High-voltage switchgear is a critical and highly dangerous piece of equipment in power systems. Its safe use must strictly adhere to regulations, with the core principles revolving around "personal safety" and "equipment safety."
High-voltage switchgear trolleys
Trolleys are classified into several types according to their purpose, including circuit breaker trolleys, metering trolleys, and isolating trolleys. Trolleys of the same brand and specifications are interchangeable. The trolley has test and working positions inside the cabinet, each equipped with a positioning device and connected to electrical and mechanical interlocking devices to prevent operator error and ensure operational safety.
1. The circuit breaker can only be opened or closed when the circuit breaker trolley is in the test or working position. After the circuit breaker is closed, the trolley cannot be moved, preventing accidental opening or tripping of the circuit breaker under load.
2. The circuit breaker trolley can only be moved from the test position to the working position when the grounding switch is in the open position; the grounding switch can only be closed when the circuit breaker trolley is in the test position, preventing accidental closing of the grounding switch under energized conditions and preventing the circuit breaker from closing when the grounding switch is in the closed position.
3. When the grounding switch is in the open position, neither the lower nor the rear door can be opened, preventing accidental entry into a energized compartment.
4. When the circuit breaker is in the operating position, the secondary plug is locked and cannot be removed.
High-voltage switchgear safety interlock devices
To ensure safety and prevent damage to interlocking devices, operation must be performed according to the interlocking procedures. High-voltage switchgear has reliable interlocking devices whose functions are:
1. Preventing accidental operation of circuit breakers.
2. Preventing the operation of disconnecting switches under load, i.e., preventing the trolley from being pushed or pulled under load.
3. Preventing the grounding wire from being connected while energized, i.e., preventing the grounding switch from being closed while energized.
4. Preventing energization with the grounding wire connected, i.e., preventing energization when the grounding switch is in the grounded position.
5. Preventing accidental entry into energized compartments.
Incoming Line Cabinet Power Supply Procedure
1. Close all cabinet doors and rear panels, and lock them (the lower door of the outgoing line cabinet can only be closed when the grounding switch is in the closed position).
2. Push the transfer trolley onto the cabinet and position it. Push the circuit breaker trolley into the cabinet and position it in the test position (when pushing the circuit breaker, press the two push-pull handles of the circuit breaker towards the middle, and simultaneously push the circuit breaker into the cabinet. After the circuit breaker reaches the test position, release the push-pull handles; the handles should automatically return to their original positions). Manually insert the aviation connector, close the trolley compartment door, and lock it.
3. Observe whether the instruments and signal indicators on the upper cabinet door are normal (when normal, the integrated relay protection power indicator is on, the trolley test position indicator, the circuit breaker trip indicator, and the energy storage indicator are on. If all indicator lights are off, open the upper cabinet door and confirm whether each busbar power switch is closed. If they are closed and the indicator lights are still off, the control circuit needs to be inspected).
4. Insert the circuit breaker hand crank into the crank handle socket and press it down firmly. Turn the crank handle clockwise approximately 20 times. When the crank handle is clearly exposed to heat and accompanied by a "click" sound, remove the crank handle. At this point, the circuit breaker trolley is in the working position, the aviation connector is locked, and the main circuit of the circuit breaker trolley is connected. Check the relevant signals (the working position indicator light on the trolley will illuminate, while the test position indicator light will turn off).
5. Observe the live indicator to confirm that external power has been supplied to this cabinet (the live indicator panel switch should be in the ON position; if the live indicator light is on, it indicates that external power has been supplied to the lower contacts of the circuit breaker in this cabinet. If the live indicator light is off, external power must be supplied to this cabinet first).
6. Operate the on/off selector switch on the instrument panel to close the circuit breaker and supply power. Simultaneously, the red closing indicator light on the instrument panel should illuminate, and the green opening indicator light should go out. Check other relevant signals; if everything is normal, power supply is successful. (When operating the on/off selector switch, rotate the operating handle clockwise to the closed position indicated on the panel. After releasing the handle, it should automatically return to the pre-closed position.)
