Fast switch-based fast current-limiting circuit adopting forced zero-cross principle

Abstract

The invention relates to a fast switch-based fast current-limiting circuit adopting a forced zero-cross principle. The fast current-limiting circuit comprises a system main loop, wherein an isolationswitch K1, a fast vacuum circuit breaker S1, a saturated inductor L1 and an isolation switch K2 are connected in series in sequence so as to form the system main loop, an absorption capacitor C1 and an absorption resistor R1 are connected in series so as to form a resistor-capacitor absorption circuit and then the resistor-capacitor absorption circuit is connected between fractures of the fast vacuum circuit breaker S1 in parallel, two ends of the fast vacuum circuit breaker S1 and the saturated inductor L1 are separately connected with a current-limiting reactor L3 and a zinc oxide resistor M1 in parallel, a converter capacitor C2, a converter inductor L2, a spark gap G and a high voltage fuse F1 are connected in series so as to form a forced zero-cross loop and then the forced zero-crossloop is connected between two ends of the fast vacuum circuit breaker S1 and the saturated inductor L1 in parallel, and two ends of the converter capacitor C2 are connected with an absorption resistor R2 and a transformer energy storage loop in parallel. The fast current-limiting circuit has the beneficial effects of better limiting fault current, resisting higher current impact, guaranteeing circuit security, and lowering the harm of a short circuit fault to the power system.

Description

technical field [0001] The invention relates to the technical field of protection circuits, in particular to a fast current-limiting circuit based on the principle of forced zero-crossing based on fast switches. Background technique [0002] Short-circuit faults are one of the most common faults in power systems. After a short-circuit fault occurs, a strong short-circuit current will be generated in the circuit, which will cause great harm to the equipment and lines in the power system. Effective control of short-circuit current is an urgent and difficult problem to overcome. In the relay protection system of my country's power system, the circuit breaker is used as the main executive component to cut off the short-circuit fault. When a short-circuit fault occurs in the power system, the secondary protection device makes a logical judgment and issues a corresponding circuit breaker action command, and the circuit breaker is opened. Cut off the fault current and reduce the h...

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Problems solved by technology

[0003] 1. With the expansion of the enterprise, the density of the power grid continues to increase, and the level of fault current also increases accordingly. However, the breaking capacity of the circuit breaker is indeed limited. The maximum breaking level of the circuit breaker currently in use is only about 63KA. Research and development High-voltage circuit breakers with higher breaking capacity have many technical problems, which cannot be overcome in a short time

[0004] 2. At present, ordinary mechanical circuit breakers have a long inherent opening time, generally more than 40ms. It usually takes more than 60ms from the occurrence of a short-circuit fault to the short-circuit current cut-off to complete arc extinction. During this period, the system needs to withstand more than the rated current More than ten times the current impact, it is likely to cause damage to electrical equipment, power system paralysis and other serious accidents

[0005] 3. At present, the time for the secondary protection device to judge the short-circuit fault in the power system generally exceeds 20ms. Even if the opening time of the circuit breaker is very short, it is impossible to avoid the impact of the short-circuit current on the power equipment. It is also very necessary to develop a new algorithm for fast detection of short-circuit faults

[0006] 4. At present, the inherent opening time of the fast vacuum circuit breaker can be controlled within 3.5ms, plus the short-circuit current detection and judgment time, so it can be controlled within 6ms from the occurrence of the fault to the complete removal of the fault. Intrinsic characteristics, at least half of the fault cycle is required to completely remove the fault

After a short-circuit fault occurs in the power system, due to the influence of the DC attenuation component, the impact of the first half-wave current is the largest, and the damage to the power equipment is the most serious. Therefore, the fast vacuum circuit breaker cannot completely avoid the impact of the short-circuit current on the power equipment.

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