A demarcation switch function detection circuit and detection method thereof

Abstract

The present invention relates to the technical field of power grid equipment testing instruments, and its purpose is to provide a boundary switch function detection circuit and a detection method thereof. The present invention discloses a boundary switch function detection circuit, including a large current generator, a PLC, a fifth resistor, a zeroth resistor, a first resistor, a zeroth contactor, a first contactor, a fifth contactor, a sixth contactor, an eighth contactor, a tenth contactor and a twelfth signal relay. The present invention also discloses a detection method according to the above-mentioned boundary switch function detection circuit, including a switch function detection method. The present invention is a relatively simple, inexpensive, portable and easy-to-operate device, which replaces expensive relay protection testers, does not require more frequent wiring changes, can be relatively close to the parameters of the working conditions during distribution network failures, and can perform a relatively comprehensive detection of the boundary switch protection function.

Description

Technical Field

[0001] The invention relates to the technical field of power grid equipment testing instruments, and in particular to a boundary switch function detection circuit and a detection method thereof. Background Art

[0002] The boundary switch is a device used for line protection of branch lines and terminal users. It has the function of automatic isolation of overhead line user faults and can automatically cut off the grounding fault within the user boundary. Among them, the boundary switch using a circuit breaker as the main body can automatically cut off the interphase short-circuit fault within the user boundary; the boundary switch using a load switch as the main body can achieve the isolation of the interphase short-circuit fault within the user boundary by cooperating with the upper-level circuit breaker to avoid expanding the power outage scope of the medium-voltage distribution network and affecting the normal power consumption of other users.

[0003] At present, most manufacturers lack technical strength and have a small production scale. They mostly produce the switch body by themselves and purchase controllers to form user boundary switches, which are prone to problems in function matching. In order to ensure the safe application of the boundary switch, it is necessary to perform functional testing before it leaves the factory. In the prior art, when performing functional testing on the boundary switch, manufacturers generally use a large current generator for testing. This method is very different from the line fault conditions encountered during switch operation, and the detection is too one-sided. When it comes to testing the protection function of the user boundary switch in engineering applications, professional testing unit personnel generally use relay protection testers or large current generators for testing. There are various detection methods, but basically there is an incomplete detection content, and it is easy to have a problem of large differences between the test conditions and the line fault conditions. Summary of the invention

[0004] In order to solve the above problems existing in the prior art, the present invention provides a boundary switch function detection circuit and a detection method thereof.

[0005] The technical solution adopted by the present invention is:

[0006] A demarcation switch function detection circuit includes a high current generator, a PLC, a fifth resistor, a zeroth resistor, a first resistor, a zeroth contactor, a first contactor, a fifth contactor, a sixth contactor, an eighth contactor, a tenth contactor and a twelfth signal relay;

[0007] The power connection pole of the PLC is connected to the two ends of the primary winding of the large current generator; the zeroth signal output pole of the PLC is connected to the same-name end of the primary winding of the large current generator through the coil of the zeroth contactor, the first signal output pole of the PLC is connected to the same-name end of the primary winding of the large current generator through the coil of the first contactor, the fifth signal output pole of the PLC is connected to the opposite-name end of the primary winding of the large current generator through the coil of the fifth contactor, the sixth signal output pole of the PLC is connected to the opposite-name end of the primary winding of the large current generator through the coil of the sixth contactor, the eighth signal output pole of the PLC is connected to the opposite-name end of the primary winding of the large current generator through the coil of the eighth contactor, the tenth signal output pole of the PLC is connected to the opposite-name end of the primary winding of the large current generator through the coil of the tenth contactor, and the eighth signal input pole of the PLC is connected to the common negative pole of the PLC through the contact of the twelfth signal relay;

[0008] The two ends of the primary winding of the large current generator are respectively connected to the two poles of the power supply; the same-name end of the secondary winding of the large current generator is connected to the first detection point of phase A through the fifth resistor and the contact of the fifth contactor in sequence, the contacts of the zeroth resistor and the zeroth contactor are connected in series to form a first branch, the contacts of the first resistor and the first contactor are connected in series to form a second branch, and the first branch and the second branch are both connected in parallel with the fifth resistor; the junction point of the fifth resistor and the contact of the fifth contactor is connected to the first detection point of phase B through the contact of the sixth contactor, the junction point of the fifth resistor and the contact of the fifth contactor is connected to the first detection point of phase C through the contact of the eighth contactor, and the junction point of the fifth resistor and the contact of the fifth contactor is also connected to the live wire of the power supply; the opposite-name end of the secondary winding of the large current generator is respectively connected to the second detection point of phase A, the second detection point of phase B and the second detection point of phase C through the contact of the tenth contactor, the opposite-name end of the secondary winding of the large current generator is connected to the junction point of the contacts of the fifth resistor and the fifth contactor through the coil of the twelfth signal relay, and the opposite-name end of the secondary winding of the large current generator is also connected to the neutral line of the power supply;

[0009] The two ends of the primary winding of the large current generator are connected to the power supply pole of the boundary switch.

[0010] Preferably, the boundary switch function detection circuit further includes a fourth resistor, a fourth contactor, a seventh contactor and a ninth contactor;

[0011] The fourth signal output pole of the PLC is connected to the opposite end of the primary winding of the large current generator through the coil of the fourth contactor, the seventh signal output pole of the PLC is connected to the opposite end of the primary winding of the large current generator through the coil of the seventh contactor, and the ninth signal output pole of the PLC is connected to the opposite end of the primary winding of the large current generator through the coil of the ninth contactor;

[0012] The fourth resistor and the contacts of the fourth contactor are connected in series to form a third branch, and the third branch is connected in parallel with the fifth resistor; the opposite-name end of the secondary winding of the large current generator is connected to the first detection point of the B phase through the contacts of the seventh contactor, and the opposite-name end of the secondary winding of the large current generator is connected to the first detection point of the C phase through the contacts of the ninth contactor.

[0013] Further preferably, the boundary switch function detection circuit further includes a third resistor, a third contactor and an eleventh contactor;

[0014] The third signal output pole of the PLC is connected to the opposite end of the primary winding of the large current generator through the coil of the third contactor, and the eleventh signal output pole of the PLC is connected to the opposite end of the primary winding of the large current generator through the coil of the eleventh contactor;

[0015] The third resistor and the contact of the third contactor are connected in series to form a fourth branch, and the fourth branch is connected in parallel with the fifth resistor;

[0016] One end of the contact of the eleventh contactor is connected to the opposite end of the primary winding of the large current generator, and the other end of the contact of the eleventh contactor is connected to the power output pole of the boundary switch.

