Power system components usually have standard static ratings that determine the load constraints. Load constraints are designed for extreme conditions and are one of the reasons, why power systems do not use all of their potential transmission capacity. In the 21st century, efficiency and the cost of energy production and distribution have become a very popular topic, because the energy production and its transmission cost has a direct influence on sustainability. Dynamic Rating is a smart grid application, which allows using more of the system capacity by monitoring system conditions. This paper presents a literature review on the topic of Dynamic Rating. We focus on Dynamic Rating of overhead lines. Overhead lines are of great interest for Dynamic Rating applications, because of their high cost and high potential for further improvement. Different tools for analysis of real time data and ways of application of Dynamic Rating to the power system are taken into consideration.

Dynamic Line Rating (DLR) is a technology that allows extending capacity of existing power lines for transportation higher electrical power capacity from production site to the customer. Environmental conditions such as air temperature and wind speed have significant impact on the heat balance of the power line, therefore by monitoring the weather parameters one can dynamically vary the capacity of power line. Brief analysis of the wind speed and direction effects on the cooling of overhead lines and principles of wind power generation provide a background for the analysis of wind power connection to the existing power lines by means of Dynamic Line Rating.

This paper presents the case study of wind farm connection to the existing power line by application of DLR. Statistical weather data and information about system properties give an input parameters for the risk analysis of the dynamic rating application and highlight benefits of using DLR. The results show a potential to expand the transportation capacity of the line by injecting more wind power. Probabilistic analysis of the historical weather data and reliability analysis of the system show that line capacity can be expanded with more wind power without affecting availability of the connection.

An increasing share of renewable energy on the electricity market creates the need for economic and efficient production, operation and integration technologies, associated with the specific behavior of renewable energy sources (RES). Dynamic rating (DR) provides a possibility to apply improvements to the system both during planning and operation stages. The DR benefits are well described in various literature sources. However, DR is often focused on more efficient exploitation of power lines, not power transformers. Power transformers are costly equipment and their efficient usage and planning can have drastic effect on total costs.

Our analysis focuses on the dynamic transformer rating (DTR) for wind energy applications. The main objective is to study reliability effects of DTR from the component perspective. We utilize existing knowledge about transformer heat balance models from IEC and IEEE standards to obtain information on the loss of life (LOL) of the transformer under investigation and propose possible improvements for the system in question. The method can be employed for identifying the appropriate transformer size by taking into account ambient temperature and load variations and then overloading the transformer beyond nameplate ratings. The reliability of the proposed application is ensured by calculating the risk of overloading the transformer for each day of the year. A risk of overloading is quantified as LOL of the transformer. The risk is presented as a function of ambient temperature and duration of an overload. The final step consists of an economic analysis, which demonstrates economic benefits of DTR application.

Dynamic transformer rating (DTR) can be used to load power transformers above nameplate rating, while respecting contingency loading limits and ensuring an acceptable risk level. Purchase of power transformers is a major contributor for high costs of building new substations. Application of DTR allows to postpone the investment in new power transformers in old substations, thus DTR has a potential to become an economically beneficial technology. A quantitative risk and economic evaluation of DTR application is performed for a wind farm connected transformer and thus for a highly variable load scenario. The risks analyzed in this project are increased loss of insulation life and the risk of dielectric failure, based on the Arrhenius-Weibull model. A comparative net present value calculation has been performed to investigate the profitability of replacing a 19.4 MVA transformer with a 16 MVA dynamically rated transformer. The feasibility of DTR application is analyzed and a methodology is developed to support both transformer manufacturer and potential customers, such as distribution system operators, in the decision-making process of purchasing of dynamically rated transformer for wind energy applications.