DC Circuit Breaker v.s. AC Circuit Breaker, Know Their Difference

July 29,2022

The DC circuit breaker and the on-load voltage regulation both refer to the voltage regulation mode of the transformer tap changer. The difference is that the off-excitation voltage regulator does not have the ability to switch gears with load, because the tap changer is in the process of changing gears. There is a short-term disconnection process, and disconnecting the load current will cause arcing between the contacts to burn the tap changer or short-circuit, so the transformer must be powered off when shifting gears. Therefore, it is generally used for transformers whose voltage requirements are not very strict and do not need to be adjusted frequently.

The on-load tap-changer can switch gears with load, because the on-load tap-changer does not have a short-term disconnection process during the gear shifting process. After a transition resistance transition, it switches from one gear to another. Therefore, there is no arcing process in which the load current is disconnected. Generally used for transformers with strict voltage requirements that need to be adjusted frequently.

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Difference between DC circuit breaker and AC circuit breaker

The structure of the two is different:

The structure of the AC circuit breaker: the AC high voltage circuit breaker includes a casing, a high-voltage porcelain bottle arranged on the casing, a three-phase high-voltage input end, and a three-phase high-voltage output end. Electrode and controller, linear electromagnetic pusher includes iron core, coil, permanent magnet, armature, push rod and electromagnetic positioning lock, and push rod is arranged between movable electrode and linear electromagnetic pusher.

Structural composition of DC circuit breakers: The topology of DC circuit breakers is complex and diverse. According to the different key breaking devices in DC circuit breakers, DC circuit breakers can be divided into three categories: mechanical DC circuit breakers, all-solid-state DC circuit breakers A hybrid DC circuit breaker that combines a mechanical switch, a mechanical switch and a solid state switch.

The structural characteristics of the two are different:

Structural characteristics of AC circuit breaker: The circuit breaker adopts a three-phase strut structure, which has the characteristics of stable and reliable breaking performance, no combustion and explosion danger, maintenance-free, small size, light weight and long service life.

Structural characteristics of DC circuit breakers: The difficulties in the development of DC circuit breakers are manifested in two aspects. First, the DC system current has no natural zero-crossing point, and the mature arc extinguishing technology in AC circuit breakers cannot be applied; secondly, the inductive components in the DC system cannot be applied. It stores a huge amount of energy, which significantly increases the difficulty of breaking the DC fault current.

The overview of the two is different:

Overview of AC circuit breaker: AC high voltage circuit breaker is the main power control equipment of the substation. When the system is in normal operation, it can cut off and connect the no-load and load current of the line and various electrical equipment; when the system occurs In the event of a fault, it cooperates with the relay protection to quickly cut off the fault current to prevent the expansion of the scope of the accident. Therefore, the working quality of the high-voltage circuit breaker directly affects the safe operation of the power system.

Overview of DC circuit breaker: The DC circuit breaker combines power electronic devices and is a circuit breaker for breaking the DC circuit. The moment when the DC circuit is realized is the current zero-crossing point. DC circuit breakers can generally be divided into mechanical DC circuit breakers, solid-state DC circuit breakers and hybrid DC circuit breakers. Among them, the control of power electronic devices and DC arc extinguishing are the key technologies of DC circuit breakers.