AC Power Circuits Research Articles

Medium-Voltage Circuit Breakers and Contactors Are Not the Same: Neither are Their Protection Methods

Many standards and specifications related to medium-voltage (MV) motor and feeder circuits continue to center around the improper generic use of IEEE Device 52 as a circuit identifier for the switching device used within various points of power systems. IEEE Device 52 is defined as a device that is used to close and interrupt an ac power circuit under normal conditions or to interrupt this circuit under fault or emergency conditions. While many of the present standards include detailed protection and coordination recommendations that are centered only on the protective and control settings for circuit breakers (CBs), the protection schemes for CBs and fused contactor-controlled motors are documented in IEEE Standard 3004.8. This article clarifies some key differences between MV contactors and MV CB ratings. It also compares the appropriate protection variations and requirements between the two devices, highlighting the dangers to personnel and equipment if misapplied. Recommended protective device functions for motor protection for fused contactor-controlled or breaker-controlled motors are presented with companion drawings.

Pengukuran Radiasi Kalor pada Beberapa Bohlam yang Berbeda-beda Warnanya

This study aims to compare the rate of heat absorption in black, red, green, yellow, milky white, and blue electrical light related to temperature change with a predetermined time variation. This study uses an AC power circuit to light a bulb with varied colours and then measures the temperature associated with the heat involved in the light on. The calculation in this study uses the Black principle concept. The results showed that black and green light bulbs had the greatest temperature change followed by red, blue, yellow, and white bulbs. This is in accordance with the basic concept that dark colours tend to conduct heat better than bright colours.

Coordination of surge protective devices in low voltage AC power installations

The surges protection in low-voltage AC power circuits is commonly realized by Surge Protective Devices (SPDs). These devices divert a large amount of the surge energy to the ground and reduce the surge voltage to the level acceptable for protected device(s). Adequate protection performances are provided by applying multiple-stage protection assuming cascade deployment of SPDs starting from distribution board toward equipment in an installation. Therefore, SPDs coordination, (i.e. selection of SPDs parameters as well as determination of necessary distance between stages) becomes of great importance and the paper deals with this issue. The proper SPDs coordination is significant for both protected equipment and SPDs themselves (their survival during surges). The paper provides an analysis of the SPDs coordination for case of two-stage protection system. The influence of different lengths of cables between protection stages, as well as influence of type and parameters of load on SPDs protection characteristics have been analyzed and discussed with the purpose of determination of requirements for proper surge protection and coordination of applied SPDs.

Smart Aquarium as Physics Learning Media for Renewable Energy

Smart aquarium has been developed as a learning media to visualize Micro Hydro Power Generator (MHPG). Its used aquarium water circulation system and Wind Power Generation (WPG) which generated through a wheel as a source. Its also used to teach about energy changes, circular motion and wheel connection, electromagnetic impact, and AC power circuit. The output power and system efficiency was adjusted through the adjustment of water level and wind speed. Specific targets in this research are: to achieved: (i) develop green aquarium technology that’s suitable to used as a medium of physics learning, (ii) improving quality of process and learning result at a senior high school student. Research method used development research by Borg and Gall, which includes preliminary studies, design, product development, expert validation, and product feasibility test, and vinalisation. The validation test by the expert states that props feasible to use. Limited trials conducted prove that this tool can improve students science process skills.

Effects of Different Combination Wave Generator Design on Surge Protective Devices Characteristics in Cascade Protection Systems

Cascade application of surge protective devices (SPDs) in low-voltage ac power circuits is intended to ensure proper equipment protection against surges as well as to provide surge energy distribution between SPDs. In order to evaluate equipment response and SPDs performance, concept of representative surges, which can be used for surge testing purposes, is introduced by international standards. Combination wave surge is defined both by IEEE C62.41.2 standard and IEC 61000-4-5 standard as one of the representative surges. However, these standards specify different tolerances regarding short-circuit current waveform's undershoot delivered by combination wave generator (CWG). The aim of this paper is to investigate the influences of different CWGs regarding short-circuit current undershoot in cascade two-stage protection system. It will be shown that differences that appear during surge testing with application of different CWGs can lead to inappropriate selection of SPDs regarding energy absorption capability and/or protection level.

The Misuse of IEEE Device 52- Medium Voltage Contactors and Breakers Are Not the Same!

Many standards and specifications, related to medium voltage (MV) motor and feeder circuits, continue to center around the generic use of the IEEE Device 52 as a circuit identifier for the switching device used within those power systems. IEEE Device 52 is defined as a device that is used to close and interrupt an ac power circuit under normal conditions or to interrupt this circuit under fault or emergency conditions. Many of the current standards include detailed protection and coordination recommendations that are centered on circuit breaker protective settings. Some of these recommended protective settings can be detrimental when medium voltage vacuum contactors are used instead of ac circuit breakers to interrupt the circuit under fault conditions such as in motor and feeder applications. This paper will outline MV contactor and breaker rating differences, compare the appropriate protection variations and requirements between the two, and highlight the dangers to personnel and equipment when assuming that a medium voltage vacuum contactor can provide the same performance and require the same protective settings as a medium voltage circuit breaker.

