A disconnection detection circuit and detection method for a load control loop

Abstract

The present invention discloses a disconnection detection circuit and a detection method for a load control loop, including a current limiting circuit, a rectification circuit, an energy storage and voltage stabilizing circuit, an energy release circuit, and a signal conditioning circuit, and a controller. The current limiting circuit, the rectification circuit, the energy storage and voltage stabilizing circuit, the energy release circuit, and the signal conditioning circuit are connected in series in sequence, and the output end of the signal conditioning circuit is connected to the signal input end of the controller; it detects whether a periodic level pulse signal is received to judge the disconnection state of the load control loop, and at the same time avoids the problem of mis-tripping of the circuit breaker caused by the milliampere-level current in the existing load control loop. The present invention can complete the disconnection detection of the control loop under a tiny current, ensure the accuracy of the detection of the load control loop, and at the same time does not cause mis-tripping of the load switch.

Description

Technical Field

[0001] The present invention relates to a disconnection detection circuit and method for a load control loop, belonging to the technical field of power load control. Background Art

[0002] Power load control is the last line of defense for orderly power consumption and an important means to ensure the stable operation of the power system. The realization of the power load control function is mainly completed through the cooperation of several links such as the system master station, dedicated transformer acquisition terminal, control loop, and load switch.

[0003] Whether the load switch of the electricity customer is controllable and whether the control loop is available are the keys to ensuring the normal implementation of load control. Therefore, it is necessary to detect in real time whether the load control loop is disconnected to ensure that the load control command can be successfully executed.

[0004] Taking the trip control as an example to illustrate the principle of current load control loop disconnection detection. When a trip is required, the controller controls the trip of the circuit breaker through a relay. The relay switch closes, and the voltage at both ends of the trip coil of the circuit breaker is the power supply voltage, and the circuit breaker trips. Under the power protection state, the small current existing in the load control loop can drive the optocoupler to conduct, and the controller can obtain the loop disconnection state by detecting the output signal of the optocoupler. Since the optocoupler needs a milliampere-level current to conduct, however, in actual applications, the existence of a milliampere-level current will cause some types of circuit breakers to trip erroneously, resulting in the unavailability of the disconnection detection function.

[0005] Therefore, how to avoid the erroneous tripping of the circuit breaker caused by the milliampere-level current in the existing load control loop, thus resulting in the unavailability of the disconnection detection function, is a technical problem that needs to be urgently solved by those skilled in the art. Summary of the Invention

[0006] Objective: To overcome the deficiencies in the prior art, the present invention provides a disconnection detection circuit and method for a load control loop. A current limiting, rectifying, energy storage and voltage stabilizing, energy releasing, and signal conditioning circuit are designed in the disconnection detection circuit of the load control loop to ensure the normal function of the loop disconnection detection and not cause the switch to trip at the same time.

[0007] Technical Solution: To solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0008] In a first aspect, a disconnection detection circuit for a load control loop includes: a current limiting circuit, a rectifying circuit, an energy storage and voltage stabilizing circuit, an energy releasing circuit, and a signal conditioning circuit, a controller. The current limiting circuit, the rectifying circuit, the energy storage and voltage stabilizing circuit, the energy releasing circuit, and the signal conditioning circuit are connected in series in sequence, and the output end of the signal conditioning circuit is connected to the signal input end of the controller.

[0009] The current limiting circuit is used to limit the current in the disconnection detection loop to the microampere level.

[0010] The rectifier circuit is used to convert the alternating current in the open-circuit detection loop into direct current.

[0011] The energy storage and voltage stabilizing circuit is used to store the energy in the open-circuit detection loop.

[0012] The energy release circuit is used to automatically release the energy and generate an energy release signal when the energy in the energy storage and voltage stabilizing circuit reaches a certain threshold.

[0013] The signal conditioning circuit is used to convert the energy release signal into a level pulse signal and transmit it to the controller.

[0014] The controller is used to detect whether a periodic level pulse signal is received. If so, it is determined that the open-circuit detection loop is normal; if not, it is determined that the open-circuit detection loop is open.

[0015] As a preferred solution, the current limiting circuit uses a current limiting resistor.

[0016] As a preferred solution, the rectifier circuit uses a full-wave rectifier circuit.

