Switchgear Assemblies Research Articles

Magnetic Field Density Analysis in Switchgears

For many years the evaluation of the electromagnetic field (EMF) generated by transformer substations (TS) and switchgear assemblies has been an extremely cumbersome and expensive process. Manufacturers and users of TS and switchgear lacked a broadly-accepted assessment procedure specified in an international reference standard. The publication of the new Technical Report IEC/TR 62271-208 solves this situation since it describes a technique for the evaluation of the EMF generated by switchgear assemblies and TS and opens the possibility of employing simulation tools for this purpose. In this paper, preliminary stage of process for validation of simulation tests in order to substitute laboratory tests according to IEC/TR 62271-208, is described. With this purpose, magnetic field emission analysis is carried out using finite elements (FE) method, for a set of 5 identical switchgears (manufactured by Ormazabal), in series connection. Results obtained through simulation are compared to those measured in laboratory tests. Evaluation results are also compared with applicable limits (100 µT and 500 µT at 50 Hz, according to most human exposure regulations: ICNIRP Guidelines, EU Council Recommendation, Spanish Royal Decree 1066/2001, etc).

Deklaracija o usaglašenosti sistema pobude sinhronih mašina

The paper presents a comprehensive complex model for the Declaration of Conformity of the Excitation System. The necessary projects for conformity assessment, standardization, accreditation and metrology are given. Some testing and compliance modules are listed. A part of the test according to the CB scheme of Low-voltage switchgear and controlgear assemblies for the excitation system Tesla ES 7000A is presented, which is according to valid standards, and for nominal currents up to 7000 A. A part of the test according to the CB scheme of electromagnetic compatibility for the Tesla ES excitation regulator is presented. The Declaration of Conformity of the Tesla ES 1600 excitation system is presented.

Engineering and design of a novel high-current source for testing low-voltage electrical equipment

This article presents the specification and design of a low-voltage high-current source with a capacity of up to 65 kA and 1 kV for testing electrical equipment such as low-voltage power circuit breaker switchgear, metal-enclosed switchgear, transformers, and cables, among others. Tests that can be performed with the proposed source include the short-circuit withstand on the low-voltage side of transformers, verification in temperature rise limits on electrical power connectors and transformers, and other compliance tests on power circuit breaker switchgear and controlgear assemblies. The design results from the comparison of general topologies of high-current sources according to the literature and test requirements established in current IEEE and IEC standards. In addition, the low-voltage high-current source emerged as a need for the Colombian electricity sector and will help comply with the test guidelines for switchgear and other low-voltage equipment, according to the national standard, also contributing to reducing costs of conducting tests abroad. The specification of the source resulted in the definition of three operating ranges for different types of tests, equipment, voltage, and current levels. Moreover, the general scheme of the low-voltage high-current source is provided with a description of the major components, namely, the novel medium- and low-voltage power modules based on the parallel and series arrangements of toroidal transformers to obtain levels of current and voltage of up to 65 kA and 1 kV, and the switching and protection, control, and measurement systems. Finally, a discussion of the results is presented, and the conclusions are highlighted. © 2017 Elsevier Inc. All rights reserved.

An innovative method to conduct temperature rise test on medium voltage switchgear assembly based on IEC standards in a power grid

Modern civilization is characterised by a high need for electrical energy. The importance of electricity in daily life has grown to the point that it is desirable to safeguard the power system from damage during fault situations and to ensure maximum supply continuity, which necessitates the use of switchgear. Testing of any electrical equipment indicates the extent to which the equipment is able to comply with a customer's requirements. In this paper temperature rise test on a medium voltage switchgear assembly is considered. In this research, sub-clause 6.5.2 of IEC standard 62271-1 is followed to conduct temperature rise test on a medium voltage switchgear assembly. The test is conducted on two modes, first following the existing method of testing and second by an innovative method of testing. The temperature rise test is conducted on a 12 kV, 50 kA, 3150 A single busbar switchgear assembly and the readings are measured, analysed and compared between the two methods. It is concluded that the temperature rise recorded following the innovative method is more accurate compared to the existing method, as an increase in the recorded temperature rise is seen in all the thermocouple locations as the heat dissipation to the ambient is reduced.

