Selection Of Protective Devices Research Articles

Fault detection through discrete wavelet transform in overhead power transmission lines

AbstractTransmission lines are a very important and vulnerable part of the power system. Power supply to the consumers depends on the fault‐free status of transmission lines. If the normal working condition of the power system is disturbed due to faults, the persisting fault of long duration results in financial and economic losses. The fault analysis has an important association with the selection of protective devices and reliability assessment of high‐voltage transmission lines. It is imperative to devise a suitable feature extraction tool for accurate fault detection and classification in transmission lines. Several feature extraction techniques have been used in the past but due to their limitations, that is, for use in stationary signals, limited space in localizing nonstationary signals, and less robustness in case of variations in normal operation conditions. Not suitable for real‐time applications and large calculation time and memory requirements. This research presents a discrete wavelet transform (DWT)‐based novel fault detection technique at different parameters, that is, fault inception and fault resistance with proper selection of mother wavelet. In this study, the feasibility of DWT using MATLAB software has been investigated. It has been concluded from the simulated data that wavelet transform together with an effective classification algorithm can be implemented as an effective tool for real‐time monitoring and accurate fault detection and classification in the transmission lines.

PROTECTION DEVICES AND SELECTIVITY IN DC POWER DISTRIBUTION SUB-SYSTEMS

DC power distribution sub-systems are essential components of electrical power facilities since they allow the carrying out of vital facility functions in normal operation even in the event of a collapse in grid voltage. Therefore, such systems should be a reliable and safe source of electrical power. When taking into consideration that the manner of terminating DC current is significantly different from terminating AC current, it is important that, when designing DC power distribution sub-systems in electrical power facilities, care be taken concerning their characteristics. A proper selection of protection devices (low-voltage fuses and circuit breakers) and their proper allocation according to distribution protection levels achieves protection selectivity. This paper presents the basic types of protection devices and their possible uses in DC power distribution sub-systems and the manner of achieving protection selectivity.

Control-Based Two-Layer Protection for Short-Circuit Fault at an LVDC Feeder Branch

Low-voltage dc distribution offers high efficiency for grid integration of dc-based technologies such as photovoltaic and battery storage systems and new loads such as charging stations for electric vehicles due to reduced number of conversion stages. However, the selection of protection devices, protection coordination and selectivity is still subject to research. This work proposes to use a two-layer protection technique utilizing the control capability of power converters in case of a short-circuit fault at branch level of a low voltage dc feeder. The first layer is limiting the bus current using a virtual resistance in the droop control to avoid tripping of the grid-forming converter. The second layer implements a soft fuse tripping technique for selectivity. The control concept is presented and the system stability is analyzed using impedance-based stability analysis. Experimental results on a hardware-in-the-loop setup verify the findings.

A New Guidance for Circuit Breaker Rate Selection Including the Impact of Zero-Sequence X/R Ratio

The multiplying factor (MF) is critical for the correct design, sizing, and selection of protection devices in a power system. This factor depends on the X/R ratio at the point of failure. The standards establish an equivalent MF for the X/R ratios for both three-phase and single-phase fault accordingly for engineering practices. However, X/R ratios for single-phase faults ignore how much from the total X/R ratio comes from the positive-sequence or zero-sequence X/R ratio. This research demonstrates that the total X/R ratio at the point of failure is not the only variable that affects how the multiplying factor changes. The results demonstrate with dynamic short-circuit simulations using EMTP-ATPDraw, which it is also necessary to establish the MF considering the differences of the X/R ratios of each sequence, respectively. To support the engineering designer in the correct selection of the protection device, this article proposes a methodology complementary to the standards, which allows establishing the multiplying factor using the X/R ratios of positive and zero sequence separately. The results show that both oversized and undersized design situations can occur when ignoring the zero sequence in particular scenarios.

