AC circuit breaker differential coordination detection system

Abstract

The present invention relates to the technical field of electric power systems, and proposes an AC circuit breaker differential coordination detection system, including a short-circuit simulation module, which is arranged at the output end of a certain level of distribution line, and the short-circuit simulation module is used to simulate a short circuit of the load; a skip-trip detection module, which is used to detect the opening and closing states of AC circuit breakers at various levels; a main monitoring module, which is used to send a trigger signal to the short-circuit simulation module and receive the opening and closing signal output by the skip-trip detection module; and a wireless transmission module, which is connected to the main monitoring module and is used to send information on the differential coordination of the AC feed network to a user terminal. Through the above technical solution, the problem of mismatch of AC circuit breaker protection action characteristics in the prior art, which causes AC power failure in the entire station and expands the scope of the accident, is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of power systems, and in particular to an AC circuit breaker differential coordination detection system. Background Art

[0002] In the power system, AC power is the most basic power source for substations. It is used as the power source for cooling fans, domestic electricity, fire pumps, charging devices, and power distribution and maintenance. It is the basic guarantee for the safe and reliable operation of substations.

[0003] At present, the AC feeder network of the substation mostly adopts a tree structure. From the substation to the power equipment in the station, it generally goes through three or four levels of power distribution. Each level of power distribution mostly uses AC circuit breakers as protection elements for overcurrent and short-circuit faults, which play the role of disconnecting and isolating the feeder loop power supply network. If the protection action characteristics of the upper and lower AC circuit breakers do not match, when a short-circuit fault occurs in the lower-level power equipment, it will cause the upper-level AC circuit breaker to trip, thereby causing power outages in other feeder lines, and even causing AC power outages in the entire station, expanding the scope of the accident.

[0004] Therefore, in order to limit the failure of the station AC power supply to the minimum range and prevent the hidden dangers caused by the mismatch of the AC circuit breaker action characteristics, it is crucial to correctly select the AC circuit breaker and coordinate the selective protection between the upper and lower levels. Summary of the invention

[0005] The present invention proposes an AC circuit breaker differential coordination detection system, which solves the problem in the prior art that the AC circuit breaker protection action characteristics do not match, which easily causes AC power failure in the entire station and expands the scope of the accident.

[0006] The technical solution of the present invention is as follows:

[0007] An AC circuit breaker level difference coordination detection system is used for an AC feeder network, wherein the AC feeder network includes multiple distribution lines, each distribution line is connected by an AC circuit breaker, and includes:

[0008] A short-circuit simulation module is arranged at the output end of a certain level of power distribution line, and is used to simulate a short circuit on the load;

[0009] Over-tripping detection module, used to detect the opening and closing status of AC circuit breakers at all levels;

[0010] A main monitoring module, used for sending a trigger signal to the short-circuit simulation module and receiving an opening and closing signal output by the over-tripping detection module;

[0011] The wireless transmission module is connected to the main monitoring module and is used to send information about the level difference coordination of the AC feeding network to the user terminal.

[0012] As a further technical solution, the short-circuit simulation module includes a bidirectional thyristor Q4, the bidirectional thyristor Q4 is connected in parallel to a load of a certain level of distribution line, and the main monitoring module controls the conduction state of the bidirectional thyristor Q4.

[0013] As a further technical solution, the short-circuit simulation module also includes transistors Q1~Q3, capacitors C1, capacitor C2 and transformer T1, the base of the transistor Q1 receives the trigger signal through a resistor R15, the emitter of the transistor Q1 is grounded, the collector of the transistor Q1 is connected to a 12V power supply through a resistor R17, the base of the transistor Q2 and the base of the transistor Q3 are connected to the collector of the transistor Q1 through a resistor R18, the collector of the transistor Q2 is connected to a 12V power supply, and the transistor The collector of Q3 is grounded, the emitter of the transistor Q2 and the emitter of the transistor Q3 are connected to the first end of the capacitor C1, the second end of the capacitor C1 is connected to the first input end of the transformer T1, the second input end of the transformer T1 is grounded, the capacitor C2 is connected in parallel to the capacitor C1, the first output end of the transformer T1 is connected to the first control end of the bidirectional thyristor Q4 through a resistor R19, and the second output end of the transformer T1 is connected to the second control end of the bidirectional thyristor Q4 through a resistor R20.

