Principle Of Differential Protection Research Articles

Differential protection scheme for distribution network with distributed generation based on improved feature mode decomposition and derivative dynamic time warping

With the progress of communication technology, the cost of optical fiber and 5G continues to decrease, and data transmission becomes more convenient and fast, making it possible to realize differential protection of distribution network by various intelligent algorithms using signal waveforms. Aiming at the problem that the traditional relay protection device can not meet the actual demand when the single-phase ground fault occurs in the distribution network with distributed generation, this paper proposes a new differential protection scheme. The characteristic mode decomposition improved by the whale optimization algorithm is used to decompose the zero-sequence current waveform collected at both ends of the line. Based on the basic principle of current differential protection, the derivative dynamic time warping of the component with the largest fault feature can effectively solve the problem that the grounding current of the distribution network cannot meet the working requirements of the differential protection device, and ensure the safe and stable operation of the system. Finally, based on MATLAB software, the performance of this method is comprehensively evaluated by simulating different fault conditions, so as to ensure the feasibility and accuracy of this method in the case of diversified faults when the distributed generation is used as part of the power supply.

Statistical modelling under differential privacy constraints: a case study in fine-scale geographical analysis with Australian Bureau of Statistics TableBuilder data

ABSTRACT Consistent with the principles of differential privacy protection, the Australian Bureau of Statistics artificially perturbs all count data from the Australian Census prior to its release to researchers through the TableBuilder platform. This perturbation involves the addition of random noise to every non-zero cell count followed by the suppression of small values to zero. A consequent problem encountered by researchers working with geographical TableBuilder outputs is that the aggregate sums of cell counts over fine-scale units are often much lower than the direct query totals of their coarser enclosing units. Hierarchical Bayesian modelling is here proposed as a powerful methodology for achieving consistent multi-scale statistical reconstructions suitable for downstream spatial modelling. The utility of this framework is demonstrated for the toy problem of reconstructing Multiple Family Household counts by Mesh Block in the Perth Greater Capital City area.

Analysis of an accident of abnormal increase in pole bus differential current caused by DC line faults

This paper analyzes an accident of abnormal increase of pole bus differential current and pole differential current of a converter station caused by line fault of a ±800 kV extra high-voltage direct current transmission project. After a lightning strike caused a short circuit and grounding of the DC line, the sudden voltage change protection of the DC line was triggered and the DC full voltage restart was successful. The pole bus differential current and pole differential current of the converter station have reached the protection set but have not reached the protection delay set; therefore, the differential protection has not acted. This paper first introduces the configuration principles of pole differential protection, pole bus differential protection, and line voltage sudden change protection for extra-high voltage converter stations. Second, the operation of the DC protection under this fault was analyzed in detail, and the reasons for the occurrence of pole bus differential current and pole differential current were also analyzed in this paper. Then, the range of equipment that caused the abnormal increase in differential current was identified. Finally, the lightning strike model was built on the real-time digital system, and the fault was simulated and replicated. It was determined that the abnormal increase in differential current was caused by the discharge of the pole bus surge arrester caused by the second lightning strike on the DC line.

ANALYSIS OF DIFFERENTIAL RELAY PROTECTION ALGORITHMS AND THEIR MODELLING IN MATLAB

The paper is devoted to identifying the prospects for software implementation of differential relay protection. The purpose of this study was to analyse the algorithms of the devices' operation, which allowed to create a mathematical model in the MATLAB software environment with the prospect of integration in the form of a single regional relay protection server into the unified energy system of Ukraine. It has been established that virtual models have both advantages and disadvantages compared to digital-analog devices. Their positive feature is that, due to the block principle of construction, it is possible to easily change not only the parameters but also the configuration of the primary network. The disadvantage is that the configuration of virtual protections differs from the configuration of their prototypes - real relays and terminals. The article evaluates the existing, widely used methodology and considers the actual algorithms of two-stage differential relay protection. It is established that differential protection has two stages: 1 - fast-acting differential current cut-off; 2 - sensitive differential current protection with inhibition from through current and recovery from magnetisation current surges. A simplified diagram of a fragment of the electrical system and differential relay protection of a transformer are developed and presented in MATLAB. The algorithms are considered in detail, and it is established that with their help and with the help of the considered principles of differential protection in the Simulink package, the logic of the model is implemented similarly to the logic of microprocessor-based transformer protection "RS-83DT2" of RZA Systems LLC, SPAD 346 C of ABB. Based on the modelling results, the oscillograms of primary currents of normal mode and emergency modes with external and internal short circuits are obtained. The conclusions establish the prospects of using this model and algorithms for the development of a software solution for the relay protection server and for future integration into the integrated power system.

