Faults in the power system need appropriate maintenance actions at the fault point to fix the problem immediately. A high percentage of the short circuit faults in power systems occur on the transmission system where the lines pass through different harsh climates and experience outdoor environmental conditions. The repairing procedure of the faulty line requires determining the accurate fault location. Fast and accurate fault location of transmission networks play an important role in modern power systems to improve the system reliability and stability. A fault locator is an apparatus that determines the location of the fault in the transmission system by acquiring the proper measured quantities, i.e. the voltages and currents at the lines terminals. As such, the utilities can repair and fix the problem rapidly after determining the location of the fault using the analytical and numerical methods provided in fault locators. This research explores various fault location techniques of transmission networks in detail as a vital requirement for operating the modern power system more secure and reliable. In this survey, different new methods of fault location such as i) distance relay algorithm, ii) traveling wave, iii) artificial intelligence, iv) wide-area, v) time reversal theory, vi) differential equations, and vii) impedance calculation methods are reviewed and investigated to illustrate their pros and cons inaccurate fault location for complex modern power networks. In addition, these methods are assessed to compare their requirements, abilities and shortcomings. Moreover, using the provided extensive analysis in the paper, and based on the useful experiences of the authors, some beneficial topics and suggestions are proposed for future works and improved algorithms in the field of fault location.

Different issues will be raised and highlighted by emerging distributed generations (DGs) into modern power systems in which the islanding detection is the most important. In the islanding situation, a part of the system which consists of at least one DG, passive grid, and local load, becomes fully separated from the main grid. Several detection methods of islanding have been proposed in recent researches based on measured electrical parameters of the system. However, islanding detection based on local measurements suffers from the non-detection zone (NDZ) and undesirable detection during grid-connected events. This paper proposes a passive islanding detection algorithm for all types of DGs by appropriate combining the measured frequency, voltage, current, and phase angle and their rate of changes at the point of common coupling (PCC). The proposed algorithm detects the islanding situation, even with the exact zero power mismatches. Proposed algorithm discriminates between the islanding situation and non-islanding disturbances, such as short circuit faults, capacitor faults, and load switching in a proper time and without mal-operation. In addition, the performance of the proposed algorithm has been evaluated under different scenarios by performing the algorithm on the IEEE 13-bus distribution system.

Penetration of DC networks is rapidly increasing in modern power systems. As transient behavior of DC grids is different from that of AC ones, AC grid protection schemes might not be applicable to protect DC networks. Exact fault location is vital for protection of DC networks to reduce repair cost and achieve fast power recovery. This paper proposes a novel topology independent multi-terminal DC scheme to identify fault section and location for DC transmission systems. Voltage and current signals measured at the terminals are analyzed by the least squares error (LSE) algorithm. Then, the proposed scheme uses low frequency components of the signals to locate DC faults offline. Unlike some other methods, it does not require sophisticated sensors and hardware to capture very high frequency content of the signals. Hence, the proposed scheme can be implemented in practice without additional measuring infrastructure. The performance of the proposed scheme is evaluated under various fault conditions for different topologies of DC networks in both overhead lines and cables. Numerous simulations carried out demonstrate that the proposed scheme is quite accurate and provides excellent performance under different fault resistances, sections, and locations.

Penetration of renewable energy sources (RESs) in power systems is increased considerably and fault location algorithms face considerable problems with the presence of RESs. Also, the third terminal of three-terminal lines is expanded as a cost-effective solution to energize the remote areas of medium voltage (MV) systems, while its data may not be measured and easily available. In addition, in cases where this data is obtainable, due to the excessive harmonics of the inverter-based resources (IBRs) in that terminal, the measured data includes high error. Therefore, providing a method for fault location in three-terminal lines in the presence of RESs is challenging. This paper proposes an accurate method to identify the fault location on these lines incorporating RESs without requiring the third terminal data. Due to current transformers saturation and transient response of capacitive voltage transformers, the fault location based on the faulted phase data contains significant errors. The proposed method combines both the faulty and healthy phases data to improve the accuracy of fault location. Its performance is evaluated on a MV system for different scenarios including various fault resistances, locations and types, and third terminal integration of RESs. The obtained results confirm superiority of the proposed method.

Smart grid enables integration of distributed generations (DGs) to contribute to support the network. In the islanding condition, a section of the system and at least one DG become separated from the main grid and can continue to operate autonomously. This paper proposes a passive islanding detection algorithm using just the DG power factor angle to extract an indicator for islanding detection with a negligible non-detection zone (NDZ). The proposed algorithm guarantees reliable detection of islanding condition even where the system is composed of multiple DGs including different types. In this paper, islanding and non-islanding events are discriminated using the proposed algorithm even in a nested microgrid which is operated autonomously. Moreover, the proposed algorithm provides secure detection in the noisy condition. Also, the proposed algorithm allows reaching the frequency and voltage ride-through requirements quickly by correctly discriminating grid-connected disturbances from islanding condition. The performance of the proposed algorithm is validated by performing extensive simulations and scenarios in different test systems. The results of the IEEE 34 bus test system have been presented in this paper.

Advances in renewable energy recourses technologies have paved the way for increased utilization of DC grids in modern power systems. In particular, high voltage DC (HVDC) transmission cables are used to harvest offshore energy. Since failure diagnosis and repair of the buried offshore cables under the sea bed involve quite laborious tasks, accurate fault location is of vital importance. This paper proposes a novel fault location method based on the synchronized measurement of conductors and sheaths currents in each terminal without requiring the voltage signal. Unlike the traveling-wave-based methods, the proposed method is developed for multi-terminal HVDC systems without requiring any high precision measurement infrastructure. The proposed method can be implemented for different system topologies as well as fault resistance and fault distance. The fault location method can provide accurate results even if 10ms time window samples are imported into the proposed algorithm. In addition, accuracy of the fault location using the proposed method is not affected significantly by noisy condition. Different test systems have been simulated to evaluate performance of the proposed method in various scenarios. Obtained results confirm that the proposed practical method can provide the accurate fault location for all different scenarios and conditions.