Schneider’s “Cahier techniques” for Engineers
We thought the following may be of interest to you. Click on the links to view each “Cahier Technique”.
Each "Cahier Technique" provides an in-depth study of a precise subject in
the fields of electrical networks, protection devices, monitoring and control
and industrial automation systems.
Active harmonic conditioners and unity power factor rectifiers Electric loads are becoming increasingly non-linear in the industrial, tertiary and even household sectors. These loads absorb non-sinusoidal currents which, under the effect of circuit impedance, distort the purely sinusoidal voltage waveform. This is what is known as harmonic disturbance of power networks, currently a cause for concern as it gives rise to serious problems. This describes the active harmonic conditioners. This attractive, flexible and self-adaptive solution can be used in a wide variety of cases to complete or replace other solutions. ECT183.pdf - Size: 395.1Kb - Published: 14/06/2002
Automatic transferring of power supplies in HV and LV networks An examination of the difficulties of implementing such switching devices, together with the possible technical solutions. A presentation of the various switching types backed up by practical examples, and a table summarizes the main areas of application. ECT161.pdf - Size: 72.3Kb - Published: 11/06/2002
Behavior of the SF6 - MV circuit breakers Fluarc for switching motor starting currents Many years ago, oil circuit-breakers (OCB) and air magnetic circuit-breakers (AMB) were the main breaking techniques for MV applications. Since 1970 or 1975 (depending on the country) SF6 and vacuum breaking techniques appeared on the MV market, for the primary substations firstly. ECT143.pdf - Size: 86.5Kb - Published: 21/03/2002
Breaking by auto-expansion The term "auto-expansion" is used to cover a variety of techniques or breaking methods according to technical documents and circuit-breaker manufacturers. Firstly the main differences concealed by this term are defined, as regards both breaking principles and special features, and then the breaking by auto-expansion in SF6. ECT171.pdf - Size: 210.9Kb - Published: 14/06/2002
Calculation of short-circuit currents Reviews the calculation methods for short-circuit currents as laid down by standard IEC 60909. It is intended for radial low-voltage (LV) and high-voltage (HV) circuits. ECT158.pdf - Size: 654.6Kb - Published: 11/06/2002
Cohabitation of high and low currents the rapid development of digital systems using low current links (bus) has given rise to the critical problem formed by cohabitation of high and low currents. The real problem is how to reconcile electrical safety and electromagnetic compatibility. The following issues thus arise for which solutions must be found: how to treat the problem of exposed conductive parts, which earthing system should be chosen, which shields, mitigating planes, Faraday cages should be chosen and for what purpose, how to organize routing of high and low current circuits, and many others. ECT187.pdf - Size: 176.8Kb - Published: 14/05/2003
Control equipment for MV capacitor banks The location of the capacitors in an electrical network constitutes what is known as the "compensation mode" This compensation is technically ideal since it produces reactive energy at the point where it is consumed, and in quantities strictly adjusted according to the demand. However, this solution is costly and generally leads to overcompensation since it does not include combining possibilities for load increases. ECT142.pdf - Size: 210.3Kb - Published: 13/06/2002
Control/monitoring and protection of HV motors Unit power of rotating machines frequently exceeds 100 kW in industry and large tertiary. In such cases and/or if the length of the supply line is particularly long, use of high voltage motors is advantageous. The starting systems and the various protection devices which may be used are compared in order to simplify technical choices. ECT165.pdf - Size: 141.9Kb - Published: 13/06/2002
Current transformers for HV protection Current transformers or CTs take up a lot of space in HV cubicles. Thorough knowledge of how they work makes it possible to reduce their dimensions and thus their cost, use standard CTs in a larger number of configurations. After a brief theoretical review of CT operation and current protection devices, the behavior of the CT-protection relay combination is studied in two particularly important cases in HV. ECT164.pdf - Size: 256.0Kb - Published: 13/06/2002
Current Transformers: How to Specify Them The task, consisting of identifying and rating the current transformers and associating them with the protection and/or metering units, has always given rise to problems, both for electrical engineers (oversizing the characteristics)and for the manufacturer (random feasibility, excessive sizing, high costs). ECT194.pdf - Size: 374.9Kb - Published: 14/05/2003
Current Transformers: Specification Errors and Solutions Highlights the errors most often encountered when defining current transformers, an essential and little known link between the electrical network and the protection relays. Explains how to find a way out of difficult situations: CTs that cannot be manufactured, delays, additional costs, malfunctions, etc. ECT195.PDF - Size: 171.0Kb - Published: 14/05/2003
