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Improving Operation and Maintenance of Substation Equipment Using Operational Data from Protective Relays

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Improving Operation and Maintenance of Substation Equipment Using Operational Data from Protective Relays Improving Operation and Maintenance of Substation Equipment Using Operational Data From Protective Relays Mohamed Nabil Ali Schweitzer Engineering Laboratories, Inc. Presented at the GCC Power 2019 Conference & Exhibition Muscat, Oman October 27–29, 2019 IMPROVING OPERATION AND MAINTENANCE OF SUBSTATION EQUIPMENT USING OPERATIONAL DATA FROM PROTECTIVE RELAYS Mohamed Nabil Ali* Schweitzer Engineering Laboratories, Inc. USA Summary—Most modern digital protective relays can limited to circuit breakers, transformers, and motors. easily monitor power system equipment and provide Through monitoring of operation data archived in detailed data concerning their performance and condition. protective relays, operation and maintenance engineers can These data can be used to develop a maintenance program that ensures equipment is serviced as required and that retrieve useful information that reflects the accurate status preventive actions are taken to avoid any possible failure. of the equipment. Efficiency improvements could include Protective relays provide extensive information that “reading key equipment data from the relay and displaying can be retrieved and linked with operational and or generating work instructions; reducing unscheduled maintenance topologies, either manually or automatically. downtime from equipment failures; and improving This paper details the data that can be retrieved from maintenance effectiveness by working on equipment based modern digital protective relays only and how these data on condition instead of on a time basis [1].” can be used to develop an equipment maintenance program that saves time and money. The targeted Operation and maintenance teams can retrieve and audience for this paper is electrical power engineers, analyze a significant amount of information to enhance power system engineers, control engineers, automation system efficiency, including circuit breaker coil monitoring engineers, electrical maintenance engineers, and electrical and contact wear data, motor starting statistics, and power utility owners. transformer through-fault current monitoring. Documenting Keywords—Digital protective relay monitoring the appropriate information in work instructions can features–Automatic retrieval of operating data stored in increase the life cycle of the electrical equipment and digital protective relays–Electrical equipment decrease workload by accurately scheduling a maintenance maintenance enhancements. program for the equipment when really needed. This has the benefit of focusing maintenance teams’ efforts and time I. INTRODUCTION on tasks that provide the highest return [1]. Today, protective relays can be used for several Protective relays provide detailed information about applications outside of their original functions to protect operating characteristics, the status of vital equipment, electrical networks. Control and automation are now and maintenance indicators. Through organizing the combined in most protective relays, and the relays can monitoring features of protective relays (along with their provide data from substations, analyze events, and even data logs) and establishing communications channels prevent failures in electrical devices. between operation and maintenance systems, little or Because protective relays protect electrical systems even no-cost information can be easily retrieved from the against all types of electrical faults, a very detailed and relays to help operators and maintenance engineers well-defined interface usually exists between the relays evaluate the efficiency of electrical equipment and the and the protected equipment so that the relays perform maintenance program needs. Accordingly, these their functions accurately based on the statuses of power operators and engineers can make an informed decision system equipment. This equipment includes but is not and schedule maintenance whenever it is required. * Schweitzer Engineering Laboratories, Inc., 2350 NE Hopkins Court, Pullman, WA 99163 USA • [email protected] TABLE I PERIODIC MAINTENANCE SCHEDULE FOR POWER TRANSFORMER Periodic Inspection Schedule No. Items to Be Inspected Every Every Every Every Every Month 3 Months 6 Months Year 5 Years 1 Ambient, oil, and winding temperature X 2 Ventilation for indoor transformer X 3 Bushing X 4 Relay alarms X 5 Oil leakage X 6 Earth resistance check X 7 Oil filtration X 8 Overall inspection X This paper details the information that can be providing a maintenance program exactly when it is extracted from digital relays and how the information needed (i.e., when the equipment is likely to fail but can be used to create a robust maintenance program. before it actually fails). Hence, it maintains the highest reliability of the equipment and eliminates unplanned II. MAINTENANCE DEFINITIONS system shutdown, ensuring the maintenance program is There are many definitions used to specify the efficient without commitments with a fixed time frame. meaning of maintenance and its types, models, and C. Corrective Maintenance procedures. Put simply, maintenance can be defined as Corrective maintenance is the worst type because it the required process need executed within a specific includes tasks targeted to correct equipment failures time frame to ensure efficiency and high performance that require sudden and unplanned interruption of over the life cycle of equipment. Several actions can be service to consumers. taken based on that process, such as repairing or replacing defective or unhealthy components or IV. MAINTENANCE PROGRAM devices, to guarantee overall system efficiency. It is always best to switch from unnecessary periodic III. MAINTENANCE TYPES maintenance to preventive maintenance because it rapidly reduces the outage of live circuits. In addition, In electrical power systems, maintenance is essential maintenance is performed only when it is needed, to ensure the healthy operation of all equipment in the saving time and money. network—from generation plants to the transmission Without a proper maintenance schedule that aligns network, substations, and distribution network—so with manufacturer recommendations for each piece of power reaches consumers safely, continuously, and equipment, electrical equipment can misoperate or fail efficiently. to perform their main function, which will result in Several types of maintenance have been defined, and performing corrective maintenance. This is the least these types are differentiated by the time of execution, desirable maintenance because it takes the system out of periods, process, action required, and action taken per service suddenly and without warning, and it is very the tasks that they include. costly to return it back to service within a short period A. Periodic Maintenance of time. Power system operators try to avoid this type of Periodic maintenance is the basic maintenance of maintenance at all costs. equipment performed by equipment users. It is also There are many reasons that power system operators defined as time-based maintenance. should invest in maintenance programs, including the It includes a series of basic tasks (e.g., data following: collection, cleaning, visual inspection, and so on). An • Reduce corrective maintenance example of this model of maintenance is shown in • Reduce overtime wasted with low productivity Table I. • Improve customer service • Migrate from scheduled maintenance to B. Preventive Maintenance preventive maintenance Preventive maintenance is the best type because it guarantees the high performance of equipment by Having an efficient maintenance program requires More details on the types of protective relays and accurate monitoring of all power system equipment to their functions can found in [2]. determine whether or not equipment needs Today, a protective relay combines multiple maintenance. Today, digital protective relays can easily functions. It has a processor that can be used to perform provide this accurate information through their built-in several processes at the same time, and it communicates monitoring features. with local and remote devices installed over the power network. However, it is most often used to protect a V. POWER SYSTEM STRUCTURE specific and unique application in the power system. Power system networks consist of various types of equipment with different levels of power and functions. They contain generation, transmission, and distribution devices, as shown in Fig. 1. Fig. 3. Protection System Structure Generators, transmission feeders, transformers, bus bars, capacitors, reactors, and motors require standalone relays with multiple protection functions to protect against any faults that may affect their performance. Fig. 1. Power System Diagram Because a protective relay already interfaces with A digital relay, a type of intelligent electronic device the protected equipment, it can also be readily used to (IED), is a computer-based system with software-based monitor the health of the equipment it protects. protection algorithms that detect electrical faults. It is a Protective relays store this information in nonvolatile smart device that receives inputs, such as analog values memory in various report formats, which can be (current, voltage, resistance, and so on) or digital values retrieved at any time to monitor the protected device. (e.g., binary digits) and compares them to set threshold Reference [3] provides further details on the highly values. It then provides outputs (virtual or physical) reliable and trustworthy information provided by digital
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