27.5kV系列金屬氧化物避雷器（以下簡稱MOA）是用于保護27.5kV電氣化鐵道系統設備免受大氣過電壓和操作過電壓損壞的保護電器。
復合外套MOA采用優質硅橡膠為原料，從而使產品體積小、重量輕、防爆性能大大提高，硅橡膠固有的憎水性使其具有良好的耐污性能。
瓷外套MOA帶有壓力釋放裝置，MOA故障時內部壓力增大，防爆裝置動作，釋放內部壓力。電弧從內部轉移到外部，在瓷套外部形成短接，保證瓷套不炸裂,

表.鐵道型MOA的技術參數見下表：

27.5kV series of metal oxide surge arresters (hereinafter referred to as MOA) is used to protect the 27.5kV electrified railway system equipment from atmospheric over-voltage and over-voltage protection of electrical damage.
Composite jacket MOA high quality silicone rubber as a raw material, so that the products are small, light weight, explosion-proof performance greatly improved, the inherent hydrophobicity of silicone rubber it has a good stain resistance.
Porcelain jacket MOA with a pressure relief device, the internal pressure increases when the MOA failure, explosion-proof device movement, release the internal pressure. Arc transferred from internal to external, external form in porcelain sets short, no guarantee porcelain burst,

Table technical parameters railroad type MOA in the table below: