GENERAL INFORMATION V FIBRE OPTIC TEMPERATURE SENSING

Transcription

1 GENERAL INFORMATION V FIBRE OPTIC TEMPERATURE SENSING

2 AUSENGLABS * Sentor 201 has been developed by an Australian company based in Pennant Hills, Sydney, Australia. Our staff have been developing and applying optical fibre sensors since AusEngLabs* is dedicated to providing you with: Fibre Sensing technology Fibre selection and deployment Business cases C O N TAC T U S S A L E S S A L E A U S E N G L A B S. C O M. A U W W W. A U S E N G L A B S. C O M. A U SENTOR 201 BENEFITS Sentor 201 key benefits include: TECHNOLOGY Sentor 201 includes: Reduced operating costs Better asset management Enhanced critical situation management Improved system knowledge Remote control (Web Enabled) Alarms conveyed by relay closure or . Safety nonconductive sensor Uses standard optical fibre Additional fibre for communications Up to 28,000 temperature points 1

3 A P P L I C AT I O N S Power industry Generators (and auxiliary motors) Generator HV cables Generator transformers HV switch gear Voltage transformers Transmission lines and TX cables Transformers and switchgear HV distribution cable protection (e.g. in cities e.g. Auckland!) Local substations and switch boards Steam turbines life shortened by droplets if too cool. Building systems - fire and security Building wiring, ducts and lighting Air conditioning and energy management, control and supervision Building security and coding systems Building energy management systems Tunnels road and rail Fire detection and management Mining and Quarrying Underground mining equipment Remote sensors Sensors for mining - robot controlled drills, shuttle cars, grabs Foundry/smelting (water cooling) Curing concrete and plastics Construction of bridges and dams Manufacture of large pipes, tanks Avionics In manufacture of composite components Air conditioning Aircraft engines Fire brigades Temperature of burning material, houses, bush etc. 2

4 Rail Temperature of transported stock Wheel bearings Electrical cables and motors Air conditioning Shipping Temperature of goods in hold and containers Fire and security Petrochemical and process industries Fractional columns Reactors, furnaces and boilers Heat exchangers Capacity of storage tanks Industrial energy management Oil and gas Deep well drilling Steam flood Surface condition sensors Corrosion detection Occupational health and safety Mines, air conditioned suits Hazardous areas (intrinsically safe) Bearing condition trains, conveyer systems Agriculture and food industries Dairying Food processing Food packaging transport Dam walls Exotics Synchrotron Fault monitoring Racing cars Human body NASA X33 Military 3

5 F E AT U R E S Sentor 201 key features available on our standard model: Zones fibres are zoned usually according to the monitored asset Alarms max, min or rate of change thresholds for each zone Events response to alarm may be or relay closure Multiple fibre definitions Web enabled remote control and data analysis through browser CUSTOM SYSTEMS Custom systems are developed to suit applications. Customised housings Multiple fibres Alarms/status through relay closures Data interpretation services 4

6 Critical for Life When temperature rises or falls to critical levels in plants, disasters can occur. The result could be fire, explosion, loss of life and plant shutdown affecting the whole business and their communities. The direct losses to any organisation could be huge, but substantial consequential losses may also be incurred. Sentor 201 monitors temperature throughout your plant and raises alarms when temperatures reach pre-set thresholds or exceed nominated rates of rise. Critical for Asset Management Small temperature changes at critical levels will significantly reduce the life of thermally sensitive assets. For example, a transformer operated at 60 C above ambient may have a life of 20 years. Raising the temperature by 8 C could reduce the lifetime to 10 years, and raising the temperature by 16 C could reduce the lifetime to 5 years. Sentor 201 measures temperature conditions and maintains temperature history profiles which can be used to protect the life of your assets and help gauge asset lifetime consumption. 5

