JPS63263479A - Detector for accident position of power transmission line - Google Patents

Abstract

PURPOSE:To accurately reconvert a digital light signal into a secondary current even in spite of the deterioration of a light emitting element and transmission loss by converting the output signal of a current transformer into the digital signal and emitting the light emitting element, and transmitting the digital light signal by an optical fiber. CONSTITUTION:When a current flows through a power transmission line 1, a secondary current flows through the current transformer 2 in proportion to the primary current of the alternating current. When the secondary current is excessive, the current is adjusted by a discharging arrester 3' to a proper level and then converted by an A/D converting circuit 3'' into the digital signal. The light emitting element 4 emits with this digital signal and its output digital light emission signal is transmitted by the optical fiber 5 and reconverted into the original secondary current by a D/A converter 6.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention is a method for detecting the location of a fault in a power transmission line by measuring the current flowing through a power transmission line using an optical output type current transformer and detecting the location of a fault in the power transmission line based on the measured value. Regarding equipment.

[Conventional technology]

In recent years, as power demand increases, power transmission lines have become larger and more trunk lines, and due to social demands, power transmission routes have become limited to mountainous regions. Therefore, accidents such as ground faults and short circuits caused by lightning strikes are likely to occur, and there is concern that large-scale power outages will occur if such accidents occur.

As a means of dealing with the occurrence of such accidents, current conversion systems are installed on ground wires installed at the top of the tower at appropriate positions before and after the tower to support the power transmission line, which was previously installed in the middle of the transmission line. CT-Curre
A power transmission line fault position detection device is provided that can detect the fault position based on a signal sent from a power transmission line fault position (abbreviated as nt Transformer-).

CT2↓ above, as shown in Figure 2, the coil 2 is generally placed in the two-part core 21! It is attached in a plane perpendicular to the longitudinal direction of the power transmission line at appropriate positions before and after the support tower of the power transmission line mentioned above. The output of this CT is a discharge arrester 3' attached to the CT, a current limiting resistor 3
1 #, bidirectional Zener diode 38', switching diode 3. #, is converted into an optical signal via an output circuit consisting of a light emitting diode 4, etc., and this signal is sent to a remotely located detection circuit via an optical fiber transmission line 5, where the optical signal is converted back into an electrical signal. The accident section is then determined.

In the conventional power transmission line fault position detection device, a CT generates a secondary current having a waveform similar to the primary current (follow-on current) flowing through the power transmission line, and this secondary current is used as the output signal. Follow-up current refers to the fact that when a lightning flash occurs on a power transmission tower, etc., the current being transmitted flows along the discharge path that passes through the insulator and flows into the ground. The relay in the area will trip, causing a power outage.

[Problem that the invention seeks to solve]

In the conventional power transmission line fault location detection device described above, the secondary current causes a light emitting element such as a light emitting diode to shine directly, and the signal is transmitted to the detection circuit. The magnitude of the signal, that is, the detected current value is affected by the characteristics of the light emitting element and the transmission loss of the optical fiber. This is because the follow-on current of the secondary current is alternating current, and therefore the secondary current is generated as alternating current with a waveform, amplitude, period, etc. proportional to this, so even if it is converted into an optical signal by a light emitting diode, the optical signal is The amplitude, period, etc. of This is because even if the signals actually have the same value, the detection circuit may treat them as signals with a smaller value. For this reason, there is a possibility that the power transmission line accident position detection device does not function properly and cannot detect the accident position due to a flashover accident.

This invention was made in view of the current state of power transmission line fault location detection devices, and its purpose is to prevent the influence of transmission lines and changes in light emitting power when converting secondary current from CT into optical signals. is converted into an unrelated digital signal by using an A/D conversion circuit to convert it into an electrical signal such as a digital code string or a frequency signal of an optical pulse, which can be transmitted as a digital optical signal, and is An object of the present invention is to provide a power transmission line fault position detecting device that can accurately restore the original secondary current using a D/A conversion circuit even if there is deterioration of a light emitting element or transmission loss.

[Means for solving problems]

In this invention, as a means to solve the above problems,
A current transformer consisting of a core and a coil, an A/D converter that converts its output signal into a digital signal, a light emitting element that emits light based on this digital signal, and a light emitting element that transmits the digital optical signal from the light emitting element. A configuration was adopted that included an optical fiber transmission line connected to the

[Effect]

When a follow-on current occurs in a power transmission line due to a flash phenomenon caused by an electric shock, a secondary current proportional to the primary current of this follow-on current is generated in a current transformer. Since the secondary current is basically an analog signal consisting of an alternating current component of 50 or 60 Hz, the secondary current is also generated as a similar analog signal.

