WO2008130184A1

WO2008130184A1 - Apparatus and method for patrolling medium voltage power distribution line and pin-pointing the degraded component before its failure

Info

Publication number: WO2008130184A1
Application number: PCT/KR2008/002293
Authority: WO
Inventors: Hyun Chang Lee
Original assignee: Hyun Chang Lee
Priority date: 2007-04-23
Filing date: 2008-04-23
Publication date: 2008-10-30
Also published as: KR100795190B1

Abstract

Disclosed is a system for patrolling the distribution lines to monitor and manage the operating condition of power system networks run by power utility and railway companies on the ground without climbing the poles (structures). By using patrolling system equipped with RF noise signal analyzinga functions and GPS function to locate the faulty components with the geographic information. The present invention system can provide the trend data of each network ' s compoent againg data to accurate time line to replace before its failure by ground patrolling without live line works close to the hazardous charged volatge.

Description

[DESCRIPTION]

[invention Title]

APPARATUS AND METHOD FOR PATROLLING MEDIUM VOLTAGE POWER DISTRIBUTION LINE AND PIN-POINTING THE DEGRADED COMPONENT BEFORE ITS FAILURE

[Technical Field]

The present invention relates to patrolling system of power distribution lines during operation to locate the degraded component by detecting the radio frequency power line noise signal. More particularly, the present invention relates to a system and a method for patrolling overhead power distribution lines and detecting the early stage of insulation faulty component and loosen hardwares, wherein the operating condition of equipment can be accurately located on the ground without climbing poles while in service.

[Background Art]

The current methodologies adopted by power companies to detect the faulty components are patrol along the power lines to perform the visual inspection using binocular or infrared camera on the ground, and live line inspection on the poles whilst the circuits remains energised.

More particularly, line crews patrol overhead power distribution lines on foot or by vehicle, to ensure the line clearance from trees and structures around, and to find components which are broken or loosen by visual inspection.

Such patrols are also planned and conducted according to seasonal and environmental changes in the following manner: in spring, patrols are focused on preventing power interruption due to contact with birds and trees; and in summer, the operating condition of devices are checked in connection with the increased demand of air conditioning power and the rising atmospheric temperature . The conventional method for patrolling and checking power distribution lines will now be described with reference to the accompanying drawings .

FIG. 1 is a photograph showing operators climbing and checking respective power poles on the spot while electricity flows through the lines according to the prior art, and FIG. 2 is a photograph showing the result of checking thermal images according to the prior art.

In general, power distribution line patrols conducted by power companies include a safety patrol, a regular patrol, a special patrol, and a executive patrol. The patrol cycle is no longer than 15 days, as shown in FIG. 1, and operators patrol and check power distribution lines on foot or by vehicle. [Table l]

Conventionally, line crews have climbed power poles and checked components on the pole while no electricity flows through the lines for safety reasons. However, recent development of technology has enabled line crews to conduct the same checkup while electricity flows through the lines, as shown in FIG. 1.

During pole-climbing checkups, line crews inspect closely all the components on the pole which can not be seen on the ground. The checking targets and details are given in the following Table 2. [Table 2]

In the case of the thermal image checkup, the line crews capture infrared ray signals, which are caused by comparatively higher temperature due to high contact resistances, and overloaded operation, etc., by using an IR camera on the ground.

Particularly, line crews detect the stronger infrared signals from the overloaded transformer shown in Fig.2. This is the latest method the fact that the amount of heat generated by power equipment is proportional to the electric current and resistance values:

Q= i* i * R (Q_: amount of generated heat; I: current, R: resistance) In addition, power outageresulting from degraded components correspond occupy about 30% of the entire power distribution line failure. Such degradation of components cannot be detected by visual inspection on the ground, who patrol on foot or by vehicle, but can only be spotted when operators climb poles and inspect them closely.

The thermal inspection is effective where high current, more than several hundreds amperes, flows to generate Joule heating such as low voltage cable joint and transformer itself, but cannot detect the degradation of components on the medium voltage distribution network.

The corona discharge (partial discharge) current on the medium voltage network resulting from degraded insulation rarely generates heat, because a very small amount of current (a number of microamperes) flows instantaneously. The current flowing in the medium volatge is 1/57.5 amperes of low volatge network) and generates much lesser heat . Furthermore, all connectors in the medium volatge network are hidden by insulating covers, and thermal image cameras can hardly detect emitted IR signals from high temperature joint. Particularly, covered conductors in the medium voltage network are easily burnt down when their mechanical strength is decreased by corrosion of the conductor by persisting partial discharge between the lines and supporters due to poor insulation. There is no method of detecting the early stage of cracks inside insulators, loosen bolts and nuts, etc while patrolling on the ground.

Therefore, power companies rely on the conventional live line inspection on top of the electric pole without discrimination, and it requires a huge budget to conduct this method with regard to the entire power distribution lines and dangerous work close to medium volatge live line.

A method for locating RF (radio frequency) interferenceon on the ground, instead of climbing and checking individual poles while electricity flows through the lines, is disclosed in U.S.

Patent No. 5,657,244 (issued August 12, 1997) in the name of

Radar Engineers, as well as in the user manual of Model #242 AM-

UHF RFI Locator of the same company. According to the disclosure, although the RF noise frequencies from power distribution line are not known, but monitor the single fixed frequency or manually change the frequencies time to time to detect the power line noise.

