1、 Overview
Current transformers (CT) are widely used in power systems for primary measurement, control, and protection. During normal operation, the secondary side is in a nearly short-circuit state with a very low output voltage. However, if the secondary winding is open or an abnormal current flows through the primary winding (such as lightning current, resonant overcurrent, capacitor charging current, inductor starting current, etc.) during operation, 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 endangers the safety of workers.
The CTB series current transformer secondary overvoltage protector produced by our company is designed for this situation and can effectively prevent accidents caused by CT secondary open circuit.
scope of application
The current transformer secondary overvoltage protector is mainly suitable for the differential winding, overcurrent winding, measurement winding, busbar protection winding, backup winding, etc. on the CT secondary side. It is used to suppress transient overvoltage lower than the equipment's impulse overvoltage, discharge surge energy, and protect the system circuit and equipment.
Normal usage and installation conditions
1. Normal usage conditions
a. Voltage: The voltage continuously applied between the terminals of the overvoltage protector should not exceed its maximum value
Large continuous operating voltage.
b. Environmental temperature for use: - 20 ℃ to 70 ℃.
c. Environmental humidity for use:< 95% RH.
d. Shell protection level: IP20。
e. Pollution level: The pollution level at the installation site is level 2.
2. Installation conditions
a. Installation category: According to the voltage protection level of the overvoltage protector, it is divided into two categories: II and III;
b. Installation location:
Recommended for locations with less exposure;
It should be installed in a place without significant vibration and impact.
3. Installation method: TH35-7.5 steel rails are used for installation.
4. Wiring method: Screw compression wiring.
Technical indicators:

power supply	AC/DC input 100-240V
Normal leakage current IL20V	≤1μA
Input Resistance	＞100M
turn-on voltage	150V ± 10% (can be set according to user requirements)
conducting time	50ms≤Ｔs≤250ms
Protective relay contact capacity	AC220V/5A
Using CT specifications	Secondary peak value greater than 150V
protective current	5A
work environment	Temperature: -20 ℃~+70 ℃ Humidity: ≤ 95%RH
Compound method	Manual button reset
Seismic performance	10-50-10HZ 2g 3min
Reliable and secure	Meets the requirements of IEC834-1
Working power supply	AC220V,50HZ
Power consumption	≤5W
Installation method	railed

2. Appearance and installation dimensions

External dimensions:115*90*40(Length * Width * Depth) (CTB-6) Unit: mm
Installation method: rail installation
The terminal definition is shown in the following figure: （CTB-6)

The terminal definition is shown in the following figure: (CTB-9) External dimensions:145*90*40(Length * Width * Depth) (CTB-9) Unit: mm

The terminal definition is shown in the following figure: (CTB-12) External dimensions:155*110*72(Length * Width * Depth) (CTB-12) Unit: mm

IIInstallation, use and maintenance
This type of protector has a small volume and can be installed on standard guide rails as needed.
a. During installation, insert the overvoltage protector into the installation rail and push the stopper on the overvoltage protector upwards to fix it on the installation rail without loosening or falling off. When it is necessary to remove the overvoltage protector, simply pull down the stopper.
b. Use a diameter not less than 2.5mm²The copper wire connects the A/B/C and COM contacts of CTB to the secondary side of the protected CT, and the connection should be secure.
C . Maintenance methods
Resistance testing method for multimeter:
Before powering on the CTB protector, use a multimeter to measure the resistance between the A1, B1, C1, and corresponding N terminals of each circuit. The resistance value should be greater than several tens of megaohms
The pressure regulation inspection method is as follows:

Set the single-phase voltage regulator to the 0V position, connect the output terminal to a certain winding and the corresponding N terminal (such as 1A and 1N), and turn on the AC220V power supply of the protector. At this time, the working indicator light (green) on the panel flashes every second, while other indicator lights should not be on, indicating that all protection circuits are in a normal reset state. If the red indicator light of a channel is on, it indicates that the corresponding protection status has not been reset properly and needs to be reset by pressing the reset button. Afterwards, check if the action voltage is normal. The method is to slowly adjust the voltage regulator to gradually increase the output voltage of the regulator. When the light bulb is on, the output voltage value of the regulator at this moment is the protection action starting voltage. After reducing the output voltage of the regulator, the light bulb will not turn off, indicating that the function remains normal. According to this method, all windings are tested separately. If they meet the technical specifications, the test is qualified.

4、 Ordering Notice
When placing an order, users need to specify in detail the model specifications, quantity, delivery date, mailing address, telephone number, transportation method, etc. of the ordered product. If the user is unable to determine the required product model specifications, they can provide detailed parameters of the protected CT and related circuit parameters, and our company can design and select on their behalf.
5、 Manufacturer's guarantee
The quality assurance period of this product is one year.