Substation Projects: Project Delivery System & Engineering Delivery System
Whether a substation is custom designed, or based on customer's standard designs, or a combination of both, the engineering delivery system depends on how the entire project is approached, or in other words, the project delivery system.
In most part of the world, utilities generally prefer the EPC route of project delivery for their substation projects but in New Zealand & Australia, DBB route is the most preferred option.
Project Delivery System
The main modern project methods (also known as project models, approaches, or contract arrangements) are listed below with a brief definition. Each has their advantages and disadvantages. Detailed discussion of these methods is beyond the scope of this chapter, but they are presented to see how the design integrates into each method and how it can affect design philosophy.
§ Design-Build: a project is designed then constructed by a single entity, the owner, such as a utility using its internal engineering staff and its company construction crews;
§ Design-Bid-Build or Traditional Method: a project is designed by the owner, such as a utility using its internal engineering staff, and then the owner tenders bids and contracts with a separate entity for the construction;
§ Engineer-Procure-Construct: a project owner contracts with one entity to perform the design, procure, construct, and handover the project to that owner. This is sometimes known as Turnkey project execution. Other terms used for this method are Engineer-Procure-Construct-Commission (EPCC) and Lump Sum Turn Key (LSTK);
§ Engineer-Procure-Construction Management: a project owner contracts with one entity to provide management services for the whole project. The EPCM contractor coordinates all design, procurement, and construction services. They may or may not undertake actual site work, but they must ensure required work is completed on time;
§ Build-Own-Operate: a project in which a private entity, finances, designs, builds, owns, and operates a facility with some degree of encouragement from a utility or a government, which may offer other financial incentives such as tax-exempt status. This differs from the previous methods in that it interjects a form of project financing and operating into the mix;
§ Build-Operate-Transfer: a project in which a private entity, finances, designs, builds, and operates a facility receiving a concession from the private or public sector as stated in the concession contract. This enables the project proponent to recover its investment, operating, and maintenance expenses for the project before transferring it to the public sector. This too interjects project financing and operating. This is found to be a typical approach in the resource sector, which is time-constrained, whereby the mine or process establishes the substation to a set of standards and then transfers it to the host utility as a gifted asset. This approach reduces the risk for the utility and places it upon the customer. It also used by some utilities as an option for industrial customer and IPP connections;
§ Build-Own-Operate-Transfer: a project in which a private entity, finances, designs, builds, owns, and operates a facility. During the specified concession period the private entity owns and operates the facility with the prime goal to recover the costs of investment, operating, and maintenance while trying to achieve higher margin on project. The facility is then transferred to the government or partner at a previously agreed-upon or market price. These specific characteristics make it suitable for infrastructure projects like highways, railway, airports, and power generation which have political importance for the social welfare but are not attractive for other types of private investments.
Engineering Delivery System
Irrespective of project delivery method, the precursor to detail engineering delivery and the earliest of all design activities is the development of the project owner’s concept, with regards to the engineering aspects. This is called Front End Engineering (FEE) or Front End Engineering Design (FEED). It is sometimes referred to as Pre-Project Planning (PPP), Front-End Loading (FEL), Early Contractor Involvement (ECI) or Optioneering.
Conceptual Design and/or Feasibility Study: Upon conceiving a project, the owner usually conducts a Conceptual Design and/or Feasibility Study to see if the proposed project is worth pursuing. Since there are always alternate ways to accomplish an objective, studies include optioneering or the selection of preferred options out of a wider array of likely possible design solutions considered. Each possible solution has its advantages and disadvantages in areas such as utilisation of resources, performance, constructability, operability, maintainability, future expandability, and economic use of available capital funds. The goal is to study, evaluate, compare and optimise toward the best solution to pursue. This is typically accompanied by a System Impact Study to see how the proposed project affects the surrounding parts of the system and what system modifications would be necessary (e.g. reconductoring or upgrading affected transmissions lines).
Front End Engineering (FEE) or Front End Engineering Design (FEED) or Pre-Project Planning (PPP) or Front-End Loading (FEL) or Early Contractor Involvement (ECI) or Optioneering: FEED is the basic engineering that focuses on developing technical requirements of the scope, evaluating potential risks, and determining the main investment costs for the project. The beginning of a project is the best time to start considering Safety in Design (SiD) to make the substation safer. The concept is to avert potential safety incidents, injuries and fatalities for construction and operational phases by taking well-defined, mandatory steps built in to the design phase to address safety requirements. This is accomplished by the use of shared lessons learned, a focus on hazards and their control, applying practices and techniques geared for safer outcomes, and a hierarchical engineering review/approval structure.
As an analogy to describe the FEED philosophy, think of engineering as the process of solving problems. To do this, it is wise to define the “problem” first and then identity the “solution” afterwards. Recognise that these are two fundamental steps in the engineering process. Following these steps in order, avoids rushing first into the solution, and even worse, to a certain preferred solution that may not even be the best one for the given problem. The designer needs to understand the problem clearly before solving it. FEED is the tool to understand and define the problem. It guides the designer to make some of the most important decisions up front so that they end up spending far less time and money later on when the project is deep into its execution stages.
Thus, FEED is a way of looking at a project before completing the detailed design, and is used to thoroughly plan a project and control expenses. FEED is conducted by the planning engineers, working in close communication with the owners, to thoroughly understand and logically consider all aspects of the project, both initial installation and future expansion, as well as potential problems. The engineering section then dissects this problem and generates what some call the “Basic Engineering” where the real tangible scope of work, the stage-by-stage process of delivering the solution, and the impacts on outages and remote ends all become clearly evident. This step also includes consideration of lesson learned from the past in order to avoid issues regarding deliverability and constructability of solutions, as well as avoiding variations for better consistency. It is followed by a review to ensure it is well developed to address the objective and scope (the “problem”), and then approved by all involved. The FEED package first becomes the basis for bidding and then for designing in the project execution phases, which in turn has its own critical review(s) ensuring the detailed design (the “solution”) is also well developed.
Finally, some of the FEED deliverables would be a General Single Line Diagram, a Preliminary Layout, and a Material-Take-Off List. Afterward, the project proceeds with “Detailed Engineering” where the final design deliverables (e.g. Schematic Diagrams, Plan and Elevation Views, and a Bill of Material) are prepared.
Detailed Engineering: A “simplified” view of the nominally five key engineering disciplines of Civil, Structural, Primary, Secondary and Telecommunication that are involved in substation engineering is shown below.
P.S. Content of this article are a direct extract from Cigre TB 740