A power transformer is one of the most critical and expensive assets in electric power systems. Failure of a power transformer would not only result in a downtime to the entire transmission and distribution networks but may also cause personnel and environmental hazards due to oil leak and fire. Hence, to enhance a transformer’s reliability and extend its lifespan, a cost-effective and reliable condition monitoring technique should be adopted from day one of its installation. This will help detect incipient faults, extend a transformer’s operational life, and avoid potential consequences. With the global trend to establish digital substation automation systems, transformer online condition monitoring has been given much attention by utilities and researchers alike. Several online and offline condition monitoring techniques have been recently proposed for oil-immersed power transformers. This paper is aimed at providing a state-of-the-art review for the various condition monitoring technologies used for oil-immersed power transformers. Concept of measurements and analysis of the results along with the future trend of condition monitoring techniques are presented.

Communication protocols play a pivotal role in the substation automation system as they carry critical information related to asset control, automation, protection, and monitoring. Substation legacy protocols run the assets’ bulk data on multiple wires over long distances. These data packets pass through multiple nodes, which makes the identification of the location and type of various malfunctions a challenging and time-consuming task. As downtime of substations is of high importance from a regulatory and compliance point of view, utilities are motivated to revisit the overall scheme and redesign a new system that features flexibility, adaptability, interoperability, and high accuracy. This paper presents a comprehensive review of various legacy protocols and highlights the path forward for a new protocol laid down as per the IEC 61850 standard. The IEC 61850 protocol is expected to be user-friendly, employ fiber optics instead of conventional copper wires, facilitate the application of non-conventional instrument transformers, and connect Ethernet wires to multiple intelligent electronic devices. However, deployment of smart protocols in future substations is not a straightforward process as it requires careful planning, shutdown and foreseeable issues related to interface with proprietary vendor equipment. Along with the technical issues of communication, future smart protocols call for advanced personnel and engineering skills to embrace the new technology.

With the global trend to digitalize substation automation systems, International Electro technical Commission 61850, a communication protocol defined by the International Electrotechnical Commission, has been given much attention to ensure consistent communication and integration of substation high-voltage primary plant assets such as instrument transformers, circuit breakers and power transformers with various intelligent electronic devices into a hierarchical level. Along with this transition, equipment of primary plants in the switchyard, such as non-conventional instrument transformers, and a secondary system including merging units are expected to play critical roles due to their fast-transient response over a wide bandwidth. While a non-conventional instrument transformer has advantages when compared with the conventional one, extensive and detailed performance investigation and feasibility studies are still required for its full implementation at a large scale within utilities, industries, smart grids and digital substations. This paper is taking one step forward with respect to this aim by employing an optimized network engineering tool to evaluate the performance of an Ethernet-based network and to validate the overall process bus design requirement of a high-voltage non-conventional instrument transformer. Furthermore, the impact of communication delay on the substation automation system during peak traffic is investigated through a detailed simulation analysis.

Substation Automation System (SAS) is currently in a matured state of technology that shall facilitate transformational changes from conventional protection scheme. IEC 61850 protocol is considered as the crux of digital SAS due to its multifunction features that include seamless communication, ability to integrate various intelligent electronic devices, potential for improved real-time condition monitoring, reliable protection, and control of critical electrical assets. Because the application of IEC 61850 in SAS is relatively new and has not fully implemented in many substations yet, further feasibility studies using multivendor equipment to assess its performance under different operating conditions is imperative. In this paper, a practical reliable and efficient reverse blocking over current bus bar protection scheme based on IEC 61850 is implemented and tested. Also, a comparison of digital SAS and conventional protection scheme is presented to highlight the superiority of the former one. Experimental results attest the reliability and effectiveness of the proposed digital protection scheme along with the accuracy and security of transmitting data packets using sampled values and generic objective-oriented substation event communication protocols adopted by IEC 61850.

Reliable protection, communication and control are the key features of a digital protection scheme in a utility substation. Microgrid is an alternative solution of installing long Transmission & Distribution lines could be cost prohibitive. There are number of Intelligent Electronic Devices (IEDs) which could find applications in controlling and monitoring of power network in a Microgrid set up and one such device is Phasor Measurement Unit (PMU). It is a microprocessor based intelligent device which gathers high-resolution data, checks the power quality and records disturbances. However, few issues that remains to be addressed such as, interoperability in a multi-vendor equipment and coordination between individual control systems in an integrated scheme. In this paper, an Operational Network Technology (OPNET) software model of a PMU has been designed and tested for its performance in a Microgrid environment based on IEC 61850-90-5 standard.

Communication between intelligent electronic devices (IED's) is an important feature of a utility substation automation system based on IEC 61850. Time critical information related to fault and overcurrent, under frequency messages for substation automation system (SAS) and the use of IED's from multiple vendors, has opened up issues related to a reliable protection system within the high voltage substation. Early detection of the delay in data transmission over a Generic Object Oriented Substation Event (GOOSE) network is an important step towards identification of problems associated with the dynamic protection system. It is observed that non critical messages adds up the queuing time and delays in the delivery of the messages which could be an issue in the reliable operation of a protection system. In this paper an Optimized Network Engineering Tool (OPNET) model is created, tested and analysed for a single and double bus configuration in detail for the delay encountered in data transfer within a typical zone substation. In order to understand the delay in transmission of packets, a 132/22kV zone substation model is analysed and results are discussed based on GOOSE communication in an IEC 61850 environment. Further, the delay in communication is compared and analysed between a single and double bus system of a 132/22kV substation to determine the best alternative technique available from protection point of view in a SAS network.