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The delayed operation of distance relays zone-2 element for the faults at the end of the line is excessive. It reduces the fault clearing speed and therefore, is one of the main factors that can endanger power system stability. This paper proposes an impedance-based scheme for discrimination between the last 20% of the line length faults and the adjacent line faults, which are covered by the relay zone-2. The suggested non-pilot scheme uses a modified fault location formula for the accelerated zone-2 operation of distance relays. The negative- and zero-sequence components of local signals are utilized to calculate the accurate fault location after the remote circuit breaker (CB) operation. The proposed algorithm is independent of fault resistance, power flow direction, pre-fault condition, and it can clearly distinguish internal faults from the adjacent line faults. Simulation results show that the proposed method can identify the remote CB operation and thus can accelerate the tripping of zone-2 within a very short time for different fault locations, fault types, fault resistances, and load angles. Also, accurate fault location has been achieved under all simulation conditions. [ABSTRACT FROM AUTHOR]

The fault resistance and infeeded currents from tapped transmission lines are the two main challenges to establish correct fault location estimation in multi-terminal transmission lines. Also, fault location estimation in double-circuit lines is more complicated than single-circuit lines due to the effect of mutual coupling and inter-circuit faults. This paper proposes a negative-sequence network-based method to estimate the fault location of double-circuit multi-terminal transmission lines. In the presented method, signals are measured in the relay location and then, communication links are not required as it uses only one end measurements. Also, in conventional distance relays, six elements are needed to calculate the fault location in all types of faults. Furthermore, in this method, by using only one element for each transmission line, accurate fault location can be estimated. Also, high fault resistance, mutual coupling, and infeeded currents from tapped transmission lines do not have impact on the performance of the presented scheme. To investigate the effects of the line shunt capacitances on the proposed method, a PI model of the transmission lines is used in all the investigations. Simulation results carried out using MATLAB software indicate that the proposed scheme is able to produce excellent performance for the fault location estimation. [ABSTRACT FROM AUTHOR]

• Proposal has distance protection scheme for the lines connected to the PV plants. • The proposed scheme is independent of PV plant parameters and fault resistance. • In this method the exact fault location is also calculated. The output power of the inverter-interfaced photovoltaic (PV) plant has the continuous variations due to the properties of PV modules and environmental conditions. These variations fundamentally affect the performance of the conventional distance protection during nonmetallic faults. This paper proposes a positive sequence network-based distance protection scheme for the transmission lines connected to the PV plants. Different from the adaptive mho and quadrilateral characteristics, the proposed scheme is independent of PV plant parameters and fault resistance. In this method, the Thevenin equivalent parameters of the grid seen from the PV plant are calculated. Thevenin equivalent parameters are calculated using prefault current and voltage data at the local terminal, without additional costs related to the requirements of the communication channel. The obtained parameters are used in the fault resistance compensation. Furthermore, by eliminating the fault resistance effect on the relay impedance, the exact fault location is also calculated. Since the fault line impedance formula is derived only from the positive sequence network, the proposed method is applicable to different grid codes. The efficiency of the proposed scheme is evaluated on the Western System Coordinating Council (WSCC) 9-bus and IEEE 30-bus test systems. The obtained simulation results verify the validity of the proposed scheme under various fault and PV plant conditions. [ABSTRACT FROM AUTHOR]

• The proposed non-pilot scheme is based on the accurate fault location estimation. • This method can be applied to both single- and three-pole CB operation modes. • The proposed method is independent of the line impedance variations and remote source impedances. In multi-zone distance relays, zone-2 has an intentional time delay which is considered for the coordination among the other distance relays. This delay is unnecessary for faults that occur at the end of the protected line and causes the fault to be cleared after hundreds of milliseconds. On the other hand, high-speed fault clearance is an important issue of ensuring the stability of the power system. To address the above problem, an auxiliary fault location (AFL) element based on the proper Kirchhoff voltage law (KVL) loop in the negative- and zero-sequence circuits are designed for distance relays. The input signals to the AFL are the measured signals by local distance relay. The proposed AFL can reduce the zone-2 intentional time delay from 18-28 cycles to 3 cycles. In addition to this, AFL can improve limitations associated with similar methods such as the dependence of these methods to the fault resistance, remote source impedances, and line parameters variation. The AFL can accurately calculate the fault location, before issuing a trip command. Furthermore, to increase the accuracy, the shunt capacitances of the line are compensated by the algorithm. Numerous PSCAD simulation studies verify the effectiveness and applicability of the proposed scheme. [ABSTRACT FROM AUTHOR]

