Power Differential Protection Research Articles

An enhanced sensitive power differential protection for series compensated transmission lines in renewable generation intensive power systems

Series compensation is widely used to improve the electrical characteristics of long transmission lines and increase the power transfer capability. However, the insertion of a series capacitor introduces various phenomena that affect the performance of traditional distance relays. Moreover, the fault characteristics of renewable generation systems coupled with generation outputs that vary with weather patterns produce additional complications to the protection of transmission lines. This paper proposes the application of an enhanced sensitive power differential protection (SPDP) algorithm to the protection of series compensated transmission lines. The algorithm incorporates a criterion that improves the security of the protection by inhibiting the SPDP algorithm from operating for faults external to the protected line. Performance of the enhanced SPDP algorithm has been evaluated on a test system built in Digsilent Powerfactory software. Various in-zone and out-of-zone fault cases were simulated at different compensation levels and fault resistances. The results showed that the enhanced SPDP protection technique can detect in-zone faults along practically the entire transmission line (99.99 %) for compensation levels up to 90 %. The method operated reliably for faults with resistances up to 330 Ω.

Research on CNN-LSTM DC power system fault diagnosis and differential protection strategy based on reinforcement learning

Introduction: With the development of artificial intelligence technology, more and more fields are applying deep learning and reinforcement learning techniques to solve practical problems. In the power system, both the direct current (DC) power system and the power grid substation are important components, and their reliability and stability are crucial for production efficiency and safety. The power grid substation is used to convert power from high-voltage transmission lines to low-voltage transmission lines, or from alternating current to direct current (or vice versa), in order to efficiently transmit and distribute power in the power system. However, diagnosing faults and designing cascaded protection strategies has always been a challenge due to the complexityand uncertainty of the DC power system.Methods: To improve the reliability and stability of the DC power system and power grid substation, this paper aims to develop an intelligent fault diagnosis system and cascaded protection strategy to reduce faults and downtime, lower maintenance costs, and increase production efficiency. We propose a method based on reinforcement learning and a convolutional neural network-long short-term memory (CNN-LSTM) model for fault diagnosis and cascaded protection strategy design in the DC power system. CNN is used to extract features from raw data, while LSTM models time-series data. In addition, we use reinforcement learning to design cascaded protection strategies to protect the power system from the impact of faults.Results: We tested our method using real 220V DC power system data in experiments. The results show that our method can effectively diagnose faults in the DC power system and formulate effective cascaded protection strategies.Discussion: Compared with traditional methods, this intelligent method can diagnose faults faster and more accurately, and formulate better cascaded protection strategies. This method helps reduce maintenance costs, increase production efficiency, and can be applied to other fields.

Power Differential Protection for Transformer Based on Fault Component Network

Current differential protection has been widely used as the primary protection of transformers. However, inrush currents during transformer energization can cause misoperation of the protection when the second harmonic restraint algorithm fails. This paper proposes a power differential protection scheme based on the fault component network (FCN), which is free from inrush detection and computationally cheap. First, the fault component differential power (FCDP), defined as the differential active power of a transformer in the FCN, is analyzed under different conditions. Second, a transformer protection scheme is presented based on the FCDP and the traditional differential power. A removal algorithm of decaying direct current (DDC) offset is developed to accurately estimate the FCDP. The performance of the scheme is tested under various conditions, including internal faults, external faults and transformer energization. The simulations using PSCAD, and Real Time Digital Simulator (RTDS), experiments in the Electrical Power Dynamic Laboratory (EPDL) and real recording data validate that the proposed method can protect the transformer reliably.

Power differential protection for half-wavelength transmission lines—Software in the loop analysis

Half-wavelength transmission line protection is a challenge that hinders the implementation of this technology. However, this line is considered an interesting alternative to transmit bulk power blocks over very long distances and to connect wind and photovoltaic generation to an electrical power system. This study introduces a method to protect a half-wavelength transmission line. The proposed complex plane-based protection algorithm uses a differential complex power in the sequence domain to detect faults along the entire line. The embedded spark-gap mitigation device is properly considered because it is a necessary apparatus to remove severe resonant fault conditions. A time-domain analysis shows that the proposed algorithm achieves robust performance for both internal and external faults.

Performance evaluation of power differential protection applied to half-wavelength transmission lines

The half-wavelength transmission line is considered a feasible alternative to interconnect very distant electrical subsystems, in the range of thousands of kilometers. Despite presenting good economic advantages, this alternative still has some challenges. This kind of line has unique characteristics, which makes it difficult to apply protection methods as practised today. This paper presents an analysis of power differential protection developed for half-wavelength transmission lines. Here, the performance of complex power is analysed. The method uses apparent power in the sequence domain to develop efficient protection. During an external fault, there is a balance between the measured power in both line terminals. However, when an internal fault occurs, this balance is broken. MATLAB simulations show that the method achieved good results, mainly in detecting faults in the central region of the line and external faults. Additionally, the tests considered the spark-gap apparatus to remove severe resonant fault conditions.

