Project: Western Alberta Transmission Line (WATL) HVDC Project Client: AltaLink
Attachment 3 Full Project Description
ACEC Canada – Canadian Consulting Engineering Awards 2016
Project: Western Alberta Transmission Line (WATL) HVDC Project Client: AltaLink Consultant: Teshmont Consultants LP
Project: Western Alberta Transmission Line (WATL) HVDC Project Introduction
Few projects in the realm of electric power transmission are as complex and costly as the development of a high voltage direct current (HVDC) transmission system. However, properly developed, HVDC systems can be one of the most reliable and cost effective means of transmitting power.
In 2010, Teshmont Consultants LP (Teshmont) was engaged by AltaLink to act as Owner’s Engineer for the Western Alberta Transmission Line (WATL) HVDC Project. WATL is the first HVDC system in service in Alberta and began transmitting power on December 10, 2015. The 500 kiloVolt (kV) line spans 350 km and connects the two major load centres of Calgary and Edmonton. HVDC technology was selected for this project because it provides significant improvement in performance over traditional alternating current (AC) transmission, having increased transfer capability, lower transmission losses, lower overall lifecycle costs over longer distances, as well as helping to improve overall system stability. The $1.65 billion project spanned five years and was technically challenging with a demanding schedule involving the client, several contractors, and a variety of other key stakeholders.
Technical Background and Information
Modern electric power systems work utilizing AC to generate, transmit, and distribute electricity to consumers. The AC voltages and currents change polarity at either 60 times per second (as in North America) or 50 times per second (as in Europe). HVDC, on the other hand, is transmitted using a constant voltage and current with no regular changes in polarity. In order to accomplish this, HVDC transmission requires the use of specialized equipment to convert the AC power that is generated to constant DC power. The DC power is then transmitted over HVDC transmission lines or cables to a destination where it is then converted again back to AC for onward delivery to consumers. The converter stations at either end of an HVDC line or cable consist of specialized equipment that needs to be uniquely designed and integrated specifically for each project application. This equipment includes converter transformers, converter valves and valve cooling systems, DC reactors, AC and DC filters, high voltage breakers and switches, as well as control, protection, and communication systems.
HVDC offers a number of benefits over the use of traditional AC transmission. The significant benefits can be summarized as follows:
• HVDC has lower electrical losses than AC transmission and, therefore, despite the additional cost of the conversion equipment, HVDC becomes more economically advantageous at longer distances. • HVDC results in the electrical isolation of sending and receiving end AC systems, which allows for power transmission between asynchronous AC systems that are not currently interconnected and may even be
2016 ACEC Canada Awards 1
Project: Western Alberta Transmission Line (WATL) HVDC Project Client: AltaLink Consultant: Teshmont Consultants LP
operating at different frequencies. This isolation minimizes the impact of network disturbances in one of the interconnected systems on the other. • HVDC allows for precise controllability of transmitted power, which can be used to increase the overall reliability of the surrounding AC transmission system(s). The HVDC system can also be used to address a number of issues that may be present within the AC network (reactive power problems, frequency regulation, power swings, etc.). • HVDC is particularly well suited (especially voltage sourced converter (VSC) HVDC technology) for the integration of renewable energy sources, which are often located a significant distance away from major load centers or offshore requiring the use of submarine cables. • Lines and cables transmitting HVDC power conduct electricity more effectively than AC, which allows for greater power density to be transmitted along physically and/or electrically constrained rights-of-way. • As opposed to AC where charging currents technically limit the practical length of high voltage cables to 40 to 50 km, HVDC poses no such limitation and can be used for very long submarine or terrestrial cable installations. • Because HVDC is more efficiently transmitted and only requires two conductors versus three conductors for AC, HVDC lines can be constructed on smaller towers along narrower rights-of-way. This reduces the environmental impact of an HVDC line as compared to similarly rated AC circuits and also reduces the installed cost per kilometer of transmission.
Project Description and Teshmont’s Scope
The WATL HVDC transmission line is 350 km long and runs between the Genesee area southwest of Edmonton and the Langdon area east of Calgary. The route, shown in Figure 1, runs parallel to existing 240 kV AC circuits for approximately 60% of the distance between Edmonton and Calgary.
