JPH0974660A - Harmonic detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a harmonic detector to detect harmonics with high accuracy by taking the flowing direction of each order of harmonics into consideration by detecting the flowing direction. SOLUTION: A harmonic detector detects harmonics by respectively supplying the detecting outputs of a current transformer 3 and an instrument transformer 5 provided in the power receiving section of power equipment to current and voltage calculating sections and the harmonics of the current and voltage to a discriminating section after finding the harmonics at every order, and then, discriminating the flowing direction of the harmonics, whether the harmonics flow to or from the power equipment from the phase difference between harmonics of the current and voltage at every order by means of the discriminating section.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a harmonic wave detecting device which is provided in a power receiving section of various electric power facilities and detects a harmonic wave.

[0002]

2. Description of the Related Art Conventionally, in high-voltage or high-voltage power-supply / demand self-use equipment, which is an example of power equipment, in order to protect the self-use equipment from harmonics, a harmonic detection device for a power receiving section formed by a digital relay or the like Therefore, it is necessary to detect harmonics and open the circuit breaker.

In the conventional harmonic detecting device of this type, based on the detection of the current and voltage of the received power of the equipment,
The amount of harmonics of current and voltage is individually monitored and detected,
The circuit breaker is opened according to the detection result.

[0004]

In the case of the above-mentioned conventional harmonic detection device, since the amount of generated harmonics is only monitored and detected for each of current and voltage, the harmonics of each order are detected from the detection result. It is not known whether the power is generated inside or outside the power equipment such as private equipment, and high-accuracy detection considering the inflow of the harmonics from the power supply to the power equipment and the reverse outflow, that is, the flowing direction. However, as a result, proper protection from harmonics cannot be achieved.

It is an object of the present invention to detect the flowing direction of harmonics of each order and to enable highly accurate harmonic detection in consideration of this detection.

[0006]

In order to achieve the above-mentioned object, in the harmonic detecting device according to claim 1 of the present application, there is provided a current transformer and an instrument transformer provided in a power receiving portion of power equipment. The detection output is supplied to the current and voltage calculation units, the current and voltage harmonics are obtained by both calculation units and supplied to the determination unit, and the determination unit determines the current and voltage harmonic levels for each order. Based on the phase difference, the direction in which harmonics flow into the electric power equipment is the direction in which the harmonics flow, and the opposite direction is the outflow direction.

Therefore, the current and voltage harmonics are obtained for each order by the current and voltage calculation units, and the direction in which the harmonics flow for each order is determined from the phase difference between the current and voltage harmonics for each order by the determination unit. To be detected.

Therefore, based on the detection of this direction, it is possible to detect the harmonics with high accuracy in consideration of the flowing direction of the harmonics of each order.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Next, one embodiment of the present invention will be described. FIG. 1 is a single-line system diagram of a private facility for extra-high voltage or high-voltage power supply and demand. This is private equipment for high-voltage power demand (hereinafter called private equipment).

Reference numeral 3 is a current transformer provided in the power receiving portion of the private facility 2 for current detection, 4 is a bus bar to which the commercial power source 1 is fed via the current transformer 3, and 5 is a voltage of the bus bar 4. A voltage transformer for voltage detection, 6 is a digital relay to which the secondary side detection output of the current transformer 3 and the voltage transformer 5 is supplied, and a direction determination function together with the current transformer 3 and the voltage transformer 5 Form a harmonic detection device.

Reference numeral 7 is a distribution transformer provided between the bus bar 4 and the distribution line 8 on the downstream side thereof, and 9 is a load connected to the distribution line 8, for example, from a harmonic generation load such as an inverter load. Become.

Further, FIG. 2 shows the configuration of the relay 6, in which 10 and 11 are current and voltage supplied by A / D conversion of the secondary side detection outputs of the current transformer 3 and the transformer 5. These are the calculation units, and the current,
Find harmonics of each voltage by order. Reference numeral 12 is a determination unit to which the calculation results of the calculation units 10 and 11 are supplied, and determines whether the harmonics flow in the inflow direction into the private facility 2 or in the opposite outflow direction by order. To detect.

Then, the commercial power supply 1 is supplied to a distribution transformer 7 via a circuit breaker (not shown), a current transformer 3 and a bus 4, and after being stepped down by this transformer 7, a distribution line 8 is connected. Power is supplied to the load 9 and the like via the load.

At this time, the received electric power of the private facility 2 includes harmonics of a plurality of orders generated inside and outside the private facility 2 such as the load 9, and the direction of flow of these harmonics is the effective component (effective). Based on the positive or negative of (electrical power), if the effective component is positive, it will flow from the commercial power source 1 into the private facility 2, and if the effective component is negative, it will flow from the private facility 2 to the commercial power source 1. , Depends on the order.

