KR20220168057A - Fault Location Method of Networked Distribution System - Google Patents

Abstract

The present invention relates to a fault location estimation method of a network distribution system, which may include: a failure section recognition step; a step of identifying two protective devices defining the fault section; a step of collecting measurement values at the point of failure of the fault section line in the identified two protective devices; a step of calculating a fault impedance of each of the two protective devices from the measured values at the time of the fault; and a step of calculating a fault location by applying the calculated fault impedance to a length of the fault section line between the two protective devices.

Description

Fault Location Method of Networked Distribution System {Fault Location Method of Networked Distribution System}

The present invention relates to a method for estimating a fault location in a network distribution system (or a loop-type distribution system) as a multi-linked distribution line at all times.

In general, the power distribution network of an electric power company consists of switchgear, poles, and distribution facilities such as lightning arresters, high-voltage cables and wires, from distribution substations to distribution transformers in demand areas, and is responsible for supplying high-voltage power to the high-voltage distribution networks and distribution networks. It consists of a low-voltage distribution network responsible for supplying low-voltage power from the secondary side of the dedicated transformer to low-voltage customers.

Conventional power distribution supply networks consist of dendritic structures in unimportant areas in most countries, including Korea, but the supply of always-on multi-connection distribution lines is increasing recently.

The dendritic distribution system is designed to supply the maximum load of the line throughout the year, but because the time required for the maximum load is very short, the line utilization rate is very low. Analyzed) This problem of deterioration in utilization rate is expected to accelerate due to the recent rapid increase in distributed resources (solar power generation, electric vehicles, etc.). In addition, when a fault occurs in a line, a power outage occurs for about 3 to 5 minutes until the faulty section is separated and power is supplied to the normal section.

In order to compensate for the disadvantages of such a dendritic distribution system, research on always-on multi-connected distribution lines is being conducted. The permanent multi-connected distribution line is a method in which a plurality of distribution lines, which were previously operated in a resin line, are mutually interconnected at all times. Continuously multi-connected distribution lines can improve facility utilization through load sharing (or distributed resources) between lines. In addition, since the voltage fluctuation problem caused by distributed resources can be solved, it is possible to improve the connection capacity. However, when a fault occurs, since the fault current flows into the fault point through a plurality of lines, it is not possible to properly separate the fault section with the existing protection method of the DC line. A comparison between the dendritic power distribution system and the network power distribution method is shown in Table 1 below.

When a fault occurs in the distribution system, the protection device automatically separates the fault section through protection coordination. In the dendritic system, power outages are experienced in all sections of the downstream side after the fault point, and in the network distribution system, only the fault section experiences power outages.

Even if there is such an automatic separation scheme for faulty sections, it is one of the very important indicators in terms of improving supply reliability and economic feasibility to quickly find a faulty point after a power outage, remove the fault, and restore the outage section. However, existing fault location estimation methods in dendritic systems contain large errors due to factors such as line inhomogeneity, mutual impedance, system imbalance, and the size of fault point resistance, and thus are not practically usable.

Therefore, in general, a specialist dispatched to the location from the previous week where the FI (fault indicator) occurred on the screen of the DAS (Distribution automation system) is located to find the cause of the failure through visual patrol. In this case, typical conspicuous failures such as magpies, tree contact, and ground faults due to disconnection can be found and solved without major problems, but in cases where it is difficult to visually identify (electric poles or underground lines installed in places with many obstacles), Failure recovery may be delayed. Sometimes, while looking for the cause of a breakdown, a specialized person in charge identifies the location of the breakdown through a complaint phone call.

There is no separate method for automatically estimating the fault location for the overhead line of the dendritic system, and the underground line goes to the place where the fault is presumed to be, separates the section, and detects the fault point using the Murray loop method, pulse measurement method, power outage bridge method, etc. are doing

These methods are very effective in estimating the fault location, but there are many exaggerations before they are applied. In the case of a network distribution system that is currently being developed and is scheduled to be finally demonstrated, fault current is supplied to both the upstream and load sides in the event of a fault, which is the existing technology. Since these cannot be applied, an automatic failure location estimation method is needed in preparation for this.