[0017] Further preferably, the boundary switch function detection circuit also includes a short-circuit detection switch, an increased zero-sequence current detection switch, a current correction switch and a fault indicator detection switch; the second signal input pole of the PLC is connected to the common negative pole of the PLC through the short-circuit detection switch, the third signal input pole of the PLC is connected to the common negative pole of the PLC through the increased zero-sequence current detection switch, the fourth signal input pole of the PLC is connected to the common negative pole of the PLC through the current correction switch, and the fifth signal input pole of the PLC is connected to the common negative pole of the PLC through the fault indicator detection switch.

[0018] Preferably, the boundary switch function detection circuit also includes a start switch and a stop switch; the zeroth signal input pole of the PLC is connected to the common negative pole of the PLC through the start switch, and the first signal input pole of the PLC is connected to the common negative pole of the PLC through the stop switch.

[0019] Preferably, the boundary switch function detection circuit also includes a leakage switch, a first air switch and a second air switch. The leakage switch is arranged between the primary side winding of the large current generator and the power supply, the first air switch is arranged between the primary side winding of the large current generator and the power connection pole of the PLC, and the second air switch is arranged between the primary side winding of the large current generator and the power connection pole of the boundary switch.

[0020] Preferably, the power supply is a single-phase industrial frequency sinusoidal AC power supply.

[0021] A detection method according to the above-mentioned demarcation switch function detection circuit includes a switch function detection method, and the switch function detection method includes the following steps:

[0022] Conduct ground fault zero-sequence overcurrent setting lower limit detection;

[0023] Conduct ground fault zero-sequence overcurrent setting upper limit detection;

[0024] Conduct zero-sequence overcurrent detection (two-phase flow, simulating phase loss condition) and phase-to-phase short-circuit overcurrent rate determination value lower limit detection to see if three-phase unbalanced load generates zero-sequence overcurrent detection (two-phase flow, simulating phase loss condition)

[0025] Conduct zero-sequence overcurrent detection to see if the three-phase unbalanced load generates zero-sequence overcurrent (one large and two small, three-phase current flow, simulating the unbalanced three-phase power consumption condition);

[0026] Perform the upper limit detection of the phase-to-phase short-circuit overcurrent rate determination value (including the absence of power on the power supply side at the moment of short circuit, simulating the substation switch tripping condition after a fault).

[0027] Preferably, the detection method further comprises a fault indicator detection method.

[0028] The beneficial effects of the present invention are mainly embodied in:

[0029] 1. The device of the present invention has a relatively simple structure, is cheap, portable and easy to operate, and can replace expensive relay protection testers. It does not require frequent wiring changes, can be closer to the parameters of the operating conditions during distribution network failures, and can perform a relatively comprehensive test on the protection function of the boundary switch.

[0030] 2. The present invention adopts automatic detection according to the process through PLC. There is no need to adjust various detection parameters or change various wirings during detection. The detection parameters and wiring methods are automatically converted by the device. Therefore, a normal switch detection process takes a short time. The detection speed is more than 10 times faster than the detection devices such as relay protection instruments and large current generators in the prior art.

[0031] 3. The present invention adds a detection item of whether the three-phase unbalanced load generates zero-sequence overcurrent to the detection of the boundary switch, which is rarely considered in other detection methods in the past. It can effectively check whether the synthetic zero-sequence algorithm using the synthetic zero-sequence current switch is correct.

[0032] 4. The present invention can be used to simply judge the quality of the fault indicator, achieving the effect of one machine with multiple uses. It can solve the needs of grassroots personnel engaged in power operation and maintenance and construction for a fault indicator detection instrument, making it convenient to carry out work. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is a circuit schematic diagram of Embodiment 1;

[0034] Figure 2 is a circuit schematic diagram of embodiment 1 and a boundary switch when performing switch function detection;

[0035] Figure 3 It is a circuit schematic diagram of Example 1 and the boundary switch when performing fault indicator detection. DETAILED DESCRIPTION

[0036] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments. It should be noted that although the description of these embodiments is used to help understand the present invention, it does not constitute a limitation of the present invention. The specific structures and functional details disclosed herein are only used to describe the exemplary embodiments of the present invention. However, the present invention can be embodied in many alternative forms, and it should not be understood that the present invention is limited to the embodiments set forth herein.

[0037] It should be understood and also noted that in some alternative embodiments, the functions / actions that appear may be different from the order in which the figures appear. For example, depending on the functions / actions involved, two figures shown in succession may actually be performed substantially concurrently, or may sometimes be performed in the reverse order.

[0038] It should be understood that in the following description, specific details are provided to facilitate a complete understanding of the example embodiments. However, it should be understood by those of ordinary skill in the art that the example embodiments can be implemented without these specific details. For example, the system can be shown in a block diagram to avoid obscuring the example with unnecessary details. In other examples, well-known processes, structures, and techniques may not be shown in unnecessary detail to avoid obscuring the example embodiments.

[0039] Embodiment 1:

[0040] This embodiment provides a boundary switch function detection circuit, such as Figure 1 As shown, it includes a large current generator T, a PLC, a fifth resistor R5, a zeroth resistor R0, a first resistor R1, a zeroth contactor, a first contactor, a fifth contactor, a sixth contactor, an eighth contactor, a tenth contactor and a twelfth signal relay.

[0041] In this embodiment, the PLC is a PLC manufactured by Xiamen Shuangyuan Technology Co., Ltd., which is an 8-input 16-output programmable controller, and the 16 outputs of the PLC are all implemented by 5A relays. It should be understood that the PLC can also be a PLC with a model number of FP-2020MR manufactured by Loudi Jiansi Control Co., Ltd. or a PLC with a model number of MM-30MR-4MT-700-FX-A manufactured by Shenzhen Zhongda Youkong Technology Co., Ltd.

[0042] The rated capacity of the zero contactor, the first contactor, the second contactor, the third contactor, the tenth contactor and the eleventh contactor are all 25A; the rated capacity of the fourth contactor, the fifth contactor, the sixth contactor, the seventh contactor, the eighth contactor and the ninth contactor are all 2×63A; the working voltage of the twelfth signal relay is AC 12V.

