CN107843807B

CN107843807B - Monitoring system capable of timely turning off power grid at voltage drop moment

Info

Publication number: CN107843807B
Application number: CN201610834951.8A
Authority: CN
Inventors: 张永
Original assignee: Fonrich Shanghai New Energy Technology Co ltd
Current assignee: Fonrich Shanghai New Energy Technology Co ltd
Priority date: 2016-09-20
Filing date: 2016-09-20
Publication date: 2021-07-30
Anticipated expiration: 2036-09-20
Also published as: CN107843807A

Abstract

The invention mainly relates to an electric power system, in particular to a power grid monitoring system with an electric arc detection function and a direct current value monitoring function, which monitors the current of each branch in a direct current system in real time and detects whether harmful electric arcs are generated in a direct current circuit in real time. In addition, when the power system has power failure or obvious large-amplitude voltage reduction, the protected power grid line is required to be powered off at the moment generally based on safety consideration.

Description

Monitoring system capable of timely turning off power grid at voltage drop moment

Technical Field

The invention mainly relates to an electric power system, in particular to a power grid monitoring system with an electric arc detection function and a direct current value monitoring function, which can monitor the current of each branch in the direct current system in real time and detect whether harmful electric arcs are generated in a direct current circuit in real time, and can timely turn off the power grid at the moment that the voltage drops due to power failure of the power grid, thereby ensuring the normal operation of the whole electric power system.

Background

In a power grid system, various accidents often occur to cause a rapid voltage drop, and a power failure or an obvious large-amplitude voltage drop of a power system belong to such accidents. But the main drawbacks of the current prior art are: the absence of a suitable battery backup for applying a defined voltage to the trip coil of the circuit breaker after a power failure, especially in electrical devices such as photovoltaic combiner boxes, results in an inability to quickly shut down the protected grid line at the instant of the power failure. The trip coil is wound on the magnetic core in the circuit breaker, once the trip coil generates magnetic force to enable the free trip mechanism to act, the main contact can be forced to break a circuit protected by the circuit breaker, but the trip coil of the circuit breaker can enable the magnetic core to generate enough adsorption force instantly only when the applied voltage reaches a certain degree in a short time, and if the voltage applied to the trip coil is insufficient, the circuit breaker is difficult to drive to execute the trip action to realize the opening. It is noted that the circuit breaker to which the present application refers is a common electrical switching apparatus in the art, and the function of the circuit breaker is described in detail in, for example, US9013852, etc., and thus the present application is considered to be a known art circuit breaker. In addition, the circuit breaker can be replaced by an electrical switch such as a relay with a coil winding, and an electrical switch that can satisfy repeated opening and closing operations of the protected power grid line is considered to be an object of the present application.

Also in modern power systems, in order to improve the reliability and safety of the grid, great efforts have been made to avoid negative arcs in the grid system. Arcing is an irregular and highly unstable phenomenon of high frequency variation, however, prior art effective monitoring of arcing still does not achieve a satisfactory solution. In an electrical power system, when a sufficiently high voltage differential is created between two electrodes, an arc may occur, the voltage causes gas ionization between the electrodes resulting in a plasma that may develop and current may flow between the electrodes, such a plasma potentially heating to several thousand degrees celsius until it causes equipment damage or fires that cause a fire. Potential arcs in power systems are of roughly two types: parallel arcs or series arcs. Parallel arcs typically occur between the positive and negative poles of a power system, or between one of the poles and ground. In contrast, serial arcs do not occur between two lines, but rather in a current-conducting line, and in order to reduce the negative effects of arcs, corresponding countermeasures such as switching off the arc source must be carried out as quickly as possible, so that reliable and real-time confirmation of arcs is a very important monitoring item. In some prior art solutions, some published patent documents also disclose various feasible arc detection circuits, for example, chinese patent applications CN200910109533.2, CN201410130412.7, etc., disclose arc detection solutions, but in special applications such as the field of photovoltaic bus, the arc detection effect is not good, and the present application has an additional function of detecting arcs.

