Application and Use of Distributed Temperature Sensing (DTS) Technology in Transmission Cables Dr. Sudhakar Cherukupalli Principal Engineer, Team Lead, Transmission Cables Transmission Engineering, BC Hydro Presentation at LABORA 2017 Oct 31, 2017 Hydro October 31, 2017
OVERVIEW What is distributed fiber sensing DTS/DSS/DAS Some basics advantages/challenges Cable types/installation and placement of optical fibres relative to the power cable pros and cons Synopsis of 20-year history with DTS usage at our utility with case studies How can a System operator use the information to operate the cable assets? 2
Principle of Distributed Temperature Sensing System LIGHT Source (LED or LASER) Optical Multiplexer LAN Cable LAN Cable Fiber pig-tails Distance Fusion splices CPU Photo detectors Rayleigh light Scattering Intensity anti-stokes component Stokes Component `` 3 λ 0- λ Wavelength λ 0+ λ
4 Animation of the OFDR based DTS system
5 Using Fibre to Measure Strain and Temperature for Structure Health Monitoring
Strain Gauges Versus Optical Monitoring Application for Strain Measurements Using Fibre Bragg Gratings - Shape Forming 6
Power Cables Some types and installations 7
Overseas Submarine power Cables Largest Rating 2200MW Deepest 1650m Longest length 580 km 8
Examples of Cables installed in bridge Inside box girder Exterior 9
Cable Types by Insulation o o Paper/Oil Insulated Cable o SCFF - Self-contained Fluid Filled Cable (~ 6 bars) o HPFF - High Pressure Fluid Filled Pipe Type Cable (~ 14 bars) o MI Mass-impregnated Solid Type Cable: PILC Cable, DC Cable o Gas Filled Cables: Single Conductor Cable, High Pressure Pipe Type Cable. Extruded Insulation Cables o XLPE - Cross-Linked Polyethylene Cable o PE Polyethylene o EPR - Ethylene propylene rubber 10
Commonly Used Conductor Types for HV Transmission Cables o SCFF Cables Concentric strand o XLPE Cables Concentric Self Supporting strand Milliken Milliken Type Type 11
Typical cross-section of the Vancouver City Central Transmission (XLPE) Cable with embedded fibres Conductor and Insulation shields Copper Conductor Embedded optical fiber XLPE Insulation Aluminum Sheath Polyethylene jacket 12
Cable plants in India, Korea and three new plants in North America since 2010 Southwire 13
Quality Assurance Factory acceptance testing Examples of routine Electrical Tests: o o o o Capacitance, Resistance measurements AC and Partial discharge tests Jacket DC withstand test Fibre Optic cable test 14
Ductbank Construction Trench Cut & Cover 230kV Cable Project 15
Cable Pulling on Dunsmuir St.
HV Cable Joints/Terminations
How we harnessed this technology to help integrate into Smart Grid 18
History of DTS usage at BC Hydro Started a pilot R&D demonstration project in 1992 with a DTS System Applied the technology to monitor a 69kV Cable corridor in downtown Vancouver and discovered the impact of a steam line Applied the technology to monitor a 230kV High Pressure Fluid-Filled cable corridor in 1998 Applied a real-time dynamic rating system to monitor several transmission cable circuits with EPRI collaboration in 1999 In 2000, applied a DTS system to monitor seepage in an earthen Dam Installed over 12 systems monitoring 230-500kV cable system on our network 19
20 Schematic Arrangement of Placement of FO Cable
21 Physical Examples on Land and Submarine Cables
Case Study 1 Retrofit on 525kV AC Submarine Cable 22
Schematic of Two 525kV,1200MW Cable Circuits 23
525kV Cable Terminations A view from the top! 24
25 525 kv Cable Cross-section
Submarine Cables/Cooling Pipes in Concrete Chase Return pipe Cable chase HV cable Coolant pipe 26
RTDs on Cable and Coolant Pipes 525kV Cable in chase Foam-glass insulation Coolant pipes 27
FO Splice Enclosure and CTS Stainless steel encased fiber 525kV Optical downlink CTS to measure cable and armor currents 28
Case Study 2 Application along a distribution cable corridor 29
30 2014 CYMCAP STUDY RESULTS
Results from 2014 Study A full duct bank (45 cables) in isolation has a ratings of about 215A to 230A and considering the influence of the adjacent duct banks if loaded will limit the duct bank to a cable rating to between 181-194A (15%; reduction) At the section A-A location, this equates to 168MVA at 12kV for the 3 duct banks combined. Selecting a lower Tr i.e., better soil improves the ratings by about 15%. At the section A-A location, this equates to 193MVA at 12kV for the 3 duct banks combined. This prompted the consideration to use a DTS system and take soil samples for thermal resistivity measurements 31
Schematic of the feeder cable egress out of a station 32
Distribution feeder cables in a manhole about 90m from the DTS location in the control room 33
MH 2251 (103 to 147) MH 2523 (285 to 312) Hamilton St MH 3799 (459 to ) Section A-A 2L20 MH 2255 (182 to 207) 14" Steam Pipe DTS Trace along the FO cable 100 90 Fiber Temperatures From station to MH 3799 80 70 7-16-15 10:39 11-1-15 11:00 11-9-15 0:40 8-29-15 0:10 7-16-16 10:40 Nov 09, 2015 = 81.9 Nov 1, 2015 = 67.8 60 50 40 30 July 16, 2015 = 35.5 Inside Stn Aug 29, 2015 = 35.2 20 10 0 0 100 200 300 400 500 34
Comparison of FEM result with DTS data Tempearture along the line decent match 90 Temp variation along line through empty duct to road surface at 215A 80 70 60 50 40 Calculated Duct Temperatures where FO cable is All 45 cable loaded in West DB All 45 cable loaded in Central DB All 45 cable loaded in East DB 10 ckts in East DB with 214 A More ckst in EDB at 66A 351; 43 30 351; 24 20 10 0 0 500 1.000 1.500 2.000 2.500 3.000 35
Site Installation, Calibration and Architecture of a DTS System 36
37 Recent DTS Installations with Calibrator
38 Site Calibration
39 General Layout of DTS System at Each Station
40 Overview of a monitoring corridor
How can System Operator use temperature data? 41
What does the Engineer need to do? - 1 Develop a physical model describing the cable layout, cable construction and material properties Define ambient soil temperature at depth of burial Define Soil thermal resistivity 42
Classical Rating Analyses - 2 Perform ratings calculations with commercial software, equations coded in MathCad or Finite Element Analyses Calculate the cable sheath temperatures for measured load and compare this with the DTS data Once this has been validated then one can undertake steady-state ampacity ratings for the cable system as well as in real-time Key items to note are the knowledge of soil thermal resistivity properties and ambient soil temperature 43
Example of a display Screen with Dynamic Ratings Typical Display Screen 44
45 Results from Preliminary Analyses
46 Comparison of Measured and Calculated Temperatures from Model
Lesson learned with DTS Systems and what s next? Even solid-state drives of computer that control DTS systems seem to fail after 3-4 years Temp calibration is important to preserve the sanctity of measurements The long-term (40 year) performance of optical fibers inside a power cable remains unknown Real-time ratings usage needs careful consideration and good understanding 47
CONCLUSIONS DTS basics advantages/challenges and fibre placements options- pros and cons Synopsis of history of DTS usage at BC Hydro and a few case studies Potential use of DTS data by System Operators to optimize asset utilization Lessons Learned and Future applications 48