In today’s changing utility environment, one thing remains constant - electric utilities are continually looking for better ways to increase transmission capacity to satisfy the ever-growing demand for power. In the ”distant past”, utilities were able to construct new transmission lines whenever load growth determined the need. Today, utilities don’t have that option due to environmental and property considerations and are challenged to find innovative ways to increase capacity with their existing plant, all within tight budget constraints.
To the transmission line design engineer trying to increase line capacity, knowing exactly what is in the field is essential before re-designing. Often however, important information including thermal temperature constraints, minimum ground clearance, structural loads and wire sag and tension is not accurately recorded on existing plan and profile drawings. In general, the plan and profile drawing is a record of how the line was designed, not necessarily how the line was built. Use of these drawings as a base for future upgrades, therefore, means it is likely that inaccuracies will be transferred forward to the new design. The possibility that no information whatsoever is available on a particular line also exists. In such situations, what option is left to the engineer?
This was exactly the situation faced by Manitoba Hydro when, due to expanding power sales, a small portion of the utility’s 115 kV transmission system became overloaded. The need for upgrading was clear, but, since much of this system was built between 1914 and 1931, plan and profile drawings were either severely outdated or non-existent. To meet the need for a new survey that would provide both terrain information and accurate sag and tension data on every span along the line, Manitoba Hydro selected to use LiDAR (Light Detection and Ranging) technology. LiDAR was chosen for two important reasons – firstly, the need to upgrade was urgent and the LiDAR data collection method offered very fast turn-around time from collection to delivery. Secondly, and most importantly, LiDAR offers the highly accurate ability to map terrain and wire catenary shape in every span.
“When we took delivery of the first complete line data set, we began to analyze it using standard transmission line design modeling software. It was a real awakening” says Jim Koop, General Manager of Manitoba Hydro’s Worldwide Integrated Rating Enhancement (W.I.R.E.) Services division. “The information available for us to analyze the existing line condition didn’t just improve our ability to accurately find problems, it also allowed us to use other innovative approaches to line upgrades.”
One of those innovative approaches to upgrading was a wire retensioning technique called “Nip&Tuck”™ (N&T). This software, developed by Itron (formerly LineSoft), is essentially a “multi-span analysis” program commonly used by transmission line engineers to determine the effects of unbalanced loads on transmission lines. N&T creates a computer model of the transmission line wire based on the LiDAR data and models its behavior under high temperature operation. It then identifies clearance violations that are eliminated by two methods. The first is a “Nip”, which refers to the removal of a small segment of wire. The second is a “Tuck”, which slides the conductor support clamp forward or backward along the wire. These operations can be done individually or together on any span requiring additional clearance.
On the first of several lines Manitoba Hydro applied the N&T process, design engineers increased the line’s thermal rating from 56°C (52 MW) to 100°C (115 MW). Not only did this process provide for a capacity increase of 121%, this increase was achieved with a saving of 70% over conventional retensioning techniques. Since then, Manitoba Hydro has collected LiDAR data on approximately 2000 kilometers of 115 kV and 230 kV transmission line and has successfully used N&T upgrade techniques on over 160 km of line.
One of the direct spin-offs of Manitoba Hydro’s extensive experience with LiDAR technology was the creation of their W.I.R.E. Services division in July 2001. Through an exclusive partnership with LiDAR Services International (LSI) of Calgary, Canada who provides the data collection services, Manitoba Hydro is able to offer quality LiDAR data collection and engineering analysis to electrical utilities that want to use new technology methods, but can’t, due to manpower or other constraints.
In the fall of 2001, SaskPower, the electric utility serving the province of Saskatchewan, Canada contracted W.I.R.E. Services to provide a capacity analysis on its 138 kV transmission line between Saskatoon and North Battleford (Q1N/Q2N). The 135 kilometer long, double circuit steel tower line was built in 1961, traversing prairie farmland in central region of the province. The line had experienced numerous catastrophic failures due to extreme weather events during its 40 years in service. Over the years SaskPower had undertaken several mitigative measures, including the addition of 6 wood pole dead end structures designed to minimize cascading failures.
