WO2021245511A1

WO2021245511A1 - Line fault locator

Info

Publication number: WO2021245511A1
Application number: PCT/IB2021/054682
Authority: WO
Inventors: Sinn MEKKHACHAI; Sajjakorn RATTANAKORNROJ; Suwan PANSAMNEING; Anucha KOYANYONG; Siwadol BUTAKHIEO; Krittiya KITTIWITTAYAPONG; Wattana POONCHAIYAPHUM
Original assignee: Electricity Generating Authority Of Thailand (Egat)
Priority date: 2020-06-05
Filing date: 2021-05-28
Publication date: 2021-12-09

Abstract

The invention relates to a line fault locator comprises a plurality of pulse generators, an interface unit, an alarm unit, a display unit, and a processor unit connected to the plurality of pulse generators, the interface unit, the alarm unit, and the display unit respectively; wherein the line fault locator is a radar type line fault locator for identifying line fault location on transmission lines without a line trap; wherein the line fault locator further comprises a GPS satellite receiver connected to the processor; and wherein the plurality of pulse generators comprising a Phase A pulse generator, a Phase B pulse generator, and a Phase C pulse generator; said Phase A pulse generator, Phase B pulse generator, and Phase C pulse generator connected to the processor. This line fault locator allows to save time in determining faults, reduce operating costs and reduce impact on users caused by power failure.

Description

LINE FAULT LOCATOR

TECHNICAL FIELD

This invention relates to a line fault locator.

BACKGROUND OF THE INVENTION

Line Fault Locators (LFL) are generally used to identify fault locations on power transmission lines that are installed in all areas of the country. Transmission lines have many types which are different in voltage level such as 115 kV, 230 kV, 500 kV including high voltage direct current (HVDC), some of which have distance over 300 kilometers. Faults usually happen on power transmission lines, which are generally caused by

1) weather conditions and environment, e.g., heavy rains, thunderstorm, lightning strikes to transmission lines or electrical devices, trees falling on transmission lines, fallen power poles, broken power lines, or wildfires etc.

2) technical interruptions caused by; e.g., failure in the power generation system, an electrical device malfunction in the power transmission system and short circuit in the power transmission system, etc.

3) animals e.g., birds, cats, reptiles causing short circuit

4) Human, mostly by human's negligence or ignorance; e.g., reckless driving causing collision between cars and electric poles, use of machinery near transmission lines without caution, cutting down trees near power lines, burning crops under power lines, etc.

Line fault locator assists in identifying points of line faults and calculating distance from the line fault locator which saves time from clearing faults in the power transmission system, resulting in quick fixing of electrical devices by the operators at the occurring location. As a result, the power transmission system can be restored faster. There are many different types of line fault locators depending on the method of analyzing electromagnetic waves detected in the transmission lines when a fault occurs.

Type C Line Fault Locator (Type C LFL) with radar technique renders high precision by way of transmitting high-frequency waves into the transmission line and receiving the reflected signal from fault locating point. Type C LFL calculates a gap distance between fault points and the location of Type C LFL. However, Type C LFL has limitation as it must be used with line trap or blocking coil which is a resonance circuit installed on high voltage transmission lines to prevent a high-frequency signal from the power line communication system from interrupting an operation of a protection system in a substation. The line trap allows Type C LFL to transmit a pulse signal to determine the distance of the fault occurred in the transmission line.

Japanese Patent Application Publication No. JP 17170882 A discloses an improvement in reliability of fault point locating device to withstand high voltage by separating circuit parts. The fault point locating device according to JP 17170882 A must still work with blocking coils BC1 BC2 BC3 (or line traps).

Currently, blocking coils or line traps are very expensive because communication is not transmitted via power line system anymore, and there are only a few blocking coils or line traps manufacturers left at present. For new transmission lines, there is no installation of blocking coils or line traps, which is no longer possible to install Type C LFL. Therefore, the Type C LFL is eventually out of the industry.