Disclosure of Invention

The invention provides a monitoring system capable of timely switching off a power grid at the moment of voltage drop, which comprises a main control unit with a first power module and a processor, and a first capacitor; wherein

The first power module converts the voltage source supplied to it into an operating voltage supplied to the processor and into a redundant voltage stored on the first capacitor;

a trip coil of an electrical switch for controlling the connection or disconnection of the network line is excited by the redundant voltage, the electrical switch is triggered to switch to an off state when the trip coil is connected and the voltage applied to the trip coil is not lower than a threshold voltage, and a first switch controlled by a processor determines whether to apply the redundant voltage to the trip coil;

the processor generates a first command signal to instruct the first switch to turn on when detecting the power loss of the voltage source to a predetermined magnitude, so as to apply the redundant voltage to the trip coil to thereby drive the electrical switch to perform a turn-off action to disconnect the grid line.

The system further comprises an energy storage element and a boosting circuit, wherein the redundant voltage on the first capacitor charges the energy storage element in the normal time period when the power-down event does not occur in the voltage source; and

and at the moment when the power supply is powered down and exceeds a preset amplitude to generate a power-down event, the voltage on the energy storage element is boosted by the booster circuit and is reversely transmitted to the first capacitor.

In the above system, the first capacitor is connected between the first and second nodes, and the first power supply module outputs a voltage from the first and second nodes to the first capacitor; and

the energy storage element is connected between third and fourth nodes, and a diode has an anode connected to the first node and a cathode connected to the third node.

In the system, the processor generates a second instruction signal at the time of the power-down event of the voltage source to notify the voltage boosting circuit to start to capture the voltage on the energy storage element for boosting and outputting to the first capacitor.

In the system, the trip coil and the first switch are connected in series between the first node and the second node, and the trip coil is electrified when the first switch is switched on, so that the electrical switch is triggered to actively turn off the power grid line.

In the above system, the main control unit further includes a second power module, and the second power module is configured to extract a voltage from the first capacitor or the energy storage device and convert the voltage into a working voltage provided to the processor.

In the above system, the first capacitor is an electrolytic capacitor, and the energy storage element is a super capacitor or a lithium battery.

In the above system, starting from the starting time point of the power down event of the voltage source, before the redundant voltage on the first capacitor decreases below the minimum threshold voltage required for triggering the electrical switch to generate the turn-off action:

the voltage boost on the energy storage element is transmitted to the first capacitor for boosting the redundant voltage, so as to ensure that the redundant voltage is sufficient for driving the electrical switch to be switched off.

The system described above, providing a shunt in which one of the supply line of the voltage source and the grid line is the other; or the power distribution on one of the supply line providing the voltage source and the grid line is converted from the power distribution on the other using a voltage converter; or the power supply line and the grid line are independent lines.

The system also comprises a first detection unit for detecting the direct current in the branch circuit, wherein the first detection unit is provided with a Hall annular magnetic ring with an air gap and a Hall element;

the monitored branch passes through the annular magnetic ring, the output voltage of the Hall element reflects the size of the primary side current flowing through the branch in proportion, and the processor captures the direct current so as to realize the monitoring of the branch;

and a second switch is arranged on a line of the first power supply module for supplying power to the Hall element, and the processor sends a driving signal to turn off the second switch at the moment when the power failure event occurs to the voltage source, and the processor sends the driving signal to turn on the second switch until the voltage source recovers to the voltage level before the power failure.

The system described above, further comprising a second detection unit for detecting arc information in the branch, having a current sensor and a filter;

the current sensor detects current information on a monitored branch circuit, the filter detects and extracts a detection signal which has a preset frequency band range and is used for representing whether an electric arc exists or not from the current information in a band-pass filtering mode, and the processor captures the detection signal so as to realize the monitoring of the branch circuit;

and a third switch is arranged on a line for supplying power to the filter by the first power supply module, and the processor sends a driving signal to turn off the third switch at the moment when the power failure event occurs to the voltage source, and the processor does not send the driving signal to turn on the third switch until the voltage source recovers to the voltage level before the power failure.

