Views: 245 Author: Site Editor Publish Time: 2020-12-31 Origin: Site
When a part of the current-carrying conductor contacts or contacts another wire or part of the circuit, a short circuit occurs, which makes the current flow with less resistance. In short, an electronic short circuit is a low resistance connection between two conductors supplying power to any circuit. In the power system, this will lead to the excessive current flowing through the low resistance path, and even lead to the power supply being destroyed, causing more heat and fire. This is why we need to conduct a comprehensive short-circuit study and use corresponding protective devices against electric wire short circuit currents in the power system.
Next, we should consider the lethality of short-circuit current and why it is dangerous to people working nearby or to power system equipment.
Under normal conditions, the current flowing in the power system is the rated current of the equipment or device to be operated.
For normal rated current and surge current (4 to 6 times of the normal rated current when the motor and other devices are started), the protection device does not work. In the case of lightning and arc short circuits, please let our protective device work. The short circuit current can be very large because it allows the current to flow where it should not normally flow. If the abnormally high fault current exceeds the capacity of the protection device (fuse, circuit breaker, relay), it will lead to a large and rapid release of energy in the form of heat and strong magnetic field, and may even cause an explosion called an arc explosion. High temperatures can damage or damage line insulation and electrical components. The shock wave generated by arc explosion may carry vaporized or melted metal, which can be fatal to people without protective measures nearby.
In order to correctly select the type of protection device, interruption rating and trip characteristics, fault current calculations must be carried out. In addition, it is necessary to use the calculation results of distribution boards, distribution boards and distribution boards to determine the current rating of distribution boards and distribution boards. It is necessary to calculate the total contribution of the synchronous motor to the maximum possible load when all synchronous motors are in parallel. Reliable electric wire fault passage indicators and line fault indicators are also necessary to help detect short circuits in the circuit.
We have discussed the basics of short circuit research. Now, we will consider why short circuit analysis is the main requirement of power system protection. In short, short circuit research is very important in power systems. In addition, as a prerequisite for arc flash studies, we cannot conduct arc flash studies without short circuit analysis, which is a recommended practice in any power system industry. NFPA 70E 2018 (workplace electrical safety standard) also recommends at least every 5 years or at the facility. Check out our short article arc flash research and its importance to keep pace with the speed base! A short circuit analysis is required to ensure that the rating of existing and new equipment is adequate to withstand the available short circuit current at various points in the power system. At the same time, we also need accurate electric wire fault passage indicators and accurate electric wire fault indicator monitoring systems to help us detect short circuits.
In order to correctly understand the importance of short circuit research, we divide it into several key points. First, the short-circuit study is used to determine the available fault current or short-circuit current at each point in the system. On this basis, power system engineers can easily determine the required breaking capacity of circuit breakers, which is the basis for designing appropriate relay protection systems, such as accurate cable fault indicator monitoring system and advanced cable fault indicator monitoring system. Also, short circuit analysis will help to protect personnel and equipment by determining the appropriate interruption rating of protective devices (circuit breakers and fuses). In addition, the results of the short circuit study are used to predict the accident energy level and complete the detailed coordination study of protection devices.
In short, our goal is to interrupt the fault current as soon as possible, which can be achieved by setting protection devices, such as earthing and short circuiting device or safety earthing and short-circuit kit. If the electrical fault current exceeds the interruption rating or SCCR (short circuit current rating) of the protection device, the consequences can be devastating. It may pose a serious threat to human life, and may cause personal injury and large-scale equipment damage. In medium and high voltage systems, short circuit analysis is required to determine switchgear ratings and relay settings. No substation equipment can be installed without knowing the short circuit value of the whole distribution system. Short circuit calculations must be maintained and regularly updated to protect the life of equipment and personnel. It is not safe to assume that the new equipment is rated correctly!
Short circuit calculations must be maintained and regularly updated to protect the life of equipment and personnel. It is not safe to assume that the new equipment is rated correctly!