A fault handling device for phase-to-phase short circuits in a three-phase power system

Abstract

The application discloses a kind of three-phase power system interphase short-circuit fault handling device, including on-off mechanism, the on-off mechanism one end connects neutral point or bus one phase, two phases or three phases, the other end connects ground or public wire, it further includes starting module, current control module and closing module, on-off mechanism after receiving the starting signal starts continuously or intermittently to connect the neutral point or bus certain phase with ground or the public wire, until receiving the closing signal and stop conducting.This device can connect certain phase of bus or neutral point with ground or public wire according to the occurrence and removal of interphase short-circuit fault, so as to form detection loop with related line to produce continuous or intermittent current for controlled switch in detection loop to identify, the actual situation of fault point resistance in the device can effectively control loop current in interphase short-circuit, guarantee the current value of detection loop in safety range, avoid current too large to cause impact on system.

Description

TECHNICAL FIELD

[0001] The present application relates to a device, in particular to a device for handling phase-to-phase short circuit fault of a three-phase power system. BACKGROUND

[0002] At present, the handling of phase-to-phase short circuit fault of a power supply system has problems such as complicated operation, untimely, inaccurate positioning, etc., which affects the power supply quality. The invention patent application 202011492758.3 and the invention patent application 202011453632.5 provide a method for handling phase-to-phase short circuit of a power supply system. According to the method, when a phase-to-phase short circuit occurs, one fault phase is maintained to be on and the remaining fault phases are tripped, then another fault phase is grounded to simulate a single-phase-to-ground fault, and then one live phase is connected to the ground, so that one phase of two or three fault phases connected through the short circuit fault point is connected to a live phase on the system to form a closed loop and generate current or current pulse, and then the controlled switch installed on the fault line detects the current duration or the number of current pulses and trips to remove the fault. In actual operation, it is necessary to maintain one fault phase to be on and the other fault phase to be grounded or connected to a utility conductor, and the busbar or neutral point needs to be connected to the ground or connected to a utility conductor to form the above-mentioned closed loop and generate current. There are many specific implementation ways to connect the busbar or neutral point to the ground or connect the utility conductor, and how to complete this operation through a suitable fault handling device is of great significance to the solution of the fault. SUMMARY

[0003] The purpose of the present application is to provide a device for handling phase-to-phase short circuit fault of a three-phase power system. The device can connect a certain phase of the busbar or the neutral point to the ground or a utility conductor according to the occurrence and removal of the phase-to-phase short circuit fault, so as to form a detection loop with the related line to generate continuous or intermittent current for the controlled switch in the detection loop to identify. The device can effectively control the loop current according to the actual resistance of the fault point in the phase-to-phase short circuit, so as to ensure that the current value of the detection loop is within a safe range and avoid the impact on the system caused by excessive current.

[0004] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0005] A kind of three-phase power system phase short-circuit fault handling device, including on-off mechanism, one end of the on-off mechanism connects the phase of neutral point or bus, two phases or three phases, the other end connects ground or public wire, it also includes starting module, current control module and closing module, the starting module detects the occurrence of phase short-circuit fault and removal and generates the starting signal for starting the on-off mechanism conduction;The current control module controls the current flowing through on-off mechanism in the preset range;The closing module generates the closing signal for disconnecting the on-off mechanism;The on-off mechanism starts to continuously or intermittently connect the phase of neutral point or bus with ground or the public wire after receiving the starting signal, until the on-off mechanism stops conducting after receiving the closing signal.

[0006] Preferably, the starting module starts timing from phase fault removal, and sends the starting signal for starting the on-off mechanism conduction after a preset time.

[0007] Preferably, the starting module obtains information from the auxiliary node of the outgoing line head breaker, and generates the starting signal when phase short-circuit fault is found by bus voltage detection and the head breaker is tripped.

[0008] Preferably, the closing module measures the current flowing through the on-off mechanism, and generates the closing signal when the on-off mechanism has no current after a first preset time period from the on-off mechanism starting to connect the phase of neutral point or bus with ground or public wire;Or generates the closing signal when the on-off mechanism has no current continuously for more than a second preset time period from the on-off mechanism starting to connect the phase of neutral point or bus with ground or public wire.

