AND METHOD OF OPERATING

Field

The present disclosure relates to protection systems for railway electrification systems, and to associated methods.

Background

Railway electrification systems use exposed, live conducting elements which allow trains to be powered by collecting cur rent there-from. Where these conducting elements run close to structures, vegetation or uncontrolled public areas, short circuit faults can occur. Short circuits cause intense heat ing that may lead to equipment damage in the electrification system, as well as potentially causing serious injury. Ulti mately, repair or replacement of damaged equipment caused by short circuits causes significant disruption to railway oper ations, and incidents involving public and railway staff re sult often lead to major injuries or deaths.

Traditional railway protection systems use distance protec tion devices installed at each substation to detect short circuits, and associated circuit breakers that open to enable the fault to be cleared. Installing and maintaining the nec essary hard-wired interconnections in this type of system is expensive, and still even with a well designed and maintained system a typical UK fault clearance duration is relatively slow, ranging from 100-350ms.

More recently, protection systems based on communication net works have been introduced, in which protection functions are managed using programmable logic controllers provided in in telligent electronic devices at each substation. This has enabled techniques such as accelerated distance protection to be implemented. Communication between intelligent electronic devices in the protection system takes place under the IEC 61850 standard, and the protection system enables all circuit breakers which are required to operate to clear the fault to be opened more quickly. Currently known systems have im proved fault clearance duration to typically 60-100ms.

However, there is still a drive to achieve further reduction in fault clearance duration, as well as a drive to ensure good reliability of protection systems without increasing maintenance requirements.

Summary

According to the present disclosure there are provided sys tems and methods as set forth in the appended claims. Other features of the invention will be apparent from the dependent claims, and the description which follows.

Accordingly there may be provided a protection system for a railway electrification system comprising a plurality of sub stations, a plurality of conductor sections from which power can be delivered to trains, the conductor sections arranged between substations, and a plurality of power converters ar ranged to receive power from an electricity grid for supply to the substations and delivery to the conductor sections via the substations; wherein the protection system comprises: substation controllers operable to provide fault detec tion functionality for the conductor sections at the substa tions ;

circuit breakers at the substations, operable to discon nect a conductor section at the substation under the control of a substation controller;

the protection system characterised by:

a network connection between the substations and the power converters, by which the substation controllers can distribute protection control signals to the power convert ers; and

power converter controllers operable to perform protec tion functions at the power converters, in response to a pro tection control signal received from a substation over the network connection between the substation and the power con verter .

By providing a network connection between the substations and the power converters, the existence of a faults detected by the substation controllers can be rapidly communicated to the power converter controllers, in order that protection func tions for the railway electrification system can be performed at the power converters, for example in cooperation with pro tection functions performed by substations adjacent to a fault .

In one example, the substation controllers are operable to detect a fault on a conductor section next to the substation, and in response to detecting such a fault: to operate a cir cuit breaker to disconnect the conductor section at one end thereof; to distribute a protection control signal to the ad jacent substation such that the adjacent substation can, in response, operate a circuit breaker at the adjacent substa tion to disconnect the conductor section at the other end thereof; and to distribute a protection control signal to the power converters. In one example, the protection system com prise a network connection between adjacent substations by which the substation controllers can distribute protection control signals from one to the next, in order to operate a circuit breaker in the adjacent substation in the response to a detected fault.

In this way, inter-trip protection is achieved between sub stations and protection functions can in tandem be performed by the power converters in response to the protection control signal .

In one example, the power converter controllers are operable to perform protection functions comprising: interrupting sup ply to the substations; and restoring supply to the substa tions after previously interrupting supply to the substa tions . By suitable programming of the substation controllers and power converter controllers, and choice of power converter components, a rapid response time between fault detection and interruption of power to the substations is possible.

In one example, the circuit breakers at the substations are operable to disconnect and reconnect a conductor section at the substation under the control of the substation control ler. In one example, the circuit breakers at the substations are operable to disconnect and reconnect a conductor at the substation under the control of the substation controller in a period while the power converter controllers have inter rupted supply to the substations.

In this way, the circuit breakers at the substations may be operated off-load in response to a fault being detected, thereby increasing substation reliability.

In one example, the power converter controllers are integrat ed with the power converters. In one example, the power con verters each comprise a power converter controller. In one example, the substation controllers are integrated with the substations. In one example, the substations each comprise a substation controller. In one example each power converter is arranged to provide power to a group of substations.

