TECHNICAL FIELD

The invention relates to a superconducting fault current limiting transformer for limiting fault current in transformer to reduce damage caused by fault current.

BACKGROUND

The increasing demand for electrical energy brings about the continuous expansion and complexity of power systems. The commissioning of new generating plants, lines, and loads increases the power flow in the system and the level of short circuit current that will occur during any malfunction accordingly. This situation may cause the strength limits of the power system equipment designed and/or selected according to certain short circuit current sizes to be forced or even damaged. Therefore, limiting fault currents is becoming more important day by day.

Fault current limiters have been developed to ensure that current is limited in the event of a malfunction. Under normal conditions, voltage fluctuation in the network with a fault current limiter (FCL) should not exceed the limits specified in the electrical network regulation. Fault current limiters in this case should not affect the normal operation of the power system and the characteristics of the lines. In order to limit the first peak value (peak) of the fault current, the FCL must be activated quickly. However, an increase in impedance very quickly may cause unwanted high voltages in the circuit. In the article published by Hoshino et aL, 2001a, 2001 b; Meerovich et aL, 1995a, 1995b, it is considered that a period of 2-4 ms is sufficient to limit the first peak for a power system operating in the frequency range of 50-60 Hz, without causing any high voltage in the network. The difference between superconducting fault current limiters compared to SFCLs is the use of superconductors as limiters. The activation time for limiting the use of superconductors is very short and the first peak value of the fault current can be limited to approximately 2-4 ms. In traditional FCLs, it does not seem possible to limit current within this time. Many SFCL designs have been developed to date. These can be given as resistive, inductive, saturated iron core, and bridge type. It contains different technical features according to the region of use due to the different types of SFCL and the different fault currents in the electrical network. It is very difficult to make a meaningful comparison between the SFCLs because their intended use in the network includes different characteristics. In recent years, it is seen that the research on SFCLs and the prototypes produced are concentrated on the resistive type. Due to the high voltage drop along the superconductor, the need for shunt resistance, and the long recovery time in resistive FCLs, it cannot provide effective use. Especially the long recovery period causes inefficient use of energy. However, the fact that the line current passes directly through the superconducting winding has the potential to create significant technical complications. There is a possibility of damage to electrical insulation, especially at low temperatures. The high amount of superconductor use brings a mandatory increase in cost. It is considered that there is a need for cost-cutting technological developments.

As a result, all the above-mentioned problems have made it imperative to innovate in the relevant technical field.

BRIEF DESCRIPTION OF THE INVENTION

The present invention relates to a superconducting fault current limiting transformer for eliminating the above-mentioned disadvantages and bringing new advantages to the related technical field.

An object of the invention is to provide a superconducting fault current limiting transformer to prevent damage to a transformer due to fault current.

Another object of the invention is to provide a superconducting fault current limiting transformer that allows the operation to continue by ensuring that the fault is eliminated without the need for power failure in short-term fault situations.

The present invention is a superconducting fault current limiting transformer, comprising a metal core provided in a layered structure, a first coil provided in a first extension of said metal core, and a second coil provided in a second extension, in order to realize all the objects that will emerge from the abovementioned and the following detailed description. Accordingly, the metal core comprises at least one-third extension, it comprises a superconducting winding that prevents the magnetic flux from passing over the third extension while in the superconducting state placed on the third extension and provides a limitation of the fault current by ensuring that the magnetic flux passes through the third extension when in a fault state. In this way, damage to the transformer is prevented by preventing damage that may occur in case of fault. At the same time, there is no need to stop the operation of the transformer by ensuring that the fault current is limited in a short time. This reduces the energy loss that occurs.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1 shows a representative view of a superconducting fault current limiting transformer.

DETAILED DESCRIPTION OF THE INVENTION

In this detailed description, the subject matter of the invention is explained only by means of examples that will not have any limiting effect for a better understanding of the subject matter.

The invention relates to a superconducting fault current limiting transformer (10) to reduce damage due to fault current by limiting fault current in a transformer.

Said superconducting fault current limiting transformer (10) comprises a metal core (100) provided in a layered structure, as shown in Figure 1 . The iron core mentioned in a possible embodiment of the invention consists of 23 layers in total. The number of layers mentioned may vary according to the intended use. The fact that the core is provided in a layered structure allows the metal core (100) to turn into a circular structure and allows the magnetic flux leaks to be minimized. It is preferred to use the iron core as the metal core (100) in a possible embodiment of the invention. In another possible embodiment of the invention, it is preferred that the sheet thickness used for the iron core is 0.3 mm. In another possible embodiment of the invention, there is a silicon coating of 3% of said sheet thickness.

The metal core (100) includes a first extension (101 ) for winding a first coil. The first coil mentioned in a possible embodiment of the invention comprises the aluminum winding. The metal core (100) includes a second extension (103) for winding a second coil. The second coil mentioned in a possible embodiment of the invention comprises aluminum winding.

The metal core (100) comprises a third extension (105) provided between the first extension and the second extension (103). The superconducting fault current limiting transformer (10) includes a superconducting winding (106) disposed of in said third extension (105). Said superconducting winding (106) prevents the magnetic flux from passing through the central iron core while in the superconducting state. Thus, the magnetic flux generated by the first coil flows through the first extension (101 ) surrounded by the first coil towards the second extension (103) surrounded by the second coil and provides its entanglement from the outer frame. In case of a fault (short circuit), the superconducting winding (106) surrounding the metal core (100) in the third extension (105) enables the magnetic flux to pass through the third extension (105) by making a sudden transition ("quench") to the normal state. The magnetic flux loop is completed so that it flows from the first extension (101) to the third extension (105). By reducing the heat through the liquid nitrogen tank provided to the superconducting winding (106), it is ensured that the superconductor winding is protected from the increasing temperature due to its magnetic flux. This ensures that the fault current in the circuit is limited quickly. Thus, Eddy current losses caused by the structure of the iron core are minimized by the laminated structure of the iron core, ensuring the efficient operation of the transformer. The fault current is quickly removed from the circuit by the superconducting fault current limiting transformer (10). Thus, it is ensured that the fault is eliminated without the need for a power cut in case of short-term fault. This ensures the continuity of the energy.

An exemplary operating scenario of the invention is described as follows:

The superconducting fault current limiting transformer (10) allows for inducing current in the opposite direction on the superconducting winding (106) in the reset direction of the net magnetic current passing through the third extension (105). Thus, the flow of the current through the third extension (105) is prevented under normal conditions. There is no direct current supply in the superconducting fault current limiting transformer (10). Under normal operating conditions, the impedance of the superconductor is low because the net magnetic flux in the third extension (105) where the superconducting winding (106) is located is zero. In the event of a fault, the impedance of the superconductor increases with the increase of the net magnetic flux in the iron core as the superconducting winding (106) rapidly returns to its normal state. In such a case, the majority of the magnetic flux accompanying the electrical network to be protected connection to the second coil passes through the core where the superconducting winding (106) is located, allowing the fault current to be limited at the first peak value (within approximately 5 ms).

The protection scope of the invention is specified in the attached claims and cannot be strictly limited to those explained in this detailed description for illustrative purposes. It is evident that a person skilled in the art may exhibit similar embodiments in light of the foregoing without departing from the main theme of the invention.

REFERENCE NUMBERS GIVEN IN THE FIGURES

10 Superconducting fault current limiting transformer

100 Metal core 101 First extension

102 First coil

103 Second extension

104 Second coil

105 Third extension 106 Superconducting winding