A new approach for AC loss reduction in HTS transformer using auxiliary windings, case study: 25 kA HTS current injection transformer

Abstract

AC loss is one of the important parameters in HTS (high temperature superconducting) AC devices. Among the HTS AC power devices, the transformer is an essential part in the electrical power system. The AC losses in an HTS tape depend on the magnetic field. One of the techniques usually adopted to mitigate the unwanted magnetic field is using a system of coils that produce a magnetic field opposite to the incident one, reducing the total magnetic field. In this paper adding two auxiliary windings to the HTS transformer to produce this opposite magnetic field is proposed. The proper use of these auxiliary windings could reduce the leakage flux and, therefore, the AC loss. A mathematical model is used to describe the behaviour of a transformer operating with auxiliary windings, based on the theory of electromagnetic coupled circuits. The influence of the auxiliary windings on the leakage field is studied by the finite element method (FEM) and the AC loss of an HTS transformer was calculated. Also, the simulation results show that employing auxiliary windings will improve the HTS transformer efficiency.

Heuristic mathematical formulations and comprehensive algorithm for optimal decision making for power system cabling

“…These tests are performed using high-current, low-voltage test equipments, such as CIS, by means of controlling the current values, as well as the operating time of the Equipment Under Test (EUT) [9][10][11]. Due to high current passing through secondary windings, a considerable amount of interference magnetic field is dispersed within the system tank, giving rise to malfunction or damage to the control tools [10,13].…”

“…As the block diagram in Figure 6 shows, the CIS consists of different gears. Thus, for instance, to test an EUT for ''10 kA-3 s'' in a 25 kA system, some precautionary measures are generally considered appropriate for system protection, such as the accuracy of the tap-changer setting, (L 2 ) and its connection point during the current setting, for different EUT impedances [9].…”

“…Cost computation is performed based on Eqs. (9) and (10) from which the price of the cable support is shown equal to zero (P Fe = 0) for the CIS, since cables having small cross-sections can easily pass through the tank columns or available space with no cable support system. There is also no civil work costs in the CIS, so P cm = 0.…”

“…Referring to Eqs. (9) and (10), cost criteria can be calculated. The design criteria for the proposed cabling route in the 132/20 kV HV substation take into account the new practice and material types, cost of channel construction, cable support system and its installation.…”

“…Therefore, an algorithm for an optimal cabling route based on AHP is presented. The proposed scheme is applied to a high voltage substation [1][2][3] and a 25 kA current injection system (CIS), which mainly incorporates a 25 kA-125 kVA transformer delivering an output secondary current (25 kA), as closely proportioned to the primary current as possible, at relatively low voltages (1-5 V) [9][10][11][12]. Results suggest a generic hierarchy algorithm for cabling routes to prioritize critical factors and to formulate strategies for implementation in various types of power system over a wide range of conditions.…”