[0043] The power connection pole of the PLC is connected to the two ends of the primary winding of the large current generator T; the VCC foot of the PLC is connected to the same-name end of the primary winding of the large current generator T, and the GND foot of the PLC is connected to the opposite-name end of the primary winding of the large current generator T; the zeroth signal output pole of the PLC is connected to the same-name end of the primary winding of the large current generator T through the coil of the zeroth contactor, the first signal output pole of the PLC is connected to the same-name end of the primary winding of the large current generator T through the coil C01-1 of the first contactor, and the fifth signal output pole of the PLC is connected to the same-name end of the primary winding of the large current generator T through the coil C05- 1 is connected to the opposite end of the primary winding of the large current generator T, the sixth signal output pole of the PLC is connected to the opposite end of the primary winding of the large current generator T through the coil C06-1 of the sixth contactor, the eighth signal output pole of the PLC is connected to the opposite end of the primary winding of the large current generator T through the coil C08-1 of the eighth contactor, the tenth signal output pole of the PLC is connected to the opposite end of the primary winding of the large current generator T through the coil C10-1 of the tenth contactor, and the eighth signal input pole of the PLC is connected to the common negative pole of the PLC through the contact C12-2 of the twelfth signal relay;

[0044] The two ends of the primary winding of the large current generator T are respectively connected to the two poles of the power supply; the same-name end of the primary winding of the large current generator T is connected to the live wire of the power supply, and the opposite-name end of the primary winding of the large current generator T is connected to the neutral wire of the power supply; the same-name end of the secondary winding of the large current generator T is connected to the first detection point A1 of the A phase through the fifth resistor R5 and the contact C05-2 of the fifth contactor in sequence, the zeroth resistor R0 and the contact C00-2 of the zeroth contactor are connected in series to form a first branch, the first resistor R1 and the contact C01-2 of the first contactor are connected in series to form a second branch, and the first branch and the second branch are both connected in parallel with the fifth resistor R5; the junction point of the fifth resistor R5 and the contact C05-2 of the fifth contactor is connected through the contact C06 of the sixth contactor. -2 is connected to the first detection point B1 of the B phase, the junction point of the fifth resistor R5 and the contact C05-2 of the fifth contactor is connected to the first detection point C1 of the C phase through the contact C08-2 of the eighth contactor, and the junction point of the fifth resistor R5 and the contact C05-2 of the fifth contactor is also connected to the live wire of the power supply; the opposite-name end of the secondary winding of the large current generator T is respectively connected to the second detection point A2 of the A phase, the second detection point B2 of the B phase and the second detection point C2 of the C phase through the contact C10-2 of the tenth contactor, the opposite-name end of the secondary winding of the large current generator T is connected to the junction point of the fifth resistor R5 and the contact C05-2 of the fifth contactor through the coil C12-1 of the twelfth signal relay, and the opposite-name end of the secondary winding of the large current generator T is also connected to the neutral line of the power supply;

[0045] The two ends of the primary winding of the large current generator T are connected to the power supply pole of the demarcation switch; specifically, the same-name end of the primary winding of the large current generator T is connected to the power input pole of the demarcation switch, and the opposite-name end of the primary winding of the large current generator T is connected to the power output pole of the demarcation switch; specifically, Figure 2 As shown, the boundary switch includes a boundary switch controller and a switch body, wherein the boundary switch controller includes a control output circuit, an AC sampling circuit and a CPU, the switch body is electrically connected to the first detection point A1 of phase A, the first detection point B1 of phase B, the first detection point C1 of phase C, the second detection point A2 of phase A, the second detection point B2 of phase B and the second detection point C2 of phase C, the opposite end of the primary winding of the large current generator T is electrically connected to the boundary switch controller, the switch body can send the sampling signal to the CPU through the AC sampling circuit, the CPU processes the sampling signal and sends the processed sampling signal to the control output circuit, and the control output circuit can feed back the processed sampling signal to the switch body.

[0046] The A-phase first detection point A1 and the A-phase second detection point A2 are respectively connected to the two ends of the A-phase switch of the boundary switch, the B-phase first detection point B1 and the B-phase second detection point B2 are respectively connected to the two ends of the B-phase switch of the boundary switch, and the C-phase first detection point C1 and the C-phase second detection point C2 are respectively connected to the two ends of the C-phase switch of the boundary switch.

[0047] The boundary switch function detection circuit also includes a second resistor R2 and a second contactor. The second signal output pole of the PLC is connected to the opposite end of the primary winding of the large current generator T through the coil C02-1 of the second contactor. The second resistor R2 and the contact C02-2 of the second contactor are connected in series to form a fifth branch, and the fifth branch is connected in parallel with the fifth resistor R5.

[0048] Further, the boundary switch function detection circuit also includes a fourth resistor R4, a fourth contactor, a seventh contactor and a ninth contactor;

[0049] The fourth signal output pole of the PLC is connected to the opposite end of the primary winding of the large current generator T through the coil C04-1 of the fourth contactor, the seventh signal output pole of the PLC is connected to the opposite end of the primary winding of the large current generator T through the coil C07-1 of the seventh contactor, and the ninth signal output pole of the PLC is connected to the opposite end of the primary winding of the large current generator T through the coil C09-1 of the ninth contactor;

[0050] The fourth resistor R4 and the contact C04-2 of the fourth contactor are connected in series to form a third branch, and the third branch is connected in parallel with the fifth resistor R5; the opposite-name end of the secondary winding of the large current generator T is connected to the first detection point B1 of the B phase through the contact C07-2 of the seventh contactor, and the opposite-name end of the secondary winding of the large current generator T is connected to the first detection point C1 of the C phase through the contact C09-2 of the ninth contactor.

[0051] Furthermore, the boundary switch function detection circuit further includes a third resistor R3, a third contactor and an eleventh contactor;

[0052] The third signal output pole of the PLC is connected to the opposite end of the primary winding of the large current generator T through the coil C03-1 of the third contactor, and the eleventh signal output pole of the PLC is connected to the opposite end of the primary winding of the large current generator T through the coil C11-1 of the eleventh contactor;

[0053] The third resistor R3 and the contact C03-2 of the third contactor are connected in series to form a fourth branch, and the fourth branch is connected in parallel with the fifth resistor R5;

[0054] One end of the contact C11-2 of the eleventh contactor is connected to the opposite end of the primary winding of the large current generator T, and the other end of the contact C11-2 of the eleventh contactor is connected to the power output pole of the boundary switch.

