TWI550989B - Fault Detection Method and System of Communication Divergence Fault - Google Patents

Description

Communication type bifurcation line fault automatic detection method and system

The invention relates to a circuit detecting method and system for power supply or power distribution, in particular to a communication type bifurcation line fault automatic detecting method and system.

The existing power distribution system includes a feeder main device, a plurality of main feeder circuits, a plurality of branch line circuits, and a plurality of fiber optic communication circuits, each main feeder circuit being electrically connected between the feeder main device and the plurality of bifurcation circuits. Each of the branch line circuits electrically connects a plurality of loads, and the feeder main unit supplies power to the electrically connected load via each of the main feeder circuits and their corresponding branch line circuits. And each main feeder circuit is electrically connected to each of the optical fiber communication circuits, so that when the power distribution accident causes a failure, the corresponding faulty signal is transmitted to the feeder main device through the corresponding optical fiber communication circuit, so that the main feeder device is Perform Fault Detection Isolation and Restoration (FDIR) on the main feeder circuit.

However, power distribution accidents occur mostly in these branch line circuits, but since the existing fiber optic communication circuits are only installed in the main feeder circuits, failures occurring in the branch line circuits cannot be effectively transmitted back to the feeder main unit. In addition, due to the large number of circuits of these bifurcation lines, one by one The way in which a branch line circuit sets the fiber optic communication circuit is not cost effective.

Therefore, the object of the present invention is to provide a communication type bifurcation line fault automatic detection method.

Therefore, the communication type bifurcation fault automatic detection method is implemented by a communication bifurcation fault automatic detection system, and the communication bifurcation fault automatic detection system is suitable for transmitting a plurality of driving currents, and the communication divergence line The fault automatic detection system comprises a complex bifurcation circuit, each bifurcation circuit comprising a first substation to an nth substation connected in series, n=2~N, wherein the kth substation is a preset normally open point Station, k<N, k, N are positive integers and k≧2, and any two substations are electrically connected by a power line, and wherein the i-th sub-station is the upstream sub-station of the i+1th substation, i+ 1 substation is the downstream substation of the i-th substation, 1≦i<k, and the automatic detection method of the communication bifurcation line fault includes a step (A), a step (B), a step (C), and One step (D).

The step (A) is that each of the first to kth substations detects the driving current to determine whether there is an overcurrent, and correspondingly records a flag related to whether an overcurrent is present, the first When at least one of the substations to the kth substation records the flag of the overcurrent, the process proceeds to step (B).

The step (B) is that the i-th substation sends an inquiry signal having the flag to the i+1th substation via the power line.

The step (C) is that the i+1th substation determines, according to the flag from the i-th substation and the flag of the i+1 substation, whether a fault point occurs in the i-th substation and the i-th station +1 sub-station.

This step (D) is to increase the value of i by 1 when the step (C) is NO, and return to the step (B).

Furthermore, another object of the present invention is to provide a communication type bifurcation line fault automatic detection system.

Therefore, the communication type bifurcation line fault automatic detection system includes a complex bifurcation line circuit.

Each bifurcation circuit includes a first substation to an nth substation connected in series, n=2~N, wherein the kth substation is a preset normally open substation, k<N, k, N are positive Integer and k≧2, any two substations are electrically connected by a power line, and wherein the i-th sub-station is the upstream sub-station of the i+1th sub-station, and the i+1th sub-station is the downstream sub-station of the i-th sub-station Station, 1≦i<k, each substation includes a coupler electrically connected to the power line, and a terminal unit electrically connected to the coupler.

The terminal unit of each of the first to kth substations detects the driving current to determine whether there is an overcurrent, and correspondingly records a flag related to whether or not an overcurrent is present. When the terminal unit of the at least one substation records the flag of the overcurrent, the end unit of the i-th substation issues an interrogation signal having the flag, and the coupler of the i-th substation couples the interrogation signal to the power line to transmit To the i+1th stop.

The terminal unit of the i+1th substation determines whether the flag from the i-th substation and the flag of the i+1th substation are the same, to determine whether a fault point occurs in the i-th substation and the first If the flag is not the same, the terminal unit of the i+1th station determines that the fault point occurs between the flag of the i-th substation and the i+1th substation.

The effect of the invention lies in: each minute of each bifurcation circuit The station performs the detection of the fault point autonomously and automatically, and then achieves the operation of isolation and re-operation.