[0014] As a further technical solution, the over-tripping detection module includes an AC voltage detection circuit, the input end of which is connected to other distribution lines. The over-tripping detection module determines the open or closed state of the AC circuit breaker by detecting the AC voltage of other distribution lines.

[0015] As a further technical solution, the AC voltage detection circuit includes resistors R1~R4, an operational amplifier U1 and an operational amplifier U2, the first end of the resistor R1 is connected to the VDD power supply, the second end of the resistor R1 is connected to the first output end of the distribution line through the resistor R2, the first end of the resistor R3 is connected to the VDD power supply, the second end of the resistor R3 is connected to the second output end of the distribution line through the resistor R4, the second end of the resistor R1 is connected to the inverting input end of the operational amplifier U1 through the resistor R5, the second end of the resistor R3 is connected to the non-inverting input end of the operational amplifier U1 through the resistor R6, the second end of the resistor R1 is connected to the non-inverting input end of the operational amplifier U2 through the resistor R7, the second end of the resistor R3 is connected to the inverting input end of the operational amplifier U2 through the resistor R8, the output end of the operational amplifier U1 is connected to the first end of the resistor R11, the output end of the operational amplifier U2 is connected to the first end of the resistor R12, the second end of the resistor R11 is connected to the second end of the resistor R12, and the second end of the resistor R11 outputs an opening and closing signal.

[0016] As a further technical solution, the main monitoring module and the short-circuit simulation module, as well as the main monitoring module and the over-tripping detection module are communicatively connected via an RS485 bus.

[0017] The working principle and beneficial effects of the present invention are:

[0018] The present invention uses a short-circuit simulation module to simulate a load short-circuit fault of one of the first-level distribution lines, and uses multiple over-tripping detection modules to detect the switch closure status of each AC circuit breaker after a short-circuit fault occurs in a certain level of distribution line, so as to obtain the AC circuit breaker differential coordination detection result, and sends the differential coordination detection result to the user terminal through a wireless sending module, so that the staff can quickly and conveniently understand whether the protection action characteristics of the upper and lower AC circuit breakers of the AC feed network in the substation match, and replace them in time when they do not match, so as to avoid major power accidents.

[0019] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a principle block diagram of the present invention;

[0021] Figure 2 A circuit diagram of a short-circuit simulation module of the present invention;

[0022] Figure 3 It is a circuit diagram of the over-tripping detection module of the present invention. DETAILED DESCRIPTION

[0023] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] Example 1

[0025] This embodiment proposes an AC circuit breaker level difference coordination detection system for an AC feeder network. Figure 1 For example, the AC feed network in this embodiment includes four levels of distribution lines, namely N1, L1, N2, L2, N3, L3, N4, L4, and each level of distribution lines is connected through AC circuit breakers KD1, KD2, and KD3.

[0026] The differential matching test system in this embodiment includes:

[0027] A short-circuit simulation module is arranged at the output end of the fourth-level distribution lines N4 and L4, and is used to simulate a short circuit of the load;

[0028] Over-tripping detection module, used to detect the opening and closing status of AC circuit breakers KD1, KD2, and KD3 at each level;

[0029] The main monitoring module is used to send a trigger signal to the short-circuit simulation module and receive the opening and closing signals output by the over-tripping detection module;

[0030] A wireless transmission module, connected to the main monitoring module, is used to send information about the level difference coordination of the AC feeder network to the user terminal;

[0031] This embodiment includes the following steps during specific operation:

[0032] The main monitoring module sends a trigger signal to the short-circuit simulation module;

[0033] The short-circuit simulation module causes a load short-circuit fault to occur in the fourth-level distribution line;

[0034] The over-tripping detection module sends the opening and closing signals of the circuit breakers at each level to the main monitoring module;

[0035] The main monitoring module determines the opening and closing status of each level of circuit breakers through the opening and closing signals, and obtains the differential coordination detection results of the AC circuit breakers;

[0036] The differential coordination detection result is sent to the user terminal through the wireless sending module.

[0037] In this embodiment, when a load short circuit fault occurs in the fourth-level distribution line, in order to protect the circuit, the AC circuit breaker KD3 should be activated to disconnect the third-level distribution line from the fourth-level distribution line. At the same time, in order not to affect the normal operation of other distribution lines, the AC circuit breakers KD1 and KD2 do not operate and remain in a closed state; by detecting the switch state of each AC circuit breaker through the over-tripping detection module, the AC circuit breaker differential coordination test result can be obtained.

