GB2400246A

GB2400246A - Monitoring partial discharge events in gas insulated substations

Info

Publication number: GB2400246A
Application number: GB0406227A
Authority: GB
Inventors: Brian Hampton; John Pearson
Original assignee: Diagnostic Monitoring Systems Ltd
Current assignee: Diagnostic Monitoring Systems Ltd
Priority date: 2003-03-19
Filing date: 2004-03-19
Publication date: 2004-10-06
Also published as: GB0306282D0; GB0406227D0; WO2004083878A1

Abstract

Each integrated processing unit 20 receives a signal from a UHF coupler 11, analyses it to detect partial discharge events and accordingly outputs a notification signal to a databus 12 via a link 15 and a hub 14. Each hub 14 receives signals from several processing units 20 and transmits them to a local control unit 40 which is in turn connected to a control centre. Processing unit 20 includes digitising circuitry 21 and a microprocessor 22. Processing unit 20 may include algorithms to reject interference signals and the parameters analysed may include signal count, signal spacing, and statistical pulse or pattern deviation. The processing unit 20 and coupler 11 may be in a housing (fig 3, 30) situated on chambers of a gas insulated substation (fig 4, 38) and may include an LED display indicating the presence of a partial discharge event. Local control unit 40 may perform further analysis on data received from processor unit 20 by comparing it with data corresponding to known fault conditions.

Description

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1 Improved System for Monitoring Electrical Components 3 The present invention relates to the field of monitoring 4 electrical components, and more particularly to monitoring partial discharge events in electrical 6 components.

8 Gas insulated substations (GIS) are vital items of plant 9 in the electrical power systems of developed and developing countries. GIS are utilised in many 11 electricity transmission networks because of their very 12 compact size. In a GIS, the conductors and circuit 13 devices, such as instrument transformers and switchgear, 14 are housed within pressure vessels containing an atmosphere of sulphur hexafluoride at elevated pressure.

16 The pressure vessels are typically made of aluminium and 17 electrically are held at earth potential. In a 3-phase 18 network, the conductors of the individual phases are 19 separately encased in pressure vessels and are mechanically mounted therein via insulators. The 21 pressure vessels typically comprise interconnected 22 tubular members which may have side wall inspection 23 ports.

ce. 46: I.: À À . . . . À: ÀI:.: :: À . G 2 2 Fault conditions which arise in the GIS lead to lengthy 3 disconnection periods due to the mechanical complexity of 4 the GIS, and there is therefore a requirement to provide diagnostic measurements in service use of the GIS in 6 order to predict the possibility of a fault condition and 7 to enable corrective action at a planned and convenient 8 time. These potential faults almost always show partial 9 electrical discharge activity before breakdown occurs, and this discharge activity can be sensed from the 11 consequential ultra-high frequency (UHF) resonant modes 12 established in the pressure vessels. Accordingly, the 13 UHF modes can be sensed by couplers built into the 14 pressure vessels at the inspection ports, combined with the use of a spectrum analyser connected to the coupler 16 output and human interpretation of the analyser result.

18 The electricity supply network in developed countries is 19 divided broadly into transmission and distribution systems. The most economic design of an overhead line 21 (or underground cable) to carry a certain load is to use 22 its optimum voltage/current ratio. In other words, if a 23 line needs to carry more power, then both its rated 24 voltage and rated current need to be increased.

Transmission systems are the backbone of the network and 26 often operate at 400kV and either 275kV or 230kV. Below 27 this, the distribution systems operate typically at 28 132kV, 66kV, 33kV and llkV. The interchange between 29 these voltage levels occurs at substations that are increasingly of the GIS type. All power transmitted by a 31 400kV substation passes through every other substation 32 along the chain, and since at each interchange the 33 current and voltage both decreases, the number of act.À ee: Àe: À c: À. . 1 substations at lower voltages increases very 2 approximately as the square of the voltage ratio. For 3 example, we would expect to need 36 GIS at 66kV for every 4 one at 400kV. In practice, as it is the number of switchgear bays that increases, there may be as many as 6 96 GIS at 66kV for two at 400kV. Also in practice the 7 66kV GIS are physically as large the 400kV GIS.