Chinese Patent Application Publication No. CN 107918079 A discloses a method of transmitting frequencies into transmission lines one phase at a time through the high-voltage switches that are connected to three-phase transmission lines of each phase. Then, a detector device connected to transmission line at another location receives signals through a high-voltage transformer connected to the transmission line and calculates to identify the fault location. According to CN 107918079 A, only a single-phase earth fault can be detected.

The transmission of frequencies through the high-voltage switches connected to the three-phase transmission lines, according to CN 107918079 A, then the detector connected to another location that receives the signals from a high-voltage transformer connected to the transmission line and uses the signals for calculating the result which requires the detection apparatuses to be in different locations in the power transmission system to receive signals. The detection apparatuses cannot perform as both transmitter and receiver. They will be inoperable if the communication failure occurs. Up to three very expensive, high-voltage switches are also required to be connected to the transmission lines.

There is no line fault locator with precision available in new power transmission system due to a discontinuation of blocking coils or line traps which are expensive. As a result, when fault occurred on transmission lines, it is not possible to accurately identify the line fault location. Therefore, repairing the fault is difficult and time consuming; that is, a travel to inspect the transmission lines from the primary power substation to the secondary power substation is required. Some travel routes are several hundred kilometers, and some areas are inaccessible making it difficult to inspect the transmission lines, which takes a long time to restore the power transmission system to its normal supply condition. This affects the reliability index of the power transmission system, which displays an average time of power outages caused by interruptions in the power transmission system compared to all power distribution points, also known as SAIDI (System Average Interruption Duration Index) by measuring the power outage time as of 1 minute or more per total number of power distribution points. Therefore, the operators need to restore the power transmission system as quickly as possible, which may result in accidents or cause a widespread power outage (Black Out).

An example of a typical line fault locator connected to a power transmission system with a line traps is shown in Figure 4.

Figure 4 shows the connection of the typical line fault locator to the power transmission system with line traps that comprises a Phase A voltage transformer 10', a Phase B voltage transformer 11', and a Phase C voltage transformer 12' connected to a Phase A transmission line 13, a Phase B transmission line 14, and a Phase C transmission line 15, respectively, with three line traps 22 at the primary power substation 23. The structure of this power transmission system is costly. Figure 4 also shows an example of an occurrence of a fault 25.

SUMMARY OF THE INVENTION

The line fault locator according to this invention comprises a plurality of pulse generator, an interface unit, an alarm unit, a display unit, and a processor connected to the plurality of pulse generators, the interface unit, the alarm unit, and the display unit, respectively; wherein the line fault locator is a radar type line fault locator for identifying line fault location on transmission lines without a line trap; wherein the line fault locator further comprises a GPS satellite receiver connected to the processor; and wherein the plurality of pulse generators comprising a Phase A pulse generator, a Phase B pulse generator, and a Phase C pulse generator connected to the processor, preferably, said Phase A pulse generator, Phase B pulse generator, and Phase C pulse generator generates power transmission line test signals with frequency of 80 - 500 kHz, the signal transmitting interval of 20 - 50 microseconds, the signal voltage level of 0.6 - 1.2 kilovoltage, and output impedance of 300 - 600 ohms.

The purpose of this invention is to provide improved line fault locator having several technical advantages. Technical advantages of the line fault locator according to this invention include an ability to operate with transmission lines without a line trap, an applicability with all voltage level of the transmission lines, an ability to detect signals quickly, an ability to process line fault location quickly and precisely, an ability to receive remote operation commands, an ability to identify cause of the fault each time, an ability to test power transmission system manually, and an ability to detect fault location in the blind zone. These allow the operators to quickly resolve faults, save time in determining faults, reducing operating time and costs, and reducing impact on users caused by power failure, etc.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows components of the line fault locator according to this invention.

Figure 2 shows a connection of one line fault locator according to this invention to the power transmission system.

Figure 3 shows a connection of two line fault locators according to this invention to the power transmission system.

Figure 4 shows a connection of a typical line fault locator to the power transmission system with line traps.

