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Dissolved Gas Analysis (DGA) is one of the most common techniques to detect the incipient faults in the oil-filled power transformers. In this paper, a new approach of DGA technique is proposed to overcome the conflict that takes place in the traditional interpretation techniques for transformer fault diagnosis. The new approach is based on the analysis of 386 dissolved gas samples data set that collected from the Egyptian electric utility chemical laboratory as well as from credited literatures. These data sets are used to build the technique model and also as a tested data set to get the technique’s accuracy. The new approach DGA diagnoses the transformer fault types based on the gas concentration percentage limit of the sum of main five gases (Hydrogen (H 2 ), Methane (CH 4 ), Ethan (C 2 H 6 ), Ethylene (C 2 H 4 ), and Acetylene (C 2 H 2 )) and some suggested gases ratios depending on the sample data set analysis. The validation of the proposed approach of DGA technique is satisfied by comparing its results with the results of the IEC Standard Code, Duval triangle and Rogers methods for the collected data set. The results refer to the ability and reliability of the new approach in transformer faults diagnostic. [ABSTRACT FROM AUTHOR]

• A generalized algorithm to estimate the voltage drop across the TCSC is proposed. • The distance relay terminal voltage is compensated by the estimated TCSC voltage. • This algorithm is effective for TCSC capacitive or inductive modes. • The conduction angle of the TCR is estimated for the different synchronization modes. • The proposed adaptive distance relay is tested under different stress conditions. The variable performance of the thyristor-controlled series compensator (TCSC) system represents a vital challenge for conventional distance relays. Most existing algorithms are based on the measured data at two ends of the TCSC-compensated lines. However, some of single-end algorithms need to modify the distance relay for the series capacitor (SC) only. This paper introduces a generalized algorithm to estimate the voltage drop across the TCSC. The distance relay uses the estimated TCSC voltage drop for terminal voltage compensation. The second objective of the proposed algorithm is to estimate the conduction angle of the thyristor-controlled reactor (TCR) branch under different modes of operation. This algorithm is effective for different TCSC modes such as the capacitive or the inductive modes, in addition to the method of firing angle of synchronization current or voltage synchronization modes. The main benefit of the proposed algorithm is presenting a parameter-less distance scheme for TCSC-compensated transmission line. A 400-kV overhead transmission line test system is simulated in MATLAB/SIMULINK package® and the numerical modeling is implemented in the MATLAB® script in order to evaluate the proposed algorithm effectiveness. The proposed technique is tested under several stress conditions that may face the conventional distance relay. The results illustrate the effective performance of the proposed algorithm. [ABSTRACT FROM AUTHOR]

• A new technique is proposed to detect and classify the PV system fault states. • The technique based on mapping the rate of changes of voltage and current. • The design of the PV system is implemented by installing one diode in every string. • The proposed technique is verified by modelling and experimentally. • This technique is sensitive to internal and stable for external PV array faults. This paper proposes a new simple technique to detect and discriminate the abnormal states of the grid-connected photovoltaic (PV) solar system based on the rate of change of voltage and current trajectory. The design of the PV system is developed by implementation of only one diode in every PV string. The diode prevents the reverse direction of the fault current in case of faulty strings. On the other hand, the installation of a diode reduces the ability of faults detection and diagnosis depending on currents in each string. The proposed technique depends on the rate of change of voltages and current trajectory during the fault transient period. The proposed algorithm can detect various fault cases such as cell-to-cell and string to string faults in addition to partial and full shadow faults. Also, the algorithm differentiates between high and low fault cases for each fault types. Moreover, the proposed technique is characterized by high sensitivity for internal abnormal states within certain array with high security level for the external abnormal conditions and normal load changing. The proposed technique is applied for a four-array PV system, which has a power rating of 400 kW connected to an AC grid. The simulation results and validation of the proposed technique are implemented by MATLAB/Simulink toolbox. The proposed technique is experimentally applied for a small PV system of a rating of 1.25 kW to prove its validity. [ABSTRACT FROM AUTHOR]