City of Breda Electrical Distribution System

Transcription

1 IOWA STATE UNIVERSITY DEPARTMENT OF ELECTRICAL AND COMPUTER ENGINEERING City of Breda Electrical Distribution System Design Plan Adviser: Dr. James D. McCalley Team Members: Bai Rui, Senior (EE) David Mindham, Senior (EE) Anthony Tong, Senior (EE) Christopher Krantz, Senior (EE)

2 DISCLAIMER: This document was developed as a part of the requirements of an Electrical and Computer engineering course at Iowa State University, Ames, Iowa. This document does not constitute a professional engineering design. Although the information is intended to be accurate, the associated students, faculty, and Iowa State University make no claims, promises, or guarantees about the accuracy, completeness, quality, or adequacy of the information. The user of this document shall ensure that any such use does not violate any laws with regard to professional licensing and certification requirements. This use includes any work resulting from this student-prepared document that is required to be under the responsible charge of a licensed engineer or surveyor. This document is copyrighted by the students who produced this document and the associated faculty advisors. No part may be reproduced without the written permission of the Senior Design course coordinator. 1

3 Section 0: Project Information Executive Summary Problem Statement Acknowledgments... 4 Section 1: High-Level Design Project Goals Concept Sketch Functional Decomposition Specific Functional Requirements System Analysis Technology Platforms/Choices Design Tradeoffs..10 Section 2: Detailed Design System Architecture (Block Diagram) Design of Each Step Design Process GNATT Chart Member Involvement Final Report Structure..16 Section 3: Testing and Evaluation Plan Test Plan Simulation.18 Section 4: Team Member Information

4 0.0 Project Information 0.1 Executive Summary The Breda Municipal Electric System is located in the town of Breda, Iowa. The utility serves over 500 customers. These customers include residential, commercial, and industrial. The main companies that provide power services to Breda Municipal are Western Area Power Municipal (WAPA), Municipal Energy Agency Nebraska (MEAN), and MidAmerican Energy. The city of Breda solicited the help of Iowa State s Senior Design team in order to research, guide, and implement new solutions to the their power distribution system. Diane Lucas, the Breda City Clerk, submitted a proposal to Iowa State asking what kind of improvements could be made to the city s distribution system to have a more reliable and efficient system and to reduce costs for Breda s customers. The senior design team met with Diane Lucas and the two maintenance employees in charge of maintaining Breda s distribution system Dick Steinkamp and Roger Ludwig. Concerns that were discussed during the meeting were the need of an update to the distribution system, understanding low cost improvements that could be done, how to reduce energy costs, and reliability of the power distribution system. 0.2 Problem Statement An economic analysis of the overall power distribution system of Breda, Iowa is needed to determine energy costs associated with generation, distribution, and transmission. The cost analysis will identify problem areas which are in need of revision, including areas where heavy losses are occurring. This analysis also needs to include an analysis of Breda s revenues and now to encourage high demand customers to lower costs and power consumption. A study of ways to improve system reliability and to minimize interruptions is needed. Breda has had several weather related outages in recent years. An engineering study needs to be done to show why the outages occur and how they can be prevented in the future. 3

5 Finally, a study of how upgrades to the electrical system could be cost effective in the long term. This includes how new technologies and lower resistance conductors can lower losses and long term costs. 0.3 Acknowledgments Anne Kimber (Director of Energy Services at Iowa Association of Municipal Utilities): Providing information energy markets and where to go to start a cost assessment of the distribution system. Diane Lucas (Breda City Clerk): Providing billing statements for the city of Breda. Rodger Ludwig and Dick Steinkamp (Breda City Employees): Provided technical data on the city s distribution system. Glenn Hillesland (Retired Adjunct Professor, Iowa State University): Technical reference and expert in Distribution systems, also worked on previous Breda project. Kenneth Kruempel (Contract Associate, Iowa State University): Technical reference and assisted in intial meeting with city employees. Greg Vaselaar (Field Representative for WAPA): Provided WAPA charges, WAPA background information, and contractual information. 4

6 1.0 High-Level Design 1.1 Project Goals Assess current energy costs Analyze system reliability Lower demand Provide a report on upgrades that are long term cost-effective Analyze equipment maintenance schedule Figure 1. Our goals 5