Vision-Based Robotic Solution for Wire Insertion With an Assigned Label Orientation

This paper tackles the problem of wire insertion in switchgear assembly according to the current regulations. In particular, the wire connections require that the wire label has to be oriented facing up in order to simplify and speed up testing and maintenance of the switchgear. The proposed approach exploits the a priori knowledge of the scenario with a calibrated RGB camera and a robotic arm to estimate both wire end pose and label position. The procedure combines several techniques (gradient base, trained classifier and stereo vision) to elaborate standard images in order to extract some wire features related to its shape and label. Specific frames are fixed according to estimated features and then used to correctly complete the task by using a robotic system. Experiments are reported to verify the effectiveness of the proposed approach.

IEC 61439: Alternate Design Verification Methods

Design verification for low-voltage power switchgear and control gear assemblies is intended to verify compliance of the design of an assembly or assembly system with the requirements of IEC61439 series of standards. There are 3 methods of verification. 1. Verification testing 2. Verification comparison with a tested reference design 3. Verification assessment by calculations and design rules including use of appropriate safety margins. The normally preferred verification method is verification by testing. However, verification by assessment and verification by comparison are also alternate verification methods provided by IEC 61439, which are still unexplored. This is in spite of the fact that IEC 61439 states: “ all the permitted means of design verification which includes comparison and assessment are equivalent in terms of performance achieved.” Here, we shall elaborate on the verification assessment and verification comparison methods for Low voltage switchgear and control gear assemblies.

Overview of development, design, testing and application of compact gas-insulated DC systems up to ± 550 kV

The development of high-voltage direct current gas-insulated switchgear assemblies (DC GIS) of rated voltages up to ±550 kV has been completed. DC GIS provide a compact technical solution with a high functional density, optimized for projects with limited space as in offshore HVDC converter platforms, onshore HVDC converter stations and transition stations between different transmission media. Up to now, no standards for testing of gas-insulated DC systems are available, although pre-standardization work is in progress within CIGRE. Some tests can be performed as required in AC GIS standards. Special aspects of DC voltage stress, like the electric field distribution of insulators influenced by the accumulation of electrical charge carriers and the operation-related inhomogeneous temperature distribution, must be considered by additional electric and thermoelectric tests. For DC GIS, the experience of long-term performance is limited today. Although ageing is expected to be of lower importance, tests are recommended. This contribution summarizes the physical and technical background to design and develop compact DC switchgear assemblies using gas-insulated technology. It explains the developed modules of the substation and gives an overview of the performed tests. Furthermore, it provides an insight in the on-going standardization activities and describes applications in converter and transition stations, showing its space-saving characteristics.

Tactile-Based Manipulation of Wires For Switchgear Assembly

This paper presents a mechatronic approach to the robotic manipulation of electrical wires for switchgear assembly. One of the challenges is the implementation of the wire insertion task, i.e., a wire, grasped by a robot, has to be inserted into the hole of a switchgear component to be then tightened. To this aim, a tactile sensor, installed on the robot gripper, has been optimized and a suitable algorithm has been developed for the wire shape estimation. The same tactile sensor is used to automatically evaluate if the insertion task and the following tightening have been correctly completed. The proposed approach allows to reconstruct the wire end point with a precision sufficient to allow the robot correctly execute the insertion phase with a high success rate. Experimental results validate the effectiveness of the proposed approach.

Electrical Power Quality and the Challenges Faced by Power Assemblies Applications in Petrochemical Industry

The use of power switchgear and controlgear assemblies in typical electrical power distribution systems of petrochemical industries, both in medium voltage and low voltage levels, has faced different challenges related to their specification and operation in order to deliver solutions that ensure the quality of electricity to be distributed. Many of these problems are related to the equipment used for both switching and protection. Components such as circuit breakers, protective relays, current transformers, and voltage transformers require careful analysis of the electrical system in question. The philosophies adopted for electrical protection, type of neutral grounding, and topographic conditions (arrangement) of the circuits can create conditions, which are unacceptable from the point of view of electrical power quality. Currently, in many of the analyses related to power quality in electrical installations, basic care in the definition and use of the internal components of the power assemblies is often not considered. This paper discusses actual case studies of different power assemblies installations in the industry, aiming in this way to introduce basic guidelines that can help in the specification and installation of new equipment or modernization of existing equipment for industrial facilities.

