Residual Current Devices Research Articles

A Novel Fault Leakage Current Detection Method With Protection Deadzone Elimination

Residual current device is an important switch apparatus to ensure the safe and reliable operation of the power distribution system. This article proposes a novel fault leakage current detection method to eliminate the protection deadzone that is typically associated with the classical leakage current detection method. The proposed method takes the leakage current variation in addition to the instantaneous root-mean-square (rms) value of the leakage current as the indicator of leakage fault. Three mathematical models of leakage current variation calculation are illustrated in detail and a multilevel leakage fault protection strategy is proposed. Simulation and experimental results are presented to validate the effectiveness of the proposed leakage current detection method, and a comparative evaluation of the classical and the proposed leakage current detection methods is conducted to verify the superiority of the proposed method.

Study of RCD on Industrial Commercial and Residential Electrical Safety – A Hazard Awareness

Every human relies on electricity to power the operation and comfort of their businesses and homes. And they expect their electrical installations to be secure, to protect people from the risk of shock or electrocution, and to protect buildings against the risk of electrical fire. Although the municipal laws on electrical health and defensive equipment continue to improve, many risks still remain today. Hence the paper reflects on the real development in the electrical safety industry through innovative engineering technologies covering all sorts of industrial, business, residential safety. Thus, during the electrical faults, the paper studies the function and importance of highly sensitive residual current device (RCD) and its defensive techniques. RCD is a protective device that detect the electrical faults and switch off the electricity automatically.

The Propagation and Interaction of Supraharmonics from Electric Vehicle Chargers in a Low-Voltage Grid

The recent increase in large converter-based devices like electric vehicles and photovoltaics increases supraharmonic emissions in low-voltage grids, potentially affecting customer equipment and the grid. This paper aims to give an overview of the different factors influencing supraharmonic emissions from electric vehicles and studies the propagation of supraharmonic currents through a small, low-voltage grid. Measurements in an unique lab representing a possible future household gave valuable insight on the possible developments in primary and secondary supraharmonic emissions in a conventional or power-electronic-dominated system. Emission is, for some vehicles, influenced by the type of grid connection, whereas others show no difference in emission. The supraharmonic currents mainly stay within the local installation due to absorption of nearby devices. The level of voltage distortion is dependent on the connection impedance. During the measurements, another type of interaction between devices is observed in the form of “frequency beating” and intermodulation, in some cases resulting in the tripping of residual current devices. This interaction is further analyzed in order to better understand the possible impact it can have on the grid.

Risk Assessment of the Najmieh Hospital Electricity System using Energy Trace and Barrier Analysis Method

Introduction: Considering application of multiple electrical equipment, numerous occupational accidents occur in hospitals each year. Electrical accidents are severe and impose high costs on the individuals and organizations. The aim of this study was to assess the risk of electrical systems in one of the oldest hospitals under supervision of Baqiyatallah University using energy trace and barrier analysis method (ETBA).
 Methods and Materials: All wall plugs, switches, stationary and portable equipment, and stationary and portable electrical panel were evaluated in terms of earthing and appearance. This was done using a simple voltmeter and a 100-watt bulb. All equipment and electrical panel were examined for the presence of Residual Current Device. The ETBA worksheets were completed for each equipment and workstation. The existing barriers were identified and initial risk reduction numbers were calculated. Barriers and solutions were suggested for the equipment or workstation that was at higher risk. Controlled risk was calculated by considering new barriers.
 Results: The ETBA worksheets were completed for 71 devices and workstations. The initial and controlled risk was calculated. Surveys revealed that all sections of the main building and the departmental structures did not have a good status regarding the earth condition. Risk assessment of the equipment and stations by ETBA method indicated that 97% of the equipment were not at an acceptable level of risk, 52% were at the unacceptable risk level, 45% were at undesirable risk level, and only 3% were at the acceptable risk.
 Conclusion: The results of this study can be used to prioritize resource allocation to eliminate hospital defects and reduce the risk of accidents up to an acceptable level.

Testing Sensitivity of A-Type Residual Current Devices to Earth Fault Currents with Harmonics.

