SC-185,SC-185Z,SC-210Z,SC-210,SC-280
summary:
It is used for insulation and supporting conductor of high-voltage overhead power line with nominal voltage of 35kV and below, frequency not more than 100Hz and altitude not more than 1000m in three-phase power system. The ambient temperature of insulator installation site is - 40 ℃ ~ + 40 ℃.
Structural features:
Porcelain cross arm insulator is a kind of conical or cylindrical porcelain insulator structure which plays the role of cross arm and insulator at the same time. It has the same function of fixing conductor and ground insulation as common line insulator, and it can replace all or part of iron or wood cross arm. This kind of insulator began to develop in China in order to save cross arm materials (metal, cement and wood) and meet the needs of rural power line construction. Compared with disc insulator or long rod insulator, it can also reduce tower height and simplify tower structure. Since the first porcelain cross arm line was put into operation in 1963, it has developed rapidly in recent decades. At present, 110kV and below lines, especially 6-35kV lines, have been widely used.
At the beginning of development, there are two types: pure porcelain type and adhesive type.
Pure porcelain structure is a solid porcelain piece with a mounting hole at the root. When using, the mounting hole passes through the screw and is pressed with a pressing plate. When pressing, a pad (such as asbestos cloth) should be placed between the porcelain piece and the iron piece, and the pressing plate should be pressed with a spring washer. However, the structure has been eliminated due to its low strength and poor reliability.
The glued structure is composed of solid porcelain parts and flange glued with adhesive. The flange is equipped with mounting holes for installation through screws. The porcelain cross arms of medium voltage and above, which are widely used, are equipped with metal accessories (flanges). In order to buffer the impact force generated by line breaking, the flange is also equipped with a stable screw hole. When the use load exceeds the strength of the stable screw, the stable screw is cut off, and the porcelain cross arm rotates around the installation hole, so as to increase the wire sag, reduce the wire tension, and avoid the insulator fracture or rod fall accident. During normal operation, the stabilizing screw can overcome the tension difference between two sides of the conductor under normal conditions. There is no stable screw at the root of pure porcelain type. At this time, the tension difference between the two sides of the conductor is overcome by the friction of the installation part. When the wire is broken, it can also rotate around the installation hole. Elastic gasket (generally linoleum paper) is also padded between the adhesive structure flange and the end face of the porcelain part to reduce the thermal stress. The flange is generally made of malleable cast iron or welded with steel plate. The surface of metal accessories is all hot-dip galvanized. The binder is made up of no less than 42.5 Portland cement and quartz sand.
There are two types of porcelain cross arm insulator: horizontal installation and vertical installation. There are two types of binding wires: direct binding and clamp fixation. If the insulator is installed horizontally, the conductor is bound at the side slot of the head of the porcelain piece with fine metal wire, at this time, the insulator can not be made into the top slot; if the insulator is installed vertically, the conductor is bound on the top slot of the porcelain piece. Therefore, if the top phase porcelain cross arm insulator is installed vertically during operation, the manufacturer shall produce some specifications with top groove for this kind of insulator. Another type of fixed wire is that the head of the porcelain piece is provided with a connecting hardware to clamp the wire.
China's porcelain cross arm insulator is actually a line post insulator, which can rotate in case of an accident.
The electrical and mechanical properties of porcelain cross arm insulator are compared with the common line insulator of the same voltage level, and the characteristics are as follows:
(1) The insulation distance and creepage distance of porcelain cross arm are larger, 50% full wave impulse flashover voltage and dry and wet power frequency flashover voltage are higher;
(2) The porcelain body of the porcelain cross arm is relatively long, and the mechanical bending strength is relatively low. Considering the safety and reliability factor, the allowable maximum load is generally smaller than that of the common line insulator of the same voltage level, so the porcelain cross arm is not suitable for the line with larger conductor section and spacing.
The main advantages of the distribution line with porcelain cross arm compared with that with common insulator are as follows:
(1) With the rotatable structure, when the line breaks, the unbalanced tension of the conductor will make the porcelain cross arm rotate, thus effectively alleviating the expansion of the breaking accident;
(2) The insulation level and lightning resistance level of the line are high, and the accident rate is low;
(3) The porcelain body is easy to be washed by wind and rain, with good self-cleaning, no breakdown and small replacement and maintenance;
(4) It is convenient to construct and install. When the pole height is the same, the distance between the conductor and the ground can be increased by about 0.3-2.2m;
(5) It can save steel, wood and other raw materials, and reduce the cost of single base tower by 10% - 50%.
Model Description:
JB / T 8179-1999 standard (old model):
S -- porcelain cross arm insulator;
S followed by 1, 2, 3 Is the design sequence number;
The figure after "-" is the rated voltage value, kV;
The figure after "/" is the rated bending failure load, kn.
GB / T 21206-2007 standard (new model):
Ra - line post insulator used as cross arm;
The figure after RA indicates the bending failure load value, kn;
The following letters e or j indicate the external or internal gluing of metal accessories;
The following letters T, C and H indicate top binding type, top clamp type of vertical installation or top clamp type of horizontal installation respectively;
The suffix number indicates the specified lightning impulse withstand voltage value, peak value kV;
The suffix letter N or l indicates the standard and longer creepage distances, respectively.
Technical standards:
GB / T 1001.1-2003 insulators for overhead lines with a nominal voltage higher than 1000V - Part 1: porcelain or glass insulator units for a.c. systems - Definitions, test methods and criteria
GB / T 21206-2007 characteristics of line post insulator
JB / T 9676-1999 technical specification for porcelain cross arm insulator of high voltage line