7 OPERATION Sentor 201 is a distributed-temperature measuring system. By launching pulses of laser light through optical fibre cable in contact with the objects to be measured, Sentor 201 captures many thousands of temperature measurements each second. Sentor 201 monitors the intensity of the internally reflected return signals to record temperature, and arrival time to record the location. With Sentor 201, a single optical fibre can be used to monitor temperature in multiple locations around your plant. Measurements can be made as close as 160mm apart. However for most applications, one or more metres is usually sufficient. Fibre optic cables may be fitted on installation or retrofitted to most equipment. Sentor 201 may be used for fibre route distances of up to 4,000 metres ADVANTAGES Economy For an application requiring more than 8 temperature measurement locations, Sentor 201 offers substantial savings over typical optical fibre point sensors. Flexibility By changing the pulse characteristics, the number of locations or frequency of readings can be increased or decreased without any physical change to the installation. With appropriate choice of fibre cladding, Sentor 201 can also be used for a very wide range of temperature measuring. Reliability Properly installed, fibre optic cable should provide higher in-service reliability than powder or semiconductor-tipped optic spot sensors or thermocouples. Accuracy If there is any doubt about the location of hot spots, Sentor 201 can be configured to provide much higher quality data to pinpoint the problem. Performance Sentor 201 offers an optimum combination of high sensitivity, high spatial resolution and fast response times. Physical Optical fibres are of small size, low weight, non conductive, corrosion resistant and immune to electromagnetic interference. Strength Optical fibre has high tensile strength and is available with various ruggedised claddings and strength members to suit a range of locations including direct burial underground. ADVANTAGES OVER SPOT SENSORS For an application requiring t=300s with dl=2m and L=3000m a DTS system can be installed for a cost of less than $US30 per point. In multiple point sensing applications, the new DTS system can offer very considerable savings compared with single point sensors. If you need more than a five point system installing an SENTOR 201 could be an economical alternative and may have much higher in-service fibre reliability than powder or semiconductor tipped spot sensors. Moreover if there is uncertainty as to the exact location of the hottest spot, for example in a large transformer, laying a single fibre along all possible paths will provide much higher quality data than could be obtained with a few pre-located spot sensors. 6

8 Temperature C and MVA Aging rate and Cumulative life used C A S E S T U DY OF T R A N S F O R M E R L I F E T I M E The case study reported by Stokes and Tyree illustrates the importance of temperature on asset lifetime. The study was of a hypothetical 40MVA transformer loaded on a sinusoidal basis between 20 and 40MVA over a 24 hour period. Most present day monitoring aims to assist asset management by providing a measurement that can be used to forecast the need for maintenance. A more complete program of asset management would include an estimate of remaining life based on a history of use. From the cumulative distribution it can be seen that virtually all of the 24 hour life is consumed during the 6 hours from 9:00 to 15:00 when the transformer temperature varies from 97.0 to 106.3⁰C and the load changes from to 40MVA MVA Temperature Age rate 20 5 Life used hours Time, hours 0 Transformer temperature and daily life usage (Stokes and Tyree). 7

9 P O W E R C A B L E S In early 1998 a series of power failures occurred in the underground cables providing electricity to the central business district (CBD) of Auckland. As a consequence much of the CBD of Auckland was blacked out for a significant period. It is understood that the loss of power has had a significant impact on the economic activity of Auckland. Inquiry into the Auckland Power Supply Failure: Public Summary 1 In the five weeks it took to restore the power supply, about 60,000 of the 74,000 people who worked in the area worked from home or from relocated offices in the suburbs. Some businesses relocated staff to other New Zealand cities, or even to Australia. The majority of the 6,000 apartment dwellers in the area had to find alternative accommodation. It was estimated that the long-term economic impact equivalent to 0.1 to 0.3 per cent of New Zealand's Gross Domestic Product 2. This disastrous power failure in New Zealand, with consequential costs running into the hundreds of millions of dollars, might have been avoided had a Distributed Temperature Sensor (DTS) been used to monitor for hot spots along the length of the cable. Integral Energy, who conducted the inquiry, stated that for an underground cable to perform to its optimum capacity a routine maintenance program should ideally include monitoring of cable, ambient and soil temperatures. They concluded that Mercury Energy s 110 kv cables had been operating at temperatures above their design limits from an early stage after their commissioning....in fact the rating of these cables was much lower due to the ground conditions in which they were buried. When they were loaded to more than half their nominal rating they would have started to overheat. The Auckland Central Business District Power Failure, The Inquiry And The Lessons, Bryan Leyland Principal, Sinclair Knight Merz, New Zealand and Richard Frantz Managing Director, Merz and McLellan (Pty) Ltd, South Africa, AMEU CONVENTION SEPT 1999 When the replacement cables were installed in December 1998 Olex Cables incorporated a DTS system and, as part of their contract, provide a monthly report on circuit performance to Vector Limited (Mercury s successor) using temperature data from the DTS sampled every two hours and load information from the power company. This continuous monitoring, with data available every 2 m along the cable, has shown that there are certain regions along the 9 km route that are warmer than the average. This may be due to other services crossing the cable route and is under investigation Vector are not going to be caught twice! Critical Circuits DTS Imperative, Barber et al, D2000 Proceedings1999 8

