The KYN28 switchgear, a widely used medium-voltage power distribution device in China, has demonstrated high reliability during long-term operation, but some typical problems also exist. The following is a systematic overview of these problems and their solutions:
I. Typical Problem Analysis
1. Insulation Performance Degradation and Discharge Issues
Phenomena: Partial discharge, condensation or contamination on insulating surfaces leading to creepage, and insulation aging.
Causes:
Humid and dusty operating environment; failure of internal heating and dehumidification devices.
Poor quality or aging of insulating materials (such as contact boxes, bushings, SMC partitions).
Changes in phase-to-phase or phase-to-ground distances after assembly or vibration.
Typical Case: The lower contact box of the circuit breaker becomes a high-risk area for discharge due to dirt accumulation, moisture, or mechanical damage.
2. Mechanical Operation and Interlocking Failures
Symptoms: Difficulty in cranking the circuit breaker trolley in and out, excessive operating torque on the grounding switch, and jamming or malfunction of the mechanical interlocking.
Causes:
Deformation or misalignment of the guide rails; wear of the trolley rollers.
Complex design of the interlocking mechanism; wear, deformation, or corrosion of components.
Improper operation leading to deformation of components under stress.
Key Risk: Interlocking failure may lead to misoperation, such as closing the circuit breaker with the grounding switch on or opening/closing the grounding switch under load.
3. Excessive Temperature Rise and Overheating of Connections
Symptoms: Temperature rise at moving and stationary contacts, busbar connections, cable joints, etc., exceeds standards (e.g., GB/T 11022).
Causes:
Insufficient contact pressure, wear or oxidation of the silver plating.
Loose bolts, increased contact resistance.
Large load current or the presence of harmonics exacerbates heating.
Poor ventilation and heat dissipation in the cabinet.
4. Valve Mechanism Malfunction
Symptoms: When the handcart is moved out, the valve fails to close automatically and reliably, exposing the energized stationary contacts; when the handcart is moved in, the valve jams and cannot open normally.
Causes:
Fatigue, deformation, or breakage of the valve spring.
Stuck or disengaged transmission linkage mechanism.
Deformation of the valve baffle, interfering with the cabinet or handcart.
5. Secondary Circuit and Component Faults
Symptoms: Relay protection malfunction/failure to operate, indicator lights not illuminating, energy storage motor damaged, poor contact in secondary connectors.
Causes:
Damaged insulation or loose wiring in secondary cables.
Poor quality or misalignment of microswitches, limit switches, or auxiliary contacts.
Oxidation or deformation of pins in the handcart's secondary connector (aviation connector), or misalignment.
Humid environment causing corrosion of terminal blocks and relays.
6. Five-Protection Function Failure
Symptoms: In addition to mechanical interlocking failures, electrical interlocking circuits fail, such as a malfunctioning live indicator (LED) causing forced interlocking grounding switch function failure.
Causes:
Damaged live sensor or faulty display unit.
Damaged interlocking electromagnet or power failure.
Incorrect design or wiring of the five-protection logic circuit.
7. Condensation and Corrosion
Symptoms: Condensation occurs on the inner walls of the cabinet and on the surfaces of components; metal parts (such as bolts and guide rails) corrode.
Causes:
Large temperature difference, high humidity, and poor ventilation.
The cable compartment at the bottom of the cabinet is not properly sealed, allowing moisture to seep in from the cable trench.
The heater is damaged or the condensation controller is malfunctioning.
II. Systematic Solutions and Maintenance Strategies
1. Enhanced Insulation Management
Routine Maintenance:
Regularly (e.g., annually) use an infrared thermal imager to check the overall temperature distribution inside the cabinet and identify localized hot spots.
During power outage maintenance, clean the surfaces of insulating components and check for discharge marks, cracks, or damage. Pay special attention to contact boxes, bushings, and partitions.
Use a torque wrench to check and tighten all main circuit connection bolts to the specified torque.
