Abstract—Current differential protection typically requires symmetrical communications channels—with equal latency in each direction—for correct operation. Conventionally, this has been delivered using protocols such as IEEE C37.94 over a Time-Division Multiplexing (TDM) wide-area network (WAN). Modern packet-based WANs offer improvements in efficiency, flexibility, and cost-effectiveness for utility applications. However, jitter is unavoidable in packet-based networks and, in extreme cases, jitter inevitably results in substantial asymmetrical latency in communications paths. This paper clearly defines how a new source of asymmetry arises due to the use of “de-jitter” buffers, which can jeopardize critical protection services. This is demonstrated using an analytical modelling approach, which precisely quantifies the degree of risk, and through real-time demonstration with actual devices, involving current differential protection over an IP/MPLS WAN. Using a novel method of real- time manipulation of Ethernet traffic to emulate large WANs, the modelling approach has been validated. It is shown how the sensitivity of relays to asymmetry depends on the protection settings and the magnitude of the measured load current. To address the risk of protection maloperation, a new approach for compensating for asymmetrical latency has been comprehensively validated. These developments will be of immediate interest to utilities operating, or migrating to, a packet-based infrastructure.
The L90 record shows that the 87L function is blocked at various stages throughout each test. This is due to the 87L channel being briefly interrupted as the E1 bearers change paths and resynchronise. It can be seen that at around 8 seconds before the trip command, when the DB4s switched to the alternate E1 path, the differential current rises quickly and may have resulted in a trip if the restraint did not also rise. The capture shows that the restraint increases each time the L90 detects excessive 87L channel asymmetry. This adds a level of immunity to momentary bursts of channel asymmetry, but it cannot prevent misoperation during prolonged asymmetry, without GPS compensation. With GPS, the L90 is quoted as being able to compensate for up to 10 milliseconds of asymmetry, which is well above anything measured or predicted in the AusNet Services network.
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Although demonstrated in a laboratory environment, the study uses real cases and commercially available hardware to determine the best settings in accordance with the various simulations and to show that IP/MPLS can significantly improvide the efficiency in a line differential protection communication compared with TDM solutions, whilst improving the reliability on a transport solution for electric grid wide area applications, providing utilities a step forward towards moving to a single, reliable, cost effective and integrated network.
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communications – including safety-critical teleprotection services – can be encrypted in real-time with negligible impact on performance. Furthermore, the approach described in the paper offers operational benefits for utilities and protection device vendors: authentication and encryption functionality is provided, without requiring a complex implementation within protection each protection relay, PMU, or other device; key generation can be managed automatically over time; and legacy devices and interfaces can be supported.
In digital substations with power transformers, the key to implementation of line differential protection is synchroniza- tion of electrical quantities at both two sides. System framework of current differential protection for lines between dig- ital substations is analyzed briefly, as well as the necessity of demand for time synchronization. Principle of time syn- chronization based on GPS and IEEE1588 PTP (Precision Time Protocol) are introduced. Time synchronization of cur- rent differential protection between digital substations based on IEC61850 is discussed. This paper puts forward two solution schemes of time synchronization, analyzes their advantages and disadvantages respectively, and points out that the development direction of time synchronization of differential protection between digital substations is IEEE1588 PTP.
In the modern period, the British government changed the traditional legal system and introduce unified modern legal system to administration of justice. The traditions and customs were not ignored. The British legal system was mixture of personal law, rules, local customs etc. despite the challenges British and Indian legal system did not ignore protection of consumer. Some of the important laws were passed during British time concerning consumer interest are: the Indian Contract Act of 1872, the Sale of Goods Act of 1930, the drugs and Cosmetic Act of 1940, the Indian Penal Code of 1860, the Code of Civil Procedure of 1908 etc. the policy behind all laws is to give better protection to consumer. The Sale of Goods Act of 1930 (SGA) was the main source of consumer protection by protecting interest of buyer against seller for defective goods under section 16 of the Act and praised as “Consumer‟s Charter”. It was an exception to “Caveat emptor”. The SGA was the effective legislation until 1986 than the Consumer Protection Act of 1986 was introduced in addition to the SGA. The Consumer Protection Act was enacted after the Essential Commodities ct of 1955, the Prevention of Food Adulteration Act of 1954, the Standard of Weights and Measures Act of 1976 etc. Here the consumer is not required to prove any particular intention (mens rea), means there was strict liability for wrong doer and also try to look after public interest matters rather only to focus upon private issues. In addition to the remedies under contract and criminal law, a consumer may get effective remedies under tort law. The tort provides adequate remedies which are based upon discretion power of court. Still for cheap, simple, and quick justice, a specific legislation was required to be made for consumer and then the Consumer Protection Act was enacted in 1986 with certain objectives, which are given below.
currents will be different for each fault. It means four different conditions are there for the four different faults in the DC transmission line. These conditions are checked during an internal fault to find out the type of fault that occurred in the transmission line. From the table it is clear that the type of dc line fault can be identified correctly and quickly by analysing the transient current data.
