatedly. On the other hand, when a fault occurs in a downstream system, the relay protection system should try to isolate the fault at the nearest point, rather than using the upstream main switch to isolate the fault (which would lead to a large-scale power outage). Therefore, there needs to be a sequence of actions between upstream and downstream relay protection systems (reflected by a delay).

[0067] By selecting two points with the same vertical coordinate on the two curves and measuring the horizontal coordinate, we can determine the time delay between the two curves under the same current.

[0068] Step 5: Referring to Step 4, obtain the relay protection curve of level i level by level until the relay protection curves of the relevant circuits of the first voltage level, the relevant circuits of the second voltage level, ..., the relevant circuits of the Nth voltage level have been set, and the comprehensive protection setting curve of the main transformer in the main circuit has also been set.

[0069] Step Six: For the N-level relay protection curve, N-1-level relay protection curve, ..., i-level relay protection curve, ..., second-level relay protection curve, first-level relay protection curve, and main transformer integrated protection setting curve, calculate the setting parameter values ​​of the above relay protection curves in reverse. The obtained setting parameter values ​​are as follows: Figure 5 As shown.

[0070] This method enables electrical engineers to easily and efficiently perform protection setting calculations and coordination analyses. It allows for the rapid identification of potential protection design problems and the making of appropriate decisions to improve system reliability and stability, reduce the number of protection configurations, and meet the requirements for speed, selectivity, and reliability of relay protection.

[0071] The above are merely embodiments of the present invention, described in a relatively specific and detailed manner, but should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, such as changing the movable structure; these obvious substitutions all fall within the protection scope of the present invention.

Claims

1. A method for optimizing the configuration of relay protection schemes in a power supply and distribution system, characterized in that: Includes the following steps: Step 1: Identify the electrical equipment circuits in the power supply and distribution system that require relay protection configuration. These circuits include a main circuit and successive circuits derived from it. The main circuit is either a main transformer circuit or a feeder circuit. The successive circuits include circuits related to the first voltage level, circuits related to the second voltage level, ..., ... N Voltage level related circuits N＞ 2. The voltage levels corresponding to the above voltage level-related circuits are the first voltage level, the second voltage level, ..., the Nth voltage level, respectively; Setting the first i There is a transformer in the voltage level related circuit. i Electrical equipment i and cables i ; Step 2: Draw the electrical equipment in a fixed coordinate system. N Time-current characteristic curve, electrical equipment N No-load start-up thermal limit curve, electrical equipment N Full-load start-up thermal limit curve and cable N Limit curve; obtaining N The relay protection curve of the Class A electrical equipment, the N The relay protection curve for Class A electrical equipment should include at least the following: N Tripping time-current curve of circuit breaker; Step 3: In the fixed coordinate system, for the transformer N Draw a transformer N Inrush current point and transformer N Fault curves, obtaining transformer N Rated current; Mark the transformer in the fixed coordinate system N Excitation inrush current point, and adjust N Transformer integrated protection setting curve; The N Level 1 electrical equipment relay protection curve and the above N The integrated protection setting curves of the first-stage transformer together constitute the first... N Voltage level related circuits N Level 1 relay protection curve; Step 4: Draw the electrical equipment in the fixed coordinate system. N -1 Time-current characteristic curve, electrical equipment N -1 No-load start-up thermal limit curve, electrical equipment N -1 Full-load start-up thermal limit curve, cable N -1 Limit Curve, Transformer N -1 Excitation Inrush Current Point and Transformer N -1 fault curve, based on the N Level 1 relay protection curve, obtain N -1 level relay protection curve; Step 5: Repeat Step 4 to obtain the relay protection curves for level i level by level, until the relevant circuits for the first voltage level, the relevant circuits for the second voltage level, ..., the ... N The relay protection curves for all voltage level-related circuits have been set, and the primary relay protection curves, secondary relay protection curves, ... have been obtained. N Level 1 relay protection curve; Step Six: Based on the above-mentioned primary relay protection curves, secondary relay protection curves, ... N The setting parameter values ​​of the above relay protection curves are calculated in reverse from the level-1 relay protection curve.

2. The method for optimizing the configuration of relay protection schemes in a power supply and distribution system according to claim 1, characterized in that: The N The tripping time-current curve of the circuit breaker is located in the electrical equipment. N The time-current characteristic curve is located to the upper right and above the electrical equipment. N No-load start-up thermal limit curve, electrical equipment N The lower left of the full-load start-up thermal limit curve.

3. The method for optimizing the configuration of relay protection schemes in a power supply and distribution system according to claim 1, characterized in that: The N The tripping time-current curve of a circuit breaker should include at least a continuous instantaneous zone, a transition zone, a short delay zone, and a long delay zone.

4. The method for optimizing the configuration of relay protection schemes in a power supply and distribution system according to claim 3, characterized in that: The action time of the instantaneous zone is less than or equal to 0.2s and the action current ranges from 1.5 to 15. I nN ,in I nN For electrical equipment N The rated current; the adjustable range of the operating current threshold value in the short delay zone is 1-10InN; the operating current in the long delay zone tends to be 1.

1. I nN .

5. The method for optimizing the configuration of relay protection schemes in a power supply and distribution system according to claim 1, characterized in that: The N The relay protection curves for Class A electrical equipment also include N The fusing time-current curve of the Class A fuse, the N The fusing time-current curve of the stage fuse is compared with the above. N The tripping time-current curves of the circuit breaker intersect.

6. The method for optimizing the configuration of relay protection schemes in a power supply and distribution system according to claim 1, characterized in that: The N The relay protection curve for Class -1 electrical equipment must meet at least the following conditions: ①The N The relay protection curve for -1 level electrical equipment is located in the... N The upper right corner of the relay protection curve for Class A electrical equipment; ②The N The relay protection curve for Class -1 electrical equipment is located at the electrical equipment. N -1 The upper right of the time-current characteristic curve; ③ N The relay protection curve for Class -1 electrical equipment is located at the electrical equipment. N -1 The lower left of the full-load start-up thermal limit curve; ④ The N -1 level electrical equipment relay protection curve and the above N There is a time delay between the relay protection curves.

7. The method for optimizing the configuration of relay protection schemes in a power supply and distribution system according to claim 6, characterized in that: The N -1 level electrical equipment relay protection curve and the above N The method for setting the time delay between the relay protection curves of Class A electrical equipment is as follows: Take any identical horizontal axis and adjust... N -1 level electrical equipment relay protection curve and the above N The difference in the vertical axis of the relay protection curve of the Class A electrical equipment.

8. The method for optimizing the configuration of relay protection schemes in a power supply and distribution system according to claim 7, characterized in that: The delay is at least 0.02s.

9. The method for optimizing the configuration of relay protection schemes in a power supply and distribution system according to claim 1, characterized in that: The N The integrated protection setting curves of the transformer include the high-voltage side integrated protection setting curve and the low-voltage side integrated protection setting curve, and both are located within the transformer. N Above the excitation inrush point.

10. The method for optimizing the configuration of relay protection schemes in a power supply and distribution system according to claim 1, characterized in that: The electrical equipment in the step-by-step circuit is an electric motor.

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