Technical Upgrades:
Replace with high-quality, arc-resistant, and water-repellent insulating materials (such as DMC, epoxy resin).
In humid areas, enhance the cabinet's dehumidification capacity (e.g., increase heater power, optimize heater layout, ensure the temperature and humidity controller functions properly).
For older cabinets, consider applying an anti-flashover coating (RTV) to critical insulation areas.
2. Mechanical and Interlocking System Overhaul
Adjustment and Lubrication:
Align the handcart guide rails to ensure they are straight and concentric. Replace worn rollers and bearings.
Lubricate all rotating and sliding parts of the interlocking mechanism with specialized low-temperature grease.
Manually operate the interlocking mechanism repeatedly to check its smoothness of operation and logical correctness.
Component Replacement: Replace deformed or worn connecting rods, crank arms, springs, and other critical components promptly. It is recommended to use original or high-specification spare parts.
3. Comprehensive Management of Overheating Issues
Contact Surface Treatment:
During power outage maintenance, inspect the moving and stationary contacts for burns. Minor burns can be smoothed with fine sandpaper and coated with a special conductive paste; severe burns require replacement.
Check and ensure that the contact spring pressure meets the manufacturer's technical requirements.
Monitoring Upgrade:
For critical circuits or high-load cabinets, install a wireless online temperature monitoring system to monitor the temperature of key points such as contacts in real time.
4. Special Maintenance of the Valve Mechanism
Make valve operation testing a mandatory inspection item for every operation of the handcart.
Check the elasticity and integrity of the valve springs; replace fatigued springs.
Adjust the valve transmission mechanism to ensure it moves in coordination and synchronization with the handcart, without jamming.
5. Secondary Circuit Reliability Improvement
Regularly tighten the secondary terminal block wiring and check that the cable markings are clear and undamaged.
Test the on/off status and installation accuracy of all microswitches, limit switches, and auxiliary contacts.
Clean the handcart's secondary connectors, check the pins, and ensure smooth insertion and removal with reliable contact.
Check the resistance and insulation condition of the energy storage motor and the closing/opening coils.
6. Regular Verification of Five-Proof Functions
Strictly adhere to the "five-proof" logic in simulated operation tests, verifying not only mechanical interlocks but also the effectiveness of electrical interlocking circuits (such as live-line display interlocking grounding switches).
Regularly calibrate live-line display devices and sensors.
7. Environmental Control and Sealing
Ensure the fireproof sealant at the cable compartment floor and cabinet connections is tight to prevent moisture and small animals from entering.
Inspect and maintain the ventilation openings and dust filters on the cabinet top.
Ensure the heating and dehumidifying unit is always in automatic and effective operating condition, especially conducting a special inspection before the rainy season and winter.
III. Management Recommendations
1.Standardize operating procedures: Strengthen personnel training, strictly prohibit forced operation, and investigate the cause first when operation is difficult.
2.Improve maintenance strategies: Implement a condition-based maintenance strategy, combining preventative testing (such as loop resistance, insulation resistance, withstand voltage, and partial discharge testing) with online monitoring data to develop customized maintenance plans.
3.Spare parts management: Stockpile critical and easily damaged parts (such as contacts, springs, microswitches, and heaters) to shorten fault repair time.
4.Technological upgrades: For early-commissioned switchgear with significant problems, consider complete renovation or replacement with a new model of switchgear.
Through the above systematic analysis, targeted maintenance and technical upgrades, the operational reliability and service life of the KYN28 switchgear can be significantly improved, ensuring the safe and stable operation of the power grid.
Contact Us
Shaanxi Huadian, as a power equipment manufacturer, produces the KYN28 switchgear, which has certain applications in the industry. It features mature and reliable mechanical interlocking and electrical interlocking schemes to prevent misoperation. The cabinet design fully considers the pressure relief and guidance of internal arc faults, ensuring that energy is released through preset channels, protecting operators and adjacent equipment. For more information, please contact us:pannie@hdswitchgear.com.
