Line Protection Device Research Articles

Research on new distributed distribution network hidden fault remote automatic recovery technology

Abstract To solve a series of chain reactions in which a fault in the distribution network triggers the shutdown of other components, a new distributed distribution network hidden fault remote automatic recovery technology research is proposed. The traditional chain fault model about line protection describes that when a fault occurs on one or some lines of the system, the line protection devices will operate with a certain probability, and the misoperation or inappropriate action of these line protection devices will lead to the expansion of the fault and ultimately form a wide range of power outages. This study quantitatively gives the interaction relationship between the components in the system. Firstly, the difference between the distribution network chained fault and the main network chained fault mechanism is analyzed; secondly, the topology of the distribution network is modeled; then, the fault transfer model of the distribution network and the chained fault model based on the line dynamics model are constructed based on this model; finally, the detailed distribution network chained fault algorithm process is given based on the proposed model.

Research on electrical automation devices under embedded real-time operating system design

Abstract As the scale of the electrical system becomes more and more large and the structure becomes more and more complex, the performance of the electrical automation device is therefore required to be higher. This paper studies the electrical system automation device, and from the perspective of universality, designs and establishes the hardware platform of the electrical system automation device composed of six plug-ins, such as human-machine interface, auxiliary switch input, AC input, communication, power supply, and central processor. On this basis, μC/OS-II is adopted as the embedded real-time operating system of this paper to develop and design the software of the electrical system automation device. Then, the principle of the protection device for embedded system electrical automation is analyzed, and a microcomputer line protection device based on the full-circle Fuchs algorithm is proposed. The empirical analysis of the embedded system electrical automation device shows that the maximum system task response time is 145 μs and the minimum is 10 μs, which are all no more than 1 ms. When testing including the single board state, the keyboard, the alphabetical mode, the basic function, and the single board line module sending and receiving, the pass rate of all the testing items is more than 99%, which verifies that this paper is based on the embedded real-time operating system of the feasibility and effectiveness of the electrical automation device.

Tie line fault ride‐through method of photovoltaic station based on cooperative strategy of energy storage, relay protection and photovoltaic inverters

AbstractThe fault of the tie line between the photovoltaic (PV) station and the grid is a serious fault for the PV station. It will cause the PV station to operate into an unintentional island. The uncontrolled Island voltage and frequency will inevitably lead to the disconnection of the inverter in the station. This situation will bring great losses to PV operators and impact to the power grid. In order to deal with the tie line fault, this paper analyzes the operation characteristics of PV stations in case of tie line fault firstly. Then a tie line fault ride‐through method based on cooperative strategy of small capacity energy storage (ES), relay protection and PV inverters is proposed. The islanding switching control strategies of PV and ES are designed respectively. The cooperative strategy of protection, PV controller and ES controller is formulated as well. The real‐time digital simulator (RTDS) closed‐loop test platform including line protection device, ES controller and PV controller is built to verify the effectiveness of the proposed method.

Substation-area Backup Protection Scheme for the Failure of 10kV Line Protection Device

The research on wide-area backup protection for high-voltage transmission lines has made certain progress in recent years, but there are few reports published on substation-area backup protection for low-voltage 10kV transmission lines. Based on the characteristics of shared information in intelligent substation, a substation-area backup protection scheme to deal with the failure of 10kV line protection device is proposed in this paper. This scheme uses the device self-test information and heartbeat mechanism to monitor the operation status of 10kV line protection devices; to realize the substation-area backup protection for the 10kV transmission lines when any line protection device fails, the protection criterion is constructed by the action results of power directional elements of transformer protections and other 10kV line protections. The proposed scheme can greatly improve the speed of the fault isolation and has low requirements for data demand and synchronization. PSCAD simulation results show that the proposed method is with high correctness and feasibility.

Research on automatic physical testing method of relay protection equipment through data fusion technology

Intelligent substations can accomplish deeper and more complex substation information exchange and processing by virtue of their equipment intelligence and data integration. In this paper, a relay protection equipment test system for intelligent substations is investigated for intelligent relay protection equipment. By applying data fusion technology in the testing process, functions such as automatically obtaining the action information of secondary devices and judging the response status of secondary devices can be accomplished. Applying the test system proposed in this paper to high-voltage line protection devices, the results show that the relay protection equipment test system can optimize the relay protection equipment test process, which further improves the accuracy and efficiency of relay protection equipment testing.

Real-Time Circuit Breaker Availability Assessment in the Transmission Network

Circuit breakers (CBs) in the transmission network are the basic elements for energy flow control. CB diagnosis represents a decisive action for increasing power system reliability and safety. Their actual availability status and ability to perform major functions can sometimes be difficult to determine. This paper presents a general state estimation model based on fuzzy logic (FL), membership function (MF), and expert knowledge for diagnosis schemes to handle unclear information in the diagnosis procedure. The proposed model uses inputs from the Supervisory Control and Data Acquisition (SCADA) system, data on the position and state of the switch, changes in current in the network element CB (NECB), start or trip action of a protection relay on the NECB, and alarm status of the CB. For the diagnostic system input variables, data from the SCADA system, along with transformer and line protection devices, are used to allow the proper formation of rules and ultimately to determine the diagnostic status of the CB. The proposed method is tested on an authentic test power system, and the outcome results are compared with a previously reported technique. The obtained test results and the comparison prove the efficiency, authenticity, and fast operation feature of the suggested strategy.

