How to prevent open circuit in molded-case current transformers? How to check the wiring?
2022-11-29
Cast resin current transformer How to prevent an open circuit? Regarding this issue, the cast resin current transformer manufacturer reminds you that when using this type of product, you need to comply with the electrical safety regulations to understand the need for grounding on the secondary side. The main purpose of this is to prevent high voltage from the primary side from entering the secondary side, thus causing harm to equipment and personnel.
When using a cast resin current transformer, if a secondary open circuit fault occurs, a reasonable solution should be adopted. The specific solution is to first cut off the high-voltage side and then restore the open circuit point to the normal circuit state. However, this method also has a problem, which is that it causes unplanned power outages.
There is also a non-conventional processing scheme, specifically:
When the cast resin current transformer is open-circuited, the open circuit point will discharge relatively easily. In addition, a metal wire can be used for processing. The wire diameter should meet the secondary current requirements of the cast resin current transformer. Connect one end of the wire to the grounding end of the open-circuit coil, and connect the other end of the wire to a fixed connection point far away from the open-circuit point using an insulated tool. The purpose of this is to short-circuit the open-circuit point.
To avoid accidents, it should be done by professional technicians. Prevention of open circuit in the secondary circuit of cast resin current transformer:
(1) Fuse and other short-circuit protection devices cannot be installed in the secondary circuit;
(2) The secondary circuit is not allowed to be closed. If switching is required, effective measures should be taken to prevent disconnection;
(3) Relay protection and measuring instruments cannot share one cast resin current transformer. If necessary, a converter needs to be connected between the measuring instruments;
(4) For cast resin current transformers that have been installed but not put into use, their terminals should be short-circuited and grounded;
(5) When selecting the secondary circuit terminals, select the test terminals;
(6) The mechanical strength of the secondary circuit connecting wires should be ensured.
The following are the inspection methods for the wiring of the cast resin current transformer:
1. To check whether the secondary side is disconnected or short-circuited, disconnect the wires connected to the A-phase voltage terminal and the C-phase voltage terminal of the electricity meter. Under normal circumstances, the dial of the electricity meter should be rotating.
If the electricity meter dial does not rotate after the A-phase voltage is cut off, it indicates that the C-phase of the current transformer is disconnected or short-circuited. Conversely, if the electricity meter dial does not rotate after the C-phase voltage is cut off, it indicates that the A-phase of the current transformer is disconnected or short-circuited.
2. How to determine whether the current transformer is connected in reverse? The current can be distinguished by connecting an ammeter to the secondary side of the cast resin current transformer to detect the current. If it is a star connection, the current of the middle phase is twice the current of the other phases.
3. Distinguishing Cast resin current transformer Whether the grounding is good can be accurately detected with an ammeter. During the detection process, one side of the ammeter needs to be connected to the terminal of the voltage transformer without a grounding device, and the other side to the secondary line of the cast resin current transformer. If there is a grounding device, the current of the ammeter is 100V, otherwise it is 0.
4. If you want to verify whether the grounding device is appropriate, you can also use the current to verify it. The method is to connect one end of the ammeter to the grounding device, and the other end of the wire to the electricity meter. If the terminals are connected correctly, the ammeter will not indicate.
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