Selective Auto-Reclosing of Mixed Circuits Based on Multi-Zone Differential Protection Principle and Distributed Sensing

Environmental concerns and economic constraints have led to increasing installations of mixed conductor circuits comprising underground cables (UGCs) and overhead transmission lines (OHLs). Faults on the OHL sections of such circuits are usually temporary, while there is a higher probability that faults on UGC sections are permanent. To maintain power system reliability and security, auto-reclose (AR) schemes are typically implemented to minimize outage duration after temporary OHL faults while blocking AR for UGC faults to prevent equipment damage. AR of a hybrid UCG–OHL transmission line, therefore, requires effective identification of the faulty section. However, the different electrical characteristics of UGC and OHL sections present significant challenges to existing protection and fault location methods. This paper presents a selective AR scheme for mixed conductor circuits based on the evaluation of differential currents in multiple defined protection zones, using distributed current transformer (CT) measurements provided by passive optical sensing. Case studies are conducted with a number of different UGC–OHL configurations, and the results demonstrate that the proposed scheme can accurately identify the faulty section, enabling effective selective AR of a comprehensive range of mixed conductor circuit topologies. The proposed scheme is also more cost effective, with reduced hardware requirements compared to conventional solutions. This paper thereby validates the optimal solution for mixed circuit protection as described in CIGRE Working Group B5.23 report 587.

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.

АНАЛІЗ РЕЖИМУ РОБОТИ ЕЛЕКТРИЧНОЇ МЕРЕЖІ ПРИ ОДНОФАЗНИХ КЗ НАПРУГОЮ 6-35 КВ

In three-phase electrical networks during the operation of power supply systems, damage to electrical equipment and difficult modes of operation are possible. Damage associated with insulation failure, rupture of wires and cables of power lines, personnel errors when switching, lead to a short circuit between the phases or on the ground. At a short circuit in a closed circuit there is a big current, voltage drop on elements of the equipment increases that leads to the general decrease in voltage in all points of a network and disturbance of work of consumers. Complex modes of operation of electrical networks occur, as a rule, as a result of accidents or after emergency shutdowns of equipment, with subsequent overloads and voltage deviations from the nominal values. And although these modes have been considered acceptable for some time, they create the preconditions for various types of damage and disorders in the operation of power grids. To ensure normal operation of electrical networks and prevent the development of accidents, it is necessary to respond quickly to changes in the mode of operation of the electrical network, immediately separate damaged equipment from serviceable and, if necessary, turn on a backup power supply. These functions are performed by relay protection and automation devices. Principles of operation of relay protection devices. 1. Current protection. Short circuits are accompanied by a sharp increase in current that exceeds the value predetermined by the calculation, which will perform simple relay protection devices that can control the value of currents. Separate the maximum current protection, which acts to disconnect the damaged network element with a time delay and current cut-offs, which operate without a time delay. The difference between them is in the choice of how to ensure selectivity. The currents controlled by the relay protection device can be measured in phases (through current transformers), or individual components of phase currents can be measured (currents of direct, reverse and zero sequences. This method is based on the method of symmetrical components). Current types of protection are divided with control of power direction (directional) and without control (non-directional). Current protection works on the principle of operation not only in case of damage to one of the network elements, but also to adjacent ones. Therefore, current protection is referred to as protection with relative selectivity. 2. Differential protection. The basis of the principle of differential protection is the comparison of homogeneous, instantaneous values at the ends of the protected element of the network (transformer, busbar section, generator, overhead line). Usually compare currents in magnitude and phase. Differential protection by its principle works only in case of damage to the protected element of the network, so it is performed without time delay and differential protection is called protection with absolute selectivity. 3. Remote protection. In the event of short circuits in the electrical network is not only a sudden increase in current, but also a sharp decrease in voltage, ie a decrease in resistance. The advantage of relay protection devices based on this principle is that the resistance to the fault does not depend on the current and voltage, but only on their ratio. This allows protection at short-circuit currents less than the nominal for electrical equipment. Single-phase earth faults account for about 70% of all damage to electrical equipment. According to the Rules of technical operation in the event of a single-phase short circuit to "ground" in 6-35 kV electrical networks, relay protection devices must act either to turn off the equipment or to "signal". At the enterprises with special working conditions and the increased risk of damage of the equipment and defeat of people by action of an electric current protection against single-phase short circuits on the earth operates on shutdown with the minimum endurance of time. Thus, after the analysis of the modes of operation of power supply systems, the importance of using switching devices of relay protection to ensure normal operating conditions of electrical networks and prevent accidents is confirmed. Also, the use of relay protection devices must be justified for each individual electrical equipment according to the principles of operation and characteristics of the proper functioning of the switching apparatus. In case of emergencies, namely single-phase earth faults, 6-35 kV electrical network operation modes and operation of single-phase earth fault protection are performed according to various technical parameters, depending on the type and connection scheme of the neutral of this power system.