7. If the circuit breaker automatically trips after closing or during operation, the fault must be identified and eliminated before re-energizing according to the above procedure. (At this time, observe the integrated relay protection to determine if the tripping was caused by a line fault or a fault in the integrated relay protection. After maintenance, the integrated relay protection must be manually reset.)
Incoming Line Cabinet Power Deactivation Procedure
1. Observe all relevant signals in the cabinets to confirm that all outgoing line cabinet circuit breakers are in the open position.
2. Operate the on/off switch on the instrument panel to open the circuit breaker and de-energize it. Simultaneously, the red closing indicator light on the instrument panel will turn off, and the green opening indicator light will illuminate. Check other relevant signals; if everything is normal, the power deactivation is successful. (When operating the on/off switch, rotate the operating handle counterclockwise to the open position indicated on the panel. After releasing the handle, it should automatically return to the pre-open position.)
3. Insert the circuit breaker truck handle into the handle socket and press it down firmly. Rotate the handle counterclockwise approximately 20 times. When the handle encounters noticeable resistance and is accompanied by a "click," remove the handle. At this point, the truck is in the test position, the aviation connector lock is released, open the truck compartment door, and manually disconnect the aviation connector (the truck's main circuit is disconnected).
4. Push the transfer trolley onto the trolley and lock it. Pull out the circuit breaker handcart onto the transfer trolley and move the transfer trolley away. (When pulling the circuit breaker, press the two push-pull handles of the circuit breaker towards the middle and pull the circuit breaker out of the cabinet with force. After the circuit breaker is pulled onto the transfer trolley and into place, release the push-pull handles. The handles should automatically return to their original positions.)
5. Observe the power indicator and confirm that it is not energized before continuing operation (the lower door of the incoming line cabinet is forcibly locked with an electromagnetic lock, which can only be unlocked when the incoming line is not energized, but can also be unlocked with a key in an emergency when the incoming line is energized. The tripping of the incoming line circuit breaker does not mean that the incoming line cabinet is not energized. If the external power supply has not stopped, the cable room is energized at this time, and forcibly entering is life-threatening).
6. Open the lower door, test for voltage (testing for voltage is mandatory), discharge voltage (discharging voltage is mandatory), and connect the grounding wire (connecting the grounding wire is mandatory). Maintenance personnel may then enter for maintenance and repair.
Power-on Procedure for Outgoing Line Cabinet
1. Close all cabinet doors and rear panels, and lock them (the lower cabinet door can only be closed when the grounding switch is in the closed position).
2. Insert the grounding switch operating handle into the hexagonal hole on the lower right side of the middle door, and rotate it counterclockwise to put the grounding switch in the open position. Release the operating handle; the interlock plate at the operating hole will automatically spring back, covering the operating hole, and the lower cabinet door will lock.
3. Push the transfer trolley onto the cabinet and position it. Push the circuit breaker trolley into the cabinet and position it in the test position (when pushing the circuit breaker, first press the two push-pull handles of the circuit breaker towards the middle, and simultaneously push the circuit breaker into the cabinet. After the circuit breaker reaches the test position, release the push-pull handles; the handles should automatically return to their original position). Manually insert the aviation connector, close the trolley compartment door, and lock it.
4. Observe whether the instruments and signal indicators on the upper cabinet are normal (when normal, the integrated relay protection power light is on, the handcart test position light, the circuit breaker trip indicator light and the energy storage indicator light are on. If all indicator lights are off, open the upper cabinet door and confirm whether each bus power switch is closed. If they are closed and the indicator lights are still off, the control circuit needs to be inspected).
5. Insert the circuit breaker truck crank handle into the crank handle socket and press it down firmly. Turn the crank handle clockwise approximately 20 times. When the crank handle encounters significant resistance and a "click" sound is heard, remove the crank handle. At this point, the truck is in the working position, the aviation connector is locked, and the main circuit of the circuit breaker truck is connected. Check the relevant signals (the truck's working position light will illuminate, while the truck's test position light will turn off).
