The accuracy level refers to the percentage value of the maximum current error when the primary current is the rated value within the specified secondary load change range. The accuracy levels of current transformers are divided into five levels: 0.2, 0.5, 1.0, 3, and 10.
Current transformers for protection can be divided into two types: steady-state protection (P) and transient protection (TP).
The current transformer for steady-state protection has 5P and 10P accuracy levels.
The accuracy of the current transformer for transient protection is divided into three levels: TPX, TPY, and TPZ.
There is no air gap in the toroidal core of the TPX current transformer, and the current error is not more than ±0.5% under the rated current and load.
The core of TPY current transformer has a small air gap. The length of the air gap is about 0.05% of the average length of the magnetic circuit. Due to the air gap, the core is not easy to saturate, which is conducive to the rapid attenuation of the DC component and allows the maximum current error under the rated load. It is ±1%.
The core of TPZ current transformer has a large air gap, and the length of the air gap is about 0.1% of the average length of the magnetic circuit. Due to the large air gap of the core, it is generally not easy to saturate. It is especially suitable for fast reclosing (no current time gap) Not more than 0.3s) used on the line.