[0009] Preferably, when the on-off mechanism connects two phases or three phases of bus, the current control module further includes phase selection control module, and the phase selection control module selects a phase as the conduction phase of the on-off mechanism.

[0010] Preferably, the phase selection control module receives the fault phase information sent by the fault line protection device, and sends the signal for controlling the on-off mechanism to connect a phase according to the preset logic.

[0011] Preferably, the phase selection control module is equipped with three-phase PT, and the three-phase PT measures the phase-to-phase voltage before and after line fault, and determines the conduction phase of the on-off mechanism by the change of phase-to-phase voltage combined with the preset logic.

[0012] Preferably, the current control module includes resistance measurement module during phase short-circuit fault and resistance measurement module of conduction loop after the on-off mechanism is connected.

[0013] Preferably, the resistance measurement module during phase short-circuit fault receives the resistance value of fault loop during phase short-circuit fault sent by the fault line protection device through communication link.

[0014] Preferably, the inter-phase short-circuit fault resistance measuring module calculates the resistance value of the fault loop during inter-phase short-circuit according to the voltage change before and after the inter-phase short-circuit and the transformer parameter manual.

[0015] Preferably, the on-off mechanism is a circuit breaker, and a resistance selector is connected in series between the circuit breaker and the ground or the utility conductor, and the resistance selector is controlled by the current control module to connect a current-limiting resistor with a certain resistance value.

[0016] Preferably, the resistance selector comprises a driving circuit and a plurality of resistors with different resistance values, each of the resistors is connected in series with a resistor switch to form a series unit, and all the series units are connected in parallel, and the driving circuit is used to control whether the resistor switches are closed.

[0017] Preferably, the on-off mechanism is a thyristor, the current control module is provided with a PT for measuring the voltage across the thyristor and a CT for measuring the current through the thyristor, and the voltage phase angle of the thyristor when it is turned on is selected according to the instantaneous value of the current of the thyristor so as to control the current within a preset range.

[0018] Preferably, the on-off mechanism is a thyristor, and a current-limiting resistor with a certain resistance value is connected in series between the thyristor and the ground or the utility conductor, the current control module is provided with a PT for measuring the voltage across the thyristor and a CT for measuring the current through the thyristor, and the voltage phase angle of the thyristor when it is turned on is selected according to the instantaneous value of the current of the thyristor so as to control the current within a preset range.

[0019] Preferably, each phase of the on-off mechanism comprises a plurality of pairs of moving contacts and stationary contacts connected in parallel, the plurality of pairs of moving contacts and stationary contacts are arranged in one or more arc extinguishing chambers, the moving contacts approach the stationary contacts under the driving of the driving mechanism and then move away from the stationary contacts to realize on and off, and the plurality of pairs of moving contacts and stationary contacts are sequentially connected and disconnected and circulate to intermittently connect the neutral point or the bus with the ground or the utility conductor.

[0020] Preferably, the starting module obtains information from an auxiliary node of a circuit breaker at the head of an outgoing line, and the starting module generates the starting signal when an inter-phase short-circuit fault is found through bus voltage detection and the circuit breaker at the head is tripped.

[0021] In the application, the starting module can detect the occurrence of inter-phase short-circuit fault and the temporary removal of fault caused by tripping of the first circuit breaker, and generate a signal for controlling the starting of the on-off mechanism after detecting the removal, which can be directly sent to the on-off mechanism, or sent to other modules, such as the current control module, to start the on-off mechanism to conduct a certain phase or neutral point of the bus to the ground or utility conductor, and form a detection loop through the ground or utility conductor and the fault phase. The current control module can detect the resistance of the fault point, and calculate the current-limiting resistance required for the on-off mechanism in series according to the resistance to limit the current of the detection loop, or can control the thyristor to turn on and off in real time to generate a certain phase voltage, and adjust the voltage value to achieve the purpose of current limiting. The on-off mechanism adopts the mode of multiple pairs of moving and static contacts circulating action to generate intermittent current pulses, or uses the mode of thyristor real-time on-off to generate current pulses, which is convenient for accurate control, and the closing module stops the on-off mechanism work after detecting a certain time without current. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 It is a structural schematic diagram of the application (the on-off mechanism is connected to the ground);

