JP6678539B2 - Phase loss detection system, phase loss detection device, and phase loss detection method - Google Patents

Description

  An embodiment of the present invention relates to a phase loss detection system, a phase loss detection device, and a phase loss detection method.

  In a power generation facility such as a power plant, a protective relay is connected to a transformer that transforms a high voltage of three-phase alternating current, and measures are taken in the event of a ground failure or a short circuit.

  By the way, it is rare that an insulator or the like connected to the primary side of the transformer is damaged and one of three phases, for example, loses phase (hereinafter, this is referred to as "one-phase open fault").

  A one-phase open fault in a three-phase transformer is difficult to find because a voltage is also induced in the open phase. For example, a one-phase open fault occurs on the primary side of the transformer, and the value of the abnormal current is a protection relay. If the set value is reached, it can be detected.

  However, when a one-phase open fault that does not involve a ground drop or short circuit occurs, the value may not fluctuate up to the set value of the protective relay depending on the equipment configuration and load conditions. In such a case, the one-phase open fault cannot be detected. Sometimes.

  For this reason, conventionally, in addition to mechanical detection, an attempt is made to detect a one-phase open failure that does not involve a ground drop or a short circuit by combining artificial detection.

JP-A-2005-006076

  Conventionally, when a one-phase open fault that does not involve a ground drop or short circuit occurs, the value may not fluctuate up to the set value of the protective relay depending on the equipment configuration and load conditions. In this case, the one-phase open fault can be detected Instead, they combined artificial detection.

  An object of the present invention is to provide an open-phase detection system, an open-phase detection device, and an open-phase detection device that can mechanically detect a single-phase open failure that does not involve a ground drop or a short circuit irrespective of the equipment configuration and load conditions. It is to provide a phase detection method.

An open-phase detection system according to an embodiment includes a three-phase stationary induction electric device having a primary-side circuit in which an excitation current flows through wiring for each phase, and a current detection for detecting the excitation current of each phase of the primary-side circuit. Detector, an extraction unit for extracting a harmonic from the excitation current detected by the current detector, and the primary source of the excitation current detected according to whether or not the harmonic is extracted by the extraction unit. A determination unit that determines whether the wiring of the side circuit is in an open state or a connection state, wherein the determination unit has an amplitude value of a fundamental wave exceeding a first threshold value previously set for the fundamental wave, If the amplitude value of the harmonic does not exceed the second threshold value previously set for the harmonic, it is determined that the harmonic has not been extracted, and the wiring is determined to be open.
In addition, the open-phase detecting device according to the embodiment includes an extraction unit configured to extract a harmonic from an excitation current flowing through a wiring for each phase of a primary circuit of the three-phase static induction electric device, and whether the harmonic is extracted. or the wiring of the primary side circuit of the detection source of the excitation current anda determination section for determining the connected state or the open state in accordance with, the determining unit, the amplitude value of the fundamental wave advance When the amplitude exceeds the first threshold set for the fundamental wave and the amplitude value of the harmonic does not exceed the second threshold set in advance for the harmonic, the harmonic is not extracted, and It is determined that the wiring is open.
Further, in the phase loss determination method according to the embodiment, the extraction unit extracts a harmonic from an excitation current flowing through a wiring for each phase of a primary circuit of the three-phase static induction electric device, and the determination unit determines the harmonic. A phase loss detection method for determining whether the wiring of the primary circuit from which the excitation current is detected is in a connected state or an open state according to whether or not the excitation current is extracted. If the amplitude value of the harmonic does not exceed the first threshold value set for the fundamental wave in advance and the amplitude value of the harmonic does not exceed the second threshold value set for the harmonic wave in advance, the harmonic is not extracted. It is determined that the wiring is open.