Dependability and LV Switchboards Dependability of commercial and industrial low voltage electrical installations. It focuses on which switchboard functions guard against failure of the LV distribution system, how should components be used, and in what power system environment (number of sources and loads, type of system earthing)? ECT156.pdf - Size: 317.9Kb - Published: 11/06/2002
Dependability of MV and HV protection devices Details the various factors contributing to dependability of protection devices in Medium and High Voltage networks, together with the methods which can be implemented to meet dependability objectives. It places special emphasis on, taking dependability into consideration at the design stage, the quality approach (software, qualification, manufacture) with techniques adapted to the constraints encountered in Medium and High Voltage; and analysis of experience feedback. ECT175.pdf - Size: 259.5Kb - Published: 14/06/2002
Development of LV circuit breakers to standard IEC 947-2 Presents the advantages of IEC 60947-2 standard over the former IEC 157-1, and describes the numerous tests to be satisfied by these breaking devices. These tests are highly representative of the constraints actually encountered in electrical installations. ECT150.pdf - Size: 446.7Kb - Published: 21/03/2002
Directional protection equipment This aims to give the reader a better understanding of so called "directional&" protection: a very useful technology for HV networks and machines. Advances in digital technology and the integration of logical selectivity, has enabled it to make great progress in terms of reliability, simplicity of incorporation and even costs. Its use allows to implement network configuration and selectivity system improving the dependability of power supplies. After reviewing their operating principle, the author goes on to present their many applications and gives some useful information on their incorporation. ECT181.pdf - Size: 161.9Kb - Published: 14/06/2002
Dynamic stability of industrial electrical networks Given that electrical energy is very difficult to store, a permanent balance between production and consumption is vital. Generators, loads and the electrical networks which connect them have mechanical and/or electrical inertias which complicate the maintaining of a balance guaranteeing relatively constant frequency and voltage. The purpose of this document is to understand why instability can appear and to define the main causes and effects of such instability. It explains the precautions to be taken and, using a concrete example, describes how a typical study is conducted. ECT185.pdf - Size: 125.2Kb - Published: 14/06/2002
Earthing - IT earthing system (unearthed neutral) in LV This describes the advantages and areas of application of the IT earthing system. After a brief introduction of the electrical hazard and the various earthing systems, the first fault situations, followed by the double fault specific to the IT system, are studied, and the advantages and disadvantages of this particular earthing system are developed. This "Cahier Technique" also offers solutions for the surge limiter with the various types of possible overvoltages. ECT178.pdf - Size: 504.6Kb - Published: 14/06/2002
Earthing systems in LV This reviews the hazards that insulation faults represent for safety of persons and property. It emphasizes the influence of earthing systems and the availability of electrical power. It presents the three earthing systems defined in standard IEC 364 and used to varying degrees in all countries. Each earthing system is looked at in terms of dependability (safety, maintainability and availability). ECT172.pdf - Size: 321.1Kb - Published: 14/06/2002
Earthing systems worldwide and evolutions Following an historical review of the origins of Earthing Systems, this provides information on the practices in some countries concerning medium voltage, HV/LV substations, in particular in LV public, industrial and tertiary distribution. Electrical installations are evolving; electronics are everywhere, thus leading us to look afresh at earthing systems used in LV and indeed even to predict an evolution which should bring the TN-S and TT systems closer together. ECT173.pdf - Size: 241.1Kb - Published: 14/06/2002
Earthquakes and electrical equipment In all countries there is either a zone of significant seismic activity or installations which require high security in order to operate (e.g. nuclear power stations, which generally have low seismic activity). In both cases the electrical and control and monitoring equipment must assure their safety functions correctly. This technical paper aims to facilitate dialogue between operators and specialists. After briefly summarizing the earthquake phenomena and the way in which they are specified, the author presents the theoretic approach required for seismic withstand capabilities to be taken into account at the design stage. ECT180.pdf - Size: 223.4Kb - Published: 14/06/2002