More particularly, a technician with high-level skill enough to analyze waveforms and characteristic of power line noises should patrol the lines with gears. If a RF noise signal is detected during monitoring, the technician switches to another frequency to confirm that the electric pole has faulty components becasue the detected radio signals are emitted from distribution power line as wideband noise with characteristic of power system frequency such as 50, 60 Hz.

In prior art, the skilled technician who knows the waveform interpretation should peform the patrol and poor poles may be left unnoticed if the frequency does not match to the single monitored frequency, and it is difficult to manage the data regarding the level of RF noise signals for respective places where poles are located with time tag.

[Disclosure] [Technical Problem]

Therefore, the present invention has been made in view of the above-mentioned problems, and the present invention provides a system and a method for patrolling overhead power distribution lines and detecting poor equipment, wherein the operating condition of equipment can be accurately judged on the ground without climbing poles while electricity flows through the lines. The present invention also provides a method for patrolling power distribution lines of a power company by using an RF interference analysis device adapted to detect poor components of the lines and periodically managing and analyzing interference signals with regard to respective poles so that malfunctioning equipment is detected and repaired efficiently and economically.

[Technical Solution]

In accordance with an aspect of the present invention, there is provided a system for patrolling overhead power distribution lines to locate the electric power pole where the poor components are installed by analyzing RF noise signal; the system includes multiple RF scanning receivers continuously scan in different frequency spectrums whether amplitude modulated type radio frquency signal is exist and notify the frequncy data to the RF monitoring receivers; an analyzer and alarm generation system which is comprised of multi RF monitoring receivers tuned to informed RF frequncies by above RF scanning receivers and a processor demodulating the RF signal to Audio signal to compare the signal level between the 60Hz (power frequency) filtered audio signal and RF signal to determine the power line noise and alarm severity class; displays tracking record with measured valau and alarm data over the mapping data.

The system is mounted on a vehicle or hand-carrying so that operating conditions of components installed on the poles are monitored on the ground without climbing the poles while electricity flows through the lines, and the system receives and analyzes RF signals on the move.

The system further includes a GPS receiver to synchronize the location information to the mapping data downloaded from power companies' asset management system to display measured data such as signal level, time and driving speed with direction and history data such as tracking and alarmed location. Furthermore the system sets the optimal patrol route plan by entering the work location data and guides the travel path to the line crew members .

In accordance with another aspect of the present invention, there is provided a system for patrolling overhead power distribution lines and detecting poor power distribution components by being mounted on a patrol vehicle, the system including a receiving antenna for receiving radio frequency signals emitted from power distribution line components; multiple RF scanning receivers continuously scan in different frequency spectrums whether amplitude modulated type radio frequency signal is exist and notify the frequency data to the RF Monitoring receivers; an analyzer and alarm generation system which is comprised of multi RF monitoring receivers tuned to informed RF frequncies by above RF scanning receivers and a processor demodulating the RF signal to Audio signal to compare the signal level between the 60Hz (power frequency) filtered audio signal and RF signal to determine the power line noise and severity class,-A GPS Receiver to synchronize the location information to the mapping data downloaded from power companies' asset management system to display measured data such as signal level, time and driving speed with direction and history data such as tracking and alarmed location. Furthermore the system sets the optimal patrol route plan by entering the work location data and guides the travel path to the line crew members.

Each of multiple RF scanning receivers is assigned frequency spectrum range they should scan AM noise signal which are not occupied any RF signal from 10MHz to 600MHz at the patrollling region to capture the small signal emitted from power lines prior to power distribution line patrolling. Normal detecting threshold level of AM type RF signal level is more than -9OdBm.

Each RF monitoring receiver tuned to informed RF frequncy where RF scanning receiver detected AM noise signal and filtered demodulated audio signal with power frequency (50, 60Hz) blocking filter to be compared RF signal and filtered audio signal level. The difference between the two signals will become the main factor to determine its severity level of alarm. In accordance with another aspect of the present invention, there is provided a method for patrolling overhead power distribution lines and detecting poor power distribution components by analyzing RF interference signal, the method including the steps of scanning multiple frequencies to find the AM noise signal frequency where normally non occupied) for RF interference analysis; continuously monitoring the frequencies detected by scanning receivers to determine whether power line noise and alarm level by comparing RF AM noise and power frequency filtered AF signal level; and displying the alarm level over the mapping data based on the result of comparison and generating an alarm according to the result of RF interference analysis. The steps are conducted while a patrol vehicle equipped with a corresponding system is on the move. The step of scanning; multiple frequencies where normally noise free bandwidth to detect the RF AM noise greater than thereshold level and notifying the frequency information to the RF monitoring receivers to determin the power-line noise and its severity level;monitoring the frequency informed by scanning receiver continuously to determine whetehr true power line noise or not; If informed frequency seemed true power line noise then register the frequency data to be monitored continuoulsly or false signal without power system frequency then register frequency to be skipped in scanning; In the step of scanning, radio frequency interference signals, non occupied multiple frequency bandwidths are scanned from 10MHz to 600MHz to detect the AM type signals, and RF signal at the specific frequency greater than - 9OdBm is added to a monitoring target frequecy list to be informed to monitoring receiver -9OdBm being set as a threshold value for detecting RF interference signals.