Types of transformer overload protection

Electrical equipment and circuits in substations must be protected to avoid and control a variety of damage due to abnormal currents and uneven voltage. We will look at how to install and why you need relay protection of transformers against overload, the principle of differential protection and other control processes with fuses.

A Differential Privacy Support Vector Machine Classifier Based on Dual Variable Perturbation

Data mining technology can be used to dig out potential and valuable information from massive data, and support vector machine (SVM) is one of the most widely used and most efficient methods in the field of data mining classification. However, the training set data often contains sensitive attributes, and the traditional training method of SVM reveals the individual privacy information. In view of the low prediction accuracy and poor versatility of the existing SVM classifiers with privacy protection, this paper proposed a new SVM training method for differential privacy protection. The algorithm first solved the dual problem of SVM by using SMO method and the difference $E_{i}$ between the estimated value and the real value for each support vector was recorded. Then the ratio of the $E_{i}$ of each support vector to the sum of the $E_{i}$ of all the support vectors was calculated. Next, different levels of Laplace random noise were added to the corresponding dual variables $\alpha _{i}$ of each support vector to be released, according to the ratio of each support vector. According to the principle of differential privacy protection, the algorithm meets $\epsilon $ -differential privacy which can be used to effectively protect individual privacy. Experimental results on real datasets showed that the algorithm proposed in this paper could be used for classification prediction under a reasonable privacy budget.

Evaluation of Capacitive Current Compensation Strategies to Current Differential Protection for Long Distance Transmission Lines

In UHV and EHV, distributive capacitive current to current differential protection has serious problem. Nowadays, to deal with the problem of distributed capacitive current a stimulating modern technology is being used in current differential protection with high operating threshold. Many schemes have been used into current differential protection for capacitive current compensation, which was based on shunt reactor, phasor compensation algorithm, Bergeron method. Those techniques were also reducing operating speed and sensitivity of current differential protection. To solve the problem of distributed capacitive current of the line, novel principle of current differential protection is described in this article. Current calculated from set point to both the ends give rise to a differential criterion. Differential protection is launched under the phenomenon of low sampling frequency to improve the expediency of the criterion. The calculation of set point distributed current is achieved at low sampling frequency by adding an interpolation point at each sampling interval. The point is set in the middle of the line and the calculation for magnitude of the current is done with half data window absolute value integrals, for improved the operating speed of the current differential protection.

Differential Protection in Low-Voltage Buses: An Exploration of Principles and Models

Current-differential principles are well known and commonly used for the protection of medium and large transformers, large motors, medium-voltage (MV) generators, MV and high-voltage buses, and any type of important power equipment with measurable input and output currents. However, is it practical to protect low-voltage (LV) distribution buses using differential protection? This article describes bus differential protection principles as well as interlocking principles for overcurrent protection. We discuss specific issues in applying differential protection in LV systems. Additionally, we present a concept of partial differential (PD) protection, which can be used in conjunction with zone-selective interlocking (ZSI) or as backup to traditional overcurrent protection to achieve high-speed and selective fault clearance. Additional concepts for the implementation of bus differential protection using networked data in LV systems are introduced.