During the previous year, SaskPower transmission design engineers conducted a ground clearance study based on the original plan & profile drawings from 1961. The main obstacle that prevented a precise analysis was several tension changes that had occurred over the wire’s life. However, the study revealed that at least two of the four lowest 477 MCM Hawk conductors were subject to experience clearance problems at operating temperatures around 20°C. “Given the clearance problems we could experience, we knew what we needed was a survey that would provide us with all the data we required for a proper analysis.” said Don Nagel, SaskPower’s Senior Transmission Engineer.
Work on the survey started when LSI mobilized their Helix LiDAR system to North Battleford in October 2001. In the space of 4 hours and 45 minutes, via a 135-km return flight from North Battleford to Saskatoon, LSI used onboard sensors to capture above ground LiDAR data and digital video imagery of the transmission line. Simultaneously, ground crews monitored weather stations, capturing temperature and wind data essential for determining base case wire temperatures.
Following the flight, with well over 26 million points collected, the dense LiDAR data was filtered to create a manageable DTM (digital terrain model). Each point in the DTM was assigned a feature code to define its particular attribute, such as bare earth point, low vegetation, structure, wire, etc. In addition, every point representing an overhead wire hit in every span was stripped out and a catenary shape determined for the sag and tension analysis. Another added feature provided was the creation of orthorectified digital images of the entire right of way. These full colour images are useful to the design engineer as they offer an aerial perspective view of the line at true scale, and allows measurements from point to point. It is also possible to integrate these images into modeling programs and view the terrain model with an image overlay simulating the true relief of the right of way.
With all this data on hand, the analysis of SaskPower’s line was set to begin. Experienced Manitoba Hydro transmission line engineers evaluated each of the four lowest conductors separately, then created individual design models for each. Combining the weather data along with line current, the wire temperature was established for the high temperature simulation. Evaluation of the minimum clearance in each span was carried out for a base case temperature of 9°C. No clearance violations were expected and none were found. This process was repeated for temperatures from 20°C through to 100°C in 10 degree increments and the number of clearance problems determined and graphed. It was confirmed that the maximum operating temperature of these two circuits was below the operating limit set by system control and SaskPower quickly requested W.I.R.E. Services to develop a Nip&Tuck solution.
One of the first steps was to establish loading criteria for this 40-year-old steel structure line. SaskPower imposed stringent longitudinal imbalance limits on the structure arms because of the narrow base dimension and past failure history. Maximum tension limits were also set for both very cold (-35°C) temperatures and heavy wind and Ice conditions. Balancing these conditions while increasing ground clearance would prove to be a challenge to Nip&Tuck.
Next, the new upgrade operating temperature was established using a combination of load growth forecasts and a feasibility study of how much sag reduction N&T could reasonably achieve. The end result indicated that 100 MVA, which equated to a 66°C conductor temperature limit, would meet the planning projections for load growth in the Saskatoon area for the next ten years. All that was left was for design engineers to develop a solution that would meet all these constraints.
Since the bottom four conductor models were already available from the rating study, each was loaded into N&T. The 331 transmission line spans multiplied by the four individual wire models combined for a total of 1324 spans. Of these, approximately 26% or 341 spans required sag modifications to meet minimum ground clearance values for a 66°C operating temperature. All remaining spans met minimum clearances and did not need any modification.
It was determined that, in total, 214 conductor nips and 380 clamp shifts would be required to achieve an upgraded operating temperature of 66°C on this line. “One of the most impressive things was the speed at which the N&T solution can be implemented” recounts Don Nagel.
SaskPower hired 3 local contractors and set them to work in specified areas along the line. Each contractor was given a preset rate for each splice installed and for every support clamp adjustment made. With this combined effort, the Nip&Tuck design solution was completed in 14 days.
“One crew could quite easily complete 10 Nip operations in one day, while another came behind and shifted the support clamps” mentions Don. “The whole operation went very quickly, especially since the Nip splice could be installed anywhere in the span. Crews were able to find convenient places to set up which made it go faster.”