Republic of Korea Registration No. 10-0920946

An object of the present invention is to provide a method for estimating the location of a failure in a network distribution system that can simply and accurately identify a failure occurred in a distribution line of the network distribution system and the location of the failure.

A method for estimating a fault location in a network distribution system according to an aspect of the present invention includes recognizing a fault section; identifying two protective devices defining the fault section; Collecting measurement values at the point of failure of the fault section line in the identified two protection devices; Calculating a fault impedance of each of the two protection devices from the measured values at the time of the fault; The method may include calculating a fault location by applying calculated fault impedances to a length of the fault section line between the two protection devices.

Here, in the step of identifying the two protection devices, it is possible to obtain time-synchronized or time-tacked fault current and voltage measurements immediately before the fault, and protective device pairs forming a line section including the fault section line. Among them, a protection device pair having the minimum line length can be specified.

Here, in the fault section recognizing step, if the peak value polarity of the fault current measured in the two opposing protection devices is the same, it can be determined that a fault has occurred in the line section between the two protection devices.

Here, in the step of calculating the fault impedance, from the fault voltage and fault current measured immediately before each of the two protection devices performs an open operation according to a fault, the fault impedance from each protection device to the fault location is calculated. can

Here, in the step of calculating the fault location, the fault location may be calculated by estimating the ratio of the fault impedances from the two protection devices to the fault location as the ratio of the lengths from the two protection devices to the fault location. there is.

Here, the fault location estimation method may be performed in the form of an application program in a computing device of a device provided on a network distribution line.

A method for estimating a fault location in a network distribution system according to another aspect of the present invention includes recognizing a fault section; designating a first protection device pair composed of two protection devices so that a line between the two protection devices includes the fault section; designating a second protection device pair composed of two protection devices so that a portion of a line between two protection devices overlaps a portion of a line of the first protection device pair and includes the fault section; Calculating a fault location using measurement values at the point of failure collected from two protective devices constituting the first protective device pair; Calculating a fault location using measurement values at the point of failure collected from the two protection devices forming the second protection device pair; and determining a failure location as an average of a failure location calculated for the first protection device pair and a failure location calculated for the second protection device pair.

Here, the step of calculating the fault location for the first protection device pair and the step of calculating the fault location for the second protection device pair are the fault section line of the two protection devices constituting the protection device pair. Collecting measurement values at the point of failure; Calculating a fault impedance of each of the two protection devices from the measured values at the time of the fault; The method may include calculating a fault location by applying calculated fault impedances to a length of the fault section line between the two protection devices.

Here, in the step of designating the first protective device pair, it is possible to obtain time-synchronized or time-tacked fault current and voltage measurement values immediately before the fault, and a protective device pair forming a line section including the fault section line. Among them, a protective device pair having the minimum line length can be specified.

Here, in the fault section recognizing step, if the peak value polarity of the fault current measured in the two opposing protection devices is the same, it can be determined that a fault has occurred in the line section between the two protection devices.

If the method for estimating the fault location of the network distribution system according to the spirit of the present invention having the above configuration is implemented, there is an advantage in that the fault and fault location occurring in the distribution line of the rather complex network distribution system can be accurately identified according to software without additional configuration. there is.

The method for estimating the fault location of the network distribution system according to the spirit of the present invention has the advantage of minimizing manpower input and outage time by quickly finding the fault point in the network distribution system.

The method for estimating the location of a failure in a network distribution system according to the spirit of the present invention has the advantage of dramatically reducing power outage time and enabling high-quality and highly reliable power supply.