In , the dq reference frame is directly obtained by integrating the desired frequency (e.g. 50 Hz) and thus the offshore frequency is fixed at 50 Hz during the offshore AC fault. However, the offshore wind farms (OWFs) are simplified as controllable current sources and the dynamics of the WT converters are omitted. A distributed phase locked loop (PLL) based control is proposed in  to shared reactive power among WTs without communication. With the developed controller, the system can ride-through onshore and offshore AC faults but the fault detection is not addressed.
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by, for example, loss of stability and reduction of voltage. Hence, no part of power systems can safely be left unprotected, much less the busbars because of their especially vital position and function in the system. All means of protection, even those applied to the earliest and simplest system, have in some way or other contrived to satisfy the precept that all elements of the system must be protected, including busbars . Busbar is the most critical element of a power system, as it is the point of convergence of many transmission lines, transformers, generators and loads. The effect of a single bus fault is equivalent to many simultaneous faults and usually, due to the concentration of supply circuits, involves high current magnitudes. Any incorrect operation would cause the loss of all of these elements. Therefore, protection of busbar demands high speed, reliability and stability. Failure-to-trip on an internal fault, as well as false tripping of a busbar during service, or in case of an external fault, can both have disastrous effect on the stability of the power system, and may even cause complete blackout of the system . So, it is very essential to incorporate precision and reliability factors during designing a busbar protection scheme. It was a very old practice in small substations to provide over-current relays to work for the protection of the busbar and no separate relays were used for the purpose as this was not found to be cost effective. But, with the increase in substation equipments and feeder’s complexity, it was felt necessary to go for reliable busbar protection schemes. The methods most commonly used to protect busbars are frame leakage protection, direction comparison protection and differential protection.
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Although single-ended techniques remain in principle non- unit protection methods, they can be used also in closed protection zones, where the signals are communicated to the other end of the line. For instance, wavelet theory is used in , to rapidly extract the signs of the currents to use them for directional protection. Wavelet transformation has also been used for a current differential application in . In , the current differential method is modified to a travelling wave- based criterion to make the protection algorithm more robust. The important advantage of non-unit protection methods is that they use only local signals such as currents and voltages to successfully detect a DC fault. In non-unit protection methods, selectivity is ensured with the use of reactors at the ends of each line in order to define specific boundaries A series of simulations is usually needed to demonstrate that the method works as expected and exclusively for all faults within the required protection zone, while remaining idle for external faults. Nevertheless, most of these methods cannot provide individually a sufficient protection system. For instance, in , voltage and current derivative are combined to provide a fault detection means.
This paper is concern with the implementation of digital differential current protection of a single phase transformer using Arduino Uno microcontroller as a mechanism of differential relay. A power transformer functions as a node to connect two different voltage levels . The fundamental idea of the differential current protection scheme is to provide protection to the transformer if any fault occurs in the protected zone that will cause an imbalance in the differential currents. The output power in a transformer is equal to that of the input power hence, for differential current protection of the current transformers reduces the currents at the primary and secondary sides to a measureable value and in such a way that they are equal . When there is an occurrence of internal fault an imbalanced or non-zero differential current will flow through the operating coil of the differential relay which would be substituted with a microcontroller that sends a trip signal to the relays needed to open the circuit. The differential protection scheme is concerned with the faults that arise from associated difficulties such as the magnetizing inrush current and saturation. The magnetizing inrush current is a phenomenon that occurs during brief initial state of energization of the transformer even when the secondary side has no load connected to it and has its current a lot higher than the rated current [6-8]. It is transient in nature so it lasts for just a few seconds and does not cause any permanent damage to the transformer.
In the field of privacy protection, machine learning mainly focuses on the classification of supervised learning and clustering of unsupervised learning. In the field of privacy protection, machine learning mainly focuses on the classification of supervised learn- ing and clustering of unsupervised learning. Supervise learning methods in machine learning, such as support vector machines and logistic regression and other methods, to achieve the task of classifying private data [34, 35]. In , Jia proposes an approach to preserve the model privacy of the data classification and similarity evaluation for dis- tributed systems. The clustering method of unsupervised learning is more widely used in privacy protection. The problem mainly focuses on the research of wireless sensor networks [37–40], wireless multi-hop networks [41, 42] and smart grid  where the AI technologies are widely used to solve the route, service prediction and service selec- tion problem [44–47]. In , Gao thinks traditional clustering approaches are directly performed on private data and fail to cope with malicious attacks in massive data min- ing tasks against attackers’ arbitrary background knowledge. To address these issues, the authors propose an efficient privacy-preserving hybrid k-means under Spark. In , Kai et al. propose a mutual privacy preservation K-means clustering scheme. It neither discloses personal privacy information nor discloses community characteristic data (clusters).
