CN101813756A - Method for manufacturing transient high-frequency magnetic field of power system - Google Patents

Abstract

The invention provides a method for measuring a transient high-frequency magnetic field of a power system. In the method, a measuring coil is directly closed so that the current and the magnetic induction intensity in the measuring coil form a linear relation; and the measuring coil and a coil of a current probe are magnetically coupled by a magnetic ring. The method can be used for measuring a sine steady magnetic field, particularly the transient high-frequency magnetic field and be widely applied to the measurement of the transient high-frequency magnetic field in the electromagnetic environment, specially the environment having strong magnetic field, such as a generating plant, a transformer station, and the like of a power system. The accurate measurement of a space magnetic field not only provides reliable data for the running and design of electrical equipment but also provides a basis for evaluating the electromagnetic environment.

Description

Measurement method of transient high-frequency magnetic field in power system

technical field

The invention belongs to the technical field of time-varying magnetic field measurement in power systems, and in particular relates to a method for measuring transient high-frequency magnetic fields in power systems.

Background technique

Substations and other places where there are high-voltage and high-current equipment, the electromagnetic environment is very complicated. Whether it is from the perspective of understanding and optimizing the performance of electrical equipment, or from the perspective of analyzing the physiological impact of the electromagnetic environment on people, it is necessary to accurately measure the relevant electromagnetic environment. The electromagnetic environment includes two aspects of electric field and magnetic field, which need to be measured according to different principles.

Magnetic field measurement refers to the measurement of magnetic flux, magnetic induction (magnetic flux density), magnetic field strength, etc. in space or magnetic materials. The magnetic induction intensity in space is linearly related to the magnetic field intensity, so the main measurement quantity of the space magnetic field measurement is the magnetic induction intensity.

The measurement of a constant magnetic field is easier and there are many methods. Commonly used measuring instruments are: torque magnetometer, rotating coil magnetometer, fluxgate magnetometer, Hall effect magnetometer, nuclear magnetic resonance magnetometer, magnetometer, or with impact galvanometer for measurement, etc. .

The measurement of time-varying magnetic field is usually based on Faraday's law of electromagnetic induction, which converts the problem of magnetic field measurement into the measurement of electric quantity. This method requires a measuring coil, which is placed in the magnetic field to be measured, and the magnetic field changes with time to generate an induced electromotive force e=-dψ/dt in the coil, where ψ is the flux linkage of the measuring coil. If the area of the coil is small enough, it can be considered that the distribution of the magnetic field in the coil is uniform, then e=-NSdB/dt, where N is the number of turns of the measuring coil, S is the area of the measuring coil, and B is perpendicular to the measuring coil The magnetic induction intensity component of the plane, the direction of B and the direction of e satisfy the right-handed spiral relationship.

At present, there are mainly two measurement methods based on the above principles. One is to directly measure the induced electromotive force, because the induced electromotive force is proportional to the rate of change of the flux linkage, so what is measured is only the derivative of the magnetic induction intensity with respect to time, not the magnetic induction intensity itself. Adding an integral circuit brings additional errors; the second is to connect the sampling resistor in series in the measuring coil to measure the voltage on the sampling resistor. At this time, because the measuring coil is closed, the equation e+Ri+Ldi/dt=0 is satisfied, where , i is the current in the measuring coil, R is the resistance value of the sampling resistor, and L is the equivalent inductance of the measuring coil. It can be seen from the above formula that the voltage on the sampling resistor and the magnetic induction intensity are neither nonlinear nor derivative. The specific relationship between them is related to the parameters R, L and the rate of change of the magnetic field. It can be seen that the current methods of measuring the magnetic field based on the principle of electromagnetic induction cannot accurately reflect the magnetic induction intensity of the space.

The sinusoidal steady-state magnetic field can be measured using the Hall principle, but it is more difficult to measure the transient magnetic field, and the error is large.

Contents of the invention

Aiming at the deficiencies of the above-mentioned time-varying magnetic field measurement method, the present invention provides a method for measuring the transient high-frequency magnetic field of a power system, which is characterized in that:

Close the measuring coil directly, so that the current in the measuring coil is the inductive current, the induced electromotive force in the measuring coil is balanced with the voltage of the equivalent inductance of the measuring coil, its expression is e+Ldi/dt=0, and e=-NSdB Substituting /dt, it can be seen that the current in the measuring coil has a linear relationship with the magnetic induction intensity, so the current is used as the measured magnetic induction intensity that can accurately reflect the space.

In order to avoid connecting the sampling resistor in series in the measuring coil, the present invention adopts a magnetic coupling method, and magnetically couples the measuring coil and the coil of the current probe through a magnetic ring, the measuring coil 1 is closed and passes through the magnetic ring, and the coil of the current probe also passes through the magnetic ring. over the ring. According to the principle of magnetic coupling, the current in the coil of the current probe is proportional to the current in the measuring coil. The optical-to-electrical converter is connected to the current probe to convert the electrical quantity into an optical signal, which is transmitted to the processing and storage device through the optical fiber.

