Report. Evaluation of Performance of AXCES and EXCEL Cable at the Shetland Test Site

Transcription

1 EA TECNOLOGY Report Evaluation of Performance of AXCES and EXCEL Cable at Authors: J B Wareing and A S Ward Report No: Project No: C071/21 October 1999 "adding value by developing and deploying innovative technologies"

2 Project No: C071/21 Evaluation of Performance of AXCES and EXCEL Cable at Client(s) Ericsson Cables AB EA Technology Ltd October 1999 EA Technology Limited, Capenhurst, Chester, C1 6ES; Tel: Fax: ; Registered in England number

3 EA TECNOLOGY by J B Wareing and A S Ward Summary AXCES and two EXCEL type cables manufactured by Ericsson Cable AB, of Sweden, were erected at the Susetter ill, Shetland test site in March 199 and taken down in September, 1999 at the end of their scheduled test period. They were monitored by load cells and video cameras and performed extremely well. In the Shetland Isles the standard span length used in the 11 and 33 kv network is around 60 m. The Ericssons cables were strung up on an elevated position on spans up to 90 m. They have withstood 1 months of operation, the only failure being on the foundations of the terminal poles which failed in late Spring, The poles were re-erected so that the tests could continue. Visual examination of the cables showed that there had been no slippage at the helical fittings during the test period. There was some abrasion on one support fitting and the cable but this was due to the terminal pole failure which pulled the fitting out of it s correct position. There was no indication of galloping or vibration throughout the period, nor any indication of any significant snow or ice loading.

4 Contents Page,1752'&7,21 *QUDO 6KWODQG 6FRSRIWKLVUSRUW 7+(&$%/(6 $;&(6DQG(;&(/ )LWWLQJV 66(77(5+,//7(676,7( *QUDO 7K6XVWWU+LOO7VW6LW6KWODQG Location Weather Site Layout Tests 5 0RQLWRULQJ(TXLSPQW Video Systems Load Cells Meteorological Data Accelerometers Data Capture Systems Vibration Recorders Cabling the Site 9 $;&(6(;&(/7(676 *QUDO :DWKUFRQGLWLRQV /RDGFOOGDWD 7\SLFDO5VXOWV 600$5< 5(&200(1'$7,216

5 1 Introduction 1.1 General Three samples of cable manufactured by Ericsson of Sweden have been installed at the Susetter ill Test Site, Shetland over the past eighteen months. the cables were strung on 60 and 90 m spans and monitored by load cells and dedicated video cameras. Meteorological conditions are also monitored. Also strung at the site were bare copper conductor and various types of XLPE covered conductor, including the Amo Kraft type, also manufactured in Sweden. 1.2 Shetland Shetland is situated 220 km north of the Scottish mainland and is subject to severe winds and salt pollution. It also suffers from high current positive lightning with strikes commonly in excess of 0 ka. In half of the weeks within the testing period of the AXCES/EXCEL winds reached the storm force 10 range (Beaufort scale: 4-55 knots, mph) on a 10 minute running average basis. In early November, 199 and twice during February, 1999, the wind exceeded hurricane force 12 (Beaufort scale: >64 knots, >73 mph), reaching a maximum (10 minute average) speed of 2 knots (94 mph) in early February at temperatures around 0 to - 3 C in blizzard conditions. 1.3 Scope of this report This report covers briefly the characteristics of the AXCES and EXCEL (12 and 24 kv) cable and details of the test site. Some examples of the data collected are given in this the body of the report. The full load and meteorological data is included in CD format with this report. The original video footage has been send periodically to Ericssons during the test period. The final two tapes are also included with this report. The report concludes with a review of the performance of the AXCES and EXCEL cable over the test period and how relevant this is to normal UK conditions. Recommendations are also given as to how the use of this type of cable may be encouraged in the UK utilities. 2 The Cables 2.1 AXCES and EXCEL AXCES is a three core 14/24 kv 95 m m2 stranded aluminium conductor with an earth shield and insulating sheath. It is intended for use underground, underwater and overhead. It is attached to wood poles using hanging metal supports with rubber inserts (Figure A1) similar to LV ABC, commonly used throughout the UK. At terminal poles small crossarms are used (Figure A2). A sample of AXCES has also been strung for demonstration purposes at EA Technology, Capenhurst Chester for the last 1 months. 1 of 15