It is a figure showing composition of an open phase detection system of a 1st embodiment. FIG. 3 is a connection diagram of a transformer used in a power plant or the like. It is a figure showing an equivalent circuit including a transformer. FIG. 4 is a diagram showing a flow of a power supply reason when a certain wiring is disconnected in the circuit of FIG. 3. FIG. 7 is a diagram showing an example in which some open phases cannot be detected only by the presence or absence of an excitation current. It is a figure showing a waveform of an exciting current of a transformer. FIG. 7 is a diagram in which a fundamental wave, a third harmonic, and a fifth harmonic are decomposed from the exciting current having the waveform of FIG. 6. It is a figure which shows the distortion rate of the harmonic component when the amplitude of the fundamental wave of the exciting current of a transformer is set to one. FIG. 6 is a diagram illustrating changes in a fundamental wave and a harmonic of an exciting current with respect to an applied voltage. It is a figure showing the circuit composition of a 2nd embodiment. FIG. 14 is a diagram illustrating a circuit configuration of another embodiment (modification).

Hereinafter, embodiments will be described in detail with reference to the drawings.
FIG. 1 is a diagram showing a phase loss detection system according to the first embodiment.

  As shown in FIG. 1, the open-phase detection system according to the first embodiment includes a transformer 1 as a three-phase static induction electric device, and wirings 4 a and 4 b of each phase of a primary circuit 2 of the transformer 1. 4c, and a phase loss detecting device 6 to which the current detector 5 of each phase is connected.

  The transformer 1 includes a primary circuit 2 including wirings 4a, 4b, 4c and coils of each phase continuing to the outside, and a secondary circuit 3 having a coil whose voltage is induced by the coils of the primary circuit 2. And In this transformer 1, an exciting current is applied to each of the wirings 4a, 4b, and 4c of the primary circuit 2 so that electric power corresponding to the winding ratio of the coils of the primary circuit 2 and the secondary circuit 3 is 2. It is induced in the secondary circuit 3. That is, the transformer 1 has a primary circuit 2 in which an exciting current flows through the wirings 4a, 4b, 4c for each phase, and a secondary circuit 3 electromagnetically coupled to the primary circuit 2.

  The current detector 5 detects a current flowing through each phase wiring 4a, 4b, 4c. As the current detector 5, for example, a current transformer using electromagnetic induction usually called CT, an optical CT using the Faraday effect, or the like is used. CT is an abbreviation for a current transformer (current converter).

  Based on the exciting currents detected by the current detectors 5 of the respective phases, the phase loss detecting device 6 determines whether or not the wires 4a, 4b, 4c of the corresponding phase of the primary circuit 2 from which the exciting current is detected are open. If there is an open wiring, an alarm is output to that effect.

  The phase loss detection device 6 includes an input converter 61, a filter unit 62, a determination unit 67, and an alarm output unit 68.

  The input converter 61 converts the input excitation current (current signal) into a voltage signal. The filter unit 62 has an analog filter 63, an AD converter 64, and a digital filter 65.

  The analog filter 63 attenuates a high-frequency noise component (for example, a component obtained by converting a current of about 10 amps into a voltage) included in an input excitation current converted voltage signal.

  The AD converter 64 converts an exciting current (analog signal) in which a noise component (high-frequency component) is attenuated by the analog filter 63 into a digital signal.

  The digital filter 65 separates a commercial frequency (a fundamental wave fm of 50 Hz or 60 Hz) contained in the digital signal converted by the AD converter 64 and a harmonic component such as a third harmonic 3fm and a fifth harmonic 5fm.

  In this example, the filter unit 62 extracts one or more harmonics that are integral multiples of the exciting current to the fundamental wave fm. In other words, the filter unit 62 is a band-pass filter. The filter unit 62 converts the voltage signal converted by the input converter 61 into a fundamental wave fm, a triple harmonic 3fm of three times the frequency, and a five times harmonic of the five times the frequency. It functions as an extraction unit that extracts the waves 5fm and the like.

  The determination unit 67 receives the reference voltage Vref. The determination unit 67 samples each signal at a predetermined period (operation period) in accordance with the cycle of the reference voltage Vref. The reference voltage Vref is a signal for obtaining synchronization timing, and is an AC voltage applied to any of the wires (the wire 4c in this example) of the primary circuit 2 or a normal commercial AC voltage (100 V, 50 Hz sine wave). Signal).

  The determination unit 67 has a threshold for determination for each of the fundamental wave fm and the harmonics 3fm and 5fm. The threshold value for the amplitude value of the fundamental wave fm is defined as a first threshold value, and the threshold value for the amplitude values of the harmonics 3fm and 5fm is defined as a second threshold value. As the second threshold value of the harmonic, a threshold value corresponding to each of the third harmonic 3fm and the fifth harmonic 5fm is set.