7 1.2 Conceptual Diagram Figure 2. How regulators are used in distribution feeders and a chart of voltages vary by the distance from the substation. Part of the project will be addressing this issue. 1.3 Functional Decomposition Overall Function The main function of our system design will be focused on improving the efficiency of the city s power distribution system. This project aims to analyze the overall losses and thoroughly monitor every aspect of the system. The city of Breda can choose to modify or act accordingly. Sub-functions In order to achieve the main function of this design project, we have decided to cover the following sub-functions individually: 6

8 Reliability The reliability issues within the system are mostly connected to distribution lines and circuit protection. To help Breda build a more reliable system, this project will examine ways to better protect the circuit and aid in power recovery in case of faults. Specifically, the city is using fuses to protect all of its power distribution system, which can be dangerous to replace when fault happens and it can cause unbalanced voltages to a three phase system. We will explore the possibility of replacing the fuses with circuit breakers, so the system can automatically open and close the circuit, increasing efficiency. Load Management & Voltage Regulation The city has been charged with incremental demands for the past few years. One of the charges identified was excessive peak load demand. The city uses an old computer program to manage the peak load in the city and its effectiveness will be explored. Through this project we are hoping to improve their method of managing the peak load to eliminate additional charges. Breda also has problems maintaining proper voltage levels, either for their residential customers or industrial customers during the peak time. This project is going to inspect their voltage regulating devices and make sure their voltage levels don t dip heavily when the peak load occurs. Losses One of biggest expenses for the distribution system is losses. This project is going to build an ETAP model which helps us to simulate the system and locate where the major losses might be. 7

9 1.4 Specific Functional Requirements Acceptable running limits on the power system: Voltage levels must be maintained on the entire distribution system. Our chosen level is +/-.2 V p.u. on a 120V basis. Properly maintained voltage increases the overall reliability of the system. If voltage dips too low, temporary power outages can occur. If voltages spike, damage can occur to both consumer and utility equipment. Starting electric motors can cause voltages to dip. We must insure heavily inductive loads do not result in voltage dips in the system. Power factor must be maintained as close to unity as possible. Power losses due to current in the system equal the current squared times resistance. Inductive loads use large amounts of reactive power. This reactive power draws increased current causing increased power losses. This is counteracted by installing capacitors which decrease the amount of reactive power consumed. Our chosen acceptable loss is +/- 5% of unity power factor. The current maximum load on the system is approximately 1170kW. Breda is planning expansion on the system in two areas, increased industrial load and increased residential load. The increased industrial load comes from grain drying operations only needed in the fall months. The increased residential loads come from a new subdivision planned in the near future. We will be analyzing what a 5% increase in demand will cause in stresses on the system. All suggested improvements to the system must be cost-effective. We have purposed all improvements must pay for themselves with decreased power losses within a period of 15 years. All regulators and transformers must be operated within their posted limits. These limits are located on the equipment and will need to be catalogued and included in our model. 8

10 1.5 System Analysis City of Breda Electrical Distribution System The current system has the following areas: Transformers: The city utilizes several different transformers to meet the needs of its customers. These include large 3-phase transformers that convert power from its transmission level of 12.4 kv to lower distribution levels. They also have both pad mounted and pole-mounted transformers that reduce voltages from distribution levels to 120 V or 240 V for delivery to its customers. We will be analyzing each transformer to ensure it is operating within its rated power (kva) ranges. Conductors: Conductors refer to the metals used in distribution lines to transfer power. Overall larger distances large losses can occur within these lines. We will be gathering data on all the conductors to use in our model. This data includes resistance and impedance (Ohm-mile). This data will be used to supply Breda with a report on the losses in the system. Voltage Regulators: Voltage regulators are used to maintain proper voltage levels throughout the system. They utilize autotransformers that can be adjusted as voltage levels change based on demand. These regulators will be analyzed within our model to ensure its operating properly within allowed voltage levels. 3-phase Customers: Breda has a few industrial loads that utilize 3 phase power. The multiple phases allow the customers to receive relatively large power without putting large stresses on any single phase. Since these customers are large consumers their loads will be analyzed to see how they are affecting the system. Single-phase Customers: The vast majority of customers in Breda are single phase customers. Within our model these customers will be modeled as similar loads using their average power demands. This is to greatly simplify our model and the amount of data we need to acquire. Municipal Customers: Breda has several city-owned loads that need special consideration. This includes the fire station, city hall, and the city pool. These loads will be analyzed individually because lower their demand translates directly into energy savings for Breda. 9