Electrical Disturbances in LV To improve the quality of the "electricity product” and avoid malfunctioning and in some cases destruction of the components of the electrical network and/or sensitive loads, it is essential to understand the origin of the disturbances and evaluate their risks. This is introduction to the vast field of electromagnetic compatibility and immunity from 50 Hz through to radioelectric frequencies. ECT141.PDF - Size: 348.8Kb - Published: 21/03/2002
Electrical installation dependability studies Loss of power is always annoying, but it can be particularly penalizing for information systems (computing -monitoring and control); they can even have disastrous consequences for certain processes and in certain cases endanger people's lives. Dependability studies enable electrical availability requirements to be incorporated in the choice of electrical network to be installed. They also enable two different installation configurations to be compared ... the most expensive one is not always better. This document shows how dependability studies are performed: methodology and tools. Two examples of studies are given: that of an electrical network in a factory and that of the monitoring and control system of a high voltage substation. These studies are becoming increasingly easy to perform thanks to computing tools. ECT184.pdf - Size: 120.0Kb - Published: 14/06/2002
Electrodynamic forces on busbars in LV systems Behavior of their components in the light of their environment and of possible operating stresses. Calculations lay down to allow for these forces and in particular to determine LV busbar requirements. ECT162.pdf - Size: 136.7Kb - Published: 11/06/2002
EMC: electromagnetic compatibility For all electrotechnical equipment, EMC must be considered right from the initial design phase and the various principles and rules carried on through to manufacture and installation. This means that all those involved, from the engineers and architects that design a building to the technicians that wire the electrical cabinets, including the specialists that design the various building networks and the crews that install them, must be concerned with EMC - a discipline aimed at achieving the "peaceful" coexistence of equipment sensitive to electromagnetic disturbances alongside equipment emitting such disturbances. ECT149.pdf - Size: 470.8Kb - Published: 21/03/2002
Enclosures and degrees of protection The protection of persons against direct contact is required by certain regulations, and specified by standards, such as IEC 60364. Therefore, to explain the degrees of protection that enclosures can provide, and how standards codify them, constitutes essential information for all, prescribes, installers, operators and inspecting organizations. ECT166.pdf - Size: 72.2Kb - Published: 13/06/2002
Energy-based discrimination for low-voltage protective devices This presents the new energy-based discrimination technique that ensures tripping discrimination between protective devices during a short circuit. Both simpler and more effective than standard discrimination techniques, it has been implemented on the Compact NS range of circuit-breakers used in low-voltage power distribution networks. ECT167.pdf - Size: 156.4Kb - Published: 13/06/2002
Ferroresonance Ferroresonance is a non-linear resonance phenomenon that can affect power networks. The abnormal rates of harmonics and transient or steady state overvoltages and overcurrents that it causes are often dangerous for electrical equipment. Some unexplained breakdowns can be ascribed to this rare, non-linear phenomenon. ECT190.pdf - Size: 235.1Kb - Published: 14/05/2003
Field Bus: a User Approach Deals with the "field bus" concept in the manufacturing industry from a user standpoint. Over and beyond cost and performance criteria, it attracts the attention of specifiers and contractors to the importance of the needs concerning interoperability and durability. ECT197.PDF - Size: 360.4Kb - Published: 14/05/2003
From current transformers to hybrid sensors, in HV Technical and technological changes in the protection and control/monitoring equipment used in electrical power distribution networks must be mirrored by parallel changes in their information sources, i.e. in current and voltage sensors. Following a few reminders on information needs and on current transformers, this document then presents the new hybrid sensors, with particular emphasis on those based on a Rogowski coil. ECT170.pdf - Size: 249.5Kb - Published: 14/06/2002
Fuzzy Logic Used alongside other advanced control techniques, it is making a discrete but appreciated appearance in industrial control automation systems. Fuzzy logic does not necessarily replace conventional control systems. Rather it completes such systems. Its advantages stem from its ability to: formalize and simulate the expertise of an operator or designer in process control and tuning, provide a simple answer for processes which are difficult to model, continually take into account cases or exceptions of different kinds, and progressively incorporate them into the expertise, take into account several variables and perform "weighted merging" of influencing into variables. ECT191.pdf - Size: 473.8Kb - Published: 14/05/2003