Construction on the project began in 2012 with crews logging over 5.6 million hours of work over a three year period. The line was constructed using over 3500 km of wire and 20,000 tonnes of steel to construct 950 structures along the route. At the peak of construction, the project employed 1200 people. Figure 2 shows contractors stringing a section of the line.
In addition to the transmission line, two new HVDC converter stations, Crossings in the South and Sunnybrook in the north, as well as two AC substations were constructed at either end of the line. At Crossings Converter Station, a Static Compensator (STATCOM) was also installed. Other elements of the converter stations included DC filters, DC smoothing reactor, valve cooling, converter transformers, AC filters, and an HVDC converter building that contains the converter valves, as well as the control, protection, and communication systems. An aerial view of the Crossings Converter Station is shown in Figure 3.
2016 ACEC Canada Awards 2
Project: Western Alberta Transmission Line (WATL) HVDC Project Client: AltaLink Consultant: Teshmont Consultants LP
Figure 1: WATL Route
Figure 2: Transmission Line Stringing
2016 ACEC Canada Awards 3
Project: Western Alberta Transmission Line (WATL) HVDC Project Client: AltaLink Consultant: Teshmont Consultants LP
Figure 3: Crossings Converter Station in the Langdon Area
In 2009, Teshmont was engaged by the Alberta Electric System Operator (AESO) to perform system planning studies to determine the functional requirements for the potential development of two HVDC projects in Alberta – WATL and the Eastern Alberta Transmission Line (EATL). The results of these studies were used by Teshmont to prepare functional technical specifications for both of the HVDC projects. These functional technical specifications were issued by AESO to the two major transmission facility operators (TFO) in the province. AltaLink, a Berkshire Hathaway Energy Company located in Calgary, would develop WATL, while ATCO Electric would develop EATL.
In the fall of 2010, AltaLink turned to Teshmont to act as Owner’s Engineer for WATL to provide them with the technical guidance and leadership they required to successfully design, procure, construct, and operate this HVDC system. Over the next five years, Teshmont’s scope was comprehensive and broken down into distinct phases and stages as follows:
Phase 1 – Equipment Studies and Specification Development
During Phase 1, Teshmont performed a variety of equipment rating studies to determine the exact requirements of the key components of the converter stations. These detailed studies were based on the functional specifications Teshmont previously prepared for the AESO. The results of these studies were then used by Teshmont to prepare the comprehensive technical specification for an engineer, procure, and construct (EPC) request for proposal (RFP) issued by AltaLink for the design, manufacture, delivery, construction, and commissioning of the two converter stations required for the first stage of the WATL project. In addition to preparing the technical specification, which was over 400 pages, Teshmont also assisted AltaLink in the preparation of the commercial terms of the agreement.
2016 ACEC Canada Awards 4
Project: Western Alberta Transmission Line (WATL) HVDC Project Client: AltaLink Consultant: Teshmont Consultants LP
Phase 2 – Bid Evaluation and Contract Award
After a three month tendering period, Teshmont performed a comprehensive and detailed review of the bids submitted to evaluate conformance to the specifications and to assess the different offerings from a technical standpoint in order to provide AltaLink with a ranking of the bidders on a technical merit and value basis. The review also included a series of clarification questions and associated responses. Once a preferred bidder was identified, Teshmont supported AltaLink through the contract negotiations and prepared a conformed specification at the end of negotiations, which encapsulated all of the changes to the original specification that were agreed upon during the negotiations. The final contract for the converter stations was awarded to Siemens of Germany.
Phase 3 – Design, Manufacture, Installation, and Commissioning
The third phase of the project was broken down into four distinct stages as follows:
Stage 1: Design Review – During the design review stage, Siemens was required to submit study reports, drawings, equipment specifications, schedules, plans, and other documents. Teshmont’s job was to not only review these documents, checking for conformance to specified requirements but also to manage the flow of these submittals within the AltaLink/Teshmont team to ensure timely responses, which were critical in maintaining the project schedule. Teshmont also reviewed the design of the transmission line, which was being built under separate contracts managed by SNC Lavalin. The line design review included conductor and insulator selection, tower design, as well as minimum electrical clearances.
