Ibrahim Faiek Abdulhadi

P and M Class Phasor Measurement Unit Algorithms Using Adaptive Cascaded Filters

The new standard C37.118.1 lays down strict performance limits for phasor measurement units (PMUs) under steady-state and dynamic conditions. Reference algorithms are also presented for the performance (P) and measurement (M) class PMUs. In this paper, the performance of these algorithms is analyzed during some key signal scenarios, particularly those of offnominal frequency, frequency ramps, and harmonic contamination. While it is found that total vector error (TVE) accuracy is relatively easy to achieve, the reference algorithm is not able to achieve a useful rate of change of frequency (ROCOF) accuracy. Instead, this paper presents alternative algorithms for P and M class PMUs, which use adaptive filtering techniques in real time up to 10-kHz sample rates, allowing consistent accuracy to be maintained across a ±33% frequency range. ROCOF errors can be reduced by factors of > 40 for P class and > 100 for M class devices.

Adaptive protection architecture for the smart grid

Unique and varied power system conditions are already being experienced as a result of the deployment of novel control strategies and new generation and distribution related technologies driven by the smart grid. A particular challenge is related to ensuring the correct and reliable operation of protection schemes. Implementing smarter protection in the form of adaptive setting selection is one way of tackling some of the protection performance issues. However, introducing such new approaches especially to safety critical systems such as protection carries an element of risk. Furthermore, integrating new secondary systems into the substation is a complex and costly procedure. To this end, this paper proposes an adaptive protection architecture that facilitates the integration of such schemes into modern digital substations which are a staple of smart grids. Functional features of the architecture also offer powerful means of de-risking schemes and flexible implementation through self-contained modules that are suitable for reuse. An example adaptive distance protection scheme is presented and tested to demonstrate how the architecture can be implemented and to highlight the architectures novel features.

FlexNet wide area monitoring system

This paper presents the results of collaborative research from the SUPERGEN FlexNet Consortium into Wide Area Monitoring, Protection and Control (WAMPAC). The focus of the research addresses the design and development of an optimal WAMPAC architecture, communication infrastructure and real-time WAMPAC applications which will play an important role in future GB power network operation and understanding. The article concludes with an assessment of inter-area oscillations based on data records captured by the wide area monitoring system (WAMS) established as part of the FlexNet project.

Switching Markov Gaussian Models for Dynamic Power System Inertia Estimation

Future power systems could benefit considerably from having a continuous real-time estimate of system inertia. If realized, this could provide reference inputs to proactive control and protection systems which could enhance not only system stability but also operational economics through, for example, more informed ancillary reserve planning using knowledge of prevailing system conditions and stability margins. Performing these predictions in real time is a significant challenge owing to the complex stochastic and temporal relationships between available measurements. This paper proposes a statistical model capable of estimating system inertia in real time through observed steady-state and relatively small frequency variations; it is trained to learn the features that inter-relate steady-state averaged frequency variations and system inertia, using historical system data demonstrated over two consecutive years. The proposed algorithm is formulated as a Gaussian Mixture Model with temporal dependence encoded as Markov chains. Applied to the U.K. power system, it produces an optimized mean squared error within 0.1 s2 for 95% of the daily estimation if being calibrated on a half-hourly basis and maintains robustness through measurement interruptions of up to a period of two hours.

Defining the role of wide area adaptive protection in future networks

Recent increases in generation diversity, use of renewable energy resources and HVDC, as well as the increasing electricity demand may act to push power systems closer to their operating limits, not to mention the increasing likelihood of hidden failures or severe contingencies. It has never been easy for conventional protection with fixed relay settings to deal with such complicated scenarios. That, inevitably, led to some protection performance issues, including sensitivity and coordination issues. Accordingly, to maintain a reliable and robust power system, a protection system which is potentially immune to changes and aforementioned challenges plays an important role in future networks. Adaptive protection, capable of real-time signal processing and timely adjustment of relay settings for the prevailing system conditions, is seen as a potential approach to cope with these system issues. This paper will define wide area adaptive protection (WAAP) and discuss why and how adaptive protection can be best utilized to improve protection performance, particularly during system-level disturbances. The potential challenges and drawbacks of WAAP are also analysed.

A dynamic modelling environment for the evaluation of wide area protection systems

This paper introduces the concept of dynamic modelling for wide area and adaptive power system protection. Although not limited to these types of protection schemes, these were chosen due to their potential role in solving a multitude of protection challenges facing future power systems. The dynamic modelling will be implemented using a bespoke simulation environment. This tool allows for a fully integrated testing methodology which enables the validation of protection solutions prior to their operational deployment. Furthermore the paper suggests a distributed protection architecture, which when applied to existing and future protection schemes, has the potential to enhance their functionality and avoid mal-operation given that safety and reliability of power systems are paramount. This architecture also provides a means to better understand the underlying dynamics of the aforementioned protection schemes and will be rigorously validated using the modelling environment.

A Model-Based Hybrid Approach for Circuit Breaker Prognostics Encompassing Dynamic Reliability and Uncertainty

Prognostics predictions estimate the remaining useful life (RUL) of assets. This information enables the implementation of condition-based maintenance strategies by scheduling intervention when failure is imminent. Circuit breakers (CBs) are key assets for the correct operation of the power network, fulfilling both a protection and a network reconfiguration role. Certain breakers will perform switching on a deterministic schedule, while operating stochastically in response to network faults. Both types of operation increase wear on the main contact, with high fault currents leading to more rapid aging. This paper presents a hybrid approach for prognostics of CBs, which integrates deterministic and stochastic operation through piecewise deterministic Markov processes. The main contributions of this paper are: 1) the integration of hybrid prognostics models with dynamic reliability concepts for a more accurate RUL forecasting and 2) the uncertain failure threshold modeling to integrate and propagate uncertain failure evaluation levels in the prognostics estimation process. Results show the effect of dynamic operation conditions on prognostics predictions and confirm the potential for its use within a condition-based maintenance strategy.

Application of a MW-scale motor-generator set to establish power-hardware-in-the-loop capability

This paper presents a Power-Hardware-in-the-Loop (P-HiL) testbed coupled to a MW-scale Motor-Generator (MG) set. The P-HiL configuration interfaces an 11 kV physical distribution network with a transmission network modeled in a Real Time Digital Simulator (RTDS) through the MG set. Uniquely, and in contrast with other P-HiL arrangements, the MG set used is equipped with a proprietary frequency controller with an inherent response that does not provide the desired characteristics to cater for a P-HiL interface. The paper describes a methodology to tackle this problem associated with undesirable response of the MG sets existing controller by introducing additional frequency and phase control loops. Experimental results are presented and show that the P-HiL testbed is capable of maintaining a high level of synchronization during disturbances and allows the power interaction between the model and physical network. The testbed offers a realistic and flexible testing environment for prototype systems connected to distribution networks with a specific focus on testing systems that control demand side resources for frequency response during loss of generation events.

Reachability analysis for the verification of adaptive protection setting selection logic

The testing of adaptive protection schemes is a problem that remains largely unaddressed. These schemes can be characterized by uncertainty in behavior due to the dynamic changes in their configuration to suit prevailing network conditions. This paper proposes a novel approach to formalizing this behavior using hybrid systems modeling. This unlocks the ability to verify the safety performance of the schemes using reachability analysis. In this paper, an adaptive setting selection logic for distance protection is verified for its safety, using reachability analysis, during changes in network conditions.