As we all know, high-voltage ring main units (HV RMUs) are assembled from numerous components. But do you know what types of sheaths are used for these internal parts? Below is an introduction to the sheaths of internal accessories for HV RMUs:
1. Metal Sheath
Metal sheaths are completely impermeable to water, which can prevent moisture and other harmful substances from entering the interior of cable insulation. They are widely used as sheaths for oil-immersed paper-insulated power cables with low moisture resistance and extra-high voltage cables. Let’s briefly talk about high and low-voltage cable sheaths.
Common materials for metal sheaths include aluminum, lead, and steel. According to different processing technologies, they can be divided into two types: hot-pressed metal sheaths and welded metal sheaths. In addition, formed metal pipes are also used as cable metal sheaths, such as steel pipe cables.
2. Rubber-Plastic Sheath
Rubber-plastic sheaths are characterized by flexibility and light weight, making them extremely widely used in mobiles cables. However, since rubber-plastic materials have a certain degree of water permeability, they can only be used when high-polymer materials with high moisture resistance are adopted as cable insulation. For example, the connecting cable between the primary instrument and the secondary instrument of a split-type zirconia oxygen analyzer uses a rubber-plastic sheath.
The structure of rubber-plastic sheaths is relatively simple, usually consisting of a single sheath. Generally, rubber-insulated cables use rubber sheaths (some use plastic sheaths), while plastic-insulated cables all use plastic sheaths.
3. Composite Sheath
The last type of sheath for internal accessories of HV RMUs is the composite sheath. Also known as integrated sheaths or simplified metal sheaths, they are quite widely used in plastic communication cables. In recent years, they have also received full attention in plastic power cables.
The so-called composite sheath is generally composed of a thin aluminum strip combined with a polyethylene sheath. Therefore, it not only retains the flexibility and light weight of plastic cables but also greatly reduces water permeability compared to single plastic sheaths due to the moisture barrier effect of the aluminum strip.
This article is edited and organized by DAYA Electric Group Co., Ltd. (https://www.hygraphics.com/). Please indicate the source when reprinting.