[0055] Contact C00-2 of the zero contactor, contact C01-2 of the first contactor, contact C02-2 of the second contactor, contact C03-2 of the third contactor, contact C05-2 of the fifth contactor, contact C06-2 of the sixth contactor, contact C08-2 of the eighth contactor, contact C10-2 of the tenth contactor, contact C04-2 of the fourth contactor, contact C07-2 of the seventh contactor, contact C09-2 of the ninth contactor, contact C11-2 of the eleventh contactor and contact C12-2 of the twelfth signal relay are all normally open contacts.

[0056] In this embodiment, the boundary switch function detection circuit also includes a short-circuit detection switch, an increased zero-sequence current detection switch, a current correction switch and a fault indicator detection switch; the second signal input pole of the PLC is connected to the common negative pole of the PLC through the short-circuit detection switch, the third signal input pole of the PLC is connected to the common negative pole of the PLC through the increased zero-sequence current detection switch, the fourth signal input pole of the PLC is connected to the common negative pole of the PLC through the current correction switch, and the fifth signal input pole of the PLC is connected to the common negative pole of the PLC through the fault indicator detection switch.

[0057] In this embodiment, the boundary switch function detection circuit also includes a start switch and a stop switch; the zeroth signal input pole of the PLC is connected to the common negative pole of the PLC through the start switch, and the first signal input pole of the PLC is connected to the common negative pole of the PLC through the stop switch.

[0058] In this embodiment, the boundary switch function detection circuit also includes a leakage switch Z1, a first air switch Z2 and a second air switch Z3. The leakage switch Z1 is arranged between the primary side winding of the large current generator T and the power supply, the first air switch Z2 is arranged between the primary side winding of the large current generator T and the power connection pole of the PLC, and the second air switch Z3 is arranged between the primary side winding of the large current generator T and the power connection pole of the boundary switch.

[0059] In this embodiment, the power supply is a single-phase industrial frequency sinusoidal AC power supply. Specifically, this embodiment uses a single-phase power supply for power supply and detection, and does not use a three-phase power supply. The power is not large and it is convenient to connect to the power supply. In addition, the structure is simple, the weight is relatively light, the manufacturing cost is low, and it is also conducive to detection under field site conditions.

[0060] The beneficial effects of this embodiment are as follows:

[0061] 1. The device of this embodiment has a relatively simple structure, is cheap, portable, and easy to operate. It replaces the expensive relay protection tester, does not require frequent wiring changes, can be closer to the parameters of the working conditions when the distribution network fails, and can perform a relatively comprehensive test on the protection function of the boundary switch.

[0062] 2. This embodiment uses automatic detection according to the process through PLC. There is no need to adjust various detection parameters or change various wirings during detection. The detection parameters and wiring methods are automatically converted by the device. Therefore, a normal switch detection process takes a short time. The detection speed is more than 10 times faster than the detection devices such as relay protection instruments and large current generators in the prior art.

[0063] 3. This embodiment adds a detection item of whether the three-phase unbalanced load generates zero-sequence overcurrent to the detection of the boundary switch, which is rarely considered in other detection methods in the past. It can effectively check whether the synthetic zero-sequence algorithm using the synthetic zero-sequence current switch is correct.

[0064] 4. This embodiment can be used to simply judge whether the fault indicator is good or bad, achieving the effect of one machine with multiple uses. It can solve the needs of grassroots personnel engaged in power operation and maintenance and construction for an instrument for fault indicator detection, making it convenient to carry out work.

[0065] Embodiment 2:

[0066] This embodiment provides a detection method according to the demarcation switch function detection circuit in embodiment 1, which includes a switch function detection method. The connection diagram of the demarcation switch and the switch function detection in embodiment 1 is shown as follows: Figure 2 As shown, the switch function detection method includes the following steps:

[0067] Conduct ground fault zero-sequence overcurrent setting lower limit detection;

[0068] Conduct ground fault zero-sequence overcurrent setting upper limit detection;

[0069] Conduct zero-sequence overcurrent detection (two-phase flow, simulating phase loss condition) and phase-to-phase short-circuit overcurrent rate determination value lower limit detection to see if three-phase unbalanced load generates zero-sequence overcurrent detection (two-phase flow, simulating phase loss condition)

[0070] Conduct zero-sequence overcurrent detection to see if the three-phase unbalanced load generates zero-sequence overcurrent (one large and two small, three-phase current flow, simulating the unbalanced three-phase power consumption condition);

[0071] Perform the upper limit detection of the phase-to-phase short-circuit overcurrent rate determination value (including the absence of power on the power supply side at the moment of short circuit, simulating the substation switch tripping condition after a fault).

[0072] Furthermore, the detection method also includes a fault indicator detection method. The connection diagram of the demarcation switch and the fault indicator detection of Example 1 is shown in FIG. Figure 2 shown.

[0073] Specifically, before the detection, the first detection point A1 of the A phase and the second detection point A2 of the A phase are respectively connected to the two ends of the A phase switch of the boundary switch, the first detection point B1 of the B phase and the second detection point B2 of the B phase are respectively connected to the two ends of the B phase switch of the boundary switch, and the first detection point C1 of the C phase and the second detection point C2 of the C phase are respectively connected to the two ends of the C phase switch of the boundary switch;

[0074] The ground fault zero-sequence overcurrent setting lower limit detection method comprises the following steps, taking the detection of phase A of the boundary switch as an example:

[0075] The PLC sends electrical signals to the coil C05-1 of the fifth contactor and the coil C10-1 of the tenth contactor respectively, and the contact C05-2 of the fifth contactor and the contact C10-2 of the tenth contactor are both closed; the live line voltage of the power supply is sequentially sent to one end of the A phase switch of the boundary switch through the same-name end of the primary side winding of the large current generator T, the same-name end of the secondary side winding of the large current generator T, the fifth resistor R5 and the contact C05-2 of the fifth contactor, and the neutral line voltage of the power supply is sequentially sent to the other end of the A phase switch of the boundary switch through the opposite-name end of the primary side winding of the large current generator T, the opposite-name end of the secondary side winding of the large current generator T and the contact C10-2 of the tenth contactor;

