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Harm and control method of short circuit current in power system

          In recent years, the state attaches great importance to energy-saving emission reduction, more and more enterprises to carry out energy-saving emission reduction. Such as steel companies, the new small generating units access distribution network, the power supply system for short-circuit current changes. So what is the short circuit current for power distribution system, how did it happen? 

          The short-circuit current of the power supply and distribution system is when the three-phase or two-phase short circuit occurs in the power distribution system, the power supply system will generate a large current, which may easily damage the electrical equipment and components. Short circuit current is mainly generated by the power supply equipment and motors, such as power supply systems, generators, synchronous motors, asynchronous motors.

How to prevent the harm caused by short circuit current? 

          In the design and selection of circuit breakers (switches), busbars, current transformers, cables and computer protection devices and other electrical equipment, to consider these devices in the short circuit, can quickly and reliably the point of failure Cut, and protect the equipment from failure when not damaged. And the engineering design unit in the initial design, must be based on the short-circuit current in the power system to calculate the maximum and minimum short-circuit current for each point in the power distribution system. According to the maximum short circuit current selection circuit breakers, current transformers, cables and other equipment, the minimum short-circuit current to verify the sensitivity of computer protection. 

          If the maximum short-circuit current in power supply and distribution system increases a lot, exceeding the breaking capacity or thermal stability of the original circuit breakers, current transformers, cables, etc., there is a potential safety hazard for these devices. A short circuit may cause the circuit breaker to explode, etc. ACCIDENT.

Computer protection in the short circuit current distribution system for the role? 

          Microcomputer protection In the system of three-phase short circuit, two-phase short circuit or electrical equipment internal fault, the fault can be quickly removed to ensure that other power supply equipment and electrical equipment is not damaged, as well as non-fault power supply system for normal operation . 

          The configuration of the microcomputer protection device is designed by design institutes, complete plants and other units. The protection scheme is selected according to the parameters of the equipment to be protected and the short-circuit current for the power distribution system. If the system is connected to the generator, the protection device for the distribution network must be redesigned. 

          For example, when the generator is connected to the distribution line, the power supply of the tie line is bidirectional. Due to different short-circuit points, the short-circuit current flowing through the circuit breakers on both sides of the tie line is different, and the protection of the circuit breakers on both sides of the tie line must also be bidirectional. However, in the actual power distribution design, it is easy to ignore the protection of power plants outside the device. At this moment, if the connecting line fails, the relay protection device will not move or cause serious damage such as equipment damage.

What happens when the short circuit current of the power distribution system changes? 

          When the short circuit current of power supply and distribution system changes, it is necessary to re-check the protection of distribution network, if necessary, need to be recalculated. 

          If a steel company, the system short-circuit capacity changes without the timely adjustment of the relay protection of the original equipment, resulting in the relay protection refused to move or malfunction; in the new project only concerned about the new project relay protection calculation, and ignore the upper and lower Level for the power distribution system with, it is easy to cause failure when the trip more jump, the accident may be further expanded.

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