  When the amplitude value of the detected fundamental wave exceeds the first threshold set in advance and the amplitude value of the harmonic does not exceed the second threshold set in advance, the determination unit 67 determines that the current is a charging current. It is determined that the wiring is open.

  When the amplitude value of the detected fundamental wave exceeds a preset first threshold value and the amplitude value of a harmonic exceeds a preset second threshold value, the determination unit 67 determines that the current is an exciting current. It is determined that the wiring is in a connected state.

  The determining unit 67 determines the primary side of the excitation current detection source according to the presence or absence of the fundamental wave fm and the harmonics 3fm and 5fm exceeding the predetermined thresholds (the first threshold and the second threshold of the amplitude value) extracted by the filter 62. It is determined whether the wirings 4a, 4b, 4c of the circuit 2 are open or connected.

  Specifically, the determination unit 67 determines the magnitude of the excitation current in accordance with the magnitude relationship between the excitation current extracted by the filter unit 62 and the threshold value at which it is determined that the harmonic is flowing (whether it is larger or smaller than the threshold value). It is determined whether or not the wires 4a, 4b, and 4c of the primary circuit 2 as the detection source are in an open state (at least one phase has an open failure). When the amplitude value of the extracted one or more harmonics 3fm, 5fm does not exceed the second threshold, the determination unit 67 determines that no harmonic has been extracted and the wirings 4a, 4b, 4c are open. Is determined.

  When only the presence or absence of a harmonic is used without using the fundamental wave, that is, when the amplitude value of the harmonic exceeds a second threshold value set in advance, the current is an exciting current, and the wiring is in a connected state. When the value is equal to or less than the second threshold value, the current may be simply determined to be an open state because the current is a charging current.

  That is, the determination unit 67 determines whether the wires 4a, 4b, and 4c of the primary circuit 2 from which the excitation current is detected are open or connected according to whether or not the harmonics 3fm and 5fm are extracted by the filter unit 62. I do.

  Then, as a result of the determination, when there is a wire in the open state (the wiring 4b in this example), the determining unit 67 outputs an alarm signal indicating that the wiring 4b is in the open state to the alarm output unit 68.

  The alarm output unit 68 is, for example, a speaker, a buzzer, or a display device, and is a notification unit or an alarm unit that outputs an alarm indicating that the wiring 4b is in an open state based on an alarm signal received from the determination unit 67.

  When there is a broken portion P in the wiring 4b as in the example of FIG. 1, the opening of the wiring 4b is notified by an alarm sound or an alarm display.

  That is, the determination unit 67 determines the presence / absence of a phase loss in the corresponding wiring based on the harmonics included in the excitation current. It becomes possible. This principle is described below.

  A problem in measuring the exciting current is that the charging current flows through the line even when the exciting current is not flowing. This will be described with reference to FIGS.

FIG. 2 is a connection diagram of a transformer 1 generally used in a nuclear power plant.
As shown in FIG. 2, a transformer 1 having a Y-connection on both the primary side and the secondary side is used. In order to stabilize the voltage, it is general that the winding is generally formed to include a Δ-connection winding.

  For this reason, even if a disconnection failure occurs in any one of the wires connected to the Y connection on the input side, in the case of no load or light load, a voltage almost normal is induced even in the disconnection phase. However, the conventional method of detecting a phase loss by detecting a voltage drop has caused an event in which a phase loss cannot be detected.

  In order to solve this problem, the presence or absence of the exciting current of the transformer 1 is measured to determine the presence or absence of the phase loss. FIG. 3 shows an equivalent circuit of the circuit including the transformer 1 at this time. Actually, three-phase alternating current is used. However, since the missing-phase detecting device 6 determines the presence or absence of the exciting current for each phase, only one phase is illustrated.

As shown in FIG. 3, the charging current I _CS 9 due to the stray capacitance Cs8 of the line and the exciting current I _L 10 of the transformer 1 are flowing through the line. Here, the case of installing a CT for measuring the excitation current I _L 10 transformer 1 near, CT will output by observing only the excitation current I _L.