Double-K Differential Protection Principle of Regional Power Grid Based on Voltage Vector Compensation

In the regional active distribution network where the Distributed Generation (DG) penetration rate is getting higher and higher. When a high-resistance ground fault occurs in a heavy-load line, the traditional current differential protection has very low sensitivity, the protection may refuse to act. And the power differential protection has the voltage dead zone. In addition, the T-type branch will further reduce the sensitivity of the traditional differential protection. In order to solve the problems, this paper proposes a new principle of double-K differential protection with voltage vector compensation. The principle can flexibly adjust the braking zone range by setting two parameters, and then introduce the voltage vector to compensate the operating point, which effectively improves the protection sensitivity in the case of high-resistance ground fault occurs in a heavy-load line, and there is no voltage dead zone. Simulation shows that the principle can greatly improve the reliability of protection.

SIMULATION OF TRANSFORMER DIFFERENTIAL PROTECTION IN THE MATLAB ENVIRONMENT

Currently, relay protection is based on microprocessor units, which have expanded functionality in comparison with traditional electromechanical means. For the correct operation of these devices, it is necessary to enter the actuation settings, which are calculated manually taking into account the characteristics of a particular power system. Modeling of relay protections in the MatLab environment allows reducing the role of the human factor and minimizing possible errors. (Research purpose) The research purpose is to develop a model of differential relay protection of the transformer in the MatLab Simulink environment. (Materials and methods) The article presents a model of a power system with a power two-winding transformer and differential relay protection with the functions of a current cut-off, differential protection with bias and blocking of the magnetization current surge. (Results and discussion) In the external short-circuit mode, the current protection does not acts, which indicates that the differential protection against external short circuits is detuned. In the short-circuit mode, current cut-off and protection with bias are triggered from the sides of the lower and higher voltages, which also indicates the adequacy of the model. Testing in the magnetization current surge showed that with the 0.15 detuning setpoint recommended by manufacturers of relay protection devices, the protection is blocked for more than 15 seconds, which is unacceptable in practice. The adequate operation of the relay protection is noted at a setpoint of 0.7. The dependence of the harmonic composition of the magnetization current surge on the switching moment on the transformer relative to the transition of the supply voltage through zero was revealed. (Conclusions) The developed model implements the functions of differential protection of the transformer, adequately reproduces all the processes of digital signal processing in microprocessor relay protection units, allows you to check the correctness of functioning in different modes and at different actuation settings.

Transformer power differential protection using real-time HIL test-based implementation of second-order transient-extracting transform

A novel Instantaneous Power-based Differential Protection (IPDP) for transformers is presented in this paper. The instantaneous power, gathering the voltage and current information, discriminates between internal fault and external fault, inrush current, sympathetic inrush current, overexcitation, and ultrasaturation with and without CT (Current Transformer) saturation. The proposed method relies on the waveshape properties of the instantaneous power signal. A high-resolution time–frequency analysis (TFA) technique, namely Second-Order Transient-Extracting transform (STET), is used for the discrimination purpose. Furthermore, the STET technique results are examined in a Hardware-in-the-Loop (HIL) test using Raspberry Pi (R-Pi) to evaluate the real-time speed of the proposed algorithm. This real-time manipulation results in the internal fault and other transient phenomena distinction time to be 14 ms. The proposed method does not require transformer parameters and various operating conditions of the power system and is entirely immune against noise. The usefulness of the proposed method is evaluated through numerous simulations as well as experimental implementation. Two experimental setups are considered for ensuring the practicality of the proposed method. The first one is a laboratory setup for capturing real-world transformer internal fault and inrush current waveforms. The second one includes a relay and CT tester, namely, Vebko Amirkabir AMT105 relay tester and a laboratory CT for determining the CT saturation test.

Novel Differential Protection Approach of UHV AC Transmission Lines Based on Tellegen's Quasi-Power Theorem

When current differential protection is applied to an AC transmission line, synchronous sampling at the two ends is required. The use of GPS synchronization increases the difficulty and cost of project implementation while the use of ‘ping-pong’ synchronization requires that the communication channel has equal transmission and reception delay. To overcome the impact of these issues, power differential protection has been proposed. However, power differential protection cannot fully identify the fault zone for solid single-line-to-ground fault. This paper proposes a novel differential protection approach based on the Tellegen's quasi-power theorem. The approach retains the advantages of current differential protection. Meanwhile, it is not affected by load condition and distributed capacitance. This paper also proposes a time synchronization method based on the Tellegen's quasi-power theorem to calculate and correct the time synchronization error. Therefore, the proposed pilot protection has a high synchronization accuracy and has no requirement on the communication delay. In this paper, different simulation models are established by using MATLAB/Simulink and PSCAD and extensive simulation studies verify the effectiveness of the proposed protection approach and time synchronization method.