Principle and Implementation of Current Differential Protection in Distribution Networks With High Penetration of DGs

With the high penetration of distributed generations (DGs), the conventional radial distribution network is becoming an active distribution network (ADN). It has the characteristics of multisource, multibranch, bidirectional power and fault current flow, as well as weak infeed. To provide effective protection for such a network, a novel current differential protection scheme, together with new implementation technology, is proposed in this paper. In this scheme, instead of using phase currents, a positive-sequence fault component (PSFC) is introduced into the differential protection. By building the PSFC equivalent circuit of the ADN, the distribution characteristic of PSFC within the ADN is theoretically analyzed in detail, especially for the case when the ADN contains inverter interfaced DGs. The PSFC-based differential protection criteria for different types of feeder are then established and simulated. To put the scheme into practice, data self-synchronization and peer-to-peer communication techniques are established. Based on this principle and using an advanced hardware platform, a protection prototype is successfully developed and tested. The test results verify the feasibility of the proposed protection scheme.

Current differential protection principle of HVDC transmission system

Traditional high-voltage DC (HVDC) current differential protection has problems on identifying fault current and has long delay. In this study, a novel current differential protection principle for HVDC transmission lines is proposed. By the adoption of distributed parameter model, differential current criterion is formed at a selected point on the transmission line. When fault occurs on DC line, setting point differential current reaches a high value. When no fault occurs or fault occurs outside the DC line, setting point differential current reaches a small value. Comparing with the traditional current differential protection, the proposed principle eliminates the impact of distributed capacitive current and has no requirement of delay. Comparing with travelling wave protection, fault identification can be performed during both transient and steady states, and the proposed method has reasonable sampling frequency requirements and has high reliability. Simulation analysis shows that the proposed principle identifies faults reliably and rapidly. The proposed principle is theoretically novel and practically applicable.

Testing Microprocessor-Based Numerical Transformer Differential Protection

Transformer differential protection application has always been a challenge to protection engineers and commissioning personnel, even with older electromechanical and solid-state technologies. The emergence of microprocessor-based protection, where the intelligence is implemented numerically in software algorithms, and the fact that different relay models, even from the same manufacturer, apply different algorithms and compensation techniques and use different terminology and notation, has made it increasingly more complicated to apply the protection and even more challenging to correctly test them during commissioning. This paper reviews how phase differential protection principles are implemented in numerical technology by different relay models, provide guidance in their application, and guide test personnel in performing their work. Test methods are proposed for use with modern test systems that can be applied to test all transformer phase differential protection functions easily and effectively.

The Research of Portable Charging Pile Detection Device Based on Electric Vehicle

本文提出了一种应用于充电桩现场测试的基于电动汽车的便携式充电桩检测装置。该装置针对现有的充电桩现场测试系统，通过将负载、控制单元、显示屏和计量等融于一体，采用差动保护原理、限流原理等实现对充电桩性能、功能、稳定性、互联互通和计量计费准确性的测试，并直观输出测试结果给测试人员。本装置体积小、重量轻，涵盖了现有充电桩的所有测试项目，可直接替代电动车对充电桩进行全面检测。 This paper presents a portable charging pile detection device based on electric vehicle for field test of charging pile. The device, based on the existing charging pile field test system, combining the load, control unit, display and measurement all together, uses differential protection principle, current limiting principle to achieve the performance of charging pile, stability, interoperability and measurement of billing accuracy of the test, and visual test output to the test results. The device is small, light weight, covering the existing charging pile of all test items, and can directly replace the electric car charging pile to conduct a comprehensive test.

Distributed protection for smart substations based on multiple overlapping units

Taking advantage of the information sharing mechanism in smart substations, a distributed protection based on multiple overlapping units is introduced in this paper. The area division and the construction of protection units are studied based on the principle of differential protection. Mutual perception and information interaction among units, calculation with multisource information and coordinated protection schemes are proposed to improve the reliability and adaptability of the substation protection system. A multi agent system (MAS) approach is used to model the units' working process in various situations, such as communication failure and sampled data failure. Test results demonstrate that the method can accelerate the backup protection as well as reduce the power-off range.

