Power distribution system capable of automatic fault detection in a distributed manner and method thereof

A power distribution system capable of automatic fault detection includes a lateral, a switch unit and a feeder terminal unit. The switch unit includes a circuit breaker coupled for transmitting electrical power to the lateral when making electrical connection, and a protection relay to provide a control signal that causes the circuit breaker to break electrical connection upon determining that the magnitude of a current provided by the circuit breaker is greater than a threshold current value. The feeder terminal unit detects whether or not the protection relay generates the control signal, so as to determine whether or not a fault has occurred in the lateral.

FIELD

The disclosure relates to a power distribution system, and more particularly to a power distribution system capable of automatic fault detection in a distributed manner.

BACKGROUND

A conventional power distribution system usually includes a supervisory control and data acquisition (SCADA) system, a plurality of 4-way switch units and a plurality of laterals. Each 4-way switch unit is coupled between the SCADA system and multiple laterals, and each lateral is coupled to multiple loads. The SCADA system may control feeding of electrical power to the loads through the 4-way switches and the corresponding laterals, and continuously detect operation of each of the 4-way switch units. The SCADA system is able to identify one of the 4-way switch units to which a lateral that has a fault is coupled, in order to perform fault detection, isolation and restoration (FDIR) on the faulted lateral.

The FDIR process of the conventional power distribution system may have the following drawbacks:

1. The power distribution system is unable to promptly become aware of the occurrence of a fault and thus FDIR cannot be performed speedily: since each of the 4-way switch units is coupled to the SCADA system, the SCADA system must monitor operation of each of the 4-way switch unit in order to identify the 4-way switch unit coupled to the faulted lateral for subsequent manual execution of the FDIR on that lateral, thereby delaying completion of FDIR.

2. Complex program design: since each of the 4-way switch units and the laterals is directly detected and controlled by the SCADA system, program design for the SCADA system is rather complicated.

SUMMARY

Therefore, an object of the disclosure is to provide a power distribution system that may quickly detect occurrence of a fault with a relatively simple program design.

According to the disclosure, the power distribution system includes at least one lateral, at least one switch unit and at least one feeder terminal unit (FTU). The switch unit includes a circuit breaker coupled to the lateral for transmitting electrical power to the lateral when making electrical connection, and a protection relay coupled to the circuit breaker, and configured to detect whether or not a magnitude of a current provided by the circuit breaker is greater than a threshold current value, and to generate, upon determining that the magnitude of the current is greater than the threshold current value, a control signal that causes the circuit breaker to break electrical connection. The FTU is coupled to the switch unit, and is configured to detect whether or not the protection relay generates the control signal, and to determine whether or not a fault has occurred in the lateral according to the detection.

Another object of the disclosure is to provide a fault detection method for the power distribution system of this disclosure.

According to the disclosure, the fault detection method is provided for a power distribution that includes at least one lateral, at least one switch unit and at least one feeder terminal unit (FTU). The switch unit includes a circuit breaker coupled to the lateral for transmitting electrical power to the lateral when making electrical connection, and a protection relay coupled to the circuit breaker. The fault detection method includes the steps of: a) detecting, by the protection relay, whether or not a magnitude of a current provided by the circuit breaker is greater than a threshold current value; b) generating, by the protection relay, a control signal that causes the circuit breaker to break electrical connection upon determining that the magnitude of the current is greater than the threshold current value in step a); and c) determining, by the FTU, whether or not a fault has occurred in the lateral by detecting whether or not the protection relay generates the control signal.

DETAILED DESCRIPTION

Referring toFIG. 1, an embodiment of the power distribution system with distributed fault detection according to this disclosure is shown to include at least one power distribution control module1, an analyzing and control system6, a first feeder remote terminal unit (FRTU)4and a second FRTU5. In this embodiment, there is only one power distribution control module1; however, this disclosure is not limited in terms of the number of the power distribution control module1.

The power distribution control module1includes a number (M) of first control circuits11coupled to each other one by one in series, a number (N) of second control circuits12coupled to each other one by one in series, and a number (L) of laterals13, where each of M, N and L is a positive integer. Each first/second control circuit11,12has a first output terminal and a second output terminal, and each lateral13has a first terminal and a second terminal. In this embodiment, M<N and L=2M, where M=1, N=2 and L=2, but the disclosure is not limited thereto.

