Control method of overcurrent relay for main protection and computing device for performing the same and distribution system equipped with the same

Abstract

A method for controlling a potential protection overcurrent relay, a computing device for performing the same, and a power distribution system equipped with the same are disclosed. A method according to one disclosed embodiment includes the steps of measuring a current flowing through a potential protection relay and a current flowing through a backup protection relay in a power distribution system, respectively; calculating the operating time of the backup protection relay based on the current flowing through the backup protection relay and a pickup current set in the backup protection relay; calculating the pickup current of the potential protection relay based on the operating time of the backup protection relay and the current flowing through the potential protection relay; and calculating the operating time of the potential protection relay based on the pickup current of the potential protection relay and the current flowing through the potential protection relay.

Description

Technology Field

[0001] An embodiment of the present invention relates to a control technology for a potential protection overcurrent relay. Background Technology

[0003] Recently, policies promoting the use of decarbonized energy to address climate change issues are being adopted. Consequently, power companies are reducing the proportion of conventional power sources and increasing the proportion of Distributed Energy Resources (DER) (or "distributed power sources"). However, when distributed energy sources are connected to a distribution system, the operation of existing over-current relays (OCRs) is affected depending on the location of penetration by the distributed energy sources.

[0004] FIG. 1 is a diagram illustrating a state in which an overcurrent relay (OCR) malfunctions due to a conventional distributed power source (DER). Referring to FIG. 1, a power distribution system (50) may include a main power source (51) and a power line (53). The power distribution system (50) may include multiple power lines, but for convenience of explanation, only one power line (53) is shown here. A potential protection overcurrent relay (OCR2) (hereinafter referred to as the potential protection relay) and a backup protection overcurrent relay (OCR1) (hereinafter referred to as the backup protection relay) may be provided on the power line (53).

[0005] Here, it is assumed that a fault occurs at a fault point in the power distribution system. If there is no distributed power source (DER), the fault current flows along the first path (P1). At this time, the current flowing through the primary protection relay (OCR2) and the backup protection relay (OCR1) is the same, but since the primary protection relay (OCR2) is set to be more sensitive, only the primary protection relay (OCR2) operates.

[0006] However, as illustrated in FIG. 1, if a distributed power source (DER) is installed in the power distribution system (50), a fault current flowing along a second path (P2) is added in addition to the first path (P1). In this case, the fault current flowing through the potential protection relay (OCR2) increases, and the fault current flowing through the backup protection relay (OCR1) decreases due to the influence of the distributed power source (DER).

[0007] As a result, the operating time of the primary protection relay (OCR2) increases and the operating time of the backup protection relay (OCR1) decreases, causing the Coordination Time Interval (CTI) between the two overcurrent relays to change, which leads to a malfunction in which the backup protection relay (OCR1) does not operate at the set time when the primary protection relay (OCR2) fails.

[0008] In addition, when a Superconducting Fault Current Limiter (SFCL) is additionally placed in the power distribution system (50), the fault current flowing through the backup protection relay (OCR1) of the first path (P1) is further reduced, and the fault current flowing through the potential protection relay (OCR2) of the second path (P2) is further increased, so that the adjustment time interval between the two overcurrent relays changes more significantly, and as a result, the operation of the backup protection relay (OCR1) is further delayed when the potential protection relay (OCR2) fails.

[0009] FIG. 2 is a diagram illustrating the state in which the adjustment time interval between two overcurrent relays changes due to the additional placement of distributed power sources and SFCLs. Here, OCR2 represents the time-current characteristic curve of the primary protection relay, and OCR1 represents the time-current characteristic curve of the backup protection relay. Also, M is the measured current (I) of the overcurrent relay. rms ) and pickup current (I pick It represents the ratio between ). That is, M = I rms / Ipick It can be represented as.

[0010] t 12 and t 11 represents the operating time of the primary protection relay and the backup protection relay, respectively, when there are no fault current sources such as distributed power sources and SFCLs. In this case, the adjustment time interval (t) between the two overcurrent relays 11 - t 12 ) becomes Δt.