DETAILED DESCRIPTION

The line fault locator according to this invention will be followingly described in more details referring to the attached drawings.

As shown in Figure 1, the line fault locator according to this invention comprises a plurality of pulse generators 1, 2, 3, an interface unit 6, an alarm unit 7, a display unit 8, and a processor unit 5 connected to the plurality of pulse generators 1, 2, 3, the interface unit 6, the alarm unit 7, and the display unit 8, respectively;

The line fault locator according to this invention is a radar type line fault locator for identifying line fault location on transmission lines without a line trap.

The line fault locator according to this invention further comprises a GPS satellite receiver 4 connected to the processor unit 5.

According to this invention, the plurality of pulse generators 1, 2, 3 comprise a Phase A pulse generator 1, a Phase B pulse generator 2 and a Phase C pulse generator 3 connected to the processor unit 5. Preferably, the Phase A pulse generator 1, Phase B pulse generator 2, and Phase C pulse generator 3 generates the transmission line test signals with the frequency of 80 - 500 kHz, signal transmitting interval of 20 - 50 microseconds, signal voltage level of 0.6 - 1.2 kilovoltage, and output impedance of 300 - 600 ohms.

According to this invention, the output impedance is preferably 400 - 500 ohms.

According to this invention, the Phase A pulse generator 1 connects to a Phase A voltage transformer 10 connected to a Phase A transmission line 13, the phase B pulse generator 2 connects to a Phase B voltage transformer 11 connected to a Phase B transmission line 14, and the Phase C pulse generator 3 connects to a Phase C voltage transformer 12 connected to a Phase C transmission line 15, respectively.

The phase A pulse generator 1, phase B pulse generator 2, and phase C pulse generator 3:

- generates test signals for testing the Phase A transmission line 13, the Phase B transmission line 14, and the Phase C transmission line 15, respectively, and

- receives the signals reflected from the Phase A transmission line 13, the Phase B transmission line 14, and the Phase C transmission line 15 via the Phase A voltage transformer 10, the Phase B voltage transformer 11, and the Phase C voltage transformer 12, respectively.

According to this invention, the GPS satellite receiver 4 receives clock signals from GPS satellites and generates time stamps on detected fault events, so that the operators can simply analyze each fault event.

According to this invention, the interface unit 6 acts as an interface for direct connections with transferable data external to:

- define new work process via a signal cable 16 connected to external programming tools, for example, a parameter adjustment apparatus for each fault event in the power transmission system, which are different, most likely required new adjustment for discrepancy in parameter's setting (e.g., signal start time tolerances, signal frequency tolerances, signal voltage tolerances), etc.

- transceive operation management data via a signal cable 17 connected to an external management system, for example, to check for malfunctions of the line fault locator and transmit data to the management system so that administrators can inspect and fix such faults, etc.

- transceive data for controlling an operation of the line fault locator via a signal cable 18 connected to an external telecommunication link, for example, able for an operator to control and monitor operation remotely, and

- receive a command signal from a distance relay via a signal cable 19 connected to an external distance relay, for example, once a transmission failure occurred, the distance relay instructs to disconnect the device associated with the transmission line and also instructs the apparatus to transmit signal for inspection of fault's location, etc.

According to this invention, the processor unit 5 controls the operation of the line fault locator, processes data/signal data relating to output signals and reflected signals to determine distance and fault location and transmits data to display at the display unit 8 by receiving signals from the interface unit 6.

According to this invention, the alarm unit 7 transmits signals to a remote terminal unit (RTU) of a power substation via a signal cable 20 connected to the RTU when a fault is detected on a transmission line.

According to Figure 2, the line fault locator according to this invention connects to a power transmission system. The line fault locator connects to a primary power substation 23 connected to a secondary power substation 24 via the Phase A transmission line 13, the Phase B transmission line 14, and the Phase C transmission line 15. The Phase A voltage transformer 10, the Phase B voltage transformer 11, and the Phase C voltage transformer 12 connects to the Phase A transmission line 13, the Phase B transmission line 14, and the Phase C transmission line 15, respectively. As shown in Figure 2, it indicates that the line fault locator according to this invention is operable with the power transmission system without a line trap, which can efficiently save costs.

