JPH0590375U - Harmonic checker - Google Patents

Abstract

(57) [Summary] [Purpose] The purpose of this invention is to provide a harmonic checker that allows a user to easily investigate and monitor the occurrence status of harmonics at a low cost even before a harmonic propagation failure accident occurs. There is a point to do. According to the configuration of the present invention, a harmonic component detecting means for detecting a harmonic component of a power system for each desired order, and a reference level setting means for setting a reference level according to the order of a detected harmonic signal. A comparison determination means for comparing the harmonic signal detected by the harmonic component detection means with a reference level signal set by the reference level setting means for each order, and a state held by the comparison determination means In addition, there is an alarm display means for displaying an alarm signal determined for each order, and a reset means for resetting the alarm signal to an initial state, in a harmonic checker, wherein the harmonic component detecting means is provided. It may be a harmonic component detection method that detects every fixed period.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a harmonic checker for easily checking the harmonic generation state of a power system.

[Prior art]

The power supplied to the device is preferably supplied in a sinusoidal waveform, but in reality, waveform distortion is considerably generated. As the degree of waveform distortion increases, harmonic interference often occurs in the phase-adjusting equipment and other equipment, and accidents often occur, so the problem of power supply system quality is being highlighted. Considering a general power system as shown in FIG. 3 as an example, the harmonic interference is caused by connecting the harmonic signal V _n to the bus 2 and propagating this signal. Since the load circuit of the harmonic signal V _n becomes a parallel load circuit of the internal impedance Z sn of the power supply side system S and the load impedance Zcn of the local load system C, the harmonic current I _n is shunted to both systems and propagated. Will be. When the n-th harmonic current I _n is generated, the mode of its propagation is that the harmonic current I _n is divided into the internal impedance Zsn of the power source side system S and the load impedance Zcn of the local load system C, If harmonic current I _n the load impedance Zcn also become inductive become non-expanded. Internal impedance Zsn and flows to the load impedance Zcn premises load system C min, harmonic current I _n premise load system load impedance Zcn premises load system C is a series resonance of the harmonic current I _n is the power supply side system S When flowing only to C. Harmonic current I _n is poured into a separatory load impedance Zcn internal impedance Zcn and premises load system C of the power supply side system S, the load impedance Zcn premises load system C is turned capacitive power supply side line S side harmonic current I _n becomes almost constant, if only current configuration in the load system C side is enlarged. Harmonic current I _n is poured into a separatory load impedance Zcn internal impedance Zcn and premises load system C of the power supply side system S, the load impedance Zcn premises load system C becomes capacitive, the capacity of the power source side system S In the case where parallel resonance occurs due to the inductance of the internal impedance Zs n, and the harmonic currents of the power supply side system S and the premises load system C expand. Harmonic current I _n is poured into a separatory load impedance Zcn internal impedance Zsn and premises load system C of the power supply side system S, the load impedance Zcn premises load system C becomes capacitive, the power supply side system S side harmonics If current I _n is substantially constant, only the current premises load system C side is enlarged. Can be roughly divided into five modes. It is considered that the causes of the harmonic interference accidents in these five types of harmonic propagation are the following cases, and when the harmonic generation location and the accident location occur in the same customer, It may occur in another place, or may propagate to other customers via the high voltage busbar. Although not shown in the figure, when harmonics are generated in the upper system and propagated to the lower system and cause an accident, higher harmonics are generated in the upper system and lower system, respectively, and these harmonics are superposed. There are many cases where an accident may occur. The mechanism of such a harmonic propagation disturbance accident is considered, but it is understood as a result of investigating the cause of the accident that it is the accident caused by the harmonic propagation disturbance. For investigating the cause of the accident, it takes a long time to carry various measuring instruments such as a research frequency analyzer to the accident site, set various conditions, measure and record them, and analyze them. It costs. Therefore, it takes time and labor to grasp that the cause of the accident is harmonic propagation disturbance, and it also takes a long time and labor to identify the place (equipment) where the harmonic is generated. become. It would be possible to prevent accidents from occurring by allowing consumers to install measuring instruments for research purposes and monitor the occurrence of harmonics. Not only is the equipment cost high for customers, but handling of measuring instruments is complicated, so it is not considered appropriate at present. In consideration of the situation of the fault accident due to the harmonic propagation, the present invention is a harmonic checker that allows a consumer to easily investigate and monitor the harmonic generation situation at a low cost even before the occurrence of the harmonic propagation fault. Is intended to provide.