[0076] The PLC reads the opening and closing signal of the contact C12-2 of the twelfth signal relay. Preferably, the PLC reads the opening and closing signal of the contact C12-2 of the twelfth signal relay after 0.5 seconds, and sets a delay of 0.5 seconds to prevent the influence of the jitter of each switch; if the demarcation switch is in the open state, the contact C12-2 of the twelfth signal relay is closed, and the PLC can read the closing signal of the contact C12-2 of the twelfth signal relay; if the demarcation switch is in the closed state, the contact C12-2 of the twelfth signal relay is disconnected, and the PLC can read the disconnection signal of the contact C12-2 of the twelfth signal relay; if the PLC reads the closing signal of the contact C12-2 of the twelfth signal relay, the demarcation switch is closed at this time, the contact C12-2 of the twelfth signal relay is disconnected, and the PLC reads the disconnection signal of the contact C12-2 of the twelfth signal relay, and the PLC makes the detection program wait for 10 seconds before entering the next step. Otherwise, the PLC directly enters the next step. It should be noted that the PLC instructs the detection program to wait for 10 seconds before entering the next step, waiting for the boundary switch with automatic electric energy storage to complete energy storage, or for the manual mechanism to close the switch and then move to the open energy storage position;

[0077] The PLC sends an electrical signal to the coil of the zero contactor, and the contact C00-2 of the zero contactor closes;

[0078] The PLC reads the opening and closing signal of the contact C12-2 of the twelfth signal relay. Preferably, the PLC waits for 4 seconds before reading the opening and closing signal of the contact C12-2 of the twelfth signal relay, and then stops sending electrical signals to the coil of the zero contactor, and the contact C00-2 of the zero contactor is disconnected; if the PLC reads the disconnection signal of the contact C12-2 of the twelfth signal relay, it is determined that the ground fault zero-sequence overcurrent setting lower limit function of the A-phase switch of the boundary switch is normal; if the PLC reads the closing signal of the contact C12-2 of the twelfth signal relay, it is determined that the ground fault zero-sequence overcurrent setting lower limit function of the A-phase switch of the boundary switch is abnormal;

[0079] The ground fault zero-sequence overcurrent setting upper limit detection includes the following steps, taking the detection of phase A of the boundary switch as an example:

[0080] The PLC sends electrical signals to the coil C05-1 of the fifth contactor and the coil C10-1 of the tenth contactor respectively, and the contact C05-2 of the fifth contactor and the contact C10-2 of the tenth contactor are both closed; the live line voltage of the power supply is sequentially sent to one end of the A phase switch of the boundary switch through the same-name end of the primary side winding of the large current generator T, the same-name end of the secondary side winding of the large current generator T, the fifth resistor R5 and the contact C05-2 of the fifth contactor, and the neutral line voltage of the power supply is sequentially sent to the other end of the A phase switch of the boundary switch through the opposite-name end of the primary side winding of the large current generator T, the opposite-name end of the secondary side winding of the large current generator T and the contact C10-2 of the tenth contactor;

[0081] The PLC reads the opening and closing signal of the contact C12-2 of the twelfth signal relay. Preferably, the PLC reads the opening and closing signal of the contact C12-2 of the twelfth signal relay after 0.5 seconds, and sets a delay of 0.5 seconds to prevent the influence of the jitter of each switch; if the demarcation switch is in the open state, the contact C12-2 of the twelfth signal relay is closed, and the PLC can read the closing signal of the contact C12-2 of the twelfth signal relay; if the demarcation switch is in the closed state, the contact C12-2 of the twelfth signal relay is disconnected, and the PLC can read the disconnection signal of the contact C12-2 of the twelfth signal relay; if the PLC reads the closing signal of the contact C12-2 of the twelfth signal relay, the demarcation switch is closed at this time, the contact C12-2 of the twelfth signal relay is disconnected, and the PLC reads the disconnection signal of the contact C12-2 of the twelfth signal relay, and the PLC makes the detection program wait for 10 seconds before entering the next step. Otherwise, the PLC directly enters the next step. It should be noted that the PLC instructs the detection program to wait for 10 seconds before entering the next step, waiting for the boundary switch with automatic electric energy storage to complete energy storage, or for the manual mechanism to close the switch and then move to the open energy storage position;

[0082] The PLC sends an electrical signal to the coil of the zeroth contactor and the coil C01-1 of the first contactor, and the contact C00-2 of the zeroth contactor and the contact C01-2 of the first contactor are both closed;

[0083] The PLC reads the opening and closing signal of the contact C12-2 of the twelfth signal relay. Preferably, the PLC waits for 4 seconds before reading the opening and closing signal of the contact C12-2 of the twelfth signal relay, and then stops sending electrical signals to the coil of the zero contactor and the coil C01-1 of the first contactor, and the contact C00-2 of the zero contactor and the contact C01-2 of the first contactor are both disconnected; if the PLC reads the closing signal of the contact C12-2 of the twelfth signal relay, it is determined that the upper limit function of the zero-sequence overcurrent setting value of the ground fault of the A phase switch of the boundary switch is normal; if the PLC reads the opening signal of the contact C12-2 of the twelfth signal relay, it is determined that the upper limit function of the zero-sequence overcurrent setting value of the ground fault of the A phase switch of the boundary switch is abnormal.

[0084] The detection principle of the B phase of the boundary switch and the C phase of the boundary switch is the same as above.

[0085] This detection step is to verify whether the boundary switch can be opened according to the instructions of the controller when the zero-sequence current is higher than the set value.

