Micro - current Apparent Power Sensing Method and Device

Abstract

The present invention discloses a micro-current apparent power sensing method and device, belonging to the technical field of electromagnetic measurement, which includes the following steps: Step S1: Detect the micro-current on the grounding wire, the grounding lead of the insulating part or the zero-sequence current line to obtain the current on the corresponding line; Step S2: Collect the micro-current detected in Step S1, and then multiply it by the pre-judged given apparent voltage to obtain the apparent power; Step S3: Accumulate the apparent power obtained in Step S2 in real time to obtain the apparent electricity quantity. This method can convert the small grounding current, insulation or leakage current into the form of apparent electricity quantity accumulated over time, so that it can be considered within a time period, understand the change trend of the power destruction force through the current, facilitate the adoption of necessary safety inspection measures, avoid disorderly power outages, and lay a power foundation for ensuring normal production.

Description

Technical Field

[0001] The present invention belongs to the technical field of electromagnetic measurement, and particularly relates to a method and device for sensing apparent power of micro-current. Background Art

[0002] Since the late 1960s in China, in order to strengthen electrical safety, protection measures have been gradually adopted in the power system, and the leakage protector is a common technical means. The leakage protector detects abnormal current or voltage signals of monitored equipment or lines. When the detected signal reaches its set threshold, it prompts the actuator to operate and cut off the power supply, avoiding accidents such as burning out electrical appliances, fires or electric shocks, so as to ensure the safety of personnel and electrical equipment and achieve the purpose of protection.

[0003] Later, there is also a method of small current grounding. An zero-sequence current transformer is installed at the incoming line end of high-voltage equipment (i.e., the outgoing line side of the high-voltage switch), and the secondary side of the current transformer is connected to a small current grounding line selection device. When one-phase grounding or two-phase grounding occurs in the high-voltage equipment loop, an unbalanced current will be generated in this loop. The current transformer detects the unbalanced current and transmits it to the small current grounding line selection device. The small current grounding line selection device gives a tripping signal to make the high-voltage switch trip and disconnect the high-voltage equipment from the power grid, avoiding the high-voltage equipment from being burned and at the same time avoiding expanding the fault range through the power grid.

[0004] The above protection measures all belong to the category of post-protection. Only when the destructive energy of the current develops to a certain extent and reaches the protection threshold will they act. It is a method of starting protection only through power outage, and it cannot detect the development process of the current, prevent and deal with it in advance without affecting safety to hinder its development, or even eliminate the fault in its infancy. And once the protection threshold is reached, sudden power outage will occur, bringing serious hidden dangers to production and life, especially for equipment involving people, such as elevators, transportation and entertainment equipment.

[0005] In reality, the grounding current, insulation current or leakage current is usually very small, sometimes there and sometimes not, suddenly large and suddenly small, extremely unstable, making the measured value unable to truly reflect the destructive power in the power system, resulting in the long-term problem that has always affected the safe operation of the power grid and seriously affected the power supply quality. Therefore, it is necessary to develop a new detection technology that can reflect the change of destructive energy, so as to take safety inspection measures in time, then avoid disorderly power outages, achieve safe and energy-saving production, and reduce waste. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a micro-current apparent power sensing method and device, which can convert the grounding, insulation or leakage current into the form of apparent power accumulated over time, so that it can be considered within a time period, and then the change trend of the destructive energy on the line can be judged.

[0007] To solve the above technical problem, the technical solution of the present invention is: to design a micro-current apparent power sensing method, which is characterized in that it includes the following steps:

[0008] S1: Detect the current on the grounding wire, the grounding lead of the insulation part or the zero-sequence current line to obtain the current on the corresponding line;

[0009] S2: Collect the current detected in S1, and then multiply it by a given apparent voltage to obtain the apparent power;

[0010] S3: Accumulate the apparent power obtained in S2 in real time to obtain the apparent power consumption.

[0011] Preferably, the step S1 is completed by a current transformer. Before the detection in S1, the magnetic core of the current transformer is demagnetized.

[0012] Preferably, the current sampling circuit is used to collect the current in step S1.

[0013] Preferably, the apparent voltage is a set value or a voltage supply circuit.

[0014] Preferably, the value range of the apparent voltage is 1-20V.