In many applications, modern current-using equipment utilizes power electronic converters to control the consumed power and to adjust the motor speed. Such equipment is used both in industrial and domestic installations. A characteristic feature of the converters is producing distorted earth fault currents, which contain a wide spectrum of harmonics, including high-order harmonics. Nowadays, protection against electric shock in low-voltage power systems is commonly performed with the use of residual current devices (RCDs). In the presence of harmonics, the RCDs may have a tripping current significantly different from that provided for the nominal sinusoidal waveform. Thus, in some cases, protection against electric shock may not be effective. The aim of this paper is to present the result of a wide-range laboratory test of the sensitivity of A-type RCDs in the presence of harmonics. This test has shown that the behavior of RCDs in the presence of harmonics can be varied, including the cases in which the RCD does not react to the distorted earth fault current, as well as cases in which the sensitivity of the RCD is increased. The properties of the main elements of RCDs, including the current sensor, for high-frequency current components are discussed as well.

Electrical Consumer Panel with Automated Leakage Current Detector System

In this research work, automated leakage current detector for electrical consumer panel is carried out. Residual Current Device (RCD) is protection equipment that install in the panel for every building where power supply is required. RCD detects leakage current by monitoring the current in both phase and neutral. Mechanical switch has been developed to trip RCD when there are any differences in between these two current. As RCD tripped, power supply cutoff immediately, the developed automated system can detect the Miniature Circuit Breaker (MCB) consists of leakage current. The system will generate instructions to user to open the particular MCB(s) which consist of leakage current and close the RCD to gain back power supply.

Optimal Parameter Design by NSGA-II and Taguchi Method for RCD Snubber Circuit

A genetic algorithm and Taguchi method were used to optimize parameters for the residual-current device (RCD) snubber circuit of a DC-DC flyback converter. The most suitable algorithm was determined by using test functions to compare performance in three multi-objective optimization methods: non-dominated sort genetic algorithm-II (NSGA-II), multi-objective particle swarm optimization (MOPSO), and multi-objective differential evolution algorithm (MODE). Comparisons of coverage rate, distance between non-dominant solutions, and maximum walking distance showed that NSGA-II was superior to both MOPSO and MODE. Therefore, NSGA-II was used to obtain parameter values for the RCD snubber circuit. However, practical application of the parameter values was limited because the values could not meet the specifications required for real-world circuits. Thus, the parameter values obtained by NSGA-II were used in further factor-level experiments performed by Taguchi method. The experimental results indicated that, compared to previous design methods, the proposed NSGA-II and Taguchi method obtains better parameter values for the RCD snubber circuit.

The ElectricalVehicle Simulator for Charging Station in Mode 3 of IEC 61851-1 Standard

As fuel consumption in the transport sector has increased at a faster pace than in other sectors, the use of electromobility represents the main strategy adopted by the automotive industry. In this context, as the number of electrical vehicles (EVs) will increase, it will also be necessary to increase the number of charging stations. The present paper presents a complete solution for charging stations that can be located in the office or mall parking area. This solution includes a mode 3 AC charging stations of International Electrotechnical Commission (IEC) 61851-1 Standard, an EV simulator for testing the good functionality of the charging stations (i.e., communications, residual-current device (RCD) protection) and a software application used for controlling the charging process by the programmable logic controller (PLC).

Human safety ensuring in power supply systems with dead-earthed and insulated neutral wire

In the current paper, the human safety issues in different power supply systems are considered. The conditions for residual-current device utilization and protective characteristics in grounded-neutral and insulated-neutral power supply systems are reviewed. Also, the endangerment factors and accident statistics are analyzed. Based on the given data, the judgment on the safety of different power supply system is given and a novel approach in the residual-current device setting up is proposed. Finally, the topology for IT system performing from TNC system is shown.

Green measures and firm characteristics: evidence from small businesses in an emerging economy

ABSTRACTThis paper attempts to investigate the firm characteristics that could possibly influence the use of green practices in a sample of small firms. Using a probit model and a firm-level dataset containing information on the use of green measures by the firms, the paper investigates the link between firm characteristics and several ‘green’ practices. These green practices include the use of an electricity system equipped with residual current device, the use of energy-efficient devices, the use of measures to save water and finally measures taken to reduce/reuse/recycle waste. The paper finds that there is some evidence indicating that characteristics such as size and financial performance of firms affect the use of green practices in small firms in Mauritius. This is an area that is largely understudied, especially in the case of emerging economies such as Mauritius, given data limitations. Hence, this paper is an important empirical contribution to the literature.

