Michal Wydra

Secure and Time-Aware Communication of Wireless Sensors Monitoring Overhead Transmission Lines

Existing transmission power grids suffer from high maintenance costs and scalability issues along with a lack of effective and secure system monitoring. To address these problems, we propose to use Wireless Sensor Networks (WSNs)as a technology to achieve energy efficient, reliable, and low-cost remote monitoring of transmission grids. With WSNs, smart grid enables both utilities and customers to monitor, predict and manage energy usage effectively and react to possible power grid disturbances in a timely manner. However, the increased application of WSNs also introduces new security challenges, especially related to privacy, connectivity, and security management, repeatedly causing unpredicted expenditures. Monitoring the status of the power system, a large amount of sensors generates massive amount of sensitive data. In order to build an effective Wireless Sensor Networks (WSNs) for a smart grid, we focus on designing a methodology of efficient and secure delivery of the data measured on transmission lines. We perform a set of simulations, in which we examine different routing algorithms, security mechanisms and WSN deployments in order to select the parameters that will not affect the delivery time but fulfill their role and ensure security at the same time. Furthermore, we analyze the optimal placement of direct wireless links, aiming at minimizing time delays, balancing network performance and decreasing deployment costs.

Optimal Control of Wind Power Generation

Power system control is a complex task, which is strongly related to the number and kind of generating units as well as to the applied technologies, such as conventional coal-fired power plants or wind and photovoltaic farms. Fast development of wind generation that is considered as unstable generation sets new strong requirements concerning remote control and data hubs cooperating with SCADA systems. Considering specific nature of the wind power generation, the authors analyze the problem of optimal control for wind power generation in farms located over a selected remotecontrolled part of the System Operator grid under advantageous wind conditions. This article presents an original stepwise method for tracing power flows that makes possible to eliminate current (power) overloading of power grid branches. Its core idea is to consider the discussed problem as an optimization task.

Overhead Transmission Line Sag Estimation Using a Simple Optomechanical System with Chirped Fiber Bragg Gratings. Part 1: Preliminary Measurements

A method of measuring the power line wire sag using optical sensors that are insensitive to high electromagnetic fields was proposed. The advantage of this technique is that it is a non-invasive measurement of power line wire elongation using a unique optomechanical system. The proposed method replaces the sag of the power line wire with an extension of the control sample and then an expansion of the attached chirped fiber Bragg grating. This paper presents the results of the first measurements made on real aluminum-conducting steel-reinforced wire, frequently used for power line construction. It has been shown that the proper selection of the CFBG (chirped fiber Bragg grating) transducer and the appropriate choice of optical parameters of such a sensor will allow for high sensitivity of the line wire elongation and sag while reducing the sensitivity to the temperature. It has been shown that with a simple optomechanical system, a non-invasive measurement of the power line wire sag that is insensitive to temperature changes and the influence of high electromagnetic fields can be achieved.

Optimal voltage control in distribution networks with dispersed generation

The article presents a new method for voltage control in medium voltage distribution networks with dispersed generation. A linear mathematical model of a distribution network has been proposed. The model makes possible to optimally select feeding voltage of a medium-voltage network as well as reactive power in dispersed power sources according to the actual load and active power generation.

Power system state estimation using wire temperature measurements for model accuracy enhancement

Power system state estimation is a process of real-time online modeling of an electric power system. The estimation is performed with the application of a static model of the system and actual measurements of electrical quantities that are encumbered with error. Usually, a model of the estimated system is also encumbered with uncertainty, especially power line resistances that depend on the temperature of conductors. Presently, a considerable development of technologies for dynamic power line rating can be observed. Typically, devices for dynamic line rating are installed directly on the conductors and measure basic electric parameters such as current and voltage as well as non-electric ones as surface temperature of conductors, their expansion, stress or the conductor sag angle relative to the plumb line. The objective of this article is to present a method for power system state estimation that uses temperature measurements of overhead line conductors as supplementary measurements that enhance quality of the model and thereby the estimation accuracy. Power system state estimation is presented together with a method for using temperature measurements of power line conductors for updating the static power system model in the state estimation process. Results obtained with the application of that method have been analyzed based on the estimation calculations performed for an example system with and without taking into account the conductor temperature measurements. The final part of the article includes conclusions and suggestions for the further research work.