10 DTS systems, such as SENTOR 201, make measurements by detecting and analysing Raman/Stokes backscatter within a fibre-optic cable when pulsed with a laser light source. The intensity of certain reflected frequencies is temperature dependent and time of flight for the returning signal equates to distance along the fibre. Optical fibres can be either built in to the cable when manufactured or attached externally at the time of laying. Power Companies around the World have realised the benefits of Distributed Temperature Sensing. In the UK The National Grid Company has been using DTS systems on selected new EHV cable circuits since In the USA, Commonwealth Edison are adopting fibre-optic temperature sensing for all new 138kV induct underground cables in Chicago and Northern Illinois. DTS systems will give us precise real-time, measured data and allow us to avoid all the variables such as surface temperature, soil moisture and thermal influences. - Linda Manning, ComEd s Asset Management and Planning Vice President. 4 ComEd are also looking at retrofit options for existing key circuits. Other key overseas users of DTS systems for power cable monitoring include Hydro Quebec in Canada and Tokyo Electric in Japan In Australia and New Zealand several Electricity Supply Companies are now specifying fibre-optic sensing cables to be incorporated in new installations. Western Power adopted the SENTOR 101 (predecessor of the SENTOR 201 with externally applied sensing cable for a new 132 kv cable in East Perth. Energy Australia have specified the option of fibre-optic temperature sensing for a new 33 kv cable in Sydney and WEL Energy in Hamilton, NZ are considering DTS for the same voltage. Given the simplicity of adding a sensing cable at the time of installation, and realistic pricing now available for mid range DTS instruments, an increasing number of power cable specifications are calling for fibre-optic sensing down to 11 kv. External sensing cable was installed on 22 and 66 kv underground cables at United Energy s new Dandenong Valley Substation in Melbourne. The effectiveness of this method of temperature sensing can be seen in the annotated screen view from the SENTOR 101 instrument during commissioning tests. Although the cables were very lightly loaded there are very noticeable changes in temperature where they passed through conduits, compared with direct burial in controlled backfill. What is the future for DTS systems in the Electricity Supply Industry? It is clear that fibre-optic sensing cables will be installed in growing numbers as asset managers seek to drive power systems harder and still enjoy a good night s sleep. Real Time Thermal Rating (RTTR) linked to SCADA systems will enable accurate measurement, prediction and control of temperature-critical circuit elements. As well as cable, transformers and switchgear will have embedded fibre-optic sensors for both distributed and point temperature monitoring. Other substation equipment will be linked by a network of optical fibre. For example, Integral Energy located a series of spool sensors to provide quasi point-measurement of temperature around various plant, including low voltage switchboards, at the Penrith substation in Western Sydney. Fire detection is another emerging DTS application. Perhaps one of the most persuasive arguments for adopting Distributed Temperature Sensing is its significant potential to impact positively on insurance premiums and minimise the increasing risk of class action, as well as other types of litigation, arising from failure of supply

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