Each first control circuit11outputs a first driving power and a second driving power respectively at the first and second output terminals thereof, where the first driving power and the second driving power are associated with a first primary driving power provided by a power substation (not shown). In this embodiment, each first control circuit11includes a first 4-way switch unit111and a first feeder terminal unit (FTU)112.

For each first control circuit11, the first 4-way switch unit111thereof includes two switch elements113,114that are coupled in series and that are closed in a normal condition (i.e., faultless condition), a first circuit breaker (CB)115, a second CB116and a protection relay117. Each of the first and second CBs115,116has a first terminal coupled to a common node (R) of the switch elements113,114, and a second terminal serving as a respective one of the first and second output terminals of the first control circuit11at which the corresponding one of the first and second driving power is outputted. The protection relay117is coupled between the second terminals of the first and second CBs115,116for detecting a first/second current (resulting from the first/second driving power) provided by the first/second CB115/116, and determines whether or not a magnitude of the first/second current is greater than a first/second threshold current value (i.e., a short-circuit fault). When the determination for the first/second current is affirmative, the protection relay117generates a first/second control signal (C1/C2), and provides the first/second control signal (C1/C2) to the corresponding first/second CB115,116, to thereby cause the corresponding first/second CB115,116to break electrical connection thereof.

The first FTU112is coupled to the first 4-way switch unit111, detects whether or not the protection relay117generates the first and/or second control signals (C1, C2), and determines whether a fault has occurred according to the detection. Specifically, when it is detected that the protection relay117generates the first and/or second control signals (C1, C2), the first FTU112determines that a fault has occurred.

When M<N, as with this embodiment, each of the first output terminal of a first one of the second control circuits12and the second output terminal of an Nthone of the second control circuits12may be coupled to a corresponding circuit unit (not shown), which may be a lateral or other circuits. For other output terminals of the second control circuits12, power outputted at each first output terminal is called a third driving power, and power outputted at each second output terminal is called a fourth driving power, where the third driving power and the fourth driving power are associated with a second primary driving power which may be provided by another power substation (not shown). In this embodiment, each of the second control circuits12includes a second 4-way switch unit121and a second FTU122, and the second 4-way switch units121of the second control circuits12are, but not limited to, coupled to each other one by one in series.

For each second control circuit12, the second 4-way switch unit121thereof includes two switch elements123,124, a first CB125, a second CB126and a protection relay127. Each of the first and second CBs125,126has a first terminal coupled to a common node (Q) of the switch elements123,124, and a second terminal serving as a corresponding one of the first and second output terminals of the second control circuit12at which the corresponding one of the third and fourth driving power is outputted. The protection relay127is coupled between the second terminals of the first and second CBs125,126for detecting a third/fourth current provided by the first/second CB125/126, and determines whether or not a magnitude of the third/fourth current (resulting from the third/fourth driving power) is greater than a third/fourth threshold current value. When the determination for the third/fourth current is affirmative, the protection relay127generates a third/fourth control signal (C3/C4), and provides the third/fourth control signal (C3/C4) to the corresponding first/second CB125,126, to thereby cause the corresponding first/second CB125,126to break electrical connection thereof.

The second FTU122is coupled to the second 4-way switch unit121, and detects whether or not the protection relay127generates the third and/or fourth control signals (C3, C4), so as to determine whether a fault occurs.

When M<N, the first and second terminals of a (2i−1)thone of the laterals13are respectively coupled to the first output terminal of an ithone of the first control circuit(s)11and the second output terminal of an ithone of the second control circuits12for respectively receiving the first driving power and the fourth driving power therefrom, where 1≦i≦M. The first and second terminals of a (2i)thone of the laterals13are respectively coupled to the second output terminal of the ithfirst control circuit11and the first output terminal of an (i+1)thone of the second control circuits12for respectively receiving the second driving power and the third driving power therefrom. Each lateral13includes a plurality of first sub-switch units131that are divided into a first switch group and a second switch group, a second sub-switch unit132between the first switch group and the second switch group, and a number (Y) of loads133, where Y is a positive integer. In this embodiment, the number of the first sub-switch units131is five and Y=7, but this disclosure is not limited thereto.

