GB2266419A

GB2266419A - Electrical power supply

Info

Publication number: GB2266419A
Application number: GB9208755A
Authority: GB
Inventors: Shlomo Scop
Original assignee: Motorola Israel Ltd
Current assignee: Motorola Solutions Israel Ltd
Priority date: 1992-04-23
Filing date: 1992-04-23
Publication date: 1993-10-27
Also published as: GB9208755D0

Abstract

An electrical power system (10) for routing an electrical current (I) comprises a plurality of fault sensing devices (24) responsive to the system (10), and at least one remote unit (RTU1-RTUn) coupled to the system (10). A satellite global positioning system (12, 14, 16), associated with each of the remote units (RTU1-RTUn), provides a synchronised timing signal. Each of the remote units (RTU1-RTUn) has at least one of the fault sensing devices (24) coupled to it, and the detection of a fault (26, 38, 40, 42) within the system (10), as registered by a fault sensing device (24), causes a remote unit (RTU1) coupled to the device to register a time (T1, T2, T3), obtained form the satellite system (12, 14, 16). The time tagging arrangement enables tracking and location of a fault by comparison of the times logged. <IMAGE>

Description

An Electrical Power Svstem.

Background to the Invention.

This invention relates, in general, to an electrical power system and is particularly, but not exclusively, applicable to accurate time synchronization between such sites therein and time tagging and event logging within such a system.

Summarv of the Prior Art, In an electrical power distribution system, such as a national electrical power grid, there are many application in which a user requires an absolute time synchronization between distinct and remotely located sites. One such application is the accurate time tagging of the occurrence of events at a single site, such as a transformer station or a generating station, and the relationship of these events to other events occurring at different sites within the system. A time tagging regime is particularly suited to the tracking and identification of a fault within an electrical network.

Present time tagging technology achieves synchronization between remote sites through a simultaneously radio transmission of a signal from a central control unit to each remote site Unfortunately, such a synchronisation technique provides a time resolution of -10 milliseconds which is insufficient to ascertain in what chronological order the events have occurred within the system, how the events have spread and to subsequently conclude what caused the events. In order to obtain the desirable benefit of fault identification through the use of time tagging, the time resolution must be increased to a resolution of better than elms.

Clearly, there is a requirement within the art to provide a time tagging methodology with both a high resolution and a high synchronisation and which has the ability to identify and track a fault within a system.

Summarv of the Invention.

This invention addresses at least some deficiencies which prevail in the prior art described above. In accordance with a preferred embodiment of the present invention there is provided an electrical power system for routing an electrical current. The electrical power system comprises at least one remote unit coupled to said system, a plurality of fault sensing devices responsive to said system and a satellite global positioning system (GPS). The satellite positioning system is associated with each of the at least one remote units and provides a synchronised timing signal thereto.Each of the at least one remote units has at least one of said plurality of fault sensing devices coupled thereto and the detection of a fault within the system, as registered by a fault device, causes a remote unit coupled to said device to register a time, obtained from said satellite system, of said detection of the fault.

In the preferred embodiment of the present invention, the electrical power system further comprises a control unit responsive to the at least one remote unit. Furthermore, each of the at least one remote units further comprises a transceiver. Moreover, a remote unit, which registers the detection of a fault, transmits, to said control unit, both said time of said detection and an identity which uniquely identifies the unit from which a transmission emanates. In a further embodiment, the control unit further comprises reception means for receiving a plurality of times which each represent a time of the detection of a fault by a fault sensing device and comparison means for comparing said plurality of times.

The control means subsequently estimates a location for the fault by ascertaining from said comparison means an earliest time for the detection of said fault and identifying the corresponding fault sensing device from which said earliest time emanated. In the preferred embodiment, the fault sensing device are circuit breakers and the remote unit comprise part of a supervisory control and data acquisition system. Moreover, the electrical power system may be electrical power grid.

An exemplary embodiment of the invention will now be described with reference to the accompanying drawings.

Brief Description of the Drawings.

Fig. 1 is a preferred embodiment of an electrical power system in accordance with the present invention.

Fig. 2 is an alternative embodiment of the electrical power system of Fig. 1.

Fig. 3 illustrates a control unit suitable for implemetation with the present invention.

Detailed Description of a Preferred Embodiment.