Then, the detected output of the current containing the harmonics of the current transformer 3 is A / D converted and supplied to the current calculation section 10, which calculates the current detection waveform by Fourier transform, for example. A calculation is performed, and the fundamental wave a and the harmonics b, c, and d of FIG. 4 are classified and obtained from this waveform.

At the same time, the detection output of the voltage including the harmonics of the instrument transformer 5 is A / D converted and supplied to the voltage calculation unit 11, which converts the voltage detection waveform into the voltage detected by the calculation unit 10. The same Fourier transform is performed to separate and obtain the fundamental wave corresponding to the fundamental wave a and the harmonics b, c, and d of FIG. 4 and the harmonics of each order.

Then, the fundamental wave data of both arithmetic units 10 and 11 and, for example, the harmonic data of each order of 5, 7, 11, and 13 are supplied to the judging unit 12, and the judging unit 12 is based on the given data. , Phase difference of current and voltage harmonics is obtained for each order.

At this time, for example, if the harmonics are generated by the load 9 and flow out from the private facility 2 to the commercial power source 1, the active power becomes negative, and as shown in FIG. 5, the voltage vector is used as a reference. The vector of the obtained current becomes a vector in the forward direction of the angle θ ₁ , and the phase difference between the current and the voltage is obtained as the angle θ ₁ .

[0019] In addition, it is generated on the side of the commercial power source 1
If the harmonics that flow into the
As shown in FIG. 5, the current vector becomes a vector in the opposite direction of the angle θ ₂ , and the phase difference between the current and the voltage is obtained as the angle θ ₂ .

The phase difference between the current and the voltage of the harmonic is 0 ° if the load characteristic of the private facility 2 is inductance.
The range is −90 ° or + 90 ° to + 180 °, and the range 0 ° to + 90 ° or −90 ° to −180 ° for capacitive.

When the phase difference is in the range of 0 ° to ± 90 °, the harmonics have positive active power and flow into the private facility 2, and when the phase difference is larger than ± 90 °, The harmonics have negative active power and flow out of the private facility 2. Therefore, the direction in which the harmonic flows does not relate to the load characteristics of the private facility 2.

Then, the judging section 12 judges and detects the flowing direction of the harmonics for each order from the phase difference between the current and the voltage for each order.

Further, the ratio of the harmonic of each order to the fundamental wave is obtained as the harmonic current content rate, and the result is, for example, 0 to +1 mA in the inflow direction and 0 to -1 mA in the outflow direction. Evaluation is made with an analog signal of 0 to ± 1 mA.

Then, based on this evaluation, when the harmonics are in a state of being higher than the allowable value, an instruction to turn off the circuit breaker such as the power receiving end is generated to prevent an accident due to the harmonics.

Therefore, high-accuracy harmonic detection can be performed in consideration of the flowing direction of the harmonic of each order based on the evaluation of each harmonic order, and based on this detection, highly accurate accident prevention and the like can be achieved. And, of course, it can be applied to the harmonic detection of various electric power equipment.

[0026]

The present invention has the following effects. Based on the detection output of the current transformer 3 and the instrument transformer 5, the electric current. Each of the voltage calculation units 10 and 11 obtains the harmonics of the current and voltage for each order, and the determination unit 12 detects the flowing direction of the harmonics of each order from the phase difference between the harmonics of the current and voltage of each order. This makes it possible to detect harmonics with high accuracy in consideration of this detection.

[Brief description of drawings]

FIG. 1 is a system diagram of an embodiment of the present invention.

2 is a detailed block diagram of a portion of FIG. 1. FIG.

FIG. 3 is a waveform diagram of a current including harmonics.

FIG. 4 is a waveform diagram of a fundamental wave and a harmonic wave separated from the current of FIG.

5 is a vector diagram for explaining the operation of the determination unit in FIG.

[Explanation of symbols]

 3 Current transformer 5 Transformer for instrument 10 Current calculation unit 11 Voltage calculation unit 12 Judgment unit

Claims (1)

[Claims] 1. A detection output of a current transformer and an instrument transformer provided in a power receiving section of a power facility is supplied to current and voltage calculation sections, respectively, and both current and voltage harmonics are ordered by both calculation sections. It is separately obtained and supplied to the determination unit, and the direction in which the harmonic flows from the phase difference between the harmonics of the current and voltage for each order by the determination unit is either the inflow direction to the power equipment or the outflow direction. A harmonic detection device characterized by detecting whether or not it is classified by order.