Is It Better For A Surge Protector To Have A Smaller Leakage Current? Is There An Spd With 0 Leakage Current?
The surge protectors that we often use, which are composed of varistors, all have leakage current problems. Generally speaking, the larger the leakage current of the surge protection device, the more likely it is to cause self-heating, deterioration, and shorten the service life of the surge protector. In severe cases, it may cause explosions and serious safety accidents.
1. Surge protector leakage current
The leakage current of the surge protective device refers to the current in the microampere order of magnitude that passes through the varistor when a certain voltage is applied to both ends of the varistor under normal circumstances. It is the current generated by applying a voltage value of 70% of the rated varistor voltage to both ends of the varistor, that is, the leakage current index of the varistor, and generally requires a static leakage current of I≤20μA.
The leakage current of the surge protector is continuous, but as long as it is within the allowable range on a line, it will not cause damage to the line and protection equipment.
2. The stability of leakage current is very important when selecting a surge protector
When selecting a surge protector, its leakage current characteristic must be fully considered. Generally, the leakage current value of the surge protector is required to be within a certain range, and it is not allowed to automatically increase during operation. Once the leakage current is found to increase automatically, it should be eliminated immediately, because the instability of the leakage current is the direct cause of the accelerated aging and explosion of the surge protector. At present, there are two different batching methods and production processes in terms of varistor manufacturing process:
1. The initial leakage current index of the varistor produced by one process is low, only 3~6μA, but once it enters the use link, it will increase year by year as the use time of the surge protector increases, and it will be in an unstable state for a long time, causing the surge protector to overheat, age, and fail, and may also cause fires.
2. The varistor manufactured by another production process has a large leakage current of 20~30μA, but it is in a stable state for a long time and will not gradually increase with the use time of the surge protector, ensuring the stability of the line leakage current and will not cause rapid degradation and failure of the surge protector.
3. Surge protector leakage current detection is a necessary item for lightning protection detection
In order to ensure whether the surge protector put into use has deteriorated or failed, the routine lightning protection detection carried out by the lightning protection device user unit every year will conduct detailed tests on the leakage current index of the surge protector.
When measuring I1 mA for the first time, the measured value of the leakage current Iic of the SPD composed of a single MOV should not exceed the maximum value of Iic specified by the manufacturer; if the manufacturer does not claim the leakage current Iic, the measured value should not be greater than 20μA. For SPDs with multiple MOVs in parallel, the measured value of the leakage current Iic should not exceed the maximum value of Iic specified by the manufacturer: if the manufacturer does not claim the leakage current Iic, the measured value should not be greater than 20μA multiplied by the number of MOV valves. When the number of valve plates cannot be determined, the actual measured value of the SPD shall not exceed 20μA;
When the I1 mA is measured later, the actual measured value of the leakage current Iic of the SPD composed of a single MOV and multiple MOVs shall not be greater than 1 times the first measured value.