The step of tuned to monitoring target frequency to determine that detected RF frequency is power line noise by comparing the RF noise and AF filterd power system frequency signal level. If the level difference between the two signals is exist more than threshold level then true power line noise but less than threshold level then false; If false power line noise then register the RF frequency to be skipped; and measuring an RF field strength level value for each frequency and recording the value together with time and location information.

The step of comparing the field strength of the RF interference with the audio signal includes the steps of determining if 60Hz power system, comparing the RF field strength value with a level value of the audio signal after the audio signal having passed through the 60Hz blocking filter.

The step of comparing the field strength of the RF interference with the audio signal includes the steps of determining if 50Hz power system; comparing the RF field strength value with a level value of the audio signal after the audio signal having passed through the 50Hz blocking filter.

The step of displaying an RF interference grade and generating an alarm includes the steps of determining a power interference grade included in an RF signal for each section; comparing the determined interference grade with a previous level; displaying an identical interference grade in the case of an identical level and displaying a new interference grade in the case of a different level; determining if the interference grade is equal to or higher than a setup level; and determining an alarm level based on the interference grade when the interference grade is equal to or higher than the setup level and outputting different kinds of alarms according to the interference grade.

After RF interference analysis is completed, obtained information is displayed on a map on a screen of an analyzing and recording device differently according to respective degrees of danger.

[Advantageous Effects]

The system and method for patrolling overhead power distribution lines and detecting poor equipment according to the present invention have the following advantages. Firstly, it is possible to prevent power failure resulting from poor components (e.g. insulator, switchgear, joint, lightning arrestor etc) , which occupy 30% of entire power distribution line failure and which cannot be detected by conventional visual inspection including thermal inspection on the ground. Therefore, power outage resulting from poor components can be reduced substantially.

Secondly, the present invention makes it unnecessary to climb and check all the poles to detect the faulty components while electricity flows through the lines because the present invention can pinpoint the poles with faulty components for power companies to reduce the cost of maintenance and increase the productivities .

The present invention reduces the budget and accident related to aerial works close to medium volatge lines. Thirdly, the live line inspection is done just one time in a spot (i.e. not continuously) according to the prior art, but the present invention makes it possible to easily manage, record, and compare periodic measurement values by using a vehicle. Such continuous monitoring of equipment in connection with its aging guarantees reliable equipment management.

Fourthly, even if line crews patrolling power distribution lines have no professional knowledge regarding RF waves and high voltages, they can easily detect faulty components on the spot. For example, an operator can mount the inventive system on a normal vehicle and monitor the condition of power distribution lines concurrently with another job, even without a dedicated patrol operator. This reduces line crew manpower and improves working efficiency.

[Description of Drawings]

The foregoing and other objects, features and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings in which:

FIG. 1 is a photograph showing operators climbing and checking respective poles on the spot while electricity flows through the lines according to the prior art; FIG. 2 is a photograph showing the result of thermal image checkup according to the prior art;

FIG. 3 illustrates electric power distribution line patrol method using the system according to the present invention;

FIG. 4 shows system configuration drwaing based on the present invention;

FIG. 5 shows RF scanning receiver; FIG. 6 shows RF monitoring receiver;

FIG. 7 Audio frequency waveform before power system frequency filetered; FIG. 8 Broken suspension insulator due to degraded insulation ;

FIG. 9 shows RF spectrum lkm distanced from electric pole in FIG.8; FIG. 10 shows RF spectrum 6 spans away from electric pole in FIG. 8;

FIG. 11 shows RF spectrum just under the electric pole in FIG. 8; FIG. 12 shows RF spectrum 1 span away from the electric pole in FIG. 8;

FIG. 13 shows another RF spectrum at differenct location 15km away from FIG. 14 noise source;

FIG. 14 shows frequency spectrum where faulty lightning arrestor on the pole;

FIG. 15 shows audio output signal after filered for 3 different frequencies;

FIG. 16 shows log data for RF signal strength level with time and location data; FIG. 17 shows flowchart of frequency scanning and some of frequency monitoring procedure;

FIG. 18 shows flowchart of determining the alarm level procedure;

FIG. 19 shows detail flowchart of grading the alarm level (1); FIG. 20 shows detail flowchart of grading the alarm level (2);

FIG. 21 is the graph shows relationship between frequency and distance;

FIG. 22 shows example user interface screen displaying the mapping data and RF signal strength; FIG. 23 shows screen to find the un-occupied frequency spectrum before patrolling; and

FIG. 24 shows RG signal (bottom) and power system frequency (above) to compare between the two signals. [Best Mode]

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings. [Mode for Invention]

FIG. 3 illustrates the power distribution line using the syste, according to the present invention. FIGs. 4-6 show the construction of a system for patrolling lines and detecting poor equipment according to the present invention. FIG. 7 shows a waveform, prior to filtering, of an audio frequency signal resulting from poor insulation of power distribution equipment.

The present invention includes an RF noise signal collection and analyzation to detect the power line noise from the faulty components in the power distribution lines networks all over the nation, guiding the operator to the selected power distribution lines by vehicle, monitoring RF noise signal of an unknown frequency emitted from poor equipment by using the vehicle, and comparing the level of an RF interference signal of a monitored frequency with that of an audio signal that has been demodulated and passed through power system filters (60Hz or 50Hz blocking filter) to determine the RF interference grade for respective places where poles are installed. The device generates an audible alarm signal at a place having poor equipment so that the line crews recognize it.