[0038] As a further technical solution,

[0039] like Figure 2As shown, the short-circuit simulation module includes a bidirectional thyristor Q4, the bidirectional thyristor Q4 is connected in parallel to the load of a certain level of distribution line, and the main monitoring module controls the conduction state of the bidirectional thyristor Q4. The short-circuit simulation module also includes transistors Q1~Q3, capacitor C1, capacitor C2 and transformer T1. The base of transistor Q1 receives the trigger signal through resistor R15, the emitter of transistor Q1 is grounded, the collector of transistor Q1 is connected to the 12V power supply through resistor R17, the base of transistor Q2 and the base of transistor Q3 are both connected to the collector of transistor Q1 through resistor R18, the collector of transistor Q2 is connected to the 12V power supply, the collector of transistor Q3 is grounded, the emitter of transistor Q2 and the emitter of transistor Q3 are both connected to the first end of capacitor C1, the second end of capacitor C1 is connected to the first input end of transformer T1, the second input end of transformer T1 is grounded, capacitor C2 is connected in parallel to capacitor C1, the first output end of transformer T1 is connected to the first control end of bidirectional thyristor Q4 through resistor R19, and the second output end of transformer T1 is connected to the second control end of bidirectional thyristor Q4 through resistor R20.

[0040] The trigger signal sent by the main monitoring module to the short-circuit simulation module is used to control the conduction state of the bidirectional thyristor, thereby simulating a load short-circuit fault. The working process of the short-circuit simulation module is as follows: when the input trigger signal is at a low level, transistor Q1 is cut off, transistor Q2 is turned on, and transistor Q3 is cut off. The current direction is 12V→transistor Q2→capacitors C1 and C2→primary side of transformer T1. The power supply charges capacitors C1 and C2 through transistor Q2. The current pulse on the primary side of transformer T1 flows from top to bottom, and the thyristor on the left of Q4 is driven at this time; when the input trigger signal is at a high level, transistor Q1 is turned on, transistor Q2 is cut off, and transistor Q3 is turned on. The current direction is capacitors C1 and C2→transistor Q3→primary side of transformer T1. Capacitors C1 and C2 are discharged. The current pulse on the primary side of transformer T1 flows from bottom to top, and the thyristor on the right of Q4 is driven at this time. In this way, the load short-circuit fault of the AC distribution line is realized through the charging and discharging method of C1 and C2.

[0041] As a further technical solution,

[0042] like Figure 3As shown, the over-tripping detection module includes an AC voltage detection circuit, the input end of which is connected to other distribution lines. The over-tripping detection module determines the open and closed state of the AC circuit breaker by detecting the AC voltage of other distribution lines. The AC voltage detection circuit includes resistors R1~R4, an operational amplifier U1 and an operational amplifier U2. The first end of the resistor R1 is connected to the VDD power supply, the second end of the resistor R1 is connected to the first output end of the distribution line through the resistor R2, the first end of the resistor R3 is connected to the VDD power supply, the second end of the resistor R3 is connected to the second output end of the distribution line through the resistor R4, the second end of the resistor R1 is connected to the inverting input end of the operational amplifier U1 through the resistor R5, the second end of the resistor R3 is connected to the non-inverting input end of the operational amplifier U1 through the resistor R6, the second end of the resistor R1 is connected to the non-inverting input end of the operational amplifier U2 through the resistor R7, the second end of the resistor R3 is connected to the inverting input end of the operational amplifier U2 through the resistor R8, the output end of the operational amplifier U1 is connected to the first end of the resistor R11, the output end of the operational amplifier U2 is connected to the first end of the resistor R12, the second end of the resistor R11 is connected to the second end of the resistor R12, and the second end of the resistor R11 outputs an opening and closing signal.

[0043] In this embodiment, the opening and closing state of the AC circuit breaker is determined by detecting the AC voltage of other distribution lines. The AC voltage of the distribution line passes through the attenuation circuit composed of resistors R1~R4 and the DC bias voltage source VDD, and after resistor voltage division, a millivolt-level weak voltage signal is obtained at the second end of the resistor R1 and the second end of the resistor R3, and then proportionally amplified by the operational amplifier U1. In this embodiment, the operational amplifier U1 adopts a single power supply. In order to restore all AC signals, the signal of the negative half axis of the AC signal is amplified by the operational amplifier U2. Therefore, the input ends of the operational amplifier U1 and the operational amplifier U2 are connected to opposite electrical signals. The voltage signals output by the operational amplifier U1 and the operational amplifier U2 are combined through the resistor R11 and the resistor R12 to output the voltage signal. The output detection of this voltage signal can determine whether the distribution line has electricity, and further reflect whether the AC circuit breaker of the previous level is actuated.

