What Is Leakage Current?

There are four types of leakage current: semiconductor element leakage current, power supply leakage current, capacitor leakage current, and filter leakage current.

For safety reasons, the effects of leakage current need to be considered when using passive EMl filters. Most manufacturers define the leakage current of each phase during normal operation. Generally, the rated value of leakage current is not the result of measurement, but the calculated value. The basic contents of leakage current are discussed, including the requirements of the standard for leakage current, the calculation and measurement methods of leakage current for three-phase power supply network and single-phase power supply network, and the influence of the topology of the power supply network on the leakage current. ^[1]

The communication room is a valuable resource for communication operators. The power distribution room provides high reliability and effective guarantee for the communication room. The leakage current is too high, and any residual current circuit breaker connected to the building network will affect the reliable operation of the equipment. These residual current circuit breakers detect the current flowing into the ground wire. Once the current exceeds a certain current limit value, the power supply voltage will be disconnected. Leakage current limit enables reliable equipment operation and ensures that no one is injured even when the ground wire is broken.

Applicable scope of leakage current leakage protector

Generally speaking, leakage protection switches are suitable for civil and industrial electrical equipment, but for some industrial electrical equipment, special high-frequency switching power supplies may not be applicable. For the communication power system, in view of the special performance of the communication high-frequency switching power supply, the following are recommended:

(1) Confirm that there is a good and reliable grounding equipment, it is recommended not to install a leakage protection switch;

(2) It is not recommended to install a leakage protection switch for large-capacity power systems;

(3) Small-capacity power supply system, equipment installed in private houses, it is recommended to install leakage protection switches.

Leakage current requirements for communication power

It should meet the requirements of the maximum leakage current in Table 17 of 5.2.2 in GB4943-1995. When the leakage current is greater than 3.5MA, the leakage current should not exceed 5% of the input current of each phase. If the load is unbalanced, the maximum value of the three phase currents should be used for calculation. The steady-state leakage current of the power module meets the national YD731 standard. The leakage current at 1500VAC does not exceed 30mA, and the leakage current at 220VAC does not exceed 5mA.

Leakage characteristics of leakage current switching power supply

Inside the switching power supply, there is usually a small-capacity high-voltage capacitor for input to ground, output to ground, and input to output. Due to this, there will be a certain leakage current from the AC input to ground, so this leakage current may cause The leakage protection switch installed on the input end of the device cannot operate normally.

Regulation on leakage current of switching power supply

The leakage current of the power supply system is related to the number and model of the modules. The larger the number of modules, the larger the leakage current itself. Therefore, the operating current of the selected leakage protection switch also needs to be larger. In this way, the system will have a fixed leakage current to the ground, so the high-frequency switching power supply system must be reliably grounded according to regulations. When the module works normally, the leakage current to ground varies with the input voltage of the module, and the zero-line voltage drift will increase slightly. In this way, if the system is configured with more than 10 modules, the ground leakage current of the system will be greater than the 20mA current limit value of the general leakage current protection switch, causing the leakage current protection switch protection. Therefore, the front end of the system power distribution cannot be connected to the leakage current protection switch. ^[2]