Urumqi Nantianya Electrical Complete-sets Equipment Co.,Ltd.
Add : 366 Tongbaishan Street, Economic and Technological Development Zone, Urumqi
Phone : 86-:13809951165
Service Phone :0991-4653766


Possible faults and handling during operation of SF6 circuit breaker

Possible faults and handling during operation of SF6 load switch

I. Analysis and overhaul of possible failures

1. Leakage analysis and processing (density relay signaling)

1) Density relay signaling

a density relay action value error, false signal, adjust or replace it; secondary wiring failure, find the wrong point, correct the wiring;

b The air leakage of the circuit breaker body, find out the cause of the air leakage, and then deal with it.

2) When the SF6 gas leaks normally to the density relay, the air can be calibrated according to the SF6 gas pressure-temperature curve to reach the rated pressure; when the air is supplied, it can be carried out under live operation.

3) When the pressure of SF6 gas drops rapidly or zero gauge pressure occurs, it should immediately exit the operation; and analyze whether it is caused by the following reasons:

a There is a problem with the quality of the welded parts and the welds are leaking;

b the surface of the casting is leaking (with pinholes or blisters);

c The seal ring is aging or the bolts and threads of the sealing part are loose;

d Leakage at the gas line connection;

e The pressure gauge or density relay leaks and should be replaced.

Find out the specific cause of the leak and carry out maintenance with the assistance of the manufacturer. When a serious leak occurs in the circuit breaker during operation, when the operation or maintenance personnel need to approach the equipment, pay attention to the approach from the windward direction. Wear a gas mask and protective clothing when necessary, and pay attention to the safety distance from the live equipment.

2. Rejection or closing speed is low

a The core of the closing iron core has a small stroke. When the suction is completed, the positioning member and the roller cannot be unlocked, and the iron core stroke is adjusted;

b Continuously perform the closing operation for a short time to make the coil heat up and the closing force is reduced;

c The auxiliary switch is not converted or has poor contact. Make adjustments and check if the contacts of the auxiliary switch are burnt. If there is burn, replace it.

d The closing spring is permanently deformed and the closing work is insufficient;

e Closing coil is broken or burned and should be replaced;

f The closing iron core is stuck and should be checked and adjusted to make it flexible.

g The sector plate is not reset or the clearance to the half shaft is too small (less than 1mm), because the opening is not in place or improperly adjusted, it should be readjusted;

h The amount of the buckle between the sector plate and the half shaft is too small, it should be adjusted within the range of 2~4mm, or the broken joint between the sector plate and the half shaft should be replaced;

I The sealing gear or the roller on the cam has a low heat treatment hardness and deformation, and should be replaced;

j The mechanism or the body is stuck, and it is necessary to carry out slow-motion inspection or disintegration inspection to find out the inflexible parts and re-adjust the adjustment;

k The circuit of the opening circuit is connected, that is, during the closing process, the opening coil has a current (the voltage exceeds 30% of the rated operating voltage), and the opening iron core is jacked up. At this time, it should be checked whether the secondary circuit wiring is faulty, and Correct the error;

l The power supply voltage drop is too large, and the voltage at the closing coil end does not reach the specified value. At this time, the power supply should be adjusted and the lead wire should be thickened;

m The control loop is not connected. Check the open circuit. If the lead wire at the terminal of the coil is not pressed and the contact is poor, check the problem and perform targeted treatment.

