Overvoltage protector
1. Purpose and applicable conditions
Electrical systems usually use circuit breakers to operate high-voltage motors. Therefore, during operation, operating overvoltages are prone to occur, especially interception overvoltage, reignition overvoltage, and interruption overvoltage. This kind of operating overvoltage has a strong destructive effect on the motor stator coil and transformer winding. In severe cases, insulation breakdown may occur. Therefore, measures must be taken to limit the operating overvoltage to protect the safe and reliable operation of electrical equipment and at the same time expand the application scope of vacuum circuit breakers. The commonly used oxidation arresters can only protect electrical equipment from phase-to-ground overvoltage damage, but cannot limit phase-to-phase overvoltage. Three-phase combined overvoltage protectors are two new types of overvoltage protectors designed according to market needs and to address the shortcomings of existing arresters. Its main components are a combination of discharge electrodes, metal oxide resistors, three-phase combination bases, organic composite jackets, etc. This novel and unique design and structure has incomparable advantages. One three-phase combination overcurrent protector can replace six ordinary zinc oxide arresters. It is mainly used in power plants and substations. The power system of the factory can not only limit the lightning overvoltage of electrical equipment such as generators, transformers (including electric furnace transformers), switches, busbars, motors, and parallel compensation capacitors, but also limit the operating overvoltage and phase-to-phase overvoltage of the power system, providing reliable protection for electrical equipment. This product can be used as over-voltage protection for high-voltage electrical equipment in 3-35kV neutral point ungrounded systems as well as over-voltage protection for other electrical equipment.
1.1 Ambient temperature: -40℃~+40℃, altitude does not exceed 3000m, wind speed does not exceed 35m/s,
1.2 The power frequency is not greater than 62Hz and not less than 48Hz
1.3 Areas with earthquake intensity below 7 degrees are suitable for dirty areas.
The three-phase combined overvoltage protector is a novel overvoltage protection device. It is mainly used in power systems below 35kV to protect transformers, switches, busbars, motors, parallel compensation capacitors and other electrical equipment. It can limit atmospheric overvoltage and operating overvoltage caused by various vacuum circuit breakers. Both phase-to-ground and phase-to-phase overvoltage can cause reliable limiting effects. The three-phase combined overvoltage protector consists of four lightning arresters forming a four-star connection, so that the overvoltage of each phase to ground and between phases is protected. Due to the clever coordination of the structure, one overvoltage protector functions as 6 lightning arresters. At the same time, it overcomes the shortcoming that the simple star connection method of three arresters cannot better protect the phase overvoltage. The three-phase combined overvoltage protector can be a series gap type or a gapless type.
5. Test installation and precautions of protector
1. Measure the leakage current at 1mA DC reference voltage and 0.75 times the 1mA DC reference voltage.
The test is carried out with a high-voltage DC generator, and DC high voltage is applied to A and D, B and D, C and D of the tested product respectively. Slowly and evenly increase the output voltage of the test transformer, and observe the changes of the voltmeter and ammeter at the same time. When the ammeter displays 1mA, read the reading of the voltmeter, which is the reference voltage value. Then add 0.75 times of this reading to both ends being measured, and the reading displayed by the ammeter is the leakage current.
2. Test precautions:
a. Remember that traditional arrester test methods cannot be used to conduct work discharge tests on this overvoltage protector;
b. When doing insulation tests on other electrical equipment, the protector connecting wire should be removed;
c. This product undergoes a preventive test every one to two years, and the dust on the outer surface of the protector is cleaned at the same time.
3. Installation and precautions:Pay Attention to Cold Shrink Cable Termination Technology
a. The indoor type can be installed upright in various types of switch cabinets. In addition to being directly connected to switch cabinets "A", "B","C"The wire nose connecting the three phases and the ground phase ("D" phase) is outside the bare conductor, and the rest is enclosed by the insulator. Therefore, the distance between the phases and the ground (or cabinet) and the cabinet installation space requirements are correspondingly small. It can be installed directly in the handcart chassis of the switch cabinet or in the transformer room;
b. For a protector with an intelligent monitor, first install the protector body and the monitor (embedded in a place that is easy to observe, and the shell must be grounded). After they are fixed, they are connected through a seven-core shielded cable with an aviation plug. For details on the installation dimensions, see the "Smart Overvoltage Monitor Instructions";
c. When the protector is connected to the three-phase power supply (A, B, C) and the ground terminal (D), the following matters must be paid attention to;
(1) The distance between the connecting noses on the cable should meet the minimum safety distance requirements between different phase live conductors of different voltage levels;
(2) The safety distance between protector cables and the safety distance between protector cables and different-phase busbars or cabinets) should not be less than the phase-to-phase distance at the outlet of the protector cable (should be under cable tension);
(3) The length of the high-voltage cable should be selected according to the installation location, and the length should be appropriate. If it is too long, the phase cable can be bundled and fixed on the same phase busbar (line). It is strictly prohibited to bundle different phase cables together;
(4) When users install a protector on a trolley, they can first fix the B phase of the protector facing the B phase of the busbar, and then perform wiring;
(5) It is strictly prohibited to carry cables during installation, and care should be taken to prevent high-voltage cables from being cut by sharp objects.
d. After connecting the ground terminal of the column protector, wrap the exposed connection part with heat shrink tube.
