Behavior of Residual Current Devices at Frequencies up to 50 kHz

The use of residual current devices (RCDs) is obligatory in many types of low-voltage circuits. They are devices that ensure protection against electric shock in the case of indirect contact and may ensure additional protection in the case of direct contact. For the latter purpose of protection, only RCDs of a rated residual operating current not exceeding 30 mA are suitable. Unfortunately, modem current-using equipment supplied via electronic converters with a pulse width modulation produces earth fault currents composed of high-frequency components. Frequency of these components may have even several dozen kHz. Such components negatively influence the RCDs’ tripping level and, hence, protection against electric shock may be ineffective. This paper presents the results of the RCDs’ tripping test for frequencies up to 50 kHz. The results of the test have shown that many RCDs offered on the market are not able to trip for such frequencies. Such behavior was also noted for F-type and B-type RCDs which are recommended for the circuits of high-frequency components. Results of the test have been related to the requirements of the standards concerning RCDs operation. The conclusion is that these requirements are not sufficient nowadays and should be modified. Proposals for their modification are presented.

The overcurrent protection characteristics testing digital substation intelligent electric devices

The electric power industry digital transformation features and the intelligent electronic devices (IEDs) introduction in the low-voltage circuits of power stations and substations are considered. The analysis of normative documents and standards is carried out. The features of scheduled maintenance of relay protection and automation devices are determined, the possibilities and prospects of organizing condition-based maintenance are considered. The mandatory steps required for any type of maintenance are defined. A method for checking the electrical and time characteristics of the overcurrent protection of an intelligent electronic device is proposed. The device is designed in accordance with the IEC-61850 standard and operates in the local area network of a digital substation of architecture III

Adapter-Transceiver for HF Equipment PLC Technology

The paper analyses the features of PLC technologies and describes the circuitry solutions for HF equipment adapters used and their operation modes. It also proposes a new type of transceiver adapters based on a new construction principle that implements a magnetoelectric effect in the structure of a composite. One of the main components of the proposed adapters, which actually translates the HF information signal into the phase wires of the power line, is a ferrite core. The physical effects underlying the operation of the proposed transceiver adapter are analyzed. The main distinguishing feature of the proposed adapter is the absence of transformer and galvanic connections between the high-voltage power line of the power supply network and low-voltage information circuits, which ensures that the effect of the operational high voltage of the power supply line on the low-voltage circuits of HF equipment is blocked. This allows for an easy integration of the proposed version of the adapter-transceiver into standard HF equipment for PLC technologies, boosting the level of its function. The developed new types of adapter-transmitter and adapter-receiver were experimentally tested as part of an experimental fire alarm system, which uses two types of transmission channels: based on wireless technologies employing a radio channel and a PLC technologies-based one.

SmartLVGrid Platform—Convergence of Legacy Low-Voltage Circuits toward the Smart Grid Paradigm

The current electrical system is transitioning towards a new technological model called the smart grid. The transition duration between the traditional Electric Power System (EPS) and the full smart grid depends on well-designed strategic plans, implementing transition models that are as close to smart grids as possible, based on the processes and technological resources available at the time, but always considering their economic feasibility, without which no solution thrives. In this article, we present a method for convergence of the traditional power distribution grid to the smart grid paradigm by retrofitting the legacy circuits that compose this grid. Our results indicate that the application of such a method, through a distributed system platform with integrated technological resources added to the legacy infrastructure, converts these passive grids into intelligent circuits capable of supporting the implementation of a smart grid with a broad scope of functionalities. Based on a novel retrofitting strategy, the solution is free from the cost of replacing or significantly modifying the legacy infrastructure, as verified in deploying other currently available solutions.