[0017] As a preferred solution, the energy storage and voltage stabilizing circuit consists of a charging capacitor and a first voltage stabilizing diode connected in parallel.

[0018] As a preferred solution, the energy release circuit includes a first transistor and a second transistor. The emitter of the first transistor is connected to one pole of the power supply of the open-circuit detection loop. The collector of the first transistor is connected to the base of the second transistor through a first resistor. The base of the first transistor is connected to the collector of the second transistor. The emitter of the second transistor is connected to the other pole of the power supply of the open-circuit detection loop. A second voltage stabilizing diode is connected in parallel between the emitter and the collector of the first transistor. The collector of the second transistor is connected to the signal conditioning circuit.

[0019] As a preferred solution, the signal conditioning circuit includes a second resistor and an optocoupler. One end of the second resistor is connected to the output end of the energy release circuit. The other end of the second resistor is connected to one end of the input of the optocoupler. The other end of the input of the optocoupler is connected to one pole of the power supply of the open-circuit detection loop. One end of the output of the optocoupler is connected to the positive pole of the voltage source through a third resistor. The other end of the output of the optocoupler is connected to the negative pole of the voltage source. The input end of the controller is connected between one end of the output of the optocoupler and the third resistor.

[0020] In a second aspect, a method for detecting an open circuit in a load control loop includes the following steps:

[0021] The controller detects whether the open-circuit detection function of the load control loop is enabled. If it is not enabled, no open-circuit detection is performed.

[0022] If the disconnection detection function of the load control loop is enabled, it is judged whether the control relay in the load control loop is closed. If the control relay is closed, the disconnection detection is not performed.

[0023] If the control relay is open, the controller detects whether there is a periodic input level inversion. If there is a periodic level inversion, the load control loop is not disconnected. If no periodic level inversion is detected, it is determined that the load control loop is disconnected.

[0024] Beneficial effects: A method for detecting disconnection of a load control loop provided by the present invention restricts the disconnection detection current of the load control loop through a resistor, completes the compatibility of the AC and DC power supplies of the negative control loop through a rectifier circuit. On the DC side of the rectifier circuit, an energy storage and voltage stabilization circuit is formed by an energy storage capacitor and a voltage stabilizing diode, an energy release circuit is formed by a triode and a voltage stabilizing tube, and a signal conditioning circuit is formed by an optocoupler and a resistor.

[0025] The loop detection circuit of the present invention can complete the disconnection detection of the control loop under a very small current, ensure the accuracy of the detection of the load control loop, and at the same time not cause mis-tripping of the load switch. It can be adapted to load control loops of different voltage levels and meet the requirements of the load control loop for disconnection detection current. Description of the Drawings

[0026] Figure 1 It is a schematic structural diagram of the load control loop of the present invention.

[0027] Figure 2 It is the disconnection detection process of the load control loop of the present invention.

[0028] Figure 3 It is a schematic structural diagram of the load control loop of the preferred embodiment of the present invention. Detailed Embodiment

[0029] The following further describes the present invention with reference to specific embodiments.

[0030] In order to implement the disconnection detection function of the load control loop and ensure that the disconnection detection current is in the microampere level, a disconnection detection circuit is innovatively designed.

[0031] As Figure 1 shown. A disconnection detection circuit for a load control loop includes: a current limiting circuit 11, a rectifier circuit 12, an energy storage and voltage stabilization circuit 13, an energy release circuit 14, and a signal conditioning circuit 15, a controller 5. The current limiting circuit 11, the rectifier circuit 12, the energy storage and voltage stabilization circuit 13, the energy release circuit 14, and the signal conditioning circuit 15 are connected in series in sequence, and the output end of the signal conditioning circuit 15 is connected to the signal input end of the controller 5.

[0032] The current limiting circuit is used to limit the current in the disconnection detection loop to the microampere level.

[0033] The rectifier circuit is used to convert the alternating current in the open - circuit detection loop into direct current or control the direct - current voltage, ensuring that the circuit can work whether the power supply is alternating current or direct current, and increasing the universality of the circuit.

[0034] The energy storage and voltage - stabilizing circuit is used to store the energy in the open - circuit detection loop.

[0035] The energy - release circuit is used to automatically release energy and generate an energy - release signal when the energy in the energy storage and voltage - stabilizing circuit reaches a certain level.