[0002]

[Means for Solving the Problems]

 As a first idea, the harmonic checker of this invention sets the harmonic component detection means for detecting the harmonic components of the power system for each desired order and the reference level according to the order of the detected harmonic signal. Reference level setting means for comparing the harmonic signals detected by the harmonic component detecting means with the reference level signal set by the reference level setting means for each order, and the comparing and determining means. The alarm display means for holding the state determined by the above and displaying the alarm signal determined for each order, and the reset means for resetting the alarm signal to the initial state are provided. It is preferable that the detected harmonic components are at least the third, fourth, fifth and seventh harmonics. A second invention is characterized in that the harmonic component detecting means of the first invention is a harmonic component detecting means for detecting every fixed period.

The first difference between the first device and the second device is that the first device continuously detects the harmonic components of the electric power system and compares them with the reference level to make a judgment. The second idea is to detect the harmonic components of the power system at regular intervals and compare them with the reference level.

The order of the harmonic components to be checked is preferably selected from at least four types of harmonic components of the third, fourth, fifth and seventh harmonic components. Third and reason for choosing fourth-order harmonic component, equipment for currently used has been that adjustment phase, for example, a series reactor for power capacitor as an example, JIS C 48 01- ₁₉₉₀ "high pressure and special Looking at the commentary column of "Series reactor for high voltage phase-advancing capacitor", it is enough to consider "35% of the 5th harmonic as a general case where a large majority is used" in determining the maximum allowable current as an overload condition. Although measures have been taken against the 5th harmonic due to the fact that it is supposed to be, etc., etc., the 4th order, which is lower than the 5th harmonic, is taken into consideration in view of the current state of installation of rectifiers for large currents. And the third harmonic is often generated, and when a 6% series reactor is used, the harmonic propagation of ,, causes damage to the phase-advancing capacitor or series reactor due to expanded overcurrent. Obstacle Since the number of accidents has been increasing in recent years, it is necessary to constantly monitor the third and fourth harmonic components to prevent accidents. If the 5th harmonic becomes abnormally large and a capacitor device with a 6% series reactor is used, for example, if the voltage waveform distortion is 3.5% or more, the fifth harmonic current of 35% or more of the fundamental wave flows in the reactor. As a result, a series reactor burnout accident will occur. Therefore, the investigation and monitoring of the fifth harmonic generation status is intended to be used as a danger prediction signal for the prevention of harmonic interference accidents in the direct reactor of electric power consumers. is there. The reason why we chose the 7th harmonic is that the inductance of the low voltage capacitor and the transformer is the 7th harmonic filter for the high voltage bus 2 and the 7th harmonic is abnormally large on the low voltage bus. This is because the equipment will be overloaded and will eventually be damaged, so the 7th harmonic generation status will be monitored to prevent such accidents.