[0015] The present invention also provides a power sensor for specifically implementing the above method, including a current sensor, which is used to detect the current on the grounding wire, the grounding lead of the insulation part or the zero-sequence current line to obtain the current on the corresponding line. It is characterized in that it further includes a current sampling circuit and an arithmetic unit.

[0016] The current sampling circuit collects the detected current of the current sensor;

[0017] The arithmetic unit multiplies the current collected by the current sampling circuit by a given apparent voltage to obtain the apparent power, and accumulates the apparent power in real time to obtain the apparent power consumption.

[0018] Preferably, a demagnetizing winding is wound on the magnetic core of the current transformer. The demagnetizing winding is connected to a demagnetizing power supply through a first switch, and a second switch interlocked with the first switch is arranged in the acquisition circuit of the sampling circuit.

[0019] Preferably, the on-off states and on-off times of the first switch and the second switch are controlled by a single-chip microcomputer.

[0020] Preferably, the apparent voltage is a given set value or the given voltage provided by a voltage setting circuit, and the arithmetic unit samples the given voltage.

[0021] Preferably, the numerical range of the apparent voltage is 1 - 20V.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] 1. After using a current sensor to sample the grounding, insulation or leakage current and multiplying it by the given apparent voltage to form apparent power, and accumulating the apparent power over time into the form of apparent electricity, the change amplitude within two adjacent time periods of the same length can be viewed, thereby reflecting the change trend of the destructive energy such as grounding, insulation or leakage, facilitating the adoption of necessary safety inspection measures, avoiding the sudden tripping and power-off caused by the current reaching the threshold in the prior art, and thus laying a power foundation for ensuring normal production.

[0024] 2. Since this apparent power sensor converts the small current into the form of apparent electricity that changes over time, on the one hand, it can overcome the drawbacks of easy misjudgment due to unstable current or potential hazards caused by too small current that cannot be detected; on the other hand, it avoids the false reflection caused by instantaneous determination and increases the number of unnecessary sudden power-offs; in addition, it can also master the development trend of the destructive energy, so as to adopt on-line power-off-free disposal or planned power-off disposal to ensure safe production, avoid waste of raw materials and reduce losses.

[0025] 3. Since the given apparent voltage adopts the method of a DC voltage divider circuit in the prior art, the technology is mature, the performance is stable and reliable, and it is easy to implement.

[0026] 4. Since the apparent voltage is estimated according to on-site conditions such as grounding resistance and application location and can be adjusted according to changes in on-site conditions, and its numerical range is generally 1 - 20V, after adopting this apparent voltage, the detected tiny current can be converted into the form of apparent electricity reflecting the destructive energy within a time period, truly reflecting the destructive ability of the grounding current, insulation level and leakage current on the power system.

[0027] 5. Since a demagnetizing winding is wound on the magnetic conductive core of the current transformer, the demagnetizing winding is connected to a demagnetizing power supply through a first switch, and a second switch interlocked with the first switch is provided in the acquisition loop of the sampling circuit, realizing the interlocked control of the demagnetizing loop and the acquisition loop, and the residual magnetism in the magnetic conductive core caused by instantaneous impulse current such as lightning strike can be removed after timing or after clearing the fault, restoring the magnetic conductivity of the magnetic conductive core and improving the accuracy of current detection.

[0028] 6. The sensing device of the present invention can be arranged on the grounding wire to detect the leakage current, or on the zero-sequence current line to detect the leakage current, or on the grounding lead of the equipment insulation part to detect its insulation level. It can be applied to high and low voltage AC and DC lines, and the application scenarios are flexible and diverse.

[0029] 7. The present invention breaks through the conventional protection method and proposes a new method of active detection and monitoring of the change process. It reflects the change trend of the destructive energy through the apparent electric quantity, so as to do a good job in pre-event safety inspection, take measures according to the situation, contain the development trend of the destructive energy, avoid sudden power outage, thus conforming to the construction of the ubiquitous power Internet of Things and facilitating popularization and application in this field. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is the structural schematic diagram of the present invention Figure 1 ;

[0031] Figure 2 is the structural schematic diagram of the present invention Figure 2 .

