Managing Energy Assets - Essay Example

? MANAGING ENERGY ASSETS by goes here] Presented to [your goes here] [your goes here] s [city and state] [due date of the paper] TABLE OF CONTENTS CONTENTS PAGE # 1. Introduction 1 2. Oil Filled Transformers 1 3. Transformers at the Substations 3 3.1 Step-Up Transmission 5 3.2 Step-Down Transmission 5 3.3 Underground Substation 6 3.4 Distribution Substations 6 4. Types of Monitoring Equipment 6 4.1 Dissolved Gas Analysis 9 4.2 Partial Discharges 10 4.3 Temperatures 11 4.4 Qualitrol 509 and 505 Intelligent Transformer Monitors 11 5. Proposed technique and Justification for the Technique 12 6. Conclusion 13 7. References 14 Monitoring Transformer Performance 1. Introduction Before going to present the proposal for instruments and techniques that can be used to monitor the condition of a transformer, let us get a better understanding of what transformer actually is and why is it important to supply electricity through the network. A transformer is an electric device, which is designed to convert alternating voltage from one level to another usually from high voltage to low voltage. Transformers work on the principle of magnetic induction. Dickinson (2009) states, “Transformers under load generate heat due to winding (copper) and core losses occurring during operation”. Transformers are solid-state devices, as they have no moving parts in them. The step up or step down in the voltages is the main use of every transformer. 2. Oil Filled Transformers There are two main categories of transformers, which include dry type and liquid filled transformers. In this paper, we will prepare a proposal for oil-filled transformers at substations, which are one of the main types of liquid filled transformers. Oil filled transformers make use of cellulose paper and mineral based oil in their insulation systems. This combination of cellulose paper and oil is very good for the working of transformers because they provide remarkable dielectric and thermal properties at a low cost. About this combination, Dickinson (2009) states, “So popular and effective are these units, that all other transformer designs are judged in relation to them”. For outdoor usage, oil filled transformers are the best ones among all types of transformers because of their low purchase costs and thermal and dielectric properties. The inclusion of mineral oil in the oil-filled transformers although makes them flammable but the low cost associated with these transformers makes them a good choice for power distribution companies. The low purchase cost of oil-filled transformers makes them an attractive choice for all types of power distribution companies. Dickinson (2009) asserts, “Oil-filled transformers, thanks to their lower purchase costs, find applications in literally every sort of power distribution”. The only weakness of mineral oil filled transformers is flammability, which is the reason why these transformers are allowed only in outdoor locations because outdoor locations are considered safe for the installation of oil-filled transformers because of availability of proper fire protection mechanisms. Experts suggest that the consumers should always buy oil-filled transformers from trusted manufacturers because they ensure lowest level of flammability in the oil-filled transformers. Flammability is such a weakness of oil-filled transformers that most of the power distribution companies seek good replacements of oil-filled dtransformers, which should be non-flammable. This is the reason why dry type transformers have been popular for decades because they are completely free from this weakness. Dry type transformers make use of high temperature insulation instead of mineral oil which them a risk free option for power distribution companies. “Dry type transformer construction uses high-temperature insulation that exceeds the ratings of cellulose or 'O' and 'K' class fluids” (Dickinson 2009). There is no risk of flammability in dry type transformers, which makes them less dangerous for indoor installations. 3. Transformers at the Substations McGee (n.d.) states, “A transformer substation is a location where electric power is converted from bulk power to local power or vice versa”. Substations are very important for the proper working of a transformer because they are the equipments, which convert the electrical current in order to allow it to move to the logical grid or through the bulk power system. Substations are either small or large and they change high voltages to the low level in order to bring it in our daily use. Large substations comprise of more than one transformers and dozens of related equipments whereas small substations have just one transformer and related equipment. The main purpose of the substations is to covert the electricity into usable form and that task cannot be completed without a transformer. When a power plant generates some electricity, it is known as bulk power, which is not a usable form of electricity. “Bulk power moves through high-voltage transmission lines and enters a transformer substation” (McGee n.d.). It is the role of the substations to convert the bulk power into useable form before letting the transformers supply that power to the homes and to the companies. Transformers, which are there in the substations, step transmission voltages that are in the very high level of voltage down to the distribution voltage level, which is typically less than 10,000 volts (Brain n.d.). The main role of every transformer is to convert high voltage of electricity into lower and acceptable levels. Transformers are the main electric apparatus located at the substations and their role in the provision of required level of voltage to the end users is very important. Without best quality transformers, conversion of voltage levels cannot take place in an appropriate manner. Transformers of substations not only convert bulk power into the useable form of energy but also converts back the usable form of energy into the bulk power and sends it to the power