For each lateral13, each of the first and second sub-switch units131,132includes a lateral terminal unit (LTU, seeFIG. 7) that continuously provides to the corresponding first and second FTU(s)112,122a fault detection signal that indicates an operation condition of the respective first or second sub-switch unit131,132, and a 2-way switch134. Particularly, for each of the first and second sub-switch units131,132, the LTU may detect a current information associated with the 2-way switch134, and generate a fault flag to serve as the fault detection signal upon detecting that the current information thus detected is abnormal (e.g., a current thus detected falls outside of a predetermined range). The 2-way switches134of the first and second sub-switch units131,132are electrically coupled in series, and the 2-way switch134of the second sub-switch unit132interconnects the 2-way switch134of a terminal of the first sub-switch units131of the first switch group and the 2-way switch134of a terminal of the first sub-switch units131of the second switch group. In this embodiment, the LTUs respectively detect currents flowing through the 2-way switches134, thereby providing the fault detection signals to the first and second FTUs112,122. The 2-way switches134of the first sub-switch units131of the first switch group are coupled to each other one by one between the first terminal of the lateral13and the 2-way switch134of the second sub-switch unit132to forma first conduction path (P1), while the 2-way switches134of the first sub-switch units131of the second switch group are coupled to each other one by one between the second terminal of the lateral13and the 2-way switch134of the second sub-switch unit132to form a second conduction path (P2). In this embodiment, the first switch group has three first sub-switch units131, and the second switch group has two first sub-switch units131, but this disclosure is not limited thereto. In this embodiment, when the lateral13operates in the normal/faultless condition, each of the first sub-switch units131permits power transmission therethrough, and the second sub-switch unit132disables power transmission therethrough. In other words, in the normal condition, the 2-way switches134of the first sub-switch units131are closed and the switch131of the second sub-switch unit132is open.

For each lateral13, 1stand Ythones of the loads133are respectively coupled to the first and second terminals of the lateral13, and each of second to (Y−1)thones of the loads133is coupled to a respective pair of adjacent sub-switch units131,132. The loads133of each lateral13receive corresponding first or second driving power via the first conduction path (P1), or receive corresponding third or fourth driving power via the second conduction path (P2).

In this embodiment, the analyzing and control system6may be a supervisory control and data acquisition (SCADA) system, and includes an analyzing module2to collect, via a communication network (e.g., a fiber network), information (e.g., electric current information) of the laterals13via a hierarchical structure of the first and second FRTUs4,5, the first and second FTUs112,122and LTUs for analysis, thereby generating an analysis result, and a control module3to control operations of the first and second FTUs112,122according to the analysis result.

In a first exemplary condition depicted inFIG. 1, a fault occurs at a fault location (f1) in the first conduction path (P1) of a first one of the laterals13.

FIGS. 1, 2 and 3A to 3Dare used to cooperatively illustrate the embodiment of a distributed fault detection method implemented by the power distribution system when the laterals13are in the first exemplary condition. It is noted that, inFIGS. 3A to 3D, the first CB115is exemplified using a switch, and the distributed fault detection method is described using only the first control circuit11and the corresponding first conduction path (P1) for the sake of brevity, but this disclosure is not limited thereto. The first control circuit11may perform FDIR on the first conduction path (P1) of the first lateral13according to the distributed fault detection method, which includes the following steps60-69.

Step60: The protection relay117detects whether or not the magnitude of the first current provided by the first CB115is greater than the first threshold current value. The flow goes to step61when the determination is affirmative, and goes back to step60when otherwise.

Step61: The protection relay117generates the first control signal (C1) that is provided to the first CB115and that causes the first CB115to break electrical connection (seeFIG. 3A).

Step62: Upon detecting that the protection relay117has generated the first control signal (C1), the first FTU112determines that there is a fault with the lateral13, and the flow goes to step63.

Step63: The first FTU112determines the fault location (f1) of the lateral13at which the fault occurs according to the fault detection signal received from each of the first and second sub-switch units131,132before the first CB115breaks electrical connection, and the flow goes to step64.