[0011] However, in the presence of fault current sources such as distributed power sources and SFCLs, the current magnitudes in the primary and backup protection relays fluctuate, causing the operating times of the two overcurrent relays to shift in the direction of the arrows on their respective characteristic curves. That is, the operating time of the primary protection relay is t 22 It becomes, and the operating time of the backup protection relay is t 21 This becomes. At this time, the adjustment time interval (t) between the two overcurrent relays 21 - t 22 ) becomes Δt'. Here, Δt' becomes a value greater than Δt, so the adjustment time interval increases. Prior art literature

[0013] Korean Registered Patent Publication No. 10-1382478 (April 8, 2014) The problem to be solved

[0014] An embodiment of the present invention is intended to provide a control method for a potential protection overcurrent relay that can maintain a constant adjustment time interval between a potential protection relay and a backup protection relay even when a fault current source is placed in a power distribution system, a computing device for performing the same, and a power distribution system equipped with the same. means of solving the problem

[0016] A method for controlling an overcurrent relay according to one disclosed embodiment is a method performed in a computing device having one or more processors and a memory storing one or more programs executed by said one or more processors, and comprises the steps of: measuring a current flowing in a potential protection relay and a current flowing in a backup protection relay in a power distribution system, respectively; calculating an operating time of the backup protection relay based on a current flowing in the backup protection relay and a pickup current set in the backup protection relay; calculating a pickup current of the potential protection relay based on the operating time of the backup protection relay and a current flowing in the potential protection relay; and calculating an operating time of the potential protection relay based on a pickup current of the potential protection relay and a current flowing in the potential protection relay.

[0017] The operating time (t1) of the above backup protection relay can be calculated by the following mathematical formula.

[0018] (Mathematical formula)

[0019]

[0020] : Curve coefficients according to the characteristic curve of the backup protection relay

[0021] : Time delay coefficient of the backup protection relay

[0022] The step of calculating the pickup current of the above-mentioned potential protection relay calculates the pickup current of the above-mentioned potential protection relay using a preset adjustment time interval together with the operating time of the above-mentioned backup protection relay and the current flowing through the above-mentioned potential protection relay, and the adjustment time interval may be the difference in operating time between the above-mentioned potential protection relay and the above-mentioned backup protection relay when there is no fault current influence source in the distribution system.

[0023] The pickup current of the above-mentioned potential protection relay can be adaptively varied according to the current flowing through the above-mentioned potential protection relay so that the adjustment time interval between the above-mentioned potential protection relay and the above-mentioned backup protection relay becomes constant, even if there is a fault current influence source in the distribution system.

[0024] The pickup current of the above-mentioned potential protection relay can be calculated by the following mathematical formula.

[0025] (Mathematical formula)

[0026]

[0027] : Curve coefficients according to the characteristic curve of the potential protection relay

[0028] : Time delay coefficient of the potential protection relay

[0029] The operating time (t2) of the above potential protection relay can be calculated by the following mathematical formula.

[0030] (Mathematical formula)

[0031]

[0032] A computing device according to one disclosed embodiment comprises one or more processors; a memory; and one or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors, and the one or more programs include: a command for measuring a current flowing through a potential protection relay and a current flowing through a backup protection relay in a power distribution system, respectively; a command for calculating the operating time of the backup protection relay based on the current flowing through the backup protection relay and a pickup current set in the backup protection relay; a command for calculating the pickup current of the potential protection relay based on the operating time of the backup protection relay and the current flowing through the potential protection relay; and a command for calculating the operating time of the potential protection relay based on the pickup current of the potential protection relay and the current flowing through the potential protection relay.

[0033] The command for calculating the pickup current of the above-mentioned potential protection relay calculates the pickup current of the above-mentioned potential protection relay using a preset adjustment time interval together with the operating time of the above-mentioned backup protection relay and the current flowing through the above-mentioned potential protection relay, and the adjustment time interval may be the difference in operating time between the above-mentioned potential protection relay and the above-mentioned backup protection relay when there is no fault current influence source in the distribution system.