Another highly impressive result of this project was the cost saving realized by using the Nip&Tuck solution. The original cost estimates for the project using conventional techniques were determined to be more than $1.25 million. The Nip & Tuck technology, SaskPower saved more than 80% with actual costs in the neighborhood of $232,000.
SaskPower put the North Battleford/Saskatoon circuits back into service on May 30, 2001, a mere 36 days after the request was sent to engineer a Nip&Tuck solution. “We’re very pleased with W.I.R.E. Services. They’ve got an exceptional ability to provide quality-engineering services for upgrading transmission lines. They bring a truly unique utility perspective to the project and don’t just leave you with piles of data” says Don Nagel. “Best of all, after analyzing the line rating, they were able to provide us with a real workable and very affordable solution”.
SaskPower was also interested in considering further upgrade options for load growth forecasts beyond 10 years. In response, a 100°C operating solution was provided. The design solution required 206 structure extensions, to raise support heights, along with an additional 208 Nip and 231 Tuck operations. SaskPower now has the advantage of knowing what is involved to upgrade to 100°C and can accurately forecast the cost when the time comes.
Manitoba Hydro is also committed to the use of LiDAR surveys for upgrade data acquisition. They are currently in the 3rd year of an 8-year program to accurately map approximately 40% of their transmission system. During this winter season Manitoba Hydro construction crews will complete over 160 km of N&T upgrade solutions to two 115 kV transmission lines.
According to Jim Koop, Manitoba Hydro is committed to becoming a leader in upgrade technology. And he adds they are also committed to bringing that technology and its many benefits to other utilities.
About the Author
J. E. (Jim) Koop is the General Manager of W.I.R.E. Services, a division of Manitoba Hydro located in Winnipeg Canada. Mr. Koop graduated from Civil Engineering Technology in 1982 from Red River College in Winnipeg, Manitoba. He is a registered Engineering Technologist in Manitoba as well as a member of IEEE, Power Engineering Society. Mr. Koop has over 18 years experience in Transmission Line Design at Manitoba Hydro. He was responsible for major transmission line projects from conceptual design planning through to construction. His interest in LiDAR technology began in 1998 when he developed and coordinated a program to verify existing line ratings through the use of LiDAR technology. The program’s success led to the formation of a business relationship with LiDAR Services International and the creation of W.I.R.E. Services. He can be reached at jekoop@wireservices.ca.
To the transmission line design engineer trying to increase line capacity, knowing exactly what is in the field is essential before re-designing. Often however, important information including thermal temperature constraints, minimum ground clearance, structural loads and wire sag and tension is not accurately recorded on existing plan and profile drawings. In general, the plan and profile drawing is a record of how the line was designed, not necessarily how the line was built. Use of these drawings as a base for future upgrades, therefore, means it is likely that inaccuracies will be transferred forward to the new design. The possibility that no information whatsoever is available on a particular line also exists. In such situations, what option is left to the engineer?
This was exactly the situation faced by Manitoba Hydro when, due to expanding power sales, a small portion of the utility’s 115 kV transmission system became overloaded. The need for upgrading was clear, but, since much of this system was built between 1914 and 1931, plan and profile drawings were either severely outdated or non-existent. To meet the need for a new survey that would provide both terrain information and accurate sag and tension data on every span along the line, Manitoba Hydro selected to use LiDAR (Light Detection and Ranging) technology. LiDAR was chosen for two important reasons – firstly, the need to upgrade was urgent and the LiDAR data collection method offered very fast turn-around time from collection to delivery. Secondly, and most importantly, LiDAR offers the highly accurate ability to map terrain and wire catenary shape in every span.
“When we took delivery of the first complete line data set, we began to analyze it using standard transmission line design modeling software. It was a real awakening” says Jim Koop, General Manager of Manitoba Hydro’s Worldwide Integrated Rating Enhancement (W.I.R.E.) Services division. “The information available for us to analyze the existing line condition didn’t just improve our ability to accurately find problems, it also allowed us to use other innovative approaches to line upgrades.”