6. Operate the on/off selector switch on the instrument panel to close and energize the circuit breaker. Simultaneously, the red closing indicator light on the instrument panel will illuminate, and the green opening indicator light will turn off. Check the energized display and other relevant signals. If everything is normal, energization is successful. (When operating the on/off selector switch, rotate the operating handle clockwise to the closed position indicated on the panel. After releasing the handle, it should automatically return to the pre-closed position.)
7. If the circuit breaker trips automatically after being closed or during operation, the fault must be identified and eliminated before power can be restored according to the above procedure (at this time, observe the integrated relay protection to determine whether the tripping is caused by a line fault or a fault in the integrated relay protection. After maintenance is completed, the integrated relay protection must be manually reset).
Outgoing Line Cabinet Power Deactivation Procedure
1. Operate the on/off selector switch on the instrument panel to trip the circuit breaker and de-energize it. Simultaneously, the red closing indicator light on the instrument panel will turn off, and the green opening indicator light will illuminate. Check other relevant signals; if everything is normal, the power deactivation is successful. (When operating the on/off selector switch, rotate the operating handle counterclockwise to the off position indicated on the panel. After releasing the handle, it should automatically return to the pre-open position.)
2. Insert the circuit breaker truck handle into the handle socket and press it down firmly. Rotate the handle counterclockwise approximately 20 times. When the handle encounters significant resistance and a "click" sound is heard, remove the handle. At this point, the truck is in the test position, the aviation connector lock is released, open the truck compartment door, and manually disconnect the aviation connector (the truck's main circuit is disconnected).
3. Push the transfer trolley onto the trolley and lock it. Pull the circuit breaker handcart onto the transfer trolley and move the transfer trolley away. (When pulling the circuit breaker, first press the two push-pull handles of the circuit breaker towards the middle, and at the same time pull the circuit breaker out of the cabinet with force. After the circuit breaker is pulled onto the transfer trolley and into place, release the push-pull handles. The handles should automatically return to their original positions.)
4. Observe the power indicator and confirm that it is not energized before continuing operation.
5. Insert the grounding switch operating handle into the hexagonal hole on the lower right side of the middle door and rotate it clockwise to bring the grounding switch to the closed position. After confirming that the grounding switch is closed, open the lower cabinet door so that maintenance personnel can enter for maintenance and repair.
6. The grounding switch, circuit breaker, and cabinet door are interlocked. The grounding switch can only be opened or closed when the circuit breaker is in the test position or removed from the cabinet. The circuit breaker can only be moved from the test position to the operating position after the grounding switch has been opened. Forced operation is prohibited. The grounding switch and lower cabinet door interlock can be unlocked in an emergency. Emergency unlocking should only be performed when absolutely necessary; otherwise, there is a risk of electric shock.
Metering Cabinet Operating Procedures
The metering trolley has a direct connection between moving and stationary contacts and does not have breaking or arc-extinguishing capabilities. Operating the metering trolley under load is strictly prohibited. The metering trolley and the incoming line switchgear circuit breaker are electrically and mechanically interlocked. The metering trolley can only be operated after the incoming line circuit breaker has been tripped; forced operation is prohibited to avoid damaging the interlocking device. The operating method for the metering trolley is the same as that for the circuit breaker trolley.
Summary
The safe use of high-voltage switchgear is a systematic project. By following the above points, the operational safety of high-voltage switchgear can be effectively improved, the probability of accidents can be reduced, and the stable operation of the power system can be guaranteed.
Shaanxi Huadian focuses on the research and development and manufacturing of high-voltage switchgear, integrating the craftsmanship spirit of Shaanxi into every process and every test. Our products are not only devices for connecting and disconnecting power, but also the stable foundation of your power system.Please contact us for a quote.
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