JPH02210270A - Optical zero-sequence/positive-sequence current detection device - Google Patents

Abstract

PURPOSE:To measure a positive-phase current with high sensitivity by additionally providing a separate transformer. CONSTITUTION:Ring iron cores 8a-10a are arranged on each 3-phase transmission/distribution line and the 1st transformers 8-10 are provided with the secondary windings 8b-10b and tertiary windings 8c-10c wound up to these cores. These windings 8b-10b are connected to a common resistor 11 for load in parallel and also the windings 8c-10c are connected in series then a photoelectric voltage sensor 12 is provided between both terminals of this series circuit to detect a voltage proportional to a zero-phase current. At this time, the ring iron cores 13a, 14a are arranged in at least two phases of the circuits for the windings 8b-10b and the 2nd transformers 13, 14 are provided with the secondary windings 13b, 14b and the tertiary windings 13c, 14c wound up to these cores. Resistors 15, 16 are connected respectively to the circuits of each winding 13b, 14b of these transformers 13, 14, and photoelectric voltage sensors 17, 18 are connected to the circuits of the windings 13c, 14c. Thus, optical signals are conducted to a signal processing circuit for positive-phase current through an optical transmission passway and detected.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides an optical zero-sequence/positive-sequence current detection device for detecting zero-sequence current and positive-sequence current of power transmission and distribution lines with high sensitivity and high reliability. Regarding.

[Conventional technology]

In the field of power distribution, current transformers are generally used to measure current in high-voltage circuits, but optical current detectors have traditionally been proposed to ensure insulation and noise resistance. There is.

For example, as shown in FIG. 5, an optical magnetic field sensor 25 made of a magneto-optic crystal having a Faraday effect is sandwiched between a gap provided in a magnetic core 24 through which a negative order conductor 26 passes, and transmission is transmitted from an optical transmission path 2. There is a system in which the modulated light of the transmitted light is taken out from the optical transmission path 3. However, with this method,
Despite the presence of air gaps, there is a problem in that large currents cannot be accurately measured due to the magnetic saturation of the magnetic core 24, and the accuracy is not high enough to measure small currents.

On the other hand, as shown in FIG. 6, a secondary winding 13b and a tertiary winding 13c are wound around an annular magnetic core 13a through which a negative conductor 26 passes, and a resistor is connected to the output terminal of the secondary winding 13b. There is a method in which a photo voltage sensor 17 using an electro-optic effect element is connected to both ends of the tertiary winding 13c, and the current in the primary conductor 26 is measured from changes in light.

With this method, the voltage can be greatly amplified by increasing the turns ratio, so even small currents can be measured with high accuracy. Further, since magnetic saturation of the magnetic core 13a is suppressed by the current generated in the secondary winding, a large current can be measured.

On the other hand, in order to detect the weak zero-sequence current that flows due to the stray capacitance of the line when a ground fault occurs on an ungrounded power transmission/distribution line, a three-phase transmission line is used as shown in Figure 4. Iron cores 3a and 9a are placed on each of the distribution lines.

10a, secondary windings 8b, 9b, 10b and tertiary windings 8c, 9c.

A first transformer 8,9.10 wound with 10c is provided, 3
The phase secondary windings 8b, 9b, 10b are connected to a common resistor 1.
1, and three-phase tertiary windings 8c, 9c, I
The OCs are connected in series and a photovoltage sensor 12 is connected between both terminals.
According to this method, a voltage proportional to the zero-sequence current generated in the power transmission and distribution lines is applied to the tertiary windings 8c and 9c. , occurred at 10c,
This is the photo voltage sensor 12 that is not affected by electromagnetic effects.
If applied, the zero-sequence current can be measured accurately and precisely. In addition, in FIG. 4, 1 is an optical transmitter, 2
is an optical transmission path, 3 is an optical reception path, 4 is an optical receiver, 5 is a signal processing circuit, 6 is a display device, 7 is a switch, 7a, 7b,
7c is a three-phase switch electrode.

Now, let's consider using the zero-sequence current detection method shown in Figure 4 to measure the zero-sequence current of a three-phase power transmission and distribution line, and at the same time measure the carrying current (positive-sequence current) of each phase. . As mentioned above, it is more useful as a sensor to apply a voltage to the optical voltage sensor 12 by some method. For example, a resistor is connected in series to each phase of the secondary windings 8b, 9b, and 10b of the zero-sequence current detection method, and the voltage generated across the resistors is measured using the optical voltage sensor 12 for measuring the positive-sequence current of each phase. Suppose that it is applied to

In order to increase the sensitivity of the sensor, it is necessary to increase the resistance value and generate a high voltage, but this has many disadvantages, such as increasing the load on the current transformer and increasing the cross-sectional area of the core. .