1‧‧‧load

45‧‧‧Detection unit

2‧‧‧Power line

46‧‧‧ Coupler

3‧‧‧Difference line circuit

5‧‧‧Substation feeder terminal module

32‧‧‧kth sub-station (normally open sub-station)

6‧‧‧ feeder main unit

33‧‧‧ Coupler

A01~H6‧‧‧Dual line fault point automatic detection step

34‧‧‧End unit

35‧‧‧ switch

36‧‧‧ first substation

4‧‧‧ four-way switch unit

37‧‧‧Second sub-station

41‧‧‧ switch

38‧‧‧ third substation

42‧‧‧First circuit breaker

39‧‧‧ fourth substation

43‧‧‧Second circuit breaker

F1‧‧‧ fault point

44‧‧‧Electrical protection

Other features and effects of the present invention will be apparent from the embodiments of the present invention. FIG. 1 is a circuit diagram illustrating a communication bifurcation fault automatic detection system of the present invention; FIG. 2 is a The circuit diagram illustrates a bifurcation circuit of the communication bifurcation fault automatic detection system; FIG. 3 is a flow chart illustrating a first embodiment of the communication bifurcation fault automatic detection method of the present invention; Flowchart, a step (C) of the first embodiment is illustrated; FIG. 5 is a flow chart illustrating a step (E) of the first embodiment; FIG. 6 is a flowchart illustrating the first embodiment. a step (F); FIG. 7 is a flowchart illustrating a step (G) of the first embodiment; FIG. 8A to FIG. 8D are schematic diagrams of a circuit, and FIG. 3 illustrates the first embodiment; A flow chart illustrating a second embodiment of the method for automatically detecting faults in a communication type divergence line according to the present invention.

Before the present invention is described in detail, it should be noted that in the following description, similar elements are denoted by the same reference numerals.

Referring to FIG. 1, the communication type differential line fault automatic detection of the present invention The system is adapted to transmit a plurality of driving currents to a plurality of loads 1 respectively, including a plurality of branch line circuits 3, a plurality of four-way switch units 4, and a feeder terminal terminal module 5 (FRTU), and a Feeder main unit 6.

Referring to FIG. 2, each bifurcation circuit 3 is electrically connected to a plurality of loads 1, and includes a first substation to an nth substation, n=2~N, wherein the kth substation 32 is a preset Normally open substation, k<N, k, N are positive integers and k≧2, and any two substations are electrically connected by a power line 2, and according to the current direction, the i-th sub-station is the i+1th The upstream substation of the station, the i+1th substation is the downstream substation of the i-th substation, 1≦i<k, each substation includes a coupler 33 electrically connected to the power line 2, and an electrical connection The end unit 34 of the coupler 33. The terminal unit 34 of each substation has a switch 35, and controls the corresponding switch 35 to switch between conduction and non-conduction, and the switch 35 of the k-th sub-station 32 is preset non-conducting, the k-th sub-station 32 The switch 35 of the upstream (k-1) substations is preset to be turned on.

In detail, each coupler 33 is a signal coupler of the medium voltage circuit as a signal transmission interface using Narrow-band Power Line Carrier (NPLC) communication, and each terminal unit 34 is An intelligent Lateral Terminal Unit (iLTU), and each terminal unit 34 stores a route topology for recording current directions to learn the corresponding upstream and downstream substations.

Each of the four-way switch unit 4 is electrically connected to the corresponding two-difference line circuit 3 via two power lines 2, and includes two serially connected switches 41, respectively a first circuit breaker 42 of the bifurcation circuit 3 corresponding to the electrical connection, a second circuit breaker 43, a protection circuit 44 electrically connecting the first circuit breaker 42 and the second circuit breaker 43, and an electrical connection The first circuit breaker 42 and the detecting unit 45 of the second circuit breaker 43 and a coupler 46 electrically connected to the detecting unit 45. The detecting unit 45 controls the first circuit breaker 42 and the second circuit breaker 43 to switch between conduction and non-conduction, and is implemented by an intelligent feeder terminal unit (iFTU). It should be noted that both ends of each of the branch line circuits 3 are electrically connected to the corresponding four-way switch unit 4 via the power line 2, and each of the branch line circuits 3 can be electrically connected to the first circuit breaker 42 and The second circuit breaker 43 is one of the two, but this is easily changed by those skilled in the art and will not be described again. For the sake of convenience, the first circuit breaker 42 will be described in this example.