Figs. 1 and 2 illustrate two alternative embodiments of the present invention. With reference to Fig. 1, a plurality of remote units RTUl-RTUn are coupled, in series, to an electrical power system, such as a national electrical grid, which supplies an electrical current I. These remote units RTUl-RTUn may be remote data acquisition and control units which monitor and control the electrical power system. Each remote unit is coupled to a Global Positioning System (GPS) comprising a GPS receiver 12 and a satellite receiver 14. The GPS system is responsive to a geo-stationary satellite 16 which simultaneously provides an accurate time stamp, via the satellite receivers 14, to all GPS receivers 12 in the electrical power system 10. Synchronisation of all the remote units RTUI-RTUn is therefore achieved.Each remote unit in the electrical power system 10 further comprises a transceiver 20 for communicating information to and receiving information from a base station 22. It will be appreciated that the communication link between the remote units RTU1 -RTUn and the base station 22 may be a radio communications link, as illustrated in Fig. 1, or any other suitable form of communication link as would be apparent to one skilled in the art e.g. a land-line. A plurality of fault sensing devices 24 are coupled to and interspersed within the electrical system 10.

Implementation of the present invention is accomplished through the unique coupling of a GPS receiver 12 to a remote unit RTUl-RTUn via an RS232 connector. Furthermore, a pin on the GPS receiver 12 provides a synchronised time pulse to the remote unit.

When a fault 26 occurs within the electrical power system 10, such as a fault 26 generated by a surge in electrical current I, a lightning strike to the electrical system 10 or the grouding thereof, a fault sensing device 24, such as a circuit breaker, register the fault and causes an event logger 28, contained within each remote unit RTU1-RTUn, to register the exact time of the occurrence of the fault 26.The GPS system provides a resolution of 105 nano-seconds which is sufficient to differentiate between fault registration at different remote units RTU1-RTUn. Typically, if a fault 26 occurs between remote units RTU1 and RTU2, the sudden lose of current I to remote units RTU2 and onwards toward RTUn will consecutively trigger the detection of faults, as detected by the plurality of fault sensing devices 24 and recorded by each event logger 28 associated therewith, at each of the remote units RTU2 to RTUn. In the preferred embodiment, the time of the occurrence T1, T2, Tn of the fault 26, as detected by each event logger 28, is transmitted to the base station 22 via the radio communication link. Moreover, each remote unit RTUl-RTUn also transmits a pre-assigned address which uniquely identifies itself within the system. From the transmitted information, the base station compiles a chronological table of results and, consequentially, estimates the location of the fault and provides an analysis of how the fault 26 has spread throughout the electrical system 10. Clearly, time T1 is the earliest recorded time of the detection of a fault and time Tn, representing a detected time of the occurrence of the fault by a subsequent remote unit furthest from the fault 26, is the latest time. An alternative embodiment of the present invention would allow for the registration of the time of the detection of the fault in, for example, a non-volatile memory located within each remote unit RTU1-RTUn. The value recorded in the memory could subsequently be accessed by a service engineer.

Fig. 2 illustrates a further embodiment of the present invention A remote unit RTU1 comprises a transceiver 20, for communicating with a base station 22, and an event logger 28. The remote unit RTU1 is responsive to an accurate and synchronised time signal provided by a GPS system. Furthermore, the remote unit RTU1 is coupled to an electrical power system 10. A plurality of electrical components 32-36, such as transformers, provide a plurality of output currents I. Each one of the plurality of electrical components 32-36 is coupled to the event logger 28. A sub-station 30 is coupled at an intermediate stage between the plurality of electrical components 32-36 and the electrical power system 10. A plurality of fault sensing devices 24, such as circuit breakers, are coupled to and interspersed within the electrical system 10.

If, for example, a major fault develops at the sub-station, a plurality of secondary faults 38, 40, 42 may occur within the electrical power system. Each one of the plurality of secondary faults 38, 40, 42 is detected by a fault sensing device 24 and the time of the occurrence of each of the plurality of faults T1, T2, T3 is registered by the event logger 28 in terms of the synchronised time signal provided by the GPS system. The remote unit RTU1 transmits, to the base station 22, the time of the occurrence of each of the plurality of faults T1, T2, T3 and a unique identifying address. The base station 22 then compiles a chronological table of events and analyses the received information in order to establish the pattern in which the plurality of faults 38, 40, 42 occurred.

Fig. 3 illustrates a suitable base station 22 which may be implemented in the present invention. The base station 22 comprises a transceiver or receiver 44 for for receiving information relating to the occurrence of at least one fault and processing means 46, such as a microprocessor, for analysing received information and compiling a chronological table of events therefrom.

It can be appreciated that the implementation of such as invention provides the novel advantages of a relatively inexpensive time tagging methodology with both a high time resolution and a high time synchronisation. Moreover, such an invention provides the desirable ability to identify and accurately track a fault generated within a system. In addition, the ability to quickly locate such a fault within a system, such as one which occurs within a national electrical power grid, yields the advantages of reduced service and repair time therefor.

