The Dong Hung Electric Equipment Company in Hanoi has successfully developed MOV-ZnO ceramic with excellent nonlinear characteristics, which is used as a 35 kV lightning arrester, effectively replacing the conventional V-SiC materials.
Vietnam is a tropical country with high humidity and one of the highest lightning densities in the world. When lightning strikes, overvoltage can cause incidents in the electrical grid. Therefore, lightning arresters are essential safety devices for electrical networks.
Mr. Nguyen Cao Thinh, the project leader, stated that conventional lightning arresters are made from V-SiC materials, which have low resistance and high leakage current. When functioning as a lightning arrester, they require a gap, making them susceptible to damage from high current that can lead to fires or explosions.
MOV-ZnO is a complex oxide ceramic material primarily composed of ZnO (over 90%) along with other additives. The nonlinear properties of MOV-ZnO are significantly better, with a nonlinear coefficient many times greater than that of V-SiC. Therefore, using MOV-ZnO for 35 kV lightning arresters enhances the capability to absorb overvoltage energy per unit volume, and the response time to cut the overvoltage amplitude is greatly reduced. Additionally, MOV-ZnO does not cause voltage spikes, unlike lightning arresters with gaps using V-SiC.
Due to its excellent technical properties, this new material allows for considerable size reduction of lightning arresters, including utility poles and mounts, thus reducing transportation and maintenance costs. Mr. Thinh noted that if a lightning arrester made from V-SiC weighs 70 kilograms, the ceramic-cased product only weighs 8 kg. The cost of this product is also only 65-70% that of foreign equipment while maintaining equivalent quality.
The material has been used at power stations in Ha Nam, Thai Nguyen, and Hung Yen, ensuring good quality. The research team will continue to develop lightning arresters with higher voltage ratings of 110 – 220 kV.
This product won third place at the Vietnam Science and Technology Innovation Award in 2005.
Anh Thi