Harmonic Disturbances in Networks and their Treatment Electricity is generally distributed as three voltage waves forming a 3-phase sinusoidal system. One of the characteristics of such a system is its waveform, which must always remain as close as possible to that of a pure sine wave. If distorted beyond certain limits, as is often the case on networks comprising sources of harmonic currents and voltages such as arc furnaces, static power converters, lighting systems, etc., the waveform must be corrected. ECT152.pdf - Size: 298.0Kb - Published: 21/03/2002
Harmonics upstream of rectifiers in UPS Problems occurring downstream of rectifiers which supply non-linear loads. Also definitions and mathematical formulae relating to harmonics. ECT160.pdf - Size: 106.1Kb - Published: 11/06/2002
High availability electrical power distribution Explains to electrical installation designers how to design electrical power distribution systems that fulfill the objective of continuous voltage supply across the feeder terminals. In other words: how to master power availability so as to achieve the operating DEPENDABILITY objective. ECT148.pdf –
Size: 87.3Kb - Published: 21/03/2002
HV industrial network design Electrical networks supply the energy required to run the production facilities. The provision of a continuous power supply to loads is strived for from the start of the network design, in particular during preliminary choices in the single-line diagram. Reductions in electrical installation and operating costs, together with reliable failure-free operation, are vital conditions for profitability. ECT169.pdf - Size: 170.3Kb - Published: 14/06/2002
Integration of Local Power Generation in Industrial Sites and Commercial Buildings Engine driven alternating current generator sets are often used in remote industrial sites as a prime source of electrical energy. They are also extensively used in both industry and commercial buildings as a source of back-up power. Discusses most of the subjects which have to be handled when implementing engine driven alternating current generator sets having rated powers up to 20 MW. ECT196.PDF - Size: 580.2Kb - Published: 14/05/2003
Intelligent LV switchboards In all buildings, regardless of the activity carried out inside, the distribution of electrical power must today satisfy ever-increasing needs for dependability and efficiency. Starting with an analysis of needs, this document takes a close look at how LV power distribution can be managed. Particular emphasis is placed on decentralizing and distributing intelligence in and around the LV switchboard. Several examples of such installations are also provided. ECT186.pdf - Size: 180.2Kb - Published: 14/06/2002
Introduction to dependability design Equipment failures, unavailability of a power supply, stoppage of automated equipment and accidents are quickly becoming unacceptable events, be it to the ordinary citizen or industrial manufacturers. Dependability and its components: reliability, maintainability, availability and safety, have become a science that no designer can afford to ignore. ECT144.pdf - Size: 170.9Kb - Published: 21/03/2002
Inverters and harmonics (case studies of non-linear loads) Modern inverters are excellent generators of sinusoidal voltage even when they supply non-linear loads. This is considered quite normal as UPS are designed and very often utilized to supply computer/ microprocessor systems which draw non-sinusoidal currents. ECT159.pdf - Size: 108.4Kb - Published: 11/06/2002
Lightning and HV electrical installations This presents an overview of lightning phenomena and their effects on electrical installations, present currently available means to protect installations and limit detrimental effects, discuss problems concerning continuity of service, indicate the main steps in lightning studies on the basis of an example involving an EHV installation developed by the Network Research Department. ECT168.pdf - Size: 161.6Kb - Published: 13/06/2002
Low Voltage circuit-breaker breaking techniques This aims to define the currents to break in LV installations, explain a phenomenon which occurs whenever a circuit is opened: the electric arc, theoretically analyze the breaking of various currents by the arc placed in the extinguishing condition and describe breaking devices. ECT154.pdf - Size: 624.8Kb - Published: 21/03/2002
LV breaking by current limitation A simple introduction to the principles of low voltage current limitation, a technique developed by Merlin Gerin. It simplifies understanding of the advantages gained by using limiting circuit-breakers in electrical installations, ending with a detailed bibliography for those wishing to satisfy their scientific curiosity. ECT163.pdf - Size: 207.4Kb - Published: 13/06/2002
LV circuit-breakers confronted with harmonic, transient and cyclic currents Development of loads, a result of the technological breakthroughs of the last decade, has led to an increased number of constraints in electrical power distribution. Protection devices have had to adapt accordingly, particularly with regard to three phenomena, high harmonic currents due to multiplication of non-linear loads using power electronics (rectifiers, switch mode power supplies,...), transient currents caused by energizing loads with a high inrush current such as capacitive loads, LV/LV transformers and cyclic currents resulting from a marked increase in load automatically in repetitive cycles (welding robots, wave train heating). ECT182.pdf - Size: 90.8Kb - Published: 14/06/2002