For example, before the first CB breaks electrical connection, if the fault detection signal generated by a third one of the first sub-switch units131is different from those generated by first, second, fourth and fifth ones of the first sub-switch unit131and the second sub-switch unit132, which are the same thereamongst, the first FTU112determines that the fault location (f1) is between the second and third ones of the first sub-switch units131according to the fault detection signals generated by the sub-switch units131,132. Note that the first and fifth ones of the first sub-switch units131refer to the leftmost and rightmost ones of the first sub-switch units131, respectively, as depicted in the drawings.

Step64: The first FTU112causes the 2-way switches134of two of the first sub-switch units131that are located most adjacent to the fault location (f1) along the one-by-one serial connection to break electrical connections, to thereby disable power transmission through those two first sub-switch units131when at least one of the first sub-switch units131is located between the fault location (f1) and the second sub-switch unit132, as shown inFIG. 3B(condition 1), and the flow goes to step65. When none of the first sub-switch units131is located between the fault location (f1) and the second sub-switch unit132, i.e., the fault location (f1) is located most adjacent to the second sub-switch unit132and one of the first sub-switch units131(condition 2), the first FTU112causes only the 2-way switch134of said one of the first sub-switch units131to break electrical connection, to thereby disable power transmission through that first sub-switch unit131, and the flow goes to step66. In other words, the fault location (f1) is isolated as a consequence of step64. After completion of step64, maintenance technicians may immediately perform maintenance/repair at the fault location (f1).

Step65: The first FTU112causes the first CB115to make electrical connection, as shown inFIG. 3C, and causes the 2-way switch134of the second sub-switch unit132to make electrical connection, to thereby permit power transmission through the second sub-switch unit132, as shown inFIG. 3D. Then, the flow goes to step67.

Step66: The first FTU112causes the first CB115to make electrical connection, as shown inFIG. 3C, and the flow goes to step67.

Step67: The analyzing module2makes an analysis for the fault location (f1) according to information (e.g., current information) collected thereby, and generates the analysis result that indicates whether or not the fault at the fault location (f1) has been fixed, which should be affirmative if the maintenance/repair at the fault location (f1) has been completed properly. The flow goes to step68when the analysis result indicates that the fault has been fixed, and goes back to step67when otherwise.

For example, the analyzing module2analyzes whether or not a third conduction path (P3) between the two of the first sub-switch units131that are most adjacent to the fault location (f1) normally conducts in order to generate the analysis result that indicates whether or not the fault has been fixed.

Step68: The analyzing module2provides to the control module3the analysis result which indicates that the fault has been fixed.

Step69: Upon receipt the measured result provided in step68, the control module3controls the first FTU112to cause the 2-way switch(es)134of the first sub-switch unit(s)131that is(are) located most adjacent to the fault location (f1) to make electrical connections, to thereby permit power transmission through the first sub-switch unit(s)131, and to cause the 2-way switch134of the second sub-switch unit132to break electrical connection, to thereby disable power transmission through the second sub-switch unit132.

At this time, the first lateral13returns to the normal/faultless condition, as shown inFIG. 1(ignoring the label f1).

As a result, by implementation of the distributed fault detection method using the embodiment of the power distribution system, occurrence of faults may be quickly identified via each FTU112detecting the corresponding 4-way switch unit111, so that the subsequent FDIR process may be performed relatively promptly.

Referring toFIG. 4, a first variation of the embodiment of the power distribution system is shown to be similar to the embodiment depicted inFIG. 1, and differs therefrom in that M>N and L=2N, where M, N and L are respectively the numbers of the first control circuits11, the second control circuits12and the laterals13. In the depicted example of the first variation, M=2, N=1 and L=2, but this disclosure is not limited thereto.

When M>N, each of the first output terminal of a first one of the first control circuits11and the second output terminal of an Mthone of the first control circuits11may be coupled to a corresponding circuit unit (not shown), which may be a lateral or other circuits. For other output terminals of the first control circuits11, each first output terminal outputs the first driving power to the corresponding lateral13, and each second output terminal outputs the second driving power to the corresponding lateral13, where the first driving power and the second driving power are associated with the first primary driving power. The second control circuit12outputs to corresponding laterals13the third driving power and the fourth driving power respectively at the first and second output terminals thereof, where the third driving power and the fourth driving power are associated with the second primary driving power. The first and second terminals of a (2i−1)thone of the laterals13are respectively coupled to the second output terminal of an ithone of the first control circuits11and the first output terminal of an ithone of the second control circuit(s)12for respectively receiving the second driving power and the third driving power therefrom, where 1≦i≦N. The first and second terminals of a (2i)thone of the laterals13are respectively coupled to the first output terminal of an (i+1)thone of the first control circuits11and the second output terminal of the ithsecond control circuit12for respectively receiving the first driving power and the fourth driving power therefrom.

