Common Power Supply and Distribution Equipment Selection Manual, Fourth Volume: High-Voltage Switchgear

Author: Editor-in-Chief: Wang Zipu / et al
Publisher:
Publish Date: 2000-04-01
Features:
Excerpt:
(I) The handcart is locked in place by the. The extends through holes in the handcart panel to connect to the. The can move the handcart or lock it in the corresponding position, i.e., the (removal position), (test position), and (working position) (marked on the handcart panel). The also allows the handcart panel to be lifted or lowered, ensuring the handcart is locked to the when in the , preventing movement during operation or faults. When the handcart is in the , turning the to the "/" on the handcart position plaque locks the handcart in the . In this position, the handcart cannot be pushed directly into the or pulled out. At this point, inserting the auxiliary circuit plug allows for testing. Note: Another reason to prevent the handcart from being pushed into the from the is that when the handcart is in the , if the auxiliary plug is not inserted, the (lock bolt) drops, its height being lower than the handcart's height, thus preventing the handcart from being pushed into the . If the auxiliary circuit plug is inserted, the rises, and at this point, turning the to the "" (internal movement position) on the plaque locks the handcart in the .
(II) The mechanical interlock not only moves and locks the handcart but also provides interlocking functionality. When the handcart moves within the, the interlock rod lifts upward, simultaneously raising the (rod), which blocks the iron core, preventing the circuit breaker from tripping. When the handcart is in the and the circuit breaker is in the , the (arm piece) on the main shaft of the mechanism is in a vertical position above the interlock rod, preventing the rod from lifting. As a result, the (pushing arm) cannot rotate, and the handcart cannot move. Only when the handcart is locked in the or do the interlock rod and the return to a downward position, allowing the circuit breaker to perform、 operations. This interlocking ensures the procedural operation of the circuit breaker, i.e.:
a. The circuit breaker in the state prevents the handcart from moving between the and positions.
b. When the circuit breaker handcart moves between the and positions, the circuit breaker cannot trip.
c. The circuit breaker can only be 、 when the handcart is in the or position.
(III) Auxiliary circuit interlock device
The auxiliary circuit plug socket is a 24-pin connector. To ensure proper operation of the switchgear, the auxiliary circuit plug features an interlock mechanism with the following functions:
a. Before the auxiliary circuit plug is inserted into the socket, the interlock prevents the handcart from being pushed from the position to the position.
b. When the circuit breaker handcart is in the position, the auxiliary circuit plug cannot be removed.
c. Before the auxiliary circuit plug is removed, it prevents the handcart from being pulled out from the position.
(IV) Main contacts
The main contacts consist of a moving contact and a static contact. The moving contact is mounted on the handcart, while the static contact is mounted on the main busbar of the. The moving contact is composed of two parallel contact blades and a spring, with a simple structure and easy adjustment. The moving contact can swing vertically by ±10 mm, facilitating handcart interchangeability.
(V) Relay compartment
The relay compartment is located at the front of the top. Its height is typically 750 mm, with an effective area of 625 mm × 640 mm. If more components are required or special specifications exist, a relay compartment with a height of 1000 mm (effective area: 875 mm × 640 mm) can be provided. The relay compartment can house protection and control components. Auxiliary circuit terminals can be installed on both sides and below the compartment, with a maximum of 120 terminals (including positions for auxiliary circuit fuses). The door is equipped with measuring instruments, signal lights, and switchgear.
(VI) Grounding and grounding switch
(I) In the main grounding circuit, every part that can be disconnected from other sections must be grounded. Components such as the relay compartment door are connected to the switchgear casing via soft connection conductors, while the handcart frame is connected to the casing through grounding contacts. Handcart grounding is achieved through grounding contacts between the handcart and the. The grounding contacts ensure the handcart is grounded before the position and maintain continuous grounding from the position to the position. After the switchgear is arranged, a 50 × 5 mm grounding copper busbar is laid along the width of the arrangement at the bottom of the relay compartment. Each has a grounding connection point at the bottom, which is connected to the grounding busbar via a copper bar on the side of the, forming a complete grounding circuit.
(II) Grounding switch
For maintenance safety, grounding switches can be installed in the cable compartments of all circuit breaker cabinets. The grounding switch operates via a large shaft on the lower right side of the for tripping and closing. The front has a position indicator showing the grounding switch's tripped or closed state. The grounding switch features a reliable interlock mechanism to ensure procedural operation, i.e.:
a. The handcart must be removed before the grounding switch can be closed.
b. After the grounding switch is closed, the handcart cannot be pushed in.
(VII) "Five" (Five Protection) functions
An interlock is installed between the grounding switch and the to prevent accidental entry into energized compartments. Cable incoming cabinets, rear overhead incoming cabinets, and bus tie cabinets can be equipped with live display devices to prevent accidental entry. Electromagnetic locks prevent load-breaking operations on isolation carts. Red-green flip cards prevent (incorrect tripping) or (incorrect closing) of circuit breakers. Due to the interlock mechanisms mentioned above, this switchgear meets the "Five" requirements, i.e.:
a. Preventing load-breaking operations on (isolators).
b. Preventing incorrect tripping or closing of circuit breakers.
c. Preventing closing with (grounding wire) present.
d. Preventing energized grounding.
e. Preventing accidental entry into energized compartments.
(VIII) Emergency unlocking
(I) In emergencies or during outages, the handcart panel can be removed from the position.
(II) Three φ4 rivets are visible on the lower right of the handcart panel. Carefully removing these three rivets with a 4 mm drill allows the rear lock to fall off, enabling the panel to be removed from the " position."
(III) After the panel is removed, the main contacts, connecting conductors, and voltage transformers may remain energized. Therefore, avoid touching the rear of the handcart to prevent high-voltage hazards.
(IV) Once the fault is resolved, the lock should be quickly re-riveted to the handcart panel and secured in the " position" to restore the interlock protection.
(V) Emergency unlocking of the grounding switch and interlock can be achieved by removing two φ4 rivets at the lower left of the with a 4 mm drill.
1.4.4 Operating Conditions
(1) Ambient temperature: —10°C to 40°C.
(2) Elevation: not exceeding 1000 m.
(3) Relative humidity: monthly average not exceeding 90%, daily average not exceeding 95%.
(4) Earthquake intensity: not exceeding 8 degrees.
(5) No fire, explosion, severe pollution, chemical corrosion, or violent vibration hazards.