generation system if the delivered power becomes more than what is actually required. It is because the substations cannot store the electricity of this type, so they need to convert it back into the bulk power and send that to the system. This is a very good point regarding transformers because they not only convert high voltages to low levels but also reconvert extra energy into bulk power in order to save it for future use. Apart from these functionalities of the transformer substations, there exist some other types of substations, such as, collector substations and railway substations, which perform some specialized tasks. McGee (n.d.) defines collector substations and states, “Collector substations connect to a power generation system that relies on sporadic or uneven factors such as wind or water power”. These substations covert the power generated from wind or power systems for bulk power transmission. Similarly, railway substations receive bulk power and use it for different purposes. Manufacturing companies design transformer substations for a wide range of purposes, which include different kinds of industrial and commercial purposes. The liquid filled transformer substations play a very important role in the overall supply of electricity throughout the network. The importance of a transformer at a substation can be known by the fact that without it, the conversion of power from bulk to local power cannot take place. A liquid filled transformer substation is a very popular type of substation and is being widely used for many manufacturing facilities, hospitals, offices, schools, and shopping malls. At substations, transformers play a crucial role in the transmission of electricity through the network. A substation is a high voltage electric facility, which is designed by the manufacturers to shift alternating current voltage from one level to another. Another purpose of substations is to convert direct current into alternating current and alternating current into direct current. There are four main types of transformer substations, which have different functions and specifications. All of them meet some specific needs and requirements based on their design and imbedded technology. Let us discuss the specifications of each of the four types of substations in order to get a better understanding of how the operations of the transformers at each substation differ from the operations of others. 3.1 Step-Up Transmission “A step-up transmission substation receives electric power from a nearby generating facility and uses a large power transformer to increase the voltage for transmission to distant locations” (PTR 2007). Manufacturers make use of a transmission bus in order to distribute electricity to other transmission lines. A step-up transmission substation may have a circuit breaker switch, which is used to switch transmission circuits in and out of service when they are needed, or it can also have emergencies that require the shutdown of power to retransmit the electric power (PTR 2007). The typical voltage levels used in step-up transmission substations are high voltage ac, extra high voltage ac, ultra high voltage ac, and direct current high voltage. 3.2 Step-Down Transmission This type of substation is located at switching points, which are there in the electrical grids. They act as the sources for distribution or sub-transmission lines and they connect different devices present in the grid. This kind of substations is able to make a conversion between transmission voltage and sub-transmission voltage. “The step-down substation can change the transmission voltage to a sub-transmission voltage, usually 69 kV” (PTR 2007). This conversion makes the sub-transmission voltage lines serve to the distribution substations. 3.3 Underground Substation Underground substations change the voltage levels to low levels and are located near the end users of the electricity provided by the transformers. Some of the main parts of underground distribution substations include conduits, manholes, transformer vault, duct runs, high voltage cables, and transformers. The typical distribution of voltages varies from 34,500Y/19,920 volts to 4,160Y/2400 volts in underground distribution substations (PTR 2007). 3.4 Distribution Substations The work of transformers at distribution substations is somewhat same as underground distribution substations. They are also located near the end users and change high-level voltages to lower levels for the use of end users. One major difference between the two types of substations is that of wires. In distribution substations, the wires are not under the ground as in case of underground distribution substations. The level of voltage between the conductors is usually 34,500 volts whereas the level of voltage between the neutral ground and a one-phase conductor is usually 19,920 volts (PTR 2007). This kind of substations distributes power to a wide range of industrial and residential customers. 4. Types of Monitoring Equipment Manufacturers of transformers make use of different types of monitoring equipments in order to ensure safe and secure working of the transformers (Bengtsson 1996). Those monitoring equipments monitor overall working of the transformers and report all sorts of bugs present in the transformers to the concerned authorities, such as engineers. “Protection of large power transformers is one of the most challenging problems in the power system relaying area” (Kasztenny & Kezunovic 1998). To overcome this challenge, the engineers analyze the level of danger associated with the faults and take corrective measures to remove those faults. “Online diagnostics and online condition monitoring are important functions within the operation and maintenance of power transformers” (McArthur, Strachan & Jahn 2004). Manufacturers of transformers ensure reliable and secure supply of electricity to the end users. “Knowledge of the health of power transformers is important to prevent high costs caused by failures and to maintain the quality of the