The grade of alarm level can be dispalyed over the mapping data by different color based on 4 differenct colors as First alarm grade, Second alarm grade, Third alarm grade and Caution level.

Depending on the speed of the patrolling vehicle and the density of installed electric poles, the RF scanning and monitoring receivers may varying numbers of radio receivers.

But the illustaration in this Mode of Invention uses only two receivers, the one of which is used to scan the frequencies out of occupied bandwidth from 10MHz to 600MHz to detect the any amplitude modulation-type radio frequency noise signal exists among RF signals received from the antenna.

The other radio receiver is used to continuously monitor monitoring target frequencies, compare the level of an RF signal with that of an audio signal without power system frequency, and generate an alarm at a place with potential danger. Such radio receivers are used to continuously measure RF noise signals for respective power distribution poles, and compare and manage the measurements at each time.

Referring to FIG. 3, overhead power distribution equipment is patrolled according to the present invention in the following manner: the operator moves along a power distribution line 14, which supplies power from a power distribution substation 13, by using a power distribution line patrol vehicle 11 equipped with a present invention system, which has a device for collecting RF noise signal to analyze and detect the RF noise signal from the poor components on a power pole device 12 and a GPS for receiving signals from GPS satellites 15 so as to record both the location of patrolling and measurement time. Therefore, according to the present invention, the line crews can go over the operating condition and detect the faulty components on the ground without climbing poles while electricity flows through the lines. The detailed construction of the system for patrolling overhead power distribution lines and detecting poor equipment according to the present invention, which is mounted on a patrol vehicle, are shown in FIGs. 4-6.

FIG. 4 shows the overall construction of the system for patrolling overhead power distribution lines and detecting poor equipment according to the present invention. FIG. 5 shows the detailed construction of a receiver for scanning RF interference frequencies. FIG. 6 shows the detailed construction of a receiver for comparing and grading interference signals. If a very small current flows due to poor insulation, poor connection, bolt unfastening, etc. of power distribution line equipment, a magnetic field is created between two gaps. As a result, RF signals are generated partial breakdown of insulation, and propagated through the power lines or radiated into free space.

This RF signals travel several spans occupying the entire bandwidth ranging from the LF (Low Frequency) band to the UHF (Ultra-High Frequency) band. The level and type of created frequencies and waveforms vary depending on the atmospheric environments (temperature, humidity) , line voltage, etc.

Therefore, it is difficult to find RF power line noises reside on unknown frequency spectrum. However, according to the present invention, not only skilled maintenance operators, but also line crew can regularly patrol the lines, accumulate data, and manage and analyze the data so that any serious line malfunction can be predictive and preventive.

FIG. 4 shows the overall construction of a system 20 for patrolling overhead power distribution lines and detecting poor components according to the present invention. The system 20 includes a receiving antenna 21 for receiving radio frequencies emitted from power distribution components; an RF noise scanning receiver 22 for continuously scanning if there exists an amplitude modulation-type radio noise signal frequency among the scanned RF signals and put newly found frequencies to the monitoring target frequency list; an RF noise signal comparing and grading receiver 25 for continuously monitoring the each of monitoring target frequencies, comparing the level of an RF signal with that of an audio signal without power system frequency signal, grading them, and generating an alarm at a place of potential danger; a GPS navigation device (i.e. GPS receiver) 24 for receiving position information and matching the geographic information downloaded from utilities ' distribution asset management system prior to patrolling the power distribution lines, determining the patrol path, guiding the vehicle along the path, recording the measurement time for each equipment, the velocity of the patrolling vehicle, and the direction of movement, and displaying the information; and an analyzing and recording device 23 equipped with a program for displaying information obtained by means of the receivers on a topographical map and determining the degree of danger for each grade so that the result of detection is analyzed and recorded. Referring to FIG. 5, the RF noise scanning receiver 22 includes an RF signal amplifier 31, an intermediate frequency converter (mixer) 32 for downconverting the frequency of received RF signals, an amplitude modulation detector and band pass filter 33, an second intermediate frequency amplifier 34, a demodulator 35, an audio frequency amplifier 36, an audio frequency output device (speaker) 37, and a local oscillator 39. The RF noise scanning receiver 22 continuously scans if there exists an amplitude modulation-type radio interference frequency among the received RF signals and add the newly found frequencies into the monitoring target list.

Referring to FIG. 6, the RF monitoring receiver 25 includes an RF signal amplifier 31, an intermediate frequency converter (mixer) 32 for downconverting the frequency of received RF signals, an amplitude modulation detector and band pass filter 33, a second intermediate frequency amplifier 34, a demodulator 35, an audio frequency amplifier 36, an audio frequency output device (speaker) 37, a RF and AF signal comparator 38 for detecting RF noise from power distribution lines, and a local oscillator 39. The RF monitoring receiver 25 continuously monitors the monitoring target frequencies, compares the level of an RF signal and that of an audio signal, from which an interference signal of a power system frequency signal has been removed, grades them, and generates an alarm at a place of potential danger.

