JPH03277979A - Zero-phase voltage detector - Google Patents

Abstract

PURPOSE:To ignore an error due to influence of other phase and an irregularity in sensitivity of a phase voltage sensor itself and to prevent an erroneous judgement of an accident, etc., by directly observing a zero-phase voltage without separately measuring respective phase voltages. CONSTITUTION:Charge generated on the outer surface of a cylindrical electrode 3 formed at an arbitrary position around a 3-phase parallel high voltage line 1 is proportional to total change in the electrode 3, and proportional to vector addition of the respective phase voltages, i.e., a zero-phase voltage. Accordingly, an electric field outside the electrode 3 is proportional to the zero-phase voltage, and the zero-phase voltage of the line 1 can be detected by an electric field sensor 4A. In this case, the polarizing surface of an electro-optical polarizer is extended in the direction of an electric field E in response to the intensity of the field E in the sensor 4A. If the polarizing surfaces of a polarizing plate and a photodetector are matched thereto, an incident light amount of a signal processor 5 is increased in response to the intensity of the field. The intensity of the field is increased in response to the zero-phase voltage, unnecessary positive and reverse phase components are not included in the field to be measured by the sensor 4A, and an error components of mutual actions of three- phase power distribution lines are cancelled to be ignored.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a zero-phase voltage detection device, such as a power distribution status monitoring sensor, that can directly and accurately detect a zero-phase voltage indicating the power distribution status of a three-phase power distribution line using a simple method.

2. Description of the Related Art As shown in FIG. 3, a conventional zero-sequence voltage detection device includes a voltage divider (consisting of an inner electrode 2A, an outer electrode 2B, and an interelectrode dielectric 6) for each phase of a three-phase high-voltage distribution line 1. The output voltage (partial pressure) of each voltage divider is constantly monitored by the voltage sensor 4, and the voltage values of each phase are added vectorially in the data processing unit 5, thereby providing indirect but non-contact control. This is used to detect the zero-sequence voltage of three-phase high-voltage distribution lines.

Problems to be Solved by the Invention In the conventional method described above, each phase is affected by other phases, and the voltage sensor for each phase has sensitivity variations, making it impossible to accurately measure each phase voltage. The zero-sequence voltage determined by A/addition contains an error, which may cause erroneous judgments such as accidents.

It is an object of the present invention to solve the above-mentioned problems of the conventional zero-sequence voltage detection device, and to detect the zero-sequence voltage with high precision using a simple method that is less costly than the conventional one.

Means for Solving the Problems In order to achieve the above objects, the zero-phase chamber (0-phase chamber) pressure detection device of the present invention includes three-phase high-voltage distribution lines all together and a cylindrical chamber 11 (for example, a copper plate) formed around the three-phase high-voltage distribution line. Either by attaching an electric field sensor to the outside of the cylindrical electrode and observing the charge proportional to the zero-sequence voltage generated outside the electrode, or by installing a cylindrical parallel electrode to the outside of the cylindrical electrode and measuring the voltage between the electrodes. It has a configuration in which a voltage sensor is provided to observe the voltage.

Effect: With the above-described configuration, the present invention can directly observe the zero-sequence voltage without measuring each phase voltage, so it is possible to ignore errors caused by the influence of other phases and the sensitivity variations of each phase voltage sensor itself. This eliminates misjudgment of accidents.

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

Embodiment A first embodiment of the present invention will be described with reference to FIG. As shown in the figure, three-phase parallel high voltage electric wire 1 which is the object to be measured
are surrounded by a cylindrical electrode 3 and installed parallel to the electrode surface, that is, perpendicular to the electric field E, and an electric field sensor 4A and a signal processing unit 6. It is composed of an input optical fiber 7 and an output optical fiber 8. Here, the cylindrical chamber 4i3 may be located at any position around the three-phase parallel high-voltage electric wire 1 and without contact.

Here, the electric field sensor 4A, the signal processing section 6. To explain the configuration of the input optical fiber 7 and the output optical fiber 8 in more detail, the electric field sensor 4A includes an electro-optic polarizer that uses electro-optic effects (Pockels effect and Kerr effect), such as lithium niobate and lithium niobate. It is configured so that light passes through the material in a direction perpendicular to the direction Σ of the electric field,
The light emitted from the signal processing unit 6 passes through the input optical fiber 7 within the electric field sensor 4A, first passing through a polarizing plate (not shown), an electro-optic polarizer (not shown), and an analyzer (not shown). The signal is applied to the signal processing section 5 via an output optical fiber 8.

