JPH0475438A - Wireless telemeter system for monitoring transmission line - Google Patents

Abstract

PURPOSE:To perform carrier sense operation appropriately with no influence of corona noise even when a telemeter system is installed on a transmission line by detecting the current flowing from the transmission line to the casing of the wireless telemeter for monitoring the transmission line and then lagging the phase of thus detected charging current by 90 degree. CONSTITUTION:A charging current measuring circuit 6 measures the charging current flowing through a stray capacity existing between the casing 2 and the earth. Thus detected charging current has phase lead of 90 degree ahead a ground voltage and thereby it is fed to an integrating circuit 7 in order to lag the phase by 90 degree and further fed to a full-wave rectifying circuit 8. Output waveform from the full-wave rectifying circuit 8 is then converted through a comparator and an inverter 9 into a binary coded signal and a carrier sense circuit 10 is controlled so that carrier sense operation is executed at a zero-cross time point of the ground voltage on the transmission line 1. When no wireless signal is provided, a wireless data transmission circuit 11 transmits data of a sensor 12 on an antenna 14.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a wireless telemeter device installed on a power transmission line to monitor power transmission line parameters, particularly a device having a carrier sense circuit for preventing interference in the wireless channel. It is related to.

[Prior Art] In wireless communications, it is necessary to prevent loss of valuable data due to collision of radio waves from multiple transmitting equipment, that is, interference. Particularly in recent years, the density of radio wave use has increased dramatically with the development of social functions and the sophistication of telecommunications technology. For this reason, it has become difficult for individual radio equipment to exclusively use dedicated radio frequencies, and measures to prevent interference have become an increasingly important issue.

In the simplex wireless communication system, which communicates by alternately switching between transmitting and receiving, the device is usually put into a receiving state before transmitting, and after confirming that there are no other radio waves on the relevant radio frequency, transmitting is started. This prevents interference.

In addition, wireless telemeters that wirelessly transmit data measured at a remote point often employ a unidirectional wireless communication method in which only wireless transmission equipment is installed at the measurement point and data is transmitted unilaterally. In many cases, it is necessary to occupy a specific frequency. As a way to solve the problem of interference in this case, a receiving function is added to the transmitting equipment side, and immediately before transmission, it automatically checks for the presence of other radio waves of the same frequency and confirms that there are other radio waves. There is a so-called carrier sense interference prevention method that prevents transmission, and some devices, such as specified low power wireless equipment, are legally required to have this carrier sense function.

[Problems to be Solved by the Invention] On the other hand, various parameters (voltage, current, temperature, etc.) of high-voltage power transmission lines or distribution lines can be measured under the operating conditions of these lines, and maintenance and distribution of power transmission and distribution equipment can be carried out. Devices for monitoring purposes that can be attached directly to electrical wires have been developed. Since power transmission lines or distribution lines are always in a high voltage state, it is necessary to transmit the measured data to the ground potential so that it can be obtained by humans, and in many cases wireless transmission is used. In this case, there are a large number of radio telemeters installed, and it is not acceptable to use separate frequencies for each in view of the current congestion of radio waves, so a large number of radio telemeters will share the same frequency.

In such an environment, as a means to solve the problem of interference, a wireless telemeter is equipped with a carrier sense function as in the prior art described above. however,
Since power transmission lines are charged with high voltages, noise due to corona discharge may occur in some cases, and this corona noise makes it difficult for wireless telemeters to be installed in close proximity to the noise source. There is a problem of not being able to have a sense of career.

An object of the present invention is to provide a novel wireless telemeter device for power transmission line monitoring that can perform appropriate carrier sensing without being affected by corona noise even when installed on a power transmission line.

1. Means for Solving the Problem] The present invention includes a transmitting circuit for transmitting monitoring data of power transmission line parameters by radio waves, in a case installed on a power transmission line, and a transmission circuit of the same frequency prior to transmitting the radio waves. In a radio telemeter for power transmission line monitoring, which is equipped with a carrier sense circuit that checks the presence or absence of a radio wave and prohibits transmission from a transmitting circuit if another radio wave is received, means for recognizing the ground AC voltage waveform of a power transmission line. and carrier sense control means for detecting the recognized zero-crossing point of the ground AC voltage and allowing the carrier sense circuit to operate in the vicinity of the zero-crossing.

