◆product overview

AT-CTB current transformer (CT) is widely used for primary measurement and control in power systems. During normal operation, the secondary side of the current transformer is in an approximately short-circuit state, and the output voltage is very low. If the secondary winding is open during operation, or if an abnormal current flows through the primary winding (such as lightning current, resonant overcurrent, capacitor charging current, inductor starting current, etc.), it will generate thousands or even tens of thousands of volts of overvoltage on the secondary side. This not only poses a threat to the insulation of the secondary system, but also causes the transformer to overheat and burn out, and even endangers the safety of workers. The use of AT-CTB series current transformer overvoltage protectors can effectively prevent accidents caused by secondary open circuits of current transformers.◆
Main purpose


The AT-CTB current transformer overvoltage protector is mainly used for abnormal overvoltage protection on the secondary side of various CTs. The protector is connected to both ends of the secondary winding, and during normal operation, the leakage current is extremely small, resulting in a high resistance state. When an abnormal overvoltage occurs, the protector quickly acts and short circuits, and the panel displays the faulty area with passive signal output. After the fault is eliminated and the circuit is restored to its original state, it can be reset and put back into normal operation.

Protectors are applied to differential windings, overcurrent windings, measuring windings, busbar protection windings, and backup windings on the secondary side of CT.◆ Model Description
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TECHNICAL INDEX
1. Normal leakage current: ≤ 5 μ A;
2. Conducting voltage Uc: 150V ± 10%;
3. Conduction time Ts: 50ms ≤ Ts ≤ 250ms;
4. Remote signaling relay contact capacity: AC220V/5A;
5. Protective relay contact capacity: AC220V/10A;
6. CT specifications used: secondary peak value greater than 150V;
7. Protection current: ≥ 5A;
8. Working environment: Temperature: -20 ℃~70 ℃, humidity: ≤ 95% RH
9. Reset method: manual button "reset"; Automatic 'reset' (optional);
10. Seismic performance: 10-10-10Hz 2g 3min
11. Anti interference: 4.4KV/M³12. Dimensions: (see Figure 1 and Figure 2)
AT-CTB-1：48×48×100（mm³）(Single winding)
AT-CTB-X：144×89×73（mm
）(2-6 windings)
13. Voltage withstand: 2kV, 50Hz, 1min

14. Working power supply: AC220V ± 15%, 50Hz/60Hz or DC220V/110V;15. Installation method: panel type, rail type or fixed installation
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major function
1. During normal operation, the leakage current flowing into the protector does not exceed 20 μ A and does not affect the normal operation of the CT.
2. When the voltage across A (or B, C), N exceeds 150V, AT-CTB short circuits A (or B, C), N.
3. The contact capacity of the relay is greater than 6A, so in the event of a fault, it can reliably short-circuit the CT secondary side.
4. The relay contacts have a holding function, and the protection can only be released by pressing the "reset" button.
5. If the fault is resolved during a power outage, the device will automatically reset after the power is lost.

6. The device provides a pair of normally open contacts COM, CK and a pair of normally closed contacts COM, CB, which can be connected to various sound and light alarms or provided to the comprehensive protection device for remote information transmission. When the protective action is taken, oftenOpen and close, normally closed and open.



◆Outline dimension diagram