KR101562480B1 - Identification method of faulted section in distribution network - Google Patents

Abstract

The present invention relates to a method for judging a faulted section in a distribution system. The objective of the present invention is to judge the faulted section by acquiring a fault current from each automatic distribution switch in a main system and then comparing the fault current, while using the prior automatic distribution switch just so. For this, the method of the present invention includes: a step in which the main system acquires the fault current from a plurality of automatic distribution switches comprised in the distribution system; a step in which the main system classifies the acquired fault current into a grounding current and a phase current by the switches and then stores the grounding current and the phase current; a step in which the main system judges a short-circuit fault, by comparing the stored phase current with the stored grounding current; a step of calculating a phase current difference per each section in case it is judged to be the short-circuit fault; a step of judging the faulted section, by comparing the phase current difference calculated by each section; and a step of checking the faulted section, through an average of the phase current difference calculated by each section.

Description

{Identification method of faulted section in distribution network}

The present invention relates to a method of judging a fault in a power distribution system.

Generally, in the case of a power distribution system in which the current source is only the power source at the substation, the fault current is supplied in a unidirectional manner from the substation to the high-strength side in the event of a substation failure. For this reason, the protection of the distribution system has basically adopted the overcurrent relay method which does not consider the directionality. However, due to the connection of the distribution system of the distributed power supply, the source of the fault current in the distribution system is added to the distributed power supply in addition to the substation, and the distribution of the fault current is also distributed in both directions. .

1, when a ground fault occurs at a high advantage (F1) in a power supply system of a substation 10 and a power distribution system having a distributed power supply DG, not only at a faulted line but also at a distributed power supply side The reverse fault current (y1) is detected in the line connected to the DG and the fault can be detected. That is, when the reverse fault current y1 supplied by the distributed power source DG is detected by the first recloser RC1 and the magnitude of the fault current is equal to or greater than the fixed value (minimum operating current) of the recloser, The first recloser RC1 is tripped. As a result, the first recloser RC1 of the line without a fault unnecessarily operates, and a section below the first recloser RC1 experiences a power failure. At the same time, the first recloser RC1 trips, (RC1) or below may experience a problem that the distributed power source (DG) may fall out of the system because it experiences a single operation.

To solve this problem, it is necessary to add a directional protection device with a fault direction discrimination function to a distribution protection device such as a breaker (CB) and a recloser (RC) to solve the problem of a distribution system with a distributed power supply .

Then, the distribution automation system detects the fault of the line and displays the fault information (FI) (Fault Indication) on the HMI of the distribution automation system to inform the operator of the occurrence of the fault and the operator can remotely operate the switch The fault can be recovered. Such an automatic line fault detection device detects both line voltage and fault current, and displays fault indicator (FI) when there are two or more. In other words, an automatic switch detects a fault current when a line fault occurs, detects a no-voltage when there is a trip or reclosing operation of the line protection device, and outputs a fault indicator FI to a human machine interconnection device (HMI) .

As shown in FIG. 2, in the distribution automation system of the distribution line connected with the distributed power source, when the failure occurs at the high advantage F2, the first automatic switch GA1 is closed by the reverse fault current y2 of the distributed power source side DG, Detects a fault, and when the line first recloser (RC1) or the first substation breaker (CB1) is operated, it detects no voltage and displays the fault indicator (FI) information on the distribution automation system. If the first recloser RC1 or the first substation breaker CB1 includes a directional protection device, the first recloser RC1 does not operate when a fault occurs at the high advantage F2 and the first substation breaker CB1 The first automatic door switch GA1 generates the fault indicator FI. In a conventional distribution system without a distributed power supply, the distribution automation operator sees the fault indicator (FI) information of the automation switch and judges that a fault has occurred at the bottom of the automated switch marked with the fault indicator (FI) CB1 and the first recloser RC1, there is a high possibility that a failure occurs at the bottom of the first automatic switchgear GA1 or below. In this case, failures can not be accurately judged, and failure recovery and power outage time are likely to be prolonged. In order to solve this problem, not only the protection device but also the automatic switch may be provided with a directional function so that the problem of not generating the fault indicator FI when the reverse fault current is detected can be solved.