Each substation feeder end module 5 is connected to the detecting unit 45 of the four-way switch unit 4 through fiber optic communication to read the current current level and the switch state of the four-way switch unit 4, and report back to the feeder main device. 6 learned.

Referring to FIG. 3, a first embodiment of the communication bifurcation fault automatic detection method of the present invention is performed by the communication bifurcation fault automatic detection system, and includes the following steps. It should be noted that the following steps apply regardless of the substation located to the left or right of the kth substation 32.

First, in step A01, the protection switch 44 detects the drive current of the power line 2 to determine whether there is an overcurrent; if not, repeats this step, and if so, proceeds to step A02.

Next, in step A02, the protection switch 44 is controlled. The first circuit breaker 42 should be non-conducting.

Next, in step A, the terminal unit 34 of each of the first to kth substations 32 detects the driving current to determine whether there is an overcurrent, and correspondingly records whether an overcurrent is associated. The flag, when the terminal unit 34 of the at least one of the first to kth substations 32 records the flag of the overcurrent, proceeds to step B.

Next, in step B, the end unit 34 of the i-th substation issues an interrogation signal having the flag, and the coupler 33 of the i-th substation couples the interrogation signal to the power line 2 for transmission via the power line 2. To the i+1th substation, in this example, the initial value of i is 1.

Referring to FIG. 4, next, in step C, the terminal unit 34 of the i+1th substation determines whether a fault point occurs according to the flag from the i-th substation and the flag of the i+1 substation. At the i-th substation and the i+1th substation. And include the following sub-steps.

In step C1, the terminal unit 34 of the i+1th substation receives the interrogation signal, and determines whether the flag of the i-th substation and the flag of the i+1th substation are the same according to the flag of the interrogation signal. .

In step C2, when the result of the determination in step C1 is the same, the i+1th substation determines that the fault point does not occur at the i-th substation and the i+1th substation, and proceeds to step D.

In step C3, when the result of the determination in step C1 is different, the terminal unit 34 of the i+1th station determines that the fault point occurs in the i-th substation and the i+1th substation, and proceeds to step E.

Next, in step D, increase the value of i by 1, and return to the step B to continue to judge the location of the fault point, it is added here that the return to step B via steps C, D means that the substation being inquired will inquire about its corresponding downstream substation.

Referring to FIG. 5, in step E, when it is determined that the fault point is located in the i-th substation and the i-th sub-station, the end-end unit 34 of the i+1th sub-station sends an answer signal via the power line 2 to The i-th substation, and the two stations stop transmitting the drive current to the corresponding load 1 to isolate the fault point. Step E includes the following sub-steps.

In step E1, the terminal unit 34 of the (i+1)th station determines whether it is the kth station 32 (normally open point station) to determine whether to make the corresponding switch 35 non-conductive. If it is judged that the kth substation 32, it proceeds directly to step E3.

In step E2, if the step E1 determines that the kth substation 32 is not the switch, the switch 35 corresponding to the end unit 34 of the i+1th substation is not turned on, and an indication corresponding to the kth substation 32 is issued. The turn-on signal of the switch 35 is turned on, and proceeds to step E3.

In step E3, the terminal unit 34 of the (i+1)th station sends an answer signal indicating that the recorded flag is different from the recorded flag of the i-th station.

In step E4, the coupler 33 of the i+1th substation couples the answer signal and the on signal to the power line 2 for transmission.

In step E5, the terminal unit 34 of the i-th sub-station receives the answer signal, and controls the corresponding switch 35 to be non-conducting according to the answer signal.

In this way, the upstream substation and the downstream substation adjacent to the fault point, that is, the transmission of the fault detection and the power failure isolation by means of narrowband power line carrier communication, the substation stops supplying power to the corresponding load 1 In order to avoid the occurrence of related short-circuit accidents, and at this time, the power detector can perform maintenance control on the fault point.

Referring to FIG. 6, then, in step F, an operation to reduce the scope of the accident power outage is implemented, including the following sub-steps.

In step F1, the terminal unit 34 of the kth substation 32 (normally open substation) receives the on signal, and accordingly controls the corresponding switch 35 to be turned on.

In step F2, the terminal unit 34 of the i-th sub-station sends a notification signal to instruct the detecting unit 45 to control the first circuit breaker 42 to be turned on.

In step F3, the coupler 33 of the i-th substation couples the notification signal to the power line 2 for transmission.

