Zark Bedalov - Practical Power Plant Engineering

The standards and codes are extremely important. Actually, there are three parts to your success as an experienced engineer:

1 Understanding the applicable standards and knowing how and where to apply them.

2 Referring to the suppliers' equipment catalogs and reviewing the graphs and performance data sheets to determine the proper equipment ratings and supplies for your specific applications.

3 Building experience by field reviews of the equipment performance and its related hardware.

A typical project referred to in this book is an ore‐bearing property, owned by an investor, which according to the exploration figures contains a large ore body of Cu/Zn ore. This can equally be a mining property of coal, silver, and gold, or it may be a brewery batch plant or a large harbor development.

On the power industry side, this may be a hydro development project, for which a catchment area is defined and dammed to create a head and estimate the flow of water that can be controlled from the area. The electrical part of the project, though large, is relatively small in comparison with the huge civil infrastructure required to be built. Utilities typically take ownership of these large projects.

If the project gets a go ahead by the investment partners, the investors or their bank will provide initial funding to engage an engineering company to investigate the project a bit closer. There are a number of different engagements possible between the owner and the engineer that can be employed. That may be a subject of another book.

The project team with all the engineering disciplines has been given an assignment to develop conceptual drawings and budget estimate. The conceptual design includes plant layouts, load flow diagrams, electrical design criteria for all the electrical activities and equipment, a key one‐line diagram, and a reasonable accurate capital cost estimate to be presented as a “bankable feasibility study.” This document will also serve as a basis for the future detail engineering design to build the project, should the project proceed further.

The design calculations in this conceptual study will use the system and equipment characteristics from previous projects similar to this one to generate the design parameters for the new project. The budget estimate is obtained from the various budget quotations, previous projects, and earlier work done in the country of the project with their labor rates.

During this three to six months of engineering phase, some major long lead mechanical and electrical equipment may be ordered on the basis of a possibility of cancelling the orders if things don't “pan out.” The electrical lead equipment may include the main transformers and HV switching equipment.

The flow diagrams show the flow of the ore, through the various plant processes, including additions of other ingredients: water, heat, and fuel to process it and take it to the final product. In this case, the final products are bars of Cu and Zn. Where there is Cu, there is a chance of minor percentage of gold, while silver is never far off from a deposit of Zn.

From the electrical design perspective, design criteria, major cable routing, and one‐line diagrams will define the shape of the plant power distribution and other aspects of the electrical equipment and plant operation.

Detail design will follow the conceptual phase. This “detailed” phase may last anywhere from 9 to 18 months for an industrial plant or two to four years for a power plant, depending on the type of plant. The conceptual drawings will be reworked and expanded. Procurement phase will commence by preparing the purchase specifications to specify equipment performance requirements and also to make the interface diagrams to tie up with the related mechanical equipment. Often, the electrical design may have to wait a while for the mechanical design to near its completion and their suppliers' drawings are in hands to determine the electrical ratings and the interfacing connections needed.

The first effort will be to update the electrical plant design criteria and the key one‐line diagram from the conceptual design phase. These two items are your two big pictures, and the foundations for everything else you plan to build on.

System studies: The detailed design will present final one‐line diagrams with the actual impedances and equipment characteristics. It will use the data based on the results from power system studies: load flows, motor start, voltage drops, phase and ground short circuits, arc flash, insulation coordination, and step and touch potential. The studies will determine more precise and factual system characteristics and prove that the selected equipment ratings conform to the requirements set out in the design criteria. For these calculations, we will use the software from various system houses, such as Easy Power, ETAP, Cyme, and others. The plant data will be laid out on a computer and let the computer do the math. Not only that, the computer teaches you the power system functioning. One can introduce changes and alternatives and then observe the impact of the changes on the power system performance. It allows you to select the optimal solutions.

Interfaces: At this time, schematic and wiring diagrams for all the motors and valves, cable lists, and plant layouts will be prepared.

One of my bosses once told me: “Project usually fails at the interfaces.” He was right. The projects require a huge effort by many personnel working on the project, ranging from secretaries to the managers. Possibilities of errors are ever‐present. The interface changes may be due to a late design modification initiated by other engineering departments. If not well communicated and reconfirmed, the changes may not get on the drawings. This applies also for the communications between the engineering departments, the suppliers, and fabricators. If the equipment arrives to site with incorrect connections, it will lead to a lot of confusion on site, “throwing blame around of who said what, and so on.” This is where the experience comes in from working on large projects and by recognizing how the equipment is supposed to work and how it relates to the other equipment. Experienced engineers would notice problems if incorrect drawings cross their desks.

Every discipline can use approximations, add (+) or delete (−) a few inches or feet here and there on the drawings. The electrical engineers have no such a benefit. We have to produce drawings that match the equipment perfectly. Electrical drawings show several hundreds of thousands of wires, power, and controls interfacing between the various electrical and mechanical equipment. The only grace we get is that we can bend the plant cables around in the cable trays.

You may have done your job to perfection, but unfortunately, when you come to the construction site, you may face some disappointments. You will notice the supplier's actual equipment does not match the drawings you received to prepare your diagrams from. The suppliers have just got confused and sent you drawings they had engineered for a previous customer, or they had made changes but failed to inform you.

Do not panic now. This is something to get used to. It happens. Once the wires are connected, you may notice different problems stemming from errors, suppliers' incorrect designs, and of course, the wiring errors. This is where precommissioning and commissioning comes into play to make sure everything is properly tested and made to work as intended.

Everyone can make mistakes. Let us be honest about it. Even mechanical engineers can make a mistake here and there. But there is nothing like what the electrical engineers face. Thousands and thousands of wires are laid out in the field, and each one must find its proper place or it may turn out to be a major mistake and error, which will have to be troubleshooted later during the plant commissioning. Fortunately, with the advances in technology, a half of wiring in the modern plant is now replaced by communication cables, coax, a pair of wires, etc., carrying thousands of signals which can be shaped and configured as part of the plant control system. But that is another story. That certainly is a wiring relief, but our problems will now likely resurface in the software during commissioning (see Chapter 17).