Drawings

The features and advantages of the present invention will become apparent upon reading the following detailed description and upon reference to the following drawings:

fig. 1 is a schematic diagram of a first example of a monitoring system for timely power down of a power grid at the instant of power down.

Fig. 2 is a schematic diagram of a second exemplary monitoring system for timely power down of the power grid at the instant of power down.

Fig. 3 is a schematic diagram of a third exemplary monitoring system for timely power-off of the power grid at the instant of power failure in the present invention.

Detailed Description

Referring to fig. 1, the grid monitoring system capable of timely shutting down the grid at the moment of voltage drop in the present application at least includes a main control unit 100A having a first power module 110 and a processor 112, and a first capacitor C_ECThe first power module 110 may employ a DC-to-DC voltage converter, which is generally used in the art and mainly functions to perform conventional DC/DC voltage conversion for power distribution on the power supply lines LA and LB like a set of buses. In particular, the first power module 110 supplies the voltage source V to which the supply lines LA and LB are fed_SUPConverted to a stable voltage and provided to the processor 112 as the operating voltage of the latter, and the first power module 110 supplies the voltage source V_SUPIs converted into a signal stored in a first capacitor C_ECA backup or redundant voltage V_RED. That is, the first power module 110 needs to be at least the processor 112 and the first capacitor C_ECAnd (5) supplying power.

Referring to fig. 1, it is assumed that another group of grid lines LC and LD similar to the bus is a protected object, that is, when the power system is in a power failure or significantly drops the voltage greatly, the grid lines are required to be disconnected, otherwise, when the power supply is recovered after power failure, the devices and workers on the protected grid lines LC and LD may be accidentally injured. According to the safety requirements in the industry, the electric switch BRE needs to be arranged on the power grid lines LC and LD, and the electric switch BRE can be selected from various types and belongs to the prior art in the field, so that the details are not repeated in the application, and the main function of the electric switch BRE is to be capable of connecting or disconnecting the power grid lines LC and LD. Assuming that the electrical switch BRE has a trip coil 130, the trip coil 130 has the following functions in the industry: trip coil 130 is subjected to a redundant voltage V_REDThat means that the trip coil 130 needs to rely on a redundant voltage V_REDAs an excitation source, and the actual voltage applied to the trip coil 130 is not lower than a threshold voltage, the electrical switch BRE can be triggered to switch to the off state, so as to further cut off the grid lines LC and LD if the redundant voltage V is present_REDThe actual voltage value of (b) is too low, resulting in insufficient current density flowing through trip coil 130, and the electrical switch BRE may not be turned off. The electrical switch BRE is exemplified by a circuit breaker commonly seen in the industry, in which a trip coil 130 is wound on a magnetic core MAG, when the trip coil 130 is energized, the magnetic core MAG generates magnetic attraction, and then some trip mechanisms are guided by magnetic force to generate mechanical action, and further, a trip switch S connected to a grid line LC and a trip switch LD are driven_TRISwitching to an off state. The electrical switch BRE is further exemplified by a relay commonly used in the art, when the trip coil 130 is energized, the magnetic force generated by the magnetic core MAG adsorbs the armature spring of the relay to change the position thereof, and the armature spring also drives the tripBuckle switch S_TRIThe contact of (2) switches to the off state. Circuit breakers or relays or other similar electrically controlled switches are among the electrical switching elements that may be employed in the present application.