However, giving the directional function of the automatic switch has many problems in terms of technical and economic problems and field operation.

First, it is necessary to measure the accurate voltage and current magnitude and phase in order to determine the fault direction in case of a fault, not always due to technical problems. To do so, a high-precision transformer (PT) and a current transformer (CT) are required. Also, there is a need for hardware that has the capability to accurately calculate the phase angle. However, the transformer (PT) used in automation switches used in distribution systems is very inaccurate. Particularly, there is a problem that accuracy is drastically deteriorated over time due to deterioration or saturation characteristics of the transformer (PT) while maintaining high accuracy at the time of initial installation. Therefore, it is highly probable that the direction determination is performed by replacing only the terminal device with the device having the directional decision logic by using the installed switchgear, technically failing to determine the direction.

SUMMARY OF THE INVENTION It is an object of the present invention to overcome the above-described problems of the prior art, and it is an object of the present invention to provide a fault diagnosis system, And to provide a method for determining a fault section of a power distribution system.

According to another aspect of the present invention, there is provided a method for determining a fault in a power distribution system, comprising: obtaining a fault current from a plurality of automation switches provided in a power distribution system; Comparing the stored phase current with the ground fault current to determine whether the fault is a short-circuit fault; calculating a phase difference difference for each of the sections when the short-circuit fault is determined; Comparing the phase current difference calculated for each section with each other to determine a fault section, and checking a fault section through an average of phase current differences calculated for each section.

The phase current difference for each section may differ depending on the number of load-side automation switches.

If there is no load-side automation switch, the phase-by-phase current difference may be a phase current value of the power-side switch.

If the load-side automation switch is one, the phase-by-phase current difference may be a value obtained by subtracting the phase current value of the load-side switch from the phase current value of the power-side switch.

When there are two or more load-side automation switches, the value may be a value obtained by doubling the phase current value of the maximum power-source-side switch by subtracting the sum of the phase current values of the load-side switches.

The fault section may be a section having the largest phase current difference.

In the fault section checking step, when the phase current difference of the fault section differs by more than the reference value compared with the average value of the phase current difference, it can be confirmed as a fault section.

In the method of determining a power failure mode of the power distribution system according to the present invention, a fault current can be acquired from each automation switch in the main system while comparing the fault current to the fault current.

FIG. 1 is a current distribution diagram showing the occurrence of a fault in a power line of a distributed power source in a power distribution system having a distributed power source.
2 is a current distribution diagram showing the occurrence of a fault in a distributed power line in a power distribution system having a distributed power source.
FIGS. 3A and 3B are a schematic view and a detailed view of a flowchart showing a method of determining a failure period of a power distribution system according to an embodiment of the present invention.
4 is a current distribution diagram showing an example of a fault current flow in the power distribution system of the present invention.

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 in 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.

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 herein should be interpreted as specifying the presence of stated shapes, 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.

Referring to FIGS. 3A and 3B, there is shown a flowchart and a detailed view of a flowchart showing a method of determining a power system failure section according to the present invention. Referring to FIG. 4, there is shown an example of current flow in a power distribution system having a distributed power source for explaining a method of determining a power system failure section in FIGS. 3A and 3B. Hereinafter, the method of determining the failure period of the power distribution system of FIGS. 3A and 3B will be described with reference to the current flow of the failure of the power distribution system of FIG.

The power distribution system having the distributed power source includes a first automatic switch GA1, a second automatic switch GA2, and a third automatic switch < RTI ID = 0.0 > A fourth interval S4 between the fourth and fifth automated shutoff units GA4 and GA5 and a fourth power source unit GA4 including a fourth automatic shutoff unit GA3, a fourth automatic shutoff unit GA4 and a fifth automatic shutoff unit GA5, And a sixth automatic switch (GA6) interposed between the first and second switches (20, 20). In FIG. 4, the number of automatic power switches included in the power distribution system is shown as six, and the number of distributed power sources is shown as one. However, this is schematically shown for explaining a method of determining a fault section. In the present invention, The present invention is not limited thereto.