The system 20 for patrolling power distribution lines and detecting poor equipment according to the present invention includes an analyzing and recording device 23 and a GPS receiver 24 for receiving information regarding the position of power distribution lines to be patrolled following geological information to provide the optimized patrol path, and guiding the line crews along the optimized patrol path so that he/she can establish a vehicle navigation plan and drive it accordingly. RF noise signals are fed via a nondirectional active whip antenna installed on the roof top of the vehicle, i.e. receiving antenna 21, and pass through the RF amplifier 31, which amplifies the signals to measure very small values. The analyzing and recording device 23 changes the local oscillator frequency 39 to supply the intermediate frequency converter 32 with frequencies varying in the range of 10-600MHz at a predetermined interval so that the amplitude modulation detector and band pass filter 33 can detect RF interference signals greater than threshold level -9OdBm.

Upon detecting a corresponding signal, the amplitude modulation detector and band pass filter 33 instantly informs the analyzing and recording device 23 of the detection and, if the detected signal is not one of registered frequencies, registers it as a monitoring target frequency.

Although the same function is shared between the RF noise scanning receiver 22 for scanning if there exists an amplitude modulation-type radio interference frequency among RF signals received from the antenna and including frequencies into the monitoring target list and the RF monitoring receiver 25 for continuously monitoring the monitoring target frequencies enumerated in the monitoring target list, comparing the level of an RF signal with that of an audio signal without power system frequency (60Hz or 50Hz) at the comparator 38, grading them, and generating an alarm at a place of potential danger.

As is clear from the exemplary RF interference signal emitted from poor compoents shown in FIG. 7, RF interference signals created from power lines are mostly impulsive signals resulting from a very instantaneous flow of electric current, the duration of which is less than 0.01 cycle (167 microseconds).

The analyzing and recording device 23 compares the output value of the audio signal processed in this manner with the level of an inputted RF interference signal and analyzes and evaluates them at 38. If the corresponding place requires immediate measures on the spot, an alarm is generated. In the case of minor problems, an alarm of the corresponding grade is generated for persistent management. The analyzing and recording device 23, which is equipped with a program for recognizing the degree of danger for each grade to analyze and record the result of detection, records and analyzes the information obtained from the GPS receiver 24 on the spot (i.e. the patrol path of the patrol vehicle and measurement time, the position of equipment to be measured and the measurement time, the velocity of the patrolling vehicle, the direction of movement) , as well as information obtained from the RF interference monitoring receiver 25 and the RF monitoring receiver 22. The information is then displayed on a topographical map.

Preferably, the system 20 for patrolling power distribution lines and detecting poor equipment is mounted on a patrol vehicle and is connected to the DC 12V cigar jack of the vehicle so that it is operated with no separate power.

Setup frequencies and audio signals in the system for patrolling overhead power distribution lines and detecting poor components according to the present invention, which has been described above, will now be described in detail.

When the RF interference scanning receiver 22 shown in FIG. 4, detects an RF interference signal emitted from poor power distribution components, the receiver 22 informs the analyzing and recording device 23 of the detection and registers it as a new monitoring target frequency. The RF monitoring receiver 25 tunes into the newly registered frequency and confirms if the demodulated audio signal has power interference having partial discharge characteristics. If the signal has audio signal characteristics shown in FIG. 7, it is regarded as a setup frequency.

In other words, if a new RF interference signal is detected, and if the demodulated audio output of the frequency has power frequency interference characteristics, it is defined as a setup frequency so that it is continuously monitored and its relationship with other frequency band signals is compared.

As used herein, an audio signal refers to a signal obtained by demodulating an RF signal of a setup frequency into an intermediate frequency signal and converting it into a final audio band signal. In other words, an audio signal refers to a signal that has passed through the audio frequency amplifier 36 shown in FIGs. 5 and 6. and compare the RF and AF signal level at the comparator 38 to determine the true power line noises. The result of mounting the system for patrolling power distribution lines and detecting poor equipment according to the present invention onto a patrol vehicle and measuring RF interference signals resulting from power distribution lines will now be described.

FIG. 8 is a photograph showing a suspended insulator device having poor insulation. FIGs. 9-12 show RF spectrums measured with reference to the power distribution pole shown in FIG. 8. FIGs. 13-16 show RF spectrums measured with reference to a power distribution pole having a problem and a screen showing a record of power distribution line patrols.

RF interference is measured from a power distribution pole having three suspended insulators, two of which have lost lateral wings and cannot maintain insulation, as shown in FIG. 8. The result is shown in FIGs. 9-12.

FIG. 9 shows an RF spectrum measured at a distance of lkm from a power pole having a problem, and FIG. 10 shows frequency occupation bands measured at a distance of six spans.

As used herein, a span refers to the horizontal distance between supporters of overhead power transmission/distribution lines.

FIG. 11 shows a waveform measured from a power pole having a problem, and FIG. 12 shows frequency occupation bands measured from a power pole lying at a distance of one span. It is clear from the drawings that frequency bands undergoing the most frequent change are 100-200MHz and 400-600MHz. In summary, the RF interference frequencies resulting from power poles appear throughout the entire band. FIG. 13 shows an amplitude modulation-type RF signal spectrum measured between the 10-1000MHz bandwidth at a distance of at least 15km from a power pole having a problem, prior to starting the power distribution line patrol to identify the environmental noise spectrum to choose the noise free spectrum band to set the scanning frequencies for RF scanning receivers.