11 1.6 Technology Platforms/Choices ETAP power distribution software allows has Network Analysis capabilities, ETAP offers powerful analysis modules to build Distribution Systems design. ETAP supports balanced or unbalanced 3-phase, 2-phase and 1-phase systems for radial, looped or meshed network including per-phase voltage drop and power flow analysis, fault calculations, Protective Device Coordination (ETAP Star) Software, Optimal Capacitor Placement Software, Optimal Load Flow Software, Reliability Assessment Analysis Software, Switching Sequence Management Software, and more. Balanced and unbalanced load flow and voltage drop analysis Protective device coordination including extensive recloser modeling and sequencing Optimal capacitor placement and sizing to minimize losses and improve voltage profile Comprehensive load modeling Advanced reliability assessment and distribution reliability analysis Switching sequence management for load transfer simulations GIS Map interface Source: Design Tradeoffs Our design utilizes modeling each small load similarly. This cuts a great deal of time from the initial data collecting and entry of load information. The tradeoff is we lose a small degree of accuracy within our model. Purposing all improvements must be cost effective within 15 years eliminates some useful upgrades, but allows the improvements to be justifiable in the short term. We are somewhat limited in what other areas we can cover because making a oneline diagram is time-consuming 10

12 2.0 Detailed Design City of Breda Electrical Distribution System 2.1 System Architecture Create One-Line Diagram Enter Data into ETAP Simulation of Power Flow Isolate Problem Areas Purpose System Changes Test the Model Analyze Cost-Effectiveness Present Report Figure 3. The major steps involved in the distribution project. 11

13 2.2 System Architecture Schematic Figure 4. This is the one-line diagram of city of Breda. There are in total 35 transformers and each of them is located at the point where is labeled with bus. There are two types of transformers are using in city of Breda pad mount and pole transformer. There are two main distribution lines going through the city and 5 poles drawing the power from those two distribution lines. One of the distribution lines is at the east part of city of Breda going from north to south. The other distribution line is at the west part of Breda mainly supply power to snappy popcorn company. In the middle area where is the residential part, is using single phase constructer and the eastern part of Bread is using three phase frame. In the eastern part there are industries, commercial business, and public recreations such as water pool and tennis court. 12

14 2.3 Design Process City of Breda Electrical Distribution System The project has been broken down into eight unique steps with unique goals. Phase 1: Data collection to create one-line diagram Description: Goal: During this stage data will be collected on the city s transformers, conductors, poles, and loads. This information will be used to make a one-line diagram of the entire city s electrical distribution system. An accurate one-line diagram that can be used directly to enter information in ETAP. Completion: May 10, 2011 Phase 2: Enter Data into ETAP Description: Goal: The information on the one-line diagram will be entered into ETAP. It will be double-checked to ensure all aspects of the project are correctly entered and the resulting model is accurate. An accurate and working model of the distribution system that can be used for the later stages of testing and modeling. Completion: August 20, 2011 Phase 3: Simulation of Power Flow Description: Goal: Simulate power flow under various conditions including peak demand, highly inductive loads, low-demand loads, and single phase faults. This stage is modeling only under existing conditions. An accurate description of losses under existing conditions. Completion: September 1, 2011 Phase 4: Isolate Problem Areas Description: Use the model to look for problem areas. These include areas with high losses, large demand loads, poor voltage maintenance, or highly inductive loads. 13

15 Goal: Locate several areas that could be potential problems. Completion: September 14, 2011 Phase 5: Purpose Changes to the System Description: Goal: Find and suggest several areas to make changes in the system. These could include conductor or transformer changes, loadmanagement changes, or reactive power adjustments. Create a list of changes that can be re-modeled. Completion: September 21, 2011 Phase 6: Test the model with the changes. Description: Goal: Make the appropriate changes to the model within ETAP and run all the previous test cases. Look for improvements in voltages and demand. A system analysis of the new changes included a document of how the proposed improvements help the system. Completion: October 14, 2011 Phase 7: Verify the Cost Effectiveness of the Changes Description: Goal: Analyze all the suggested improvements for their cost effectiveness. Our standard is they must play for themselves in 10 years to be cost effective. A list of all improvements that could be made and how they would save money in the long-term. Completion: November 1, 2011 Phase 8: Present Report to Breda Description: Goal: A written report will be completed with analysis of all the previous areas. Other topics listed below will also be covered. A presentation to the city clerk and council will also be done. A written and oral presentation. 14

