1. The inspection basis for whether the current transformer is damaged:
1. The basis for checking whether the polarity is damaged:
The primary winding of the current transformer is marked P1 and P2, and the secondary winding is marked as S1 and S2. If P1 and S1 are the same name, then this sign is called reduced polarity. The primary current enters from P1 and the secondary current comes out from S1. Polarity checking is simple, and in addition to being able to be done on a transformer calibrator, the DC inspection method can also be used.
2. The inspection basis of whether to demagnetize:
Current transformerIn the case of a sudden drop in current, the transformer core may generate remanence. For example, the current transformer suddenly cuts off the power supply in the case of high current, and the secondary winding suddenly opens the circuit. The core of the transformer has remanence, which reduces the permeability of the core and affects the performance of the transformer. The transformer should be demagnetized after long-term use. The transformer should also be demagnetized before inspection.
Demagnetization is to give the iron core an alternating magnetic field through the primary or secondary winding with alternating excitation current. The alternating magnetic field (excitation current) is gradually increased from 0 to saturate the core, and then the excitation current is slowly reduced to zero to eliminate remanence.
2. The basis for checking whether the current transformer measurement is accurate:
The error test of the transformer is generally compared with the standard transformer, and the difference between the secondary current of the two transformers is the error of the transformer under test. This test method is called the comparative method.
The standard transformer is required to be two levels higher than the transformer under test, and the error of the standard transformer is negligible. If the standard transformer is only one level higher than the transformer under test, the error of the test result should be considered plus the error of the standard transformer.
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