132HC Mast Section Hidden danger of power line of tower crane
The tower crane equipment is equipped with electrical protection device, which can reduce the hidden danger to the greatest extent. However, the field staff should also have certain common sense to know which conditions will cause resistance in the grounding and neutral line of the tower crane equipment, and how to solve and avoid these problems. Engineering equipment has its own many characteristics, only a certain amount of specific knowledge can better comply with these natural laws to protect their own safety.
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1. In the three-phase four wire system, some people adopt the repeated grounding to improve the reliability; if a single grounding is adopted, when the tower crane metal structure leaks electricity, the current returns to the power supply through the tower crane grounding resistance and the neutral wire grounding resistance. Because the two grounding resistance values are basically the same, the partial voltage is basically the same, so there is one 220V on the tower crane grounding resistance Half of the voltage, because the current is not large, the voltage can exist for a long time. If a person standing on the wet ground contacts the leakage tower body, he or she will wait for the grounding resistance of the tower crane to bear the similar voltage in parallel, which may cause electric shock.
2. Although protective neutral connection measures can play a protective role, there are still hidden dangers: in the three-phase four wire system neutral line grounded power grid, tower crane adopts the protective measures of metal structure connecting the working zero line. When the metal structure leaks electricity, the leakage current directly returns to the zero line, forming a phase zero short circuit. Because the line resistance is small and the current is large, the safety device on the leakage line will be disconnected soon, so the leakage power supply will be cut off and the protection function will be played. However, due to the current flowing through the working zero line when the power consumption is unbalanced, and there is a certain resistance on the zero line, a certain voltage can be generated on the zero line. When the metal shell of the equipment is connected to zero, a certain voltage will also be generated, and at the same time, a potential safety hazard will be caused.
To sum up, in the same power grid, it is not allowed to connect some equipment to neutral or some equipment to ground. Because when the earth equipment leaks electricity, the zero line also produces voltage to the earth, all the earth equipment will be electrified, causing a wider range of security risks.
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