[0023] Figure 2 It is another structural schematic diagram of the application (the on-off mechanism is connected to the utility conductor);

[0024] Figure 3 It is a third structural schematic diagram of the application (the on-off mechanism is connected to the utility conductor);

[0025] Figure 4 It is a schematic diagram of an embodiment of the on-off mechanism;

[0026] Figure 5 It is a structural schematic diagram of the resistance selector. DETAILED DESCRIPTION

[0027] The application will be further described below in combination with the drawings.

[0028] When the fault handling device is used, it is aimed at two-phase or three-phase inter-phase short-circuit in a three-phase power system, that is, when two-phase or three-phase inter-phase short-circuit occurs, one fault phase should be maintained to be conducted, the remaining fault phases should be tripped, and one fault phase should be grounded or connected to the utility conductor. Under such conditions, the neutral point or one phase of the bus is conducted to the ground or the utility conductor by using the fault handling device, so as to generate a detection loop current through the fault phase maintained to be conducted, the fault phase grounded or connected to the utility conductor, which can be detected by the controlled switch on the line, and the corresponding controlled switch can be tripped according to the set current time or current pulse number to remove the inter-phase short-circuit fault.

[0029] The structure of the fault handling device for three-phase power system inter-phase short circuit includes on-off mechanism 1, starting module 2, current control module 3 and closing module 4.

[0030] In one embodiment, the on-off mechanism is a circuit breaker, through which the closing and opening generates continuous current or intermittent current pulse. In another embodiment, each phase of the on-off mechanism includes multiple pairs of parallel moving contacts 6 and stationary contacts 7, which can be arranged in one arc chamber 5 or in multiple independent arc chambers. The moving contacts approach and then move away from the stationary contacts under the drive of the drive mechanism to realize the on and off of the circuit. The multiple pairs of moving contacts and stationary contacts are sequentially closed and opened in turn to intermittently connect the neutral point or bus with the ground or utility conductor. Through the alternating and successive action of the multiple pairs of moving contacts and stationary contacts, the fatigue effect caused by the frequent action of single circuit breaker moving and stationary contacts in a short time can be effectively overcome, and the service life can be prolonged. In another embodiment, the on-off mechanism is a thyristor, which can be closed to generate continuous current or can be frequently turned on and off to generate intermittent current. In the above examples, the on-off mechanism can only have one-phase on-off function, in which case it can connect one phase of the neutral point or bus with the ground or utility conductor. Alternatively, the on-off mechanism can have independent two-phase or three-phase on-off function to independently connect two or three phases of the bus with the ground or utility conductor. A resistance selector can be connected in series between the on-off mechanism and the ground or utility conductor, and the resistance selector is controlled by the current control module. In one embodiment, the resistance selector includes multiple resistors 801 with different resistance values and a wire 803, which are connected in series with switches 802, and then connected in parallel and connected in series with the on-off mechanism. By driving the switches connected in series with the resistors, resistors with different resistance values can be connected in series with the on-off mechanism, and the driving circuit is controlled by the current control module.

[0031] When the on-off mechanism can only conduct one phase of the bus to the ground or the utility conductor, such as only the A-phase bus to the ground or the utility conductor, the following cases are explained: when the AB-phase short circuit occurs, the B-phase can be maintained to be conducted, the A-phase outgoing line is tripped, and the A-phase outgoing line is grounded or connected to the utility conductor (maintaining the B-phase to be conducted, tripping the A-phase, and grounding or connecting the A-phase to the utility conductor are all completed by other devices, which are not the task of the present application), the circuit breaker of the on-off mechanism is closed to conduct the A-phase bus to the ground or the utility conductor, and the current is generated and flows through the detection circuit. When the AC-phase short circuit occurs, the C-phase is maintained to be conducted, the A-phase outgoing line is tripped, and the A-phase outgoing line is grounded or connected to the utility conductor, and then the on-off mechanism conducts the A-phase bus to the ground or the utility conductor, and the current is still generated in the detection circuit. When the BC-phase short circuit occurs, any one of the phases can be maintained to be conducted, and the other phase is grounded or connected to the utility conductor, and the A-phase bus is conducted to the ground or the utility conductor, and the current is still generated in the detection circuit. If the ABC three-phase short circuit occurs, the A-phase outgoing line is tripped, and then the above-mentioned BC-phase short circuit processing is performed.