The power distribution system including the distributed power source has a first section S1 between the first automatic switchgear GA1 and the second automatic switchgear GA2 and a second section between the second automatic switchgear GA2 and the third automatic switchgear GA3 The third interval S3 between the third automatic switchgear GA3 and the fourth automatic switchgear GA4 and the fourth interval between the fourth automatic switchgear GA4 and the fifth automatic switch GA5. (S4). ≪ / RTI > At this time, one end of the sixth automatic switch GA6 is connected to the fourth section S4 and the other end is connected to the distributed power source 20.

In a power distribution system having a distributed power source, if there is a high advantage (F3) as a failure occurrence point in the second section S2, the substation side current x and the distributed power source side current y which are fault currents flow. That is, since the impedance at the high advantage F3 is reduced, the current flows from the side of the substation 10 and the side of the distributed power source 20 to the high advantage F3. At this time, there is almost no current difference between the power source side and the load side in the non-fault section, but in the second section S2, which is the fault section, between the current values measured by the second automatic switch GA2 and the third automatic switch GA3 There is a difference. That is, since the current difference between the second automatic switch (GA2) on the power source side and the third automatic switch (GA3) on the load side has a larger current difference than the other intervals, the current difference between the power source side and the load side The fault zone can be determined.

In the power distribution system failure section determination method of the present invention, first, the main system 30 acquires a fault current from a plurality of automated switches provided in the power distribution system (S1). When the pick-up current of a conventional automation switch is set to a minimum value, the fault current is supplied to the main system 30, which is a current value measured by a no-voltage condition, .

The main system 30 classifies and stores a fault current for each switch (S2). In order to classify the fault current, the main system 30 sets each section of the power distribution system and classifies the power-side switch and the load-side switch according to the set intervals. For each switch, fault current is divided into phase current and ground fault current.

The fault current of each section stored in the main system 30 can be stored as shown in Equation (1).

Here, Si denotes switch information (ID) of the power source side switch (Up) corresponding to the i period and the kth load side switch (Down) of the i period. Ini denotes a source-side ground fault current (InUpi) and a load-side ground fault current (InDowni, k) corresponding to the i-th period. Ipi denotes the power source side phase current IpUpi and the load side phase current IpDowni, k corresponding to the i period. Here, the phase current can store the largest value among the three phase currents as representative phase currents.

That is, the main system 30 can classify and store the information on the power source side and the load side switchgears in each section and the phase current and ground fault current for each switchgear.

Also, the main system 30 compares the phase current and the ground fault current for each switch and determines whether the fault is a short circuit fault (S3). The main system 30 judges that a short circuit failure occurs when all of the acquired ground fault currents are equal to or less than the set value e1 and judges that the ground fault is present if any one of the ground fault currents is equal to or greater than the set value e1. Here, the set value (e1) can be set to the pick-up current level of the ground fault overcurrent relay (OCGR).

If it is determined that the main system 30 has a short circuit failure, the main system 30 calculates the phase difference difference for each section (S4). The calculation method of the phase current difference may be different depending on the number of load side breakers for each section. Also, in the case of distribution lines, there is only one power source switch, so the number of separate power switch is not confirmed. First, the main system 30 confirms whether there is a load side switch (S41). If it is determined in step S41 that there is no load-side switch, the phase current difference is calculated through Equation 2 (S42).

Here, Ipdi is the difference between the phase current flowing in i and the phase current flowing out, and ipUpi is the phase current on the power supply side in phase i.

If it is determined that there is a load side switch, it is checked whether or not the load side switch is two or more (S43). If it is determined in step S43 that there is not more than two load-side switches, it is determined that there is one load-side switch, and the phase current difference is calculated through Equation 3 (S44).

