In the past, distribution transformers were damaged by lightning strikes, which were thought to be caused by lightning waves entering the high-voltage windings. In fact, this perception is not comprehensive.
Oil-immersed transformers are the most common transformers in the world and the simplest transformers to maintain. But simple maintenance does not mean protection from damage. Oil filled transformers often have burnouts.
How to prevent oil-immersed transformers from being burned out? Ensuring the safe operation of the oil-immersed transformer and preventing the oil-immersed transformer from burning out is very important in daily work. It is also the peak season of thunderstorms and the peak of power load. The oil-immersed transformer is easy to burn out. It is also the period of frequent accidents. The following measures can strengthen operation management and maintenance:
First, why use isolation transformer
Why use an isolation transformer? When supplying power to a low-voltage user, the power supply system generally adopts a three-phase four-wire system. The neutral line is grounded, that is, the wires to the residents’ homes, one is the phase line (the fire line), and the other is the neutral line. It is in the same position as the earth. When the human body touches the hot bottom plate, it will cause current to flow through the human body and form a loop with the earth, causing electric shock hazard. If an isolation transformer is used, it will be safer because the primary and secondary exchange energy through the magnetic field, and there is no physical hard connection. Even if the human body touches the charged item, the potential of the charged part is due to the same position of the human body and the earth. Low potential, will not cause electric shock hazard.
Second, the role of isolation transformer
The main function of the isolation transformer is to completely insulate the electrical of the primary side from the secondary side and also isolate the circuit. In addition, the high frequency loss of the iron core is utilized to suppress high frequency noise from being transmitted to the control loop. The isolation transformer is used to suspend the second ground to the ground, and can only be used in the case where the power supply range is small and the line is short. At this point, the system’s capacitance to ground capacitance is not small enough to cause personal injury. Another important role is to protect personal safety and isolate dangerous voltages.
The isolation transformer is a transformer that is electrically isolated from the input winding and the output winding. The isolation transformer is used to avoid accidental simultaneous contact with the charged body. The isolation of the transformer is to isolate the current of the original secondary winding around the coil. Early used in Europe for the power industry, power supply for control circuits, safety lighting and indicator lights for general circuits in the electronics industry or industrial and mining enterprises, machine tools and machinery.
Hermetically sealed transformer is the electrical equipment that transforms voltage and transmits electrical energy in the power grid. It is the carrier that the power grid supplies power to users. Therefore, the safety of transformers is related to people’s living electricity. However, Sealed power transformers often have various faults during operation. One of the common problems is overvoltage.
Overvoltage refers to the phenomenon that the rms value of the AC voltage rises at the power frequency, exceeding 10% of the rated value, and the long-term voltage fluctuation is longer than 1 minute. The occurrence of overvoltage is usually the result of load switching, for example: Cut off a large capacity load or energize the capacitor bank (overvoltage caused by excess reactive power compensation).
Overvoltage refers to a sudden voltage rise that is dangerous to insulation. This abnormal voltage rises up to several times the rated voltage of the equipment, which seriously threatens the safety of the oil immersed transformer insulation. If the overvoltage duration Longer, it will cause damage to the transformer.
There are several reasons why a transformer generates an overvoltage:
(1) Atmospheric overvoltage The overvoltage induced on the transmission line by lightning strikes the transmission line or tower, or due to the discharge of thunderstorm clouds in the atmosphere.
(2) Operating overvoltage The overvoltage caused by the closing or closing of the circuit breaker on the transformer or line.
(3) Fault overvoltage An overvoltage generated by a single-phase short circuit or intermittent arc grounding in the system.
Regardless of the overvoltage, the time of action is very short, only a few tens of microseconds. The values of the operating overvoltage and fault overvoltage are generally 2 to 4.5 times the rated phase voltage, and the atmospheric overvoltage can be 8 to 12 times the rated phase voltage. With an overvoltage of 2.5 times or less, the transformer is generally capable of withstanding. More than 2.5 times, any overvoltage can damage the insulation of the transformer.
In order to ensure the safety of the oil-immersed transformer in the operation of the power grid, in addition to the selection of high-quality ZTELEC hermetically sealed transformer, it is necessary to set reasonable and effective over-voltage protection measures for the transformer.
