Analysis Of The Symbol System Of Drop-out Fuses And Engineering Application Specifications
The symbolic representation of High Voltage Fuse in electrical drawings is an important part of the power system design language. Its graphical expression carries core information such as equipment functional attributes, technical parameters and installation requirements. Based on the international electrical symbol standard, this article systematically explains the composition logic and application specifications of its symbol system.
1. Analysis of the composition of basic symbols
... 4728.7 stipulates that the basic symbol of the drop-out fuse consists of a rectangular frame and a wavy line. The rectangle represents the fuse body (size ratio 1:2.5), and the wavy line (wavelength 3mm) symbolizes the fuse element. The IEC 60617 standard uses an inverted triangle superimposed with a horizontal line segment to highlight its drop-out characteristics.
... ... Arc extinguishing structure expression
... 2. Symbolic semantic expansion system
... For example, "12/100/6.3" means 12kV, 100A, 6.3kA breaking capacity. The US IEEE standard requires that the insulation level (such as BIL 75kV) be marked on the lower right side of the symbol.
... ... ... ... 3. ... Special attention should be paid to symbol conversion in the design of cross-border projects. A certain ASEAN interconnection project once caused incorrect fuse selection due to symbol misunderstanding.
Conflict between power and building standards
Building electrical drawings (GB/T 50786) are often simplified to ordinary fuse symbols, ignoring the drop characteristic annotation. It is recommended to add characteristic annotations in joint design. For example, a data center project avoids construction misreading by annotating "DROP-OUT" next to the symbol.
GB/T 4728-2018 changes the operating mechanism symbol from rectangle to ellipse, and the old version of the drawing reconstruction project needs to convert the symbol. A typical case is a rural power grid reconstruction project, in which 20% of the fuses were installed in the wrong direction due to the failure to update the symbol system.
... For fuse groups used in parallel, a 0.5mm spacing must be added between symbols, and the synchronous action mark "SYN" must be marked.
... ... ... In the protection logic diagram, the fuse symbol needs to establish an association line with the protection relay (line type 0.25mm dotted line), and the action delay parameter should be marked at the connection point. The dual configuration system should use mirror symmetric symbols, and the spacing should be kept at 150% of the body width.
V. Symbolic development in technological evolution
... A smart substation project has achieved millimeter-level spatial mapping between symbols and physical equipment.
... RoHS-compliant fuses must have a green leaf-shaped mark in the upper right corner of the symbol, and materials containing hexavalent chromium must be warned with an orange triangle. EU CE certification requires the environmental protection level (such as EPL B2) to be indicated next to the symbol.
... For fuses with the function of remaining life prediction, a progress bar is added under the symbol to intuitively display the service status through the filling ratio (0-100%). Singapore Power Grid has applied this dynamic symbol system in its asset management system.