Verification of Low-Voltage Assemblies

The generation, transmission and distribution of electrical energy provide one of the most challenging environments in which to undertake an engineering career. Every project demands safety, performance and an acute commercial awareness. The design and provision of low-voltage switchgear and controlgear assemblies are no exception, requiring a detailed understanding of industrial power systems, switching and protective devices and electro-technical knowledge required to provide bespoke designs. The role of the electrical engineer whose remit is to design and manage the manufacture and supply of low-voltage assemblies, requires the culmination of academic qualification and years of experience. Underlining the engineering ability to fulfil these requirements is the knowledge and application of appropriate standards and legislation. The last five decades have seen a marked progression in the development and publication of standards, not least those in the electrical industry and a shift from the UK-centric approach, towards a more collaborative model, channelling input through national standards bodies such as BSI, onto the platform of the IEC (International Electro-technical Committee). This approach has now brought about the latest series of low-voltage assembly standards IEC EN 61439 which now requires a comprehensive approach to demonstrating compliance through a concept of rigorous verification.

Design of Current Adjusting Device

The Temperature Rise Test of Low Voltage Switchgear Assembly has rather high requirements for the test equipment; however, the present test equipment commonly has the problem of complicated test circuits, current regulation difficulty, high power consumption etc [. Therefore, in order to raise the present test level, we have devised new test methods and designed a new type of current adjusting device for the Temperature Rise Test. This new type of device has the advantages of easy operation, compact structure, flexible motion, low power consumption, low cost, high precision etc. Practical application has proved that it can meet the technical requirements for the Temperature Rise Test of Low Voltage Switchgear Assembly.

Operational maintenance data for power generation distribution and HVAC components

This paper describes the culmination of a 24000-man-hour effort to collect operational and maintenance data on 239 power generation, power distribution and heating, ventilation and air conditioning items, including gas turbine generators, diesel engine generators, switchgear assemblies, cables, boilers, piping, valves and chillers. This program was designed to determine the effects of "new technology" equipment, i.e., equipment installed after 1971, on availability. The central hypothesis was that this new equipment would exhibit a significant increase in availability, with corresponding decreases in required maintenance and the occurrence of failures. Information was obtained on a variety of commercial and industrial facility types (including office buildings, hospitals, water treatment facilities, prisons, utilities, manufacturing facilities, schools, universities, and bank computer centers), with varying degrees of maintenance quality. Data collection guidelines and goals were established to ensure that sufficient operational and maintenance data were collected for statistically valid analysis.

Integral equation approach for the analysis of three-dimensional transient electromagnetic heating effects

An integral approach for the analysis of three-dimensional transient electromagnetic heating effects is presented. The conductor bodies are decomposed in elementary parallelepipeds, and the centers of nearby parallelepipeds are connected in order to obtain a three-dimensional grid. The electrical and thermal equilibrium equations applied to this grid allow the evaluation of the current density and the temperature distribution inside the conductors of the system. The characteristics of the approach are shown through simulations of the tests provided in the experimental verifications of switchgear and control gear assemblies. >

Circuit Breaker Shock Testing - Individual Component Tests and Apparatus Mounted Tests

The integrity of circuit breakers in a shock environment is essential to the survivability of naval combatant ships. A momentary disruption of power due to the opening of circuit breakers can disable essential combat systems equipment for a substantial period of time relative to the required response time of these systems. Even with the ongoing effort to provide shock hardened circuit breakers, the record indicates that shock integrity has been a continuing area of concern during ship shock trials. An historical review is provided of the efforts which have been undertaken to improve the shock resistance characteristics of circuit breakers and of the circuit breaker mounting structures (i.e., in switchboards or panelboards). Circuit breakers have exhibited varying shock resistance characteristics when tested individually versus when tested as an integral member of a switchboard or panelboard, therefore, a comparison is provided of the shock testing specification requirements of circuit breakers tested as components and of the assemblies into which they are commonly mounted. The differences are analyzed to postulate possible causes for the inconsistency of shock qualified circuit breakers when shock tested in their operating environment. An analysis is provided of the similarities and differences of shock impacts on circuit breakers when tested as components and when tested in a switchgear or panelboard assembly. Two series of tests were conducted, one involving circuit breakers in a panelboard and the other involving circuit breakers in a switchboard. The analysis compares the acceleration-time histories, velocity, displacements, and the shock spectrum derived therefrom. Of particular interest is the mounting structure of circuit breakers when shock tested as components and the interaction of the switchboard structure with the circuit breakers under shock impacts. Recommendations are provided for improvements in specifications, for improvements in the design of the assemblies which house the circuit breakers, for improvements in circuit breakers and for more stringent requirements regarding first article testing of assemblies.