Estimation of transient surge energy transferred with associated time delays for individual components of surge protector circuits

Modern semiconductor technology is vulnerable to transient surges such as lightning. Transient voltage suppressor systems (TVSSs), which are installed to protect modern electronics, use non-linear components such as varistors and transient voltage suppressor diodes in their design. In the case of low-voltage (1000 V and less) AC power circuits, there is no clear approach to estimate the energy absorption and associated time delays in individual components in relation to the propagated transient surge. Numerical simulation techniques can be used to analyse the phenomenon of surge propagation within a TVSS and estimate the energy transferred to each component with associated time delays. Suitable mathematical models must be used for the non-linear components. This study presents the development of reasonably accurate models for the non-linear circuit elements and formulation of state equations for the TVSS, together with simulation results; results are experimentally validated using a lightning surge simulator. The method of analysing surge propagation presented here could be extended to analyse the phenomenon of surge propagation within power conversion stages which buffer the complex electronic circuits and the power source. The results discussed here indicate that the theoretical energy calculations are within 10% of the experimental results for the individual circuit elements.

Characteristics of Overvoltage Protection with Cascade Application of Surge Protective Devices in Low-Voltage AC Power Circuits

Surge Protective Devices (SPDs) are widely used for protection of the equipment in low-voltage AC power circuits against wide variety of surges. Cascade application of SPDs starting at ...

Estimation of general energy-savings in three-phase ac power circuits by balancing phase currents using power active filter

Analyzing the ways of circuit power loss decreasing by balancing phase currents, the authors obtained analytical relations permitting to estimate power consumption decrease in a three-wire and four-wire ac circuit using a power active filter

Frequency of flashovers of clearances in low‐voltage ac power circuits due to overvoltage waves

AbstractThe frequency distribution of the crest values of overvoltage waves in low voltage AC power circuits can be approximated by an exponential function. The flashover probability P of a clearance with an impulse withstand voltage Ǔst in an electrical equipment is given by P= exp (‐ α Ǔst). The annual number of flashovers of a single clearance in an unprotected house wiring system supplied by an unprotected overhead network depends upon the impulse withstand voltage, the latitude of the network, the annual number of thunderstorm days, the effective length and the height above ground of the overhead line. However, this does not mean, that every flashover triggers a dangerous power frequency follow current.

A generalization of the concept of impedance and a novel Walsh domain immittance

This paper deals with generalized solution methods for AC power circuits. The motivation is to explore more efficient numerical solutions of power distribution circuits subject to electronic loads. Two main points are presented: a generalization of Ohm's law; and the use of the Walsh domain (as opposed to the frequency or Fourier domain) for calculations. With regard to the latter, a Walsh domain matrix similar to the bus impedance matrix is proposed. The matrix may be used to identify potential system resonances. The proposed application area for these techniques is in electric power distribution. >

PWM and phase lead combined control of AC power circuit

PWM and phase lead combined control of AC power circuit

Bibliography on Surge Voltages in AC Power Circuits Rated 600 Volts and Less

Damage by transient overvoltages of equipment operating on low-voltage ac power circuits has received increasing attention. Before effective protection can be devised, it is necessary to understand the nature of the phenomenon. Relatively little information has been published. The Working Group on Surge Voltages in AC Power Circuits Rated 600 Volts and Less has compiled a bibliography on the subject. References are grouped in broad categories, and a short paragraph describing each paper follows the reference.

Curing Interference in Relay Systems

A review is made of methods for EMI suppression for relay coil transients and switch contact arcing. The mechanism of generation of coil transients and contact arcing is described briefly. A relay solenoid is controlled in actuation by a toggle switch S. In closing, the switch exhibits bounce characteristics which cause momentary deenergizing of the relay solenoid, with the subsequent momentary oscillatory transients and switch-bounce current breaking, reflected as switch contact arcing during bounce. When S is opened, the stored energy (L12/2) is returned to the circuit and is dissipated as power losses in the relay core and switch arcing. In addition, the collapsing magnetic field generates a transient, or counter EMF, voltage expressed as E = _L(di/dt) volts. As S opens, an arc appears due to breaking current which quenches as the switch opens further. The arc is restruck as the coil voltage transient increases due to the sudden current changes, and the process continues until the coil current reaches zero. It may be noted, when viewing the transient on an oscilloscope, that a series of sawtooth changes reflected from the switch arcing is observed, rather than the expected exponential rise. The general description of this generated EMI is that it is broadband in frequency and impulsive in nature. It can be coupled into the ac power circuits via the power supply, or radiated from the line, the solenoid, and switch.