6 EXCEL is a three core 7/12 and 14/24 kv 10 m m2 copper conductor with an earth shield and insulating sheath. It has been tested at Shetland in the 12 kv and 24 kv versions. As AXCES, it is intended for underground, underwater and overhead use. It is attached to the wood poles using a metal/nylon roller type assembly with a rubber insert. It has also been strung for demonstration purposes at EA Technology. All three conductors were strung on successive spans of 90, 90 and 60 m at the Shetland site (Figure A6). 2.2 Fittings The conductors were held with helical dead ends at both terminal poles (Figure A3) and also at a section pole to accommodate the load cells (Figure A4). The load cells monitored tension on all three conductors on the central 90m span. 3 Susetter ill Test Site 3.1 General The test site is situated at latitude in the north mainland of Shetland. It is approximately at the same latitude as the Ericssons plant at Falun in Sweden. The site was established in September 1996 to compliment other EA Technology test site facilities at Green Lowther (West Scotland) and Deadwater Fell (Kielder, England). The main purposes of the three sites were testing of conductors under different weather regimes: Green Lowther : Deadwater Fell : Susetter ill : Severe icing, strong winds. eight 695m One 0m test span. Two test rigs. Up to 6 conductors can be tested at one time Test span 200m which can be configured to various spans of typically 90/110m up to 12 conductors can be tested at one time. Test rig also present.. Wet Snow and Rime Ice. Strong winds. eight 590m igh salt pollution, severe winds, snow/ice. eight 170m. Live facilities to 11kv. 21 test spans normally at 90m length arranged in 6 rows, up to 21 conductors can be tested at one time. The test rigs consist of frames containing up to 7 one metre samples of conductor, mounted on a 6.5m pole that rotates into the wind. Close-up video monitoring of snow/ice growth is available. Meteorological conditions are monitored at all sites. Two short videos are enclosed with this report. One covers the Susetter ill site, including the monitoring facilities. the other is an older video which covers the test rigs and spans at the Green Lowther and Deadwater Fell sites. 2 of 15

7 0 D QÃ'D LO\ Ã:LQG V S G ÃD QG Ã'LU F W LR Q EA Technology 3.2 The Susetter ill Test Site, Shetland Location Susetter ill is a flat topped hill, 170 m high, near Sullom Voe on the North Shetland mainland. It is within 2 km of the North Sea and the Atlantic Ocean. The site presently covers an area of 300 m by 150 m with a further area available for expansion. It is totally unmanned Weather The Green Lowther and Deadwater Fell test sites were chosen primarily for the frequent wet snow and severe icing incidents. The Shetland site also suffers wet snow blizzards but only moderate icing. It has, however, the highest wind speeds in the UK. Storm force winds (10-12 on Beaufort scale) are not uncommon and since the establishment of the site the highest wind speed recorded was 145 mph. Due to its island status and openness to winds from the North Sea and Atlantic Ocean the salt pollution level is also the highest in the UK. Its Northerly position also gives it the highest UV levels in the UK. Figure 3.1 shows the mean daily wind speed at the site during the 1996/97 winter : 90 : 270 Q 6: WLR F 6 LU 10 Ã' G LQ 6( : ( 90 1( Windspeed (knots) /02/97 02/02/97 26/01/97 19/01/97 12/01/97 05/01/97 27/12/96 19/12/96 11/12/96 04/12/96 27/11/96 20/11/96 13/11/96 06/11/96 30/10/96 21/10/96 13/10/96 06/10/96 29/09/96 22/09/96 Wind Direction Windspeed Figure 3.1 The mean daily windspeed at the Susetter ill site, Shetland Site Layout Due to the severe weather experienced in the Shetland Isles, the normal overhead line construction is based on a basic span at 11 kv of 60 m and pole heights of 7 m above ground. Wind stays are in widespread use. In order to stress the poles and equipment at the site a basic 90 m span was used with pole heights m above ground. Poles under test were not stayed. The site is intended to be flexible and continually changeable. It consists basically of five lines of 3 spans and one of 2 spans (Figures 3.2 and 3.3). This last line is due to be extended 3 of 15