Referring to fig. 1, it is worth mentioning that if power distribution on the power supply lines LA and LB is lost, even if we intend to turn off the electrical switch BRE at the moment of the power loss event, unfortunately, the master control unit/module 100A may be due to the voltage source V_SUPFails to provide a suitable power supply mechanism for trip coil 130 such that the expected shutdown of electrical switch BRE is not accomplished in the face of a power down event. To solve this problem, at the voltage source V_SUPDuring normal periods when no power down event occurs, the first power module 110 continues to supply the voltage source V_SUPVoltage conversion is performed and stored in the first capacitor C_ECThe above. In an alternative example of fig. 1, the first capacitor C_ECIs connected to a first node N₁₁And a second node N₁₂Meanwhile, a path of voltage output by the first power module 110 passes through the first node N₁₁And a second node N₁₂To be a first capacitor C_ECAnd (6) charging. Even if the voltage source V is_SUPIn the event of transient power failure, the first capacitor C_ECThe amount of power retained can still be used briefly as a backup battery.

Referring to FIG. 1, the processor 112 is provided with a sense voltage source V_SUPFunction of power-down, as in the prior art, e.g. voltage source V_SUPAlthough the voltage source V may alternatively be provided by a voltage divider providing a divided voltage to a voltage sensing port of the processor 112_SUPThe voltage value provided by the first power module 110 after voltage conversion is used as a voltage detection port for the processor 112, and the processor 112 receives the voltage value for representing the voltage source V_SUPThe voltage value of the magnitude is compared with a preset reference voltage, if the voltage value represents V_SUPIs lower than the reference voltage, a true power down event is deemed to have occurred. It has to be noted that the processor 112 is only detecting the voltage source V_SUPThe actual power-down amplitude exceeds a preset amplitude value, the real power-down is considered to exist, and the voltage source V_SUPThe slight fluctuation of the voltage does not cause the malfunction of the BRE of the electric appliance, namely the voltage source V_SUPThe magnitude or degree of power loss to which a valid power loss event is calculated can be adjusted to represent V_SUPIs compared with a reference voltage value.

Referring to fig. 1, a voltage source V_SUPWhen the falling amplitude exceeds the preset amplitude value, the processor 112 determines that the power-down event occurs and the processor 112 generates a first command signal S in a transient state therewith_COM1(e.g., high-low logic level) to indicate the first switch S_SUPSwitching on, tripping coil 130 and first switch S_SUPIs connected in series at a first node N₁₁And a second node N₁₂In the first switch S_SUPWhen switched on means that the redundant voltage V can be switched on_REDIs applied to the trip coil 130, so that the redundant voltage V_REDWhich corresponds essentially to an excitation for generating the trip current. As soon as the trip coil 130 is energized and as long as the voltage applied to the trip coil 130 is the same, i.e. the redundant voltage V_REDThe actual value of (c) is not lower than a threshold voltage, the current density flowing through trip coil 130 may cause magnetic core MAG to generate a sufficiently strong magnetic force to push electrical switch BRE to perform the turn-off operation. Otherwise if the redundant voltage V is_REDToo low (below the threshold voltage) may not successfully drive the electrical switch BRE off because the current density of trip coil 130 is not as desired.

With reference to fig. 1, consider a voltage source V_SUPThe potential drop to zero is such that the first power module 110 can no longer retrieve V_SUPInto the operating voltage of the processor 112. At the same time, the processor 112 still needs to issue a similar first instruction signal S even if there is a power down event_COM1Such signals, the source of the operating voltage of the processor 112 after a power down event is one of the issues that we need to consider. The operating voltage required by the processor 112 is not high, unlike the trip coil 130, which has a certain requirement for the magnitude of the applied voltage, so that the main control unit 100A can meet the requirement for supplying power to the processor 112 only by a small-capacity and small-volume backup battery. At one isIn an alternative embodiment, without any additional battery backup, the main control unit 100A further includes a second power module 111, and the second power module 111 may be a dc-dc voltage converter, which is commonly used in the art and mainly functions as a first node N₁₁And a second node N₁₂To a redundant voltage V_REDConventional DC/DC voltage conversion is performed and provided to the processor 112 as an operating voltage. The second power module 111 may continuously supply power to the processor 112, that is, the second power module 111 may provide stable voltage no matter whether a power down event occurs, or alternatively, the second power module 111 may supply power to the processor 112 only after the power down event occurs, and the voltage conversion role of the second power module 111 is stopped in a regular time period when the power down event does not occur, at this time, the processor 112 needs to send an indication signal to the second power module 111 at the power down instant to inform the second power module 111 to rapidly switch to the redundant voltage V in time_REDAnd carrying out voltage conversion.

