GB2337167A

GB2337167A - Testing continuity of power transmission lines

Info

Publication number: GB2337167A
Application number: GB9906065A
Authority: GB
Inventors: Ian Foley
Original assignee: HAVERHILL GENERATORS Ltd; WINDEN RAIN Ltd
Current assignee: HAVERHILL GENERATORS Ltd; WINDEN RAIN Ltd
Priority date: 1998-03-19
Filing date: 1999-03-18
Publication date: 1999-11-10
Anticipated expiration: 2019-03-18
Also published as: GB9805721D0; GB2337167B; GB9906065D0; HK1023181A1

Abstract

A power line, particularly used for railway track signalling, has a number of signalling locations 16A-16D. Switches 18,20 are provided at each side of each location in both live and neutral lines. When a power supply is connected to the line, an input or upstream side transformer 24 produces an output which closes switches 18A, 18B and also closes a relay 19 allowing continuity of the line as far as the next downstream location to be tested. Only if a normal voltage is detected is a signal produced to close switches 20A,20B and thus continue power supply to the next location. A fault indicator 34 is actuated if the detected voltage indicates an open or short circuit condition. A similar procedure takes place at successive locations. If a fault is found, a portable generator 14 can be connected.

Description

2337167 Power Lines This invention relates generally to power transmission

lines.

Power transmission lines are commonly used for railway signalling, where the power line, typically at 65OV a.c., extends along the side of the track between signalling points, known as locations, at which the line is tapped to provide via a transformer a reduced voltage, typically 1 1OV, for controlling a signal at that location.

Conventionally, at each location, continuity of the power line is achieved by means of simple mechanical connecting links. If an open circuit develops somewhere along the line, the power line becomes inoperative and, if a short circuit develops, a fuse is blown at a control station at the head of a section of the line, and the power line again becomes inoperative. There may be many locations between successive control stations along the line and, in the event of a power line failure, it is known only that a section between two control stations has failed, rendering the signalling in that section of track inoperative. Each location, possibly as many as 20 or 30, has to be tested until the location of the fault is determined, over a section of track perhaps 50 km. long, typically to enable a portable generator to be connected up at the location where the failure has occurred. In the case of a short circuit, however, power often cannot be restored until the fault is rectified. 71e consequence of a failed section of power line may therefore prevent the running of trains along a failed section of track for a long period.

It is an aim of this invention to provide an improved power transmission line, especially but not exclusively applicable to railway line signalling.

According to the invention, there is provided a power transmission line, wherein at each of a number of locations along the line, the live and neutral conductors are closable by electrically powered switches on both sides of the location to provide power line continuity and, when the switches on the upstream side of the location are closed, an electrical detector arrangement at the location is operative to check continuity of the power line on the downstream side up to the next location and power is supplied to close the switches on the downstream side of the first mentioned location only if this continuity is positively determined.

Preferably, the system is bi-directional, so that either side of each location may be considered the upstream or downstream side.

Preferably, at each location, means interconnecting the live and neutral conductors on the upstream side of each location provides a path for the detector signal.

71e invention is particularly applicable to railway signalling, where the locations are signalling points along the track.

In a preferred system, at each location, a transformer or other means interconnecting the live and neutral conductors on the upstream side of each location provides a power supply signal for the detector arrangement. 7be detector arrangement then causes a current or voltage to be applied up to the transformer or other means on the upstream side of the next location. 71e detector arrangement senses if there is a normal voltage developed between the upstream live and neutral conductors, an abnormal voltage indicating a short circuit, or a different abnormal voltage indicating an open circuit. Only in the first case does the detector system permit the supply of power for closing the switches on the downstream side of the first mentioned location, thereby to switch through the 65OV a.c. supply from the upstream side to the downstream side of the location 71e test voltage sensed may conveniently be a d.c. voltage, obtained via a rectifier associated with the downstream side transformer or other interconnecting means.

The detector system preferably includes a fault indicator.