8 to 3 spans in February, 199. It is designed so that the lines may be linked into one continuous 1.4 km line with one spur or a short line with six spurs or any combination inbetween. It is connected to the 11 kv main line via a recloser at its South West corner (pole 17) and has a transformer at its North East corner (pole 4). Due to the requirements of the various contracts, as at January, 1995 the site is connected as a 1.2 km live line at 11 kv with one live 3-span spur and one "dead" 3 span spur. Figure 3.2 The Shetland field site All the lines are at present of 3-phase horizontal construction except for one spur which is 3- phase but has no crossarms. Twelve spans are strung with 50 mm 2 XLPE covered conductors, three spans with bare copper conductor and three spans with a Swedish "aerial cable" conductor with OL/cable junctions. 4 of 15

9 Figure 3.3 Schematic of the Shetland site Tests As has been mentioned, the site is designed to be flexible and is continually being changed as results come in and the trials are assessed. One aim at present is to test covered conductors intended for 11 and 33 kv use, although future tests may include covered conductor trials to 132 kv. The conductors used also include various anti-vibrational and anti-galloping devices as well as a full range of lightning protection systems. Novel lightning protection systems are also under test. A full range of insulators (porcelain, composite, polymer concrete etc.) are also under trial. These are being tested with conventional and novel conductor fixing techniques. Crossarms under test include the standard and narrow construction designs in steel and composite forms and also the "no crossarm" constructions. Wood poles are compared with composite poles in equivalent medium and stout type and different foundation methods. The severe weather conditions have led to several failures of conductors, crossarms and poles, but also to several successes, where new equipment is proving more reliable than the conventional route. To test to destruction, however, is not the main aim. The purpose of the site is to monitor the performance of the components under test under a variety of weather conditions. The next section deals with the monitoring facilities. 5 of 15

10 3.3 Monitoring Equipment Video Systems At the Shetland site, the techniques developed at the other sites were again set up and extended to allow not only automatic but computer controlled remote operation. Video cameras are set up on several "observation" poles on the site to give general views at different angles of the spans and poles. Cameras are also mounted on the terminal poles and set so as to closely monitor conductor movements. The cameras have a high low light level sensitivity (down to 0.01 lux) and are also sensitive to wavelengths in the near infra red. Thus, night time viewing is achieved by using infra red floods which illuminate the site for the cameras but which give very little visible light. The site, therefore, does not disturb the local population or attract undue attention at night. The cameras are all set to record in time lapse mode 24 hr/day and to automatically record in "real time" for 3 seconds every 30 to 60 minutes. Two of the cameras have additional recorders which are set to record in real time in specified weather conditions. Typically the cameras may be set to be recorded in real time for 1 minute when wind speeds exceed 60 knots from a particular range of wind directions when the temperature is between certain set limits. After any such computer controlled recording period, the recorder will not record for a further set period of, say, one hour, so as to preserve tape usage. The amount of tape left can be determined by simply phoning up the site and the computer set parameters can also be changed in this way. In addition, the weather and site behaviour can be monitored visually and data-wise by video telemetry from Capenhurst. If, in assessing the situation, more video recording is required, then a simple mouse operation will set the recorder into instant "real time" or other mode of recording. The computer control and logging system is detailed in section Load Cells Load cells are installed on specified conductors throughout the site. The output is recorded at a specified rate (normally one every 10 minutes) at which the maximum, minimum and average values over the previous time period are logged. The logging rate is automatically switched to a higher rate (say, every 0.1 sec) according to set meteorological parameters in similar fashion, to the video camera control. The "fast log" data is recorded in separate files than the "normal" logged data and transmitted to Capenhurst over a phone link Meteorological Data Wind speed and direction, temperature and humidity are monitored under the same conditions as the load cells. Indeed, if any sensor is called on to record at a higher rate, the meteorological data is automatically recorded at that same rate Accelerometers Accelerometers are mounted on poles and crossarms under test. The computer calculated the movement of the crossarm tips and pole tops based on the accelerometer data. igh speed data (up to 150 z) is monitored from all the accelerometers at the same time in order for 6 of 15