See fig. 2, although the first capacitor C_ECCan provide a redundant voltage V_REDTo trigger the energization of trip coil 130 induces magnetic core MAG to generate sufficient magnetic force to push electrical switch BRE open, but once voltage source V is applied_SUPPower down of the first capacitor C_ECThe power is lost so that its charge does not generally last long, and it is likely that its charge will drop short enough to drive the electrical switch BRE open. To overcome this problem, fig. 2 also utilizes another energy storage element 140 and a voltage boost circuit 120, at the voltage source V_SUPThe first capacitor C is used for the normal time period when the power-down event does not occur_ECA redundant voltage V on_REDCharging the energy storage element 140, and at a voltage source V_SUPWhen the power is lost to a level exceeding a predetermined level to determine a real power loss event, the voltage of the energy storage element 140 starts to be boosted by a BOOST circuit (BOOST)120 and is reversely transmitted to the first capacitor C_EC。

Referring to FIG. 2, for example, the energy storage element 140 is connected to the third node N₂₁And a fourth node N₂₂Another second capacitor C in between_BAT. To achieve a period of no power down on the first capacitor C_ECCharging the energy storage element 140 but reversing the energy storage element 140 to the first capacitor C after a power down event_ECFor charging purposes, an anode of a diode D is connected to a first node N₁₁And the cathode of the diode D is connected to the third node N₂₁Wherein the second node N₁₂And a fourth node N₂₂Both may be equipotential, and they may for example be connected to the reference ground potential of the entire detection system. A set of voltage input terminals of the voltage boosting circuit 120 are respectively coupled to the third node N₂₁And a fourth node N₂₂And a set of voltage output terminals of the boosting circuit 120 are respectively coupled to the first node N₁₁And a second node N₁₂. Wherein, the second capacitor C is used for the front stage of the voltage boost circuit 120_BATAnd C on the first capacitor of the subsequent stage_ECIn other words, the first capacitor C_ECRelative to the second capacitor C_BATShould have more sufficient voltage endurance and higher speed instantaneous discharge capability, and the second capacitor C_BATRelative to the first capacitor C_ECIt is desirable to have better energy and power densities. In alternative embodiments, the second capacitor C may be charged quickly, although both the first and second capacitors may be charged quickly_BATOpposite to the first capacitor C_ECFor example, the former is typically tens of seconds below the minimum threshold required to power down sufficiently to drive the trip coil to turn off the trip switch, and the latter is typically only about ten seconds or even a few seconds below the minimum threshold required. By way of example, but not by way of any particular limitation, the second capacitor C_BATA super-capacitor (ultra-capacitor) may be used and the first capacitor C_ECAn electrolytic capacitor (electrolytic capacitor) may be used.