[0034] The pickup current of the above-mentioned potential protection relay can be adaptively varied according to the current flowing through the above-mentioned potential protection relay so that the adjustment time interval between the above-mentioned potential protection relay and the above-mentioned backup protection relay becomes constant, even if there is a fault current influence source in the distribution system.

[0035] A power distribution system according to one disclosed embodiment comprises: a main power source; one or more power lines connected to the main power source; and a power distribution system including a potential protection relay and a backup protection relay connected to the power lines and installed spaced apart from each other, wherein the power distribution system further comprises: one or more fault current influence sources connected to the power lines; and a control device that measures the current flowing through the potential protection relay and the current flowing through the backup protection relay, respectively, calculates the operating time of the backup protection relay based on the current flowing through the backup protection relay and the pickup current set in the backup protection relay, calculates the pickup current of the potential protection relay based on the operating time of the backup protection relay and the current flowing through the potential protection relay, and calculates the operating time of the potential protection relay based on the pickup current of the potential protection relay and the current flowing through the potential protection relay. Effects of the invention

[0037] According to the disclosed embodiment, even when equipment that affects fault current, such as distributed power sources or SFCLs, is placed in the power distribution system, the pickup current of the potential protection relay can be adaptively varied to maintain a constant adjustment time interval between the potential protection relay and the backup protection relay. Brief explanation of the drawing

[0039] Figure 1 is a diagram illustrating a state in which an overcurrent relay (OCR) malfunctions due to a conventional distributed power source (DER). Figure 2 is a diagram showing the state in which the adjustment time interval between two overcurrent relays changes due to the additional placement of distributed power sources and SFCLs. FIG. 3 is a block diagram illustrating a computing environment including a computing device suitable for use in exemplary embodiments. FIG. 4 is a flowchart illustrating a control method for a potential protection overcurrent relay according to an embodiment of the present invention. FIG. 5 is a diagram showing a power distribution system in which a fault current influence source, such as a distributed power source (DER) and a superconducting fault current limiter (SFCL), is arranged in one embodiment of the present invention. FIG. 6 shows that in one embodiment of the present invention, the operating time (t2) of the potential protection relay (OCR2) is the pickup current (I pick2 This is a graph showing that the adjustment time interval between the primary protection relay (OCR2) and the backup protection relay (OCR1) is maintained at a constant level by adaptively varying according to ). Specific details for implementing the invention

[0040] Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. The following detailed description is provided to facilitate a comprehensive understanding of the methods, apparatuses, and / or systems described herein. However, this is merely illustrative and the present invention is not limited thereto.

[0041] In describing the embodiments of the present invention, detailed descriptions of known technologies related to the present invention are omitted if it is determined that such detailed descriptions may unnecessarily obscure the essence of the present invention. Furthermore, the terms described below are defined in consideration of their functions within the present invention, and these may vary depending on the intentions or practices of the user or operator. Therefore, such definitions should be based on the content throughout this specification. Terms used in the detailed description are intended merely to describe the embodiments of the present invention and should not be limiting in any way. Unless explicitly stated otherwise, expressions in the singular form include the meaning of the plural form. In this description, expressions such as "include" or "comprise" are intended to refer to certain characteristics, numbers, steps, actions, elements, parts thereof, or combinations thereof, and should not be interpreted to exclude the existence or possibility of one or more other characteristics, numbers, steps, actions, elements, parts thereof, or combinations thereof other than those described.

[0042] Additionally, terms such as "first," "second," etc., may be used to describe various components, but said components should not be limited by said terms. These terms may be used for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be named the second component, and similarly, the second component may be named the first component.

[0044] FIG. 3 is a block diagram illustrating a computing environment (10) including a computing device suitable for use in exemplary embodiments. In the illustrated embodiments, each component may have different functions and capabilities in addition to those described below, and may include additional components in addition to those described below.

[0045] The illustrated computing environment (10) includes a computing device (12). In one embodiment, the computing device (12) may be a computing device that adaptively changes the pickup current of a potential protection relay to maintain a constant adjustment time interval between two overcurrent relays when a fault current influence source that affects the magnitude of the fault current, such as a distributed power source (DER) or a superconducting fault current limiter (SFCL), is placed in the power distribution system.

