JPS61241670A - Direct reading device for distortion value of distribution voltage - Google Patents

Abstract

PURPOSE:To enable digital display by separating higher order harmonic component of input voltage from a transmitting and distributing end and calculating distortion rate of input voltage from the effective value. CONSTITUTION:Input voltage from a transmitting and distributing end is voltage divided by an input voltage divider 1. Then, higher order harmonic voltage component of higher order mode is cut off by passing through an LPF for preventing errors caused by phase deviation in higher harmonic band generated when calculating distortion rate. Further, fundamental wave component of input voltage is separated by an LPF 3, and phase deviation of fundamental wave voltage component and higher harmonic voltage component is corrected by a phase shifting circuit 4. Then, distortion rate based on effective value of higher order harmonic voltage component is calculated by a differential amplifier 5 and an RMS/DC converter 7, and the distortion rate is digital displayed in a digital display section 8.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a device for measuring higher-order harmonic components contained in the voltage of a power transmission and distribution system.

[Conventional technology]

Traditionally, measurement devices used to manage high-order harmonics contained in the voltage of power transmission and distribution systems have become more accurate and highly functional due to laboratory requirements, and have become extremely large, making it difficult to use actual single devices. At present, there are not many concrete examples that can be used as such.

[Problem that the invention seeks to solve]

There is a problem in that the measuring devices used for the future high-order harmonic management as described above are not suitable for use at power distribution terminal sites in electric utilities.

This invention was made to solve such problems, and the object is to obtain a portable high-order harmonic direct reading device that is smaller, lighter, and capable of direct reading necessary for high-order harmonic management. .

[Means for solving problems]

A device for directly reading a distribution voltage distortion value according to the present invention includes a plurality of low-pass filters that separate an input voltage into a fundamental wave component and a high-order harmonic component, a differential amplifier that calculates a voltage difference between the input voltage and its fundamental wave component, RMS to find the effective value of the voltage difference
It is equipped with a /DO converter and a distortion rate digital display unit, and digitally displays the distortion rate required for harmonic management.

[Effect]

In this invention, the input voltage from the power transmission and distribution end is passed through a low-pass filter to prevent errors caused by phase shifts in the harmonic region of the higher-order modes that occur when calculating the distortion factor. After cutting off the harmonic voltage component, a second low-pass filter separates the fundamental wave component of the input voltage, and a phase shift circuit corrects the phase shift between the fundamental voltage component and the harmonic voltage component. The differential amplifier and the RMS/DC converter digitally display the distortion factor based on the calculated high-order harmonic voltage component Ω effective value.

〔Example〕

FIG. 1 is a block diagram showing one embodiment of the present invention.

The input voltage from the power transmission/distribution end is divided by an input voltage divider 1 and input to a low-pass filter (LPF) 2 and a differential amplifier 5. A low-pass filter (LPF) 2 cuts off higher-order mode harmonic components of the signal voltage (hereinafter referred to as partial voltage) from the input voltage divider 1. In this embodiment, the cutoff frequency fo of the low pass filter (LPF) 2 is set to 100OH7.
The reason for this is to prevent errors caused by phase shifts in the harmonic region of higher-order modes in the differential amplifier 5.
The effective proportion of harmonic components above Hz is very small,
This is because even if harmonic components of 1000 Hz or more are ignored, there is no problem in calculating the distortion factor of the input voltage. The signal voltage at the output end of the low-pass filter (LPF) 2 is determined by the low-pass filter (LPF) whose cutoff frequency f is set to 70Hz.
PF) 3 cuts off the high-order harmonic components, and only the fundamental wave component is input to the phase shift circuit 4, where it is passed through a low-frequency filter (LPF).
) is shifted in phase so that it is in phase with the signal voltage at the output terminal of 2. The difference between the signal voltage at the output end of the phase shift circuit 4 and the signal voltage at the output end of the Lohas filter (LPF) 2 is calculated by a differential amplifier 5.
When determined by the common-mode signal removal effect of Letting the effective value of the component be vo, the distortion factor of the input voltage is defined by the following equation.

Distortion rate = (Vh/Vo) x 100 ('16)
=vhxα[chi]... (1) Therefore, the signal voltage at the output terminal of the differential amplifier 5 is amplified by the real value α defined by (1) K in the amplifier 6, and then the RMS/DC is When converted by the converter 7, a distortion factor of the input voltage as shown in (1) is obtained, which can be digitally displayed on the digital display section 8.
゛ - Note that the effective value Vh of the fundamental wave component of the partial voltage in (1) is qualitatively constant at the input voltage distortion measurement end due to the current situation where the input voltage exceeds the maintenance range of the transmission and distribution voltage K99.5n. Considering this, the distortion factor of the input voltage is calculated using the real value α;100/Vo defined in (1) as a constant.

〔Effect of the invention〕

As described above, the present invention includes a plurality of low-pass filters, a phase shift circuit for separating high-order harmonic components of an input voltage, a differential amplifier, and ``calculating the effective value of high-order harmonic components of an input voltage.'' Since it is equipped with an R'MS/DC converter, a digital display, etc., it is possible to separate the high-order harmonic components of the input voltage from the power transmission and distribution terminals, and calculate the distortion factor of the input voltage from the effective value. This has the effect of making it easier to manage high-order harmonics at power distribution terminal sites in the electricity industry.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention. In the figure, 1 is the input voltage divider, 2 is the cutoff frequency 1
00 is a low-pass filter with a characteristic of QHz, 3 is a low-pass filter with a characteristic of a cut-off frequency of 70Hz,
7 is an RMS/DC converter.

Claims (1)

[Claims] a plurality of low-pass filters, a phase shift circuit and a differential amplifier that separate the input distorted voltage into high-order harmonic voltage components, a converter that determines the effective value of the high-order harmonic voltage components, and the distorted voltage. A device for directly reading a distribution voltage distortion value, comprising: a display section that digitally displays a waveform distortion factor.