Real-Time Monitoring & Adaptive Protection of Power Transformer to Enhance Smart Grid Reliability

Abstract Power transformer is one of the most important pieces of equipment in the grid to reliably and efficiently transmit power to the consumers. Asset management and protection are the best concepts for prolongation of transformer lifespan as well as for the increase of grid reliability. This article presents electrical and non-electrical parameter-based power transformer monitoring and protection. Various data such as core flux, age of asset, heat generation, current harmonics and temperature are monitored in real time and processed accordingly to enhance the working capability of the transformer. The proposed scheme is successfully tested on 15 kVA laboratory transformer using Arm CORTEX-M4 processor. A Fitness Function (Ff) is estimated from the collected data to examine the working condition of the transformer. Moreover, voltage, current and power-based inrush detection as well as Adaptive Power Differential Protection (APDP) are applied to protect the transformer against fault. The hardware implementation and result validation prove the effectiveness of the proposed scheme in enhancing reliability of the distribution grid.

Energy and reactive power differential protection hardware‐in‐the‐loop validation for transformer application

This article focuses on validating a time-domain power system protection solution, based on energy and reactive power algorithms, through simulations using hardware-in-the-loop. The results are compared against a commercial, off-the-shelf, intelligent electronic device. The developed protection algorithms are briefly described, followed by the description of the hardware platform responsible for its practical execution and the description of the applied tests. The obtained results show significant advantages on response times when compared to traditional protection, and the ability to securely identify delicate internal transformer faults, even during inrush condition.

Research on the 2M ASON technology in power communication network

Firstly, this paper analyzes the advantages of the traditional ASON technology in the network operation, and introduces a new 2M ASON technology to solve the problems of the traditional ASON application. Secondly, this paper explains the progressiveness of the 2M ASON from the network survivability and bandwidth utilization through the introduction of the principle of 2M ASON channel establishment, the anti-node failure technology, and the “demolition before reconstruction” channel recovery mechanism. Finally, this paper analyzes the properties of the production services in the power system, and proposes a scheme of the power differential protection service based on the characteristic of the 2M ASON.

Backup protection scheme for transmission line compensated with UPFC during high impedance faults and dynamic situations

This study presents a backup protection scheme for transmission line compensated with unified power flow controller (UPFC) using power differential protection algorithm. In this scheme, power differential feature is evaluated from the apparent power flow in each phase at the local and remote bus to discriminate between the fault and normal situation. The proposed protection algorithm can be integrated with the conventional distance protection to supervise its operation during stressed conditions. Extensive fault simulation studies have been performed for different types of fault with several conditions and critical dynamic situations/issues such as load encroachment, power swing and high impedance fault (HIF). A 500 kV three machines four bus transmission system with UPFC has been used to validate the performance of the proposed scheme using MATLAB software. The test results depict that the proposed scheme is robust against HIF, power swing and load encroachment. It is not affected by the variation in pre-fault power flow angle and synchronisation delay. The proposed scheme has also been tested for current transformer (CT) and coupling capacitor voltage transformer (CCVT) transient error, which brings out the superiority of the scheme.

Improved transformer protection using probabilistic neural network and power differential method

This article presents a novel technique to distinguish between magnetizing inrush current and internal fault current of power transformer. An algorithm has been developed around the theme of the conventional differential protection method in which parallel combination of Probabilistic Neural Network (PNN) and Power Differential Protection (PDP) methods have been used. Both PNN and PDP method are independent of harmonic contents of differential current. The proposed algorithm is capable of detecting fault and its type in the eventuality of fault in the transformer. Moreover, the combination of PDP method with the PNN makes it capable to detect light internal faults for all ratings of transformers which improve the overall performance of digital differential protection scheme. For evaluation of presented algorithm, relaying signals of various operating conditions of power transformer, including internal faults, external faults, over-excitation and inrush conditions were obtained through modeling of transformer in PSCAD/EMTDC. The performance of proposed amalgamated technique (i.e. combined PNN and PDP method) is compared with the PNN, Feed Forward Back Propagation (FFBP) neural network and the conventional harmonic restraint methods. The results amply demonstrate the capability of the proposed algorithm in terms of accuracy and speed. The algorithm has been implemented in MATLAB. Keywords: Digital differential protection, Protective relaying, Probabilistic neural network, Active power relays, Power differential method.

Power differential based wide area protection

Current differential based wide area protection (WAP) has recently been proposed as a technique to increase the reliability of protection systems. It increases system stability and can prevent large contingencies such as cascading outages and blackouts. This paper describes how power differential protection (PDP) can be used within a WAP and shows that the algorithm operates correctly for all types of system faults whilst preventing unwanted tripping, even if the data has been distorted by CT saturation or by data mismatches caused by delays in the WAP data collection system. The PDP algorithm has been simulated and tested on an Iranian 400 kV transmission line under different fault and system operating conditions. The proposed operating logic and the PDP algorithm have also been evaluated using simulation studies based on the Northern Ireland Electricity (NIE) 275 kV network. The results presented illustrate the validity of the proposed protection.