Claims

Claims,

1. An electrical power system (10) for routing an electrical current (I) comprising: a) at least one remote unit (RTUl-RTUn) coupled to said system (10); b) a plurality of fault sensing devices (24) responsive to said system (10); and c) a satellite global positioning system (12, 14, 16), associated with each of the at least one remote units (RTU1 -RTUn), for providing a synchronised timing signal thereto;; wherein each of the at least one remote units (RTUl-RTUn) has at least one of said plurality of fault sensing devices (24) coupled thereto and the detection of a fault (26, 38, 40, 42) within the system, as registered by a fault sensing device (24), causes a remote unit (RTU1) coupled to said device (24) to register a time (T1, T2, T3), obtained from said satellite system (12, 14, 16), of said detection of the fault (26, 38, 40, 42).

2. An electrical power system (10) in accordance with claim 1, further comprising: a) a control unit (22) responsive to the at least one remote unit (RTUl-RTUn); and b) each of the at least one remote units (RTUl-RTUn) further comprises a transceiver (20); wherein a remote unit (RTU1), which registers the detection of a fault (26, 38, 40, 42), transmits, to said control unit (22), both said time (T1, T2, T3) of said detection and an identity which uniquely identifies the unit (RTU1) from which a transmission emanates.

3. An electrical power system (10) in accordance with claim 2, wherein the control unit (22) further comprises: a) reception means (44) for receiving a plurality of times (T1, T2, T3) which each represent a time of the detection of a fault (26, 38, 40, 42) by a fault sensing device (24); and b) comparison means (46) for comparing said plurality of times (T1, T2, T3); wherein the control means (22) estimates a location for the fault (26, 38, 40, 42) by ascertaining from said comparison means (46) an earliest time (T1) for the detection of said fault (26, 38, 40, 42) and identifying the corresponding fault sensing device (24) from which said earliest time (T1) emanated.

4. An electrical power system (10) in accordance with any preceding claim, wherein the at least one remote unit (RTUi RTUn) comprises part of a supervisory control and data acquisition system which maintains control for said electrical power system (10).

5. An electrical power system (10) in accordance with any preceding claim, wherein the fault sensing device (24) is a circuit breaker.

6. An electrical power system (10) in accordance with any preceding claim, wherein the electrical power system (10) is an electrical power grid.

7. A system (10) comprising: a) at least one remote data acquisition and control unit (RTUl-RTUn), coupled to said system for the control thereof, having an input; b) a plurality of sensing devices (24) responsive to said system (10); and c) a satellite global positioning system (12, 14, 16), associated with each of the at least one remote units (RTUl-RTUn) for providing a synchronised timing signal thereto;; wherein each of the at least one remote units (RTUl-RTUn) has at least one of said plurality of sensing devices (24) coupled to said input thereof and the detection of an event (26, 38, 40, 42) within the system, as registered by a sensing device (24), causes a remote unit (RTU1) coupled to said device (24) to register a time (T1, T2, T3), obtained from said satellite system (12, 14, 16), of said detection of the event (26, 38, 40, 42).

8. A method for detecting the location of a fault (26, 27, 28) within an electrical power system (10) comprising the steps of: a) providing a synchronised time signal, from a satellite global positioning system (12, 14, 16), to at least one remote unit (RTUl-RTUn) coupled to said electrical power system (10); b) detecting a time (T1, T2, T3) at which at least one fault sensing device (24) within the electrical power system (10) identifies that a fault (26, 38, 40, 42) has occurred within said electrical power system (10); wherein said time (T1, T2, T3) is determined by said satellite system (12, 14, 16).

9. A method in accordance with claim 8, wherein the method further comprises the steps of: c) transmitting information, from the at least one remote unit (RTUl-RTUn) comprising: i) a plurality of times (T1, T2, T3) which represent the registration of a fault (26, 38, 40, 42) at a plurality of fault sensing devices (24); and ii) a unique address which identifies said remote unit (RTU 1) from which said information emanates; d) receiving said information at a control unit (22) responsive to said remote unit (RTU1); e) comparing said times received from the at least one remote unit (RTUl-RTUn); and f) chronologically arranging said times, whereby: i) an earliest time (T1) of registration of a fault (24) is identified; and ii) a remote unit (RTU1) from which a transmission containing said earliest time (T1) is identified

10. A method of fault detection substantially as described herein and with reference to Figs. 1, 2 and 3 of the accompanying drawings.

11. An electrical power system substantially as described herein and with reference to Figs. 1, 2 and 3 of the accompanying drawings.