9 Electricity consumers such as semiconductor manufacturers who are supplied directly at 66kV distribution voltages 11 need a very stable supply of electricity because even 12 minor dips in voltage can cause their plant to 13 malfunction.

Typically electricity suppliers monitor the transmission 16 voltage GIS. However, any plant breakdown, even at 17 distribution voltage GIS, causes a dip in the power in 18 the supply voltage over much of the network.

19 Furthermore, distribution voltage transformers have been known to explode, so catching fire and causing extensive 21 damage to the substation.

23 UHF monitoring can be used wherever the defect is 24 enclosed in a metallic housing, because it is this enclosed space that resonates and gives the UHF signal 26 picked up by the couplers. In this respect, a 27 distribution voltage network comprising 66kV GIS is no 28 different from any other, except that the total number of 29 couplers needed for all the substations would be large.

Furthermore, other low voltage components which are large 31 in number in distribution networks, such as 33kV cable 32 terminations, are enclosed in aluminium compartments that À . c. c. . c c c. c À À À c: À c 1 would support UHF resonances which are therefore suitable 2 for monitoring by such diagnostic systems.

4 In the prior art, systems are known which are suitable for application to monitoring of transmission voltage 6 GIS.

8 US Patent No 5396180 to the University of Strathclyde 9 describes a diagnostic measuring system for GIS, comprising means for automatically monitoring a plurality 11 of UHF couplers, and communicating data representing the 12 detection signals to an analysing means which carries out 13 the appropriate analysis and characterization of the 14 signal.

16 US Patent No 5982181 to Hitachi Limited describes an 17 insulation device diagnosing system which prepares 18 detection data from the partial discharge signal, such 19 that periodic elements are given to a plurality of specific frequencies of the partial discharge signal.

21 The deterioration lifetime and the kind and extent of 22 abnormality of the insulated device are judged from the 23 pattern and intensity of the spectral distribution.

US Patent No 6239723 to Siemens AG describes an 26 encapsulated installation at high or medium voltage, 27 including a plurality of sensors located within the 28 interior of an encapsulation. The surface acoustic wave 29 (SAW) sensors are monitored by wireless communication from outside the encapsulated installation. The sensors 31 can be interrogated selectively. À

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1 The problem with applying the known systems for 2 diagnostic measurements of GIS to the large number of 3 substations in a distribution network is the large amount 4 of data generated by the detection system. This data is typically transmitted across a communication network, 6 analysed centrally, and the results need expert 7 interpretation.

9 Figure 1 shows a monitoring system for a gas insulated substation (GIS) according to US Patent No 5396180, 11 generally depicted at 10. The system includes a 12 plurality of couplers 11 for detecting UHF signals from 13 inside combustion chambers of the GIS. The couplers are 14 connected to units 21, which contain circuits for signal amplification, level detection and timing of the pulse.

16 The units also digitise the outputs of the couplers 11 17 and transfer the data to a host computer 25 via a loop 18 network 13.

Host computer 25 is used to store the coupler data for

21 analysis. The prior art system as described is

22 essentially a two-stage process. Unit 21 transmits 23 characterized data via network loop 13, and host computer 24 performs the analysis necessary to determine whether a partial discharge event has occurred. The partial 26 discharge information can then be transmitted to an 27 engineer at a remote location 27 via any suitable data 28 transmission means. Here, the data will often be 29 analysed further by the engineer or by an expert system in order to gain additional information on the nature and 31 location of the defect. .

eer a a a eca 1 The system will generally comprise twenty to thirty 2 three-phase sets of couplers and therefore twenty to 3 thirty units 21, each transmitting information on the 4 characterized signal into the network 13. Within a GIS, this represents a large amount of data transmitted across 6 the network. Inside the noisy environment of a GIS, 7 these data are prone to interference, and are therefore 8 typically transmitted by an optical fibre network.

