The Detection and the Open Circuit Fault Inspection of Current Transformers

Ⅰ. The current transformers detection

The current transformers play the role of current conversion and electrical isolation. It is convenient for the secondary instrument measurement to be converted into a relatively uniform current to avoid the risk of directly measuring the current transformer line. The detection methods of current transformers are as follows:

1. Transformer comprehensive tester: Measure the error between the standard current transformer and the tested transformer, and display the working current.

2. The standard current transformer: It is used as a standard in the verification of current transformers. The accuracy is generally more than two levels higher than the measured one. It is designed with multiple ratio taps to adapt to the verification of different current transformers.

3. The voltage regulator: It is used to adjust the test current. The maintenances and switches are installed in one operation table. There are two voltage regulators for coarse adjustment and fine adjustment to meet the adjustment fineness. When measuring below the rated current of 2500A, it can be made by a combination of 10KVA general-purpose voltage regulators. Larger currents must be specially made, generally 30~60KVA.

4. The current booster: Cooperate with the voltage regulator to match the test current that produces various demands. Its capacity and cost increase with the increase of current.

5. The high-current connection cable: Connect hundreds or thousands of amperes, and the price of the cable cannot be ignored.

6. The load box: Simulate the actual working state of the current transformer under test.

Ⅱ. The open circuit fault inspection of the current transformer

1. The loop meter indication is abnormally low or zero. If the current loop used to measure the meter is open, the indication of the three-phase ammeter will be inconsistent, the indication of the power meter will decrease, the meter will not rotate or the number of revolutions will slow down. If the meter indicates spordically, it may be in a half-open state.

2. The CT body has noise, uneven vibration, serious heat generation, smoke and other phenomena. Moreover, these phenomena are not obvious when the load is small.

3. The CT secondary circuit terminals and component wires of the current transformer have discharge and ignition phenomenas.

4. The bartender device's malfunction or refusal to act. This situation can be detected and dealt with in case of false tripping or overstepping tripping.

5. The electricity meters, relays, etc. smoke and burn out. If the power meter, watt-hour meter, transmitter, and relay installed for protection are burned out, it will not only make the CT secondary open circuit, but also make the PT secondary short circuit.

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