ELECTRICITY SUPPLY MONITORING SYSTEM

Abstract: A system for monitoring the quality of electricity supply in an electricity supply network, the system comprising: a plurality of means for monitoring the quality at associated locations on the network, each means for monitoring being arranged to provide time stamped electricity quality data for the associated location; and means for correlating the time stamped electricity quality data provided by the means for monitoring to identify related changes in the electricity quality at different locations.

Description: Electricity Supply Monitoring System Field of the invention The present invention relates broadly to a system for monitoring electricity supply. Background of the invention As illustrated in Figure 1, an electricity supply network 10 can be divided into three major sections, namely a transmission section 12, a distribution section 14 and a mains section 16. The network 10 further includes a generation unit 13, suitable transformer units 15, 17, and consumers 20. From a technical viewpoint, the transmission section 12 of the network 10 involves high voltage signals (HV) , normally > 66kV. Within the distribution section 14, medium voltages (MV) , for example 11 kV, and in the mains section 16, low voltages (LV) , eg. 240 V are involved. Events that affect the "quality" of electricity supply include e.g. faults on electricity distribution cables or lines and faults in devices connected to electricity lines which can both e.g. result in the disruption of electricity supply. The disruption may eg. either be rectified by resetting protective devices such as fuses or circuit breakers within the electricity supply network or which may in fact require actual repair works to re-establish the electricity supply. Another event that effects the quality of electricity supply is commonly referred to as a "dip (or sag)", which is a temporary loss /reduction of voltage which typically lasts for less than 20 cycles of the electricity supply signal. The identification and the locating of such events is an important aspect of maintaining an electricity supply network. Issues associated with the occurrence of such events include e.g. liability questions, i.e. is the provider liable for losses/damages which resulted from the events, and the issue of identifying the actual "cause" event where "secondary" events occurred, e.g. where protective devices within the network were triggered and consequently electricity disrupted due to a fault current caused by e.g. a tree falling onto an overhead electricity distribution line at a remote location. To assist in the maintenance of electricity supply networks, systems have been introduced to monitor the quality of the electricity supply at the consumer location, e.g. at a household. If the consumer reports e.g. the occurrence of a dip, a Retailer of the electricity supply can verify the complaint through accessing the monitor data from that household. Such systems are, however, limited to the recording only of events at the consumer location. As another development to improve the maintenance of the electricity supply networks, some fault detectors and power quality monitors within the distribution or transmission sector of the network can transmit signals to a central system for centralised recording to facilitate the remote identification of the occurrence of events. Again, this development is limited to the recording only of events . Summary of the Invention In accordance with a first aspect of the present invention there is provided a system for monitoring the quality of electricity supply in an electricity supply network, the system comprising a plurality of means for monitoring the quality at associated locations on the network, each means for monitoring being arranged to provide time stamped electricity quality data for the associated location; and means for correlating the time stamped electricity quality data provided by the means for monitoring to identify related changes in the electricity quality at different locations. Accordingly, the maintenance of the electricity supply network can preferably be greatly assisted by providing means for automatically identifying related changes in the electricity quality at different locations. In one embodiment, the plurality of means for monitoring comprises a first group at locations within a transmission section of the network, and a second group at locations within a distribution section of the network. Preferably, the plurality of means for monitoring also comprises a third group at consumer locations within the mains network. According to the above described embodiments, the system can identify related changes in the electricity quality across the "boundaries" within the network. This can have the advantage of for example providing a means to identify whether e.g. a change in the quality of the electricity supply reported at a consumer location is correlated with changes in the quality of the electricity supply in an associated portion of the transmission or distribution section. This information can be used to e.g. make a determination as to what party is liable for incurred losses as a result of the change in the quality of the electricity supply. Preferably, the means for correlating the time stamped electricity quality data is arranged to identify a cause event, being a change in the electricity quality at one of the associated locations which has caused the occurrence of secondary events, being changes in the electricity quality at other associated locations . Advantageously, the time stamped electricity quality data comprises at least one of the group of FAULT CURRENT RATIOS, CYCLES OF FAULT CURRENT, and HARMONIC RATIOS. Preferred forms of the invention will now be described, by way of example only, with reference to the accompanying drawings . Brief Description of the Drawings Figure 1 is a schematic diagram illustrating a typical electricity supply network. Figure 2 is a schematic diagram illustrating a system for monitoring the quality of electricity supply embodying the present invention. Figure 3 is a schematic diagram illustrating one component of the system of Figure 2 in more detail. Detailed Description of the Preferred Embodiments In Figure 2, the system 30 comprises a plurality of HV fault detectors 32 and a plurality of HV electricity quality monitors 34 at different locations throughout a transmission section 36 and a plurality of MV fault detectors 33and MV electricity quality monitors 35 throughout a distribution section 38 of a electricity supply network. The system 30 further comprises a plurality of low voltage electricity quality monitors 42 at consumer locations 44 of the network 40. Each of the high voltage fault detectors 32, high voltage quality monitors 34, medium voltage fault detectors 33, medium voltage quality monitors 35 and low voltage quality monitors 42 transmits measured electricity quality data to a central computer system 54. The transmission of the electricity quality data is established through suitable transmission technologies, for example utilising wireless telecommunication networks 46, 48 or wired telecommunication networks 50. Turning now to Figure 3, the computer system 54 stores the received quality data in a first database 60. The computer system 54 is arranged to identify changes in the quality data received from the individual high and medium voltage fault detectors, high, medium and low voltage quality monitors (32, 33, 34, 35 and 42 of Figure 2) . If a change is identified, the computer system is arranged to generate an alert signal 62 to alert a user of the computer system 54 to the occurrence of the change. Furthermore, the computer system 54 is arranged to classify the change as being a particular event, eg. a dip or a complete electricity disruption. This information also forms part of the alert signal 62. Also, the computer system 54 is arranged to correlate the particular event with other changes in the electricity quality data received. This may involve the retrieval of previously stored data from the first database 60, (i.e. to identify related changes that occurred at an earlier time than the particular event) and/or the analysis of simultaneously received quality data and/or the analysis of subsequently received quality data, i.e. to relate events which occur at a later time than the particular event. The computer system 54 further comprises a second database 63 for storing correlation reference data. The correlation reference data is utilised by the computer system 54 to correlate a particular event with previous, subsequent, and simultaneous events. The time stamped data stored and utilised for correlation can include FAULT CURRENT RATIOS, CYCLES OF FAULT CURRENT, and HARMONIC RATIOS. Those can be used to determine the locations of multiple faults i.e., where one fault "simultaneously" causes a second or more fault at different locations on the network. It will be appreciated that for multiple faults it would be insufficient to rely on determination of times of a fault only, since the time resolution required to distinguish between events on a time basis only is practically impossible to realise. The correlation reference data may comprise scenario data, being data that provides a particular scenario of correlated events which are associated with a particular type of cause event. The computer system 54 comprises an analysis unit 65 for analysing the electricity quality data (previously stored, simultaneously and subsequently received) on the basis of the correlation reference data. The analysing unit 65 outputs a result 64 to the user of the computer system 54. The correlation of the events may include the identification of "upstream" events which may have caused a particular "downstream" event. Within an electricity supply network typically events at higher voltage (i.e. "upstream") cause events at lower voltages (i.e. "downstream") rather than vice versa. This is because the transformer units 15, 17 (Figure 1) result in a current reduced "transmission" in an "upstream" direction, i.e. towards the higher voltage. The computer system 54 is also arranged to retrieve specific data from the high and medium voltage fault detectors, high, medium and low voltage quality monitors (32, 33, 34, 35 and 42 of Figure 2), either automatically initiated through the analyser unit 65 as part of the analysis of the electricity quality data, or in response to inputs received from the user of the computer system 54 through a user interface 66. The alert signal 62 and the result signal 64 may be communicated by the computer system on screen, through electronic mail (e-mail), fax, voice, the internet or pager messages or any other suitable means . It will be appreciated by a person skilled in the art that numerous variations and/or modifications may be made to the present invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects to be illustrative and not restrictive. For example, the various components of the computer system 54 described above must not be confined to one physical computer system, but one or more of the components may be at remote locations, linked through a centralised computer platform. In the claims that follow and in the summary of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprising" is used in the sense of "including", i.e. the features specified may be associated with further features in various embodiments of the invention.

