KR101722728B1 - Method for determining fault direction in ground fault of ground system power line and over current protection method - Google Patents

Abstract

Various embodiments of the present invention relate to a method for determining a fault direction and an overcurrent protection method. An objective of the present invention is to provide a method for determining a fault direction in a ground fault of a ground system power line and an overcurrent protection method. To achieve the objective, the method for determining a fault direction in a ground fault of a ground system power line comprises: a step of measuring a current for each phase; a step of using the current for each phase to detect a fault; a step of determining whether a type of a fault is a ground fault when the fault is detected; a step of determining whether a ratio of a reverse phase current to a zero phase current is larger than a predetermined setting value when the type of the fault is a ground fault; and a step of determining a magnetic section ground fault (forward direction) when the ratio of the reverse phase current to the zero phase current is larger than the predetermined setting value.

Description

TECHNICAL FIELD [0001] The present invention relates to a method of determining a fault direction and an overcurrent protection method in a ground fault of a power supply line of a grounding system,

Various embodiments of the present invention are directed to a failure determination method and an overcurrent protection method when a ground fault occurs in a ground system power supply line.

When a failure occurs in the power distribution system, if the power source is only the power source at the substation, the fault current is supplied from the substation to the high-strength one-way. Therefore, in such a case, the protection of the power distribution system can basically adopt an overcurrent relay system that does not consider the directionality.

However, when a distributed power source is connected to the power distribution system, the distributed power source is added to the fault current source from the power distribution system to the high power source in addition to the substation. Therefore, the distribution of the fault current also distributes in both directions, causing various problems in the existing overcurrent protection system.

In general, about 90% of accidents occurring in the distribution system are ground fault accidents. For this reason, the most frequent accident occurring in a distribution system connected with a distributed power source is a case where a protection relay malfunctions when a ground fault occurs in a healthy line connected to a distributed power source other than an accident line.

Most of the transformer for distributed power supply uses Grounded Y-Delta connection method to satisfy the effective grounding criterion. Therefore, if the distributed power supply transformer is connected to the grid regardless of whether or not the ground fault occurs, the primary ground of the transformer provides the path of the ground fault current.

Especially, if the grounded system is connected to the distributed power supply line transformer, the protection relay on the healthy line may malfunction due to the circulating current of the distributed power supply line transformer when a ground fault occurs.

In addition, the conventional general directional relays perform the direction determination only when the minimum polarity voltage is greater than the reference value for direction determination, and do not perform direction determination when the minimum polarity voltage is less than the reference value.

In this case, due to a high-resistance accident or a remote accident, the video voltage required for the direction determination is insufficient, so that it can not perform direction determination and can be operated.

Therefore, it is very important to determine the direction when a fault occurs in order to avoid such an erroneous operation and to protect only its own section accurately.

The above-described information disclosed in the background of the present invention is only for improving the understanding of the background of the present invention, and thus may include information not constituting the prior art.

The present invention also provides a method of determining a fault direction and a method of overcurrent protection when a ground fault occurs in a ground line power line. For example, a problem to be solved in accordance with various embodiments of the present invention is to provide a method of controlling a ground fault in a ground system, wherein a ground fault occurs when a ground fault occurs, regardless of the reverse current state or the minimum polarity voltage (image voltage) The present invention provides a method of determining a fault direction and a method of overcurrent protection when a ground fault of a power supply line of a ground system is judged to be a fault of the self-section (normal direction) when the ratio of the image current and the reverse-

A method of determining a fault direction and a method of overcurrent protection in the occurrence of a ground fault in a ground system power line according to various embodiments of the present invention includes measuring a current for each phase; Detecting a fault using a current for each phase; Determining whether the type of fault is a ground fault in case of a fault; Determining whether a ratio of a reverse current to a video current is greater than a predetermined set value in the case of a ground fault; And determining that the self-interval ground fault is in a forward direction if the ratio of the reverse-phase current to the image current is greater than a predetermined set value.

If the ratio of the reverse-phase current to the video current is smaller than the predetermined value, it may be determined that there is a ground fault (reverse direction) in the other section.

If the operating condition of the healthy line is in the equilibrium state (I ₂ = 0), the ratio of the reverse current to the image current can be judged by the magnitude of I ₂ / I ₀ .

If the operating condition of the healthy line is unbalanced (I ₂ = α), the ratio of the reverse current to the image current can be determined as Δ I ₂ / Δ I ₀ to determine whether or not there is a ground fault. _{Here, △ I 2 = I 2 after_fault} - I _{2 pre_fault} , I ₀ = I _{0 after_fault} - I _{0 pre_fault} .