Therefore, as mentioned above, we use a single CT (current transformer) tertiary winding method in which the voltage generated in the resistor of the secondary winding wound around the magnetic core is amplified by the tertiary winding and measured by a photovoltage sensor. It is possible that However, the magnetic core of this single CT for positive phase and the zero-sequence current detection method (3CT connected tertiary winding method)
There is no point in principle in using the same magnetic core. This is because, as a result, a zero-phase magnetic field passes through the operating 3CT core, so a 30T core cannot detect the positive phase.

[Problem to be solved by the invention]

As mentioned above, with the 3CT connected tertiary winding method, it is not possible to measure the positive sequence current at the same time, and even if accessories for measuring the positive sequence current are installed, it is not possible to measure the positive sequence current with high reliability, safety, and high performance. There are many factors that make it difficult to achieve this goal.

An object of the present invention is to solve this problem and provide a zero-sequence current detector that can also measure positive-sequence current with high accuracy by adding a few parts to the zero-sequence current detector.

[Means to solve the problem]

In order to achieve this objective, the optical zero-phase/positive-sequence current detection device of the present invention has a ring-shaped iron core placed on each of the three-phase power transmission and distribution lines, and a secondary winding and a tertiary winding on each iron core. The secondary windings of these first transformers are connected in parallel to a common resistor, and the tertiary windings of each phase are connected in series. In an optical zero-sequence current detection device comprising a means for detecting a voltage proportional to a zero-sequence current by providing an optical voltage sensor using an electro-optic crystal between both terminals of the circuit, at least two of the secondary winding circuits A second transformer is provided in which a ring-shaped iron core is arranged in the phase, a secondary winding and a tertiary winding are wound around each of the iron cores, and a resistor is provided in each secondary circuit of this second transformer. The second transformer is connected to the tertiary circuit of the second transformer, and includes a means for detecting the positive sequence current by providing a photovoltage sensor between both terminals of each tertiary circuit of the second transformer.
Effect] The present invention provides a second transformer in the secondary winding of the previously proposed zero-sequence current detection device shown in FIG. That is,
The iron cores are placed in at least two phases of the secondary windings, each of which is wound around the iron core placed in each of the three-phase power transmission and distribution lines, and the secondary winding and the tertiary winding are wound on each of the secondary windings. It is a transformer. A resistor is connected to the secondary winding of the second transformer for each phase separately, and a photovoltage sensor using an optical crystal is connected to the tertiary winding for each phase, and the optical signal is emitted. - Transmitted and received from the light receiving element and sent to the signal processing circuit.

A secondary current flows through the secondary winding circuit of the first transformer due to the positive sequence current being applied to the three phases. This secondary current induces a voltage in the secondary winding of the second transformer, causing a current to flow, generating a voltage in the tertiary winding and applying it to the optical voltage sensor, which detects the tertiary voltage from the change in the optical signal. Measured to detect the positive sequence current of the two phases with the second transformer. If the second transformer is installed in only two phases, the positive sequence current of the remaining phases can be obtained by vectorially subtracting the vector sum of the detected positive sequence currents of the two phases from the zero sequence current. obtained by. If the second transformer is provided for all three phases, the positive sequence current of each phase can be directly obtained from the output of the sensor of each phase.

〔Example〕

Hereinafter, the present invention will be specifically explained based on Examples.

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. In the figure, 1.31 is an optical transmitter that sends out light;
2.32 and 3.33 are optical transmission paths and optical reception paths using optical fibers, 4 and 34 are optical receivers, 5.35 is a signal processing circuit, and 6.36 is a display device.

Reference numeral 7 denotes a switch filled with arc-extinguishing gas, and switch electrodes 7a, 7b, and 7c connected to each of the three-phase power transmission and distribution lines are housed in this switch. 8°9.10
is a transformer, and each of the switch electrodes 7a, 7b, and 7c has an annular iron core 8a disposed surrounding the electrodes.
9a, 10a are provided, and these iron cores 3a, 9
a.