Claims: The Claims Defining the Invention are as Follows : 1. A system for monitoring the quality of electricity supply in an electricity supply network, the system comprising: a plurality of means for monitoring the quality at associated locations on the network, each means for monitoring being arranged to provide time stamped electricity quality data for the associated location; and means for correlating the time stamped electricity quality data provided by the means for monitoring to identify related changes in the electricity quality at different locations. 2. A system as claimed in claim 1, wherein the plurality of means for monitoring comprises: a first group at locations within a transmission section of the network; and a second group at locations within a distribution section of the network; and a third group at locations within a mains section of the network. 3. A system as claimed in claims 1 or 2 , wherein the plurality of means for monitoring also comprises a third group at consumer locations within the mains network. 4. A system as claimed in any one of the preceding claims, wherein the means for correlating the time stamped electricity quality data is arranged to identify a cause event, being a change in the electricity quality at one of the associated locations which has caused the occurrence of secondary events, being changes in the electricity quality at other associated locations. 5. A system as claimed in any one of the preceding claims, wherein the time stamped electricity quality data comprises at least one of the group of FAULT CURRENT RATIOS, CYCLES OF FAULT CURRENT, and HARMONIC RATIOS.

Inventors: ROBERT ZAGARELLA, ROBERT, ZAGARELLA
Applicants: CHK ENGINEERING PTY LTD, ROBERT ZAGARELLA, ROBERT, ZAGARELLA
Application year: 2000
Main classification: G01R31
IPC codes: G01R31