An Enhanced Algorithm for Conventional Protection Devices of Transmission Lines With DTLR

As the installed capacity of renewable generation continues to increase nowadays to satisfy both emissions and economic requirements, the nature of intermittent generation results in a need to further increase transmission capacity. Dynamic thermal line rating may be used to increase the capacity of transmission lines without upgrading infrastructure. However, existing transmission line protection devices may mal-operate due to the increased capacity. So, it is required to evaluate the performance of existing protection devices. This paper proposes an algorithm that enhances the performance of existing conventional relays such as distance and overcurrent relays. The proposed algorithm is based on a combination of dynamic thermal rating, current ratio of negative and positive sequences and voltage criterion to detect faults whether symmetrical or asymmetrical and unsafe overload. In addition, it aims at restraining the existing relays during safe overloads. A model of a system under investigation is simulated, with studies are performed in MATLAB/Simulink environment. The results demonstrate the ability of the proposed scheme to detect all types of faults and unsafe overload dependably and restrain the conventional relays securely during safe overloads.

Compensation voltage moduli comparison‐based wide‐area protection algorithm independent of data synchronism and integrity

Secondary direct-current loss within a substation is a severe event. In China, each line protection device is generally powered by one set of secondary direct current (DC) power system within a substation of 110 kV voltage level. In this case, the line protection devices will be immediately taken out of service when the secondary DC is lost, and the lines protected by them will lose their corresponding protections. Once a fault occurs on the line, only the remote back-up protection can be relied on to isolate the fault, which expands the fault influence and increases its clearance time. To handle the above problem, a novel wide-area protection algorithm based on compensation voltage moduli comparison is proposed, which is independent of multi-terminal data synchronism. Then, a comprehensive protection strategy composed of the proposed protection algorithm and the original local distances protection is proposed. The results from a power systems computer aided design/electromagnetic transients including DC (PSCAD/EMTDC)-based simulation verify that the proposed protection algorithm has higher sensitivity. The comprehensive protection strategy could cope with most line faults effectively, even if only partial data are available, the selectivity and speed of which are better than that of distance protections.

IMPACT OF REAL AND REACTIVE POWER CONTROLLABILITY OF STATCOM ON TRANSMISSION LINE PROTECTION

Static synchronous Compensator (STATCOM) is a shunt connected Voltage Source Converter (VSC) based FACTS controller which is useful in improving the voltage regulation. VSC based FACTS controllers facilitate connection of energy storage devices like battery, fuel cell, Super Magnetic Energy Storage(SMES) etc. at the DC bus. Addition of energy storage device results in better real and reactive power flow control, transient stability enhancement and power oscillation damping. However, FACTS controllers with energy storage device in the line poses new challenges for the line protection device. Operating region of STATCOM with energy storage device (STATCOM – ES) encompasses all the four quadrants in P – Q plane. Impedance contribution by STATCOM operating in any of these four quadrants can modify apparent impedance seen by distance relay and hence needs to be investigated thoroughly. Main aim of this paper is to analyze the impact of emulated conductance and susceptance by four quadrant operation of STATCOM on the performance of distance relay in a hybrid compensated system. A novel control strategy to dynamically modify the reference for real power exchange by STATCOM is proposed to avoid damage to the STATCOM during fault. Possibilities of distance relay under reach and over reach due to operation of STATCOM - ES in various operating modes and impact of fault resistance on the relay performance is discussed.

Problems Found During Testing Synchronous Digital Hierarchical Devices Used on Power Protection Systems

This paper examines testing methods and devices for sending data to line protection devices using the synchronous digital hierarchical (SDH) protocol. The paper has arisen as a result of cooperation between the Institute of Power Engineering and the Polish Power Electrical Utility Operator (PSE). The main objective of the tests was to investigate the possibilities of using already installed or new SDH telecommunication devices in power system protection systems. A range of protection functionality tests was considered along with SDH devices tests that focused on certain conditions and possible problems that may occur during normal operating conditions.

A Novel Pilot Protection for VSC-HVDC Transmission Lines Based on Correlation Analysis

The control system of voltage source converter HVDC (VSC-HVDC) is complex and its fault tolerance ability is not sufficient, and correct rate of line protection device is not high. A novel pilot protection for VSC-HVDC transmission lines based on correlation analysis is proposed in this paper. In the principle, external fault is equivalent to a positive capacitance model, so the correlation coefficient of the current and voltage derivative is 1; while the internal fault is equivalent to a negative capacitance model, so the correlation coefficient of the current and voltage derivative is -1. Internal faults and external faults can be distinguished by judging the correlation coefficient. Theoretical analysis and PSCAD simulation experiments show that the new principle, which is simple, not affected by transition resistance, control type and line distributed capacitance current, can identify internal faults and external faults reliably and rapidly, having certain practical value.

Design of Systems of Covered Overhead Conductors by Means of Electric Field Calculation

Recently, in medium voltage overhead line systems, previously bare conductors are being replaced with conductors covered with a layer of insulation. Covered conductors enable an economical increase in operational reliability. At the current stage of development, there are several ways of replacing bare conductors with covered ones. Such a replacement also requires changing the accompanying line accessories, insulators, and line protection devices. The selection of the optimum combination of covered conductors and equipment has been done by means of electric field calculations. The optimization parameters have included the use of existing equipment to the maximum possible extent, new elements of equipment that have to be added, and the prevention of disturbances and failures in operation. Theoretical findings have been confirmed with laboratory tests on prototype combinations of covered conductors and the accompanying equipment.

Effective Utilization of Surge Protection Devices

A systematic method is described for selecting the energy rating for surge protection devices when coordinated with a known impedance and subjected to typical low-voltage ac transients. A review of line transient generation characteristics, source impedance determination, and load surge protection device characteristics is given. From this study, an analytical model of the source, line, and load protection device is presented with closed-form mathematical expressions for suppressor current and energy. Results are obtained and compared for a unidirectional voltage impulse, a decaying oscillatory voltage wave, and a unidirectional current wave. From the analysis, the effect that line impedance has on each of these waveforms is shown graphically. In addition, the validity of the analytical model is confirmed experimentally.