[0032] In one embodiment, the starting module detects the bus voltage through the voltage transformer (PT) 201, and when the voltages of two or three phases in the three-phase bus are simultaneously reduced by more than a threshold value, and the effective values of the voltages tend to be the same, it is determined that a phase-to-phase fault occurs, and when the voltage values of the three-phase bus return to normal, it indicates that the protection device of the three-phase power system trips to temporarily cut off the fault line, and at this time, the starting module generates a starting signal, which is used to trigger the on-off mechanism to start to conduct the detection circuit. In another embodiment, the starting module obtains information from the auxiliary node of the outgoing line head circuit breaker 11, and when the phase-to-phase short circuit fault is found through the bus voltage detection, the head circuit breaker is tripped, indicating that the phase-to-phase short circuit occurs and is temporarily cut off, and at this time, the starting module can generate a starting signal. In another embodiment, the starting module can also directly obtain the information of the phase-to-phase short circuit and the tripping of the head circuit breaker to cut off the phase-to-phase short circuit fault from the protection device of the power system, and generate a starting signal therefrom. After the starting signal is generated and sent out, the on-off mechanism starts to act to continuously conduct or intermittently conduct.

[0033] In one embodiment, the starting module begins timing from the clearing of the phase-to-phase fault, and after a preset time, sends a start signal to activate the switching mechanism. Because the occurrence and elimination of phase-to-phase short-circuit faults are random—some are transient, others are permanent—transient faults disappear instantly, allowing for direct restoration of power. However, it's impossible to predict in advance whether a particular fault will be transient or permanent. Traditionally, the system recloses to restore power after a certain time (e.g., 2 seconds). If a phase-to-phase short circuit still exists after reclosing, it indicates it's not a transient fault, and the system trips again for maintenance. With the fault handling device and method of this invention, the switching device is activated after a preset time (e.g., 2 seconds), generating a controllable current. If a controllable current is generated, it indicates the phase-to-phase short-circuit fault has not been cleared. In this case, the fault is directly eliminated using a controlled switch on the line that detects the current duration or current pulse. If no current is generated, it indicates a transient fault, and the shut-off module sends a shut-off signal to disconnect the switching mechanism. Then, the system directly recloses to restore power. This can replace traditional reclosing operations and overcome the impact on the system caused by the fault not being cleared after reclosing. Furthermore, this logic can be used repeatedly, allowing for secondary, tertiary, or even more reclosing operations. One advantage of this method is that the current flowing through the fault circuit is an artificially created, controllable current, reducing the impact of short-circuit current on the system (transformer, switch, conductors).

[0034] The current control module measures the resistance at the phase-to-phase short-circuit fault point and determines the resistor to be connected in series in the detection circuit based on the resistance value and the upper and lower limits of the current value in the preset detection circuit. Then, it controls a resistance selector to select a suitable resistor to be connected in series with the switching mechanism. In one embodiment, the current control module includes a resistance measurement module for phase-to-phase short-circuit faults and a resistance measurement module for the circuit after the switching mechanism is activated. In one embodiment, the resistance measurement module for phase-to-phase short-circuit faults directly receives data from the fault line protection device (…). Figure 3 The resistance value of the fault circuit during a phase-to-phase short-circuit fault is transmitted via a communication link. In another embodiment, the resistance measurement module detects the phase-to-phase voltage (TPV) during a phase-to-phase short-circuit fault using PT 201. Figure 1 or Figure 2 Based on the voltage values ​​before and after the phase-to-phase short circuit fault and the transformer parameter manual, the resistance value of the fault circuit during a phase-to-phase short circuit can be calculated.