Providing controllers in the power converters in this way en ables a reduction in costs compared to providing components with rapid response times and more sophisticated control functionality across the many substations on the railway electrification system.

In one example, the network connections between adjacent sub stations are provided as data network connections, for exam ple as IEC 61850 network connections. In one example, the network connection between the substations and the power con verters are provided as data network connections, for example as IEC 61850 network connections. In one example the network connections between adjacent substations and between substa tions and power converters use the same network protocols as one another.

In one example, the conductor sections are sections of over head line equipment.

In one example the power converters are AC to AC converters. In one example, the power converters are static frequency converters. In one example, the power converters are three phase to single phase converters.

Accordingly there is provided method of operating a protec tion system for a railway electrification system comprising a plurality of substations; a plurality of conductor sections from which power can be delivered to trains, the conductor sections arranged between substations; and a plurality of power converters arranged to receive power from an electrici ty grid for supply to the substations and delivery to the conductor sections via the substations, the method compris ing :

detecting a fault on a conductor section between substa tions ;

generating a protection control signal in response to the detected fault;

delivering the protection control signal to the power converters over a network connection and in response control ling the power converters to perform a protection function; and

subsequently disconnecting the conductor section on which the fault was detected at substations either side of the fault.

In one example, the method is performed using the protection system and/or in a railway electrification system as herein- described . In one example, the controlling the power converters to per form a protection function comprises controlling the power converters to interrupt supply to the substations in response to the protection control signal.

In one example, the disconnecting the conductor section com prises comprising the steps of: operating a circuit breaker at a substation to disconnect the conductor section at one end thereof; distributing a protection control signal to an adjacent substation such that the adjacent substation oper ates a circuit breaker at the adjacent substation to discon nect the conductor section at the other end thereof.

In one example, the controlling the power converters to per form a protection function comprises step of controlling the power converters to restore supply to the substations, after the step of disconnecting the conductor section on which the fault was detected at substations either side of the fault.

In one example, the method comprises the further step of re connecting the conductor section on which the fault was de tected, at substations either side of the fault.

Brief Description of the Drawings

Examples of the present disclosure will now be described with reference to the accompanying drawings, in which:

Figure 1 shows an example embodiment of the protection system incorporated into a railway electrification system; and

Figure 2 shows an example embodiment of a method of op erating a protection system for a railway electrification system.

Detailed Description Referring now to Figure 1, there is shown an example embodi ment of the protection system, incorporated into a railway electrification system. The railway electrification system is a high voltage AC system in which power from an electrici ty supply grid G is delivered to trains via overhead line equipment including overhead lines 0 that are formed in con ductor sections 10, 10 ' -15, 15 ' .

Between the electricity supply grid G and the overhead lines 0 are power converters 20-23. The power converters 20-23 are provided as three phase to single phase static frequency con verters with associated power converter controllers 200-203. The output of the power converters 20-23 is delivered to feeder substations 30,34, with further substations along the overhead lines 0 provided between the conductor sections 10, 10 ' -15, 15 ' of the overhead lines 0. As shown schematical ly, the conductor sections 10, 10 ' -15, 15 ' on each of the over head lines 0 are provided with suitable isolation components I between one and the next.

The protection system further comprises substation control lers 300-304. The substation controllers 300-304 operate to provide fault detection functionality for the conductor sec tions 10, 10 ' -15, 15 ' at either side of the associated substa tions 30-34. In the example embodiment of Figure 1, each substation 30-34 comprises its own substation controller 300- 304. In this way, so that scaling the system is made easier. The substation controllers 300-304 are provided as intelli gent electronic devices, which can control circuit breakers, illustrated as X, at the associated substation 30-34 as part of their functionality. By operation of the circuit breakers X at the substations 30-34, under the control of the substa tion controllers 300-304 it is possible to disconnect adja cent conductor sections at either side of each of the substa tions 30-34.

The protection system further comprises a first network con nection 1, provided between the substations controllers 300- 304 and the power converter controllers 200-203. The first network connection 1 is shown between substation 32 and each of the power converters 20-23, but it is to be understood that the other substations also have a corresponding first network connection 1. The first network connection 1 is a wired connection configured for data transfer according to the IEC 61850 network protocol.

A second network connection 2, also a wired connection con figured for data transfer according to the IEC 61850 network protocol, is also provided as part of the protection system. The second network connection 2 is shown only between substa tions 32 and 33, but is present between each substation and the next in order to enable inter-trip between substations.