In step F4, the detecting unit 45 receives the notification signal, and controls the first circuit breaker 42 to be turned on according to the notification signal.

Referring to FIG. 7, then, in step G, an operation to repair the fault point and re-power is implemented, including the following sub-steps.

In step G1, the feeder main unit 6 determines whether the fault point has returned to normal, and if not, repeats this step, and if so, proceeds to step G2.

In step G2, the body line master device 6 controls the detecting unit 45 to send a first reply signal via the substation feeder end unit 34 to indicate that the i-th sub-station and the i-th sub-station respectively correspond to each other. Switch 35 reply Into conduct.

In step G3, the coupler 46 of the branch line circuit 3 corresponding to the four-way switch unit 4 couples the first reply signal to the power line 2 for transmission.

In step G4, the i-th sub-station and the end-end unit 34 of the i+1th sub-station respectively receive the first reply signal, and control the corresponding switch 35 to be turned on.

In step G5, the i-th sub-station and the end-end unit 34 of the i+1th sub-station respectively send a return signal to report that the corresponding switch 35 has been restored to be turned on to the detecting unit 45.

In step G6, the i-th substation and the coupler 33 of the i+1th substation couple the return signal to the power line 2 for transmission.

In step G7, the detecting unit 45 receives the reward signal and sends a second reply signal to indicate that the kth substation 32 (normally open substation) returns the corresponding switch 35 to be non-conductive.

In step G8, the coupler 46 of the branch line circuit 3 corresponding to the four-way switch unit 4 couples the second reply signal to the power line 2 for transmission.

In step G9, the terminal unit 34 of the kth substation 32 receives the second reply signal, and accordingly controls the corresponding switch 35 to be non-conductive.

In this way, when the fault of the branch line circuit 3 is eliminated, the detecting unit 45 also restores the power supply to the corresponding load 1 by means of narrow-band power line carrier communication.

Referring to FIGS. 8A to 8D, the first substation 36, the second substation 37, the third substation 38, and the fourth substation 39, which are mutually upstream and downstream, are illustrated as an example, wherein current is from the first Substation 36 flows to the fourth substation 39, the first substation 36 is the upstream substation of the second substation 37, the second substation 37 is the downstream substation of the first substation 36, and the kth substation 32 (normally open point) The substation is the fourth substation 39, and a fault point f1 is located between the second substation 37 and the third substation 38. Further, the following describes the fault, detection, isolation and complex of the present invention. Electrical operation.

First, the protection power detects the overcurrent of the corresponding branch line circuit 3, that is, controls the first circuit breaker 42 to be non-conductive, as shown in FIG. 8A.

Then, according to the current flow direction and the position of the fault point f1, the first substation 36 and the second substation 37 record the flag of the overcurrent, and the two substations transmit the narrow frequency by recording the flag of the overcurrent. Power line carrier communication transmission, respectively, to the downstream substation to ask if there is an overcurrent flag. The second substation 37 answers the first substation 36 to record the flag of the overcurrent, and the first substation 36 knows that there is no need to trip, and knows that the fault point is not at the first substation and 36 The second sub-station 37, then the second sub-station 37 then interrogates the third sub-station 38. The third substation 38 records the flag without overcurrent and knows that it is not the same as the flag of the second substation 37, even if the corresponding switch is not turned on, and answers the second substation 37 to inform the user The corresponding switch is not turned on, as shown in FIG. 8B, at this time, the operation of detecting the fault point and powering off the isolation is achieved.

Then, when the terminal unit of the second substation 37 makes the corresponding switch non-conducting, that is, the detecting unit is notified, the detecting unit controls the first circuit breaker 42 to be turned on, and the end of the third sub-station 38 Since the unit is not a normally open substation, the fourth substation 39 is instructed to be turned on, as shown in FIG. 8C. Thereby, the load around the first substation 36 and the third substation 38 is maintained to supply power to reduce the power outage range of the accident.

Finally, when the power detecting personnel completes the repair and eliminates the fault of the corresponding branch line circuit 3, the feeder main device controls the second substation 37 and the third substation 38 to be turned on even if the detecting unit controls the second substation 37 and the third substation 38. The quartile 39 returns to be non-conducting as shown in Figure 8D.

Referring to FIG. 9, a second embodiment of the method for automatically detecting faults in the communication type bifurcation line of the present invention is similar to the first embodiment, except that steps H1 to H6 after step B are performed.