[0086] The method for detecting whether a three-phase unbalanced load generates a zero-sequence overcurrent and the method for detecting the lower limit of the interphase short-circuit overcurrent rate determination value include the following steps: a three-phase unbalanced load, i.e., two-phase current is passed through, and a phase-loss condition is simulated, taking the AB phase detection of the boundary switch as an example:

[0087] The PLC sends electrical signals to the coil C05-1 of the fifth contactor and the coil C07-1 of the seventh contactor respectively, and the contact C05-2 of the fifth contactor and the contact C07-2 of the seventh contactor are both closed. The PLC reads the opening and closing signal of the contact C12-2 of the twelfth signal relay after 0.5 seconds, and sets a delay of 0.5 seconds to prevent the influence of the jitter of each switch; the live wire voltage of the power supply is successively sent to one end of the A phase switch of the boundary switch through the same-name end of the primary side winding of the large current generator T, the same-name end of the secondary side winding of the large current generator T, the fifth resistor R5 and the contact C05-2 of the fifth contactor, and the neutral line voltage of the power supply is successively sent to one end of the B phase switch of the boundary switch through the opposite-name end of the primary side winding of the large current generator T, the opposite-name end of the secondary side winding of the large current generator T and the contact C07-2 of the seventh contactor. If the boundary switch contact is in the disconnected state, the contact C12-2 of the twelfth signal relay is closed, and the PLC reads the closing signal of the contact C12-2 of the twelfth signal relay. At this time, close the boundary switch, the contact C12-2 of the twelfth signal relay is disconnected, and the PLC reads the disconnection signal of the contact C12-2 of the twelfth signal relay. The PLC instructs the detection program to wait for 10 seconds and then proceeds to the next step.

[0088] The PLC sends an electrical signal to the coil C04-1 of the fourth contactor, and the contact C04-2 of the fourth contactor closes;

[0089] PLC waits for 1 second;

[0090] The PLC reads the opening and closing signal of the contact C12-2 of the twelfth signal relay; if the PLC reads the opening signal of the contact C12-2 of the twelfth signal relay, it is determined that the AB phase short circuit over-current speed lower limit detection function of the boundary switch is normal. If the PLC reads the closing signal of the contact C12-2 of the twelfth signal relay, it is determined that the AB phase short circuit over-current speed lower limit detection function of the boundary switch is abnormal, and the PLC records the abnormality of this function.

[0091] The PLC waits for another 3 seconds, and then reads the open / close signal of the contact C12-2 of the twelfth signal relay. If the disconnect signal of the contact C12-2 of the twelfth signal relay is read, it is determined that the three-phase unbalanced load of the boundary switch does not produce a zero-sequence overcurrent trip. If the closing signal of the twelfth signal relay is read, it is determined that the three-phase unbalanced load of the boundary switch produces a zero-sequence overcurrent trip, and the PLC records the abnormality of this function.

[0092] The detection principles of the BC phase of the boundary switch and the CA phase of the boundary switch are the same as above.

[0093] This test step is to verify whether the boundary switch generates zero-sequence overcurrent tripping when the three-phase unbalanced load simulates the phase loss condition, two phases are flowing, and the three-phase current vector sum is 0. And when the line current is lower than the phase-to-phase short-circuit overcurrent rate determination value, the switch should not be tripped.

[0094] The method for detecting whether the three-phase unbalanced load generates zero-sequence overcurrent is to detect one large phase and two small phases, and to simulate the unbalanced three-phase power consumption condition, including the following steps, taking the detection of the A-BC phase of the boundary switch as an example:

[0095] The PLC sends electrical signals to the coil C05-1 of the fifth contactor, the coil C07-1 of the seventh contactor and the coil C09-1 of the ninth contactor respectively, and the contact C05-2 of the fifth contactor, the contact C07-2 of the seventh contactor and the contact C09-2 of the ninth contactor are closed. The PLC reads the opening and closing signal of the contact C12-2 of the twelfth signal relay after 0.5 seconds. The live wire voltage of the power supply passes through the same-name end of the primary winding of the large current generator T, the same-name end of the secondary winding of the large current generator T, the fifth resistor R5 and the first resistor R7 in turn. The contact C05-2 of the fifth contactor is sent to one end of the A phase switch of the demarcation switch, and one path of the zero line voltage of the power supply is sent to one end of the B phase switch of the demarcation switch through the opposite end of the primary winding of the large current generator T, the opposite end of the secondary winding of the large current generator T and the contact C07-2 of the seventh contactor in sequence, and the other path of the zero line voltage of the power supply is sent to one end of the B phase switch of the demarcation switch through the opposite end of the primary winding of the large current generator T, the opposite end of the secondary winding of the large current generator T and the contact C09-2 of the ninth contactor in sequence. If the demarcation switch is in the open state, the contact C12-2 of the twelfth signal relay is closed, and the PLC reads the closing signal of the contact C12-2 of the twelfth signal relay. At this time, the demarcation switch is closed, and the contact C12-2 of the twelfth signal relay is disconnected. The PLC reads the disconnection signal of the contact C12-2 of the twelfth signal relay, and the PLC makes the detection program wait for 10 seconds before entering the next step. Otherwise, the PLC directly enters the next step.

[0096] The PLC instructs C04 to close, the PLC waits for 4 seconds, reads the twelfth signal relay open / close signal, and then C04 opens.

[0097] If the twelfth signal relay is read as disconnected, it is considered that the three-phase unbalanced load of the boundary switch does not cause zero-sequence overcurrent tripping, and the next step of detection is continued. If the twelfth signal relay is read as closed, it is considered that the three-phase unbalanced load of the boundary switch causes zero-sequence overcurrent tripping, and the PLC records the abnormal function, and the next step of detection is continued.

[0098] The detection principles of the B-CA phase of the boundary switch and the C-AB phase of the boundary switch are the same as above.

[0099] This detection step is to verify whether the boundary switch generates zero-sequence overcurrent tripping when the three-phase unbalanced load occurs, but the vector sum of the three-phase current is 0.

[0100] This item is added to prevent some manufacturers from cheating in the detection of whether a three-phase unbalanced load generates a zero-sequence overcurrent trip. The two-phase flow is used, that is, the three-phase unbalanced load that simulates the phase loss condition generates a zero-sequence overcurrent detection method. Some manufacturers set a cheating method in the control program to lock the zero-sequence overcurrent trip when one phase current is 0. After the three-phase flow is used, for example, in the A-BC detection, since there is often a difference in the contact resistance in the primary connection of the B and C phases, the current passing through the A phase is not evenly distributed to the B and C phases, but a random number, which can effectively prevent the above cheating method.

