I. Overview:
UNT-LJK series high-precision zero-sequence current transformer adopts ABS engineering plastic shell and all-resin casting to be fully sealed. The use of insulating oil refrigeration cutting process effectively avoids corrosion of the transformer during long-term use. Good insulation performance and beautiful appearance. It has the characteristics of high sensitivity, good linearity, reliable operation and convenient installation. Its performance is superior to the general zero-sequence current transformer, and it can be used in a wide range of applications. It is not only suitable for electromagnetic relay protection, but also suitable for electronic and microcomputer protection devices, and is matched with other products of the company to ensure the accuracy and reliability of protection. .

2.Product development purposes:
For the small current grounding system, the zero sequence power direction criterion is adopted, which requires the system to input not only the zero sequence current but also the zero sequence voltage. At this time, the external zero-sequence transformer can adopt the zero-sequence CT matched with the small current grounding line selection device on the general market. (In this case, the zero-sequence CT ratio is not marked, and the ratio is about 40:1)

However, in the low-voltage system, many people still use this method, and do not consider the change of the grounding method. Most of the low voltage systems use high current grounding systems. Since the neutral line is directly grounded, when single-phase grounding occurs, the grounding current mainly depends on the single-phase short-circuit current of the circuit. At this time, it is required to act on the comprehensive protection device to trip, but the difference in the unbalanced current of the circuit is large, and the comprehensive protection device The different rated input of the tripping action will cause the misoperation and rejection of the integrated protection device. Therefore, it is necessary to configure a suitable zero-sequence current transformer for the protection device and select an appropriate ratio to ensure the accuracy and reliability of the operation of the integrated protection device. .

Taking into account the above factors, the company specially designed and developed a high-precision zero-sequence current transformer for the low-voltage and high-current system, which is matched with the grounding protection of the comprehensive protection device. It has been proved by engineering practice that the precision of the protection action is greatly improved. reliability.

3. The device features:
· Compared with traditional current and voltage transformers
· Small size, light weight and low price
·High sensitivity, high precision, good linearity, wide dynamic range, true wave shape transmission
·High overload capacity and high isolation strength (greater than 2.5KV/min)
·The primary of the current transformer can be designed as a
· Divided into integral and open installation, easy to use
· Accurate conversion and measurement of current quantity
·Supporting high and low pressure control devices to ensure the reliability and accuracy of protection actions

4.The use of the environment and conditions:
Ambient temperature: -10 ° C ~ 40 ° C
Atmospheric pressure: 80～110KPa
Relative humidity of air: 90% (25 ° C), 50% (40 ° C)

5. Product categories and main data:
Voltage 0.38KV ~ 66KV
Grid frequency 50Hz
The same name end is penetrated by the "L1" side once and the second time is "K1"

6.Installation:
The integral transformer installation should be carried out before laying the cable, and the cable will pass through the transformer when it is laid.
Open-type transformers are not limited by cable laying, as follows:
(1) .Remove the joint compression piece of the transformer "K1ˊ" and "K2ˊ"
(2). Loosen and remove the two hexagon socket bolts on the top of the transformer. The transformer is divided into two parts.
(3). Put the transformer on the cable, wipe the contact surface clean, apply a layer of anti-rust oil thinly, and tie the two parts of the transformer. Then, screw the hexagon socket bolts. The two parts of the transformer should be aligned to avoid affecting performance. .
(4). Fix the gusset on "K1ˊ" and "K2ˊ"
(5). If the inner hole>120mm transformer is installed horizontally, please add non-magnetic bracket.

7. The instructions required for ordering:
·One zero sequence current, secondary zero sequence current
·Inner hole diameter
·Secondary load capacity or load impedance