## 1 Introduction
### Research Contribution and Novelty  
The task at hand includes evaluating novel aspects. Based on the writers' current understanding, there is currently no previous research in the published literature that presents a PRISMA systematic review of Internet of Things-based transformer condition monitoring, solely concentrating on the interfacing of multiple sensors to form a community of sensors to ensure effective transformer condition monitoring in a real, practical environment setting. This study follows a PRISMA 2020 checklist to present a complete examination ofan IoT-based transformer condition monitoring system. This study further presents the most preferred transformer types, investigated aspects, IoT clouds, microcontrollers, and IoT implementation challenges such as standardization, data security, and the computing power of IoT cloud services and microcontrollers. With regard to the rapidly developing field of Internet of Things technology for electrical transformer condition monitoring, this SLR significantly advances the field. It serves as a thorough and perceptive examination of the most recent advancements and patterns in this developing field. This SLR carefully examines the field of research, including important details about the main goals of the study, the publications that are most recommended, the study's place of origin, and the types of transformers that are being examined. It also revealed microcontrollers, communication channels, software for programming the microcontrollers, tools, and IoT cloud platforms that researchers chose, providing insight into their preferences. Notably, this SLR explores the type of transformers being investigated and the investigated aspects. Power and distribution transformers are highlighted, and the types of transformers that have been the subject of research are categorized and discussed. This SLR also provides a temporal perspective, illuminating the dynamic progress of this field's study. It points out typical problems and restrictions with the use of the Internet of Things and highlights new developments and prospects that could influence the direction of transformer monitoring with the IoT in the future. This SLR essentially acts as a lighthouse, shedding light on the present situation and future direction of a revolutionary technology that is poised to completely alter the field of electrical transformer condition monitoring. This literature review is important because it demonstrates the potential to change how the power systems industry approaches transformer condition monitoring and maintenance through the implementation of IoT monitoring systems. This literature review provides a workable substitute for more conventional, costly techniques by reviewing an affordable IoT-based transformer condition monitoring system. A wider range of power utilities, even those in resource-constrained regions, can now access advanced monitoring technology thanks to the use of inexpensive components like Arduino boards, Raspberry Pi, ESP32, ESP8266, etc. The early identification of any faults is made possible by real-time monitoring of critical transformer parameters like voltage, current, temperature, and oil level. This prolongs the life of transformers and makes timely maintenance possible, thereby averting catastrophic failures. Moreover, IoT integration makes it easier to gather data continuously and remotely monitor systems, which eliminates the need for manual inspections and on-site visits. This increases operational efficiency, saves a significant amount of money, and optimizes resource allocation for power utilities. The suggested system's modular architecture guarantees its scalability and adaptability to different kinds of transformers and power systems, making it simple to expand and customize in accordance with operational and monitoring requirements. Furthermore, this study offers a useful illustration of the Internet of Things use in power systems, making it an important teaching resource for scholars and students.