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Heihe One of the three major inland rivers in China's Hexi Corridor. Originating in the northwest of Gansu Province, it is formed by the rivers flowing from the Nanshan and Qilian Mountains between Zhangye and Jiuquan. The total length is about 800 kilometers. Flow through desert salt marshes. From Tiancang in Jinta County to Huxin Village in Ejin Banner, Inner Mongolia, it is called weak water (or Ejin River). Huxi Xincun is divided into two branches below: the Donghe (Nalin River) is injected into Sogonor, and the Xihe (Mulin River) is injected into Gasunnoor. The Heihe River Valley is the only settlement in Alxa Heights. It was originally the home of the Central Asian Silk Road. A large number of cultural relics have been unearthed in the past 70 years. From 1930 to 1931, a northwestern scientific expedition jointly organized by China and Sweden discovered more than 10,000 wooden slips before the Eastern Han Dynasty in Juyan, and more than 20,000 were unearthed in 1973. Most of these Han Bamboo Slips are the Tunshu documents from 73 to 48 BC. They are the earliest official documents in China and are extremely precious. The Heihe River Basin is the second largest inland river in the northwestern part of China. It originated from the interruption of the northern foothills of the Qilian Mountains. The river basin is bounded by the Qilian Mountains in the south and borders the Mongolian People's Republic in the north. The river basins are connected to the north to Juyanhai in the Ejina Banner of the Inner Mongolia Autonomous Region, and border the Mongolian People's Republic. The watershed ranges from 98-102 ° east longitude and 37 ° 50′-42 ° 40 ′ north latitude. It involves Qinghai, The three provinces (autonomous regions) of Gansu and Inner Mongolia Autonomous Region have a total land area of 14.29 square kilometers, including 61,800 square kilometers of Gansu Province, 10,400 square kilometers of Qinghai Province, and about 70,700 square kilometers of Inner Mongolia. There are 35 small tributaries in the Heihe River Basin. With the continuous increase of water use, some tributaries gradually lose their surface hydraulic connection with the main stream, forming three independent sub-water systems in the east, middle and west. The western sub-water system includes the Tanlai River and the Hongshui River, which belong to the Jinta Basin, covering an area of 21,000 square kilometers; the central sub-water system, including the Maying River and the Fengle River, belong to the Gaotai Yanchi Yiminghua Basin, with an area of 0.6 10,000 square kilometers, the eastern sub-water system is the main stream of the Heihe River, including the main stream of the Heihe River, Liyuan River, and more than 20 small tributaries along the mountain, covering an area of 116,000 square kilometers. The main stream of the Heihe River is 821 kilometers in length. It is above the Yingluo Gorge at the exit of the mountain. The river is 303 kilometers long and covers an area of 10,000 square kilometers. Both sides of the river have high mountains and valleys, the river bed is steep, the climate is humid and cold, and the vegetation is good. It is less than 2 ℃, and the annual precipitation is 350 mm. It is a runoff area in the Heihe River Basin. The middle reaches of Yingluo Gorge and Zhengyi Gorge are 185 kilometers long with an area of 25,600 square kilometers. The land on both sides of the strait is flat, with sufficient light and heat resources, but the drought is severe. The annual precipitation is only 140 cm, the average annual temperature is 6-8 ° C, the annual sunshine hours are up to 3000-4000H, the annual evaporation capacity is 1410 mm, and the area of artificial oasis. Large, severe salinization of land in some areas. Below the Zhengyi Gorge is the downstream, with a river length of 333 kilometers and an area of 80,400 square kilometers. Except for the river banks and the Juyan Delta, most of them are desert Gobi. The annual precipitation is only 47 centimeters, and the average annual temperature is about 8-10 ° C. Extreme minimum temperature is below -30 ℃, extreme maximum temperature exceeds 40 ℃, annual sunshine hours are 3446H, annual evaporation capacity is up to 2250 cm, climate is very dry, drought index reaches 47.5, belongs to extreme arid area, wind and sand damage is very serious, and it is a serious problem for China. One of the main sources of sandstorms in the north. High-voltage market: Heihe High Voltage Fuse

High-voltage fuse use

It is mainly used for overload and short circuit protection of high voltage transmission lines, voltage transformers, voltage transformers and other electrical equipment.

High-voltage fuse engineering principle

Its structure generally includes a fuse tube, a contact conductive part, a support insulator and a base, and the fuse tube is filled with quartz sand fine particles for arc extinguishing. Fuse is a metal wire or metal sheet made of a metal material with a lower melting point, connected in series in the protected circuit. When the circuit or the equipment in the circuit is overloaded or malfunctions, the fuse heats up and melts, thereby cutting off the circuit and achieving The purpose of protecting a circuit or device.