In the step of detecting a fault using the current for each phase, if the current for each phase is larger than a predetermined set value, it can be judged as a failure.

The step of determining whether the type of fault is a ground fault is judged as a ground fault if the neutral current, which is the sum of the currents by phase, is larger than a predetermined set value.

In accordance with various embodiments of the present invention, there is provided an overcurrent protection method for a ground fault in a ground system power line, the method comprising the steps of: Detecting a fault using a current for each phase; Determining whether the type of fault is a ground fault in case of a fault; Determining whether a ratio of a reverse current to a video current is greater than a predetermined set value in the case of a ground fault; If the ratio of the reverse current to the video current is larger than the predetermined set value, determining that the ground fault is a self-interval ground fault (forward); And operating the overcurrent relay.

Operating the overcurrent relay may include activating a ground overcurrent relay (OCGR) and tripping the protection device.

If the ratio of the reverse current to the video current is smaller than the predetermined value, it is determined that there is a ground fault (reverse direction) in the other section, and the overcurrent relay may not be operated.

Various embodiments of the present invention provide a method of determining a fault direction and an overcurrent protection method when a ground fault occurs in a ground system power supply line.

For example, the various embodiments of the present invention provide a method of controlling a video current and a reverse-phase current, regardless of the magnitude of a reverse polarity voltage or a minimum polarity voltage (image voltage) caused by a distributed power source- The fault ratio is analyzed to provide a method of determining a fault direction when a ground fault occurs in a power line of a grounding system which is judged to be a fault of the self-section (forward direction).

In addition, various embodiments of the present invention provide an overcurrent protection method for operating a ground fault overcurrent relay (OCGR) and tripping a protective device when a ground fault is judged to be a ground fault fault (forward direction) in the ground system. Of course, if the ground fault is judged to be a fault in the other section (reverse direction), the ground fault overcurrent relay is not operated and the protection device is not tripped.

FIG. 1 is a diagram showing a magnetic section (protection section) for each position of a protective relay in a radial system.
FIG. 2 is a diagram showing a possible operation of a protection relay malfunction in a distributed power line-connected transformer-connected line.
FIG. 3 is a diagram illustrating a possible operation of the protection relay unit due to a shortage of the video voltage required for direction determination.
4 is a diagram showing a reverse phase and a video current relationship when a ground fault occurs in a distributed power supply line connected to a transformer.
FIG. 5A is a flowchart illustrating a fault direction determination method and an overcurrent protection method when a ground fault occurs in a ground system power line according to an exemplary embodiment of the present invention. FIG. 5B is a flowchart illustrating a method of determining a fault direction in a ground system power line according to an exemplary embodiment of the present invention. FIG. 7 is a block diagram showing a configuration of a fault direction determination apparatus when a ground fault occurs; FIG.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The embodiments of the present invention are described in order to more fully explain the present invention to those skilled in the art, and the following embodiments may be modified into various other forms, The present invention is not limited to the embodiment. Rather, these embodiments are provided so that this disclosure will be more faithful and complete, and will fully convey the scope of the invention to those skilled in the art.

In the following drawings, thickness and size of each layer are exaggerated for convenience and clarity of description, and the same reference numerals denote the same elements in the drawings. As used herein, the term "and / or" includes any and all combinations of one or more of the listed items. In the present specification, the term " connected "means not only the case where the A member and the B member are directly connected but also the case where the C member is interposed between the A member and the B member and the A member and the B member are indirectly connected do.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a," "an," and "the" include singular forms unless the context clearly dictates otherwise. Also, " comprise, " and / or "comprising, " when used in this specification, are intended to be interchangeable with the said forms, numbers, steps, operations, elements, elements and / And does not preclude the presence or addition of one or more other features, integers, operations, elements, elements, and / or groups.

Although the terms first, second, etc. are used herein to describe various elements, components, regions, layers and / or portions, these members, components, regions, layers and / It is obvious that no. These terms are only used to distinguish one member, component, region, layer or section from another region, layer or section. Thus, a first member, component, region, layer or section described below may refer to a second member, component, region, layer or section without departing from the teachings of the present invention.

It is to be understood that the terms related to space such as "beneath," "below," "lower," "above, But may be utilized for an easy understanding of other elements or features. Terms related to such a space are for easy understanding of the present invention depending on various process states or use conditions of the present invention, and are not intended to limit the present invention. For example, if an element or feature of the drawing is inverted, the element or feature described as "lower" or "below" will be "upper" or "above." Thus, "lower" is a concept encompassing "upper" or "lower ".