[0046] The computing device (12) includes at least one processor (14), a computer-readable storage medium (16), and a communication bus (18). The processor (14) can cause the computing device (12) to operate according to the exemplary embodiment described above. For example, the processor (14) can execute one or more programs stored in the computer-readable storage medium (16). The one or more programs may include one or more computer-executable instructions, and the computer-executable instructions may be configured to cause the computing device (12) to perform operations according to the exemplary embodiment when executed by the processor (14).

[0047] A computer-readable storage medium (16) is configured to store computer-executable instructions or program code, program data and / or other suitable forms of information. A program (20) stored in the computer-readable storage medium (16) includes a set of instructions executable by a processor (14). In one embodiment, the computer-readable storage medium (16) may be memory (volatile memory such as random access memory, non-volatile memory, or a suitable combination thereof), one or more magnetic disk storage devices, optical disk storage devices, flash memory devices, or other forms of storage media that are accessed by a computing device (12) and capable of storing desired information, or a suitable combination thereof.

[0048] The communication bus (18) interconnects various other components of the computing device (12), including the processor (14) and the computer-readable storage medium (16).

[0049] The computing device (12) may also include one or more input / output interfaces (22) and one or more network communication interfaces (26) that provide interfaces for one or more input / output devices (24). The input / output interfaces (22) and network communication interfaces (26) are connected to a communication bus (18). The input / output devices (24) may be connected to other components of the computing device (12) through the input / output interfaces (22). An exemplary input / output device (24) may include an input device such as a pointing device (such as a mouse or trackpad), a keyboard, a touch input device (such as a touchpad or touchscreen), a voice or sound input device, various types of sensor devices and / or imaging devices, and / or an output device such as a display device, a printer, a speaker and / or a network card. An exemplary input / output device (24) may be included inside the computing device (12) as a component constituting the computing device (12), or it may be connected to the computing device (12) as a separate device distinct from the computing device (12).

[0051] FIG. 4 is a flowchart illustrating a control method for a potential protection overcurrent relay according to an embodiment of the present invention, and FIG. 5 is a diagram illustrating a power distribution system in which a fault current influence source, such as a distributed power source (DER) and a superconducting fault current limiter (SFCL), is arranged in an embodiment of the present invention. Although the method is described in the illustrated flowchart in a plurality of steps, at least some of the steps may be performed in a different order, combined with other steps, omitted, divided into detailed steps, or performed with one or more steps not illustrated added.

[0052] Referring to FIGS. 4 and 5, the computing device (12) has a current (I) flowing through the potential protection relay (OCR2). rms2 ) and current (I) flowing through the backup protection relay (OCR1) rms1Each can be measured (S 101). The primary protection relay (OCR2) and the backup protection relay (OCR1) can be determined according to the location of the fault in the power distribution system. In Fig. 5, OCR2, which is close to the location of the fault, operates as the primary protection relay (main protection relay), and OCR1 operates as the backup protection relay (backup protection relay).

[0053] Next, the computing device (12) has a current (I) flowing through the backup protection relay (OCR1). rms1 ) and the pickup current (I) set in the backup protection relay (OCR1) pick1 Based on ), the operating time (t1) of the backup protection relay (OCR1) can be calculated (S 103).

[0054] Here, pickup current (I pick1 ) may refer to the current for operating the backup protection relay (OCR1). Pickup current (I pick1 ) may be a preset current value. The computing device (12) can calculate the operating time (t1) of the backup protection relay (OCR1) through the following mathematical formula 1.

[0055] (Mathematical Formula 1)

[0056]

[0057] : Curve coefficients according to the characteristic curve of the backup protection relay (OCR1)

[0058] : Time delay coefficient of backup protection relay (OCR1)

[0059] Here, These are different constant values ​​that are pre-set according to the characteristic curve of the backup protection relay (OCR1), and is the time delay coefficient value set in the backup protection relay (OCR1).