Next, with reference to FIG. 4, a case where a disconnection failure occurs in any of the wirings 4a, 4b, and 4c of the primary circuit of the transformer 1 will be considered.
As shown in FIG. 4, when a disconnection occurs at a point X relatively far from the transformer 1 (see FIG. 3), the exciting current of the transformer 1 does not flow in the phase of the disconnected wiring (disconnection phase). It will be 0 amps.
On the other hand, the charging current of the line is not supplied from the power supply 7 because of the disconnection.

However, as described above, the transformer 1 is provided with the stabilizing winding, and even in the disconnection phase, the voltage _EL 30 that is substantially the same as in the normal state is induced in the primary circuit 2 of the transformer 1. Therefore, so that the charging current flows _{I CS2} 40 from the voltage _E L 30 to the line.

At this time, the charging current I _{CS2 40} is a phase of current advances supplied from the voltage E _L 30, excitation of sound when the excitation current I _L 10, i.e. delayed phase supplied from the power source 7 current I _L 10 And the current is exactly in phase. And the charging current I _{CS2 40,} for example, in the case of CV cable, significantly large, the line length up to the fault point may also be the same as the exciting current I _L 10.

  In other words, it is not sufficient to determine the disconnection by simply detecting the exciting current, and it is important to distinguish between the charging current and the exciting current.

  FIG. 5 shows an example in which a CV cable is used in the secondary circuit 3 of the transformer 1 as a second example in which the presence or absence of the excitation current cannot be determined.

When a CV cable is used for the secondary circuit 3 of the transformer 1, a relatively large charging current _ICS330 flows as shown in FIG. The charging current I _CS3 30 becomes a current of 1 / turn ratio of the transformer 1 and flows the _leading component current I _CS31 31 to the primary side of the transformer 1. _{CS 31} 31 are exactly opposite phase as the exciting current _I L 10 of the transformer 1, both so that the cancel.

Here, depending on the length of the CV cable, it advances component of the current I _{CS 31 31} and the exciting current I _L 10 is exactly the same size, that is, that when the current becomes zero may occur. This indicates the same current value as in the case where the disconnection has occurred near the transformer 1 on the primary side of the transformer 1, so that the detection of the disconnection by the detection of the excitation current is no longer possible.

Therefore, by paying attention to the difference in nature of the excitation current I _L 10 and the charging current I _{CS3 30,} for the case where there is influence of the charging current is also devised a technique to accurately determine the presence or absence of excitation current I _L 10.

As the difference nature of the excitation current _I L 10 charging current _{I CS3} 30, there is the generation of harmonic current. The charging current I _{CS3 30} is Whereas contains little harmonic component with respect to the power supply frequency, the excitation current I _L 10 is has a nonlinearity to the excitation characteristics of the transformer 1 has a relatively large harmonic component.

  FIG. 6 shows an example of the waveform of the exciting current of the transformer 1. It can be seen that the waveform 70 of the exciting current shown in FIG. 6 is a waveform that is greatly distorted, which can no longer be called a sine wave, because a harmonic is superimposed on the fundamental wave of the sine wave.

  The waveform 70 is decomposed (separated) into components of a fundamental wave and a harmonic. The result is shown in FIG. It should be noted that the point of the phase 0 of the applied voltage, not shown, is plotted as the time origin. Each harmonic current of the fundamental wave 71, the third harmonic 72, and the fifth harmonic 73 flows with a phase delay of 90 ° with respect to the applied voltage.

  FIG. 8 shows harmonic components when the amplitude of the fundamental wave component included in the exciting current of the transformer 1 is set to 1. In FIG. 8, it can be seen that a third harmonic 72 having a distortion rate substantially equal to the current of the fundamental wave 71 and a fifth harmonic 73 having a distortion rate of about 50% flow.

  When the transformer 1 is in a no-load state, the only cause of such a harmonic flow is the exciting current. By measuring the harmonic current, the transformer 1 can be clearly distinguished from other currents such as the line charging current. 1 can be measured.

  Considering the case where a load current flows through the transformer 1, many load currents include an iron core such as a motor, and there are many loads such as a rectifier circuit in which a current non-linearly responds to a voltage.

