Application of Vacuum Circuit Breakers in Low Voltage Distribution Boxes

Vacuum circuit breaker is one of the key power distribution equipment electrical devices with wide range of consumption in low voltage distribution boxes. Due to the insufficient or incomplete understanding of the protection characteristics of low voltage isolating switches and their application scope, various errors or problems often occur in the specific application of low voltage vacuum circuit breakers. In the following, the definition, key technical characteristics and main parameters of low voltage vacuum circuit breakers will be described, in order to enable customers to have a deeper understanding of low voltage vacuum circuit breakers.

Definition of Low Voltage Vacuum Circuit Breakers

The voltage of circuits with a frequency of 50Hz or 60Hz and rated voltage of 1200V or below, and direct current rated voltage of 1500V or below is referred to as low voltage. Low voltage electrical products (including low voltage circuit breakers) are used for the above-mentioned electrical network voltage. According to their relationship with the use system, low-voltage electrical devices can be divided into two categories: distribution electrical devices and control electrical devices. The category of distribution electrical devices includes low-voltage circuit breakers and fuses, knife switches, transfer switches, as well as load break switch 33kv, among others.

A low voltage vacuum circuit breaker is a switch electrical device that can not only connect and disconnect normal load current and overload current, but also can connect and disconnect short-circuit current. In addition to its control function, low voltage circuit breakers also have certain protective functions, such as overload, short circuit, undervoltage, and leakage protection. There are many ways to classify low voltage circuit breakers, which can be classified according to their structure, functions, and different protection objects. According to their structure and functions, they can be divided into two categories: plastic shell type and universal type; According to different protection objects, they can be divided into four types: distribution protection type, motor protection type, household and similar household protection type, and residual current (leakage) protection type. These circuit breakers are commonly used in pole mounted switchgear and play a vital role in ensuring the safety and reliability of low voltage electrical systems.

Key Performance Parameters of Low Voltage Vacuum Circuit Breakers

(1) Rated voltage: refers to the rated effective value of normal operating voltage that can be continuously applied to the electrical equipment without adverse effects.

(2) Rated frequency: Rated frequency can be 50Hz or 60Hz.

(3) Rated current: The rated current level of the vacuum circuit breaker is indicated by the specification and construction of a larger trip device that can be installed in the same framework or plastic machine housing. The rated current of the vacuum circuit breaker is the rated continuous current, i.e. the current that the trip device can pass for a long time.

(4) Temperature rise: The working temperature of each component of the VCB vacuum circuit breaker must be less than a rated value.

(5) Power frequency withstand voltage: After the circuit breaker is closed, a power frequency voltage value parallel to each electrode and the metal casing is applied between the incoming line and the outgoing line, and between the circuit breakers. It is not allowed to flash or breakdown according to the level of the insulation voltage.

(6) Protective characteristics of overload and short circuit: Two-stage protection, three-stage protection, single-phase ground fault protection.

(7) Residual action current: Under certain conditions, only the residual current is used to make the VCB vacuum circuit breaker act.

(8) Residual non-action current: Under certain conditions, only the residual current is used to keep the circuit breaker from acting.

(9) Service life: It can be divided into mechanical life and battery life.

(10) Short-circuit sectionalizing ability: There are limits to the ability of short-circuit sectionalizing and operating sectionalizing.

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