[0060] Next, the computing device (12) [describes] the operating time (t1) of the backup protection relay (OCR1) and the current (I) flowing through the potential protection relay (OCR2). rms2 Based on ), and a preset adjustment time interval (Δt), the pickup current (I) of the potential protection relay (OCR2) pick2 ) can be calculated (S 105).

[0061] Here, the preset adjustment time interval (Δt) may represent the difference in operating time between the primary protection relay and the backup protection relay when there is no fault current source in the power distribution system. The computing device (12) uses the following mathematical formula 2 to determine the pickup current (I) of the primary protection relay (OCR2). pick2 ) can be produced.

[0062] (Mathematical Formula 2)

[0063]

[0064] : Curve coefficients according to the characteristic curve of the potential protection relay (OCR2)

[0065] : Time delay coefficient of the potential protection relay (OCR2)

[0066] Here, These are different constant values ​​that are pre-set according to the characteristic curve of the potential protection relay (OCR2), and is the time delay coefficient value set in the potential protection relay (OCR2).

[0067] According to Equation 2, the pickup current (I) of the potential protection relay (OCR2) pick2 ) is not a fixed current value, but the operating time (t1) of the backup protection relay (OCR1) and the current (I) flowing through the potential protection relay (OCR2). rms2 It can be seen that the value varies adaptively by ).

[0068] Next, the computing device (12) picks up the pickup current (I) of the potential protection relay (OCR2). pick2) and current (I) flowing through the potential protection relay (OCR2) rms2 Based on ), the operating time (t2) of the potential protection relay (OCR2) can be calculated (S 107).

[0069] The computing device (12) can calculate the operating time (t2) of the potential protection relay (OCR2) by the following mathematical formula 3.

[0070] (Mathematical Formula 3)

[0071]

[0072] As seen above, the pickup current (I) of the potential protection relay (OCR2) pick2 As ) adaptively varies, the operating time (t2) of the potential protection relay (OCR2) also picks up the pickup current (I pick2 It adaptively changes according to ), and as a result, the adjustment time interval between the primary protection relay (OCR2) and the backup protection relay (OCR1) can be maintained at a constant level.

[0073] FIG. 6 shows that in one embodiment of the present invention, the operating time (t2) of the potential protection relay (OCR2) is the pickup current (I pick2 This is a graph showing that the adjustment time interval between the primary protection relay (OCR2) and the backup protection relay (OCR1) is maintained constant by adaptively varying according to ). Here, OCR2 represents the time-current characteristic curve of the primary protection relay, and OCR1 represents the time-current characteristic curve of the backup protection relay.

[0074] Referring to Fig. 6, when there are fault current sources such as distributed power sources and SFCLs in the power distribution system, the adjustment time interval (t) between two overcurrent relays 21 - t 22 ) becomes Δt', and Δt' becomes a value greater than Δt, so the adjustment time interval increases.

[0075] However, in the disclosed embodiment, the pickup current (I) of the potential protection relay (OCR2) as in Equation 2 pick2 ) varies adaptively, and as a result, M, the ratio between the measurement current and the pickup current, 22 = I rms2 / I pick2 Ga M 22 It becomes variable. That is, M in the characteristic curve of OCR2 in Fig. 6 22 a pickup current (I pick2 M follows the curve according to the fluctuation of ) 22 It moves to '. Accordingly, looking at the graph in Fig. 6, the operating time (t2) of the potential protection relay (OCR2) is also t 22 from t 22 It will vary to '. In this case, the adjustment time interval between the two overcurrent relays is (t 21 - t 22 It becomes ') and is equal to the pre-set adjustment time interval Δt.

[0076] Here, the pickup current (I) of the potential protection relay (OCR2) pick2 According to mathematical formula 2, ) adaptively changes according to the preset adjustment time interval Δt, and as a result, the adjustment time interval between the primary protection relay (OCR2) and the backup protection relay (OCR1) can be maintained at a constant Δt.