  Therefore, when the load current is large, it is difficult to detect the phase loss using the harmonic current anymore. After locking the output of the phase loss detection device 6, other methods of detecting the phase loss such as the detection of the voltage drop are performed. It is desirable to combine

  As a method of determining the harmonic component of the load current and the harmonic component of the exciting current, the phase of the exciting current described above can be used. In other words, the load current is generally resistive and has the same phase as the applied voltage, whereas the exciting current has a 90 ° delayed phase. Therefore, the load current is detected by detecting a current having a 90 ° delayed phase with respect to the applied voltage. It is possible to measure by dividing it to some extent.

  As described above, according to the first embodiment, according to the presence / absence of a fundamental wave and a harmonic exceeding a predetermined threshold value included in the excitation current detected by the current detector 5 provided in the wirings 4a, 4b, and 4c of each phase. To determine whether any of the wires 4a, 4b, and 4c of the primary circuit 2 that is the source of the excitation current is in the connected state or the open state, so that no ground drop or short circuit occurs irrespective of the equipment configuration or load condition. A one-phase open fault can be detected mechanically.

Next, a second embodiment will be described with reference to FIGS.
It is necessary to pay attention to the fact that the exciting current of the transformer 1 greatly varies depending on the applied voltage. FIG. 9 shows an example of a change in the current of the fundamental wave 71 and the harmonics 72 and 73 of the excitation current with respect to the applied voltage.

  As shown in FIG. 9, the exciting current greatly changes depending on the voltage applied to the transformer 1, and this change is particularly noticeable in the harmonic current.

  Therefore, in the second embodiment, as shown in FIG. 10, an instrument transformer PT as a voltage detector is provided on one of the wires 4a, 4b, and 4c of the primary circuit 2 of the transformer 1, and A circuit is configured to input the voltage detected by the transformer PT to the determination unit 67 of the phase loss detection device 6 via the voltage regulator 69, the analog filter 63, the AD converter 64, and the digital filter 65.

  The instrument transformer PT is a measuring device for acquiring the reference voltage Vref, and here, detects an AC voltage applied to any wiring (for example, the wiring 4c) of the primary side circuit 2. And

  When the reference voltage Vref detected by the instrument transformer PT is input to the open-phase detecting device 6, the voltage must be corrected, so that a voltage regulator 69 is provided. Also, since the voltage corrected by the voltage regulator 69 has a noise component, the noise corrected from the voltage corrected by the voltage regulator 69 is passed through the analog filter 63, the AD converter 64, the digital filter 65, and the like. Filter components.

  In the case of the second embodiment, the applied voltage of the transformer 1 is detected (measured) at the same time as the exciting current by the instrument transformer PT, and is input to the determination unit 67. The determination unit 67 changes a threshold value for determining the presence or absence of the excitation current based on the detected (measured) applied voltage.

  As described above, according to the second embodiment, in addition to the effect of the first embodiment, the applied voltage of the transformer 1 is measured at the same time as the exciting current and input to the determination unit 67. Since the threshold value for determining the presence or absence of the exciting current is changed according to the applied voltage, the exciting current can be detected in accordance with the fluctuation of the applied voltage.

  Although an embodiment of the present invention has been described, this embodiment is provided by way of example and is not intended to limit the scope of the invention. This new embodiment can be implemented in other various forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and their equivalents.

  In the first embodiment, one current detector 5 is provided for each of the wires 4a, 4b, and 4c. However, as shown in FIG. 11, the number of signal waveforms to be detected is provided for each of the wires 4a, 4b, and 4c. Only the current detectors 5a, 5b and 5c are provided.

  For example, the current detector 5a is for detecting a fundamental wave, the current detector 5b is for detecting a third harmonic, and the current detector 5c is for detecting a fifth harmonic. Then, a circuit is configured to input the detected current to the open-phase detecting device 6.

In this case, the filter unit 62 extracts a signal of a corresponding waveform (a fundamental wave fm, a third harmonic 3fm, a fifth harmonic 5fm, etc.) from each detected current, and inputs the extracted signal to the determination unit 67.
By configuring the circuit in this manner, it is not necessary to decompose (separate) the reference wave and the harmonic in the filter unit 62, and it is only necessary to extract individual signals (waveforms).