FIG. 14 shows an amplitude modulation RF signal spectrum measured in the same range of frequency bands from a power pole having a poor lightning arrester. FIG. 15 shows waveforms resulting from continuous recording of the audio level when the vehicle equipped with the RF interference analyzing device moves past power poles having poor lightning arresters.

It is clear from the drawing that the audio level has dropped to an almost zero level in the case of power poles that the vehicle has moved past in the time period of 08:35:30-08:36:15, as marked with red circles in the drawing.

However, FIG. 16 confirms that the RF interference signal does not fluctuate in the same period. As mentioned above, the system for patrolling overhead power distribution lines and detecting poor equipment according to the present invention guides the patroller to power distribution lines to be checked, recognizes the frequency of amplitude modulation-type RF interference signals of at least a threshold level (-9OdBm) resulting from power distribution poles during driving, and compares the level of the received RF signal of the recognized frequency with that of an audio signal that has passed through the power interference filter. A method for patrolling overhead power distribution lines and detecting poor components by using the system for patrolling overhead power distribution lines and detecting poor components according to the present invention will now be described in detail.

FIGs. 17-20 show a flowchart of a method for patrolling overhead power distribution lines and detecting poor components according to the present invention. FIG. 21 is a diagram showing the relationship between RF interference frequencies and the distance of arrival.

FIG, 22 shows a screen shot of user interface to display the information obtained on the spot by using a system for patrolling overhead power distribution lines and detecting poor components according to the present invention. FIG. 23 shows a screen dispalying the un-occupied frequency spectrums to set the scanning frequency bandwidth to detect the RF noises in a region to be patrolled, prior to patrolling power distribution lines, to determine frequencies to be scanned. FIG. 24 shows a screen configuration for recognizing power interference in a 60Hz power system, removing it, and making a comparison.

The method for patrolling overhead power distribution lines and detecting poor equipment according to the present invention includes a frequency scanning step for analyzing RF interference, a power frequency interference processing step for analyzing RF interference, a step of comparing the RF interference field strength with an audio signal after interference processing, a RF interference grade display step, and an alarm processing step based on the result of RF interference analysis.

The step of continuously monitoring frequencies to be monitored, comparing the size of an RF signal with that of an audio signal, from which an interference signal of a setup frequency has been removed, and grading them will now be described.

Poorly insulated objects installed on power distribution lines emit RF interference signals, including audio signals synchronized with power frequency (60Hz or 50Hz) as shown in FIG.

7, throughout the entire band frequencies as shown in FIGs. 10 and 11.

Therefore, as shown in FIGs. 9 and 13, the broadcasting and radio station frequencies in the region to be patrolled are recognized first, and normal radio frequencies are registered as scan-exempt objects so that the measurement time is shortened.

Then, a clean frequency band free of interference signals, which are not scan-exempt frequencies, is selected and continuously monitored. If a signal of a threshold value (-9OdBm) or larger is detected, the corresponding frequency information is sent to the RF monitoring receiver so that the frequency is fixed as the monitoring reference.

The RF monitoring receiver analyzes an audio signal received with regard to a newly registered monitoring target frequency and, if it is determined that the signal is interference resulting poor power distribution equipment, designates the frequency as a setup frequency for following comparison and evaluation. If it is determined that the frequency is not interference resulting from poor power distribution equipment, the frequency is registered as a scan-exempt object.

Then, the RF monitoring receiver measures the RF field strength level, including GPS signals, as shown in FIG. 16, and the level of audio signals that have passed through the power frequency filter as shown in FIG. 15, and compares them.

Particularly, when a setup frequency is newly registered, the

RF monitoring receiver compares already registered other setup frequencies with the audio output signal and grades it. This step is divided into an interference signal comparing step and an interference grading step.

In the interference signal comparing step, after tuning in the newly registered setup frequency, an audio signal (RF field strength value) before filter insertion is compared/measured with an audio signal value that has been filtered after insertion, and the difference between both audio signal levels is recorded in the memory. Then, after tuning in another registered setup frequency, the audio output levels before and after filter insertion are similarly compared/measured and recorded in the memory.

In the interference grading step, a signal frequency having the largest difference value is recognized among data stored in the memory after the interference signal comparison, and it is confirmed if there is a setup frequency higher than the frequency of the signal.

Based on the fact that the higher the frequency is, the shorter the distance of arrival becomes, as shown in FIG. 21, grading is conducted by using the correlation between the highest frequency among setup frequencies and the frequency having the largest difference value, as shown in FIGs. 17 and 20. After the grading, an alarm defined at the corresponding level is generated and recorded. Particularly, the RF interference monitoring receiver 22 and the RF monitoring receiver 25 are connected to the RF interference signal receiver antenna 21, and the RF interference monitoring receiver 22 is used to continuously scan to detect an amplitude modulation-type RF interference signal in the 10-600MHz band (SIlOl) .

Frequencies having RF interference signals equal to higher than the reference value set in the scanning step are recorded (S1102) .

The reference value is preferably set to be -9OdBm. The setup value of -9OdBm corresponds to the threshold value to detect RF interference signals by the system for patrolling power distribution lines and detecting poor equipment according to the present invention, and can be varied as desired by those skilled in the art. It is determined if the registered frequency is an already registered one (S1103) , and, if not, the frequency is regarded and registered as a monitoring target frequency (S1104) .