In addition, the controller (controller) and / or other associated equipment or components in accordance with the present invention may be implemented using any suitable hardware, firmware (e.g., custom semiconductor), software, or any appropriate combination of software, . For example, the various components of a controller (controller) and / or other associated equipment or components in accordance with the present invention may be formed on one integrated circuit chip or on a separate integrated circuit chip. In addition, the various components of the controller (controller) may be implemented on a flexible printed circuit film and formed on the same substrate as the tape carrier package, printed circuit board, or controller (controller). In addition, the various components of the controller (controller) may be a process or thread executing on one or more processors in one or more computing devices, which executes computer program instructions to perform various functions, And interact with other components. The computer program instructions are stored in a memory that can be executed on a computing device using standard memory devices, such as, for example, random access memory. The computer program instructions may also be stored in other non-transitory computer readable media, such as, for example, CD-ROMs, flash drives, and the like. Further, those skilled in the art will appreciate that the functions of the various computing devices may be combined with one another, integrated into one computing device, or the functionality of a particular computing device may be implemented within one or more other computing devices Lt; / RTI > can be dispersed in the < / RTI >

For example, the controller according to the present invention may be implemented as a central processing unit, a mass storage device such as a hard disk or solid state disk, a volatile memory device, an input device such as a keyboard or a mouse, an output device such as a monitor or a printer, Of commercial computers.

FIG. 1 is a diagram showing a magnetic section (protection section) for each position of a protective relay in a radial system.

As shown in Fig. 1, when the protective relay in the radial system between the ground system power supply and the distributed power supply is located, for example, in each of R1, R2 and R3, the self- All. If a fault occurs at F1, the protection relay of R1 operates because it is its own interval, but the protection relay of R2 should not operate because it is not its own interval.

FIG. 2 is a diagram showing a possible operation of a protection relay malfunction in a distributed power line-connected transformer-connected line.

As shown in FIG. 2, if a ground fault occurs at the point F2, the protective relay of R3 will operate normally because it is a fault of its own section. However, the protection relays of R1 and R2 are connected to the ground of the distributed power- It may malfunction even though it is not a failure in its own section.

FIG. 3 is a diagram illustrating a possible operation of the protection relay unit due to a shortage of the video voltage required for direction determination.

As shown in FIG. 3, if a ground fault is detected at a point F2, the image voltage (minimum polarity voltage) measured at each interval is not determined at a point R3 that is less than the set value, have.

4 is a diagram showing a reverse phase and a video current relationship when a ground fault occurs in a distributed power supply line connected to a transformer.

As shown in FIG. 4, if a ground fault occurs at the point F1, the forward fault current has a relation of I ₂ > I ₀ and the reverse fault current has a relation of I ₂ < I ₀ .

As in Figures 2 and 3, directional relays in general have the potential for misoperation. FIGS. 2, 3 and 4, including these cases, show the general relationship between the reverse phase current and the video phase current measured by the protection relay in the event of a ground fault. As shown in Figs. 2, 3 and 4, the relation of I ₂ &gt; I ₀ in the case of forward fault current and I ₂ < I ₀ in the case of reverse fault current are shown.

That is, in general, the reverse-phase current has a relatively large or similar value relative to the image current for the self-interval ground fault (R3 in Fig. 2, R3 in Fig. 3, R1 in Fig. 4) The current is smaller than the image current (R1, R2 in Fig. 2, R2 in Fig. 4).

Therefore, it can be seen that the self-interval judgment can be divided by the ratio of the image minute current and the reverse phase current when a ground fault occurs. This reason is considered to be due to the failure characteristics of Grounded Y- △ connection which is most widely used as a transformer connection method for distributed power supply connection. In other words, when Grounded Y- △ connection is used, regardless of the type of distributed power source or the power generation status of the distributed power source when a fault occurs, This is because the image current is formed larger than the reverse current.

The fact that the image current is largely formed means that the current vectors of each phase converge in one direction within a certain phase difference. Therefore, it can be seen that the fault direction can be discriminated by using these characteristics.

The fault direction determination method and the overcurrent protection method in the occurrence of the ground fault in the power line of the grounding system will be described in more detail.

FIG. 5A is a flowchart illustrating a fault direction determination method and an overcurrent protection method when a ground fault occurs in a ground system power line according to an exemplary embodiment of the present invention. FIG. 5B is a flowchart illustrating a method of determining a fault direction in a ground system power line according to an exemplary embodiment of the present invention. FIG. 7 is a block diagram showing a configuration of a fault direction determination apparatus when a ground fault occurs; FIG.

As shown in FIG. 5A, in the method of determining the fault direction when a ground fault occurs in the ground system power supply line, first, the current for each phase is measured (S1), and whether or not the input current is higher than a preset value (S2).