As shown in Figure 3 , the line fault locators according to this invention connect to the power transmission system without a line trap. One line fault locator is installed and connected to the transmission line at the primary power substation 23 while another one is installed and connected to the transmission line at the secondary power substation 24 allowing an effective detection of the fault location in blind zone

The line fault locator according to this invention can be installed and connected to the transmission line without a line trap. It can also be installed either at the primary power substation 23 or the secondary power substation 24 or both the primary power substation 23 and the secondary power substation 24.

In case of a fault 25 in an electrical system, the line fault locator at the primary power substation 23 will be activated to operate via a signal cable 19 of the distance relay connected to the protection system in a power substation. The line fault locatortransmits one test signal at a time to the Phase A transmission line 13, the Phase B transmission line 14, and the Phase C transmission line 15, then waits forthe signal reflected from each transmission line, and transmits to the processor unit 5 to process the distance at which the fault is occurred. After that, the line fault locator at the secondary power substation 24 is activated to perform in the same manner via the communication line 18. The processor unit 5 sends the fault location result to show on the display unit 8 to the operator after finish processing.

The line fault locator according to this invention is a radar type for identifying line fault location on transmission lines without a line trap which yields high accuracy. Frequency wave is transmitted into the transmission line and reflected when fault is detected. This is used to calculate location as a distance from the fault location to the line fault locator, which is necessary to reduce system average of interruption duration caused by a fault in the power transmission system or SAIDI, and to increase reliability index of power transmission system. This indicates that the country's power transmission system is more stable and reliable.

This line fault locator according to this invention is developed with improved features to provide several technical advantages, which are: ability to operate with the transmission lines without a line trap - this is because this invention is developed to generate an output impedance (Ol) at 300 - 600 ohms, preferably 400 - 500 ohms. An output impedance of a typical line fault locator is at 75 ohms, which would require a matching impedance equipment to balance the impedance; applicability with all voltage level of the transmission lines, in conjunction with capacitor voltage transformers (CVT) which is used to transform voltages lower for operators' safety and suitable for a measurement range of the voltmeter. A basic protection system in a power transmission line has specified a voltage standard where the CVT has a port for transmitting a signal to inspect line fault; ability to quickly detect signals; i.e., one signal transmission (one phase) takes 1 to 2 milliseconds, thus six signal transmissions (three phases) between both substations take just 18 milliseconds; ability to process line fault location on transmission lines quickly and precisely, i.e., process one fault event in just 18 milliseconds (three phases) whereas a typical line fault locator requires 320 milliseconds (1 phase) to do so; ability to receive remote operation commands, especially from autonomous control centers, while a typical line fault locator requires an operator to travel to inspect the line fault locator at the site; ability to easily determine cause of fault each time due to GPS system, which has a time tracking function and time analysis function to analyze event's data compared to the line fault event by means of time stamp principle using signals from GPS satellites; ability to display calculation result for distance and location of the fault, i.e., ability to transmit the test signal for each phase of transmission line and receive the reflected signal for each phase of transmission line, and then forward to the processor 5 to process the distance and the location of the fault; ability to conduct a manual test for the power transmission system without any interruption in the power transmission system, i.e., ability to conduct the test at any time and able to test the transmission line after repair; ability to detect fault location in the blind zone where the typical line fault locator cannot do. This is done by installing one line fault locator at the primary power substation 23 and another one on the high voltage transmission line at the secondary power substation 24.

As a result of these advantages, it allows, for example, operators to quickly resolve the fault, saves time in determining faults, reduces operating time and costs, and reduces impact on users caused by power failure, etc.

Throughout the present specification and the accompanying claims, the word "Transmission Line" used herein can refer to "High Voltage Transmission Line", "Medium Voltage Transmission Line" or "Low Voltage Transmission Line". The word "Voltage Transformer" also includes "Capacitor Voltage Transformer". The "Primary Power Substation" denotes "Power Distribution Station" and the "Secondary Power Substation" denotes "Power Receiving Station".