Such recording of frequencies having radio interference signals equal to or higher than the reference value set in the scanning step is for the purpose of utilizing the information, which has been obtained in the current patrol process, at a later patrol step. While the RF interference monitoring receiver 25 is used to scan radio RF interference signals and register monitoring target frequencies, the RF monitoring receiver 22 is used to continuously tune frequencies enumerated in the monitoring target frequency list (S1105) .

Then, the RF field strength level value is measured for each frequency and is recorded together with time and position information (S1106) .

The analyzing and recording device 23 obtains information regarding the position, time, and velocity of the moving vehicle from the GPS receiver 24, and stores the information together with the RF field strength level value for each frequency, which has been measured by the RF monitoring receiver 22.

It is determined if power interference is included (S1107), and, if so, interference is removed from the corresponding RF signal by passing it through the demodulator and the power interference filter (S1108) .

After removal of interference and storage of the RF field strength level value for each frequency in this manner, the analyzing and recording device 23 compares the RF field strength value with the level value of an audio signal that has passed through the power interference filter (S1109) , and determines the grade of the power interference included in the RF signal (SlIlO) . It is to be noted that any failure of lines of power distribution equipment results from a breakdown phenomenon, and partial discharge occurs locally inside or outside a fragile portion of the insulation material before such a phenomenon occurs.

The present invention is based on this finding. Particularly, a very small amount of energy is charged/discharged before the highest ascending point and the lowest descending point of each cycle of the power voltage, as shown in FIG. 7, and, as a result of the charging/discharging for a very short period of time, interference energy of an RF signal is discharged.

Such a frequency resonates with frequencies of tens or hundreds of MHz, as shown in FIGs. 10-16, and is emitted into free space or propagates along the power while emitting energy.

As the insulation degradation proceeds, the amount of emitted energy increases, and the occupied frequency band widens.

This means that, even in the case of an interference signal resonating with a frequency of hundreds of MHz, its demodulation together with a normal receiver provides an audio signal synchronized with the power frequency. By comparing and analyzing this, it is possible to easily detect and evaluate interference resulting from poor equipment installed on power distribution lines in free space.

The power interference grade included in the RF signal is determined by dividing the difference for each step (1OdB, 2OdB, 3OdB, 4OdB, audio signal=0) .

The interference grade determined in this manner is compared with the previous level (Sllll) , and, in the case of the same level, the same interference grade is displayed (S1112) . In the case of a different level, a new interference grade is displayed

(S1113) . It is confirmed if the entire frequencies to be monitored in the corresponding region have been measured (S1114), and, if so, the alarm level corresponding to the interference grade is determined (S1115) . However, if the frequency resulting from the power line is high, as shown in FIG. 21, the distance of arrival (measurable distance) becomes shorter. Therefore, it must be checked first if the grade of the highest frequency among monitoring target frequencies is the highest one (S1116) . If the highest frequency and another lower frequency belong to the same grade (S1117) , and if the adjacent power pole corresponds to at least third alarm grade (S1118) , it can be said that the power distribution equipment have already degraded to a considerable extent. Therefore, this case is designated as the top priority target and is processed based on four alarm level classification (S1119) .

If the highest frequency belongs to the highest grade, but if other frequencies do not belong to lower grades, it can be said that poor equipment may exist nearby. Therefore, the alarm level is set to be lower than the previous case by one, and the alarm is processed based on three step classification (S1120) .

If the highest frequency does not belong to the highest grade (S1121) while the periphery corresponds to at least third grade, and if input RF interference has been observed in a low monitoring target frequency band while no audio signal has been detected, it is regarded that the power distribution equipment may malfunction. This case is processed based on three step classification (S1123) . If no audio signal has been found even in low frequencies, this is regarded as a problem of little importance, and the first step alarm is applied (S1121, 1122, 1123, S1124, S1125) .

The result of measuring interference signals through the steps of patrolling overhead power distribution lines and detecting poor equipment according to the present invention is displayed on a map, as shown in FIG. 22, and is displayed on the screen of the analyzing and recording device 23 differently according to each degree of danger. As mentioned above, the system and method for patrolling overhead power distribution lines and detecting poor equipment according to the present invention are advantageous in that, by equipping the patrol vehicle with a management system including a device for analyzing RF interference resulting from poor equipment and a GPS to record and display both the position and measurement time of equipment due for corona interference measurement, the operator can accurately determine the operating condition of equipment on the ground without climbing poles while electricity flows through the lines. Although several exemplary embodiments of the present invention have been described for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

[industrial Applicability]

The present invention is applicable to patrol of power distribution lines during operation and detection of poor equipment. Particularly, the operator can accurately determine the operating condition of equipment on the ground without climbing poles while electricity flows through the lines.

Claims

[CLAIMS] [Claim l]

A system for patrolling overhead power distribution lines to detect the faulty components in the network by analyzing RF noise generated from the power line noise sources, the system comprising: configurable number of RF noise scanning receivers for scanning if an amplitude modulation-type radio interference frequency exists among received RF signals and registering a frequency with signal level greater than threshold (-9OdBm) in the monitoring target list; an RF monitoring receiver for continuously monitoring the registered monitoring target frequency, comparing the level of an

RF signal with the level of an audio signal, an power system frequency has been removed from the audio signal, grading the signals, and generating an alarm; and an analyzing and recording device for displaying information obtained by means of the receivers on a topographical map and analyzing and recording detection results. [Claim 2]

The system as claimed in claim 1, wherein the system is mounted on a vehicle so that operating conditions of medium volatge network are monitored on the ground without climbing the poles while electricity flows through the lines, and locate the point where the power line noise captured on the move.

