Converter transformers are the key and the most important components in high voltage direct current (HVDC) power transmission systems. Statistics show that the failure rate of HVDC converter transformers is approximately twice of that of transformers in AC power systems. This paper presents an approach integrated with a two-dimensional cloud model and an entropy-based weight model to evaluate t...

We study the relation between state transformers based on directed complete partial orders and predicate transformers. Concepts likèpredicate', `liveness', `safety' and`predicate transformers' are formulated in a topological setting. We treat state transformers based on the Hoare, Smyth and Plotkin power domains and consider continuous, monotonic and unrestricted functions. We relate the transf...

Different stress factors impact power transformers during service. In most cases, the effects of additional direct current (DC) components are not taken into consideration. Nevertheless, this contribution considers DC or quasi-DC components which occur in the German transmission grid (400 kV level). Current measurements are therefore performed at several grounded star points of grid coupling po...

Partial discharge (PD) pattern recognition is an important tool in HV insulation diagnosis. A PD pattern recognition approach of HV power transformers based on a neural network is proposed in this paper. A commercial PD detector is firstly used to measure the 3-D PD patterns of epoxy resin power transformers. Then, two fractal features (fractal dimension and lacunarity) extracted from the raw 3...

In a power system, a contingency refers to an outage of power system components such as transformers, generators, lines, etc. due to faults or failure. A contingency could lead to voltage and power flow problems. This paper describes practical contingency studies based on a real power system provided by a utility. The aim of this study is to find out contingencies that cause undervoltage, overv...

The development of power electrical systems causes attention to accuracy of protection elements and measurement values. So we need some new measuring devices with high accuracy for power transmission lines. One of these devices is Optical Current Transformer (OCT). Optical current transformers are suitable for power system protection and can replace the magnetic current transformers. In this pa...

Introduction This application guide addresses the limiting conditions of connecting transformers in parallel and loading considerations when turn ratios, impedances, and kVA ratings are different. Most transformers installed in parallel have the same kVA, turn ratios, and impedances, which can make it difficult for power engineers in industrial and commercial facilities to understand circulatin...

In this paper we propose transformer-based solutions to several power quality problems. Elsewhere we have shown how to solve the acoustical noise emission problems. In this paper we introduce toroidal transformers with reduced inrush currents, transformers with reduced electromagnetic emissions, and other transformers useful to reduce the transfer of harmonics. With the low-inrush transformers ...

This paper proposes a method for extending the ability of rotary power flow controller (RPFC) using tap-changer of the RPFC’s transformers. A detailed model of the device is presented to analyze the effects of the tap changer operation on the performance of the RPFC. To evaluate the results, the RPFC model is simulated using PSCAD/EMTDC software. Dynamic operation of the RPFC on a 400 kV transm...