In step H1, the terminal unit 34 of the i-th station and the terminal unit 34 of the (i+1)th station are counted down for a predetermined time.

Step H2, the terminal unit 34 of the (i+1)th station determines whether to make the corresponding switch 35 non-conductive according to whether an inquiry signal from the i-th sub-station is received at the predetermined time, if the i-th The end unit 34 of the 1st station receives the inquiry signal, that is, proceeds to step C.

Step H3, when the i+1th station does not receive the inquiry signal at the predetermined time, the i+1th station makes the corresponding switch 35 non-conductive.

In step H4, the i-th substation determines whether the corresponding switch 35 is non-conducting according to whether an answer signal from the i+1th substation is received at the predetermined time.

In step H5, the ith station does not receive the answer signal at the predetermined time, and the ith station makes the corresponding switch 35 non-conductive.

In step H6, the value of i is incremented by 1, and the process returns to step B. in This supplementary explanation is that returning to step B via steps H1 to H6 means that the substation being inquired at this time will inquire about its corresponding downstream substation.

Thus, when the couplers 33 fail and cannot be transmitted by the narrow-band power line carrier communication, the switches 35 corresponding to the sub-stations are sequentially turned off until the k-th sub-station 32 (normally open points) Station) so far.

Continuing from the previous example, the protection circuit detects an overcurrent, and likewise controls the first circuit breaker 42 to be non-conducting, and the first substation 36 and the second substation 37 also record the overcurrent flag. Due to the failure of the couplers, the interrogation signals sent by the substations cannot be received by the downstream substation, and the downstream substation cannot answer the upstream substation, so for example, the predetermined time is one minute. The three-station 38 does not receive an inquiry signal from the second sub-station 37 after one minute, and the second sub-station 37 does not receive an answer signal from the third sub-station 38 after one minute, the two substations The terminal unit controls the corresponding switch to be non-conducting, and repeats this step until the fourth substation 39 (normally open substation).

It should be added here that when the kth substation 32 (the normally open substation) needs to move, the detecting unit 45 can also control the kth substation 32 by using the narrowband power line carrier communication transmission. The corresponding switch 35 is turned on, and controls the switch 35 corresponding to any substation to be non-conducting as the new k-th sub-station. At the same time, the detecting unit 45 transmits a new routing topology to each of the substations to inform the upstream and downstream sub-station relationships and the frequent opening point sub-station. Therefore, the flexibility of the automatic detection method for the communication type bifurcation line of the present invention can be increased.

In summary, the communication type differential line fault automatic detection of the present invention The system is provided with the couplers 33 and 46 correspondingly at each sub-station and each of the four-way switch units 4 of each bifurcation circuit 3, and directly communicates with the narrow-frequency power line carrier to directly utilize the existing power line 2 The signal is transmitted, and all the substations of each bifurcation circuit 3 communicate with each other in a mutual question and answer manner, and each of the bifurcation circuit 3 and each of the four switch units 4 directly and automatically performs the fault, detection, and Isolation and re-powering can indeed achieve the object of the present invention.

The above is only the preferred embodiment of the present invention, and the scope of the present invention is not limited thereto, that is, the simple equivalent changes and modifications made by the patent application scope and patent specification content of the present invention, All remain within the scope of the invention patent.

1‧‧‧load

2‧‧‧Power line

3‧‧‧Difference line circuit

32‧‧‧kth sub-station (normally open sub-station)

4‧‧‧ four-way switch unit

41‧‧‧ switch

42‧‧‧First circuit breaker

43‧‧‧Second circuit breaker

44‧‧‧Electrical protection

45‧‧‧Detection unit

46‧‧‧ Coupler

5‧‧‧Substation feeder terminal module

6‧‧‧ feeder main unit

Claims (9)