1 is a flowchart illustrating an embodiment of a method for estimating a location of a failure according to the spirit of the present invention.
2 is a conceptual diagram illustrating a ground fault of a distribution line;
3 is a conceptual diagram for prescribing fault impedance for each distance according to selection of two protection devices serving as standards for fault impedance calculation.
FIG. 4 is a flowchart illustrating a method for estimating a location of a failure performed by averaging estimated values derived from each of the plurality of protective device pairs described above.
Figure 5a is a network distribution system 1-line ground fault simulation circuit diagram for confirming the suitability of the fault location expression in the network distribution system.
Figure 5b is a result table of the measured voltage and current of the power-side protective device in case of failure in the simulation according to Figure 5a.
Figure 5c is a result table of the measured voltage and current of the load-side protective device in case of failure in the simulation according to Figure 5a.

In describing the present invention, terms such as first and second may be used to describe various components, but the components may not be limited by the terms. Terms are only for the purpose of distinguishing one element from another. For example, a first element may be termed a second element, and similarly, a second element may be termed a first element, without departing from the scope of the present invention.

When a component is referred to as being connected or connected to another component, it may be directly connected or connected to the other component, but it may be understood that another component may exist in the middle. .

Terms used in this specification are only used to describe specific embodiments, and are not intended to limit the present invention. Singular expressions may include plural expressions unless the context clearly dictates otherwise.

In this specification, the terms include or include are intended to designate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, and one or more other features or numbers, It can be understood that the presence or addition of steps, operations, components, parts, or combinations thereof is not precluded.

In addition, the shapes and sizes of elements in the drawings may be exaggerated for clearer description.

Unlike the dendritic system, since the network system is a bidirectional power source, the fault location can be automatically derived immediately after a fault occurs through the fault location estimation method according to the spirit of the present invention.

In the fault location estimation method according to the spirit of the present invention, fault impedance (a different concept from fault resistance, the ratio of voltage and current measured in a protective device in case of a fault) is used as an element for estimating the fault location, and the key contents Is as follows.

When a fault occurs in the network distribution system, protective devices at both ends of the fault section open. Calculate the fault impedance (ZF) through the fault voltage and fault current measured just before opening. At this time, the ratio of the fault impedance (ZFA) from the 'power-side protective device to the fault point' and the fault impedance (ZFB) from the 'fault point to the load-side protective device' is the distance from the 'power-side protective device to the fault point' (x) and the distance from the fault point to the load-side protective device (L-x, L: total distance between protective devices) (ZFA : ZFB = x : L-x). The fault location can be determined using the above-mentioned fault impedance, and the fault point can be quickly found, and manpower input and outage time can be minimized.

1 is a flowchart illustrating an embodiment of a method for estimating a location of a failure according to the spirit of the present invention.

The illustrated failure location estimation method includes a failure section recognizing step (S20); Identifying two protective devices defining the failure section (S40); Collecting measurement values at the point of failure of the fault section line in the identified two protection devices (S60); Calculating the fault impedance of each of the two protective devices from the measured values at the time of the fault (S65); It may include calculating a fault location (point) by applying the calculated fault impedances to the length of the fault section line between the two protection devices (S80).

In the fault section recognizing step (S20), it is possible to recognize a line section in which a failure has occurred in the network distribution system according to the prior art.

Alternatively, in the fault section recognition step (S20), when a fault occurs in the network distribution system distribution line, fault current is supplied from both directions (power side, load side) of the fault point, and the fault current measured by the protection devices on both sides based on the fault point The polarity of the peak value at every moment is the same, and the polarity of the peak value measured by the protection device facing the opposite direction is the same by using the fact that the peak value polarity of the fault current measured by the two protection devices facing each other is the same. It can be judged that this has occurred.

In the step of identifying the two protection devices (S40), designating the two protection devices to form a line section having the minimum length and including the fault section recognized in the step S20 is It is advantageous in terms of accuracy, but not limited thereto, and forms a line section longer than the minimum length, but other two protection devices that are easy to obtain time-tagged fault current/voltage measurement values may be designated.