Measures to Minimize Series Faults in Electrical Cords and Extension Cords

In electrical power systems, cords and extension cords are exposed to mechanical damage and other insulation stresses. Mechanical damage to stranded conductors can reduce locally their cross section or break them and cause anomalous local conditions of overheating or arcing. The ordinary protective devices cannot detect the series faults that persist, so the fault point remains energized and is subject to electric shock and fire hazards. Effective protection can be accomplished by implementing active and passive measures: installing arc-fault circuit interrupters or arc-fault detection devices, able to detect arcing faults, or wiring the circuits with a grounding protection conductor to involve the ground in every fault. In this way, residual current protective devices (residual current devices or ground fault protective devices) quickly protect the series faults not only with arc, but also without it. Ground-fault-forced cables facilitate by design the conversion of any kind of cable fault to a ground fault. They are particularly recommended for cords and extension cords, internal circuits to grounded equipment, uninterruptible power system continuity circuits, aircraft circuits, road tunnels, data centers, refrigerated containers parks, residences, and hospitals.

A dual-stage low-power converter driving for piezoelectric actuator applied in flapping-wing micro aerial vehicles

It is essential for flapping-wing micro aerial vehicles to have a driver with compact size, low mass, and high conversion efficiency in low-power application. In this article, a dual-stage low-power converter driving for piezoelectric actuator was designed and implemented, which can be applied in flapping-wing micro aerial vehicles. Using the “simultaneous drive” method, an Residual Current Devices (RCD) passive snubber flyback DC/DC step-up converter cascaded with a bidirectional active half-bridge drive stage is designed. The flyback converter is controlled by pulse width modulation in discontinuous conduction mode to ensure the stability of the output high voltage. The half-bridge drive stage takes the approach of comparing the output voltage signal with an ideal waveform lookup table to generate arbitrary unipolar signals. The proposed converter has a weight of 345 mg, a size of 285 mm2 (19 × 15 mm2), a maximum output power of 500 mW, and a maximum conversion efficiency of 64.5%. An experiment driving for piezoelectric actuator was performed to observe the displacement generated by the converter. According to the experimental results, this converter can be applied in flapping-wing micro aerial vehicles.

Verification of safety in low-voltage power systems without nuisance tripping of residual current devices

Low-voltage power systems require initial and periodical verification to check the effectiveness of protection against electric shock. As a protection in case of fault, automatic disconnection of supply is most often used. To verify such a protection measure, the earth fault loop impedance or resistance is measured. This measurement is easy to perform in circuits without residual current devices. When residual current devices are installed, their unwanted tripping occurs during the measurement, and the verification becomes problematic. The paper proposes a new method of testing the effectiveness of automatic disconnection of supply, without unwanted tripping of residual current devices, especially when their rated residual current is equal to 30 mA. The theoretical background of this method, along with mathematical analysis and experimental verification are presented. The proposed method uses the testing current which is many times higher than the rated residual current of commonly used residual current devices. This is an important advantage in terms of testing accuracy.

Calibration of Residual Current Device (RCD) Testers

Residual current devices (RCDs) are commonly used in low voltage electric power systems, including our households, as protective devices against electric shock. They monitor the balancing current b...

Electrical Safety in Street Lighting Systems Against Loss of Service Continuity and Shock Hazards

For the street light systems, the worldwide trend of electrical standards encourages the adoption of class II equipment such as light fixtures, cabling systems, and other components with double insulation. In installations of a largest number of light poles, safety degradation could be possible and so dangerous electrical potentials may appear on the steel poles that expose people to shock hazards. To decrease the risk to an enhanced low level, also against natural and anthropic events, different solutions are available. In this paper, the authors deal with a combined action of two safety measures for existing installations with steel poles not interconnected by a common grounding system. In particular, these measures are the insulation of the steel poles by an adequate varnish against shock hazards in faulted conditions and the protection of supplying circuits by residual current devices. These RCDs avoid the permanence of ground faults and provide their auto-reclosing with a circuit insulation control.