16 Completion: Dec 11, 2011 Other Areas of focus: Description: Goal: We have picked a few other areas to explore that are not directly related to this design process but could prove to be useful to Breda. These include an economic breakdown of transmission costs, costs associated with Midwest ISO regulation, distribution maintenance, and load reduction. A deliverable report of each area including cost breakdowns. Completion: November, Gantt Chart Figure 5. Gantt chart showing the time frame for each phase of design and the leader in charge of that area. 15

17 2.5 Member Involvement City of Breda Electrical Distribution System Estimated Individual Team Member Effort (hours) Task: Member: Totals Anthony David Chris Rui Totals Figure 6. Estimated time breakdown of each phase. 2.6 Final Report Structure Deliverables: Reports: Current system power losses Current system transmission losses Suggested improvements and their cost-effectiveness Transmission cost breakdown Demand billing costs and reduction savings Distribution maintenance plan Load-management effectiveness MISO associated costs Presentation: An oral presentation delivered summarizing the findings to a largely nontechnical audience. Model: An ETAP model that can be used by future distribution reviewers. 16

18 3.0 Testing and Evaluation Plan 3.1 Test Plan Tests of the model will be run on ETAP. And will be broken into several categories. Test 1: Normal Operating Conditions The model will be evaluated under normal average loads to evaluate performance. The average demand is approximately 850kW. Assuming a distributed load, we will use this as a base for system performance. Voltages will be analyzed along the distribution feeder to look voltages outside the acceptable range of +/-.2 V per unit on a 120 V base. Test 2: Peak Load The peak load that the City of Breda experienced in 2010 was 1172 kw in January. The model will be fed the conditions of this load. Once again we will be looking for voltage drops outside the acceptable range of +/-.2 V p.u. Also all transformer and conductors will be analyzed to ensure they are functioning within their posted kva values. Overall losses will be cataloged. Test 3: Inductive Loads The City also experiences high demand loads during the summer months of July and August. Although generally not as high as the winter loads, these loads are unique because they come from largely inductive loads (air conditioners). Inductive loads can present problems because they require a larger current to serve them, which leads to larger losses in power distribution. We will be looking at the loads to ensure there are no significant voltage drops. The city also installed a switchable capacitor bank to counteract the effects of this largely inductive load. We will be running the simulation with both the bank switched on and off. With the bank on we need to verify that the power factor is within 2% of unity. Test 4: Single-Phase Faults 17 We will be testing the ability of the system to maintain functionality under singlephase fault conditions. At various points within the model one phase will be

19 allowed to fault to ground. The other two power phases will be looked at to confirm that they maintain acceptable voltage levels. This assessment of the system s reliability will be included in the final report. 3.2 Simulation We will be collecting information on modern conductors and transformers. This information will be used to replace the current equipment Breda processes on our model. The model will then be tested again under the previous test cases. The results of the simulation when be compared to the previous test cases to see how new equipment could improve overall system performance. The cost of new equipment would need to be considered as part of this report. Each replaced component will be analyzed in the following manner for cost-effectiveness. Component Cost Power Loss Savings (kw-h) Estimated Savings per month Years to Recoup Cost Equipment changes that require more than 15 years to recover costs will be ignored. If there are voltage problems we will be inserting voltage regulators into the simulation and running a new simulation. The regulators will be included in the final report along with other recommended upgrades. A final copy of the ETAP model and one-line diagrams will be included in our final report to the City of Breda. This will allow any future energy assessments done on the equipment to be completed quickly. 18

20 4.0 Team Member Information Faculty Advisor: Dr. James McCalley Professor Electrical and Computer Engineering 2210 Coover Ames, IA Client: Diane Lucus City Clerk-City of Breda, IA PO Box 129 Breda, IA Team Members: David Mindham Christopher Krantz 3310 Emerald DR 1823 Duff Ave Ames, IA Ames, IA Anthony Tong Rui Bai 141 University Vlg Apt C 2721 Luther DR Unit 8 Ames, IA Ames, IA ttong@iastate.edu bairui@iastate.edu 19