The system described in US 5396180 is not suitable for 11 implementation across a distribution network due to the 12 high expense involved in installing such a system. In 13 addition, the amount of data generated would be difficult 14 to handle.

16 It would be advantageous to provide a system suitable for 17 monitoring a large number of GIS and other components at 18 distribution voltages which avoided the generation of 19 large amounts of data and also provided status reporting in a manner easily understood. Furthermore, it would be 21 advantageous to provide a system simple enough to be 22 installed and maintained by local agents.

24 It is an object of the present invention to provide a monitoring system which can monitor a large number of GIS 26 or other components and transmit a small amount of data 27 about the status of the GIS or other components through 28 the communication network.

According to a first aspect of the present invention, 31 there is provided an integrated processing unit for use 32 in an electrical component monitoring system, the 33 integrated processing unit comprising: À À À . . a À a a À À - 1 receiving means for receiving a signal from a UHF 2 detector; 3 analysing means for analyzing the received signal and 4 determining if the received signal corresponds to a partial discharge event; 6 means for generating a notification signal in the event 7 that the received signal corresponds to a partial 8 discharge event.

The integrated processing unit may comprise means for 11 transmitting the notification signal to a local control 12 unit.

14 Preferably, the analysing means is adapted to distinguish a received signal corresponding to a partial discharge 16 event from a received interference signal.

18 Preferably, the analysing means is a CPU running a 19 software module, the software module analyzing one or parameters of the received signal, the parameters 21 selected from the group consisting of: signal count, 22 signal spacing, statistical pulse, and pattern deviation.

24 More preferably, the software module further comprises a noise suppression algorithm.

27 The means for transmitting a notification signal may be a 28 switch operable to act on a pair of wires connected to 29 the local control unit.

31 Preferably, the means for transmitting a notification 32 signal is a two-way data link. : t:

À À .: . À À - 1 More preferably, the integrated processing unit further 2 comprises a housing, wherein the UHF detector is a 3 coupler partially enclosed by said housing.

Preferably, the integrated processing unit comprises an 6 input means adapted to receive an input signal from an 7 auxiliary UHF detector.

9 The integrated processing unit further may comprise a visible display to indicate the presence of a partial 11 discharge event.

13 Preferably, the integrated processing unit is adapted to 14 transmit a signature of the received signal to a local control unit when a partial discharge event is 16 identified.

18 According to a second aspect of the invention, there is 19 provided a system for monitoring electrical components, said system comprising a plurality of integrated 21 processing units according to the any preceding Claim.

23 The system may further comprise a plurality of UHF 24 detectors for detecting UHF radiation and providing detection signals to the integrated processing units.

27 Preferably, one UHF detector is provided for each 28 integrated processing unit.

Preferably, the system further comprises a local control 31 unit configured to receive notification signals from a 32 plurality of integrated processing units. À 1

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1 The local control unit may comprise a memory device 2 storing data representative of known fault conditions, 3 and a comparator for comparing a signature signal from an 4 integrated processing unit with known fault conditions.

6 Preferably, the system further comprises a control 7 centre, remote from the integrated processing units and 8 local control unit, connected to the local control unit 9 by a communications link and adapted to receive a second notification signal from a local control unit.

12 The control centre may be provided with a display for 13 indicating the status of the local control unit.

Preferably, the system is adapted to monitor Gas 16 Insulated Substations (GIS), each GIS having a local 17 control unit and a plurality of integrated processing 18 units.

According to a third aspect of the invention there is 21 provided a method for monitoring electrical components, 22 the method comprising the steps of: 23 i) detecting a UHF signal using a UHF coupler; 24 ii) analysing said signal in order to distinguish a detected signal corresponding to a partial discharge 26 event from a detected interference signal; 27 iii) generating a notification signal indicative of a 28 partial discharge event; 29 iv) transmitting the notification signal to a location remote from the UHF coupler.