7be above-described power transmission line has the advantage that power is maintained up to any location immediately preceding a fault which has developed in the line, whereby the site of a fault is immediately determinable. It is then possible, for example, to insert a portable generator in the line at the location following the fault, quickly restoring the operative state of the signalling system. By connecting a portable generator to the line on each side of the short circuit, for example to opposite ends of the line, power can be restored to the whole line without first rectifying the fault, which is contained within a now isolated section of the line.

The detector system can also be adapted to indicate the nature of a fault, e.g. open circuit or short circuit, which has developed.

The invention is further described with reference to the accompanying drawing, in which the single figure is a circuit diagram of part of a power line in accordance with the invention.

Referring to the drawing, there is shown a length of power line 10 extending from a control station 12 and a portable generator 14. 77here are four signalling locations 16A, 16B, 16C and 16D on this length of line.

Each location comprises a pair of contactors 18A, 18B on the upstream side, as marked for location 16B for example, and a pair of contactors 20A, 20B on the downstream side. Tle contactors axe able to close to achieve continuity of the live and neutral conductors of the power line via links 22A, 22B. In the drawing, the contactors are all shown open but, when a 65OV a.c. supply is present on the line, continuity of the power supply would be established up to location 16D. At location 16D, it is assumed that, as a result of a fault at this location, contactors 20A, 20B have failed to close, and the portable generator 14 has been connected to provide continuation of power downstream.

Taking location 16B as an example, when the 65OV supply is present on the upstream side, transformer 24 and rectifier 26 provide a d.c. signal for powering a detector arrangement generally referenced 28. This enables the detector arrangement to energise the contactors 18A, 18B, which thereby close. In addition, a resistor 30 is switched into circuit by a test relay 19, creating a potential divider formed by the resistor 30, a transformer 32 on the downstream side of the location, and the transformer 24 on the upstream side of the location 16C.

The detector arrangement then detects the voltage present on the power line on the downstream side of the location 16B up to the next location 16C, where contactors 20A, 20B currently remain open. Three possible voltages may be sensed; firstly a normal voltage, secondly an abnormal voltage due to an open circuit on the line, and thirdly an abnormal voltage due to a short circuit on the line.

Only in the first case of a normal voltage does the detector arrangement deenergise the test relay 19 and provide a signal for closing the contactors 20A, 20B, whereby to continue the power supply downstream. As previously indicated, in the drawing it is assumed that a fault has been detected between locations 16D and 16C and consequently contactors 20A, 20B have not closed.

The detector arrangement may include a fault indicator 34.Even if the developed fault is a short circuit, portable generators can be connected on the downstream sides of the fault to restore power to the whole line, without waiting for the short circuit to be repaired, since the fault is now contained within an isolated section of the line.

As can be seen from the drawing, the arrangement is bi-directional, so that in the foregoing either side of each location may be considered the upstream side or the downstream side.

Claims

1 - A power transmission line, wherein, at each of a number of locations along the line, the live and neutral conductors are closable by electrically powered switches on both sides of the location to provide power line continuity and, when the switches on the upstream side of the location are closed, an electrical detector arrangement at the location is operative to check continuity of the power line on the downstream side up to the next location and power is supplied to close the switches on the downstream side of the first mentioned location only if this continuity is positively determined.

2. A power line according to claim 1, wherein the system is bidirectional, so that either side of each location may be considered the upstream or downstream side.

3. A power line according to claim 1 or claim 2, applied to railway track signalling, wherein the said locations are signalling points along the track.

4. A power line according to any of claims 1 to 3, wherein, at each location, means interconnecting the live and neutral conductors on the upstream side of each location provides a path for the detector signal.

5. A power line according to any of claims 1 to 4, including a fault indicator.

6. A power line according to any of claims 1 to 5, wherein the detector arrangement is adapted to sense a normal voltage, an abnormal voltage due to an open circuit on the line, and an abnormal voltage due to a short circuit on the line.

7. A power transmission line substantially as hereinbefore described with reference to the accompanying drawing.