In this case, the means for recognizing the ground AC voltage waveform of the power transmission line specifically includes a charging current detection circuit that detects the current flowing from the power transmission line to the case of the wireless telemeter for monitoring the power transmission line, and a charging current detection waveform thereof. It can be configured with a phase shift circuit that delays the phase by 90°.

[Function] The wireless telemeter device for power transmission line monitoring of the present invention is configured to perform carrier sense near the zero-crossing point of the ground AC voltage waveform of the power transmission line. Corona noise is generated around the high voltage portion of a sine wave and disappears near the zero-crossing point, so that appropriate carrier sensing can be performed without being interfered with by corona noise.

The timing to execute carrier sense does not have to be exactly at the zero-crossing point; it can be carried out at a phase angle of 45 degrees, that is, within ±2.5 msec in a 50Hz system, and within about ±2 msec in a 60Hz system. .

To recognize the ground AC voltage waveform of a power transmission line, a current measurement means is inserted between the power transmission line and the case of the monitoring wireless telemeter.
What is necessary is to detect the charging current waveform flowing into the stray capacitance between the case of the monitoring telemeter and the ground, and correct the phase shift.

[Embodiment 1] Hereinafter, details of a carrier sense device used in a power transmission line monitoring telemeter of the present invention will be explained with reference to figures showing embodiments.

FIG. 1 is a waveform conceptual diagram illustrating the method of the carrier sense device of the present invention.

As shown in (^) in FIG. 1, the voltage to the ground of the power transmission line is a sine wave whose sign reverses from positive to negative at the commercial frequency. When extremely high voltages are applied, the electric field on the surface of the power transmission line increases, causing dielectric breakdown of the surrounding air and causing partial discharge, or corona discharge. If an unexpected protrusion forms on the surface of a power transmission line, corona discharge will occur at a lower voltage. These corona discharges generate noise containing radio frequency components.

These are RI (Radio Interferenc
e) + 'rv I (TVInterferenc)
This is a phenomenon known as e).

Looking at the details in terms of time, as shown in (B), a high voltage is generated centering on the wave height part of the sine wave, and the part that crosses Ov (
disappears at the zero-crossing point and before and after). Therefore, the intensity of the generated wireless noise has the form shown in (C). Furthermore, if another radio equipment is transmitting, a signal as shown in fD) will be present. Therefore, the radio receiving section that performs carrier sensing receives a signal strength in which noise and other radio signals are superimposed, as shown in (E). Carrier sense determines the presence or absence of other radio signals using a predetermined threshold as shown in (E).

If carrier sensing is performed at time a shown in (F), noise due to corona discharge will be detected, and the determination will be made as if another radio signal were present. Also,
If carrier sensing is performed at time b, it will not be possible to distinguish between radio signals and noise. Therefore, it is necessary to distinguish between noises by some means, and the present invention utilizes phase information of the ground voltage waveform of the power transmission line. That is,
As shown by cl, C2, C3, and C4 in (F), carrier sensing is performed at the zero-cross point of the ground voltage waveform of the power transmission line to remove the influence of noise. It can be accurately determined that there are no other wireless signals in C1°C2 and C4, and C3
can accurately determine the presence of other wireless signals.

FIG. 2 is a configuration diagram showing one embodiment of the carrier sense device of the present invention, and FIG. 3 is a schematic diagram of waveforms explaining the operation of FIG. 2.

A power transmission line monitoring wireless telemeter device 2 is installed on the power transmission line 1 . Inside the wireless telemeter case 2a,
A feedthrough transformer 3 for power supply is installed around the power transmission line,
Power for the telemeter is extracted from the current flowing through the power transmission line by electromagnetic induction. The output of this transformer 3 is stabilized and rectified by a power supply circuit 4 and supplied to each part.

A rechargeable battery 5 is attached to the power supply circuit 4, which allows operation for a certain period of time even if the current flowing through the power transmission line decreases.