32 Preferably, steps (ii) and (iii) are carried out by a 33 single integrated processing unit.

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2 Step (iv) may comprise the sub-steps of (a) transmitting 3 a first notification signal to a local control unit, 4 local to the UHF coupler, and (b) transmitting a second notification signal to the location remote from the UHF 6 coupler.

8 The method may comprise the step of transmitting a 9 signature of a received signal to the local control unit.

11 Preferably, the method comprises the additional step of 12 comparing the signature of the received signal with data 13 corresponding to known fault conditions, thereby 14 determining the most likely cause of the partial discharge event.

17 In order to provide a better understanding of the present 18 invention, an example will now be described by way of 19 example only and with reference to the accompanying Figures, in which: 22 Figure 1 illustrates a block diagram of the system

23 according to the prior art;

Figure 2 illustrates a block diagram of the system 26 according to an embodiment of the invention; 28 Figure 3 illustrates an integrated processing unit 29 according to an embodiment of the invention.

31 Figure 4 shows a monitoring system according to an 32 embodiment of the invention.

Àe it: .'t: . . À' : Àe it: 1 Figure 5 illustrates an example of a simple front end 2 display in the control centre; 4 Figure 6 illustrates the circuit diagram of an integrated processing unit according to an embodiment of the 6 invention; 8 Figure 7 illustrates the circuit diagram of an integrated 9 processing unit according to an alternative embodiment of the invention; 12 Figure 2 shows a schematic diagram of a monitoring system 13 according to an embodiment of the invention. The system 14 includes the plurality of couplers 11, connected to integrated processing units 20. Each integrated 16 processing unit (IPU) is connected to a databus 12 via a 17 hub 14. Hub 14 receives input signals from several IPUs 18 20, via links 15, and is connected by the databus 12 to a 19 local control unit 40. The local control unit 40 is in turn connected to control centre 27. Databus 12 is for 21 example a multicore cable. Hub 14 is not an essential 22 part of the system, but provides a convenient cabling 23 solution and allows each IPU to be addressed individually 24 by the local control unit 40.

26 Couplers 11 detect UHF signals, and transmit the 27 detection signal to the integrated processing units 20.

28 The detection signals are received by processing unit 20, 29 which contains analysing means 21, 22 for determining whether the detected signal corresponds to a partial 31 discharge event or is due to an external source of 32 interference.

:: .:e i:ai 1 Analysing means contains circuitry 21 for digitizing the 2 signal, as well as a microprocessor 22 which analyses the 3 signal in order to determine whether a real partial 4 discharge has occurred. The microprocessor runs a software module that includes algorithms to analyse the 6 parameters of the received signal. The parameters 7 analysed are selected from the signal count, the signal 8 spacing, and the statistical pulse or pattern deviation.

9 The software module also runs a noise rejection algorithm.

12 The IPU may then transmit a simple "yes" or "no" message 13 to the local control unit 40, depending on whether or not 14 the partial discharge (PD) event has occurred. The local control unit 40 is linked to a control centre 27 where an 16 engineer may monitor its activity.

18 A key advantage of the system is the reduction in the 19 amount of data transmitted through the system. By providing an integrated unit that characterizes and 21 analyses the detection pulse in situ, the transmission of 22 large amounts of data associated with the detection pulse 23 is avoided.

There will now be described an example embodiment of a 26 practical implementation of the monitoring system, with 27 reference to Figures 3 to 6. Figure 3 shows an IPU 20 28 contained in a housing 30. The housing is also provided 29 with an LED display 31, reset module 36, power input 32 and coupler 11. The housing 30 is mounted on chambers of 31 the GIS 38, as shown in Figure 4. A connection 35 32 functions as a control link from the local control unit 33 40 to the IPU.

sac.d ee.: c À cc c À cc 2 The housing 30 is mounted such that the coupler is on 3 dielectric apertures in the chambers such as the exposed 4 edges of the cast resin support barriers or glass observation windows.

