1structural characteristics
At the beginning stage of development, there are two types: pure ceramic and adhesive.
The adhesive structure is composed of solid ceramic parts and flanges glued together with adhesive. The flanges are equipped with mounting holes for screws and nails to be installed. Ceramic crossarms with medium voltage and above voltage levels that are widely used are equipped with metal accessories (flanges). In order to buffer the impact force generated when the line breaks, the flange is also equipped with stabilizing screw holes. When the load exceeds the strength of the stabilizing screw, the stabilizing screw will cut off and the porcelain cross arm will rotate around the installation hole, thereby increasing the relaxation of the wire, reducing the tension of the wire, and avoiding insulator breakage or pole collapse accidents. Stable screws during normal operation can overcome the tension difference between the two sides of the wires that exists under normal circumstances. Pure ceramic roots do not have stable screws, and in this case, the frictional force at the installation site overcomes the tension difference between the two sides of the wire. When the wire breaks, it can also rotate around the installation hole. There is also an elastic pad (usually made of felt paper) between the flange of the adhesive structure and the end face of the ceramic part to reduce thermal stress. Flanges are generally cast from malleable iron or welded from steel plates, and the surfaces of metal accessories are all hot-dip galvanized. The adhesive is prepared by mixing not less than 42.5 grade Portland cement and quartz sand.
The porcelain cross arm insulator in our country is actually a type of line column insulator that can rotate during accidents.
(1) The insulation distance and creepage distance of the porcelain cross arm are relatively large, and the 50% full wave impulse flashover voltage and dry and wet power frequency flashover voltage are relatively high;
Compared with distribution lines installed with ordinary insulators, the main advantages of porcelain cross arm distribution lines are:
(2) The insulation level and lightning resistance level of the line are relatively high, and the accident rate is low;
(4) Construction and installation are convenient, and the same height of the pole can increase the distance between the wire and the ground by about 0.3-2.2m;
2、 Model Description
S - Ceramic cross arm insulator;
The number after "-" represents the rated voltage value, kV；
GB/T 21206-2007 standard specifies (new model):
The number after RA represents the bending failure load value, kN；
The following letters T, C, and H respectively represent top tie type, vertically installed top clamp type, or horizontally installed top clamp type;
The letters N or L in the suffix represent standard and longer creepage distances, respectively.
GB/T 1001.1-2003 "Insulators for overhead lines with nominal voltage above 1000V - Part 1 Ceramic or glass insulator components for AC systems - Definitions, test methods and criteria for determination"
JB/T 9676-1999 Technical Conditions for Ceramic Cross arm Insulators for High Voltage Transmission Lines
<p style="font-family:" color:#333333;text-indent:0px;background-color:#ffffff;"="">JB/T 8179-1999 "Dimensions and Characteristics of Ceramic Cross arm Insulators for High Voltage Transmission Lines"
