Inverter generates harmonic control measures

1, quarantine measures

The main cable faults are:

1. Overload operation. Long-term overload operation will increase the cable temperature and insulation aging, resulting in breakdown insulation and lower construction quality.

2. Electrical aspects: The cable head construction process fails to meet the requirements, and the cable head is poorly sealed. Moisture intrudes into the cable interior and the cable insulation performance deteriorates. When the cable is laid, no protective measures are taken, the protective layer is damaged, and the insulation is reduced.

3, civil engineering aspects: well pipe trench drainage is not smooth, long-term cable is soaked in water, damage the dielectric strength; well is too small, the cable bending radius is not enough, long-term damage by the external force of the extrusion, mainly in the municipal construction of mechanical brutal construction, Dig out and cut the cable.

4. Corrosion. The protective layer is subject to chemical corrosion or cable corrosion for a long time, resulting in failure of the protective layer and reduced insulation.

5, the cable itself or the poor quality of the cable head accessories, poor cable head seal, insulation adhesive dissolved, cracking, leading to the resonance phenomenon of the station for the line disconnection fault line phase capacitance and ground capacitance and distribution transformer excitation inductance form a resonance Loops, which excite ferromagnetic resonances.

Breakage failure causes resonance damage

Breaking resonance Under severe conditions, the high frequency is superimposed with the fundamental frequency resonance, which can make the overvoltage amplitude reach 2.5 times of the phase voltage [P], which may cause the neutral point of the system to move, and the winding and the wire may overvoltage. Insulation flashover, lightning arrester explosion, and electrical equipment damage. In some cases, the phase sequence of the load transformer may reverse, and overvoltage may also be transmitted to the low voltage side of the transformer, causing damage.

Measures to prevent overvoltage and disconnection from resonance

The main measures to prevent overvoltage and disconnection overvoltage are:

1. Do not use fuses to avoid non-full-phase operation;

2. Strengthen the inspection and maintenance of the circuit to prevent the occurrence of disconnection;

3, do not hang the transformer long-term on the line;

4, using ring or dual power supply;

5. The phase-to-phase capacitance is added on the transformer side. The principle is: the capacitor is used as the energy-absorbing element to absorb the energy in the transient process, thereby reducing the impact disturbance intensity to suppress the occurrence of resonance. S (o + 3C,,) 1C. Adding the interphase capacitance ΔC to the transformer side increases the value of 8-[Co+3(C U+ A0)/Ca], thereby increasing the capacitance required for the equivalent capacitor C and the equivalent electromotive force Eo.