The A/D converter converts an analog secondary current signal into a digital optical signal using, for example, the following method.

The secondary current sent to the A/D converter is sampled by a sampling circuit of the converter as discrete signals at appropriate time intervals. This pulsed discrete waveform signal is
A hold circuit holds only the magnitude of the amplitude until the next sample value, a quantizer converts it into discrete time and amplitude signals, and an encoder converts these signals digitally as a signal sequence of 0 or 1. signaled.

After converting into an electrical digital signal, this signal causes the light emitting element to emit light. The digital signal from this light emitting element is simply sent as a pulsed optical signal, such as a code string of 0 or 1, via an optical fiber transmission line. Therefore, even if there is deterioration of the light emitting element or transmission loss due to the optical fiber, as long as this optical signal can be detected by the D/A conversion circuit at the transmission destination, the D/A converter will be able to convert the digital signal regardless of the size of the digital signal.
A conversion circuit can return the current to the original secondary current.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a schematic block diagram showing an embodiment of a power transmission line fault location detection device according to the present invention.

This detection device includes a current transformer 2 (hereinafter abbreviated as CT) consisting of a split core 2I and a coil 2□ installed in a plane substantially orthogonal to the power transmission line 1, and a current transformer 2 (hereinafter abbreviated as CT) that An A/D converter 3 consisting of a discharge arrester 3' for electrically converting the output of the CT and an A/D converter circuit 3'' for electrically converting the output of the CT into a digital signal, and a digital optical signal from the digital electrical signal by this converter. The light emitting device 4 includes a light emitting device 4 such as a light emitting diode, which emits light as a light emitting device, and an optical fiber transmission line 5 connected to the light emitting device for transmitting a digital optical signal from the light emitting device.

The optical signal transmitted by the optical fiber transmission line 5 is converted back into an analog signal by a remotely provided D/A conversion circuit 6, and the accident position is detected using the output thereof.

Although not shown, the A/D converter 3 also includes a current-limiting resistor, etc., and the A/D converter circuit 3'' has the necessary components to convert the input analog signal into an electrical digital signal. Of course, a sampling circuit, a hold circuit, a quantizer, and an encoder are included.

When a Vt current flows through the power transmission line 1, an analog secondary current is induced in the CT in proportion to this alternating current analog secondary current.

When the secondary current is excessive, l! 1. After the current is adjusted to an appropriate magnitude by an electric arrester 3' or the like, it is sent to the A/D conversion circuit 3#. In the A/D conversion circuit 3'', the secondary current is converted into a discrete signal at appropriate time intervals, which is held in a hold circuit, and the signal, which is discretized in both time and amplitude, is converted into a digital signal by an encoder.

The digital signal thus output as a 0 or 1 signal causes the light emitting diode of the light emitting element 4 to emit light. This light emission signal is transmitted through an optical fiber 5, and is transmitted through a D/A conversion circuit 6.
is returned to the original secondary current.

Furthermore, by detecting this secondary current, the fault location of the power transmission line can be detected.

In this case, since the discretized signal is converted into a digital signal and transmitted as an optical signal, there is a risk of deterioration of the light emitting element.
Even if there is attenuation due to the optical fiber, the amplitude of the digital signal only decreases, and when the D/A converter circuit 6 returns the signal to the original signal, the decrease in amplitude is irrelevant as long as the signal can be determined as either O or 1. The waveform of the secondary current can be restored to its original state.

〔effect〕

Since the present invention is configured as described above, the digital signal converted by the A/D converter is transmitted by the light emitting element.
It can be a digital optical signal with a code string of O or 1, so the secondary current caused by CT can be detected in the D/A conversion circuit regardless of the deterioration of light emitting elements etc. in the transmission path or transmission loss. can. Therefore, even if there is deterioration of the light emitting elements or the like in the transmission path or transmission loss, the accident location can be accurately determined.

[Brief explanation of the drawing]

FIG. 1 is an overall schematic block diagram of an embodiment of a power transmission line fault location detection device according to the present invention, and FIG. 2 is a block diagram of a conventional power transmission line fault location detection device. 2... Current transformer, 3... A/D converter, 4... Light emitting element.

Claims (2)

[Claims] (1) A current transformer consisting of a core and a coil, an A/D converter that converts its output signal into a digital signal, a light emitting element that emits light based on this digital signal, and a digital optical signal transmitted by the light emitting element. An optical fiber transmission line connected to a light emitting element. (2) The power transmission line fault position detection device according to claim 1, wherein a light emitting diode is used as the light emitting element.