Current distribution systems require circuit breakers to provide isolation and safety protection. In addition to circuit control for the passage of current and simple short-circuit and overload protection, high demands are placed on the safety of personnel, equipment and the reliability of the distribution system in particular. The development and procurement of products must therefore also focus on the following three aspects: personal safety, protection of electrical circuits and equipment, reliability and uninterrupted supply of electricity.

Let me introduce the characteristics of the moulded case circuit breaker, as follows:

1. rated limit short-circuit breaking capacity Icu. circuit breaker breaking capacity for analysis of technical indicators are rated working limit short-circuit breaking capacity Icu and rated operating process in the presence of a variety of short-circuit breaking capacity Ics. Ics as an important feature of their own design parameters, and not just by simply can consider the breaking capacity of different circuit breakers, but we as a study of a breaking indicator, but also It is after breaking several short-circuit problem faults, can still ensure that it can manage the work properly. For molded case circuit breakers in general business, there should be a student does not have enough Icu, can interrupt the short circuit calculation work current to make the switch tripped. According to the provisions of the plastic case circuit breaker Ics as long as we time cost greater than 25% Icu even if they do not have a qualified. At present, the vast majority of circuit breakers on the market in China ICU (50% -75%) between the ICU, so the power supply enterprises on the distribution network system requirements are low, can only consider ICU.

2. Current limiting opening capacity refers to the ability of the circuit breaker to limit the current generated by carrying out a fault during a short circuit and tripping. When a circuit breaker is short-circuited, the contacts can be broken quickly to produce an impact arc, which equates to a rapidly developing increase in arc resistance in the string in the line, thus achieving an increase in the system fault analysis current. In addition, the shorter the circuit breaker opening time, the closer the IC is to the Icu, the better the current limiting effect, and the electromagnetic effect, the short-circuit current on the circuit breaker and electrical equipment produced by the negative effects of electrical and thermal effects can be greatly reduced, thus extending the service life of the circuit breaker.

3. short-circuit protection, that is, the short-circuit circuit breaker short-circuit instantaneous tripping, after the change in load to pay attention to timely adjustment of environmental protection of the rectification value, in order to prevent the rectification value is too small, frequent tripping, affecting the quality of the enterprise power supply services, or rectification value is too large, so that the line and equipment management can not be without an effective protection.

Four. Overload delay protection means that the load current exceeds the limit of the equipment, there is a danger of burning equipment, the protection device can cut off the power within a certain period of time. Overloads have a part of the process where heat can build up and the protection technology does not need to act too quickly. The protection should not act on short-term overcurrents.

5. Isolation management system to carry out the function, is required after the plastic case circuit breaker disconnected leakage current does not cause serious harm to the person and equipment technology can be affected through. After several short-circuit trips, the control performance of the switch will decline and the leakage current will increase.

Compared with electronic leakage protection devices, leakage protection devices are small in size, high in precision and sensitivity, but less resistant to interference.

The universal intelligent terminal carries a rectified leakage current of 30mA for the switch and a rectified value of 300mA for the upper branch through the switch. short-circuit protection cannot effectively cut off arcing short circuits with high fire hazards, while leaky moulded-case circuit breakers can reliably cut off earth faults and prevent electrocution and associated earth short-circuit faults from occurring.