Referring to fig. 2, the voltage endurance is a weak link of the super capacitor, which is based on the dielectric material, and the dielectric in the super capacitor is particularly thin and is only in the order of nanometers, so that a large surface area can be generated to form a larger capacity,these very thin layers, however, do not have the desirable insulating properties of conventional dielectrics and therefore require lower operating voltages. As an example, the second capacitor C_BATIt may be replaced by a lithium battery, and when the energy storage element 140 is a lithium battery, the anode of the battery is connected to the third node N₂₁And the negative pole of the battery is connected to the fourth node N₂₂. The first capacitor C if there is no continuous supply of electrical energy_ECWill fall to a point where it is completely impossible to activate the trip coil 130, in a matter of seconds, and the second capacitor C_BATAlthough it loses its charge quickly, its charge decreases at a much slower rate than the first capacitor C_ECBased on the use of a second capacitor C_BATAnd a first capacitor C_ECThe respective power loss rates are different, and one of the purposes to be achieved by the present application is from the voltage source V_SUPStarting from the initial point in time of the occurrence of the power down event to the first capacitor C_ECActual redundant voltage V on_REDBefore dropping below the minimum threshold voltage required to trigger the electrical switch BRE to produce the switch-off action: the voltage on the energy storage element 140 is boosted by the above-mentioned boosting circuit 120 and transmitted to the first capacitor C_ECUpper for raising the actual redundant voltage V_REDTo ensure the redundant voltage V_REDSufficient to drive the electrical switch off. It is noted that the boost circuit 120 does not operate during the normal period when no power down event occurs, and it starts from the third node N only after the power down event occurs₂₁And a fourth node N₂₂The voltage on the energy storage device 140 is captured as an input, and boosted from the first node N₁₁And a second node N₁₂Is output to the first capacitor C_ECAt both ends of the same. According to this solution, even the first capacitor C_ECLoss of voltage source V_SUPAnd also self-power-down at the same time to cause redundant voltage V_REDDecreased, but redundant voltage V due to the charge of boost circuit 120_REDNor does it fall too quickly.

Referring to fig. 2, the starting time points of the boost circuit 120 performing the DC-DC boost operation are: at a voltage source V_SUPTime of occurrence of power down event, departmentThe processor 112 generates a second command signal S_COM2The boosting circuit 120 is informed to start to extract the voltage on the energy storage device 140 for boosting and outputting to the first capacitor C_ECThe above. The second power supply module 111 may be powered from the first node N₁₁And a second node N₁₂To a redundant voltage V_REDPerforms conventional DC/DC voltage conversion and provides the same to the processor 112 as an operating voltage or from the third node N₂₁And a fourth node N₂₂The voltage across the extracted energy storage device 140 is converted to a conventional DC/DC voltage and provided to the processor 112 as the operating voltage.

Referring to FIG. 1, the processor 112 detects the voltage V_SUPThe power distribution of the power supply lines LA and LB is not a power failure event, but the power supply lines LC and LD are the objects protected by the electrical switch BRE. In some alternative embodiments, the power supply lines (LA-LB) and the grid lines (LC-LD) may be independent lines with respect to each other. In other alternative embodiments, there is a partial coupling relationship between the power supply lines LA and LB and the grid lines LC and LD, such as: one of the power supply lines (LA-LB) and the grid lines (LC-LD) may be a bypass or branch circuit of the other, or the power distribution on one of the power supply lines (LA-LB) and the grid lines (LC-LD) is converted from the power distribution on the other by means of a voltage converter. In fig. 1, the grid lines LC to LD are used as an example of a voltage converter 150 which converts the power distribution on it into power distributions on the supply lines LA to LB, for example, the voltage converter 150 is an ac-to-dc voltage converter or a dc-to-dc voltage converter, and may be a step-up conversion or a step-down conversion.

In the application occasions such as photovoltaic combiner box, direct current cabinet, telecommunications room, communication base station in the electric power industry, each branch current in the real-time supervision direct current system with whether have harmful electric arc to produce in the real-time detection direct current circuit, in case there is harmful electric arc, need send alarm signal drive trip gear on the circuit breaker at once, cut off the trouble return circuit, effectively prevent potential safety hazards such as conflagration that electric arc arouses. In the power grid monitoring system provided by the present application, the power grid monitoring system further includes a first detecting unit 100B for detecting a direct current and a second detecting unit 100C for detecting arc information, and the processor 112 retrieves a current value measured by the first detecting unit 100B and the arc information detected by the second detecting unit 100C, thereby implementing monitoring of the power grid.

