JP2722749B2 - Zero-phase voltage detector - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zero-phase voltage detecting device, such as a distribution state monitoring sensor, capable of directly and accurately detecting a zero-phase voltage indicating a distribution state of a three-phase distribution line by a simple method.

2. Description of the Related Art As shown in FIG. 3, a conventional zero-phase voltage detecting device includes a voltage divider (inner electrode 2A, outer electrode 2) for each phase of a three-phase high voltage distribution line 1.
B and the inter-electrode dielectric 6) are installed, and the output voltage (divided voltage) of each voltage divider is constantly monitored by the voltage sensor 4, and the voltage value of each phase is vectorized in the data processing unit 5. The addition detects the zero-phase voltage of the three-phase high-voltage distribution line in an indirect but non-contact manner.

Problems to be Solved by the Invention In the above-mentioned conventional method, each phase is affected by another phase,
Since the voltage sensors of the respective phases have sensitivity variations and cannot accurately measure the respective phase voltages, the zero-phase voltage obtained by the vector addition of the respective phase voltages may include an error and cause an erroneous determination such as an accident.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems of the conventional zero-phase voltage detecting device and to accurately detect the zero-phase voltage by a simple method that does not cost more than the conventional one.

Means for Solving the Problems In order to achieve the above object, the zero-phase voltage detecting device of the present invention provides a three-phase high-voltage distribution line by providing a cylindrical electrode (for example, a copper plate) around it in a non-contact manner. Either mounting an electric field sensor on the outside and observing the charge proportional to the zero-phase voltage generated outside the electrode, or providing a cylindrical parallel electrode outside the cylindrical electrode and observing the voltage between the electrodes A voltage sensor is provided.

In the configuration as described above, the charge generated on the outer surface of the cylindrical electrode provided in a non-contact manner around the three-phase high-voltage distribution line is based on Gauss's theorem and the following three trivial conditions (A) The outer surface of the cylindrical electrode is equipotential. (B) The shape of the cylindrical electrode is constant. (C) The relative positional relationship between the cylindrical electrode and the reference potential is constant. The outer surface is distributed so as to have the same potential, and the distribution of the surface charge varies in intensity depending on the state of the internal charge, but the distribution itself is a relative positional relationship between the shape of the cylindrical electrode and the cylindrical electrode and a reference potential. Is invariant because it depends on

Therefore, the total amount of charge inside the cylindrical electrode is dispersed on the outer surface of the cylindrical electrode by a distribution coefficient depending on the shape of the cylindrical electrode and the relative positional relationship between the electrode and the reference potential. (D) The relative positional relationship between the cylindrical electrode and the electric field sensor is constant. Therefore, the electric field at the certain electric field sensor position is determined by the total charge amount inside the cylindrical electrode and the electric field sensor position. Is determined by the product of the distribution coefficients inherent to the electric field sensor, and the amount of charge change at a local portion on the outer surface of the cylindrical electrode detected by the electric field sensor is proportional to the zero-phase voltage.

As described above, according to the present invention, the zero-phase voltage can be directly observed without measuring each phase voltage, so that errors due to the influence of other phases and variations in sensitivity of each phase voltage sensor itself can be ignored, and an accident can be ignored. No misjudgment is made.

Furthermore, when the absolute number of voltage sensors or electric field sensors is three-phase, it is only one-third that of the conventional example, and the installation position of the parallel cylindrical electrodes around the three-phase high-voltage distribution line can be arbitrarily set. This is advantageous in terms of workability.

Embodiment 1 A first embodiment of the present invention will be described with reference to FIG. As shown in the figure, a three-phase parallel high-voltage electric wire 1 which is an object to be measured
Are collectively surrounded by a cylindrical electrode 3 and are composed of an electric field sensor 4A installed parallel to the electrode surface, that is, perpendicular to the electric field E, a signal processing unit 5, an input optical fiber 7, and an output optical fiber 8. Have been. Here, the cylindrical electrode 3 may be located at any position around the three-phase parallel high-voltage electric wire 1 and in a non-contact state.

Here, the configuration of the electric field sensor 4A, the signal processing unit 5, the input optical fiber 7, and the output optical fiber 8 will be described in more detail. The electric field sensor 4A has an electro-optical effect using an electro-optical effect (Pockels effect or Kerr effect). A polarizer, for example, a material such as lithium niobate or lithium niobate is configured to transmit light in a direction perpendicular to the direction E of the electric field, and the light emitted from the signal processing unit 5 is transmitted through the input optical fiber 7 to the electric field sensor 4A. First, the light passes through a polarizing plate (not shown), an electro-optical polarizer (not shown), and an analyzer (not shown), and is applied to the signal processing unit 5 via an output optical fiber 8. .

