Short circuit current limiter

Short-circuit currents are an inevitable phenomenon in a power network. They occur during various damage to network components (cables, transformers, switches, consumer devices), during lightning discharges and for other reasons. Short-circuit currents exceed the normal values ​​of currents tens and hundreds of times, exerting a huge load on all network components, damaging them, causing equipment emergency stops, initiating fires and explosions. The impact of short-circuit currents leads to an increase in the cost of replacing and repairing equipment, fines for poor quality of power supply to consumers, lost revenue. In developing power systems, the level of short-circuit currents has a steady upward trend, which sometimes leads to the need to replace equipment with more powerful equipment. To reduce damage, modern electrical equipment (cables, transformers, circuit breakers) is designed with a sufficient margin for current loads. For example, a circuit breaker with a rated current of the order of 1 ÷ 2 kA is designed so that in emergency mode it can be capable of switching current up to 40, 50, 63 or 80 kA. This leads to a rise in the cost of equipment, an increase in size, and the appearance of additional difficulties in operation. Topological (network division) and technical means (installation of current - limiting reactors ) used to limit short-circuit currents can reduce short-circuit currents. However, at the same time, these approaches increase the loss of electricity in the network, limit the flow of power, reduce the controllability and reliability of power supply, and prevent the connection of new consumers. OTKZ allow to reduce the maximum level of short circuit currents in the network without these disadvantages. OTKZ allow to provide protection against short circuit currents of trunk, distribution and traction networks; reduce the heat load on the electrical components of various equipment; provide smooth start-up of powerful electric motors; to simplify the connection to the local generation power grid. OTKZs can have a special effect on the quality of power supply to industrial plants, allowing in the event of a short circuit to maintain voltage stability on the tires due to their speed, without interrupting or violating the conditions of the process.

Resistor-type superconducting short-circuit current limiters use the property of superconductors to transition from the superconducting to the normal (resistive) state when a certain current density, called critical, is exceeded. Such a nonlinear dependence of resistance on current is characteristic exclusively of superconducting materials and is characterized by a change in resistivity by more than 10 orders of magnitude. In the resistive state, the superconducting element TOU limits the current due to its active resistance, while Joule heat is released on it and the element heats up. To return to the superconducting, low-resistive state, the superconducting element must be again cooled to operating temperature, and the current flowing through it must be lower than critical. Resistor-type superconducting OTKZ has two operating modes: nominal (with resistance close to zero) and current-limiting (with resistance of units and tens of ohms). The transition between these modes is determined by the fundamental physical properties of the superconductor, that is, an external signal is not required to initiate the transition between these modes. The transition between the modes is very fast, with a characteristic time of about 1 millisecond, which is much less than the typical time for tripping a circuit breaker. In the power system, the work of the superconducting CTB should be coordinated with the work of the protections. As a rule, after emergency control shuts down the damaged area, the superconducting OTKZ returns to its nominal operating mode. With the advent of practical materials in the 2000s - high-temperature superconducting (HTSC) wires of the 2nd generation, resistive type HTSC OTKZ began to be developed and implemented in various types of power grids. Currently, HTSC OTKZ voltage classes from 10 to 220 kV operate in the energy networks of Germany, Great Britain, South Korea, the USA, Thailand and other developed countries. In the Russian Federation, the integration of the first resistive type HTSC OTZ to the 220 kV voltage class began at a substation in Moscow in 2016 ^[1] .

• Superconducting Fault Current Limiters
• High temperature superconductor fault current limiters: concepts, applications, and development status
• Fault Current Limiter and Their Types
• 2012: YBCO-tape FCL enters service in German private grid
• Russian HTSC OTKZ