[0044] As a further technical solution,

[0045] In this embodiment, the main monitoring module and the short-circuit simulation module, as well as the main monitoring module and the over-tripping detection module are communicated via RS485 bus.

[0046] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An AC circuit breaker level difference coordination detection system, used in an AC feeder network, wherein the AC feeder network includes multiple distribution lines, each of which is connected by an AC circuit breaker, and is characterized in that: include, A short-circuit simulation module is arranged at the output end of a certain level of power distribution line, and is used to simulate a short circuit on the load; Over-tripping detection module, used to detect the opening and closing status of AC circuit breakers at all levels; A main monitoring module, used for sending a trigger signal to the short-circuit simulation module and receiving an opening and closing signal output by the over-tripping detection module; A wireless transmission module, connected to the main monitoring module, for transmitting information on the level difference coordination of the AC feed network to the user terminal; The short-circuit simulation module includes a bidirectional thyristor Q4, the bidirectional thyristor Q4 is connected in parallel to a load of a certain level of power distribution line, and the main monitoring module controls the conduction state of the bidirectional thyristor Q4; The short circuit simulation module also includes transistors Q1-Q3, capacitors C1, C2 and transformer T1. The base of the transistor Q1 receives the trigger signal through a resistor R15. The emitter of the transistor Q1 is grounded. The collector of the transistor Q1 is connected to a 12V power supply through a resistor R17. The bases of the transistors Q2 and Q3 are both connected to the collector of the transistor Q1 through a resistor R18. The collector of the transistor Q2 is connected to a 12V power supply. The collector of the transistor Q3 is connected to a 12V power supply. grounded, the emitter of the transistor Q2 and the emitter of the transistor Q3 are both connected to the first end of the capacitor C1, the second end of the capacitor C1 is connected to the first input end of the transformer T1, the second input end of the transformer T1 is grounded, the capacitor C2 is connected in parallel to the capacitor C1, the first output end of the transformer T1 is connected to the first control end of the bidirectional thyristor Q4 through a resistor R19, and the second output end of the transformer T1 is connected to the second control end of the bidirectional thyristor Q4 through a resistor R20.

2. The AC circuit breaker differential coordination detection system according to claim 1, characterized in that: The over-tripping detection module includes an AC voltage detection circuit, the input end of which is connected to other distribution lines. The over-tripping detection module determines the opening and closing state of the AC circuit breaker by detecting the AC voltage of other distribution lines. The other distribution lines are: distribution lines other than short-circuit distribution lines in the multi-level distribution lines, and the short-circuit distribution lines are lines where simulated short circuits occur.

3. The AC circuit breaker differential coordination detection system according to claim 2, characterized in that: The AC voltage detection circuit includes resistors R1~R4, an operational amplifier U1 and an operational amplifier U2. The first end of the resistor R1 is connected to the VDD power supply, the second end of the resistor R1 is connected to the first output end of the distribution line through the resistor R2, the first end of the resistor R3 is connected to the VDD power supply, the second end of the resistor R3 is connected to the second output end of the distribution line through the resistor R4, the second end of the resistor R1 is connected to the inverting input end of the operational amplifier U1 through the resistor R5, the second end of the resistor R3 is connected to the non-inverting input end of the operational amplifier U1 through the resistor R6, the second end of the resistor R1 is connected to the non-inverting input end of the operational amplifier U2 through the resistor R7, the second end of the resistor R3 is connected to the inverting input end of the operational amplifier U2 through the resistor R8, the output end of the operational amplifier U1 is connected to the first end of the resistor R11, the output end of the operational amplifier U2 is connected to the first end of the resistor R12, the second end of the resistor R11 is connected to the second end of the resistor R12, and the second end of the resistor R11 outputs an opening and closing signal.

4. The AC circuit breaker differential coordination detection system according to claim 1, characterized in that: The main monitoring module and the short-circuit simulation module, as well as the main monitoring module and the over-tripping detection module are connected in communication via RS485 bus.

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