[0032] Reference numerals in the figure: 1. Current transformer; 2. Current sampling circuit; 3. Single-chip microcomputer; 4. Voltage dividing circuit; 5. Demagnetizing power supply; 6. First switch; 7. Demagnetizing winding; 8. Second switch. DETAILED DESCRIPTION OF THE INVENTION

[0033] The present invention will be further described in detail below in conjunction with the drawings and the specific embodiments.

[0034] The main idea of the present invention is as follows: Use a current detection device to detect the current on the grounding wire, zero-sequence current line or grounding lead of the insulation part of the equipment. After collecting the detected current, multiply it by a given apparent voltage to form apparent power, accumulate the apparent power to obtain apparent electric quantity, and then read the apparent electric quantity once every time interval of the same duration. Check the change amount of the apparent electric quantity in the same time period. If the change amount of the apparent electric quantity in each time period does not change significantly and is basically in a stable state of being flat, it indicates that the destructive force on the line has no obvious change, and continue to maintain the above time interval to read the apparent electric quantity and check the change amount of the apparent electric quantity; if the change range of the apparent electric quantity reaches a certain degree, take the way of alarming or reporting the information to the host computer to notify the staff to take safety inspection measures in time, find out the reason for the change of the change amount of the apparent electric quantity, do pre-event treatment, contain the development trend of the increasing current, so as to avoid sudden tripping due to reaching the protection threshold.

[0035] To achieve the above idea, the specific detection method is as follows:

[0036] S1: Detect the current on the grounding wire, the grounding lead of the insulation part or the zero-sequence current line to obtain the current on the corresponding line;

[0037] S2: The current sampling circuit 2 samples the current detected by S1, and then multiplies it by the given apparent voltage to obtain the apparent power.

[0038] S3: The apparent power obtained in S2 is cumulatively calculated in real time to obtain the apparent electricity quantity.

[0039] As Figure 1 and Figure 2 shown, in the power sensor provided by the present invention, the current transformer 1 is used to detect the current on the ground wire, the grounding lead of the insulating part or the zero-sequence current line, and obtain the current on the corresponding line.

[0040] The current sampling circuit 2 samples the detected current of the current transformer 1.

[0041] The arithmetic unit multiplies the current sampled by the current sampling circuit 2 by the given apparent voltage to obtain the apparent power, and cumulatively calculates the apparent power in real time to obtain the apparent electricity quantity. The arithmetic function of the arithmetic unit is completed by using the single-chip microcomputer 3.

[0042] In order to prevent the sudden current from leaving residual magnetism in the magnetic core of the current transformer 1, changing the magnetic permeability of the core and affecting the accuracy of its current measurement, the present invention also winds a demagnetizing winding 7 on the magnetic core of the current transformer 1. The demagnetizing winding 7 is connected to a demagnetizing power supply 5 through a first switch 6, so that the current in the demagnetizing winding 7 rises and falls slowly alternately and finally gradually returns to zero. A second switch 8 interlocked with the first switch 6 is provided in the acquisition loop of the current sampling circuit to realize the interlocked control of the demagnetizing loop and the acquisition loop. The on-off states and on-off times of the first switch 6 and the second switch 8 are controlled by the single-chip microcomputer. The magnetic core can be demagnetized after a fixed time or after clearing a fault to restore the magnetic permeability of the magnetic core, thereby improving the accuracy of current detection.

[0043] The working process of the present invention is as follows:

[0044] During use, the current transformer 1 is connected to the ground wire, the grounding lead of the insulating part or the zero-sequence current line to detect the current on the corresponding line. The current sampling circuit 2 samples the detected current, and then the arithmetic unit multiplies the sampled current by the given apparent voltage to obtain the apparent power; the obtained apparent power is cumulatively calculated in real time to obtain the apparent electricity quantity. In this way, the change amount of the apparent electricity quantity can be viewed in two adjacent time periods of the same length. If the change amount is stable, it indicates that the current in the line is stable; if the change amount increases, it indicates that the current in the line increases, thereby reflecting the change of the current and understanding the development process of this destructive force of the current, so as to take corresponding measures.