Referring to fig. 3, the first sensing unit 100B includes a Hall ring-shaped magnetic ring 115 with an air gap and a Hall element (Hall component)116, and an Open Loop Hall current sensor (Open Loop Hall Effect) is applied to the first sensing unit 100B. The line LIN passes through the annular magnetic ring 115, the Hall element 116 measures the magnetic field generated in the annular magnetic core 115 and amplifies the output, and the output voltage V of the Hall element 116_HALLProportionally reflecting the primary direct current I flowing through the line LIN_PRIThe size of (2). The main working principle of the mutual cooperation of the annular magnetic ring 115 and the hall element 116 is as follows: when primary side current I_PRIWhen a long conductor of the line LIN is passed, a magnetic field is generated in the annular magnetic core 115, the magnitude of which corresponds to the current I flowing through the conductor LIN_PRIIn proportion, the generated magnetic field is concentrated in the toroidal core 115, and the intensity of the magnetic field is measured and amplified by the hall element 116 disposed in the air gap of the toroidal core 115, and thus the voltage V output from the hall element 116 is output_HALLAnd primary side current I_PRIIn a direct proportional relationship. The processor 112 is used for receiving the voltage V output by the Hall element 116_HALL。

Referring to fig. 3, the second sensing unit 100C includes an air coil sensor 117 and a filter 118. The air coil sensor 117 used in this application is used to detect various components of the current information in the line LIN, the air coil sensor 117 is not structurally configured with a magnetic core containing ferromagnetic material, such as a hall current sensor, and its coil is wound on a flexible or rigid frame serving as a physical support to form a toroidal winding, which is not a magnetic core so that the air coil has no hysteresis effect and no phaseBit errors and magnetic saturation phenomena. The theoretical basis of the air-core coil sensor 117 is faraday's law of electromagnetic induction and ampere's loop law, and when the load current of the line LIN passes through the center of the coil of the air-core coil sensor 117 along the axis, a correspondingly changing magnetic field is generated within the volume surrounded by the annular winding structure of the coil of the air-core coil sensor 117, and an induced voltage U is generated across the coil₁(t) M x (di/dt), voltage U₁(t) is proportional to the differential equation of the alternating current i to be measured, varying with time t, M being the mutual inductance of the coil windings. The wide response bandwidth of the air-core coil sensor 117 is advantageous in that it ensures that high frequency harmonics, such as those with spike components, are accurately detected, and that conventional spike harmonics can be captured without loss of accuracy. The band-pass filter 118 detects and extracts a detection signal with a predetermined frequency band range from the current information sensed by the sensor 117, and the processor 120 extracts the detection signal to implement arc monitoring of the branch circuit. If the processor 120 determines that a fault arc has occurred in the monitored line LIN, it may also issue another command signal to inform the first switch S_SUPTurning on further induces the electrical switch BRE to turn off. Likewise, line LIN may be a bypass or branch circuit of grid lines LC to LD, or the distribution on line LIN is converted from the distribution on grid lines LC to LD by means of a voltage converter.

Referring to fig. 3, in an optional embodiment, a second switch S is disposed on the line of the first power module 110 for supplying power to the hall element 116_DECOnly when the second switch S is present_DECThe first power module 110 can supply power to the hall element 116 when the first power module is turned on, otherwise the second switch S_DECWhen turned off, power cannot be supplied to the hall element 116. At a voltage source V_SUPAt the time of the power down event, the processor 112 sends a driving signal to turn off the second switch S_DECTo protect the safety of the first detection unit 100B and reduce the overall power consumption in this stage until the voltage source V_SUPThe processor 112 sends a driving signal to turn on the second switch S when the voltage level before the power failure is recovered_DEC. In an optional, non-necessary embodiment, a third switch S is provided in the line supplying the filter 118 from the first power module 110_ARCOnly when the third switch S_ARCThe first power module 110 can supply power to the filter 118 when it is turned on, whereas the third switch S_ARCWhen turned off, the filter 118 cannot be powered. At a voltage source V_SUPAt the time of the power down event, the processor 112 sends a driving signal to turn off the third switch S_ARCTo protect the safety of the second detection unit 100C and reduce the overall power consumption at this stage until the voltage source V_SUPThe processor 112 sends a driving signal to turn on the third switch S only when the voltage level before the power failure is recovered_ARC. In some alternative embodiments, the second switch S_DECAnd a third switch S_ARCBoth of the first detecting unit 100B and the second detecting unit 100C are optional, that is, they are discarded from the power supply lines and directly powered by a similar power supply module, such as the first power module 110 or the second power module 111.