• A pilot scheme to enhance the fault location for TCSC compensated line is proposed. • In this method only the current data at remote-end should be sent to the local-end. • The proposed algorithm is independent of fault resistance, and TCSC parameters. This paper introduces a communication-aided scheme to enhance the fault detection, and fault location calculation for a thyristor-controlled series capacitor (TCSC) compensated transmission lines. In the proposed method only the current data at the remote-end should be synchronously sent to the local-end. Since the remote-end voltage data do not use in local-end, compared with the conventional pilot impedance-based protection schemes, the proposed method significantly reduces the requirement of data transmission bandwidth. The proposed algorithm is independent of fault resistance, power flow direction, and pre-fault condition. In the proposed method the TCSC parameters are not utilized in the derived fault location formula and as a result, the performance of the proposed method is not impacted due to variations in TCSC parameters. Several major factors are taken to investigate the accuracy of the proposed method, including measurement errors and power swing conditions. The simulation results prove the high accuracy and acceleration of the proposed scheme during all fault cases. [ABSTRACT FROM AUTHOR]

• This method is only based on the current data in relay location. • The proposed method is completely analytical. • A negative-sequence based approach used to fault location estimation. This paper introduces an accurate fault location algorithm for double-circuit transmission lines compensated by Static Var Compensator (SVC). The proposed algorithm is based on the negative-sequence circuit of the transmission system and it depends only on the current data available from one end of the line. Since only magnitudes of current signals are required, there is no need for data synchronization. The proposed technique uses the COMTRADE fault files available from digital distance relays and it can effectively locate the all types of unbalanced faults, regardless the high fault resistance, effect of mutual coupling and SVC current injection information. As one formula can be used for all types of fault, classification of fault types and phase selection are not required. The shunt capacitances of the line are considered by utilizing the distributed parameters model of the transmission lines. The proposed algorithm is rigorously investigated for various fault scenarios in SVC compensated transmission system. The simulation cases in the MATLAB environment verifies that the proposed scheme has excellent performance. Test results are compared with a conventional fault location technique to illustrate the accuracy of the proposed algorithm. [ABSTRACT FROM AUTHOR]

• A non-pilot method based on the KVL loop in the negative-sequence circuit is proposed. • The input signals to the method are the measured voltage and current signals by local distance relay. • The proposed method is independent of fault resistance, power flow direction, and SC parameters. Obtaining the accurate fault location in the series compensated double-circuit transmission lines (SCDCTL) is a challenge due to the presence of series compensator, fault resistance, and mutual the coupling between parallel lines. Although by using the pilot fault location methods, the effect of all the aforementioned factors can be eliminated and the location of the fault can be calculated. However, the number of communication channels available for pilot schemes is limited. In addition, the reliability of the communication links for long transmission lines may be particularly reduced. On the other hand, most of the non-pilot methods need to calculate the series compensator data and the accuracy of the fault location in them depends on the accuracy of the series compensator parameters. To improve the limitation of conventional impedance-based methods, this paper presents a non-pilot accurate fault location element (FLE) for conventional distance relays in SCDCTL. The main concept of the proposed method is considering the proper Kirchhoff voltage law (KVL) loop in the negative-sequence circuit of SCDCTL. Consideration of the shunt capacitances of lines ensures accuracy of the achieved fault location formula. It is shown that the designed FLE can improve limitations associated with similar methods such as the dependence of these methods to the fault resistance, mutual coupling between the parallel lines, and the series compensator (SC) parameters. To investigate the performance of the proposed FLE, several factors are considered in the simulation analysis including different fault resistances, fault locations, and fault types. Besides, the influence of current transformer (CT) saturation, measurement errors, external faults, bypassing of the Metal Oxide Varistor (MOV), and effect of noise on the proposed scheme is studied. Evaluation study using PSCAD verify the effectiveness and applicability of the proposed scheme. [ABSTRACT FROM AUTHOR]