[0035] When the on-off mechanism connects two or three phases of the bus with the ground or the utility conductor, the current control module further comprises a phase selection control module. The phase selection control module is equipped with a three-phase PT, which measures the phase-to-phase voltage before and after the line fault, and determines the on-off mechanism to conduct a certain phase by combining the voltage change with the preset logic. The implementation of the preset phase selection logic of an on-off device is as follows: first, the fault phase is sensed, and the two or three phases whose voltage changes before and after the fault exceed the threshold are the fault phase; after the fault phase is determined, a certain fault phase of the fault line is maintained to be on, and the other fault phase (or two phases) is turned off and connected to the ground or the utility conductor; then, the closing phase of the on-off mechanism is determined, and the off phase or the non-fault phase can be selected as the closing phase of the on-off mechanism. For example, as long as the AB phase-to-phase fault occurs, the A phase line is preset to be maintained to be on, and the B phase line is turned off and connected to the ground or the utility conductor, then the on-off mechanism selects the C phase or the B phase to be connected to the ground or the utility conductor, and other faults are handled in a similar manner. As long as the fault phase is determined, the preset logic can be used to determine which phase of the on-off device is connected to the ground or the utility conductor, and the determination of the fault phase according to the voltage change before and after the fault is a conventional technique in the field.

[0036] In another embodiment, the phase selection control circuit receives the fault phase information from the fault line protection device, and determines the on phase of the on-off mechanism according to the fault phase information and the aforementioned preset logic. The preset logic is to determine a fault phase to be on, and another or another two fault phases to be turned off, and then make the bus of the turned-off phase or the non-fault phase conduct through the on-off mechanism and the ground or the utility conductor, and send a switch quantity signal to control the on-off mechanism to conduct the phase.

[0037] In another embodiment, the on-off mechanism is a thyristor, the current control module is equipped with a PT to detect the voltage across the thyristor, and a CT to detect the current passing through the thyristor, and then selects the voltage phase angle when the thyristor is turned on according to the size of the current value and the preset control range, i.e. when the current is too large, the voltage value is selected to be low before turning on, and if the current is too small, the voltage can be selected to be high before turning on. A resistor can also be connected in series in the circuit to limit the circuit current to be less than the preset value.

[0038] The closing module generates a closing signal for disconnecting the on-off mechanism, which starts to continuously or intermittently conduct a certain phase of the neutral point or bus to the ground or public conductor after receiving the starting signal, and stops conducting until receiving the closing signal. In one embodiment, the closing module measures the current flowing through the on-off mechanism through the current transformer (CT) 401, detects no current after a preset time period after the on-off mechanism starts to conduct a certain phase of the neutral point or bus to the ground or public conductor, or continuously detects no current for a certain preset time period, and then sends a signal to disconnect the on-off mechanism. In this way, after fault removal, the on-off mechanism can be stopped in time to conduct in order to restore power supply by reclosing the system fault line. For example, after the on-off mechanism conducts after the starting signal is sent, no current is detected after a preset time period, which may be a transient fault and has been automatically eliminated, and the on-off mechanism can be directly closed at this time. Or continuously no current is detected for a certain preset time period, which may be an interphase short-circuit fault that has been removed by the controlled switch on the line, and the on-off mechanism also needs to be stopped at this time.

[0039] The above embodiments are only a number of descriptions of the concept and implementation of the present application, and are not a limitation. Under the concept of the present application, technical solutions without substantial changes are still within the protection scope.

