JPH068837B2 - Phase detector for transmission and distribution lines - Google Patents

Description

The present invention relates to a phase detector for determining the phase of a transmission / distribution line.

[Prior art] Is the transmission / distribution line of each phase properly connected to the terminal of each phase of each electric power equipment after completing wiring work for new installation or replacement of the transmission / distribution line, or rebuilding of the tower? The conventional technique for "phase detection" to check whether or not the connection is to remove the once connected wire, sequentially energize each one end of each wire, and detect the voltage at the other end.

[Problems to be Solved by the Invention] In the conventional phase detection method, the wiring of each power device has to be removed, which is extremely complicated in terms of work. Especially in recent electric power devices, many of them have a closed structure, and it is particularly difficult to remove the wiring. Furthermore, there is a danger of electric shock because the phase is detected when the power is on. If the voltage applied to each line is lowered to eliminate the risk of electric shock, the voltage induced on the line to be inspected by induction from another line will be higher than the voltage applied for inspection, and the phase discrimination However, there are some problems such as difficulty in

[Means for Solving Problems] A phase detector for a transmission and distribution line of the present invention is provided at one end of the transmission and distribution line.
When N is a natural number, an oscillator generates a low-frequency signal whose frequency is represented by the product of a value obtained by subtracting 1 from twice the value of N and a value of half the frequency of the current transmitted by the distribution line. The low frequency signal is selectively received by the filter at the other end of the power transmission and distribution line and is displayed on the display means to detect the other end of the target phase line.

[Operation] A low-frequency signal applied to one end of one of the power transmission and distribution lines is detected at the other end by a bandpass filter so that only the signal of that frequency is separated from other signals and noise.

[Embodiment] FIG. 1 shows the configuration of an embodiment of the present invention. In the figure,
The transmitter T comprises three oscillators 1, 2 and 3 which emit low frequency signals of eg 330 Hertz, 450 Hertz and 570 Hertz respectively. The output of each oscillator is the respective amplifier 4
Is amplified by. The signal amplified by the amplifier 4 is transmitted through the respective isolation transformers 5 to the transmission lines A3, B3 and
It is adapted to be output to respective terminals A1, B1 and C1 for connecting to C3. An arrester 6 is provided on the primary side and the secondary side of each isolation transformer 5 in order to protect the amplifier 4 from high voltage due to lightning induction or the like.

The power transmission lines A3, B3, and C3 may be several kilometers in length, for example, in the case of overhead lines, or may have various electric devices interposed. An actual example is shown in FIG.
In the figure, a cubicle 22, which is an example of a device having a closed structure, is installed in the substation 21 and the transmitter T
The respective terminals A1, B1 and C1 are connected to the working ground terminals A5, B5 and C5 of the busbar of the cubicle 22, respectively. The ground terminal E is connected to the ground wire of the cubicle 22. The transmission lines A, B and C from the cubicle 22 reach the connecting portion 27 of the steel tower 24 via the underground cable 23, and from there, connect to the three overhead lines A3, B3 and C3 stretched between the steel towers 24 and 25, respectively. Has been done. In order to prevent inductive obstacles, a plurality of overhead lines change the order of phases on the way as shown in section M of FIG. Overhead lines A3, B3, and C3 in the steel tower 25 are connected to, for example, a device 26 provided outdoors in another substation. The measuring terminals A2, B2 and C2 of the receiver R are respectively connected to the respective busbars A6, B6 and C6 of its corresponding device 26. The ground terminal E of the receiver R is grounded.

As shown in FIG. 1, one terminal of the primary coil of each insulation transformer 15 is connected to each of the measuring terminals A2, B2 and C2, and the other terminal E of each primary coil is grounded. The secondary side of each isolation transformer 15 is connected to a respective change-over contact 40, 41 and 42 of a change-over switch 38 via a high-pass filter 36 for substantially short-circuiting signals below 300 Hertz. The common contact 43 of the changeover switch 38 is adapted to be commonly input to the bandpass filters 11, 12 and 13 via a variable resistor 37 for adjusting the level. The output level of each filter 11, 12 and 13 is displayed by a respective level meter 16, 17 and 18.

Next, the operation of this embodiment will be described. As shown in FIG. 2, a transmission signal of the oscillator 1 of the transmitter T, for example, at 330 Hz is amplified by the amplifier 4 and applied to the power transmission line A from the terminal A1 via the insulating transformer 5. Similarly, the oscillation output of the oscillator 2 and the oscillation output of the oscillator 3 are amplified by the respective amplifiers 4 and applied to the transmission lines B and C from the respective terminals B1 and C1 via the respective insulation transformers 5. .

