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The distance relay using the transmission line impedance measurement identifies the type and location of the fault. However, any other factors that cause the failure of the measured impedance, makes the relay detect the fault in incorrect location or do not detect the fault at all. One of these factors is the fault resistance which directly increases the measured impedance by the relay. Another factor that indirectly alters the impedance of the transmission line is static synchronous compensator (STATCOM). When a fault happens, current injection by the STATCOM changes the measured signals by the relay and thus makes the calculated impedance incorrect. In this paper, a method is provided based on the combination of distance and differential protection. Firstly, from the current data of buses, faulted transmission line is detected. Then using the presented algorithm, the fault location is calculated on the transmission line. The basis of the algorithm is on the active power calculation of the buses. Fault resistance is calculated from the active powers and its effect will be deducted from calculated impedance by the algorithm. Furthermore, with choosing data of appropriate bus, STATCOM effect is eliminated, and fault location will be obtained. [ABSTRACT FROM AUTHOR]

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]

Locating a fault in double-circuit transmission lines is a challenging task due to the mutual coupling effects between adjacent circuits of the line. Also, performance of impedance-based fault location schemes for double-circuit lines is adversely affected by fault resistance. Accurate fault location in double-circuit lines can be achieved if fault location schemes utilize reliable communication links. However, the communication links are not available or enabled in all transmission lines. To overcome such difficulty in fault location in double-circuit lines, a new fault location scheme is proposed for double-circuit transmission lines by using voltages and currents data extracted from single-end of the line. Only the negative-sequence current and voltage phasors during the fault are processed for calculating the fault location. The proposed fault location formula is derived by applying the Kirchhoff's voltage law around the parallel circuits and shunt capacitances loops. Obtained formula is applicable for all types of unbalanced faults and accordingly classification of fault types and phase selection are not required. The proposed scheme is immune to the fault resistance and insensitive to mutual coupling effects. Evaluation results verify that the accuracy of the proposed algorithm is very high under various fault resistances, fault locations, and fault types. [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]

• 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 fault resistance and remote source impedances. The accelerated operation of distance relay is an important issue to improve the power system stability. The zone-1 of distance relay usually covers about 80% of the transmission line length with an instantaneous operation, while during resistive faults the coverage of zone-1 may be reduced considerably. Therefore, the conventional distance relay cannot cover the whole line length with fast fault clearance. To address the above problem, a non-pilot protection scheme based on the accurate fault location estimation is proposed. When a fault occurs at the end section of the line, after the fast remote circuit breaker (RCB) operation, the accurate amount of fault current can be obtained. Using this current, the accurate fault location is calculated, and as a result, the accelerated trip can be issued to the local circuit breaker (CB) for the faults occurring at all the total line length including the end section faults. The obtained fault location formula is independent of the fault resistance and remote source impedances and can be applied to both single- and three-pole CB operation modes. The proposed high-speed protection scheme is evaluated in the WSCC 9-bus system. 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]

• An accurate bi-level single-end fault location algorithm is proposed. • The iterative nature of the method leads to its independency of fault resistance. • It converges very quickly and in a few iterations. • It can be applied to both transposed and un-transposed transmission lines. • It is robust to measurement noise and uncertainties in lines parameters. To guarantee continuous and reliable operation of power systems working near their stability margins, it is necessary to clear faults quickly. For this purpose, accurate and fast fault location methods are required. Single-ended phasor based methods are a category of fault location strategies which are favourable due to simplicity of their implementation. However, enhancing the accuracy of these methods is a challenging task due to unavailability of data from the remote end of the line. In this paper, a novel fault location method that requires the measured data of one end of the line is proposed. As a result, this method does not need communication links. The proposed method is bi-level and in its first level, fault characteristics such as current, voltage, and impedance of the fault are calculated for a given fault location obtained from Level-2. Then, based on the calculated fault characteristics, fault location is updated in the second level. The presented fault location method considers magnetic coupling between lines and it is also applicable for both transposed and un-transposed lines. Numerous simulation studies verify the accuracy of the proposed method in presence of uncertainties such as noise, fault impedance and error in input line parameters. Furthermore, although the proposed method is based on a bi-level iterative approach, the presented results confirm that it converges quickly in 2 or 3 iterations. [ABSTRACT FROM AUTHOR]