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III. P ROTECTION OF M ULTI - TERMINAL VSC-HVDC S YSTEMS The main hurdle hampering the implementation of MT- HVDC systems is the non-availability of the protection system. Thus, a complete new technique needs to be established. It is difficult to extinguish the arc in dc systems as the polarity of current remains constant. Available protection algorithms for MT-HVDC are not satisfactory. During a dc grid fault, it is practice to operate ac switchgear to disconnect the whole dc grid: this is not acceptable. The reasons why protecting dc grids is more difficult than ac networks are : 1. Normally, cables are used in VSC-HVDC with high
Table 1 shows the results of the vertical seawater absorption test. Of the four kinds of fabrics, linen has the best seawater absorbing capacity. The seawater does not go up at all for cotton after 24h. The phenomenon suggests that linen is the best among the four kinds of fabrics that maybe used for seawater absorption to enable sacrificial anode’s function of cathodic protection at splash zone.
shape, more precisely from the wave shape of internal fault current have been proposed in . In the proposed algorithm, the Neural Network Principal Component Analysis (NNPCA) and Radial Basis Function Neural Network (RBFNN) are used as a classifier. The proposed algorithm is used to discriminate between internal faults from inrush and over-excitation condition. The algorithm also makes use of ratio of voltage-to- frequency and amplitude of differential current for detection transformer operating condition. A comparison among the performance of the FFBPNN (Feed Forward Back Propagation Neural Network), NNPCA, RBFNN based classifiers and with the conventional harmonic restraint method based on DFT method is presented in distinguishing between magnetizing inrush and internal fault condition of power transformer. The results confirm that the RBFNN is faster, stable and more reliable.
Indeed, recent observations or experimental investigations on the eﬀects of radiation have demonstrated that overall responses at ecosystemic level may not be simply derived from local responses observed at individual organ- ism level . This can be due to indirect eﬀects mediated through alteration of trophic interactions between populations of diﬀerent species [12, 13]. But more generally, this roots from “emergent” properties of ecosystems, like resilience or resistance, which drive to non straightforward propagation of eﬀects across levels of biological organisation , or through successive gen- erations [15, 16]. Similar responses have already been faced in other ﬁelds of environmental protection against other stressors, pushing a number of environment professionals to assign stronger emphasis on more systemic ap- proaches.
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In detail The operating element of a differential relay is an overcurrent element. Because the ratios of CTs provided at the different terminals cannot be perfectly matched for all operating conditions, restraining elements are also included in differential relays. The restraining elements are intended to ensure that the relay does not operate during external faults. Restraint windings provide stability from CT mismatch and CT output differences due to CT saturation. Such relays, also known as percentage differential relays, operate if the differential current is above a set percentage of restraint current. 
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Directional overcurrent protection so called all protection system. It can detect the minimum fault level and intended to operate and stabilize any fault that not intended to operate. Directional overcurrent protection is usually applied to a grid transformer’s incomer. The minimum fault level is can find at phase to earth fault which close to the source on the 132kV system the source circuit breaker is open that is back fed through the transformer. Then, the minimum fault is the contribution from the grid network. Directional overcurrent protection relays take the inputs from a set of current transformers (CT) in order to determine the amount of current flow while a set of potential transformers (VT) to determine the direction of power flow. The direction is defined by separating usually via a 90° quadrant connection of the line current with the phase to phase voltage of the other two lines [37-39].
analysis of inrush and fault current in power transformer and elimination using artificial neural network algorithm. The proposed analysis helps ANN to easily discriminate among the inrush current and fault current. In typical relay system, the relay tends to trip even at the start because of inrush current. In this paper, the offline model of relay model is built in MATLAB environment and the data is collected for inrush and fault current conditions. Since, the wavelet transform has the characteristic of multi-scale analysis and good time and frequency domain localization, fits to extract sudden- change signals in transient processes, and detects irregularity of signals very well. Further analysis using DWT is done and energy as a feature is extracted at only 7th decomposition level to decide whether the relay should trip or not using ANN algorithm. The 7 level decomposition is carried out using DWT and ANN yields 100% accuracy in results.
years. Researchers have been studying the feasibility of designing relays using microprocessors (1).Due to the advancement in digital technology and decreases in digital hardware process, digital relays are now available and being used for power system protection. Which are contribute to improved reliability and reduced costs on electric power systems (2)