One of those innovative approaches to upgrading was a wire retensioning technique called “Nip&Tuck”™ (N&T). This software, developed by Itron (formerly LineSoft), is essentially a “multi-span analysis” program commonly used by transmission line engineers to determine the effects of unbalanced loads on transmission lines. N&T creates a computer model of the transmission line wire based on the LiDAR data and models its behavior under high temperature operation. It then identifies clearance violations that are eliminated by two methods. The first is a “Nip”, which refers to the removal of a small segment of wire. The second is a “Tuck”, which slides the conductor support clamp forward or backward along the wire. These operations can be done individually or together on any span requiring additional clearance.
On the first of several lines Manitoba Hydro applied the N&T process, design engineers increased the line’s thermal rating from 56°C (52 MW) to 100°C (115 MW). Not only did this process provide for a capacity increase of 121%, this increase was achieved with a saving of 70% over conventional retensioning techniques. Since then, Manitoba Hydro has collected LiDAR data on approximately 2000 kilometers of 115 kV and 230 kV transmission line and has successfully used N&T upgrade techniques on over 160 km of line.
One of the direct spin-offs of Manitoba Hydro’s extensive experience with LiDAR technology was the creation of their W.I.R.E. Services division in July 2001. Through an exclusive partnership with LiDAR Services International (LSI) of Calgary, Canada who provides the data collection services, Manitoba Hydro is able to offer quality LiDAR data collection and engineering analysis to electrical utilities that want to use new technology methods, but can’t, due to manpower or other constraints.
In the fall of 2001, SaskPower, the electric utility serving the province of Saskatchewan, Canada contracted W.I.R.E. Services to provide a capacity analysis on its 138 kV transmission line between Saskatoon and North Battleford (Q1N/Q2N). The 135 kilometer long, double circuit steel tower line was built in 1961, traversing prairie farmland in central region of the province. The line had experienced numerous catastrophic failures due to extreme weather events during its 40 years in service. Over the years SaskPower had undertaken several mitigative measures, including the addition of 6 wood pole dead end structures designed to minimize cascading failures.
During the previous year, SaskPower transmission design engineers conducted a ground clearance study based on the original plan & profile drawings from 1961. The main obstacle that prevented a precise analysis was several tension changes that had occurred over the wire’s life. However, the study revealed that at least two of the four lowest 477 MCM Hawk conductors were subject to experience clearance problems at operating temperatures around 20°C. “Given the clearance problems we could experience, we knew what we needed was a survey that would provide us with all the data we required for a proper analysis.” said Don Nagel, SaskPower’s Senior Transmission Engineer.
Work on the survey started when LSI mobilized their Helix LiDAR system to North Battleford in October 2001. In the space of 4 hours and 45 minutes, via a 135-km return flight from North Battleford to Saskatoon, LSI used onboard sensors to capture above ground LiDAR data and digital video imagery of the transmission line. Simultaneously, ground crews monitored weather stations, capturing temperature and wind data essential for determining base case wire temperatures.
Following the flight, with well over 26 million points collected, the dense LiDAR data was filtered to create a manageable DTM (digital terrain model). Each point in the DTM was assigned a feature code to define its particular attribute, such as bare earth point, low vegetation, structure, wire, etc. In addition, every point representing an overhead wire hit in every span was stripped out and a catenary shape determined for the sag and tension analysis. Another added feature provided was the creation of orthorectified digital images of the entire right of way. These full colour images are useful to the design engineer as they offer an aerial perspective view of the line at true scale, and allows measurements from point to point. It is also possible to integrate these images into modeling programs and view the terrain model with an image overlay simulating the true relief of the right of way.
With all this data on hand, the analysis of SaskPower’s line was set to begin. Experienced Manitoba Hydro transmission line engineers evaluated each of the four lowest conductors separately, then created individual design models for each. Combining the weather data along with line current, the wire temperature was established for the high temperature simulation. Evaluation of the minimum clearance in each span was carried out for a base case temperature of 9°C. No clearance violations were expected and none were found. This process was repeated for temperatures from 20°C through to 100°C in 10 degree increments and the number of clearance problems determined and graphed. It was confirmed that the maximum operating temperature of these two circuits was below the operating limit set by system control and SaskPower quickly requested W.I.R.E. Services to develop a Nip&Tuck solution.