A communication type bifurcation line fault automatic detection method is implemented by a communication bifurcation line fault automatic detection system, and the communication bifurcation line fault automatic detection system is suitable for transmitting a plurality of driving currents, and the communication type bifurcation line fault automatic detection The measurement system includes a plurality of bifurcation lines, each bifurcation circuit includes a first substation to an nth substation connected in series, n=2~N, wherein the kth substation is a preset normally open substation, k<N, k, N are positive integers and k≧2, and any two substations are electrically connected by a power line, and wherein the i-th sub-station is the upstream sub-station of the i+1th substation, the i+1th point The station is the downstream substation of the i-th substation, 1≦i<k, and the automatic detection method of the communication bifurcation line fault includes: (A) each substation detection of the first substation to the kth substation The driving current is used to determine whether there is an overcurrent, and correspondingly records a flag related to whether or not the current is over, and when at least one of the first sub-station to the k-th sub-station records the flag of the over-current, the process proceeds to the step (B); (B) the ith substation sends an inquiry signal having the flag to the i+1th substation via the power line; (C) the i+1th substation according to a flag of the i-th substation and a flag of the i+1 substation to determine whether a fault point occurs at the i-th substation and the i+1th substation; and (D) when step (C) is Otherwise, increase the value of i by one and return to step (B). The method for automatically detecting a fault of a communication line as described in claim 1, wherein the step (C) comprises: (C1) The i+1th substation determines whether the flag of the i-th substation and the flag of the i+1th substation are the same, (C2) when the judgment result of the step (C1) is YES, the i+th 1 substation judges that the fault point does not occur at the i-th substation and the i+1th substation, and proceeds to step (D), (C3) when the step (C1) determines that the result is no, the i+th The terminal unit of the 1st station determines that the fault point occurs at the i-th substation and the i+1th substation. For the communication type bifurcation line fault automatic detection method described in claim 2, each substation has a corresponding switch, and is controlled to switch between conduction and non-conduction, and the switch corresponding to the k-th sub-station is pre- If the switch is not turned on, the switches corresponding to the (k-1) substations upstream of the kth substation are all preset, and the communication bifurcation fault automatic detection method further includes the step after the step (C3) ( E1) to (E5): (E1) The i+1th substation judges whether it is the kth substation to decide whether to make the corresponding switch non-conducting; (E2) if the judgment result of the step (E1) is no And the i+1th substation causes the corresponding switch to be non-conducting, and sends a conduction signal indicating that the switch corresponding to the kth substation is turned on; (E3) the i+1th substation sends an indication The recorded signal is different from the recorded flag of the i-th sub-station; (E4) the conduction signal and the answer signal are respectively transmitted through the power line to the k-th sub-station and the i-th sub-station; E5) The i-th substation makes the corresponding opening according to the answer signal Guan Cheng does not conduct. The communication type bifurcation line fault automatic detection method according to claim 3, wherein the communication bifurcation line fault automatic detection system further comprises a plurality of four-way switch units, and each of the four-way switch units is electrically connected via two power lines. a second branch line circuit, comprising: a first circuit breaker corresponding to the branch line circuit corresponding to the electrical connection, and a detecting unit electrically connected to the first circuit breaker, the detecting unit controlling the first circuit breaker to be turned on The non-conducting switching, and the communication bifurcation fault automatic detection method further includes the steps (A01) and (A02) before the step (A): (A01) the four-way switching unit detects the driving current to determine whether If there is an overcurrent; and (A02) if the result of the step (A01) is YES, the first circuit breaker corresponding to the four-way switch unit control is non-conducting, and further includes the step (F1) after the step (E) To (F4): (F1) the kth substation receives the on signal to control the corresponding switch to be turned on; (F2) the i th station sends a notification signal to instruct the detecting unit to control the a circuit breaker is turned on; (F3) the notification signal is sent to the detective via the power line Units; and (F4) of the communications unit receives the detection signal, and controlling the first circuit breaker to be turned. For the communication type bifurcation fault automatic detection method described in claim 1, each substation has a corresponding switch, and is controlled to switch between conduction and non-conduction, and the switch corresponding to the k-th sub-station is pre- Set no, this The switches corresponding to the (k-1) substations upstream of the kth substation are all preset. The communication bifurcation fault automatic detection method further includes the steps (H1) to (H6) after the step (B). (H1) the i-th substation and the i+1th substation respectively count down for a predetermined time; (H2) whether the i+1th substation receives the e-substation from the i-th substation at the predetermined time Querying a signal to determine whether to make the corresponding switch non-conductive, and when the i+1th station receives the inquiry signal at the predetermined time, proceeds to step (C); (H3) when the i+th If the first station does not receive the inquiry signal at the predetermined time, the i+1th station makes the corresponding switch non-conducting; (H4) whether