If a fault is detected, it is determined whether the type of the fault is a ground fault by measuring the current for each phase (S3). If the neutral line current (In) which is the sum of the three-phase input currents (Ia + Ib + Ic) is higher than the predetermined set value, it is judged as a ground fault. On the other hand, if the neutral current (In) is smaller than the predetermined set value, it can be regarded as an injury (short circuit failure). Here, the description is omitted since it is not a main content of the present invention.

As described above, in the case of a ground fault, the fault current supplied from the distributed power supply is not smaller than the fault current supplied from the ground system power supply. In some cases, the fault current supplied by the distributed power supply may be greater than the fault current at the grid power supply. Also, since the minimum operating current of Over Current Ground Relay (OCGR) is usually set low for high resistance ground fault detection, it is difficult to solve with conventional protection cooperative method.

Therefore, if the type of fault is determined as a ground fault, the fault direction is first determined (S4). For example, although not limiting, it is determined whether the ratio of the reverse-phase current I ₂ to the imaging current I ₀ is higher than a predetermined set value in the case of a ground fault.

Here, if the running state of the healthy line is in an equilibrium state (I ₂ = 0), it is possible to judge whether there is a self-induced ground fault by the magnitude of the inverse-phase current with respect to the video current to be I ₂ / I ₀ .

If the running state of the healthy line is in the unbalanced state (I ₂ =?), It is possible to determine whether the self-induced ground fault has occurred by the magnitude of the inverse-phase current with respect to the video current by Δ I ₂ / Δ I ₀ .

Here, _{ΔI 2} = I _{2 after_fault ( after ground fault )} - I _{2 pre_fault ( before ground fault )} , Δ I ₀ = I _{0 after_fault (after ground fault)} - I _{0 pre_fault ( before ground fault )} .

In this way, if the ratio of the reverse-phase current to the video current is higher than the predetermined set value k, it is determined that the ground fault is in the self-interval (forward direction) (S5).

If the ratio of the reverse current to the video current is smaller than the predetermined value, it is determined that the ground fault is in the reverse direction (S6).

As described above, the embodiment of the present invention makes it possible to accurately determine the failure direction when a ground fault occurs in the ground system power supply line. That is, in the embodiment of the present invention, when a ground fault occurs in the ground system, only the ratio of the image current and the reverse-phase current is analyzed regardless of the magnitude of the reverse polarity voltage or the minimum polar voltage (image voltage) If it is high, it can be judged accurately by fault of self-section (forward direction).

On the other hand, after the self-section ground fault (forward) determination step S5, a step of operating the overcurrent relay may be performed for overcurrent protection. Here, operating the overcurrent relay may be accomplished by operating a ground fault overcurrent relay (OCGR) and tripping the protection device. Of course, the protection relay described above is not operated after the step S6 for judging the ground fault fault in the other direction (reverse direction).

Thus, various embodiments of the present invention provide a method of determining a fault direction as well as an overcurrent protection method when a ground fault occurs in a ground system power supply line. That is, in various embodiments of the present invention, when a ground fault occurs in a ground system, a ratio of a video current to a reverse-phase current, regardless of the magnitude of a reverse polarity voltage or a minimum polarity voltage (image voltage) (Forward direction) when the ground fault is over the set value, and provides a method of determining the fault direction and an overcurrent protection method when a ground fault occurs in the power supply line of the ground system that performs the overcurrent protection operation.

The fault direction determination method and / or the overcurrent protection method as described above may be implemented through a control unit 200 interlocked with the protection device 100 such as a breaker, as shown in FIG. 5B.

The control unit 200 interlocks with the protection device 100 through the communication cable 300 and sends a trip signal to the protection device 100 or receives the current measurement information from the protection device 100. [

Specifically, the control unit 200 measures a current from a CT (Current Transformer) of the protection device 100, detects a failure by the above-described method, detects whether or not a ground fault has occurred, determines a failure direction, The overcurrent relay 250 operates the overcurrent relay 250 to send a trip signal to the protection device 100 to operate the protection device 100. When the failure direction is determined to be the reverse direction, (OCGR) is not operated.

The protection device control unit 200 includes a current measuring unit 210, a fault detecting unit 220, a ground fault detecting unit 230, a fault direction determining unit 240, an overcurrent relay 250 and a trip signal generating unit 200 .

The current measuring unit 210 measures the current for each phase by interlocking with the CT of the protecting device 100. Also, the measuring unit 210 calculates the neutral line current by adding the measured three-phase input currents.