The invention converts the measurement of the magnetic induction intensity into the measurement of the current, can accurately measure the sinusoidal steady-state magnetic field, and can especially measure the transient high-frequency magnetic field. The invention can be generally applied to the measurement of transient high-frequency magnetic fields in electromagnetic environments, especially in power plants, substations and other environments with strong magnetic fields in power systems.

Description of drawings

The present invention is described in detail below in conjunction with accompanying drawing:

Fig. 1 is a block diagram of the present invention;

Fig. 2 is the schematic diagram that the measuring coil of the present invention and the coil of current probe carry out magnetic coupling through magnetic ring;

Fig. 3 is a schematic diagram of the coupling between the measuring coil and the high-precision current transformer through the magnetic ring of the present invention.

Reference signs:

1-Measuring coil, 2-Magnetic ring, 3-Current probe coil, 4-Current probe,

5-photoelectric converter, 6-processing and storage equipment, 7-high precision current transformer.

Detailed ways

Embodiment one

As shown in FIG. 1 , the measuring coil 1 is placed in the magnetic field to be measured. Since the magnetic field changes with time, an induced electromotive force is generated in the measuring coil 1 . If the area of the measuring coil 1 is small enough relative to the distribution of the magnetic field to be measured, it can be considered that the magnetic field in the measuring coil 1 is uniformly distributed, and the interlinked magnetic flux of the measuring coil 1 is proportional to the magnetic induction intensity.

The measuring coil 1 is closed and passes through the magnetic ring 2, and the induced electromotive force in the measuring coil 1 is balanced with the voltage of the equivalent inductance of the measuring coil 1, so it can be seen that the magnetic induction intensity has a linear relationship with the current in the measuring coil 1. The coil 3 of the current probe 4 also passes through the magnetic ring 2, as shown in FIG. 2 . According to the principle of magnetic coupling, it can be seen that the current of the coil 3 has a linear relationship with the current of the measuring coil 1, and thus the current of the coil 3 has a linear relationship with the magnetic induction. The photoelectric converter 5 is connected with the current probe 4 and converts the electricity into an optical signal, which is transmitted to a processing and storage device 6 through an optical fiber. The processing and storage device 6 first converts optical signals into digital quantities, saves and calculates the measured data, and displays the measurement results through the man-machine interface. Because the magnetic induction is a vector, when measuring the magnetic field of the electromagnetic environment, each point should measure three components according to the Cartesian coordinate system, so as to obtain the magnitude and direction of the magnetic induction at that point. The magnetic field strength at that point is obtained by dividing the magnetic induction by the magnetic permeability of the vacuum.

Embodiment two

As shown in Figure 3, the measuring coil 1 is placed in the magnetic field to be measured, the magnetic ring 2 passes through the measuring coil 1, and the high-precision current transformer 7 realizes the coil 3, the current probe 4, the photoelectric converter 5, the processing and The function of the storage device 6, the magnetic ring 2 is also an integral part of the high-precision current transformer 7.

The specific implementation method can be summarized as follows: the measuring coil 1 passes through the magnetic ring 2, and the measuring coil 1 is directly closed. When the measuring coil 1 is placed in the magnetic field to be measured, an induced current will be generated in the measuring coil 1 , and the induced current has a linear relationship with the component of the magnetic induction intensity B perpendicular to the plane surrounded by the measuring coil 1 . The induced current in the measuring coil 1 is measured by a high-precision current transformer 7, so that the component of the magnetic induction intensity B perpendicular to the plane surrounded by the measuring coil 1 can be measured. When measuring the magnetic field of the electromagnetic environment, each point should measure three components according to the Cartesian coordinate system, so as to synthesize the magnitude and direction of the magnetic induction intensity of the point. The magnetic field strength at that point is obtained by dividing the magnetic induction by the magnetic permeability of the vacuum.

Claims (3)

1. the measuring method of an electric system transient state high frequency magnetic field, this method is based on electromagnetic induction principle, it is characterized in that, measure coil (1) closure and pass magnet ring (2), the coil (3) of current probe (4) also passes magnet ring (2), photoelectric commutator (5) links to each other with current probe (4), and electric weight is converted to light signal, and links to each other with memory device (6) with processing by optical fiber.

2. the method for claim 1 is characterized in that, the area of described measurement coil (1) DISTRIBUTION OF MAGNETIC FIELD to be measured relatively is enough little.

3. the method for claim 1, it is characterized in that, the function of the coil (3) of described magnet ring (2), current probe (4), current probe (4), photoelectric commutator (5), processing and memory device (6) can be integrated by high precision current transformer (7) and realize.

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