The Method of Selecting Protection Devices in the Automated Design of an Electrical Complex of a Transport Vehicle

The article describes the mathematical and software module of computer-aided design of vehicle electric systems: selection and verification of protective devices. The following problems are solved: calculation of currents in the circuit sections of scheme for normal and directive modes taking into account the changes in the current distribution as to the modes of consumption, calculation of the currents in the circuit sections of design scheme for short-circuit modes, checking the correct choice of protection devices as to the rated current, checking the correct selection of protection device in overloads in case of electric motor loads, determining the sequence of triggering of protection devices in the modes of short-circuit and checking the selectivity of protection, checking the protection devices for resistance to short-circuit currents

A new multiple-risk map approach to solve process plant layout considering safety and economic aspects

Mathematical models used to optimize the process plant layout (PPL) with risk reduction have four primary objectives, which are related to the minimization of land, pumping (pipe system), protection system devices, and risk costs. Moreover, these models are of two types: continuous plane models (CPM) and grid-based models (GBM); however, the nonconvexity of the CPM models makes difficult to achieve the global optimum, because it is formulated as Mixed-Integer Nonlinear Programming (MINLP). Thus, the risk map approach has been implemented with the grid-based models to solve problems of process plant layout focused on finding the best possible solution. However, these risk map formulations present important limitations, mainly related with the use of protection devices and the occupied area. Therefore, a new GBM-MILP formulation is proposed to optimize the selection of protection devices and minimize the occupied area. The risk is reduced through the investment on safety devices instead of considering the increase of separation distances. The proposed model was used to solve the layout problem of an ethylene oxide process, and the results was compared with a process layout reported in the literature. The results show that the model can provide the best possible solution; however, the time spent in the calculation is considerably greater than that reported for continuous plane models. Finally, the model can be used by decision-makers to evaluate different layout options for several explosion scenarios, during the early stages of the plant design.

Testing and Improving an ISO 14119-Inspired Tool to Prevent Bypassing Safeguards on Industrial Machines

Various safety-related standards associated with the machinery design phase, such as ISO 14119:2013, emphasize the appropriate design and selection of protective devices to prevent bypassing. Despite such standards, bypassing safeguards is a common issue at the machinery use phase. ISO 12100:2010 indicates, “experience has shown that even well-designed safeguarding can fail or be violated”. This unsafe practice can cause serious injuries or fatalities. This paper presents an improved version of a bypassing-related assessment tool initially inspired by ISO 14119. The improvement results from testing its performance through industrial case studies to explore how the tool works in reality. Five occupational health and safety (OHS) practitioners apply this tool in four plants in Quebec to 18 machines and 37 activities. Afterwards, the OHS practitioners provide feedback using a questionnaire. The findings reveal that the tool is appropriate for the machine usage phase to prevent bypassing with an overall 82% satisfaction score. The probability levels of bypassing given by the tool enable a safety improvement prioritization method for the machines and safeguards. The tool was improved, redefining some incentives to bypass and its layout. The findings explain how practitioners could influence decision-making to minimize incentives to bypass and the probability of bypassing to prevent accidents.

Photovoltaic and Wind Turbine Integration Applying Cuckoo Search for Probabilistic Reliable Optimal Placement

This paper presents an efficient Cuckoo Search Optimization technique to improve the reliability of electrical power systems. Various reliability objective indices such as Energy Not Supplied, System Average Interruption Frequency Index, System Average Interruption, and Duration Index are the main indices indicating reliability. The Cuckoo Search Optimization (CSO) technique is applied to optimally place the protection devices, install the distributed generators, and to determine the size of distributed generators in radial feeders for reliability improvement. Distributed generator affects reliability and system power losses and voltage profile. The volatility behaviour for both photovoltaic cells and the wind turbine farms affect the values and the selection of protection devices and distributed generators allocation. To improve reliability, the reconfiguration will take place before installing both protection devices and distributed generators. Assessment of consumer power system reliability is a vital part of distribution system behaviour and development. Distribution system reliability calculation will be relayed on probabilistic reliability indices, which can expect the disruption profile of a distribution system based on the volatility behaviour of added generators and load behaviour. The validity of the anticipated algorithm has been tested using a standard IEEE 69 bus system.

Influence of contact network parameters on value of current rise speed during short circuit in power circuits of electric rolling stock

Purpose. Influence investigation of contact system parameters on current rate of rise during short circuit, and the difference of these parameter values under different connection diagrams of traction motors in the power circuit. Methodology. The mathematical model and method for determining the effect of the contact system parameters, such as inductance and active resistance of the contact wire, on rise speed during the short circuit current were offered. Besides that, it is determined the influence of current speeds on their difference in power circuits of DC electric locomotive in different points of short circuit, different variants of traction electric engines connection and different distances of electric locomotives from the traction substation. The proposed model and method can be used for any type of electric DC locomotive at any point of a short circuit in traction engine circuit. Findings. Qualitative and quantitative influence of contact system parameters on values of current rise speed during short circuit and on the differences value of these parameters with different connection diagram of traction electric engines was established. Originality. The investigation method concerning determination of the influence of contact system parameters on current rise speed in short circuit and on the difference of these parameters on different distances of electric locomotives from traction substation was proposed. Practical value. The results can be used in selection of protective devices of rolling stock power circuits, where the main parameter is the current rise speed during the short circuit.