Secondary windings 8b, 9b, 10b and tertiary windings 3c, 9c, IOC are wound around 10a so that the transformation ratios of the respective transformers 8, 9, 10 are equal. A burden resistor 11 is connected in parallel to the secondary windings 8b, 9b, 10b, and the tertiary windings 8c, 9c, 10
c are connected to each other in series, and the terminals on both sides are connected to the electrodes of the photovoltage sensor 12, respectively. This optical voltage sensor 12 includes an electric field operated element such as a Pockels element,
For example, 1Tao, OP to LiNbO5 (to H
-PO4), BGO(To+zGeOao).

Ferroelectric materials such as B50 (Bi, 2SiO, .) are mainly used.

Reference numerals 13 and 14 designate a second transformer for detecting positive sequence current, and are provided with annular iron cores 13a and 14a arranged around the secondary winding of the first transformer.
14a has secondary windings 13b, 14b and tertiary winding 1 so that the transformation ratios of each transformer 13.14 are equal.
3c and 14c are wound. These secondary windings 1
3b.

Load resistors 15 and 16 are connected to the tertiary windings 14b and 14b, respectively, and a photovoltage sensor 17 is connected to the tertiary windings 13C and 14C.
．． 18 are connected to each other, and an optical signal is guided to a signal processing circuit for positive-sequence current through an optical transmission line.

This optical voltage sensor 12. A voltage detection system using 17.18 is shown in FIG. 1^ is a pulse generator,
The output pulse is converted into an optical pulse by the electro-optical conversion element IB, and is applied to the optical voltage sensor 12 via the optical transmission path 2 using an optical fiber. These pulse generators 1
^ and the electro-optical conversion element IB are provided in the optical transmitter 1. The photovoltage sensor 12 has a transparent electrode 2 on the end surface.
19. Field-operated element with 0.20. Polarizer 21.
It is composed of an A wavelength plate 22 and an analyzer 23.

The transparent electrodes 20.20 are the tertiary windings 3c and 9c in FIG.
, are electrically connected to both ends of the IOC series circuit. The optical output from the analyzer 23 is transmitted via an optical receiving path 3 using an optical fiber to an optical receiver 4 equipped with an optical-to-electrical conversion element, where it is converted into an electrical signal and sent to a signal processing circuit 5. It will be done.

Next, the operation of the block diagram in FIG. 1 will be explained. When the power transmission and distribution lines (not shown) connected to the switching electrodes 7a, 7b, 7c of the switch 7 are normally energized, the secondary windings of the first transformers 8, 9, 1.0 Bb, gb.

Since the sum of the secondary currents induced in each of the tertiary windings 3c, 9c, 1.10b becomes zero, no voltage is generated across the burden resistor 11. No voltage is generated at Oc. Therefore, the continuous light transmitted from the optical transmitter 1 to the optical transmission path 2 passes through the optical voltage sensor 12 to which no voltage is applied, and is output from the optical reception path 3 to the optical receiver 4. Optical receiver 4
converts the optical signal into an electrical signal and outputs it to the signal processing circuit 5. The signal processing circuit 5 amplifies the input electrical signal, performs signal processing, and outputs the signal to the display device 6.

Next, when one phase of the power transmission and distribution line has a ground fault and a zero-sequence current flows through the switching electrode 7a of the switch 7, a secondary current and A transformer 9.10 in which a secondary voltage is generated and provided on the other switching electrodes 7b, 7c
The same secondary voltage is applied to each of the secondary windings 9b, 10b, and a detection voltage is induced in the tertiary windings 3c, 9c, IOC of the respective transformers 8, 9°lO. Tertiary windings 8c, 9c of these transformers 8, 9.10.

10c are connected in series, the detected voltages are added and applied to the electrodes of the optical voltage sensor 12. As a result, the light transmitted through the optical voltage sensor 12 is polarized, and a polarized optical signal is transmitted from the optical receiving path 3 to the optical receiver 4. The optical receiver 4 converts the optical signal into an electrical signal and outputs it to the signal processing circuit 5. The signal processing circuit 5 amplifies the input electrical signal, performs signal processing, and outputs it to the display device 6.

The above is the operating principle of zero-sequence current detection.