Stage 2: Manufacturing – During the manufacturing phase, Teshmont monitored Siemens’ progress and reviewed factory test plans and subsequent test results of major components. For the most critical components, Teshmont staff attended factory acceptance tests together with AltaLink staff to ensure the quality of the delivered equipment.
Stage 3: Installation – During site installation of the equipment, Teshmont supported AltaLink by providing feedback to any questions or concerns that arose. Teshmont staff, while not permanently on-site, did make site visit at key times to view progress.
Stage 5 Commissioning – During final energization and commissioning of the system, Teshmont reviewed the commissioning plan and was on-site for critical first energization and subsequent system testing up to achievement of full power transmission readiness on December 10, 2015.
In addition to the above, Teshmont provided project management support and coordination throughout the lifecycle of the project, overseeing the effective and time critical flow of information between the various stakeholders. This involved management of the massive amounts of data flowing through the project SharePoint portal between all of the project stakeholders in a timely manner so as not to delay the project
2016 ACEC Canada Awards 5
Project: Western Alberta Transmission Line (WATL) HVDC Project Client: AltaLink Consultant: Teshmont Consultants LP
schedule. Teshmont also had the responsibility of reviewing, vetting, and coordinating comments from various teams of subject matter experts involved in the project.
Teshmont worked together with key AltaLink personnel throughout the project for training and technology transfer purposes. This was seen from the outset as a key factor to having a successful project, as this would be the first HVDC project for AltaLink and they would be ultimately be responsible for ongoing operation and maintenance of the system after it was commissioned.
Project Complexities and Challenges
The WATL Project was a $1.65 billion dollar project with multiple parties involved over a span of five years. Teshmont had to ensure that the technical specifications were clear and concise and that the contractors adhered to the technical specifications while remaining on schedule and within budget. In order to accomplish this, information exchange between stakeholders in a well-organized and timely manner was essential. Teshmont was responsible for setting up and managing a process and system for document submittal and review utilizing Microsoft SharePoint that ultimately was used on over 32,000 documents shared amongst a number of stakeholders over the course of the five year project.
WATL also brought particular technical challenges as it was the first HVDC system to be energized in Alberta. Thorough study was essential to ensure that the initial 1000 MW line embedded in the heart of the existing Alberta electric system would not have any adverse effects. Some of the particular technical issues that had to be examined for WATL included:
- Effects of commutation failures
- Effects of transformer energization
- Effects of transient overvoltages
- Possible control interactions and power voltage instability
- Effects on the rating of existing harmonic filters in other substations
Another challenge was the potential impact of the transmission line on the countless pipelines found in the surrounding area. In many instances, HVDC systems are developed utilizing ground electrodes, which allow for the HVDC system to operate in ground current return mode for short periods of time during certain operating conditions. Utilization of a ground electrode allows for a much simpler, smaller, and less expensive design of the HVDC transmission line towers. However, operation utilizing a ground electrode may have undesirable impacts on nearby infrastructure, which would need to be examined and possibly mitigated. Due to the possible safety and operating concerns with the numerous oil and gas pipelines in the region, it was decided to develop the HVDC line with a metallic return conductor and avoid the use of ground electrodes.
2016 ACEC Canada Awards 6
Project: Western Alberta Transmission Line (WATL) HVDC Project Client: AltaLink Consultant: Teshmont Consultants LP
The project schedule was another challenge. Despite the five year duration, a number of key activities throughout the project had very short timelines in order to meet key milestone dates. The initial front-end engineering study, design, specification, bid, review, negotiate, and award process for the converter stations was completed within six months compared with a more typical duration of eight to twelve months. Construction of the transmission line was also a challenge due to the relatively tight construction schedule. In order to expedite construction of the line, helicopters were used to assist with not only tower erection as shown in Figure 4, but also stringing of the line as shown in Figure 5.