Selection of high-voltage fuse type

There are two types of high-voltage fuses commonly used in 3 ~ 66kV power stations and substations:
It is an indoor high-voltage current-limiting fuse with rated voltage levels of 3, 6, 10, 20, 35, and 66kV. Common models are RN 1, RN 3, RN 5, XRNM 1, XRN T 1, XRN T 2, XRN T3 type is mainly used to protect the overload and short circuit of power lines, power transformers and power capacitors; RN2 and RN 4 types have a rated current of 0.5 ~ 10A, which is a special fuse for protecting voltage transformers. The other type is outdoor high-pressure jet fuses. When the fuse melts to generate an arc, the arc burns against the white paper to produce gas and stretches the arc. The arc inductance reacts to change phase, and a zero break occurs when the current crosses zero. In order to open the circuit, the current limiting effect is not obvious. Commonly used are drop-out fuses . The types are RW 3, RW 4, RW 7, RW 9, RW 10, RW 11, RW 12, RW 13, and PRW series. Their functions are the same as those of RN 1. Under certain conditions, unloaded overhead lines, no-load transformers, and small load currents can also be disconnected and closed. Outdoor porcelain sleeve type current limiting fuse RW 10- 35 / 0.5 ~ 50-2000MVA type RW10-35 / 0.5 ~ 1-2000MVA is an outdoor product dedicated to protect 35kV voltage transformers. So choose according to the type of fuse and different protection objects.

1. Select by working voltage

(1) General conditions
U e≥Uwe
In the formula:
U e——rated voltage of fuse
Uwe-rated voltage of the grid at the installation
That is, the rated voltage (kV) of the fuse should not be less than the rated voltage (kV) of the power grid where the fuse is installed.
(2) For current-limiting fuses
The current-limiting fuses with quartz sand as the fuse filling material can only be selected according to the condition of Ue = Uwe. In this case, the maximum overvoltage multiple generated by such fuses is limited to the specified 2.5 times the phase voltage. This value does not exceed the insulation level of appliances of the same voltage level. If the fuse is used in a power grid whose operating voltage is lower than its rated voltage, the threat caused by multiples of overvoltage may increase by 3.5 to 4.

2.Select according to working current and protection characteristics

(1) General conditions
I e≥Ije≥Ig · zd
In the formula:
I e——rated current of fuse, A
I je——rated current of fuse, A
I g · zd——Maximum continuous working current of circuit, A
This condition is the overall requirement for selecting the rated current of the fuse, of which the selection of the rated current of the fuse is the most important. Its selection is related to its fusing characteristics and should be able to meet the requirements of protection reliability, selectivity and sensitivity.
(2) Specific situation
①Protect power distribution equipment (ie, 35kV and below power transformers):
Ije = K Ie
Where
Ie——rated working current of transformer loop, A
K——Reliability coefficient, 1.5 ~ 2.4 is not taken into consideration when the motor is self-starting, 2.4 ~ 4.0 is taken into consideration when the motor is self-starting
Selecting according to this condition can ensure that the transformer does not fuse when the transformer passes the maximum continuous working current, through the transformer inrush current, and the impulse current generated by the motor from starting or short circuit outside the protection range, and it can ensure the selectivity of the front and rear protection actions and this paragraph. Short circuit in the range can clear the fault in the shortest time.
② Protection of power capacitors:
Ije = K Ic · e
In the formula:
I c · e——rated current of capacitor circuit, A
K —— Reliability coefficient, for jet fuses, 1.35 ~ 1.5; For current-limiting fuses, when a capacitor, the coefficient is 2 ~ 2.8; when a group of capacitors, the coefficient is 5 ~ 10
③ Protection of power lines:
Select by general conditions:
Ie≥Ije≥I g · zd

3. Select by breaking current

(1) General conditions
I ke≥I dt (Ske≥Sdt)
In the formula:
I ke (or Ske) —— rated breaking current of the fuse, kA (or rated breaking capacity MVA)
I dt——short-circuit full current, kA (installation place)
For current-limiting fuses, take I dt≥I ″ (sub-transient current amplitude); for non-current-limiting fuses, take I dt≥I ch (maximum effective value of steady-state short-circuit current).
(2) For drop-out fuse
The breaking capacity of the drop-out fuse should be checked according to the upper and lower limit values. The maximum operating mode of the system should be applied when checking the upper limit value. The minimum operating mode should be used when checking the lower limit value.