7 When a defect is present, the dielectric apertures in the 8 GIS chambers pass UHF signals that are picked up by the 9 couplers. The signal from the coupler is analysed within the processing unit 20, and in the presence of a defect a 11 notification signal is transmitted via switch 34. In 12 this embodiment, each IPU is associated with one UHF 13 coupler 11.

The notification signal is provided by the internal 16 switch 34 which operates on a pair of wires connected to 17 local control unit. Thus the output signal from the unit 18 is a simple one, merely showing that the internal switch 19 34 is open or closed.

21 LED display 31 is also provided within the housing. The 22 LED display shows the status of the internal switch and 23 hence indicates whether a fault condition is present 24 within the GIS. Resetting module 36 is also provided for resetting the unit to the "no-fault" condition.

27 The notification signal from the individual integrated 28 processing units is transmitted via cable 12 to a local 29 control unit 40 as shown in Figure 4. The local control unit incorporates the power supply, which is typically AC 31 at a low voltage. The power supply cable would typically 32 be a screened multi-core cable.

dl: And: C 3 À , 3 , 1 In addition, the local control unit 40 incorporates means 2 for determining the status of the switches within the 3 IPUs. The local control unit is optionally provided with 4 one or more indicating devices to show information on the current status of the internal switches within the IPUs.

6 For example, the level control unit may display whether 7 the internal switch in any IPU is open or closed, or the 8 local control unit may indicate the status of a 9 particular IPU. Alternatively, the local control unit may indicate which IPUs have internal switches in the 11 closed position.

13 Further functional circuitry is also optionally provided 14 within the local control unit. For example, means for automatically testing the IPUs at preset intervals, or 16 resetting the IPUs to the no-fault condition are 17 included. Such control signals are provided via control 18 link 35.

In an alternative embodiment, the monitoring system of 21 the invention utilizes internal couplers provided within 22 the chambers of the GIS. In this case, the couplers are 23 connected to the IPUs via coaxial cables.

The information on the status of the internal switches in 26 the IPUs is transmitted from the local control unit to a 27 remote control centre by SCADA. This control centre may 28 monitor a large number of GIS systems and contains a PC 29 and a monitor. Software running on the PC gives an alarm when an internal switch within an IPU is closed. The 31 particular GIS containing that IPU is identified, and an 32 operator in the control centre can instruct an engineer 33 to attend to the GIS with the fault condition. In a more l.

À À .; l 1 sophisticated embodiment, the PC can optionally provide 2 the operator, via the local control unit, with additional 3 information such as the particular IPU with the fault 4 condition. The alarm within the control centre is cancelled when the internal switch of the IPU is reset, 6 by a command from the local control unit to the reset 7 module running on the IPU. All of the data received in 8 the remote control centre from the various local control 9 units is recorded.

11 Figure 5 shows a simple form of display 50 provided by 12 the software running on the PC in the control centre.

13 The left-hand side contains a list 51 of the GIS 14 monitored by the system. Each GIS has an array 52 of indicators 53 to display the status of the GIS over a 16 recent period of time. An indicator of one colour (say 17 green) indicates that no fault conditions were detected 18 within the GIS on that particular day. An indicator of a 19 second colour (say red) indicates to the operator that a fault condition existed in that particular GIS on a 21 particular day. This display allows the history of the 22 GIS to be instantly displayed in a clear and concise 23 manner. The display is for example a Microsoft Windows 24 based software application.

26 In a more sophisticated embodiment, the operator has the 27 option to call up further information on the fault from 28 the local control units. For example, data on the time 29 of the fault, or the approximate location of the fault may be displayed.