On the other hand, regarding the positive-sequence current, regardless of the presence or absence of the zero-sequence current, the secondary current flows through the secondary windings 3b and gb of the first transformers 8 and 9, so that the second transformer 13. 14 secondary winding circuits 13b, 14b have resistors 15. 16, a secondary current flows respectively in the tertiary windings 13c and 14c.
A tertiary voltage is generated and applied to the optical voltage sensor 17,18. The operation thereafter is similar to that of the optical voltage sensor 12. As a result, the positive sequence currents of the two phases of the power transmission and distribution lines are measured, and for the remaining one phase, as shown in Fig. 3, the vector of the measured positive sequence currents 1- and Ib of the two phases is The sum can be vectorially calculated from the measured zero-sequence current 1c at the signal processing stage.

Regarding power consumption, if the turns ratio between the secondary winding and the tertiary winding of the second transformer is increased, the resistance values of the resistors 15 and 16 can be reduced, so that power consumption can be suppressed.

On the other hand, apart from the method of the present invention, suppose that a method is adopted in which, for example, a resistor is directly connected to each of the secondary windings of the first transformer of each phase and the voltage generated across the resistor is applied to the sensor. In order to ensure the sensitivity of the sensor to the same level as the method of the present invention, a large amount of power will be consumed, and in order to compensate for this burden, the cross-sectional area of the magnetic core must be made large.

Furthermore, when a single CT for positive sequence current is installed on the primary conductor as shown in Figure 6, the primary current is larger than in the second transformer of the present invention, so the core diameter becomes larger for insulation, and the secondary Since both the secondary current and the secondary voltage increase, power consumption increases. Furthermore, if the resistance is made smaller in order to reduce power consumption, the tertiary voltage will also become smaller, which will reduce detection sensitivity, and in order to compensate for this, the turns ratio will have to be increased.There are many factors that make this difficult to implement. , it can be seen that the present invention is more useful.

In this example, the lq-shaped iron core was placed at the opening of the switch electrode of the switch, but it may also be placed around power transmission and distribution lines, and the voltage sensor is not limited to an optical voltage sensor using an electro-optic crystal. Any type of voltage sensor may be used as long as it is a human impedance voltage sensor.

〔Effect of the invention〕

As explained above, according to the present invention, positive sequence current can be measured with high sensitivity by adding a second transformer while leaving the device that detects zero-sequence current of power transmission and distribution lines with high sensitivity as is. . Furthermore, by increasing the turns ratio of the second transformer, the power consumed by the resistor can be suppressed, and the load on the entire circuit can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention, and FIG.
The figure is an explanatory diagram of the structure of an optical voltage sensor, Figure 3 is a vector diagram showing how to determine the positive sequence current, Figure 4 is a block diagram showing the configuration of a conventional optical zero-sequence current detection device, and Figure 5 is a stand-alone FIG. 6 is a block diagram showing the configuration of the CT tertiary winding system, and is an explanatory diagram showing an example of a conventional current measuring device using an optical magnetic field sensor. 1.31: Optical transmitter 2.32: Optical transmission path 3.33: Optical receiving path 4.34 + Optical receiver 5.35 + Signal processing circuit 6.36: Display device 7; Switches 7a, 7b, 7c 8.9 ,10
: First transformer 8a, 9a, 10a: M-shaped core 8b, 9b, iob: Secondary winding 8c, 9c, 10c: Tertiary winding 11, 15.16: Resistor 12, 17.18: Photovoltage Sensors 13, 14: Second transformers 13a, 14a: 1m-shaped iron cores 13b, 14b: Secondary windings 13C, 14C: Tertiary windings: Switch electrode Patent applicant Yasuyo Electric Manufacturing Co., Ltd. Manager Kobori Masu (and 2 others)

Claims (1)

[Claims] A first transformer is provided in which an annular core is arranged on each of the first and third phase power transmission and distribution lines, a secondary winding and a tertiary winding are wound around each core, and The secondary winding of the transformer No. 1 is connected in parallel to a common resistor, and the tertiary windings of each phase are connected in series, and a photovoltaic voltage is generated using an electro-optic crystal between both terminals of the series circuit. In an optical zero-sequence current detection device equipped with a sensor and means for detecting a voltage proportional to the zero-sequence current, an annular iron core is disposed in at least two phases of the secondary winding circuit, and two A second transformer having a secondary winding and a tertiary winding is provided, a resistor is connected to each secondary circuit of this second transformer, and a resistor is connected to each tertiary circuit of this second transformer. 1. An optical zero-sequence/positive-sequence current detection device, comprising means for detecting a positive-sequence current by providing optical voltage sensors between both terminals of a circuit.