While multiple embodiments are disclosed, still other embodiments of the present invention will become apparent to those skilled in the art from the following detailed description, which shows and describes illustrative embodiments of the invention. As will be realized, the invention is capable of modifications in various obvious aspects, all without departing from the spirit and scope of the present invention. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not restrictive.

Claims

WHAT IS CLAIMED IS:

1. A line fault locator comprises a plurality of pulse generators (1, 2, 3), an interface unit (6), an alarm unit (7), a display unit (8), and a processor unit (5) connected to the plurality of pulse generators (1, 2, 3), the interface unit (6), the alarm unit (7), and the display unit (8) respectively; wherein the line fault locator is a radar type line fault locator for identifying line fault location on transmission lines without a line trap (22); wherein the line fault locator further comprises a GPS satellite receiver (4) connected to the processor (5); and wherein the plurality of pulse generators (1, 2, 3) comprising a Phase A pulse generator (1), a Phase B pulse generator (2), and a Phase C pulse generator (3); said Phase A pulse generator (1), Phase B pulse generator (2), and Phase C pulse generator (3) connected to the processor (5), preferably, said Phase A pulse generator (1), Phase B pulse generator (2), and Phase C pulse generator (3) generates power transmission line test signals with a frequency of 80 - 500 kHz, signal transmitting interval of 20 - 50 microseconds, signal voltage level of 0.6 - 1.2 kilovoltage, and output impedance of 300 - 600 ohms.

2. The line fault locator as claimed in claim 1, wherein the output impedance is preferably 400 - 500 ohms.

3. The line fault locator as claimed in claim 1, wherein the Phase A pulse generator (1) connects to a Phase A voltage transformer (10) connected to a Phase A transmission line (13); the Phase B pulse generator (2) connects to a Phase B voltage transformer (11) connected to a Phase B transmission line (14); and the Phase C pulse generator (3) connects to a Phase C voltage transformer (12) connected to a Phase C transmission line (15) wherein the Phase A pulse generator (1), Phase B pulse generator (2), and Phase C pulse generator (3):

- generates test signals for testing the Phase A transmission line (13), Phase B transmission line (14) and Phase C transmission line (15), respectively, and transmits said test signals respectively via the Phase A voltage transformer (10), Phase B voltage transformer (11) and Phase C voltage transformer (12); and

- receives reflected signals respectively from the Phase A transmission line (13), Phase B transmission line (14), and Phase C transmission line (15) via the Phase A voltage transformer (10), Phase B voltage transformer (11), and Phase C voltage transformer (12).

4. The line fault locator as claimed in claim 1, wherein the GPS satellite receiver (4) receives clock signals from GPS satellites and generates time stamps on detected fault events.

5. The line fault locator as claimed in claim 1, wherein the interface unit (6) acts as an interface for direct connections with transferable data external to: - define new work process via a signal cable (16) connected to external programming tools;

- transceive operation management data via a signal cable (17) connected to an external management system;

- transceive data for controlling an operation of the line fault locator via a signal cable (18) connected to an external telecommunication system; and

- receive a command signal from a distance relay via a signal cable (19) connected to an external distance relay.

6. The line fault locator as claimed in claim 1, wherein the processor unit (5) controls an operation of the line fault locator, processes data/data signals relating to output signals and reflected signals to determine distance and fault location, and transmits data to the display unit (8), by receiving signals from the interface unit (6).

7. The line fault locator as claimed in claim 1, wherein the alarm unit (7) transmits signals to a remote terminal unit (RTU) of a power substation via a cable (20) connected to the RTU when a fault is detected on a transmission line.

8. The line fault locator as claimed in any of claims 1 to 7 is installed and connected to a power transmission system at a primary power substation (23) or a secondary power substation (24) or both the primary power substation (23) and secondary power substation (24).