32 In addition to the reset function implemented by a 33 specific command to the reset module 36 from the local : .: À À .. :e 1 control unit 40, the system can be configured so that the 2 switches are reset to the no-fault condition at a set 3 time. This reset function may be configured within the 4 processor inside the housing, or alternatively can be implemented in the local control unit. The automatic 6 reset prevents a temporary fault from being displayed on 7 consecutive days. That is, a persistent fault can be 8 distinguished from a short-lived one.

Optionally, when the display indicates a fault to the 11 operator, the IPU reset function can be activated from 12 the control centre, so that the display is set back to 13 the green no fault condition. If the discharge is still 14 active, the display will return to red, and the operator can instruct an engineer to attend the site. This 16 mechanism provides a means for checking the operation of 17 the system. Such an embodiment requires a more 18 sophisticated communications link between the remote 19 control centre and the local control units at the GIS, such as an RS232 connection.

22 When the engineer arrives at the GIS he or she must 23 determine which coupler has detected a fault. This 24 information can be provided by an operator who has accessed the data from local control unit 40 in advance.

26 Alternatively, the engineer may gain the information from 27 the local control unit himself. When the active coupler 28 is located, the engineer connects a portable UHF monitor 29 to the coupler. The portable device is provided with a mobile telephone capable of relaying data back to the 31 control centre for more detailed analysis.

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I: À i: :: À 1 Figure 6 shows the circuitry of the integrated processing 2 unit in more detail.

4 The UHF coupler 11 transmits the detection signal to a filter 61, which is typically a band pass filter chosen 6 to transmit only the UHF signals of interest. The output 7 of the filter 61 is delivered to amplifier 62. Power 8 supply from the local control unit is shown by 32.

A combination of the signal detector 63 and the signal 11 peak detector 64 provide information on the peak of the 12 pulse, the width of the pulse and the point-on-wave time 13 of events with respect to a 50 Hz reference signal.

This information is digitized by the ADC 65 within micro 16 controller 60. The digitised data are then accessed by 17 processor 66 for analysis. The processor runs a software 18 module including a series of algorithms for analyzing 19 various parameters of the signal, including the signal count, the signal spacing, and the statistical pulse or 21 pattern deviation. The software module also runs a noise 22 rejection algorithm. Additional protection circuitry may 23 be provided to avoid damage created by large discharge 24 spikes. The software module may be updated via input 68.

26 The above-described embodiment allows transmission of a 27 simple notification signal to a local control unit 40 via 28 output 69. A more sophisticated embodiment includes the 29 capability for additional, more detailed characterization of the detected signal. In this example, if a partial 31 discharge event is identified, a sample or signature of 32 the signal will be transmitted to the local control unit 33 40 for further analysis.

::e le. ate:e À:. ace À À 2 Different types of partial discharge event produce 3 different UHF signals with different pulse signatures.

4 The local control unit comprises memory, storing data representative of known fault conditions. A comparator 6 compares the signature signal with known fault 7 conditions, and is able to determine the most likely 8 cause of the detected signal.

For this example, the data transfer system between the 11 IPUs and the local control unit must be capable of 12 allowing additional information to be transmitted to the 13 local control unit. Optionally, some or all of this 14 information can be transmitted to the control centre.

For example, if required, the characterizing parameters 16 of the pulse signature may be transmitted across a 17 network, or information on the type of discharge event 18 that has occurred can be provided to an operator at the 19 control centre. However, in the preferred embodiment, a simple notification that a fault has been identified at a 21 particular GIS is transmitted to the remote control 22 centre via a SCADA communications link.

