FZW □ -27.5/D1250-20 outdoor high-voltage AC vacuum load switch isolation switch combination device (hereinafter referred to as the combination device), single-phase column structure, novel structure, with obvious visible fracture, using an operating mechanism to drive the vacuum arc extinguishing chamber, has a large breaking capacity, no arc when breaking and closing current, no fire or explosion hazard, can be operated quickly and frequently, long electrical life, maintenance free and other characteristics.
Combination electrical equipment is a single-phase AC 50Hz, rated voltage 27.5kV single pole outdoor high-voltage switchgear (at an altitude of 2000 meters), widely used in electrified railways for breaking load current, no-load transformers, cable current, capacitor current, and short-circuit fault current.
Scope of application and main technical parameters
The load isolation switch is installed on an outdoor pole and must be able to open and close the normal load current of the line, and integrate the function of the isolation switch to form a visible break. This negative tea isolation switch can be installed in power supply areas such as locomotive depots, partition pavilions, turnaround sections, and station yards, replacing the installation of isolation switches on columns and eliminating the need for circuit breakers specifically designed to cut off normal load currents.

(1) The rated parameters are as follows:
Rated voltage: 27.5kV
Rated current: 1250A
Rated frequency: 50Hz
Rated active load breaking current: 1250
One minute power frequency withstand voltage: 95kV
Isolation fracture distance: ＞ 400mm
Dynamic stable current: 31.5kA
Thermal stability current: 12.5kA
Rated short-circuit closing current: 12.5kA

(2) Overall layout (as shown in the diagram)
The arc extinguishing chamber is installed on the static contact at the incoming line end, and is connected in parallel with the main electrical circuit - the static contact when in the closed position, ensuring that the switch has strong overload bearing capacity and reliable conductivity (equivalent to a closed isolation switch at this time). The isolation fracture is connected with an isolation knife. The driving force of the arc extinguishing chamber is a fast mechanism, and the isolation knife action drives the conductive fork on the fast mechanism to store energy for the fast mechanism. The conductive fork also plays a role in conducting current during the transient process of closing and opening. In order to enable the isolation knife to move quickly, a passing spring is installed on the three-axis of the isolation knife to ensure that the isolation knife can move quickly when it rotates to a certain angle during the opening and closing process.

(3) Action principle (as shown in the diagram)
When the switch is in the closed state, current flows in from the static contact and divides into two paths. One path flows through the vacuum arc extinguishing chamber - conductive fork to the isolation knife (this path has extremely low current), and the other path flows directly from the static contact to the isolation knife, and then flows out from the isolation knife to the output board.
Breaking process: The spindle rotates under the drive of the electric mechanism, and the isolation knife rotates upward through the insulating operating rod. The isolation knife disengages from the static contact, and all the current flows through the vacuum arc extinguishing chamber - the conductive fork. The isolation knife edge does not shake, and the isolation knife drives the conductive fork to continue moving upward. When it reaches a certain angle (43 °), the fork triggers the fast mechanism inside the body, driving the vacuum arc extinguishing chamber to quickly break the current, and the circuit is in an open circuit state. The pulley and conductive fork on the final isolation knife are separated in a non negative state, forming a clear visible isolation fracture and completing the disconnection operation.
The action sequence of the closing process of the switch is opposite to that of the opening process.
When in the closed position, due to the much smaller resistance in the circuit between the isolation blade and the static contact compared to the circuit composed of the fork and the arc extinguishing chamber, the current mainly flows through the circuit composed of the static contact head of the isolation blade. In the normal powered state, the current passing through the temperature rise calibration arc extinguishing chamber circuit in the isolation blade switch state is very small, so this product has reliable electrical performance and outstanding load-bearing capacity.
Transportation, acceptance, and storage
a、 Dynamic transmission: The load switch of the container must not be flipped, inverted, or subjected to strong vibrations during transportation and loading/unloading.
b、 Acceptance: (1) Carefully remove the load switch to prevent damage to the insulation components;
(2) Check the nameplate data of the load switch, whether the product certificate matches the model, and check whether the documents are missing according to the packing list.
c、 Storage: (1) If the load switch needs to be stored, it should be rotated and stored indoors in a dry and ventilated place for a period of ten years.

Precautions
a、 When transporting or hoisting this product, external forces must not be applied to the insulated porcelain pillars at the inlet and outlet ends, otherwise it will cause the insulated porcelain pillars to break, resulting in the product being unusable. In dynamic transmission, there must be no strong vibration rolling phenomenon, and the switch should be effectively grounded during installation.
b、 After installation, use an electric operating mechanism to perform opening and closing operations on the switch for more than 20 times. There should be no improper opening during the opening process, and the isolation fracture should be greater than 400mm. The arc pull rod should be completely detached from the static end contact without any connectors.

FZW-27.5/D1250-20 Outdoor High Voltage AC Vacuum Load Switch