The PCB board is a printed circuit board, which is a general term for commonly used circuit boards. It is divided into: cardboard, semi-glass fiberboard, fiberglass board, metal substrate, etc. according to the material.
A regulated power supply is an electronic device that provides a stable AC or DC power supply to the load. When the grid voltage fluctuates instantaneously, the regulated power supply compensates the voltage amplitude with a response speed of 10-30ms, which makes it stable within ±2%. In addition to the most basic stable voltage function, the regulator should have overvoltage protection (+10% of output voltage), undervoltage protection (-10% lower than output voltage), phase loss protection, short circuit overload protection. Basic protection features.
5G high frequency copper clad laminates passed the test of the designated testing agency of the Ministry of Industry and Information Technology of China
The copper-clad high-frequency electronic substrate products (hereinafter referred to as “5G high-frequency copper-clad boards“) for the 5G communication equipment developed and produced by ZTELEC GROUP have been successfully tested by the third-party testing institutions designated by the Ministry of Industry and Information Technology, marking ZTELEC’s first high at 5G. The development of frequency-covered copper plates has been successful.
High Density Polyethylene Sheets. Chinese name: Polyethylene plate. PE sheet is a high crystallinity, non-polar thermoplastic resin. The original HDPE has a milky white appearance and a semi-transparent shape in a thin section.
PE sheet product features:
1. The wear resistance of high molecular weight polyethylene board is the first in plastics, and the higher the molecular weight, the higher the wear resistance and impact resistance of the material;
2. The impact strength of ultra-high molecular polyethylene sheets is the highest value among existing plastics, and there is still a relatively high impact strength even at -70 ° C;
4. Ultra-high molecular weight polyethylene has extremely low water absorption. Therefore, its physical and mechanical properties are independent of the humidity factor in the operating conditions used;
5. Ultra-high molecular weight polyethylene is chemically stable, and can resist corrosion of various corrosive media and organic solvents such as acid, alkali and salt at a certain temperature and concentration range;
6. Ultra-high molecular weight polyethylene is odorless, non-toxic, odorless, non-corrosive, physiologically circulatory and physiologically adaptable.
PP sheet is polypropylene plastic
Specific gravity: 0.9-0.91 g / cm 3 Molding shrinkage: 1.0-2.5% Molding temperature: 160-220 ° C
Low density, strength and stiffness, can be used at about 100 degrees. It has good electrical properties and high-frequency insulation, which is not affected by humidity, but becomes brittle at low temperature and is not resistant to mold aging. It is suitable for making general mechanical parts and corrosion-resistant parts. And insulating parts
Molding performance 1. Crystallized material, low hygroscopicity, easy to melt fracture, long-term contact with hot metal is easy to decompose.
2. Good fluidity, but the shrinkage range and shrinkage value are large, and shrinkage, dent and deformation are easy to occur.
3. The cooling rate is fast, the pouring system and the cooling system should be slowly dissipated, and the molding temperature should be controlled. The direction of the material is low and the direction is obvious. The low temperature and high pressure are especially obvious. When the mold temperature is lower than 50 degrees, the plastic parts are not smooth and easy to produce. Poor welding, leaving marks, warping deformation is easy to occur above 90 degrees
4. The plastic wall thickness should be uniform to avoid lack of glue and sharp corners to prevent stress concentration.
PVC, polyvinyl chloride, English Poly (Vinyl Chloride)
Specific gravity: 1.38 g / cm 3 Molding shrinkage: 0.6-1.5% Molding temperature: 160-190 ° C
Mechanical properties, excellent electrical properties, strong acid and alkali resistance, good chemical stability, but low softening point. Suitable for making thin plates, wire and cable insulation, seals, etc.
1. Amorphous material, low moisture absorption, poor fluidity. In order to improve fluidity and prevent air bubbles, the plastic can be pre-dried. The mold casting system should be short and thick, the gate section should be large, and there must be no dead angle. The mold must be cooled and the surface should be chrome-plated.
2. It is easy to decompose. It is more easily decomposed with steel and copper at 200 °C. It will escape corrosion when decomposed. Irritant gas. The molding temperature range is small.
3. When using the screw injection machine nozzle, the hole diameter should be large to prevent dead angle stagnation. Good without inserts, if there are inserts should be preheated