Further, inside the case 2, a charging current measuring circuit 6 is connected between the power transmission line 1 and the case 2a, and measures the charging current flowing in the stray capacitance between the case 2 and the ground. As shown in Figure 3, the detected charging current waveform (■) has a phase that is 90 degrees ahead of the ground voltage waveform, so it is delayed by 90 degrees by passing it through the integrating circuit 7 as a transfer circuit, and is further subjected to full-wave rectification. By passing it through the circuit 8, a rectified output waveform (2) shown in FIG. 3 is obtained. This charge measurement circuit 6. Integral circuit 7
The full-wave rectifier circuit 8 constitutes means a for recognizing the ground AC voltage waveform of the power transmission line 1. Reference numeral b denotes a carrier sense control means that detects the recognized zero-crossing point of the ground AC voltage and allows the carrier sense circuit 10 to operate near the zero-crossing point. When this rectified output waveform (2) is converted into a binary signal by a comparator and an inverter 9, an inverter output waveform (2) is obtained.

The carrier sense circuit 10 is controlled using this output waveform (2) as a carrier sense control signal, and the carrier sense operation is executed at the time when the ground voltage of the power transmission Ill crosses zero, that is, at the time when noise due to corona discharge is not generated. The carrier sense circuit 10 is connected to the antenna 14 through the antenna switch 13, performs a carrier sense operation, and when it is confirmed that there is no other wireless signal, the wireless data transmission circuit 11 transfers the data of the sensor 12 to the antenna. 14.

Effects of the Invention As explained above, according to the carrier sense device of the present invention, even if corona noise occurs in a power transmission line where a monitoring wireless telemeter is installed, an appropriate carrier sense can be carried out. This has the remarkable effect of avoiding the loss of valuable information due to interference.

[Brief explanation of drawings]

Fig. 1 is a waveform conceptual diagram explaining the operating principle of the carrier sense of the present invention, Fig. 2 is a configuration diagram showing an embodiment of the wireless telemeter device of the present invention, and Fig. 3 is an embodiment shown in Fig. 2. FIG. 2 is a schematic diagram of waveforms explaining the operation of FIG. In the figure, 1 is a power transmission line, 2 is a wireless telemeter for monitoring power lines,
2a is a case, 3 is a feed-through transformer for power supply, 4 is a power supply circuit, 5 is a rechargeable battery 6 is a charging current detection circuit, 7 is an integration circuit (transfer circuit 1i'l), 8 is a full-wave rectifier circuit, 9 is a A comparator and an inverter, 10 is a carrier sense circuit, 11 is a wireless data transmission circuit, 12 is a power transmission line monitoring sensor, 13 is an antenna switch, 14 is a wireless transmission antenna, a is a means for recognizing the ground AC voltage waveform, and b is a carrier It is a sense control means. Patent applicant Tokyo Electric Power Co., Ltd. Hitachi Cable Co., Ltd. Agent Patent attorney Nobuo Kinutani Korob 'Rikig1t Noyce Figure 1

Claims (1)

[Claims] 1. A transmission circuit for transmitting monitoring data of power transmission line parameters by radio waves in a case installed on a power transmission line, and a transmission circuit that detects the presence or absence of other radio waves of the same frequency before transmitting the radio waves. In a wireless telemeter for power transmission line monitoring, which is equipped with a carrier sense circuit that prevents the transmission circuit from transmitting when another radio wave is received, it has been recognized as a means for recognizing the ground AC voltage waveform of a power transmission line. 1. A wireless telemeter device for monitoring power transmission lines, comprising carrier sense control means for detecting a zero-crossing point of an AC voltage to ground and allowing operation of the carrier sense circuit near the zero-crossing. 2. The means for recognizing the ground AC voltage waveform of the power transmission line,
The power transmission line monitoring system according to claim 1, comprising a charging current detection circuit for detecting the current flowing from the power transmission line to the case of the wireless telemeter for power transmission line monitoring, and a phase shift circuit that delays the charging current detection waveform by 90 degrees. wireless telemeter device.