[0045] It is also possible to apply an alternating current with a slow rise and a slow fall alternately in the demagnetizing winding 7 at regular intervals or after the security inspection of the staff, and finally gradually return to zero to demagnetize the ferromagnetic core, thereby improving the detection accuracy of the current transformer 1.

[0046] In the above embodiment, the given voltage can be in the form of a digital signal with a set value, or can adopt the analog signal mode of the DC voltage divider circuit 4, which is estimated according to on-site conditions such as the grounding resistance and the application position. Specifically, it can be pre-judged by the method of multiplying the known grounding resistance by the measured current value, and can be adjusted according to the change of on-site conditions. Its value range is generally 1-20V. After adopting this apparent voltage, the detected tiny current can be converted into the form of apparent electric quantity reflecting the damage energy within a time period, truly reflecting the damage ability of the grounding current, insulation level and leakage current to the power system; it also plays a corresponding degree of amplification effect on the detected current, improving the situation that the change is not obvious due to the very small detected current, improving the detection accuracy, and facilitating the early adoption of security inspection measures.

[0047] The present invention can detect the grounding current on the grounding wire and the current on the grounding lead of the insulated part of the equipment, such as Figure 1 shown, the detection line on the left is the grounding wire or the grounding lead; it can also detect the leakage current of the zero-sequence current line, that is, the differential current in the incoming and outgoing circuits, such as Figure 2 shown, and the application scenarios are flexible and diverse.

[0048] Of course, it is also possible to use current sensors based on other measurement principles other than current transformers, so that the present invention can be used for the detection of high-voltage and low-voltage DC lines and high-voltage and low-voltage AC lines. The above current sampling circuit 2 is already a mature existing technology and will not be elaborated in detail here.

[0049] The above is only a preferred embodiment of the present invention, and it is not a limitation of the present invention in other forms. Any person skilled in the art may use the disclosed technical content to make changes or modifications into equivalent embodiments with equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the technical solution content of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A micro-current apparent power sensing method, characterized in that: Including the following steps: S1: Detect the current on the grounding wire, the grounding lead of the insulating part or the zero-sequence current line to obtain the current on the corresponding line; S2: Collect the current detected in S1, and then multiply it by a given apparent voltage to obtain the apparent power, where the apparent voltage is a set value or a voltage supply circuit; S3: Cumulatively calculate the apparent power obtained in S2 in real time to obtain the apparent electricity quantity; During application, read the apparent electricity quantity once every time interval of the same duration, and reflect the change trend of the damage energy such as grounding, insulation or leakage through the change amplitude of the apparent electricity quantity within two adjacent time periods of the same duration.

2. The micro-current apparent power sensing method according to claim 1, wherein: Step S1 is completed by a current transformer. Before the detection in S1, demagnetize the magnetic core of the current transformer.

3. The micro-current apparent power sensing method according to claim 2, characterized in that: The current sampling circuit is used to collect the current in step S1.

4. The micro-current apparent power sensing method according to any one of claims 1 to 3, characterized in that: The value range of the apparent voltage is 1 - 20V.

5. A micro-current apparent power sensing device, comprising a current sensor, the current sensor being used to detect the current on the ground wire, the grounding lead of the insulating part or the zero-sequence current line to obtain the current on the corresponding line, characterized in that: It also includes a current sampling circuit and an arithmetic unit, The current sampling circuit collects the detected current of the current sensor; The arithmetic unit multiplies the current collected by the current sampling circuit by a given apparent voltage to obtain the apparent power, and cumulatively calculates the apparent power in real time to obtain the apparent electricity quantity; the apparent voltage is a given set value or the given voltage provided by the voltage supply circuit, and the arithmetic unit samples the given voltage.

6. The micro-current apparent power sensing device according to claim 5, characterized in that: The current sensor is a current transformer, and a demagnetizing winding is wound on the magnetic core of the current transformer. The demagnetizing winding is connected to a demagnetizing power supply through a first switch, and a second switch interlocked with the first switch is arranged in the acquisition loop of the sampling circuit.

7. The micro-current apparent power sensing device according to claim 6, characterized in that: The on-off states and on-off times of the first switch and the second switch are controlled by a single-chip microcomputer.

8. The micro-current apparent power sensing device according to any one of claims 5 to 7, characterized in that: The value range of the apparent voltage is 1 - 20V.

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