11 both quantitative and comparative movement to be evaluated. This method allowed a direct comparison of the on-site performance of the composite poles and crossarms compared with the conventional wood poles and steel crossarms Data Capture Systems The video data is recorded on-site and can also be viewed by telemetry on standard phone lines from Capenhurst. All other data is logged by an on-site computer which not only records the data but also analyses it in order to change the sensor recording modes as required. Figure 3.1 shows the layout as represented by a schematic display on the computer screen with the instantaneous outputs of the load cells and accelerometers shown at the appropriate pole number (Figure 3.2). The wind speed and direction are shown numerically and graphically as circular dials and compass points (Figure 3.6). The current humidity and temperature values are shown in both bar and digital format. Finally, the amount of tape usage in the computer controlled video recorders is shown. The operational buttons shown on the screen can be operated by the mouse to start and stop the recorders manually/remotely. Figure 3.1 Schematic layout of the site Figure 3.2 Computer screen showing monitoring system In the data display mode only the instantaneous values of each sensor is shown. owever, by clicking on the appropriate sensor button, the variation of the sensor output over a specific 7 of 15

12 period can be displayed (Figure 3.3). In the case of the accelerometers, the output against frequency up to 150 z can also be displayed. Figure 3.3 Sensor output Figure 3.4 Sensor selection for output display At the top of the screen (Figure 3.4) the logging rates can be displayed and altered as required. Figure 3.5 shows the drop-down display to set the standard acquisition rate and a faster rate under certain specified conditions. The historical logged data can also be downloaded in its normal and fast-logging rate files. of 15

13 Figure 3.5 Logging rates display Figure 3.6 Meteorological data display Vibration Recorders Figure 3.7 Drop-down display to set video automatic operation parameters As has been mentioned, the site is flexible and is continually being changed according to the various clients wishes. The computer display can be modified easily to include new poles or other equipment to be tested in the future and any additional sensors on present poles. As load cells are switched to different conductors, the display is altered to show this Cabling the Site The various sensors have different outputs. All poles with sensors have conditioning boards which change the sensor output to a 4-20 ma loop. The signals are then sent via the surface cabling network to the portacabin which contains the video recorders, computer, data-logging 9 of 15

14 and telemetry equipment. As a security feature the cabin has its own security cameras which are both recorded continuously and can be viewed at any time from Capenhurst. 4 AXCES/EXCEL Tests 4.1 General The AXCES and EXCEL cables were strung on two 90m and one 60m span at the Susetter ill site in March, 199 on two terminal, one intermediate and one section pole. A dedicated video camera was set up on the section pole looking down and north along the 90m span (Figure A4). A further two video cameras, already present on the site, were orientated to view the 90 and 60m spans from the West side. All the camera outputs were recorded in time lapse format with 3 second bursts of real twine video every 40 minutes. Under these parameters the 3 hour VS tapes give 7 weeks coverage of the test site. All three conductors were monitored by load cells at the section pole. The stringing was performed by Scottish ydro Electric linesmen supervised by Lam Effraimson and Per Dahlberg of Ericssons and EA Technology personnel. The Ericssons personnel also installed the helical fittings (Figure A5). 4.2 Weather conditions Temperature, wind speed and wind direction were monitored and presented in graphical format in periods of one week on the enclosed CD. umidity data is also available if required. 4.3 Load cell data The tensions on all three conductors are recorded every 15 minutes. The data is again presented graphically in periods of one week on the enclosed CD. 4.4 Typical Results Basically the cables were very stable and the tensions varied very little, even in the severest weather conditions. Figure 4.1 shows the tensions soon after installation when the first storm force winds were encountered. The weather data is shown in Figure of 15