  Furthermore, in the above-described embodiment, an example in which a general iron core CT is used as the current detector has been described. However, a very small current of, for example, about 0.2 A, which is not used for detecting a normal excitation current, is detected. By arranging the optical CT dedicated to phase loss detection on each of the wirings 4a, 4b, and 4c, the noise component is saturated and cannot be detected, but only a weak excitation current can be detected.

  By using the optical CT as the current detector, the cable to the open-phase detecting device 6 can be made thin. In addition, since detection in a low voltage region becomes possible in accordance with the number of turns of the optical fiber, the weight can be reduced, for example, when used as a gas insulated switchgear (GIS device).

  Further, each component of the open-phase detecting device 6 shown in the above-described embodiment may be realized by a program installed in a storage such as a hard disk device of a computer, and the above-mentioned program may be realized by a computer-readable electronic medium. And the functions of the present invention may be realized by causing a computer to read the program from an electronic medium.

  Examples of the electronic medium include a recording medium such as a CD-ROM, a flash memory, and a removable medium. Furthermore, the present invention may be realized by distributing and storing components in different computers connected via a network, and communicating between the computers in which the respective components function.

DESCRIPTION OF SYMBOLS 1 ... Transformer, 11 ... Primary winding, 12 ... Secondary winding, 13 ... Stabilization winding, 2 ... Primary circuit, 3 ... Secondary circuit, 4a, 4b, 4c ... Wiring, 5 ... Current detector, 6: phase loss detecting device, 7: power supply, 8: floating capacitance Cs, 9: charging current I _CS , 10: exciting current I _L , 20: CT, 30: secondary charging current I _CS3 , 31 ... Primary conversion secondary-side charging current I _CS31 , 61... Input converter, 62... Filter unit, 63... Analog filter, 64.

Claims (5)

A three-phase stationary induction electric device having a primary-side circuit in which an exciting current flows through wiring for each phase;
A current detector for detecting the exciting current of each phase of the primary side circuit;
An extraction unit configured to extract a harmonic from the excitation current detected by the current detector,
A determining unit that determines whether the wiring of the primary circuit, which is the source of the excitation current, is in an open state or a connected state according to whether or not the harmonic is extracted by the extracting unit;
With
The determination unit includes:
If the amplitude value of the fundamental wave exceeds a first threshold value set in advance for the fundamental wave and the amplitude value of the harmonic does not exceed a second threshold value set in advance for the harmonic wave, the harmonic is extracted. It is determined that the wiring is in an open state,
Open phase detection system. The extraction unit includes:
Extracting one or more harmonics that are integral multiples of the excitation current with respect to the fundamental wave,
The determination unit includes:
2. The open-phase detection system according to claim 1, wherein when the amplitude value of the extracted one or more harmonics does not exceed the second threshold, it is determined that the wiring is in an open state.   3. The phase loss detection system according to claim 1, further comprising an alarm output unit that outputs an alarm when the determination unit determines that the wiring is in an open state. 4. An extraction unit configured to extract a harmonic from an excitation current flowing through a wiring for each phase of a primary circuit of the three-phase static induction electric device;
A determination unit configured to determine whether the wiring of the primary circuit that is the source of the excitation current is connected or disconnected according to whether or not the harmonic is extracted;
With
The determination unit includes:
If the amplitude value of the fundamental wave exceeds the first threshold value set in advance for the fundamental wave, the amplitude of the harmonic does not exceed a second preset threshold value for the harmonics, the harmonics It is determined that the wiring is in an open state as not being extracted,
Open phase detection device. An extracting unit that extracts a harmonic from an exciting current flowing through a wiring for each phase of a primary circuit of the three-phase static induction electric device;
A determining unit that determines whether the wiring of the primary circuit, which is a source of the excitation current, is connected or disconnected according to whether or not the harmonic is extracted;
An open phase detection method,
The determination unit includes:
If the amplitude value of the fundamental wave exceeds a first threshold value set in advance for the fundamental wave and the amplitude value of the harmonic does not exceed a second threshold value set in advance for the harmonic wave, the harmonic is extracted. It is determined that the wiring is in an open state,
Open phase determination method.

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