Figure 4: Tower Assembly Using a Helicopter Air Crane
Figure 5: Conductor Stringing using a Helicopter
2016 ACEC Canada Awards 7
Project: Western Alberta Transmission Line (WATL) HVDC Project Client: AltaLink Consultant: Teshmont Consultants LP
Innovation and Application of Technology
The selection of HVDC transmission technology for interconnecting the major Alberta load centres of Calgary and Edmonton was made based on studies results that showed the technical advantages of HVDC over a similarly rated AC option were of higher benefit.
Any HVDC project is technically complex and involves careful study and planning to ensure that the HVDC technology is properly applied and the WATL project was no exception. Power system analysis performed by Teshmont indicated that there were potential issues with interactions between the planned converter station and the Alberta interconnected electric system at the Crossings Converter Station near Langdon. In order to mitigate the identified issues, the project implementation required a STATCOM, which is a fast power electronic based regulating device used to provide precise voltage regulation. The STATCOM at Crossings Converter Station minimizes the impact on the AC system when the HVDC system’s filter banks required to absorb the harmonics generated by the converters are switched in and out.
The converters are controlled by state of the art high speed advanced control and protection systems, which are able to precisely regulate the amount and direction of power flow through the HVDC system. The control and protection systems are also able to quickly respond to disturbances in the adjoining AC network to help operators maintain system control and stability during outages. Another major application of advanced technology on the project was in the method of testing these control and protection systems in the factory. These tests took over two months and were performed in Siemens’ factory in Germany utilizing a power system real time digital simulator (RTDS). The RTDS is an advanced parallel processing super computer that, when loaded with a model of the power system, is able to simulate the response of a power grid to HVDC controls in real time. When connected to the simulator, the HVDC controls behave and respond as if they were in operation in the real power grid. This method allows for very accurate testing to be performed and modifications to be carried out on the HVDC controls without the risk of causing problems, including blackouts, in the real power system.
While initially installed and commissioned for two terminal operation at 1000 MegaWatts (MW) maximum power transfer capability, the HVDC line has been designed to be upgraded to 3000 MW with no additional structures or conductors required. As well, the system has also been developed to support the potential future addition of more converter stations to form a multi-terminal scheme. Multi-terminal HVDC transmission is highly complicated from a HVDC control and protection perspective and currently there are only two such systems in operation in the world.
Social/Economic/Environmental Impact
As noted previously, HVDC technology was selected for a number of reasons, including the reduction of electrical power loses. As a result of these lower losses, the project is estimated to reduce carbon emissions by approximately 350,000 tonnes, which is the equivalent of removing 65,000 vehicles from Alberta’s roads.
2016 ACEC Canada Awards 8
Project: Western Alberta Transmission Line (WATL) HVDC Project Client: AltaLink Consultant: Teshmont Consultants LP
By selecting HVDC to interconnect the two largest load centres in the province, WATL will help to improve the overall reliability of electricity supply to consumers in these centres and in the province. Secure and dependable supply of electricity helps maintain a high quality of life, security, and productivity for the people of Alberta.
The project also relieves transmission system congestion that existed in the existing AC network and that limited consumers’ access to the generator facility owners. As Alberta is the only truly deregulated energy market in North America, with consumers having choice in their electricity provider, unrestricted access to electricity generators results in increased competition and ultimately lower energy costs to consumers.
The selection of HVDC also resulted in a transmission line whose towers are smaller in size and therefore take up less space than a similarly rated AC transmission line. This reduction in tower size results in less land being required for the line right-of-way and is less visually obstructive than a comparable AC transmission line.
Finally, the application of HVDC has no observed negative effects on potential health impacts resulting from electric or magnetic fields.
Conclusions
The WATL project was significant and historic for both AltaLink, as well as the electric power system in Alberta. Teshmont was instrumental in helping AltaLink throughout the five years of development and implementation of the project by working closely to provide technical leadership, guidance, advice, and training for the successful operation of the WATL HVDC Project. Thanks in large part to Teshmont’s extensive involvement in the project, the WATL HVDC Project will provide environmental, economic, and societal benefits for all Albertans throughout its life.
2016 ACEC Canada Awards 9
Project: Western Alberta Transmission Line (WATL) HVDC Project Client: AltaLink
Attachment 4 Photographs
ACEC Canada – Canadian Consulting Engineering Awards 2016