service” (Sanz-Bobi et al. 1997). However, some faults are likely to occur at some stage in the life of the transformers. “Transformers are such a component; they are often an essential link in the distribution network” (Van, Gulski & Smit 2002).The most common fault that can occur in most of the transformers is partial discharge. As the result of this fault, power outages can occur. Partial discharge can also harm the electric products of the end users. “Considerable costs are associated with transformer failure, especially if such failure happens without warning, and no action for a planned outage can be taken” (PCT 2009). “Mechanical and electrical faults may arise following short circuits, local overheating at hot spots or leakage flux” (Pahlavanpour & Wilson 1997). Engineers need to correct such faults in the early stages because of such faults are ignored; they can cause severe damages to the end users. “Monitoring the transformers for problems before they occur can prevent faults that are costly to fix and result in a loss of service” (Wood et al. 2003). Some of the main reasons due to which partial discharge can occur in the transformers, include unfriendly operating conditions for the transformers, over age transformers, and improper monitoring of transformers. External UHF couplers can be fitted to autotransformers in order to develop new transformer monitoring techniques (Judd et al. 2000). “Different defect types can be distinguished on the basis of their phase-resolved patterns measured at UHF” (Cleary & Judd 2002). In the monitoring of transformers, various factors are involved, such as, data acquisition, analysis of data, and link development between electricity failures and data measurement analyses. Engineers make use of such monitoring equipments, which accurately analyze all aspects of the working of transformers and do not ignore any fault that they find in the transformers. Manufacturers of transformers put monitoring equipment permanently on the transformers in order to ensure continuous monitoring of the working of the transformers. Some of the most common and reliable monitoring parameters that are being used all over the world include oil temperature, operation of cooling fans, moisture levels, and electrical load levels (PCT 2009). Different electricity providing companies set different parameters for the monitoring of transformers’ operations. Observing the oil temperature and electrical load levels are two of the most reliable options to know whether everything is going fine with the transformer or a corrective action is needed. Aging of transformers is one of the most critical problems associated with transformers. “The aging infrastructure of large GSU and EHV power transformers built in the `60s and `70s poses a serious strategic issue for users worldwide” (Ward & Lindgren 2000). Most of the transformers face faults due to their over age and improper installation of the monitoring equipments. There also exist some other reasons for improper working of transformers, such as, improper management and installation of unreliable parts on the transformers. Therefore, manufacturing companies need to install efficient monitoring equipment on the transformers in order to ensure safe operation of the equipment. “There are plenty of proper monitoring methods to evaluate the condition and possible incipient failures of a power transformer” (Pylvanainen, Nousiainen & Verho 2007). Online monitoring methods include gas-in-oil analysis, partial discharge, and temperature measurement methods (Leibfried 1998). Let us discuss these methods of monitoring the performance of transformers in some detail. 4.1 Dissolved Gas Analysis “An established diagnostic method, gas-in-oil analysis involves analyzing the types, concentration and production rates of generated gases” (PCT 2009). In this method, engineers analyze different aspects of gas in order to identify faults in the transformers. “The analysis of dissolved gases is a powerful tool to diagnose developing faults in oil-filled power transformers” (Cardoso & Oliveira 1999). In this method, certain key gases present in the transformers are monitored and quantified (Muhamad et al. 2007). Analyses of the types, production rates, and concentration provide enough data to the analysts related to the working of transformer. The transformer monitoring team relates generation of different types of gases with different types of faults present in the transformers. For example, arcing is associated with the generation of acetylene whereas overheated cellulose is associated with the generation of carbon oxides in the transformers. Using the gas concentration of a gas chromatograph and catalytic gas sensor, the apparatus determines whether there is a fault in a transformer or not (Tsukioka et al. 1986). In the process of transformer monitoring using this method, engineers take oil samples from the transformers at regular intervals and then extract the gases that are present in the oil samples. Manufacturers make use of Online Gas Sensors to provide electric companies with full-time monitoring of the transformers. Online gas sensors are able to detect changes related to gas present in the transformers. These sensors provide a great help to the monitoring teams as they can sense every kind of fault in the working of the transformers. The sensors, after identifying the faults, report them to the engineers who analyze those changes or faults in the production of gases and take corrective actions. The sensors used in this technique are highly reliable which can detect a wide variety of faults present in the transformers. This is the reason why this technique is being used by a large number of electricity providing companies. 