[0101] The method for detecting the upper limit of the current velocity determination value of the phase-to-phase short circuit, i.e., when there is no power on the power supply side at the moment of the short circuit, simulating the tripping condition of the substation switch after the fault, comprises the following steps, taking the AB phase detection of the boundary switch as an example:

[0102] The PLC commands C05 and C07 to close, and the PLC reads the opening and closing signal of the twelfth signal relay after 0.5 seconds; the live line voltage is sent from L2→R5→L3→C05 to the side of the boundary switch located at the first detection point A1 of phase A, and the neutral line voltage is sent from N2→N3→C07 to the side of the boundary switch located at the first detection point B1 of phase B. If the boundary switch contacts are in the open state, the twelfth signal relay voltage relay has voltage closure, the PLC reads the twelfth signal relay closing signal, the PLC commands the detection program to wait, and does not proceed to the next step; at this time, the boundary switch is closed, the contact C12-2 of the twelfth signal relay is disconnected, the PLC reads the twelfth signal relay disconnection signal, the PLC commands the detection program to wait for 10 seconds, and then proceeds to the next step. If the PLC commands C05 and C07 to close, and the PLC reads the twelfth signal relay opening signal after 0.5 seconds, the program does not wait to proceed.

[0103] The PLC instructs C03 and C04 to close, the PLC waits for 1 second, reads the twelfth signal relay open / close signal, and then C03 and C04 are disconnected.

[0104] If the twelfth signal relay is closed, it is considered that the boundary switch interphase short circuit overcurrent speed upper limit detection function is normal, and continue to the next step of detection. If the twelfth signal relay is disconnected, it is considered that the boundary switch interphase short circuit overcurrent speed upper limit detection function is abnormal, the PLC records the abnormality of this function, and continue to the next step of detection.

[0105] The BC phase detection principle of the boundary switch is the same as above.

[0106] This test step is to verify the demarcation switch. When the phase-to-phase short-circuit current is higher than the set value, it should be tripped. At this time, the substation outgoing line switch is not tripped, and the distribution line still has voltage.

[0107] In the detection of the boundary switch CA phase, the PLC instructs C05 and C09 to close, and the PLC reads the opening and closing signal of the twelfth signal relay after 0.5 seconds; the live line voltage is sent from L2→R5→L3→C05 to the side of the boundary switch located at the first detection point A1 of phase A, and the neutral line voltage is sent from N2→N3→C09 to the side of the boundary switch located at the first detection point C1 of phase C. If the boundary switch contact is in the open state, the twelfth signal relay voltage relay has voltage closure, the PLC reads the twelfth signal relay closing signal, the PLC instructs the detection program to wait, and does not proceed to the next step; at this time, the boundary switch is closed, the contact C12-2 of the twelfth signal relay is disconnected, the PLC reads the twelfth signal relay disconnection signal, the PLC instructs the detection program to wait for 10 seconds, and then proceeds to the next step. If the PLC instructs C05 and C09 to close, the PLC reads the twelfth signal relay opening signal after 0.5 seconds, and does not wait for the program to proceed.

[0108] The PLC instructions C03, C04, and C11 are closed, the PLC waits for 1 second, and reads the opening and closing signal of the twelfth signal relay.

[0109] If the twelfth signal relay is closed, it is considered that the boundary switch interphase short circuit overcurrent speed upper limit detection function is normal, and continue to the next step of detection. If the twelfth signal relay is disconnected, it is considered that the boundary switch interphase short circuit overcurrent speed upper limit detection function is abnormal, and the PLC records the abnormal function. After C11 is closed, it delays for 1 second and C11 is disconnected. The entire test is completed.

[0110] This test step is to verify the demarcation switch. When the phase-to-phase short-circuit current is higher than the set value, it should be tripped. At this time, the substation outgoing line switch is tripped and there is no voltage in the distribution line.

[0111] The connection diagram of the demarcation switch and the fault indicator detection in Example 1 is as follows: Figure 3 As shown, the fault indicator detection method comprises the following steps:

[0112] Pass 360A current for 0.5S;

[0113] Manual observation to see if the card is flipped;

[0114] Pass 7A current for 1min;

[0115] Pass 360A current again for 0.5S;

[0116] Manually observe whether the card is flipped.

[0117] In the prior art, since fault indicators are not very important in the distribution network and are relatively cheap (more than 100 yuan per unit for ordinary types), special detection devices are expensive (more than 100,000 yuan), and it is difficult for power supply companies, construction teams, and professional detection companies below the municipal level to have detection equipment. Therefore, it is difficult to understand the status of a newly installed or after-operation fault indicator for a period of time. However, this embodiment can generate a controllable large current, so it can also be used to simply judge the quality of the fault indicator, achieving a multi-purpose effect.

[0118] The multiple embodiments described above are merely illustrative. If a unit described as a separate component is involved, it may or may not be physically separated; if a component displayed as a unit is involved, it may or may not be a physical unit, that is, it may be located in one place, or it may be distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment. Ordinary technicians in this field can understand and implement it without paying creative labor.

[0119] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention is described in detail with reference to the above embodiments, a person skilled in the art should understand that the technical solutions described in the above embodiments can still be modified, or some of the technical features can be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

[0120] Finally, it should be noted that the present invention is not limited to the above optional implementations, and anyone can derive other various forms of products under the enlightenment of the present invention. The above specific implementations should not be understood as limiting the scope of protection of the present invention. The scope of protection of the present invention should be based on the definition in the claims, and the description can be used to interpret the claims.