24 An alternative circuit diagram is shown in Figure 7. In this embodiment, the tuned filter 71 is provided so that 26 measurements can be made in a part of the spectrum that 27 is free from external interference. The signals are then 28 amplified by amplification circuits 72. The remainder of 29 the circuitry works in the same way as the embodiment of Figure 6, other than the transmission of the warning 31 signal. In this embodiment a "Bluetooth" transceiver 32 73 is provided within the integrated processing unit for 33 communicating the warning signal. The local control unit Àe ce: .: À À a. : ee. ee: 1 is also provided with Bluetooth transceiver. By 2 providing the Bluetooth transceivers, wireless 3 communication between the local control unit and the IPU 4 is possible. In addition, wireless communication is possible between the local control unit and the portable 6 device carried by an investigating engineer, or between 7 the IPU and such a mobile device directly.

9 The local control unit can also be used to update the IPUs with new software for analysing of detected pulses.

12 In practice, an engineer dispatched to the relevant site 13 is able to obtain extra information on the discharge 14 event by accessing the Bluetooth 0 transceiver with a portable unit. This information can be obtained from the 16 local control unit or directly from the IPUs Bluetooth 17 transceiver itself. This would avoid the need for 18 physically connecting the coupler or local control unit 19 to the portable device during detailed fault investigation.

22 It is evident that many modifications could be made to 23 the described system within the scope of the invention.

24 Such modifications include changes to the data transmission systems,the detector circuitry, the display 26 systems and the power supply, and would be obvious to one 27 skilled in the art.

29 The present invention offers numerous advantages over the

prior art systems as follows:

32 By providing an integrated unit for identifying a partial 33 discharge event by analyzing the detected signal, the ee. .. be: add: À À À À: . À ... . 1 physical structure of the system is simplified. The one 2 piece unit is cheaply produced, easily distributed and 3 readily installed in the GIS. Significantly, the units 4 may be retro-fitted to GIS.

6 By analysing the signal in si tu it is possible to reduce 7 the amount of data that is transmitted through the 8 network as a matter of course, thereby enabling larger 9 numbers of GIS to be monitored. The invention is therefore particularly suitable for monitoring GIS and 11 other plant equipment at distribution levels.

13 The systems described provide an operator with a lucid 14 display of the statuses of a large number of GIS, complete with defect history. No expert analysis is 16 necessary at the control centre, and therefore the 17 operator need not be skilled in interpreting partial 18 discharge information.

In the non-fault condition, the display provides the user 21 with a degree of assurance by virtue of the positive 22 indication of the status of a GIS when no fault is 23 present.

Indicators on the local control units and the IPUs 26 themselves indicate the presence of a defect to an 27 investigating engineer, and direct the engineer to the 28 approximate location of the fault.

More sophisticated embodiments allow additional 31 information on the type of partial discharge event to be 32 transmitted on an ad hoc basis.

ace e. a&: ees: À À .: À . . 1 Although the foregoing description relates to GIS, the 2 claimed invention in its various aspects is suitable for 3 monitoring other electrical systems, including power and 4 instrument transformers, bushings, cable terminations and switch gear.

7 Further modifications may be made within the scope of the 8 invention herein intended.

Claims

ee' .. ce: ace: ee. c'. .: c.e:e 1 Claims 3 1. An integrated processing

unit for use in an 4 electrical component monitoring system, the integrated processing unit comprising: 6 (i) receiving means for receiving a signal from 7 a UHF detector; 8 (ii) analysing means for analyzing the received 9 signal and determining if the received signal corresponds to a partial discharge 11 event; 12 (iii) means for generating a notification signal 13 in the event that the received signal 14 corresponds to a partial discharge event.

16 2. The integrated processing unit as claimed in Claim 17 1 comprising means for transmitting the 18 notification signal to a local control unit.

3. The integrated processing unit as claimed in Claim 21 1 or Claim 2 wherein the analysing means is adapted 22 to distinguish a received signal corresponding to a 23 partial discharge event from a received 24 interference signal.

26 4. The integrated processing unit as claimed in Claim 27 3 wherein the analysing means is a CPU running a 28 software module, the software module analysing one 29 or parameters of the received signal, the parameters selected from the group consisting of: 31 signal count, signal spacing, statistical pulse, 32 and pattern deviation. À

::e.e es. V:. e.e:e À 1 5. The integrated processing unit as claimed in Claim 2 4 wherein the software module further comprises a 3 noise suppression algorithm.