Engineering Test Codes and Standards for Motors, Controllers, Switchgear, and Transformers

There are many standards, which apply to electric equipment, such as ANSI, IEEE, NEMA, UL, and IEC. These standards cover factors such as design, installation, performance, and testing of both components and assemblies of components. To consider all of these factors would be a major undertaking. Only the performance and conformance testing of assemblies such as induction and synchronous motors in integral horsepower ratings, controllers for 600-V and 5000-V classes, low-voltage and medium-voltage switchgear assemblies, and transformers for load centers and substations are covered. The tests which are performed, whether the tests are routine, design, or by request only, and the standards which specify the requirements and test codes are shown.

Fault Voltage Drop and Impedance at Short-Circuit Currents in Low-Voltage Circuits

In the paper are presented new data on (1) arc-voltage drop and current-limiting effects for arc faults in bar-conductor structures, (2) current-limiting effect of insulated-cable arc faults, (3) cable impedance in an iron conduit, and (4) impedance of low-voltage switchgear circuit assemblies, derived from tests at short-circuit currents in circuits with open-circuit line-to-line voltages of 208-600 volts at 60 cycles. The currents ranged from less than 10,000 amperes to values as high as 100,000 amperes rms in some cases. The new data dispel several illusions with respect to accidental faults in low-voltage bus structures and other low-voltage gear. Contrary to inferences frequently drawn from previously published data, the paper shows that (a). Faults in the typical low-voltage bus structures tested are not self-clearing. (b). Fault arcs do not show the drastic current-limiting effect which they are frequently assumed to exert upon short-circuit currents. Instances are shown where actual fault currents reach 100 per cent of the rms symmetrical values calculated for bolted faults. This study shows a self-clearing tendency for representative types of accidental faults in cable, but it was found that a large current-limiting action prior to current interruption cannot be depended on. The new data, supplementing existing impedance data, definitely indicate the possibility of reasonably accurate calculation of short-circuit currents in low-voltage circuits.

Fault voltage drop and impedance at short-circuit currents in low-voltage circuits

In the paper are presented new data on (1) arc-voltage drop and current-limiting effects for arc faults in bar-conductor structures, (2) current-limiting effect of insulated-cable arc faults, (3) cable impedance in an iron conduit, and (4) impedance of low-voltage switchgear circuit assemblies, derived from tests at short-circuit currents in circuits with open-circuit line-to-line voltages of 208-600 volts at 60 cycles. The currents ranged from less than 10,000 amperes to values as high as 100,000 amperes rms in some cases. The new data dispel several illusions with respect to accidental faults in low-voltage bus structures and other low-voltage gear. Contrary to inferences frequently drawn from previously published data, the paper shows that (a). Faults in the typical low-voltage bus structures tested are not self-clearing. (b). Fault arcs do not show the drastic current-limiting effect which they are frequently assumed to exert upon short-circuit currents. Instances are shown where actual fault currents reach 100 per cent of the rms symmetrical values calculated for bolted faults. This study shows a self-clearing tendency for representative types of accidental faults in cable, but it was found that a large current-limiting action prior to current interruption cannot be depended on. The new data, supplementing existing impedance data, definitely indicate the possibility of reasonably accurate calculation of short-circuit currents in low-voltage circuits.

A New Current-Limiting Fuse

Increasing concentration of power combined with the desire for more compact switchgear assemblies has created a demand for small, totally enclosed, high-interrupting-capacity fuses suitable for potential and operating transformer protection. The current-limiting fuse meets these requirements for it is inherently a high-interrupting-capacity fuse of low current rating and can be totally enclosed in a small space. The theory and construction of previous current-limiting fuses are briefly described. The theory and construction of a new current-limiting fuse is given. The new fuse is simple in theory and construction. Its fundamental elements can be separated, studied, and tested, making it possible to predict an unusual degree of reliability and freedom from voltage surges. Test results confirm the reliability, high interrupting capacity, and freedom from voltage surges of the new fuse.