Biến dòng đo lường thứ tự không Shanghai Huatong LJZ-Φ65, LJZ-Φ75, LJZ-Φ110, LJZ-Φ150 10KV

• Brand: Shanghai Huatong Transformer
• Model: LJZ-Φ65

LJZ-Φ65, Φ75, Φ110, Φ150 zero sequence current transformer

LJZ-Φ65, Φ75, Φ110, Φ150 zero-sequence current transformers are indoor products with pouring insulation and small volume. They are used for grounding protection of three-phase cable lead wires of generators, motors, etc. (the outer diameter does not exceed 65mm).

Principle of action

Zero sequence current protection is generally suitable for use in TN grounding systems. Because when one phase is grounded, the Id loop impedance of the TN-S system includes the phase impedance Z1, the PE line impedance ZPE and the contact impedance Zf, that is, Zs=Z1+ZPE+Zf; for the TN-C system, the Id loop impedance Including phase line impedance Z1, PEN line impedance ZPEN and contact resistance Zf, namely ZS=Z1+ZPEN+Zf; for TN-CS system, Id loop impedance includes phase line impedance Z1, PEN line impedance ZPEN, PE line impedance ZPE and contact The resistance Zf, namely ZS=Z1+ZPEN+ZPE+Zf, produces a single-phase ground fault current Id=220/ZS, which is obviously greater than the three-phase unbalanced current when there is no fault. As long as the setting is appropriate, the ground fault can be detected The zero sequence current at the time to cut off the fault circuit. For IT systems, it is generally used in industrial and mining enterprises that have high requirements for power supply reliability, and it is not necessary to immediately cut off the power supply circuit for single-phase grounding, but need to issue insulation damage monitoring signals to maintain power supply for a period of time. The three-phase three-wire distribution line of the neutral line. When a single phase is grounded, the zero sequence current flowing on the fault line is the sum of the non-fault system capacitance current of the whole system, so it is easy to detect the ground fault current, so the zero sequence current protection device can be used to monitor the first ground fault relative to the ground . The TT grounding system is often used in the three-phase four-wire power distribution system of industrial and agricultural, civil buildings, lighting, and power hybrid power supply. It is often found that the three-phase unbalanced current is large. When one phase is grounded, the Id loop impedance includes the phase Line impedance Z1, PE line impedance ZPE, load-side grounding resistance RA and power-side grounding resistance RB, contact impedance Zf, namely ZS=Z1+ZPE+RA+RB+Zf, ground fault current Id=220/ZS, due to RA+ RB>>Z1+ZPE+Zf, and RA+RB values ​​are generally large, it is obvious that the fault loop impedance of the TT system is large, and the single-connection fault current Id generated is much smaller than the unbalanced current, and it is difficult to detect the fault Current, so it is not suitable for TT grounding system.

The installation dimensions of LJZ-Φ65, Φ75, Φ110, Φ150 zero sequence current transformer are as follows