The low frequency signal applied to each transmission line A, B and C passes through the underground cable 23 and the overhead lines A3, B3 and C3, and the measurement terminal A of the receiver R
Input to 2, B2, and C2. The input signals are input to the respective high-pass filters 36 via the insulating transformers 15 as shown in FIG. The signal from which the components of 300 Hertz or less have been removed by the high pass filter 36 is switched by the changeover switch 38 and applied to the band pass filters 11, 12 and 13. The filter 11 has a bandpass characteristic of 330 Hz which is the oscillation frequency of the oscillator 1 of the transmitter T, and only the 330 Hz signal is selected and the level is displayed by the level meter 16. Further, the filters 12 and 13 have bandpass characteristics of 450 hertz and 570 hertz transmitted by the oscillator 2 and the oscillator 3, respectively, and select signals of respective frequencies and display them on the level meters 17 and 18, respectively. Generally, an overhead line consists of multiple parallel lines 28 between towers 24 and 25, as shown in FIG.
Are provided, and the overhead lines A3, B3 and C3 are induced from their parallel line 28, producing an induced signal over a wide frequency spectrum range. The filters 11, 12 and 13 selectively receive the signals of the oscillators 1, 2 and 3 from their induced signals.

Now, if the level meter 16 indicates the highest level when the changeover switch 38 is switched to the contact 42, it is found that the busbar C6 is connected to the working ground terminal C5. Further, for example, when the level meter 18 indicates the highest level when switching to the contact 41, the bus bar B6 is connected to the working ground terminal A5.
Turns out to be connected to.

Fig. 3 shows the transmission voltage of 22KV, overhead line length 3.8km, underground line length 0.1k.
m shows the measured data of an actual transmission line with an extension line length of 1.0 km. In the figure, each waveform shows the frequency response of the level displayed on the level meter 18 and the level generated on the secondary side of the isolation transformer 15. Waveform 30 is level meter 18
The waveform 31 is the output waveform of the secondary side of the isolation transformer 15. The waveform 32 is generated by the guidance from the parallel line 8. The oscillation signals of the oscillators 2 and 3 have the levels shown in the waveforms 33 and 34, respectively. Oscillator 1
The level of the waveform 30 displayed by the level meter 18 indicating the reception signal of 330 Hz which is the transmission signal of is higher than the level of the waveform 31 by about 30 decibels, and therefore can be easily detected.

By selecting the respective oscillation frequencies of the oscillators 1, 2 and 3 as shown in the first equation, it is possible to reduce the influence of 60 Hz which is the frequency of the current flowing through the transmission line and its harmonics.

F = C × (2n−1) (1) where F is the transmission frequency and n is a natural number. C is a constant, which is a value that is half the transmission frequency.

Further, it is difficult to sharpen the characteristics of the halter at a frequency lower than 200 hertz, and a high frequency of 800 hertz or higher is not suitable for use in the embodiment of the present invention because the transmission line is largely attenuated during seeding.

[Effects of the Invention] According to the present invention, a transmitter is connected to one device and a receiver is connected to the other device connected to a transmission and distribution line to be subjected to phase detection, and low-frequency signals of different frequencies are generated. The transmission lines of three oscillators are connected to the respective power transmission lines, and the low frequency signals are selectively detected by the Bunt pass filter provided in the receiver, so that the power transmission lines are connected to the electric equipment or the like. Since the phase of each transmission line can be determined as it is, it is not necessary to remove the transmission line from the electric device, and the phase detection work can be performed very easily. Therefore, the phase can be easily detected even in an electric device in which the distribution line cannot be removed due to the closed structure.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a layout diagram showing a usage state of a phase detector of the present invention, and FIG. 3 shows measured values of detection levels with respect to frequencies in an embodiment of the present invention. It is a graph. A, B, C; Transmission line 1,2,3; Oscillator 11,12,13; Filter 16,17,18; Level meter

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-58-79168 (JP, A) JP-A-60-253881 (JP, A) Actual development Sho-58-186472 (JP, U)

Claims (1)

[Claims] 1. A low-frequency signal applied to one end of a transmission / distribution line, the frequency of which is a value obtained by subtracting 1 from a value twice N when N is a natural number, and a current transmitted to a power line. At least one oscillator for generating a signal represented by the product of half the frequency and a filter provided at the other end of the transmission and distribution line and having the low frequency signal as a pass band and selected. A phase detecting device for a transmission and distribution line having a display means for displaying the received signal.