Using the first network connection 1 the substation control lers 300-304 distribute protection control signals to the power converters 20-23 over the first network connection 1.

In response the power converter controllers 20-23 are ar ranged to operate to perform protection functions.

The substation controllers each 300-304 operates to detect a fault on a conductor section next to their substation 30-34. For example, a short circuit fault F on the conductor section 13 occurs near to the substation 32. The substation control ler 302 recognises the short circuit based on High Speed Overcurrent detection.

In response to detecting the short circuit fault, the substa tion controller 302 performs a number of functions. To iso late the short circuit by disconnecting the conductor section 13, the substation controller 302 operates a local circuit breaker X in the substation 32 to disconnect one end of the conductor section 13. The end in question is the end which connects to the substation 32. In addition, to isolate the other end of the conductor section the controller 302 sends a protection control signal over the second network connection 2 to the adjacent substation 33. The adjacent substation 33, in response to receipt of the protection control signal by its substation controller 303, operates a circuit breaker X in the substation 33 to disconnect the conductor section at the other end thereof. Further in addition to controlling the local operation of circuit breaker X in the substation 32 and sending the protection control signal over the second network connection 2, the substation controller 302 also dis tributes a protection control signal to the power converter controllers 200-203 of each of the power converters 20-23, over the first network connection 1.

The power converters 20-23 receive the protection control signal at the power converter controllers 200-203 over the first network connection 1 and are optimised to react very quickly. The power converters 20-23 comprise large, complex pieces of electrical equipment, typically provided with con trol systems and current limiting functionality built in, which in response to the protection control signal can be op erated to reduce the current supplied to the substations 30- 34. That is, all the power converters 20-23 operate together in response to a protection control signal received over the first network connection 1 from any of the substations 30-34, so that supply from the power converters 20-23 is reduced and the substations are effectively disconnected at their input sides .

This enables the local and inter-trip circuit breaker opera tions to take place on a relatively longer timescale, with the circuit breakers involved opening under no load, or at least reduced load conditions.

The power converter controllers 200-203 are arranged to re connect supply to the substations 30-34 after a predetermined period of time, the predetermined period being long enough that the circuit breakers in the substations will have opened. The reconnection of supply may be arranged to take place gradually, with a ramping up of current available from the power converters 20-23 over a further predetermined peri- od after the period during which supply is interrupted ena bling the conductor sections aside from that with the fault to return to normal operation.

For example the power converter controllers may perform rapid reduction of fault current, which is then maintained for a defined period, effectively disconnecting the fault in milli seconds. The conductor section on which the fault is located can then be disconnected by circuit breakers opening off load. Following the predetermined period, which may for ex ample be ~50ms, the power converter controllers are arranged to restore their normal supply voltage over a short duration, for example 100ms.

Figure 2 shows an example method of operating a protection system for a railway electrification system. The method of Figure 2 is, for example, performed in the railway electrifi cation system of Figure 1.

At a first step, S101 a fault, for example a short circuit fault, is detected on a conductor section between substa tions. At step S102 a protection control signal is generat ed. At step S103 the protection control signal is delivered, over a network connection, to power converters of the railway electrification system. At step S104 the power converters perform a protection function in response to the received protection control signal, interrupting supply to the substa tions. At step S105 the conductor section on which the fault was detected is disconnected at either side of the fault. At step S106 the power converters restore supply to the substa tions .

In the example embodiment, steps S101 and S102 are performed by a substation controller local to the fault. Step S103 in volves communication over the first network connection be tween the substation controller local to the fault and the power converter controllers. Step S104 is performed by the power converter controllers. Step S105 is performed in part by the substation controller local to the fault, and the ad jacent substation controller after communication there be tween over the second network connection, and by the associ ated circuit breakers at these substations. Step S106 is performed by the power converter controllers.

As will be appreciated, by communicating fault conditions over the first network connection to the power converters, a rapid response that is effective across the range of possible fault locations can be made, and the associated reduction in operation of circuit breakers on load eases mainte

nance/increases reliability of the protection system.

Attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by refer ence .

All of the features disclosed in this specification (includ ing any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclu sive .

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or simi lar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one ex ample only of a generic series of equivalent or similar fea tures .

The invention is not restricted to the details of the forego ing embodiment ( s ) . The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings) , or to any novel one, or any novel combination, of the steps of any method or process so disclosed.