自愈式电容器采用单层聚丙烯膜做为介质，表面蒸镀了一层薄金属作为导电电极。电解电容厂家为您详细介绍下自愈式电容的自愈过程：当施加过高的电压时，聚丙烯膜电弱点被击穿，击穿点阻抗明显降低，流过的电流密度急剧增大，使金属化镀层产生高热，击穿点周围的金属导体迅速蒸发逸散，形成金属镀层空白区，击穿点自动恢复绝缘。
the self-healing capacitor uses a single layer of polypropylene film as the dielectric, and a thin layer of metal is evaporated on the surface as the conductive electrode. when the high voltage is applied, the electric weakness of polypropylene film is broken down, the impedance of breakdown point is obviously reduced, the current density is increased rapidly, which makes the metallized coating produce high heat, the metal conductor around the breakdown point evaporates and dissipates rapidly, forming a metal coating blank area, and the breakdown point automatically recovers the insulation.
1、定电压
constant voltage
电容器额定电压优先值如下0.23，0.4，0.525及0.69kv。电容器额定电压选取一般比电气设备额定运行电压高5%。
the priority values of capacitor rated voltage are as follows: 0.23, 0.4, 0.525 and 0.69kv. the rated voltage of capacitor is generally 5% higher than that of electrical equipment.
2、电容
capacitance
电容器的电容是极板上的电荷相对于极板间电压的比值，该值与极板面积、极板间绝缘厚度和绝缘介质的介电系数有关，其计算式为c=14πε×sd式中ε为极板间绝缘介质的介电系数;s为电容器极板面积;d为电容器绝缘层厚度。
the capacitance of a capacitor is the ratio of the charge on the electrode plate to the voltage between the plates, which is related to the area of the plate, the insulation thickness between the plates and the dielectric coefficient of the insulating medium. the formula is c = 14 π ε × sd, where ε is the dielectric coefficient of the insulating medium between the plates; s is the area of the capacitor plate; d is the thickness of the insulation layer of the capacitor.
静态电容一般投运后第一年电容值下降率应在2%以内，第二年至第五年电容值下降率应在1%～2%，第五年后因电介质老化，电容值将加速下降，当电容值下降至出厂时的85%以下，可认为该电容器寿命期结束。
generally, after the static capacitor is put into operation, the reduction rate of capacitance value in the first year shall be within 2%, and that from the second year to the fifth year shall be between 1% and 2%. after the fifth year, due to dielectric aging, the capacitance value will decrease rapidly. when the capacitance value drops to less than 85% of the original value, the life of the capacitor can be considered to be over.
3、无功功率
reactive power
在交流电路中，无功功率qc=uisinφ由于电容器电介质损耗角极小，φ=90°，所以sinφ=1，则无功功率qc=ui=ωcu2×10-3=2πfcu2×10-3（μf），从该式可见，电容器无功功率不仅取决于电容c，而且还与电源频率f、端电压u直接相关，电容器额定无功功率的准确定义应是标准频率下外接额定电压时静态电容c所对应的无功率。
in ac circuit, the reactive power qc = uisin φ, because the dielectric loss angle of capacitor is very small, φ = 90 °, so sin φ = 1, then reactive power qc = ui = ω cu2 × 10-3 = 2 π fcu2 × 10-3 (μ f). from this formula, it can be seen that the reactive power of capacitor is not only determined by capacitor c, but also directly related to power frequency f and terminal voltage u. the accurate definition of rated reactive power of capacitor should be under standard frequency no power corresponding to static capacitance c when external rated voltage is connected.
当电网电压低于电容器额定电压时，电容器所输出的无功功率将小于标定值。因此如果电容器额定电压选择偏高，电容器实际运行电压长期低于额定值，很可能因电容器无功出力低于设计值造成电网无功短缺。
when the output voltage of the capacitor is lower than the rated voltage of the capacitor. therefore, if the rated voltage of the capacitor is too high and the actual operating voltage of the capacitor is lower than the rated value for a long time, it is likely that the reactive power of the power grid will be short because the reactive power output of the capacitor is lower than the design value.
电容器在外施电压作用下，由于介质中的杂质或气隙等弱点的存在或发展引起介质击穿形成导通电路；接着在导通电路处附近很小范围内的金属层中流过一个前沿很陡的脉冲电流。邻近击穿点处金属层上的电流突然上升，按其离击穿点的距离而成反比分布。在顺时刻t，半径为rt的区域内金属层的温度达到金属的熔点，于是在此范围内的金属熔化并产生电弧。该电流引起电容能量释放，在弧道局部区域温度突然升高，压力突然增大。
under the action of applied voltage, the dielectric breakdown of the capacitor is caused by the existence or development of impurities or air gap in the medium to form a conducting circuit; then a pulse current with a very steep front edge flows through the metal layer within a small range near the conduction circuit. the current on the metal layer near the breakdown point suddenly rises and is inversely proportional to the distance from the breakdown point. at the time t, the temperature of the metal layer in the region with radius rt reaches the melting point of the metal, so the metal in this range melts and generates an arc. the current results in the release of capacitance energy and the sudden increase of temperature and pressure in the local area of arc channel.
随着放电能量的作用，半径为rt的区域内金属层剧烈蒸发并伴随喷溅。在该区域半径增大的过程中电弧被拉断，金属被吹散并受到氧化与冷却，破坏了导电通路，在介质表面形成一个以击穿点为中心的失掉金属层的圆形绝缘区域，电容器的自愈过程结束。
with the effect of discharge energy, the metal layer in the region with radius rt evaporates violently, accompanied by splashing. in the process of increasing the radius of the region, the arc is broken, the metal is blown away and oxidized and cooled, which destroys the conductive path, and forms a circular insulation area with the breakdown point as the center, and the self-healing process of the capacitor ends.