Adaptive busbar differential relaying scheme during saturation period of current transformers based on alienation concept

This study presents an advanced technique provided with adaptive differential relay characteristics for avoiding current transformer (CT) saturation effects. The proposed technique uses the alienation and differential protection principles to make adaptive logic; if no CT saturation is detected, the differential principle alone is capable of tripping the busbar. If CT saturation is detected, both the alienation and differential principles must pickup in order to trip. The alienation coefficient is useful in CT saturation detection, evaluation of CT saturation degree and adapting the differential relay characteristics during saturation period of CTs to avoid false operation in the event of external faults. The differential current and alienation coefficient are calculated from two terminal currents of the busbar. The proposed protective scheme has several attractive features, including the simplicity of on-line implementation, not affected by the remanent flux in the CT core, and it is independent of the CT parameters/characteristics and secondary burden. A real 19.57 kV busbar is simulated using Alternate Transients Program/Electro-Magnetic Transient Program and MATLAB packages to examine the suggested scheme under different types of faults. Under normal operating conditions and external faults, the scheme remains stable and it operates only for the case of internal faults. Moreover, it is unaffected by CT saturation.

Current Differential Protection for Distributed Transmission Lines using Low Sampling Frequency

Current differential protection has been affected negatively by the distributed capacitive current of transmission lines. In order to solve the problem of distributed capacitance current of transmission line, the current differential protection in this paper is based on distributed parameters model of the transmission line. The current formula along with the transmission line is derived under this distributed parameter line model. The differential criterion is constructed with the current calculated from both ends to the set point. In order to improve the practicality of the criterion, the implementation of the differential protection is given under low sampling frequency. By adding a cubic spline data interpolation point at each sampling interval, the calculation of the set point distributed current under low sampling frequency is achieved. In order to improve the operating speed of current differential protection, the point is set at the midpoint of the line, and the magnitude of the current is calculated with a half data window absolute value integrals. The results show that the proposed novel current differential principle is not affected by the distributed capacitance current. It has obvious advantages compared with traditional current differential protection principle for the low sampling frequency requirement, fast action speed and the small amount of computation.

A New Transmission Line Pilot Differential Protection Principle Using Virtual Impedance of Fault Component

A novel line pilot differential protection principle based on the virtual impedance of fault component is proposed in this paper. First, according to the fault component of the measured current and voltage at both line ends, the fault component of the current and voltage at the line midpoint is calculated. Second, the virtual impedance is defined as the calculated voltage fault component divided by the calculated current fault component. And then, according to the two virtual impedances calculated at two line ends, the ratio restraint criterion is formed with the sum of the virtual impedances and the smaller virtual impedance. Finally, by analyzing different characteristics of the criterion in different fault cases, the fault can be identified. Simulation results verify that the proposed method is able to identify different kinds of fault accurately with high sensitivity. It is highly reliable and not affected by the fault location, transition resistance, load current, distributed capacitance, and data synchronization. Even in the case of transitional fault, selectivity can still be guaranteed with the proposed method.

Protection for DC Distribution System with Distributed Generator

DC distribution system has advantages of high power quality, large transmission capacity, high reliability, simple structure, economy and low energy consumption, and so forth. It has been a key part of smart grid nowadays. However, the development of DC distribution system is constrained by the lack of operational experience in DC system, the small interrupting capacity of DC circuit breaker (CB), and the lack of protection schemes for system itself. In this paper, protection for DC distribution system with distributed generator (DG) is fully investigated and verified. Firstly, the electromagnetic transient model of DC distribution system with DG is presented. Simulation based on the electromagnetic transient model is carried out. Both the step response and the steady-state performance verify the accuracy of the model. Then the fault characteristic mechanism is analyzed, and the protection principles and scheme are investigated in detail, including voltage mutation principle as protection starting component, differential current protection principle for DC bus, and two-section current protection for distribution lines. Finally, transient responses with protection scheme are analyzed during faults. The results present that the protection principles and scheme are feasible for DC distribution system with DG.