the i-th station receives one from the predetermined time. The answer signal of the i+1th substation determines whether the corresponding switch is non-conducting; (H5) the i-th sub-station does not receive the answer signal at the predetermined time, and the i-th sub-station makes corresponding The switch is rendered non-conductive; and (H6) increments the value of i by one and returns to step (B). A communication type bifurcation fault automatic detection system is suitable for transmitting a plurality of driving currents, comprising: a complex bifurcation circuit, each bifurcation circuit comprising a first substation to an nth substation connected in series, n=2~N , wherein the kth substation is a preset normally open substation, k<N, k, N is a positive integer and k≧2, and any two substations are electrically connected by a power line, and wherein the i th The station is the upstream substation of the i+1th substation, and the i+1th station is the downstream substation of the i-th substation, 1 ≦i<k, each substation includes a coupler electrically connected to the power line, and a terminal unit electrically connected to the coupler, the end unit of each of the first to kth substations Measuring the driving current to determine whether there is an overcurrent, and correspondingly recording a flag related to whether or not the current is over, when the terminal unit of the at least one substation records the flag of the overcurrent, the terminal unit of the i th substation sends out An interrogation signal having the flag, the coupler of the i-th substation coupling the interrogation signal to the power line for transmission to the (i+1)th station, and the end unit of the i+1th station judges from the i-th sub-station Whether the flag of the station and the flag of the i+1th substation are the same, to determine whether a fault point occurs in the i-th substation and the i+1th substation, and if the flag is not the same, the i-th The terminal unit of the +1 substation determines that the fault point occurs between the flag of the i-th substation and the i+1th substation. The communication type bifurcation fault automatic detection system according to claim 6, wherein the end unit of each substation has a switch, and controls the corresponding switch to switch between conduction and non-conduction, and the kth substation The switch is preset to be non-conducting, and the (k-1) sub-station upstream of the kth substation is preset to be turned on, when the flag of the i-th substation and the flag of the i+1th substation are not When the same, the terminal unit of the i+1th sub-station further determines whether it is the k-th sub-station to determine whether the corresponding switch of the control is switched to be non-conducting, and if it is judged that the k-th sub-station is not, the i+1th sub-score The switch corresponding to the end unit control of the station is non-conducting, and an indication is issued to the kth substation And a corresponding signal indicating that the switch is turned on, and an answer signal indicating that the recorded flag is different from the flag recorded by the terminal unit of the i-th substation, and the coupler of the i+1th substation couples the answer signal And transmitting the conduction signal to the power line, and the terminal unit of the i-th sub-station receives the response signal, and controls the corresponding switch to be non-conducting according to the response signal. The communication type bifurcation line fault automatic detection system according to claim 7, further comprising: a plurality of four-way switch units, each of the four-way switch units electrically connecting the corresponding two bifurcation line circuits via the two power lines, and including one electric a first circuit breaker connected to the branch line circuit and a detecting unit electrically connected to the first circuit breaker, and the detecting unit controls the first circuit breaker to switch between conducting and non-conducting, the four way The switch unit detects the drive current to determine whether there is an overcurrent, and if it is determined to be an overcurrent, the first circuit breaker corresponding to the four-way switch unit control is non-conductive, when the fault point occurs, and the i-th point When the station and the terminal unit of the i+1th substation respectively control the corresponding switch to switch to non-conduction, the end unit of the kth substation receives the conduction signal to control the corresponding switch to be turned on, the i-th The terminal unit of the substation sends a notification signal to indicate that the detecting unit turns on the first circuit breaker, the coupler of the i-th sub-station couples the notification signal to the power line transmission, and the detecting unit receives The notification signal and controlling the first circuit breaker to be turned on. The communication type bifurcation fault automatic detection system according to claim 6, wherein the end unit of each substation has a switch, and controls the corresponding switch to switch between conduction and non-conduction, and the kth substation The switch is preset to be non-conducting, and the switches of the (k-1) substations upstream of the kth substation are preset to be turned on, and the end units of the i th substation and the i+1th substation are counted down one by one. a predetermined time, the end unit of the i+1th substation determines whether to make the corresponding switch non-conducting according to whether an inquiry signal from the i-th sub-station is received at the predetermined time, and when the inquiry is not received a signal, the switch corresponding to the end unit control of the i+1th substation is non-conducting, and the end unit of the i-th substation receives an answer signal from the i+1th substation according to the predetermined time. In order to determine whether the corresponding switch is non-conducting, and when the answer signal is not received, the i-th substation makes the corresponding switch non-conducting, and increases the value of i by 1, and the i-th substation continues to issue the The inquiry signal asks for the i+1th station.