The operation of the first embodiment of the present invention configured as described above will now be described. The charge generated on the outer surface of the cylindrical electrode 3 formed at an arbitrary position around the three-phase parallel high-voltage electric wire 1 is described. Is proportional to the total charge in the cylindrical electrode according to Gauss's theorem, and the total charge is proportional to the vector addition of each phase voltage, that is, the zero-phase voltage. Therefore, the electric field generated outside the cylindrical electrode 3 is also proportional to the zero-phase voltage, and the zero-phase voltage of the three-phase parallel high-voltage electric wire 1 can be detected by the electric field sensor 4A. At this time, in the electric field sensor 4A, the polarization plane of the electro-optical deflector spreads in the direction of the electric field E in accordance with the intensity of the electric field E. The intensity of the electric field incident on the signal processing unit 5 also increases according to the intensity of the electric field, and the intensity of the electric field increases according to the zero-phase voltage.
The increase in the amount of incident light can be detected as an increase in the zero-sequence voltage. The electric field observed by the electric field sensor 4A does not include unnecessary positive and negative phase components, and
The error component due to the interaction of the three-phase distribution lines is also canceled out and can be ignored, so that highly reliable data with little error can be obtained.

A second embodiment of the present invention will be described with reference to FIG. In this embodiment, as shown in the figure, the inner cylindrical electrode 3A, the derivative 6 and the outer cylindrical electrode 3B are sequentially surrounded around the three-phase parallel high-voltage electric wire 1, which is the object to be measured. It comprises a voltage sensor 4B for measuring the inter-electrode voltage of the electrode 3B and a signal processing unit 5. The dielectric 6 may be air. Here, the inner cylindrical electrode 3A and the outer cylindrical electrode 3B may be located at any positions around the three-phase parallel high-voltage electric wire 1 and in a non-contact state. Here, the voltage sensor 4B has two electrodes attached to the electro-optic polarizer of the electric field sensor 4A used in the first embodiment so as to apply an electric field in a direction perpendicular to the light. Accordingly, an electric field is applied, and accordingly, incident light applied to the signal processing unit 5 also increases.

The operation of the second embodiment of the present invention configured as described above will be described below. The operation occurs on the outer surface of the inner cylindrical electrode 3A formed at an arbitrary position around the three-phase parallel high-voltage electric wire 1. The charge is proportional to the total charge in the inner cylindrical electrode according to Gauss's theorem, and the total charge is the vector addition of each phase voltage,
That is, it is proportional to the zero-phase voltage. Therefore, the inner cylindrical electrode 3A
The voltage generated between the outer cylindrical electrode 3B and the outer cylindrical electrode 3B is also proportional to the zero-phase voltage, and the zero-phase voltage of the three-phase parallel high-voltage electric wire 1 can be detected by the voltage sensor 4B. The voltage observed by the voltage sensor 4B does not include unnecessary positive-phase components and negative-phase components, and error components due to the interaction of the three-phase distribution lines are also negligible and can be ignored. High data can be obtained.

Although the most general three-phase AC distribution line has been described above, it goes without saying that the present invention can be applied to two-phase or four-phase or more alternating current as long as it is a symmetric polyphase system.

The parallelism between the electric wires does not require much strictness in principle.

Further, the electric field sensor 4A and the voltage sensor 4B have a good insulation property, and the method using light that is not guided has been described. However, other detection methods may be used as long as the measurement is not affected.

Advantageous Effects of the Invention As is clear from the above description, the present invention can directly observe the zero-sequence voltage without measuring the positive-phase component and the negative-sequence component, which are unnecessary for fault detection. The error caused by the sensitivity variation of the voltage sensor itself can be ignored, and highly reliable data can be obtained, so that there is an effect that erroneous determination of an accident or the like is eliminated.

[Brief description of the drawings]

FIG. 1 is a perspective view of a zero-phase voltage detecting device according to a first embodiment of the present invention, FIG. 2 is a perspective view of a zero-phase voltage detecting device according to a second embodiment of the present invention, and FIG. It is a perspective view of a zero-sequence voltage detection device. 1 ... three-phase parallel high-voltage electric wire, 2A ... inner cylindrical electrode of voltage divider, 2B ... outer cylindrical electrode of voltage divider, 3 ... cylindrical electrode, 3A
... inner cylindrical electrode, 3B ... outer cylindrical electrode, 4A ... electric field sensor, 4B ... voltage sensor, 5 ... signal processing unit, 6 ...
... dielectric.

Claims (2)

(57) [Claims] 1. A zero-phase voltage detecting device for forming a cylindrical electrode at an arbitrary position around a group of multi-phase conductors and detecting an electric field generated on the outer surface of the cylindrical electrode. 2. A cylindrical electrode is formed at an arbitrary position around a group of multi-phase conductors, and an outer cylindrical electrode is formed outside of the cylindrical electrode via a dielectric material. A zero-phase voltage detection device for detecting a voltage generated between the outer cylindrical electrode and the outer cylindrical electrode.