Power transformers in service are subjected to a wide variety of electrical, mechanical and thermal stresses capable of producing insulation faults. This type of failure figures amongst the most costly faults in distribution networks since it produces both machine outage and electrical supply interruption. Major research effort has therefore focused on the early detection of faults in the insul...

This paper introduces a cutting-edge transformer technology – the piezoelectric transformer – currently considered as a potential candidate to replace magnetic transformers in resonant switching converters. Magnetic transformers are extensively used for providing step-up and step-down voltages while allowing input to output isolation in ac-dc and dc-dc converters. Even with the extensive use, t...

Yoshihiro Konishi, Member (Fuji Electric Co., Ltd.) Mutsuo Nakaoka, Member (Yamaguchi University) This paper presents a novel type flyback DC-DC converter using snubber energy regenerative circuit. The proposed snubber regenerative circuit consists of passive circuit components such as auxiliary transformers, inductors, capacitors and diodes, and has a high reliability. The operation principle ...

This thesis describes how to provide standardized, current based, differential protection for any three-phase power transformer, including phase-shifting transformers with variable phase angle shift and transformers of all construction types and internal on-load tap-changer configurations. The use of standard transformer differential protection for such applications is considered impossible in ...

This paper investigates protection integrity of distribution transformers in Ghana. The purpose of the study was to find the main causes of distribution transformer failures in Ghana. The study was conducted in the Ashanti East Region, one of the operational areas of Electricity Company of Ghana ECG with high incidence of distribution transformer burnouts. Data on status of protection systems o...

An original electronic device for compensating ratio and phase-displacement errors, of measuring current transformers and clamp-on probes, is proposed. It is specially intended for low-frequency applications (power frequency and its harmonic components), where the magnetizing current is the main cause of measuring errors. This system reduces the magnetic flux in the transformer core, reducing i...

SiC MOSFETs are applied to constitute a three-phase, 5-kW LLC series resonant dc/dc converter with isolation transformers. A switching frequency of around 200 kHz for the transistors successfully reduces the volume of these isolation transformers, whereas insulatedgate bipolar transistors (IGBTs) are not capable of achieving such a high switching speed. The high-voltage tolerance of SiC MOSFETs...

Turning to Renewable Energy Sources (RES) is the most logical politics in securing the modern society from critical changes in earth increasing temperature. However, Distributed Generation (DG) sources could lead to new challenges in electricity network, mainly allocation of DG sources in distribution level of power system will set the existing network under stress of power flow parameters. The...