4.2 Partial Discharges Partial discharge is one of the main problems associated with the working of transformers. As discussed earlier, partial discharges can lead to power outages. Partial discharge can also harm the electric products of the end users. Electricity providing companies make use of Partial Discharge Testing to examine overall integrity of the transformers. Partial discharge monitoring is somewhat more expensive and complicated as compared to discharge gas analysis. Partial discharge testing is a good method to monitor the performance of a transformer. Although this method of transformer monitoring is not very suitable for online monitoring due to its expensiveness, but it provides a number of considerable advantages to the companies, such as, identification of partial discharge at an early stage and identification of the level of discharge from a transformer at one time. This method of monitoring the performance of transformers also makes use of sensors, which identify the partial discharges and report those discharges to the concerned authorities. Acoustical sensors are the new development in the area of partial discharge sensors. These sensors are fitted externally and are very cost effective as compared to other sensors that work for the identification of partial discharge. The only disadvantage of acoustical sensors is that they are fitted externally which makers them prone to disturbances that may occur due to rough out-of-doors substation environment. However, the fact is that manufacturers are doing research for the development of such outdoor sensors, which should be able to cope with rough outdoor environment. 4.3 Temperatures The hot spot of the windings is the load capability of the transformers. “Hot spot is typically calculated indirectly from measurements of oil temperatures and load current” (PCT 2009). The hot spot tells the transformer management authorities that whether the load of electricity on the transformer is normal or not. Some companies also make use of fiber optic temperature sensors that are placed on the windings. Two types of fibers are used to measure the temperature of the transformer. One type of fiber calculates the temperature at a single point whereas the second type calculates the temperature along its own length. Single point fiber is low cost as compared to distributed fibers that can only be used to monitor the temperature of new transformers. 4.4 Qualitrol 509 and 505 Intelligent Transformer Monitors It is also a reliable and one of the latest developments in the field of transformer monitoring. This device has many new capabilities, which make it a good option to choose for the monitoring of transformers. Some of the most considerable capabilities include event recording, data logging, and dynamic loading analysis. These capabilities help the electricity companies manage their transformers over a long time. “Literatures are accumulated on developing intelligent CM systems with advanced practicability, sensitivity, reliability and automation” (Han & Song 2003). Another advancement, which is Qualitrol 505, provides more advanced and accurate monitoring of the transformers. Condition assessment technique can also be used to monitor transformer’s performance. This technique uses signatures that are installed on OLTCs in distribution substations and the online monitoring systems collect those signatures (Kang & Birtwhistle 2001). “An onload tap changer (OLTC) is the most maintenance intensive subassembly on a power transformer” (Kang & Birtwhistle 2003). Evolving wavelet network is also one of the main types of transformer condition monitoring. “EWNs possess far superior diagnosis accuracy and require less constructing time than the existing methods” (Huang, Y. & Huang, C. 2002). These were some of the main techniques being used for monitoring the performance of transformers. New and advanced technologies are also coming in the field of transformer monitoring which will ensure more safe and dynamic approach to ensure reliable working of the transformers. 5. Proposal and Justification for the Technique I would like to propose an evolutionary programming based fuzzy system development technique in coordination with Dissolved Gas Analysis method to review the maintenance regime for the oil-filled transformers at substations. The reason is that this technique makes use of Online Gas Sensors, which will provide electrical distribution utility with continuous monitoring of the transformers. The online gas sensors will be able to detect the changes related to gas present in the transformers. These sensors will also provide a great help to the monitoring teams, as they will be able to sense every kind of faults present in the transformers. The evolutionary programming based technique is superior in performance not only in developing the diagnosis system but also in identifying the faults in transformers (Huang , Y., Yang & Huang, C. 1997). This is the reason why I have found this technique the most suitable one for the electrical distribution utility to review its maintenance regime for the oil-filled transformers at substations. 6. Conclusion Summing it up, role of transformers at substations is very important as they not only convert bulk power into the useable form of energy but also converts back the excessive usable form of energy into the bulk power and sends it to the power generation system. Continuous monitoring of oil-filled transformers is necessary in order to make them useful and trouble free for a long time. There exist different techniques to monitor the performance of oil-filled transformers. Electricity companies make use of those techniques based on their advantages and levels of reliability. To review the performance of oil-filled transformers at substations for an electrical distribution utility, I have decided to propose evolutionary programming based fuzzy system development technique because it is superior to all other techniques in the development of diagnosis systems. References Bengtsson, C 1996, ‘Status and trends in transformer monitoring’, IEEE Transactions on Power Delivery, vol. 11, no. 3, pp. 1379-1384, viewed 16 July 2011, http://www.lib.monash.edu.au/tutorials/citing/harvard-journals.html Brain, M n.d., How Power Grids Work, viewed 16 July, 2011, . 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