 Here, Ipdi is the phase difference between the i-phase input current and the output phase current, IpUpi is the i-phase power source phase current, and IpDowni, 1 is the first load phase current i.

If it is determined in step S43 that there are two or more load-side switches, the phase current difference is calculated through Equation (4) (S45).

Here, Ipdi denotes the difference between the phase current flowing in the i-th phase and the phase current flowing out, and the power side current (IpUpi) and the load side phase current (IpDowni, k).

When the difference between the phase currents on the power source side and the load side is calculated in this manner, the fault region can be determined (S5) through the calculated phase current difference. The main system 30 can determine the section having the largest difference between the phase current flowing in each section and the phase current flowing out as a fault section. In addition, the main system 30 can calculate an average value of the phase current differences of the remaining sections excluding the phase current difference of the section in which the maximum phase current has occurred. The difference between the input and output phase currents and the average value are shown in Equation (5). Then, the fault section can be confirmed (S6) through the difference between the calculated inflow and outflow currents and the average value.

Here, Ipdv means the largest difference value between the input phase current and the output phase current, and Ipdavg means the average value of the phase current difference. Here, the average value means an average of the remainder obtained by subtracting the maximum difference value. And v is the largest interval between the input phase current and the output phase current.

If the maximum difference value exceeds the reference value e2 in comparison with the average value in the failure interval checking step S6, the interval in which the maximum difference value is generated can be determined as the failure interval. Also, in order to remove the section in which the fault has been confirmed, the information of the automatic switch in the fault section can be outputted and the driving can be controlled (S10). If the difference between the average value and the reference value e2 is smaller than the reference value e2 in the fault section checking step S6, it is impossible to determine the fault section, so that it can be notified.

If it is determined in step S3 that the short-circuit fault has occurred, it is checked whether or not the ground fault has occurred (S7, S8, S9). Such a ground fault check step is similar to the short-circuit fault section check (S4, S5, S6). However, the current difference of the ground current can be used for the inflow and outflow current difference for each section, and if the ground current difference is not particularly large, the fault section can be further searched using the phase current difference. Since there is almost no ground fault current at the time of a short fault, it is meaningless to compare the difference of the ground fault current, so that it can be confirmed only by the difference of the input current and the output phase current.

As described above, the present invention is not limited to the above-described embodiments, but can be applied to a method of determining a failure period of a power distribution system according to the present invention. It will be understood by those skilled 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 by the appended claims.

10; Substation side DG, 20; Distributed power side
30; Main system GA; Automation Switch

Claims (7)

The main system obtaining a fault current from a plurality of automation switches provided in the power distribution system;
The main system classifying and storing the ground fault current and the phase current for each fault current obtained by the main switch;
Comparing the stored phase current and ground fault current in the main system to determine whether the fault is a short circuit fault;
Calculating a phase current difference for each section when it is determined that a short circuit fault has occurred;
Comparing the calculated phase current difference for each section to determine a fault section; And
And determining a fault section through an average of phase current differences calculated for each of the sections. The method according to claim 1,
The phase current difference for each section
Wherein the calculation method is different according to the number of load-side automation switches. The method of claim 2,
Wherein when the load side automation switch is not provided, the phase current difference according to the section is a phase current value of the power switch. The method of claim 2,
Wherein when the load-side automation switch is one, the phase-by-phase current difference is a value obtained by subtracting a phase current value of the load-side switch from a phase current value of the power-side switch. The method of claim 2,
Wherein when the number of load-side automation switches is two or more, a value obtained by doubling the phase current value of the maximum power-side switch is subtracted from a sum of the phase current values of the load-side switches. The method according to claim 1,
Wherein the fault section is a section having a largest phase current difference. The method of claim 6,
In the fault section checking step
And determining a fault section as a fault section if the phase difference difference of the fault section exceeds a reference value as compared with an average value of the phase difference difference.

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