Summary of high-voltage wall bushing


High-pressure wall-through bushings are also called high-pressure wall-through pipes, waterproof bushings, wall-embedded pipes, and waterproof bushings are divided into rigid waterproof bushings and flexible waterproof bushings. The two are mainly used in different places. Flexible waterproof sleeves are mainly used in places such as civil defense walls and pools. Rigid waterproof sleeves are generally used in locations such as basements where pipes need to pass through.
Flexible waterproof casing is suitable for the hardware fittings of the structure where the pipeline passes through the wall subject to vibration or strict waterproof requirements. General manufacturers are manufactured according to the S312, 02S404 standard atlas developed by the Institute of Building Science. Flexible waterproof casings pass through walls. If non-concrete is used, concrete walls should be used instead, and the casings must be solidified in the walls at one time. Flexible waterproof casings are widely used in construction, chemical, steel, tap water, and sewage treatment. And other units.
Rigid waterproof casing is a steel pipe plus a wing ring (annular sleeve made of steel plate is placed on the steel pipe), and it is installed in the wall (mostly concrete wall). The outer wing ring, the inner ring and the like are also available. The flange inner wire is sold in sets or can be processed on its own. It is used for pipes that require shock absorption, such as pipes connected to water pumps passing through walls.
Both flexible waterproof sleeves and rigid waterproof sleeves are hardware fittings used for pipes to pass through the walls of buildings subject to vibration or strict waterproof requirements. They are often used in construction, chemical, steel, tap water, sewage treatment and other units.





High-voltage load switch function

Under the specified conditions of use, a certain capacity of no-load transformers (315KVA indoor, 500KVA outdoor) can be connected and disconnected; no-load overhead lines (5KM indoor, 10KM outdoor) can be connected and disconnected; Connect and disconnect a certain length of no-load cable line.

Difference between load switch, disconnect switch and circuit breaker

1. The load switch can be disconnected with a load and has a self-extinguishing function, but its breaking capacity is very small and limited.
2. Generally, the disconnecting switch can not be disconnected with load. There is no arc extinguishing cover on the structure, and there is also an isolating switch that can disconnect the load. The structure is different from the load switch, which is relatively simple.
3. Load switches and disconnectors can form obvious disconnect points. Most circuit breakers do not have isolation function, and a few circuit breakers have isolation function.
4. Isolation switch does not have protection function. The protection of load switch is generally added with fuse protection, only quick-break and over-current.
5. The breaking capacity of the circuit breaker can be made very high in the manufacturing process. It mainly depends on the current transformer and the secondary equipment to protect it. Can have short circuit protection, overload protection, leakage protection and other functions.

Arc extinguishing principle of high voltage load switch

(FN3-10R) --- The main shaft drives the piston to compress the air when the brake is opened, so that the compressed air is ejected from the nozzle at high speed to blow out the arc; Make up. (Vacuum tube)

Characteristics of high voltage load switch

A. It can isolate the power supply and has obvious disconnection points. It is mostly used for fixed high-voltage equipment.
B. There is no arc extinguishing device, and the normal working current and short circuit can be passed in the closed state.
C. It is strictly forbidden to connect and disconnect the circuit with load, and it is often used in series with the high-voltage circuit breaker .

Precautions for high voltage load switch

A. For vertical installation, the switch frame, closing mechanism, cable sheath, and protective steel pipe should be reliably grounded (cannot be grounded in series).
B. No-load opening and closing operations should be performed several times before operation. There is no jamming in each rotating part, and the closing is in place. There is a sufficient safety distance after opening.
C. The fuse of the fuse used in series with the load switch should be selected properly, that is, the fuse should be blown first when the fault current is greater than the breaking capacity of the load switch, and then the load switch can be opened.
D. The contact is good when the switch is closed, and there is no overheating at the connection part. During the inspection, pay attention to check the porcelain bottle for dirt, cracks, porcelain dropout and flashing discharge. Do not flush the switch with water (indoor type). (When a high voltage cabinet controls a transformer, it is best to stop the circuit high voltage cabinet when replacing the fuse.)
A high-voltage load switch is an electrical appliance that functions between a high-voltage circuit breaker and a high-voltage isolation switch . High-voltage load switches are often used in series with high-voltage fuses; they are used to control power transformers. The high voltage load switch has a simple arc extinguishing device, because it can switch on and off a certain load current and overload current. However, it cannot disconnect the short-circuit current, so it is generally used in series with a high-voltage fuse, and the fuse is used for short-circuit protection.
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