Next, the operation of the first embodiment of the present invention configured as described above will be explained. The electric 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 According to Gauss's theorem, is proportional to the total charge in the cylindrical electrode, 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-sequence voltage, and the zero-sequence voltage of the three-phase parallel high-voltage electric wire 1 can be detected by the electric field sensor 4A. At this time, within the electric field sensor 4A, the polarization plane of the electro-optic polarizer expands in the direction of the electric field E depending on the strength of the electric field E, so if the polarization planes of the polarizer and analyzer are aligned in this direction, the electric field The amount of light incident on the signal processing unit 6 increases according to the strength of the electric field, and the strength of the electric field increases according to the zero-sequence voltage, so an increase in the amount of incident light can be detected as an increase in the zero-sequence voltage. can. The electric field observed by the electric field sensor 4A does not include unnecessary positive-phase components and negative-phase components, and the error component due to the interaction of the three-phase distribution line is also canceled out and can be ignored, resulting in reliability with little error. Highly accurate data can be obtained.

A second embodiment of the invention will be described with reference to FIG. In this embodiment, as shown in the figure, a three-phase parallel high-voltage electric wire 1, which is an object to be measured, is surrounded in this order by an inner cylindrical electrode 3A, a dielectric 6, and an outer cylindrical electrode 3B. It is composed of a voltage sensor 4B that measures the interelectrode voltage of the cylindrical electrode 3B and a signal processing section 6. The dielectric 6 may be air. Here, the inner cylindrical electrode 3A and the outer cylindrical electrode 3B may be placed at arbitrary positions as long as they are around the three-phase parallel high-voltage electric wire 1 and are not in contact with each other. 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. An electric field is added accordingly,
Therefore, the amount of incident light applied to the signal processing section 6 also increases.

The operation of the second embodiment of the present invention configured as described above will be explained below. According to Gauss's theorem, the charge is proportional to the total charge inside the inner cylindrical electrode, and the total charge is calculated by adding the vector voltages of each phase,
In other words, it is proportional to the zero-sequence voltage. Therefore, the inner cylindrical electrode 3
The voltage generated between A and the outer cylindrical chamber FMa B is also proportional to the zero-sequence voltage, and the voltage sensor 4B can detect the zero-sequence voltage of the three-phase parallel high-voltage electric wire 1. 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 canceled out and can be ignored, resulting in reliability with little error. Highly accurate data can be obtained.

Although the above description has been made regarding the most common three-phase AC power distribution line, it is of course applicable to two-phase, four-phase or more-phase AC as long as the system is a symmetrical polyphase system.

Further, the parallelism between the electric wires does not need to be very strict in principle.

Also electric field sensor 4A! Although the pressure sensor 4B has good insulation and uses light that is not guided, other detection methods may be used as long as the measurement is not affected.

Effects of the Invention As is clear from the above explanation, the present invention allows zero-sequence voltage to be directly observed without measuring positive-sequence components and negative-sequence components that are unnecessary for fault detection. Errors caused by variations in sensitivity of the voltage sensor itself can be ignored and highly reliable data can be obtained, which has the effect of eliminating erroneous judgments such as accidents.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a zero-phase voltage detection device according to a first embodiment of the present invention, FIG. 2 is a perspective view of a zero-phase voltage detection device according to a second embodiment of the present invention, and FIG. FIG. 2 is a perspective view of a zero-phase 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 old... Outer cylindrical electrode, 4A...
...Electric field sensor, 4B, old...Voltage sensor, 6...
... Signal processing section, layer electric body for 6.

Claims (2)

[Claims] (1) A zero-phase voltage detection device that forms a cylindrical electrode at any position around a plurality of phase conductors and detects the electric field generated on the outer surface of this cylindrical electrode. (2) A cylindrical electrode is formed at any position around the plurality of phase conductors, and an outer cylindrical electrode is formed on the outside of this cylindrical electrode with a dielectric interposed between the cylindrical electrode and the outer side. A zero-phase voltage detection device that detects the voltage generated between the cylindrical electrode and the cylindrical electrode.