Electric shock hazard in circuits with variable-speed drives

The conventional approach to electrical safety under fault condition in typical power systems considers earth fault currents of sinusoidal waveform and frequency of 50/60 Hz. However, in circuits with variable-speed drives, there is earth fault current flow with harmonics, and these harmonics influence the threshold of ventricular fibrillation. The paper presents earth fault current waveforms in circuits with variable-speed drives without inverter output (motor) filter and with one of the two types of inverter output filters being used. The details of both filters are presented, and the effect of harmonics of earth fault current on ventricular fibrillation is evaluated. Furthermore, the effect of harmonics, which occurs in circuit of variable-speed drive, on the tripping current of residual current devices is presented. Residual current devices may be utilized to ensure protection against direct and indirect contact, but limitations in their proper operation, due to harmonics, may exist. Operational characteristics of a proposed residual current device dedicated to circuits with earth fault current containing harmonics, as in the variable-speed circuits, are presented.

Commercial arc fault detection devices in military electromagnetic environment

Arc fault detection device (AFDD) is the latest protection device for low voltage circuits. It is used to detect arcing faults that cannot be detected by circuit breakers or residual current devices. Arcing faults are one of the main causes for electrical fires. Arc fault detection device is an active electronic device which operation is typically based on measurement of low and high frequency characteristics of the current passing through. Based on measured current characteristics and the knowledge of the arcing unique deviations in current, arc fault detection device detects possible arcing and disconnects the protected circuit. Arc fault detection device as an active electronic device is a potential source and victim of electromagnetic interference. Electromagnetic compatibility requirements are especially very demanding in military applications where low emission levels and high immunity levels are required. This article presents test results from electromagnetic compatibility testing of five different commercial arc fault detection devices against military standard requirements and analyses the suitability of the arc fault detection devices in military electromagnetic environment.

Practical papers, articles and application notes

Arcing faults, if not detected early, can lead to electrical fires. An Arc Fault Detection Device (AFDD) aims to detect arcing faults that cannot be detected by circuit breakers or residual current devices. AFDD is an active electronic device that measures low and high frequency characteristics of the current passing through it. AFDD can be a potential source and victim of EMI, especially in a military electromagnetic environment, where low emission levels and high immunity levels are necessary. Janne P. Pulkkinen from Finnish Defence Forces, Finland, discusses the EMC requirements of AFDD in the first paper, "Commercial Arc Fault Detection Devices in Military Electromagnetic Environment".

Improving sensitivity of residual current transformers to high frequency earth fault currents

Abstract For protection against electric shock in low voltage systems residual current devices are commonly used. However, their proper operation can be interfered when high frequency earth fault current occurs. Serious hazard of electrocution exists then. In order to detect such a current, it is necessary to modify parameters of residual current devices, especially the operating point of their current transformer. The authors proposed the modification in the structure of residual current devices. This modification improves sensitivity of residual current devices when high frequency earth fault current occurs. The test of the modified residual current device proved that the authors’ proposition is appropriate.

누전차단기와 CT1 서지방호장치의 서지협조의 분석

The objective of this paper is to present whether the surge coordination between connection type 1(CT1) surge protective devices(SPDs) and built-in varistors of residual current device(RCD) for application to energy storage system is established. L-N mode surge coordination characteristics of CT1 SPD connected in parallel with RCD were investigated. The test voltage was supplied by a combination generator, capable of outputting a 10kV voltage, 5kA current into a 2Ω load. BR As a result, the built-in varistors of all sample RCDs against incoming surges were conducted. Most of the incoming impulse currents flows into the built-in varistor of RCD, and some RCDs was damaged at the impulse current of more than 2.5kA. Surge coordination between RCD and CT1 SPDs was not achieved. In addition, the minimum value of continuous operating voltage(Uc) for SPD connected between phase conductor and ground in TT grounding system should be a value of 1.5USUB0/SUB, where USUB0/SUB is the voltage to ground. Some SPDs used in this work are not acceptable to the above requirement.