The two designated protection devices must be devices capable of time-tacking or generating time-synchronized measured values with respect to the imminent failure.

For example, two protection devices may be designated so that the length of a line section including the fault section is the minimum length among protection devices obtained with current/voltage measurement values belonging to a predetermined time section from the time of failure.

Here, the line section means a line section between the two designated protection devices.

Accordingly, in the step of calculating the fault impedance (S65), from the fault voltage and fault current measured immediately before each of the two protection devices perform an open operation according to the fault, the fault location in each protection device. Fault impedance can be calculated.

In the step of calculating the fault location (S80), the fault location is calculated by estimating the ratio of the fault impedances from the two protection devices to the fault location as the ratio of the lengths from the two protection devices to the fault location. can

Next, the principle of the method of calculating the fault impedance applied in step S65 and the method of calculating the fault location in step S80 will be described.

2 is a conceptual diagram illustrating a ground fault in a distribution line.

As shown in the network distribution system, when a line failure occurs, the fault voltage and fixed current are measured in the control box of the electric pole (equipment main) where the equipment is installed. Fault impedance can be calculated through the voltage and current measured at each equipment main. At this time, the 'fault impedance ratio' derived from the specific both ends of the line where the fault occurs means the 'electrical distance ratio' at the corresponding both ends, and in most cases, this is very similar to the actual distance ratio.

In other words, the ratio of “Protection device A ~ Fault point (150m): Fault point ~ Protection device B (50m)” is 3: 1 when divided, and the calculated Z _FA : Z _FB also has the same value as 3: 1 . Here, Z _FA is the calculated fault impedance in reporting device A, and Z _FB is the calculated fault impedance in reporting device B.

In the case of a 1-wire ground fault, only the fault impedance of the fault phase needs to be obtained, but in the case of a 2-wire and 3-wire ground fault, it is preferable to obtain all fault impedances for each phase. However, in case of 2-wire and 3-wire ground faults, each calculated value is generally similar, so it is okay to calculate 2 times and 3 times of one phase.

In detail, the calculation method for each failure type is shown in Table 2 below.

The fault voltage measured at the equipment main, which is one of the two protection devices identified in step S40, is V _LN , the fault current (ground fault current: I _Ground , short circuit current: I _Fault ) is I _{F (G)} , and the fault current is I F (G). The fault impedance (ZF) can be defined by dividing the voltage by the fault current, which can be expressed as in Equation 1 below.

To estimate the location of a 2-wire ground fault, the fault impedances of each fault phase must be calculated and summed. In the case of 3-wire ground fault and 3-wire short circuit, the fault impedances of each fault phase are calculated and summed. After the power-side and load-side fault impedances are calculated, the fault location is determined using the distance ratio (actual distance vs. electrical distance) as shown in Equations 2 to 4 below. At this time, x is the distance from the reference point (protection device A position) to the fault point, and L means the total length between the protection devices.

In the fault location estimation method according to the spirit of the present invention described above, once the fault section is identified in step S20, a line section between two protection devices such as a circuit breaker and a switch is based on the line section including the fault section (S40), it is possible to accurately determine the location of the failure in the above steps S60 to S80.

The above-described method for estimating a location of a failure may be performed in a computing device of a device on a distribution line in the form of an application program (software) without additional hardware. As a device on the distribution line, various devices/servers such as IEDs that control circuit breakers, smart terminal devices in the field, such as FRTUs for breakers/switches, upper distribution management servers, and local substation operation servers, etc. can be applied. .

3 is a conceptual diagram defining fault impedance for each distance according to selection of two protection devices, which are standards for calculating fault impedance.