As shown in FIG. 1, the first idea is to extract a measured current from a high voltage bus 2 by a current transformer CT, and use this to obtain a bandpass filter BPF ₃ for the third harmonic and a current for the fourth harmonic. The components are distributed to the bandpass filter BPF ₄ , the bandpass filter BPF ₃ for the fifth harmonic, and the bandpass filter BPF ₇ for the seventh harmonic to detect each harmonic component of each order. The detected harmonic signals are converted into DC signals by the rectifier circuits DET ₃ , DET ₄ , DET ₅ and DET _7, respectively. This DC signal, third-order, fourth-order, 5th, 7th reference (direct current) signal setting circuit _{REF 3,} REF _4, REF 5, RE _{F 7} of the reference signal and the comparison circuit COMP _3, The levels are compared using COMP ₄ , COMP ₅ , and COMP ₇ , respectively. The signals compared by the comparison circuit are input to the set terminals of the flip-flop circuits FF ₃ , FF ₄ , FF ₅ , and FF ₇ , respectively, to record and hold them, and hold period light display devices LED ₃ , LED ₄ , LED ₅ , LED ₇ The warning light is displayed by. Resetting the alarm signal can be cleared memory hold signal by inputting a reset signal from the reset terminal of the flip-flop circuit _{FF 3, FF 4, FF 5} , FF 7. As for the total harmonic distortion, an alarm can be optically displayed by the same means except that a bandpass filter that passes a band higher than the second harmonic is used.

The second invention can be implemented by digital signal processing using a microprocessor unit (MPU) or the like, and FIG. 2 shows a block diagram for explaining the embodiment. The measurement voltage is taken out from the high-voltage bus 2 by the transformer PT for an instrument, and this is sampled for a fixed time (sampling time t ₁ ) by the A / D converter, and the sampling time t ₁ is followed by a fixed time (analysis processing time t ₂ ) The harmonic component is detected by the real time method of the cycle [1 / (t ₁ + t ₂ )] in which the waveform information sampled in ₂ ) is calculated and an alarm signal is output. The calculation process calculates the 3rd, 4th, 5th, and 7th harmonic components from the stored waveform information using the Fast Fourier Transform (FFT) program, and specifies these values from the external switch SW. When the level exceeds the reference signal level, the alarm signal is output from that point. The order of the higher harmonic wave which issues the alarm signal is optically displayed by the number display device DS, and the alarm signal is displayed by the display device LED ₀ instead of the light signal. The optical signal can be reset by clearing the register that calculates the alarm signal.

[0007]

[Effect of the device]

 The harmonic checker of the present invention adapts to the unique harmonics generated in the power system and detects the harmonic components of the necessary and sufficient order, which reduces the cost and sets the reference level for each order of the harmonic components. By doing so, the degree of harmonic interference occurring in the power system can be appropriately known.

[Brief description of drawings]

FIG. 1 is a block diagram illustrating an embodiment of a first device.

FIG. 2 is a block diagram illustrating an embodiment of a second device.

FIG. 3 is an explanatory diagram of a general power supply system.

[Explanation of symbols]

1 ... Infinity bus 2 ... High-voltage bus S ... Power supply side system N ... Harmonic generation load system C ... Local load system V _n ... Nth harmonic voltage I _n ... Nth harmonic current CT ... Instrument current change PT ・ ・ ・ Instrument transformer BPF ・ ・ ・ Band pass filter COMP ・ ・ ・ Voltage comparator REF ・ ・ ・ Reference signal LED ・ ・ ・ Optical display device FF ・ ・ ・ Flip-flop circuit MPU ・ ・ ・ Microprocessor unit DS ・ ・ ・ Number display device LED ₀・ ・ ・ Optical display device SW ... External switch

Claims (3)

[Scope of utility model registration request] 1. A harmonic component detecting means for detecting a harmonic component of a power system for each desired order, a reference level setting means for setting a reference level according to the order of a detected harmonic signal, and the harmonic. Comparison discrimination means for comparing the harmonic signal detected by the component detection means with the reference level signal set by the reference level setting means for each order, and holding the state discriminated by the comparison discrimination means and for each order A harmonic checker, comprising: alarm display means for displaying an alarm signal determined for each case; and reset means for resetting the alarm signal to an initial state. 2. The harmonic checker according to claim 1, wherein the harmonic component detecting means is a harmonic component detecting means for detecting every fixed period. 3. The harmonic component to be detected is at least the third order,
The harmonic checker according to claim 1 or 2, wherein the harmonic checker has fourth, fifth, and seventh harmonic components.