[Claim 3]

The system as claimed in claim 1, further comprising a GPS receiver to synchronize the location data with GIS information to set the optimal patrol route and get guidnace patrol path and display the measured data over the mapping data.

[Claim 4]

A system for patrolling overhead power distribution lines and detecting poor power distribution components by being mounted on a patrol vehicle, the system comprising: a receiving antenna for receiving radio frequencies emitted from power distribution line equipment; configurable RF scanning receivers for scanning non-occupied frequency spectrums to detect the amplitude modulation-type radio interference frequency signals and adding the newly found frequencies into the monitoring target list; an RF monitoring receiver for continuously monitoring the monitoring target frequency, comparing the level of an RF signal with the level of an audio signal without power system frequency, grading the signals, and generating an alarm at a place of potential danger; a GPS receiver for receiving installation information regarding power distribution lines to be monitored from a power distribution management system run by a power company, determining a patrol path based on the information, and guiding a patrol of the power distribution lines along an optimized path so that analysis of the obtained information, positions of equipment due for interference measurement, measurement time, velocity of the moving patrol vehicle, and movement direction information are recorded and displayed; and an analyzing and recording device equipped with a program for displaying information obtained by means of the receivers on a topographical map and recognizing a corresponding degree of danger for each grade so that detection results are analyzed and recorded.

[Claim 5] The system as claimed in claim 1 or 4, wherein the RF noise scanning receiver is adapted to recognize the occupied RF signal bandwidth to avoid the scanning frequencies in a 10-600MHz band of a corresponding region prior to a power distribution line patrol, continuously monitor the frequency bandwidths not being occupied, and detect the RF interference signal from the faulty components in the distribution line networks.

[Claim β]

The system as claimed in claim 1 or 4, wherein the RF monitoring receiver is adapted to continuously monitor the frquencies detected by RF scanning receiver.

[Claim 7]

The system as claimed in claim 1 or 4, wherein the RF monitoring receiver comprises comparator to determine the power line noise by compare the level between RF signal and Af level without power system frequency signa.

[Claim 8]

The system as claimed in claim 1 or 4, wherein the RF monitoring receiver comprises of an audio signal output limiter if RF power line noise _ is in-flowing such as impulsive interference signal from power line. [Claim 9] A method for patrolling overhead power distribution lines and detecting poor power distribution components by analyzing RF interference, the method comprising the steps of: scanning non occupied frequencies to detect the AM mode signal greater than thresholde level (-9OdBm) ; register the newly found AM mode RF noise frequencies into the monitoring target frequency list; comparing the field strength of the RF signal level with an audio signal after removing power system frequency; and displaying an RF interference grade based on the result of comparison and generating an alarm according to the result of RF interference analysis, whereinthe steps are conducted while a patrol vehicle equipped with a corresponding system is on the move. [Claim lθ]

The method as claimed in claim 9, wherein the step of scanning a received frequency comprises the steps of: connecting an RF scanning receivers and RF monitoring receivers to an antenna for receiving RF interference signals; scanning to detect the amplitude modulation-type radio interference signal among selelcted noise free spectrum bandwidths by RF scanning receivers; recording frequencies detected as AM type RF noise with level greater than threshold level when the newly detected frequencies are new into the continuous monitoring frequency list.

[Claim 11]

The method as claimed in claim 10, wherein, in the step of scanning a received frequency, frequencies in a 10-600Mhz band are scanned continuously, and frequencies of -9OdBm or higher are added to a monitoring target list, -9OdBm being set as a threshold value for detecting RF interference signals.

[Claim 12] The method as claimed in claim 9, wherein the step of processing power frequency interference comprises the steps of: continuously tuning frequencies enumerated on the monitoring target frequency list by using the RF monitoring receiver; and measuring an RF field strength level value for each frequency and recording the value together with time and position information.

[Claim 13]

The method as claimed in claim 9, wherein the step of comparing the field strength of the RF interference with the audio signal comprises the steps of: determining if 60Hz power interference is included; removing 60Hz interference signal from audio frequency signal; and comparing the RF field strength value with a level value of the audio signal .

[Claim 14]

The method as claimed in claim 9, wherein the step of comparing the field strength of the RF interference with the audio signal comprises the steps of: determining if 50Hz power interference is included; removing 50Hz interference signal from audio frequency signal; and comparing the RF field strength value with a level value of the audio signal.

[Claim 15]

The method as claimed in claim 9, wherein the step of displaying an RF interference grade and generating an alarm comprises the steps of: determining a power interference grade included in an RF signal for each section; comparing the determined interference grade with a previous level; displaying an identical interference grade in the case of an identical level and displaying a new interference grade in the case of a different level; determining if the interference grade is equal to or higher than a setup level; and determining an alarm level based on the interference grade when the interference grade is equal to or higher than the setup level and outputting different kinds of alarms according to the interference grade. [Claim lβ]

The method as claimed in claim 9, wherein, after RF interference analysis is completed, obtained information is displayed on a map on a screen of an analyzing and recording device differently according to respective degrees of danger.