15 1 Excel12kV N Ã Q R L V Q 7 EA Technology &DEO/RDGVZN Max kn Excel24kV Max kn Axces Max kn /03/ 9 31/03/ 9 01/04/ 9 02/04/ 9 03/04/ 9 04/04/ 9 05/04/ 9 05/04/ 9 'DW Figure 4.1 Cable tensions in the first week of installation 6XVWWU+LOO:DWKU'DWDZN Ã G LQ ÃÃ: Ã& U WX U D S P WV Q 30 Ã. G 20 S V V U J ÃG Q WLR F LU ' Temperature Wind Speed Wind Dir. 30/03/9 31/03/9 01/04/9 01/04/9 02/04/9 03/04/9 04/04/9 04/04/9 05/04/9 'DW Figure 4.2 Weather data accompanying Figure 4.1 Figures 4.3 and 4.4 show the load cell and weather data under storm force 11 conditions (62 knots, 71 mph) in January, 1999, ten months after installation. 11 of 15

16 1 Excel12kV N Ã Q R L V Q 7 EA Technology &DEO/RDGVZN Max kn Excel24kV Max kn Axces Max kn /10/9 22/10/9 22/10/9 23/10/9 23/10/9 23/10/9 23/10/9 24/10/9 24/10/9 24/10/9 24/10/9 24/10/9 25/10/9 25/10/9 25/10/9 25/10/9 'DW Figure 4.3 Cable tensions in January XVWWU+LOO:DWKU'DWDZN Ã G LQ S P ÃÃ: WV 3 Ã& Q U Ã. G2 WX U D S V /10/9 23/10/9 23/10/9 23/10/9 24/10/9 24/10/9 25/10/9 25/10/9 25/10/ V U J ÃG Q WLR F LU ' Temperature Wind Speed Wind Dir. 'DW Figure 4.4 Weather data for late January, The full data is given on the enclosed CD. 5. Summary The AXCES and both EXCEL cables performed very well. In the Shetland Isles the standard span length used in the 11 and 33 kv network is around 60 m. The Ericssons cables were strung up on an elevated position on spans up to 90 m (Figure A6). They have withstood 1 months of operation, the only failure being on the foundations of the terminal poles which failed in late Spring, These were re-erected and the test continued. Metallurgical tests are being carried out by Ericssons and are not the subject of this report. owever, visual examination of the cables showed that there had been no slippage at the helical fittings during 12 of 15

17 the test period. There was some abrasion on one support fitting and the cable but this was due to the terminal pole failure which pulled the fitting out of it s correct position. There was no indication of galloping or vibration throughout the period. Indeed, the cable video pictures were boringly stable! There was no indication of any significant snow or ice loading. This is not surprising as the shape of the cables will tend to avoid accreting loads due to wind flow effects. In this instance it is similar in performance to LV ABC. 6. Recommendations The tests at the Shetland site have indicated that the AXCES and EXCEL cables will be very capable of handling the weather conditions suffered by the overhead line network in the UK. The fittings used also performed perfectly adequately with no visible problems. The cables can therefore be recommended for use in the UK wherever the current network is established. Electrically, the optimum size for UK networks may fall between the two sizes on test here. If it is intended that these conductors be used to replace old copper lines or to refurbish lines at present using Rabbit (50 mm² ACSR) or azel (59 mm² AAAC) conductor, then sag/tension values and pole strength will have to be considered. It is recommended therefore that an intermediate size of cable be considered and that it be strung in direct comparison to these aluminium conductors. In this way wind and ice loadings as well as creep can be directly compared. If these suggested tests were successful then this type of cable could have good potential within the UK. 13 of 15

18 Appendix I Figure A1 The cables attached to wood poles using hanging metal supports with rubber inserts i

19 Figure A2 The short crossarm used to support the AXCES cable. ii

20 Figure A3 elical dead ends at a terminal pole. Figure A4 elical dead ends at the intermediate pole. The dedicated video camera is also visible. iii

21 Figure A5 Installion of the helical fittings Figure A6 General view of the cables at Susetter ill. iv