How does a single-phase isolation transformer limit short-circuit current to protect system safety?

Short-circuit fault is one of the most common fault types in power systems. When the insulation of electrical equipment is damaged or personnel misoperation causes conductors of different potentials to be directly connected, a short-circuit loop will be formed. At this time, the current will bypass the load and flow directly through the short-circuit loop, causing the current to increase sharply, far exceeding the rated current of the equipment. Short-circuit current will not only cause physical damage such as overheating and burning of equipment, but may also cause safety accidents such as fire and explosion due to arc discharge and spark splashing.

In order to deal with short-circuit faults, the power system needs to take a series of protection measures. Among them, limiting short-circuit current is a key link in reducing the harm of faults. By increasing the system impedance, the growth rate of short-circuit current can be effectively slowed down, its peak value can be reduced, and thus the damage to equipment and systems can be reduced.

A single-phase isolation transformer is an electrical device with electrical isolation and voltage conversion functions. In power systems, it is usually used to convert electrical energy of one voltage level into electrical energy of another voltage level, while achieving electrical isolation to ensure the safety of equipment and personnel. However, the functions of a single-phase isolation transformer are far more than that. By adjusting the turns ratio of its primary winding and secondary winding, the single-phase isolation transformer can also achieve impedance transformation, that is, change the relationship between input impedance and output impedance.

When a short-circuit fault occurs, the single-phase isolation transformer can increase the total impedance of the system through its impedance transformation function. When the short-circuit current flows through the transformer, due to the increase in impedance, the current will be hindered, its growth rate will slow down, and the peak value will also be reduced. In this way, the degree of damage to the equipment and system caused by the short-circuit current will be significantly reduced.

The mechanism of limiting short-circuit current by the single-phase isolation transformer is mainly based on its impedance transformation function. In the power system, the impedance of the transformer is mainly composed of its inductance, capacitance and resistance and other components. When a short-circuit fault occurs, these components will act together on the short-circuit current to form a certain obstruction.

The inductance element of the single-phase isolation transformer has a significant obstruction effect on the short-circuit current. At the moment of short circuit, the inductance element will generate self-induced electromotive force, trying to prevent the rapid change of current. This obstruction is proportional to the value of the inductance. The larger the inductance, the stronger the obstruction. Therefore, by increasing the inductance value of the transformer, the magnitude of the short-circuit current can be further limited.

The capacitance and resistance elements of the single-phase isolation transformer also have a certain hindering effect on the short-circuit current. The capacitance element will absorb part of the electrical energy at the moment of short circuit and slow down the growth rate of the current; while the resistance element will reduce the peak value of the current by consuming electrical energy. The combined effect of these elements makes the single-phase isolation transformer perform well in limiting the short-circuit current.

Single-phase isolation transformers are widely used in power systems, not only in limiting short-circuit current. However, in terms of short-circuit fault protection, its unique impedance transformation function gives it a significant advantage.

Single-phase isolation transformers effectively reduce the magnitude of short-circuit current by increasing the system impedance, thereby reducing the degree of damage to equipment and systems caused by faults. This helps to extend the service life of equipment, reduce maintenance costs, and improve system reliability.

Single-phase isolation transformers have electrical isolation functions, which can ensure that faults do not spread to the entire system. When a short-circuit fault occurs, the transformer limits the fault current to a local range, preventing it from spreading to other equipment and system parts, thereby reducing the impact of the fault on the entire system.

The single-phase isolation transformer also has the advantages of simple structure, small size and light weight, which makes it easy to install and maintain in the power system and reduces the complexity and cost of the system.