In the network distribution system, the concepts of the power side and the load side are virtually ambiguous, but in the present invention, for convenience, the direction close to the substation is defined as the power side and the far echo is defined as the load side. The size of the load and the length of the branch line associated with the fault section do not cause errors. Considering the accuracy of the measured voltage and current values, the error range is ±5% or less if the length is more than 400m, and the error range is ±10% or less if the length is less than 400m.

As shown in FIG. 3, the error rate can be reduced by deriving a plurality of values as [ZFA: ZFB], [ZFA: ZFC], and [ZFA: ZFD] and averaging the values. This error occurs when a part of the distribution line contains CNCV (because the impedance is much smaller than that of ACSR).

That is, when designating a pair of protection devices to include the fault section (the line section between protection device A and protection device B including the fault point) in the line section between each other in FIG. 3, 'protection device A - protection device B' , 'protection device A - protection device C' and 'protection device A - protection device D' exist.

For each of the three protective device pairs, the fault location estimation method using the fault impedance ratio according to the spirit of the present invention is performed, and the final fault location can be determined with the average value of the three fault locations obtained according to the three results performed. there is.

FIG. 4 is a flowchart illustrating a method for estimating a location of a failure performed by averaging estimated values derived for each of the plurality of protection device pairs described above.

The illustrated failure location estimation method includes a failure section recognizing step (S200); designating a first protection device pair (which may be a line of a minimum length) composed of two protection devices so that a line between the two protection devices includes the fault section (S401); A part of the line between the two protection devices overlaps a part of the line of the first protection device pair, and designating a second protection device pair composed of two protection devices to include the fault section (S402) ; Calculating a fault location using measurement values at the point of failure collected from the two protection devices forming the first protection device pair (S621, S651, S681); Calculating a fault location using measurement values at the point of failure collected from the two protection devices forming the second protection device pair (S622, S652, S682); and determining the failure location as an average of the failure locations calculated for the first pair of protection devices and the locations of failures calculated for the second pair of protection devices ( S800 ).

As shown, depending on the implementation, the step of calculating the fault location using the measured values at the point of failure collected from the two protection devices constituting the third protection device pair may be performed up to the Nth protection device pair ( S62N, S65N, S68N).

As shown, calculating a fault location for the first protection device pair (S621, S651, S681), calculating a fault location for the second protection device pair (S622, S652, S682), and The step of calculating the fault location for the second protection device pair (S62N, S65N, S68N) is the step of collecting measurement values at the time of failure of the fault section line in the two protection devices constituting the protection device pair ( S621, S622, S62N); Calculating the fault impedance of each of the two protection devices from the measured values at the time of the fault (S651, S652, S65N); and calculating a fault location by applying the calculated fault impedances to the length of the fault section line between the two protection devices (S681, S682, S68N).

Depending on the implementation, in the step of designating the first protective device pair (S401), time synchronization or time-tacked fault current and voltage measurement values immediately before the fault may be obtained, and the line section including the fault section line Among protection device pairs formed, a protection device pair having the minimum line length can be designated.

5A is a network distribution system 1-line ground fault simulation circuit diagram for confirming the suitability of a fault location expression in a network distribution system.

FIG. 5B is a result table of measured voltage and current of the power-side protective device in case of a failure in the simulation according to FIG. 5A.

FIG. 5C is a result table of measured voltage and current of the load-side protection device in case of failure in the simulation according to FIG. 5A.

A result of applying the fault location estimation method according to the spirit of the present invention to the circuit diagram of FIG. 5A is illustrated.

A portion marked with a red line box in FIG. 5A is a total 2 km section of an overhead line trunk line (ACSR). At the midpoint (1 km), the branch line extends 1 km and has a load of 1 MVA. There is a switch at both ends of the line, and the fault occurred at the 50% point of the upper overhead line (500m from the power side) and caused a ground fault on the first line.

5b and 5c show fault voltage and fault current for each protection device. Through this, the fault impedance is obtained as shown in Equation 5 below.

