David Antonio Aragón Verduzco

Access to reliable low-voltage power is challenging where distribution networks are unavailable or uneconomic, including switching substations, construction sites, and remote communities. Station Service Voltage Transformers (SSVTs), also known as Power Voltage Transformers (PVTs), address this problem by supplying useful low-voltage power from transmission or subtransmission networks. This paper reviews SSVT terminology, operating principles, construction architectures, electromagnetic and thermal modeling, testing, reliability, monitoring, and applications. The most extensively documented applications concern substation auxiliary services, while rural minisubstations are supported by SSVT-specific development studies and selected field reports. Electric mobility has progressed beyond a prospective concept: an SSVT-based, transmission-connected micro-substation pilot has demonstrated direct 220 kV-to-low-voltage supply for electric-vehicle (EV) charging. However, SSVT-specific characterization for this application, long-term operating data, and application-oriented design guidance remain limited. Key research gaps concern coupled multiphysics validation, nonlinear-load performance, reliability statistics, techno-economic assessment, and life-cycle analysis. Particular attention is given to distinguishing applications already demonstrated with SSVT technology from emerging uses for which validation, standardization, or long-term operating experience remains limited. The review concludes by proposing a roadmap to develop reproducible, experimentally validated, and digitally supported SSVT platforms for remote energy access and selected electric-mobility applications.

Transformers are essential in electrical networks, and their failure can lead to the shutdown of a section or the entire grid. This study proposes a combination of techniques for early fault detection, distinguishing between small load imbalances and incipient interturn short circuits. An experimental setup was developed using a three-phase transformer bank with three single-phase dry-type transformers. One transformer was modified to create controlled short circuits of two and four turns and to simulate a load imbalance by reducing the winding by four turns. The main contribution of this research is the development of a combined diagnostic approach using instantaneous space phasor (ISP) spectral analysis and infrared thermal imaging to differentiate between load imbalances and incipient interturn short circuits in transformers. This method enhances early fault detection by identifying distinctive electrical and thermal signatures associated with each condition. The results could improve transformer monitoring, reducing the risk of failure and enhancing grid reliability.

This work is a proposal of a finite element model to obtain the electromagnetic performance of a squirrel cage motor considering the magnetic wedges and radial vents. To analyze the electromagnetic performance at the design stage, without the need to build a prototype, the paper proposes a simple two dimensions finite element model, which includes components as magnetic wedges used to hold the windings in the stator slots, radial vents in the core, which are part of motor cooling system, and edge effects to improve the model. The stator and rotor cores are modeled with an equivalent homogeneous permeability, obtained from the combination of the radial air vents of rotor and stator and the magnetic core material. The permeability of magnetic wedges is also considered. Edge effects considered are the end winding leakage inductance, representing the leakage flux in the end coils of the stator, and an equivalent impedance between rotor bars due to conductivity and leakage flux in the rings of the squirrel cage. The results obtained are compared with experimental tests performed in steady state to validate the model. Furthermore, no-load, and blocked-rotor tests are simulated to estimate the equivalent circuit parameters and draw the typical induction motor torque-speed curve, which is compared with the obtained curve by means of Thevenin’s theorem. With this proposed model, the results are close to the ones obtained experimentally. The implementation of a 3D model is complex, and the computational cost can be much higher, compared to the 2D model developed here.

A new analytical method is presented for computing the leakage inductance of the single-end coils of electrical machines, based on the solution of Maxwell’s equations, which considers core eddy currents. Maxwell’s equations are solved in general form in two regions: inside and outside the core, employing appropriate boundary conditions and an iteration scheme. Asymptotic methods are effectively employed for the analytical calculation of Green’s functions in both the regions. Analytical results are compared with 3-D finite-element computations. The comparison shows a close correspondence between the analytical and numerical results. Our formula is the basis for further computations of the end-winding leakage inductance of rotating electric machines.