Claims

1. A fault handling apparatus for phase-to-phase short circuits in a three-phase electric power system, characterized in that When two-phase or three-phase phase-to-phase short circuit occurs in a three-phase power system, the fault handling device selects one phase of the bus to be connected to the ground or a utility conductor to form a detection loop and generate a detection current under the condition that one fault phase is maintained to be on, the rest fault phases are opened, and the other fault phase is connected to the ground or the utility conductor; The fault handling device comprises a switching mechanism connected to two or three phases of the bus at one end and connected to the ground or the utility conductor at the other end, and further comprises a starting module, a current control module and a closing module, the starting module detects the occurrence and removal of the phase-to-phase short circuit fault and generates a starting signal for starting the switching mechanism to be on, the current control module controls the current flowing through the switching mechanism to be within a preset range, and the closing module generates a closing signal for turning off the switching mechanism; the switching mechanism starts to continuously or intermittently connect a certain phase of the bus to the ground or the utility conductor upon receiving the starting signal and stops the connection upon receiving the closing signal. The starting module starts timing from the opening of the circuit breaker at the first end to temporarily remove the phase-to-phase fault, and then sends the starting signal for starting the switching mechanism to be on after a preset time. The closing module measures the current flowing through the switching mechanism, and generates the closing signal when the switching mechanism has no current after a first preset time period since the switching mechanism starts to connect a certain phase of the bus to the ground or the utility conductor, or generates the closing signal when there is no current continuously for more than a second preset time period since the switching mechanism starts to connect a certain phase of the bus to the ground or the utility conductor. The current control module further comprises a phase selection control module, and the phase selection control module selects one phase of the bus to be the on phase of the switching mechanism, which is another fault phase different from the fault phase maintained to be on or a non-fault phase to form the detection loop and generate the detection current.

2. The failure handling apparatus according to claim 1, wherein The phase selection control module receives the fault phase information sent by the fault line protection device and sends a signal for controlling the switching mechanism to connect a certain phase according to a preset logic.

3. The fault handling device of claim 2, wherein, The phase selection control module is provided with a three-phase PT, which measures the phase-to-phase voltage before and after the line fault, and determines the on phase of the switching mechanism according to the change of the phase-to-phase voltage and a preset logic.

4. The fault handling device of claim 1, wherein, The current control module comprises a resistance measurement module during the phase-to-phase short circuit fault and a resistance measurement module of the on loop after the switching mechanism is on.

5. The fault handling device of claim 4, wherein, The resistance measurement module during the phase-to-phase short circuit fault receives the resistance value of the fault loop during the phase-to-phase short circuit fault sent by the fault line protection device through a communication link.

6. The fault handling device of claim 5, wherein, The resistance measurement module during the phase-to-phase short circuit fault calculates the resistance value of the fault loop during the phase-to-phase short circuit fault according to the voltage change before and after the phase-to-phase short circuit fault and the transformer parameter manual.

7. The fault handling device of claim 1, wherein, The switching mechanism is a circuit breaker, and a resistance selector is connected in series between the circuit breaker and the ground or the utility conductor, and the resistance selector is controlled by the current control module to connect a current-limiting resistor with a certain resistance value in series.

8. The fault handling device of claim 7, wherein, The resistance selector comprises a driving circuit and a plurality of resistors with different resistance values, each resistor is connected in series with a resistor switch to form a series unit, all series units are connected in parallel, and the driving circuit is used to control whether the resistor switch is closed.

9. The fault handling device of claim 1, wherein, The on-off mechanism is a thyristor, the current control module is provided with a PT for measuring the voltage across the thyristor and a CT for measuring the current through the thyristor, and the voltage phase angle when the thyristor is turned on is selected according to the current instantaneous value of the thyristor so as to control the current within a preset range.

10. The fault handling device of claim 1, wherein, The on-off mechanism is a thyristor, a current-limiting resistor with a certain resistance is connected in series between the thyristor and the ground or a utility conductor, the current control module is provided with a PT for measuring the voltage across the thyristor and a CT for measuring the current through the thyristor, and the voltage phase angle when the thyristor is turned on is selected according to the current instantaneous value of the thyristor so as to control the current within a preset range.

11. The fault handling device of claim 1, wherein, Each phase of the on-off mechanism comprises a plurality of pairs of parallel moving contacts and stationary contacts, the parallel pairs of moving contacts and stationary contacts are arranged in one or more arc extinguishing chambers, the moving contacts approach the stationary contacts under the driving of a driving mechanism and then move away from the stationary contacts so as to realize on and off, and the parallel pairs of moving contacts and stationary contacts are sequentially combined and separated and circulated so as to intermittently connect the bus with the ground or a utility conductor.

12. The fault handling device of claim 1, wherein The starting module obtains information from an auxiliary node of a first-end circuit breaker of an outgoing line, and generates the starting signal when an inter-phase short-circuit fault is found through bus voltage detection and the first-end circuit breaker is tripped.

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