While the present invention has been described with reference to the preferred embodiments and illustrative embodiments, it is to be understood that the invention as described is not limited to the disclosed embodiments. Various alterations and modifications will no doubt become apparent to those skilled in the art after having read the above description. Therefore, the appended claims should be construed to cover all such variations and modifications as fall within the true spirit and scope of the invention. Any and all equivalent ranges and contents within the scope of the claims should be considered to be within the intent and scope of the present invention.

Claims

1. A monitoring system capable of timely switching off a power grid at the moment of voltage drop is characterized by comprising a main control unit with a first power module and a processor, and a first capacitor; wherein

a trip coil of an electrical switch for controlling the connection or disconnection of the network line is energized by the redundant voltage, the electrical switch is triggered to switch to an off state when the trip coil is energized and the voltage applied thereto is not lower than a threshold voltage, and a first switch controlled by the processor determines whether to apply the redundant voltage to the trip coil;

the processor generates a first command signal to instruct the first switch to turn on when detecting that the voltage source is powered down to a preset amplitude, so as to apply the redundant voltage to the trip coil to push the electrical switch to perform a turn-off action to disconnect the grid line;

the power supply also comprises an energy storage element and a booster circuit, and the redundant voltage on the first capacitor charges the energy storage element in the normal time period when the power failure event does not occur in the voltage source; when the voltage source is powered down and exceeds a preset amplitude to generate a power-down event, the voltage on the energy storage element is boosted through the boosting circuit and is reversely transmitted to the first capacitor;

the first capacitor is connected between first and second nodes, and the first power supply module outputs a voltage from the first and second nodes to the first capacitor; and said energy storage element is connected between third and fourth nodes, a diode having an anode connected to said first node and a cathode connected to said third node;

when the power-down event of the voltage source occurs, the processor generates a second instruction signal to inform the voltage boosting circuit to start to capture the voltage on the energy storage element for boosting and outputting to the first capacitor;

the first capacitor is an electrolytic capacitor, the energy storage element is a super capacitor, the respective rates of loss of electric quantity of the energy storage element and the first capacitor are different, and the rate of decrease of the electric quantity of the energy storage element is lower than that of the first capacitor.

2. The system of claim 1, wherein the trip coil is connected in series with the first switch between the first and second nodes, the trip coil being energized when the first switch is closed thereby triggering the electrical switch to actively shut off the grid line.

3. The system of claim 1, wherein the master control unit further comprises a second power module for extracting voltage from the first capacitor or the energy storage device and converting the voltage to an operating voltage for the processor.

4. The system of claim 1, wherein from a starting point in time when a power down event occurs in the voltage source, before the redundant voltage on the first capacitor drops below a minimum threshold voltage required to trigger the electrical switch to produce a turn off action:

5. The system according to claim 1, characterized in that a shunt is provided of one of the supply line of the voltage source and the grid line being the other; or

The power distribution on one of the supply line providing the voltage source and the grid line is converted from the power distribution on the other using a voltage converter; or the power supply line and the grid line are independent lines.

6. The system as claimed in any one of claims 1 to 5, further comprising a first detecting unit for detecting the DC current in the branch, which has a Hall ring magnetic ring with an air gap and a Hall element;

7. The system according to any one of claims 1 to 5, further comprising a second detection unit for detecting arc information in the branch, having a current sensor and a filter;