Fuse IEC127 standard defines it as "fuse link " It is a kind of electrical components installed in the circuit to ensure the safe operation of the circuit. Fuse widely used in high and low voltage power distribution systems and control systems, as well as electrical equipment, as a short circuit and over-current protection device, is one of the most widely used protection devices.
Fuse is an over-current protection appliances. Mainly by the fuse fuse and fuse two parts and filler plus other components. When used, the fuses are connected in series with the circuit to be protected. When the current of the circuit to be protected exceeds the specified value and the heat generated by the melt itself blows off the melt after a certain period of time, the circuit is disconnected and protected .
An appliance used to protect electrical equipment from high transient overvoltages and to limit the freewheeling time constant. The main material is zinc oxide. The lightning arrester is usually connected between the mains lead and the ground, but sometimes it is connected to the side of the mains or between the leads. Surge arresters are sometimes referred to as overvoltage protectors, surge divider.
Surge arresters are devices in which substations are protected from lightning strikes.
When the lightning impulse transmitted into the substation along the line exceeds the protection level of the arrester, the arrester discharges first and the lightning current is safely introduced into the earth through a good conductor. The grounding voltage is limited to the lightning impulse level of the protected equipment Electrical equipment is protected.
According to the arrester can be divided into its development:
① protection gap - is the most simple form of arrester;
② tube surge arrester - is also a protective gap, but it can extinguish itself after discharge;
③ valve arrester - is a single discharge gap is divided into many short series of gaps, while increasing the nonlinear resistance, improved protection performance;
④ magnetic arrester - the use of the magnetic spark gap, improve the ability of arc suppression, but also has the ability to limit the internal over-voltage;
⑤ zinc oxide surge arresters - the use of zinc oxide valve ideal volt-ampere characteristics (non-linear high, that is, low voltage resistance at high voltage characteristics, limiting the arrester on the voltage at normal frequency showed high resistance characteristics ), With no gap, no freewheeling residual voltage advantages, but also limit the internal over-voltage, is widely used.