Claims

1. A demarcation switch function detection circuit, characterized in that: It includes a high current generator (T), a PLC, a fifth resistor (R5), a zeroth resistor (R0), a first resistor (R1), a zeroth contactor, a first contactor, a fifth contactor, a sixth contactor, an eighth contactor, a tenth contactor and a twelfth signal relay; The power connection pole of the PLC is connected to the two ends of the primary winding of the large current generator (T); the zero signal output pole of the PLC is connected to the same-name end of the primary winding of the large current generator (T) through the coil (C00-1) of the zero contactor, the first signal output pole of the PLC is connected to the same-name end of the primary winding of the large current generator (T) through the coil (C01-1) of the first contactor, the fifth signal output pole of the PLC is connected to the opposite-name end of the primary winding of the large current generator (T) through the coil (C05-1) of the fifth contactor, and the The sixth signal output pole is connected to the opposite end of the primary winding of the large current generator (T) through the coil (C06-1) of the sixth contactor, the eighth signal output pole of the PLC is connected to the opposite end of the primary winding of the large current generator (T) through the coil (C08-1) of the eighth contactor, the tenth signal output pole of the PLC is connected to the opposite end of the primary winding of the large current generator (T) through the coil (C10-1) of the tenth contactor, and the eighth signal input pole of the PLC is connected to the common negative pole of the PLC through the contact (C12-2) of the twelfth signal relay; The two ends of the primary winding of the large current generator (T) are respectively connected to the two poles of the power supply; the same-name end of the secondary winding of the large current generator (T) is connected to the first detection point (A1) of the A phase through the fifth resistor (R5) and the contact (C05-2) of the fifth contactor in sequence; the zeroth resistor (R0) and the contact (C00-2) of the zeroth contactor are connected in series to form a first branch; the first resistor (R1) and the contact (C01-2) of the first contactor are connected in series to form a second branch; the first branch and the second branch are both connected in parallel with the fifth resistor (R5); the junction point of the fifth resistor (R5) and the contact (C05-2) of the fifth contactor is connected to the first detection point (B1) of the B phase through the contact (C06-2) of the sixth contactor; the fifth resistor (R5) and the fifth ... connected in parallel with the fifth resistor (R5); the junction point of the fifth resistor (R5) and the contact (C05-2) of the fifth contactor is connected to the first detection point (B1) of the B phase through the contact (C06-2) of the sixth contactor; the fifth resistor (R5) and the fifth contactor are connected in series to form a second branch; the first branch and the second branch are connected in parallel to the fifth resistor (R5); the first branch and the second branch are connected in parallel to the fifth resistor (R5); the first branch and the second branch are connected in parallel to the fifth resistor (R5); the first branch and the second The junction point of the contact (C05-2) of the high current generator (T) is connected to the first detection point (C1) of the C phase through the contact (C08-2) of the eighth contactor, and the junction point of the fifth resistor (R5) and the contact (C05-2) of the fifth contactor is also connected to the live wire of the power supply; the opposite-name ends of the secondary winding of the high current generator (T) are respectively connected to the second detection point (A2) of the A phase, the second detection point (B2) of the B phase and the second detection point (C2) of the C phase through the contact (C10-2) of the tenth contactor, the opposite-name ends of the secondary winding of the high current generator (T) are connected to the junction point of the fifth resistor (R5) and the contact (C05-2) of the fifth contactor through the coil (C12-1) of the twelfth signal relay, and the opposite-name ends of the secondary winding of the high current generator (T) are also connected to the neutral wire of the power supply; The two ends of the primary winding of the large current generator (T) are connected to the power supply pole of the boundary switch; The demarcation switch function detection circuit also includes a start switch and a stop switch; the zero signal input pole of the PLC is connected to the common negative pole of the PLC through the start switch, and the first signal input pole of the PLC is connected to the common negative pole of the PLC through the stop switch; The power supply is a single-phase industrial frequency sinusoidal AC power supply.

2. A boundary switch function detection circuit according to claim 1, characterized in that: The demarcation switch function detection circuit also includes a fourth resistor (R4), a fourth contactor, a seventh contactor and a ninth contactor; The fourth signal output pole of the PLC is connected to the opposite end of the primary winding of the large current generator (T) through the coil (C04-1) of the fourth contactor, the seventh signal output pole of the PLC is connected to the opposite end of the primary winding of the large current generator (T) through the coil (C07-1) of the seventh contactor, and the ninth signal output pole of the PLC is connected to the opposite end of the primary winding of the large current generator (T) through the coil (C09-1) of the ninth contactor; The fourth resistor (R4) and the contact (C04-2) of the fourth contactor are connected in series to form a third branch, and the third branch is connected in parallel with the fifth resistor (R5); the opposite-name end of the secondary winding of the large current generator (T) is connected to the first detection point (B1) of the B phase through the contact (C07-2) of the seventh contactor, and the opposite-name end of the secondary winding of the large current generator (T) is connected to the first detection point (C1) of the C phase through the contact (C09-2) of the ninth contactor.

3. A boundary switch function detection circuit according to claim 2, characterized in that: The demarcation switch function detection circuit also includes a third resistor (R3), a third contactor and an eleventh contactor; The third signal output pole of the PLC is connected to the opposite end of the primary winding of the large current generator (T) through the coil (C03-1) of the third contactor, and the eleventh signal output pole of the PLC is connected to the opposite end of the primary winding of the large current generator (T) through the coil (C11-1) of the eleventh contactor; The third resistor (R3) and the contact (C03-2) of the third contactor are connected in series to form a fourth branch, and the fourth branch is connected in parallel with the fifth resistor (R5); One end of the contact (C11-2) of the eleventh contactor is connected to the opposite end of the primary winding of the large current generator (T), and the other end of the contact (C11-2) of the eleventh contactor is connected to the power output pole of the boundary switch.

4. A boundary switch function detection circuit according to claim 3, characterized in that: The boundary switch function detection circuit also includes a short-circuit detection switch, an increased zero-sequence current detection switch, a current correction switch and a fault indicator detection switch; the second signal input pole of the PLC is connected to the common negative pole of the PLC through the short-circuit detection switch, the third signal input pole of the PLC is connected to the common negative pole of the PLC through the increased zero-sequence current detection switch, the fourth signal input pole of the PLC is connected to the common negative pole of the PLC through the current correction switch, and the fifth signal input pole of the PLC is connected to the common negative pole of the PLC through the fault indicator detection switch.

5. A boundary switch function detection circuit according to claim 1, characterized in that: The boundary switch function detection circuit also includes a leakage switch (Z1), a first air switch (Z2) and a second air switch (Z3), wherein the leakage switch (Z1) is arranged between the primary winding of the large current generator (T) and the power supply, the first air switch (Z2) is arranged between the primary winding of the large current generator (T) and the power supply connection pole of the PLC, and the second air switch (Z3) is arranged between the primary winding of the large current generator (T) and the power supply connection pole of the boundary switch.

6. A detection method for a boundary switch function detection circuit, characterized in that: The detection method is implemented based on the boundary switch function detection circuit according to claim 3 or 4, and includes a switch function detection method, and the switch function detection method includes the following steps: Conduct ground fault zero-sequence overcurrent setting lower limit detection; Conduct ground fault zero-sequence overcurrent setting upper limit detection; Conduct zero-sequence overcurrent detection and phase-to-phase short-circuit overcurrent rate determination value lower limit detection for three-phase unbalanced load; Detect whether the three-phase unbalanced load generates zero-sequence overcurrent; Perform phase-to-phase short circuit overcurrent rate determination value upper limit detection.

7. A detection method for a boundary switch function detection circuit according to claim 6, characterized in that: The detection method also includes a fault indicator detection method.

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