An expert system for integrated protection design with configurable distribution circuits. I

An integrated expert system for protection system design has been developed, for an engineering workstation, using a relational database management system. The expert system incorporates both procedural and declarative, or query, operating modes. Rules dealing with the coordination, placement and selection of protective devices are used to incorporate expert knowledge into the knowledge base. The protection system designer controls which rules are implemented in the design.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

An expert system for integrated protection design with configurable distribution circuits. II

For pt.I see ibid., vol.9, no.2, p.1108-14 (1994). An example protection system design is presented using an integrated expert system developed for an engineering workstation. The example problem consists of three interconnected distribution circuits. Dynamic knowledge, created by the expert system from the rules and system data, is used in the design. System data is presented pertaining to the circuits along with the created dynamic knowledge. The implemented rules dealing with the coordination, placement and selection of protective devices are presented, along with all associated parameter values. The final design and results are shown.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Protection, control, alarm and auxiliary equipment for EHV substations

Faults on EHV systems can prove to be expensive for both supply authority and user. Careful selection of protective devices and ancillary equipment will minimise damage to plant and outage times

Protection of Auxiliary Power Systems in a Nuclear Power Plant

This paper outlines the electrical protection for the 4.16 kV and 480 V auxiliary power systems in a nuclear power plant. The paper describes the protection philosophy, selection of protective devices, and the bases of their coordination and settings.

Crankcase Explosions: An Investigation into Some Factors Governing the Selection of Protective Devices

Remedies which have been suggested for crankcase explosions include the use of warning devices to detect over-heating in the crankcase, and the provision of relief vents to limit the explosion pressure to a safe value. Data were obtained experimentally at the Thornton Research Centre for the conditions necessary for the ignition of mists of lubricating oil in air in order that the margin of safety offered by a detector of overheating might be more fully assessed. The venting of explosions was also studied both on a rig scale and in the crankcase of a Diesel engine of 1,100 h.p. The results indicated that it would not be practical to provide sufficient venting area on an engine of this size, to limit the maximum explosion pressures to a safe value for the more violent explosions which might occur. For venting to provide complete protection, it would seem necessary to take measures to prevent the flame from spreading throughout the whole crankcase.

Protection of low-voltage circuits by air circuit breakers in cascade arrangement

This paper deals with and outlines a new solution to the problem of providing adequate short circuit protection for low-voltage distribution systems and circuits operating at 600 volts or less. Recent tests and field experience have dispelled the illusion that protective devices of very limited interrupting ability will satisfactorily protect any low-voltage circuit. A recently published calculating procedure makes possible the accurate determination of the short circuit currents obtainable in low voltage circuits or systems. Modern types of low-voltage air circuit breakers in a wide range of interrupting ratings are now available. While the best short circuit protection is obtained by selecting those of interrupting ratings at least equal to the calculated short circuit current, such a procedure is not always justifiable. In many instances a relatively large number of main feeder circuits, emanating from a bus fed through one or more main breakers or incoming line breakers, supply an even larger number of branch feeders. The short circuit currents obtainable at the branch-feeder breaker locations may not be materially less than those obtainable at the main bus. Yet the selection of branch feeder breakers, or possibly even main feeder breakers, with interrupting ratings high enough to match these obtainable currents, may prove completely impractical when viewed with any reasonable regard for space requirements or cost. Air circuit breakers of varying interrupting ratings, properly coordinated in design may be used in a “cascade” or series connection in such manner that in event of a severe fault, the main breakers “back-up” the smaller main feeder breakers, and these, in turn, “back-up” the branch feeder breakers. Only the main breakers need have interrupting ratings equal to the obtainable short-circuit current, yet the system is adequately protected, within the limits set forth in the paper. Cascading also makes possible a simple means of selecting air circuit breakers to provide economical yet adequate protection for relatively small installations, where a complete short-circuit study might be difficult to justify and where a poor selection of protective devices would result in either an unnecessarily expensive installation or a serious hazard — generally the latter. An application table for such installations, based upon the principle of cascade operation is included.