[0078] Although representative embodiments of the present invention have been described in detail above, those skilled in the art will understand that various modifications can be made to the above-described embodiments without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined by the claims set forth below as well as equivalents thereof. Explanation of the symbols

[0080] 10: Computing Environment 12: Computing device 14 : Processor 16: Computer-readable storage media 18: Communication bus 20 : Program 22 : Input / Output Interface 24 : Input / Output Devices 26: Network communication interface

Claims

Claim 1 A method for controlling an overcurrent relay, performed in a computing device having one or more processors and a memory storing one or more programs executed by said one or more processors, comprising: measuring a current flowing in a potential protection relay and a current flowing in a backup protection relay in a power distribution system, respectively; calculating an operating time of the backup protection relay based on a current flowing in the backup protection relay and a pickup current set in the backup protection relay; calculating a pickup current of the potential protection relay based on the operating time of the backup protection relay and a current flowing in the potential protection relay; and calculating an operating time of the potential protection relay based on a pickup current of the potential protection relay and a current flowing in the potential protection relay. Claim 2 A method for controlling an overcurrent relay according to claim 1, wherein the operating time (t1) of the backup protection relay is calculated by the following mathematical formula. (Mathematical formula) : Curve coefficients according to the characteristic curve of the backup protection relay : Time delay coefficient of the backup protection relay Claim 3 A method for controlling an overcurrent relay according to claim 2, wherein the step of calculating the pickup current of the potential protection relay calculates the pickup current of the potential protection relay using a preset adjustment time interval together with the operating time of the backup protection relay and the current flowing through the potential protection relay, and the adjustment time interval is the difference in operating time between the potential protection relay and the backup protection relay when there is no fault current influence source in the power distribution system. Claim 4 A control method for an overcurrent relay according to claim 3, wherein the pickup current of the potential protection relay adaptively varies according to the current flowing through the potential protection relay so that the adjustment time interval between the potential protection relay and the backup protection relay becomes constant even though there is a fault current influence source in the power distribution system. Claim 5 A method for controlling an overcurrent relay according to claim 3, wherein the pickup current of the potential protection relay is calculated by the following mathematical formula. (Mathematical formula) : Curve coefficients according to the characteristic curve of the potential protection relay : Time delay coefficient of the potential protection relay Claim 6 A method for controlling an overcurrent relay according to claim 5, wherein the operating time (t2) of the potential protection relay is calculated by the following mathematical formula. (Mathematical formula) Claim 7 A computing device comprising one or more processors; memory; and one or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors, and wherein the one or more programs include: a command for measuring a current flowing in a potential protection relay and a current flowing in a backup protection relay within a power distribution system, respectively; a command for calculating the operating time of the backup protection relay based on the current flowing in the backup protection relay and a pickup current set in the backup protection relay; a command for calculating the pickup current of the potential protection relay based on the operating time of the backup protection relay and the current flowing in the potential protection relay; and a command for calculating the operating time of the potential protection relay based on the pickup current of the potential protection relay and the current flowing in the potential protection relay. Claim 8 A computing device according to claim 7, wherein a command for calculating the pickup current of the potential protection relay calculates the pickup current of the potential protection relay using a preset adjustment time interval together with the operating time of the backup protection relay and the current flowing through the potential protection relay, and the adjustment time interval is the difference in operating time between the potential protection relay and the backup protection relay when there is no fault current influence source in the power distribution system. Claim 9 A computing device according to claim 8, wherein the pickup current of the potential protection relay adaptively varies according to the current flowing through the potential protection relay so that the adjustment time interval between the potential protection relay and the backup protection relay becomes constant even though there is a fault current influence source in the power distribution system. Claim 10 A power distribution system comprising: a main power source; one or more power lines connected to the main power source; and a potential protection relay and a backup protection relay connected to the power lines and installed spaced apart from each other, wherein the power distribution system further comprises: one or more fault current influence sources connected to the power lines; and a control device that measures the current flowing through the potential protection relay and the current flowing through the backup protection relay, respectively, calculates the operating time of the backup protection relay based on the current flowing through the backup protection relay and the pickup current set in the backup protection relay, calculates the pickup current of the potential protection relay based on the operating time of the backup protection relay and the current flowing through the potential protection relay, and calculates the operating time of the potential protection relay based on the pickup current of the potential protection relay and the current flowing through the potential protection relay.

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