[0036] Through the cooperation of the energy - release circuit and the energy storage and voltage - stabilizing circuit, the tiny current in the load - control detection loop stores and releases the energy of the current. Through the cooperation of the energy - release circuit and the energy storage and voltage - stabilizing circuit, a periodic charge - discharge cycle and a level pulse are generated, and then a signal indicating whether the load - control loop is open - circuited is obtained. The energy - release circuit can be implemented by at least one of the following methods: a discrete transistor, a monostable flip - flop of an integrated circuit, and a comparator.

[0037] The signal - conditioning circuit is used to convert the energy - release signal into a level - pulse signal and transmit it to the controller. The signal - conditioning isolation circuit can be implemented by at least one of the following methods: an opto - coupler, a current transformer, a transformer, etc.

[0038] The controller is used to detect whether a periodic level - pulse signal is received. If so, it is determined that the open - circuit detection loop is normal; if not, it is determined that the open - circuit detection loop is open - circuited.

[0039] When the open - circuit detection circuit of a load - control loop of the present invention is in use, the open - circuit detection circuit is connected in parallel to the load - control loop composed of a power supply 1, a control relay 3, and a circuit breaker trip 2. The controller is used to send a control signal for the relay to act to the control relay. When the controller controls the control relay to disconnect, the open - circuit detection circuit forms a series loop with the power supply and the circuit breaker trip in the load - control loop. The current is limited by the current - limiting circuit and then rectified by the rectifier circuit. The rectified small current is stored by the energy storage and voltage - stabilizing circuit. When the energy reaches a certain threshold, the previously stored energy is released through the energy - release circuit to form an energy - release signal. The energy - release signal is converted into a level acceptable to the controller by the signal - conditioning circuit and is electrically isolated at the same time, and the level - pulse signal is sent to the controller. The controller determines the open - circuit state of the load - control loop by detecting the periodic level - pulse signal output by the signal - conditioning circuit. This process repeats continuously. Once the loop is open - circuited, the circuit cannot maintain a periodic charge - discharge, and the controller cannot detect a periodic level - pulse signal, so it can be determined that the control loop is open - circuited.

[0040] Such as Figure 2As shown in the figure, a method for detecting a broken wire in a load control loop includes the following steps: The controller detects whether the broken wire detection function of the load control loop is enabled. If it is not enabled, no broken wire detection is performed.

[0041] If the broken wire detection function of the load control loop is enabled, it is determined whether the control relay in the load control loop is closed. If the control relay is closed, no broken wire detection is performed.

[0042] If the control relay is open, the controller detects whether there is a periodic input level flip. If there is a periodic level flip, the load control loop is not broken. If no periodic level flip is detected, it is determined that the load control loop is broken.

[0043] Due to the limitation of the current in the control loop, the traditional scheme of directly detecting the loop state through an optocoupler is not feasible. Compared with the traditional scheme for detecting a broken wire in the loop, the circuit of the present invention adds a rectifier circuit, an energy storage and voltage stabilization circuit, and an energy release circuit. By reasonably configuring parameters, the control circuit charges and discharges periodically to generate a pulse signal recognizable by the controller, thereby realizing the detection of a broken wire in the load control loop under the condition of small current.

[0044] Embodiment:

[0045] A typical example of the implementation of this method is as Figure 3 shown in the figure. In the figure, the current limiting circuit is implemented by resistor R1, the rectifier circuit is a full-wave rectifier circuit composed of diodes D1 - D4, the energy storage and voltage stabilization circuit is composed of zener diode Z1 and energy storage capacitor C1, the energy release circuit is composed of zener diode Z2, transistors Q1 and Q2, resistors R2 and R3, and the signal conditioning circuit is composed of resistor R4 and optocoupler OP1.