One of the first steps was to establish loading criteria for this 40-year-old steel structure line. SaskPower imposed stringent longitudinal imbalance limits on the structure arms because of the narrow base dimension and past failure history. Maximum tension limits were also set for both very cold (-35°C) temperatures and heavy wind and Ice conditions. Balancing these conditions while increasing ground clearance would prove to be a challenge to Nip&Tuck.
Next, the new upgrade operating temperature was established using a combination of load growth forecasts and a feasibility study of how much sag reduction N&T could reasonably achieve. The end result indicated that 100 MVA, which equated to a 66°C conductor temperature limit, would meet the planning projections for load growth in the Saskatoon area for the next ten years. All that was left was for design engineers to develop a solution that would meet all these constraints.
Since the bottom four conductor models were already available from the rating study, each was loaded into N&T. The 331 transmission line spans multiplied by the four individual wire models combined for a total of 1324 spans. Of these, approximately 26% or 341 spans required sag modifications to meet minimum ground clearance values for a 66°C operating temperature. All remaining spans met minimum clearances and did not need any modification.
It was determined that, in total, 214 conductor nips and 380 clamp shifts would be required to achieve an upgraded operating temperature of 66°C on this line. “One of the most impressive things was the speed at which the N&T solution can be implemented” recounts Don Nagel.
SaskPower hired 3 local contractors and set them to work in specified areas along the line. Each contractor was given a preset rate for each splice installed and for every support clamp adjustment made. With this combined effort, the Nip&Tuck design solution was completed in 14 days.
“One crew could quite easily complete 10 Nip operations in one day, while another came behind and shifted the support clamps” mentions Don. “The whole operation went very quickly, especially since the Nip splice could be installed anywhere in the span. Crews were able to find convenient places to set up which made it go faster.”
Another highly impressive result of this project was the cost saving realized by using the Nip&Tuck solution. The original cost estimates for the project using conventional techniques were determined to be more than $1.25 million. The Nip & Tuck technology, SaskPower saved more than 80% with actual costs in the neighborhood of $232,000.
SaskPower put the North Battleford/Saskatoon circuits back into service on May 30, 2001, a mere 36 days after the request was sent to engineer a Nip&Tuck solution. “We’re very pleased with W.I.R.E. Services. They’ve got an exceptional ability to provide quality-engineering services for upgrading transmission lines. They bring a truly unique utility perspective to the project and don’t just leave you with piles of data” says Don Nagel. “Best of all, after analyzing the line rating, they were able to provide us with a real workable and very affordable solution”.
SaskPower was also interested in considering further upgrade options for load growth forecasts beyond 10 years. In response, a 100°C operating solution was provided. The design solution required 206 structure extensions, to raise support heights, along with an additional 208 Nip and 231 Tuck operations. SaskPower now has the advantage of knowing what is involved to upgrade to 100°C and can accurately forecast the cost when the time comes.
Manitoba Hydro is also committed to the use of LiDAR surveys for upgrade data acquisition. They are currently in the 3rd year of an 8-year program to accurately map approximately 40% of their transmission system. During this winter season Manitoba Hydro construction crews will complete over 160 km of N&T upgrade solutions to two 115 kV transmission lines.
According to Jim Koop, Manitoba Hydro is committed to becoming a leader in upgrade technology. And he adds they are also committed to bringing that technology and its many benefits to other utilities.
About the Author
J. E. (Jim) Koop is the General Manager of W.I.R.E. Services, a division of Manitoba Hydro located in Winnipeg Canada. Mr. Koop graduated from Civil Engineering Technology in 1982 from Red River College in Winnipeg, Manitoba. He is a registered Engineering Technologist in Manitoba as well as a member of IEEE, Power Engineering Society. Mr. Koop has over 18 years experience in Transmission Line Design at Manitoba Hydro. He was responsible for major transmission line projects from conceptual design planning through to construction. His interest in LiDAR technology began in 1998 when he developed and coordinated a program to verify existing line ratings through the use of LiDAR technology. The program’s success led to the formation of a business relationship with LiDAR Services International and the creation of W.I.R.E. Services. He can be reached at jekoop@wireservices.ca.
