In the power system, the distribution cabinet is the key hub for power distribution and control, and its leakage protection mechanism is crucial. Once a leakage accident occurs, if it cannot be protected in time and accurately, it will pose a serious threat to personal safety and may also damage expensive electrical equipment. A deep understanding of the leakage protection system of the distribution cabinet is the core point to ensure the safety of electricity use.
Distribution cabinets are usually equipped with leakage protectors, and their core principle is based on residual current detection. When the vector sum of the current flowing in and out of the line is not zero, that is, when leakage occurs, the leakage protector can quickly sense it. Common types are electromagnetic and electronic. Electromagnetic leakage protectors
Rely on electromagnetic force to drive the tripping mechanism, which is fast and reliable, and is not affected by power supply voltage fluctuations; electronic types use electronic components to detect signals, with high sensitivity, and can also realize more additional functions, such as leakage current display.
There are two key parameters: leakage action current and leakage action time. The leakage current refers to the minimum leakage current value that causes the protector to operate. It is generally divided into high sensitivity (such as 30mA and below), medium sensitivity (30mA - 1000mA) and low sensitivity (above 1000mA). In places where people frequently come into contact, such as residential houses and offices, 30mA high-sensitivity protectors are often used, which can quickly cut off the power supply at the moment of leakage to ensure personal safety.
For humid environments, such as basements and bathrooms, the risk of leakage increases due to the decrease in human body resistance. It is advisable to use a protector with a 15mA or even lower operating current to ensure that even a slight leakage can be responded to in time. In industrial environments, if there is a large equipment startup impact current, in order to prevent false operation, the operating current can be appropriately increased to about 100mA, and at the same time, a short delay action (such as 0.1 - 0.2s) can be used to avoid the instantaneous current fluctuation at startup.
The leakage protection in the distribution cabinet needs to be coordinated with the protection of the upper substation and the lower electrical equipment. The upper protection action current value should be greater than the lower protection value to form a hierarchical protection to avoid over-tripping. For example, the upper protection value is set to 300mA, and the lower distribution cabinet is set to 30mA - 100mA according to the scene, to ensure that the fault area is accurately located in the event of local leakage and reduce the scope of power outage.
To ensure that the leakage protection mechanism is continuously effective, regular inspections are required. Use professional testing instruments to simulate leakage signals and verify whether the action current and time meet the standards. At the same time, check whether the appearance of the protector is damaged and whether the wiring is loose to ensure reliable operation at critical moments.
The distribution cabinet leakage protection mechanism is a sophisticated and rigorous system. Reasonable setting of action parameters, selection of protection types, and daily maintenance can fully protect personal and equipment safety and ensure stable power supply.