[0046] When the relay switch of the dedicated transformer acquisition terminal is open, the power supply, the loop broken wire detection circuit, and the circuit breaker form a series loop. The power supply charges capacitor C1 through resistor R1, and the voltage across C1 gradually increases. The zener diode Z1 is used to limit the DC side voltage of the rectifier circuit within the designed range. After the voltage across C1 rises to a certain level, Z2 conducts, and then Q1 conducts. A forward conduction current flows through the primary side of the optocoupler OP1, and the level of the secondary side of the optocoupler flips; after Q2 conducts, Q1 conducts subsequently. Since the current flowing through transistor Q2 is much larger than the charging current in the control loop, capacitor C1 discharges, and the voltage in C1 continuously decreases. When the voltage across C1 drops to the breakdown voltage of Z2, Z2 turns off. As the discharge continues, finally Q1 turns off and Q2 turns off, and the circuit stops discharging, and the secondary side of the optocoupler flips again. The circuit enters the charging state, the voltage across C1 gradually rises, and then enters the next cycle.

[0047] When the load control loop is open-circuited, the voltage across C1 is zero at steady state, and the level of the secondary side of the optocoupler remains unchanged. By detecting the flip of the level of the secondary side of the optocoupler by the controller, it can be judged whether the loop is open-circuited. By controlling the size of the control resistor R1, the current in the control loop can be ensured to meet the requirements.

[0048] The above are only the preferred embodiments of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A disconnection detection circuit for a load control loop, characterized in that: Comprising: A current limiting circuit, a rectifying circuit, an energy storage and voltage stabilizing circuit, an energy release circuit, a signal conditioning circuit, and a controller; the current limiting circuit, the rectifying circuit, the energy storage and voltage stabilizing circuit, the energy release circuit, and the signal conditioning circuit are connected in series in sequence, and the output end of the signal conditioning circuit is connected to the signal input end of the controller; The current limiting circuit is used to limit the current in the open circuit detection loop to the microampere level; The rectifying circuit is used to convert the alternating current in the open circuit detection loop into direct current; The energy storage and voltage stabilizing circuit is used to store the energy in the open circuit detection loop; The energy release circuit is used to automatically release energy and generate an energy release signal when the energy in the energy storage and voltage stabilizing circuit reaches a certain threshold; The signal conditioning circuit is used to convert the energy release signal into a level pulse signal and transmit it to the controller; The controller is used to detect whether a periodic level pulse signal is received. If so, it is determined that the open circuit detection loop is normal. If not, it is determined that the open circuit detection loop is open.

2. The disconnection detection circuit for a load control loop according to claim 1, wherein: The current limiting circuit adopts a current limiting resistor.

3. The disconnection detection circuit for a load control loop according to claim 1, wherein: The rectifying circuit adopts a full-wave rectifying circuit.

4. The disconnection detection circuit for a load control loop according to claim 1, wherein: The energy storage and voltage stabilizing circuit consists of a charging capacitor and a first voltage stabilizing diode connected in parallel.

5. The disconnection detection circuit for a load control loop according to claim 1, wherein: The energy release circuit includes a first triode and a second triode. The emitter of the first triode is connected to one pole of the power supply of the open circuit detection loop. The collector of the first triode is connected to the base of the second triode through a first resistor. The base of the first triode is connected to the collector of the second triode. The emitter of the second triode is connected to the other pole of the power supply of the open circuit detection loop. A second voltage stabilizing diode is connected in parallel between the emitter and the collector of the first triode. The collector of the second triode is connected to the signal conditioning circuit.

6. The disconnection detection circuit of a load control loop according to claim 1, characterized in that: The signal conditioning circuit includes a second resistor and an optocoupler. One end of the second resistor is connected to the output end of the energy release circuit. The other end of the second resistor is connected to one end of the input end of the optocoupler. The other end of the input end of the optocoupler is connected to one pole of the power supply of the open circuit detection loop. One end of the output end of the optocoupler is connected to the positive pole of the voltage source through a third resistor. The other end of the output end of the optocoupler is connected to the negative pole of the voltage source. The connection between one end of the output end of the optocoupler and the third resistor is connected to the input end of the controller.

7. The disconnection detection method for the load control loop of the disconnection detection circuit according to any one of claims 1-6, characterized in that: Including the following steps: The controller detects whether the open circuit detection function of the load control loop is enabled. If it is not enabled, no open circuit detection is performed; If the open circuit detection function of the load control loop is enabled, it is determined whether the control relay in the load control loop is closed. If the control relay is closed, no open circuit detection is performed; If the control relay is open, the controller detects whether there is a periodic input level flip. If there is a periodic level flip, the load control loop is not open. If no periodic level flip is detected, it is determined that the load control loop is open.

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