LV surges and surge arresters LV insulation co-ordination Low voltage insulation co-ordination consists of matching the surge levels that may appear on an electrical network (or installation) with the surge withstand of the industrial or domestic equipment that it supplies, bearing in mind the possibility of including surge limiting devices in the network structure. This discipline contributes to increased safety of equipment and increased availability of electrical power. ECT179.pdf - Size: 304.1Kb - Published: 14/06/2002
MV Breaking Techniques Details the advantages, disadvantages and application fields of past and present Medium Voltage breaking techniques. Having defined the currents to be broken and discussed breaking on a theoretical level, the author goes on to present breaking in air, oil, and in SF 6, finishing with two comparative tables. ECT193.PDF - Size: 527.2Kb - Published: 14/05/2003
MV public distribution networks throughout the world Describes the various types of distribution networks and the distributor's role, plus details on the topologies of MV networks, substations, and protection and telecontrol devices. ECT155.pdf - Size: 516.6Kb - Published: 11/06/2002
Neutral Earthing in an Industrial HV Network HV electrical networks can be earthed in different ways. This document analyzes the constraints imposed by the different parameters of the installation (overvoltages, network, and receivers) and calculates the fault currents. Different protection modes are described along with the settings and adjustments suggested according to the requirements. ECT062.PDF - Size: 73.5Kb - Published: 21/03/2002
Overvoltages and insulation coordination in MV and HV Insulation coordination is a discipline aiming at achieving the best possible technical-economic compromise for protection of persons and equipment against overvoltages, whether caused by the network or lightning, occurring on electrical installations. It helps ensure a high degree of availability of electrical power. Its value is doubled by the fact that it concerns high voltage networks. ECT151.pdf - Size: 192.5Kb - Published: 21/03/2002
Power Quality Describes the main phenomena causing degradation in Power Quality (PQ), their origins, the consequences for equipment and the main solutions. It offers a methodology for measuring the PQ in accordance with differing aims. Illustrated with practical examples for the implementation of solutions, it shows that only by observing best practice and by applying strict methodology (diagnostics, research, solutions, implementation, and preventive maintenance) can users obtain the right quality of power supply for their requirements. ECT199.pdf - Size: 891.1Kb - Published: 14/05/2003
Protection of MV/LV substation transformers Discusses the stresses to which the transformers are subjected during operation and the consequences of these stresses and goes on to present the various protection devices that can be used. It is necessarily simple, due to the large number of criteria and solutions that exist. Electrical engineers should however find this document provides the main information needed to make the right choices. ECT192.pdf - Size: 205.8Kb - Published: 14/05/2003
Residual current devices in LV The earth leakage circuit-breaker is generally recognized as the best and most reliable of the protective devices which have been developed to offer protection against indirect contact in the low voltage field. ECT114.pdf - Size: 268.6Kb - Published: 21/03/2002
SF6 properties, and use in MV and HV switchgear The general properties of SF 6 gas and its SF 6 by-products are presented. A brief history of the use of SF 6 in switchgear is given. The effects of SF 6 on the environment are discussed. Guidance is given for working with SF 6 gas and SF 6 filled equipment under normal and abnormal conditions of service. ECT188.pdf - Size: 173.5Kb - Published: 14/05/2003
The singularities of the third harmonic In installations where the neutral is distributed, non-linear loads may cause significant overloads in this conductor due to the presence of the third harmonic. Both the phenomenon and its remedies are explained. ECT202.pdf - Size: 207.4Kb - Published: 14/05/2003
Thermal study of LV electric switchboards Aims at furthering the understanding and mastery of the thermal problems encountered in LV electric switchboards. After a brief review of standards and of thermal phenomena: conduction -radiation - convection, the author shows how LV cubicles can be modeled using modeling techniques normally reserved for other areas. Modeling naturally leads to software to aid design of electrical cubicles equipped with switchgear. The results are compared with real temperature measurements.
ECT145.pdf - Size: 321.2Kb - Published: 21/03/2002
Vacuum Switching A brief description of the physical phenomena that are associated with vacuum switching, and of their use. It also includes a presentation of the different technological options that are available to vacuum interrupter designers. ECT198.PDF - Size: 1203.1Kb - Published: 14/05/2003