The first variation of the first embodiment of the power distribution system may implement the distributed fault detection method in a manner similar to that described hereinabove, and details are not repeated herein for the sake of brevity.

Referring toFIG. 5, a second variation of the embodiment of the power distribution system is shown to be similar to the embodiment depicted inFIG. 1, and differs therefrom in that M=N and L=2M−1. InFIG. 5, M=N>1, where M=2, N=2 and L=3, but this disclosure is not limited thereto.

When M=N>1, each of the first output terminal of a first one of the second control circuits12and the second output terminal of an Mthone of the first control circuits11may be coupled to a corresponding circuit unit (not shown), which may be a lateral or other circuits. For other output terminals of the first control circuits11, each first output terminal outputs the first driving power to the corresponding lateral13, and each second output terminal outputs the second driving power to the corresponding lateral13, where the first driving power and the second driving power are associated with the first primary driving power. For other output terminals of the second control circuits12, each first output terminal outputs the third driving power to the corresponding lateral13, and each second output terminal outputs the fourth driving power to the corresponding lateral13, where the third driving power and the fourth driving power are associated with the second primary driving power. The first and second terminals of a (2i−1)thone of the laterals13are respectively coupled to the first output terminal of an ithone of the first control circuits11and the second output terminal of an ithone of the second control circuits12for respectively receiving the first driving power and the fourth driving power therefrom, where 1≦i≦N. The first and second terminals of a (2i)thone of the laterals13are respectively coupled to the second output terminal of the ithone of the first control circuits11and the first output terminal of an (i+1)thone of the second control circuits12for respectively receiving the second driving power and the third driving power therefrom.

Furthermore, when M=N=1 and L=1 (not shown), each of the first output terminal of the second control circuit12and the second output terminal of the first control circuit11may be coupled to a corresponding circuit unit, which may be a lateral or other circuits. The first output terminal of the first control circuit11and the second output terminal of the second control circuit12respectively output the first driving power and the fourth driving power to the lateral13, where the first driving power and the fourth driving power are respectively associated with the first primary driving power and the second primary driving power. The first and second terminals of the lateral13are respectively coupled to the first output terminal of the first control circuit11and the second output terminal of the second control circuit12for respectively receiving the first driving power and the fourth driving power therefrom.

The second variation of the embodiment of the power distribution system may implement the distributed fault detection method in a manner similar to that described hereinabove, and details are not repeated herein for the sake of brevity.

Referring toFIG. 6, the laterals13of the embodiment of the power distribution system according to this disclosure are shown to be in a second exemplary condition, which is similar to the first exemplary condition and differs in that, instead of the fault location (f1) (seeFIG. 1), a fault occurs at the fault location (f2), which is in the second conduction path (P2).

Each second control circuit12may perform the abovementioned distributed fault detection method in a manner similar to that described for the first control circuit11in the first exemplary condition, and the details are not repeated herein for the sake of brevity.

In summary, the power distribution system of this disclosure may quickly identify the occurrence of a fault so as to perform FDIR on the lateral13at which the fault occurs. Since each of the control circuits11,12has the FTU (FTU)112,122to control operations of the corresponding 4-way switch unit111,121and lateral(s)13, the fault at any lateral13may be easily detected via the FTUs112,122detecting the corresponding 4-way switch units111,112, facilitating prompter subsequent FDIR on the faulted lateral13. As a result, time between occurrence of a fault till completion of the FDIR is reduced. In addition, since each of the 4-way switch units111,121and the laterals13is controlled by the corresponding control circuits11,12, a relatively simpler program design for the analyzing and control system6is sufficient in comparison to the conventional power distribution system in which all of the 4-way switch units and the laterals are directly controlled by the SCADA system.