From the calculation results of the above-described simulation contents, it can be seen that the distance from the power-side protective device to the fault point is calculated as the 0509km point, and has an error of 9 meters (error rate 18%).

Those skilled in the art to which the present invention pertains should understand that the embodiments described above are illustrative in all respects and not limiting, since the present invention can be embodied in other specific forms without changing the technical spirit or essential characteristics thereof. only do The scope of the present invention is indicated by the following claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts should be construed as being included in the scope of the present invention. .

For example, in the description of the present invention, the network distribution system, in which estimation of the fault location is technically more difficult, is embodied and explained, and this is emphasized in the title of the invention, but the fault location estimation method according to the spirit of the present invention is also applied to the loop-type distribution system. It can be done, and this also belongs to the scope of the present invention, of course.

S20: Fault section recognition step
S40: step of identifying two protection devices
S60: Collecting measurement values at the point of failure
S65: Calculate fault impedance;
S80: step of calculating the fault location

Claims (10)

failure section recognition step;
identifying two protective devices defining the fault section;
Collecting measurement values at the point of failure of the fault section line in the identified two protection devices;
Calculating a fault impedance of each of the two protection devices from the measured values at the time of the fault;
Calculating a fault location by applying calculated fault impedances to the length of the fault section line between the two protection devices
A method for estimating the location of a fault in a network distribution system comprising a.
According to claim 1,
In the step of identifying the two protection devices,
It is possible to obtain time-synchronized or time-tacked fault current and voltage measurement values immediately before a fault, and designate a pair of protection devices having the minimum line length among protection device pairs forming a line section including the line of the fault section. fault location estimation method.
According to claim 1,
In the failure section recognition step,
A fault location estimation method for determining that a fault has occurred in a line section between the two protection devices when the peak polarity of the fault current measured in the two opposing protection devices is the same.
According to claim 1,
In the step of calculating the fault impedance,
Fault location estimation method for calculating the fault impedance from each protection device to the fault location from the fault voltage and fault current measured immediately before each of the two protection devices performs an open operation according to a fault.
According to claim 4,
In the step of calculating the fault location,
A fault location estimation method for calculating a fault location by estimating a ratio of fault impedances from the two protection devices to a fault location as a ratio of lengths from the two protection devices to the fault location.
According to claim 1,
The fault location estimation method,
A failure location estimation method performed in the form of an application program in a computing device of a device provided on a network distribution line.
failure section recognition step;
designating a first protection device pair composed of two protection devices so that a line between the two protection devices includes the fault section;
designating a second protection device pair composed of two protection devices so that a portion of a line between two protection devices overlaps a portion of a line of the first protection device pair and includes the fault section;
Calculating a fault location using measurement values at the point of failure collected from two protective devices constituting the first protective device pair;
Calculating a fault location using measurement values at the point of failure collected from the two protection devices forming the second protection device pair; and
Determining the fault location as an average of the fault position calculated for the first protective device pair and the fault position calculated for the second protective device pair
A method for estimating the location of a fault in a network distribution system comprising a.
According to claim 7,
calculating a failure location for the first protection device pair; and
The step of calculating the fault location for the second protection device pair,
Collecting measured values at the point of failure of the line in the failure section in the two protection devices forming a protection device pair;
Calculating a fault impedance of each of the two protection devices from the measured values at the time of the fault;
Calculating a fault location by applying calculated fault impedances to the length of the fault section line between the two protection devices
A method for estimating the location of a fault in a network distribution system comprising a.
According to claim 7,
In the step of designating the first protection device pair,
It is possible to obtain time-synchronized or time-tacked fault current and voltage measurement values immediately before a fault, and designate a pair of protection devices having the minimum line length among protection device pairs forming a line section including the line of the fault section. fault location estimation method.
According to claim 7,
In the failure section recognition step,
A fault location estimation method for determining that a fault has occurred in a line section between the two protection devices when the peak polarity of the fault current measured in the two opposing protection devices is the same.

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