The failure detection unit 220 detects the failure using the measured current. That is, if the measurement current is higher than a predetermined value set in advance, the failure detection unit 220 detects / determines a failure.

The ground fault detection unit 230 determines the type of the fault using the measured current. Specifically, the ground fault detection unit 230 determines whether the neutral line current In, which is the sum of the currents Ia + Ib + Ic, is lower than a predetermined set value, and determines whether the type of the fault is a ground fault .

The fault direction determination unit 240 determines the fault direction by the above-described method when the determined type of fault is a ground fault. That is, the failure direction determination unit 240 analyzes the ratio of the image current and the reverse-phase current. If the size of the image current is higher than the predetermined value, the failure direction determination unit 240 determines that the failure is in the self- Reverse direction).

The failure direction determination unit 240 instructs the overcurrent relay 250 (OCGR) to operate when the failure direction is the forward direction and instructs the overcurrent relay 250 (OCGR) to issue an operation instruction when the failure direction is the reverse direction It is instructed to repeat the process of measuring the current without sending it.

The overcurrent relay 250 receives an operation instruction from the fault direction determination unit 240 or the ground fault detection unit 230 and operates.

The overcurrent relay 250 may include a short-circuit overcurrent relay (general overcurrent relay, OCR) and a ground fault overcurrent relay (OCGR).

The trip signal generator 260 generates a trip signal based on the operation of the overcurrent relay 250 and transmits the trip signal to the protection device 100.

As described above, by providing the protective device to which the control unit 200 is linked in the ground system to which the distributed power source is connected, the protective device 100 can be operated only in the self-protection period (that is, So that unnecessary malfunctions can be prevented from occurring in the sections other than the self-protection section (that is, on the power source side and the other lines on the basis of the protection apparatus installation point).

The present invention is not limited to the above-described embodiment, but may be embodied in the following forms. The present invention is not limited to the above-described embodiments, It will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined in the appended claims.

100; Protective device 200; The control unit
210; A current measuring unit 220; The failure detection unit
230; A ground fault detection unit 240; [0040]
250; An overcurrent relay 260; The trip signal generator

Claims (10)

A method for determining a fault direction when a ground fault occurs in a ground line power line,
Measuring a current for each phase;
Detecting a fault using a current for each phase;
Determining whether the type of fault is a ground fault in case of a fault;
Determining whether a ratio of a reverse current to a video current is greater than a predetermined set value in the case of a ground fault; And
And determining that the ground fault is a ground fault (forward) if the ratio of the reverse current to the video current is greater than a predetermined set value. The method according to claim 1,
And determining that the ground fault is in the reverse direction if the ratio of the reverse current to the video current is smaller than the predetermined value. The method according to claim 1,
When the operating condition of the healthy line is in equilibrium (I ₂ = 0)
Wherein a ratio of a reverse current to a video current is determined to be I ₂ / I ₀ to determine whether or not a ground fault has occurred in the ground fault. The method according to claim 1,
If the operating condition of the healthy line is unbalanced (I ₂ = α)
Wherein a ratio of a reverse phase current to a video current is determined as ΔI ₂ / ΔI ₀ to determine whether or not a ground fault has occurred in the ground fault. 5. The method of claim 4,
I ₂ = I _{2 after_fault} - I _{2 pre_fault} ,
I ₀ = I _{0 after_fault} - I _{0 pre_fault} . The method according to _{claim 1} , wherein the ground fault is a ground fault. The method according to claim 1,
The step of detecting a fault using the current for each phase includes:
And judging that the fault is detected if the current for each phase is greater than a predetermined set value. The method according to claim 1,
The step of determining whether the type of fault is a ground fault is characterized by comprising:
Wherein the ground fault is judged to be a ground fault if the neutral line current, which is the sum of the currents for each phase, is larger than a preset set value.
In an overcurrent protection method in the event of a ground fault in a power line of a grounding system,
Measuring a current for each phase;
Detecting a fault using a current for each phase;
Determining whether the type of fault is a ground fault in case of a fault;
Determining whether a ratio of a reverse current to a video current is greater than a predetermined set value in the case of a ground fault;
If the ratio of the reverse current to the video current is larger than the predetermined set value, determining that the ground fault is a self-interval ground fault (forward); And
And operating the overcurrent relay when the ground fault occurs in the power line of the ground system. 9. The method of claim 8,
The step of operating the overcurrent relay comprises:
And operating the ground fault overcurrent relay (OCGR) and tripping the protective device. 9. The method of claim 8,
And determining that the reverse current is less than the predetermined value if the ratio of the reverse current to the video current is smaller than the predetermined value. The overcurrent relay is not operated. The overcurrent protection Way.

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