6. The integrated processing unit as claimed in any 6 preceding Claim wherein the means for transmitting 7 a notification signal is a switch operable to act 8 on a pair of wires connected to the local control 9 unit.

11 7. The integrated processing unit as claimed in any 12 preceding Claim wherein the means for transmitting 13 a notification signal is a two-way data link.

8. The integrated processing unit as claimed in any 16 preceding Claim further comprising a housing, 17 wherein the UHF detector is a coupler partially 18 enclosed by said housing.

9. The integrated processing unit as claimed in any of 21 Claims 1 to 7 wherein the integrated processing 22 unit comprises an input means adapted to receive an 23 input signal from an auxiliary UHF detector.

10. The integrated processing unit as claimed in any 26 preceding Claim further comprising a visible 27 display to indicate the presence of a partial 28 discharge event.

11. The integrated processing unit as claimed in any 31 preceding Claim adapted to transmit a signature of 32 the received signal to a local control unit when a 33 partial discharge event is identified.

À - .- @e c: Àe À. À. À: ... :. À . 24 1

2 12. A system for monitoring electrical components, said 3 system comprising a plurality of integrated 4 processing units according to the any preceding Claim.

7 13. The system as claimed in Claim 12, further 8 comprising a plurality of UHF detectors for 9 detecting UHF radiation and providing detection signals to the integrated processing units.

12 14. The system as claimed in Claim 12 or Claim 13, 13 wherein one UHF detector is provided for each 14 integrated processing unit.

16 15. The system as claimed in any of Claims 12 to 14, 17 further comprising a local control unit configured 18 to receive notification signals from a plurality of 19 integrated processing units.

21 16. The system as claimed in any of Claim 15, wherein 22 the local control unit comprises a memory device 23 storing data representative of known fault 24 conditions, and a comparator for comparing a signature signal from an integrated processing unit 26 with known fault conditions.

28 17. The system as claimed in Claim 15 or Claim 16, 29 further comprising a control centre, remote from the integrated processing units and local control 31 unit, connected to the local control unit by a 32 communications link and adapted to receive a second 33 notification signal from a local control unit.

-: it: . :: ce a' 'c: A: .: : À À . À 2 18. The system as claimed in any of Claims 12 to 17 3 wherein the control centre is provided with a 4 display for indicating the status of the local control unit.

7 19. The system as claimed in any of Claims 12 to 18, 8 adapted to monitor Gas Insulated Substations (GIS), 9 each GIS having a local control unit and a plurality of integrated processing units.

12 20. A method for monitoring electrical components, the 13 method comprising the steps of: 14 (i) detecting a UHF signal using a UHF coupler; (ii) analysing said signal in order to distinguish 16 a detected signal corresponding to a partial 17 discharge event from a detected interference 18 signal; 19 (iii) generating a notification signal indicative of a partial discharge event; 21 (iv) transmitting the notification signal to a 22 location remote from the UHF coupler.

24 21. The method as claimed in Claim 20 wherein steps (ii) and (iii) are carried out by a single 26 integrated processing unit.

28 22. The method as claimed in Claim 20 or Claim 21 29 wherein step (iv) comprises the sub-steps of (a) transmitting a first notification signal to a local 31 control unit, local to the UHF coupler, and (b) 32 transmitting a second notification signal to the 33 location remote from the UHF coupler.

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2 23. The method as claimed in any of Claims 20 to 22 3 further comprising the step of transmitting a 4 signature of a received signal to the local control unit.

7 24. The method as claimed in Claim 23 comprising the 8 additional step of comparing the signature of the 9 received signal with data corresponding to known fault conditions, thereby determining the most 11 likely cause of the partial discharge event.