EE 3070 Paper Follis

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Louisiana State University *

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2070

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Electrical Engineering

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Jan 9, 2024

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LOUISIANA STATE UNIVERISTY Oncor Electric Delivery Internships EE 3070 Engineering Practice – Scalzo Jason Follis

To qualify for EE 3070 I have worked two summer internships for Oncor, an electric delivery company based out of Dallas, Texas. In the summer of 2012 I worked at the East Distribution Operating Center or EDOC in Irving for the Smartgrid division. In the summer of 2013 I worked for Power System Protection located in the Electrical Service Building or ESB in downtown Fort Worth. While working for Smartgrid applied systems, I worked primarily with Greg Nichols under supervisor Joe Wolf. I worked under supervisor Todd Rosenberger while working with the Power System Protection workgroup. The first summer I was working for Smartgrid Applied Systems in the East DOC which The first project I was asked to work on was related to the results of a recent internal audit of Oncor’s systems. One of the findings in this audit was that the users of certain applications were never required to reset their passwords on any reoccurring basis. In order to comply with the audit, a system was needed to allow passwords to expire, be reset, and be recovered. I was tasked with building a website in C# to communicate with both existing and new Oracle SQL databases which would allow mobile users to reset their passwords for their mobile applications. While the task was simple, the execution required significant consideration. The users resetting their passwords were typically field workers whose computer skills may not be the best so the process needed to be easy to follow. Additionally although this would be an internal webpage, it would be communicating with SQL databases, therefore considerable sanitation of input values was necessary. Sanitation of inputs is necessary to prevent malicious code from being input instead of normal values which can create a security risk. The next project while working for SmartGrid involved the testing of new software which was to be incorporated into the existing dispatcher interface. Prior to the summer, a factory acceptance test of Siemen’s Distribution Network Analysis or DNA software had occurred and been passed. During the summer, the software needed to go through SAT or Site Acceptance Testing. Siemens had provided a test book with steps that needed to be executed and the results verified Due to the circumstances, SAT testing required a lot of coordination and proper communication to ensure responsible parties could resolve the variances that SAT testing revealed. I was the primary owner of the SAT issues list which contained a list of variances, the status, severity, author, date, section of software, summary of the issue, and comments. I also sent out daily testing summaries to the testing team as well as informing management of the progress.

For the second summer with Oncor I had requested to be in the Power System Protection group if possible and fortunately for the summer of 2013 I worked for that division in the Ft. Worth offices. Prior to the summer I had completed the Power System Protection lab at LSU so I was familiar with some of the concepts and different types of relays. For the first week or so while my computer access was being finalized I was reading up on resources for power system protection in addition to reading and understanding Suburban IV, an Oncor specific protection standard and implementation, for protection of their systems. While I cannot discuss details it was very interesting to read about a highly engineered standard which could be implemented for both new installations and interface with older systems as well. While Suburban IV had a lengthy technical write-up I was also given the logic diagrams which provided great insight into the programming and connection of the various microprocessor relays used. Once I could understand what Suburban IV was supposed to accomplish I was introduced to relay functional diagrams, which I now understand to be the core to the language and design of designing power protection systems. It was difficult at first but being able to connect the ideas of Suburban IV, the logic of the system, the relay functional drawings, and the detailed schematic diagrams allowed me to understand and review designs. While it took a couple of weeks to acclimate fully to relay functionals and full schematic diagrams, I was given other tasks as well. One of the first assignments I had was to update a list of switches which could and could not be operated to de-energize 345 kV Autotransformers. Certain autotransformers due to their physical configuration could draw an exciting current higher than the interruption capability of motor operated air switches. If the wrong autotransformer air switch was operated an arc would likely form which could damage equipment or personnel. To update this list I had to first determine which 345 kV autotransformers on the system were either new or replacing old autotransformers. Once the serial number of new transformers were determined I needed to find the transformer test report provided for each specific transformer. Once the data was collected the actual exciting current was calculated using the following formulas: Power BASE V BASE X √ 3 = I BASE % ExcitingCurrent 100 X I BASE = Actual ExcitingCurrent It was necessary to find the power base and % exciting current from the transformer test reports the nominal voltage base is 345 kV. The actual exciting current was compared to the current an air switch on Oncor’s network could successfully interrupt which is 3.25 amperes, calculated from a formula provided by IEEE C37-36b-1990. With the calculations completed if the exciting current was greater than 3.25 amps the autotransformer was flagged. This list was last updated in 2011 and over 10 new 345kV autotransformers were added. This list, while a fairly simple task required me to learn how to interact with other divisions of Oncor to determine new autotransformer installations. Also I became familiar with autotransformer test reports and the sort of information manufacturers supply in addition to the records system Oncor had in place.

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While many of the engineers were busy with settings for new installations, substation retrofits, designing new protection solutions, and more sometimes a review of older settings is necessary. Power System Protection at Oncor not only performs the conceptual design to determine the hardware necessary to protect equipment but also issues calculated settings for the relays to operate properly. While these settings are accurately calculated when issued, it is possible for settings overtime to become insufficient for the systems they are meant to protect. In this day and age power has become something as a necessity growing in consumption year after year. As power consumption increases it could cause settings to become obsolete, the overcurrent settings of twenty years ago may be the nominal setting of today. If settings are not reviewed and updated they can lead to unnecessary disruption of service, potentially costing both Oncor and customers money. My main project as an intern was to review the settings across Oncor’s entire network for a specific set of electromechanical relays. The relay settings in question were for the PVD type bus differential relay and their backups. The PVD type relay was produced by General Electric and is a single phase, high impedance differential relay, which was an instantaneous type operation. Interestingly PVD relays only have two settings: a voltage operated 87L setting and a high speed overcurrent 87H setting. The overcurrent 87H setting is actually obtained by analyzing a curve dependent on the 87L setting. While this leaves only the 87L value to be calculated, the considerations and calculations are far from trivial. The PVD relay is intended to protect an entire substation bus by using a differential circuit to detect for fault conditions. The general idea for bus differentials is that all current flowing into the bus must equal the current flowing out of the bus. If a fault occurs on the bus in-between breakers, current will flow from the output and input simultaneously to ground, creating a difference across the relay’s operating coil which will cause a trip. However, if instead of a fault occurring on the bus and instead close in on a single feeder the ideal operation would be for only that feeder’s relay to trip and isolate that fault from the bus. This scenario, a close in fault on a single feeder introduces the coordination issue that the 87L value must be calculated for. To calculate the proper 87L value for a PVD relay one must know a lot of information about the current transformers (abbreviated CT) used for the PVD circuit. This information includes researching CT