3, the speed of rejection or opening is low

a Thehalf shaft and the sector plate are improperly adjusted, and the buckle amount is too large (the buckle amount should generally be adjusted within the range of 2 to 4 mm);

b The auxiliary switch is not converted or has poor contact. Make adjustments and check if the contacts of the auxiliary switch are burnt. If there is burn, replace it.

c If the opening iron core is not completely reset or stuck, check whether there is any blockage in the assembly of the opening electromagnet. If it is excluded, it should be excluded.

d The disconnecting coil is broken or burned out and should be replaced;

e If the parameters of the opening circuit are not properly matched, the voltage at the opening of the coil will not reach the specified value and should be readjusted;

f The control loop is not turned on, check where the open circuit is, and then perform the processing.

g The mechanism or the body has a jamming phenomenon, which affects the speed of opening, can be slowly divided or disassembled, and reassembled;

h The pre-stretching length of the opening spring is not up to the requirement, and the pre-stretching length is adjusted appropriately;

I The brake spring fails and the opening function is insufficient, and the opening spring can be replaced.

4. The closing spring does not store energy or the energy storage is not in place.

a The automatic air switch of the control motor should be closed at the “minute” position;

b Check the control loop, if there is a wrong connection, open circuit, poor contact, etc., it should be targeted;

c Contactor contact is poorly contacted and should be adjusted;

d The travel switch is cut off too early, it should be adjusted, and check whether the travel switch contacts are burnt out, and there are burns to be replaced;

e Check the energy storage part of the organization, whether there is any jamming, poor cooperation, damage to parts, etc., if any, should be excluded.

5, water exceeds the standard (infiltration of water)

a replacement of the adsorbent;

b Vacuum, dry or replace SF6 gas.

Second, the disassembly process and requirements

1. The maintenance personnel wear a gas mask to discharge the SF6 gas in the circuit breaker (the released gas should be discharged through 10% NaOH aqueous solution), then vacuum, the absolute pressure should reach 133Pa, and then flush with nitrogen for 3 times, the inflation flush pressure 0.2 MPa (the gas is still discharged through the NaOH aqueous solution);

2. The maintenance personnel wear protective clothing and gas mask to open the SF6 load switch cover and temporarily evacuate the site for 30 minutes;

3. The maintenance personnel wear a gas mask or oxygen breathing apparatus and protective gloves to remove the adsorbent, use a vacuum cleaner and a brush to remove dust, and clean the metal and insulation with acetone;

4. Dispose of the waste until it is neutral (after immersing in 20% NaOH solution for 12 hours) deep burial;

5. After disassembly, mainly check the parts that are worn, burnt and corroded, replace fasteners, springs, insulation parts, aging seals, insulation parts, and replace the adsorbent (replacement of adsorbents and waste) (6) Properly dispose of in accordance with relevant regulations; (6) Re-clean all parts (using industrial alcohol), and send the insulation to the oven for drying at 80-100 °C for 4 hours, and the adsorbent is dried at 500-550 °C. After 2 hours of assembly, after assembly, according to the repair standard and customer's special requirements, the assembly should be prompt, and timely closure of the body;

6. After the end of the assembly, vacuum the pump to 133Pa, keep the vacuum pump running for more than 30 minutes, then stop the vacuum pump for 30 minutes, then read the vacuum value, then wait for more than 5 hours, read the vacuum value for the second time, two readings. The difference is not more than 65Pa, otherwise, find the leak point. When vacuuming, it is absolutely necessary to prevent it from being operated, so as to avoid causing vacuum pump backflow accident;

7. Dry the inflating pipe and charge qualified SF6 gas to the rated pressure (20 °C);

8. After inflating for 24 hours, the air leak rate is detected by an SF6 gas leak detector with a sensitivity of 10-8 atm.cm3/s. The annual air leakage rate is ≤1%, and the micro water content is ≤150PPm (20 °C). Pay special attention to Pipes, joints, valves, etc.;

9. After the circuit breaker is assembled, the main technical parameters shall meet the factory standards, and the mechanical characteristics and electrical performance tests shall be carried out according to the factory standards, and the factory shall be delivered after the factory requirements are met;

10. After the work is finished, clean the used protective equipment and the maintenance personnel should take a bath.

Third, disassembly and overhaul

1. When the following conditions occur, the SF6 load switch should be returned to the manufacturer for disassembly and overhaul.

2. The operation time of the circuit breaker has reached 10 years; after inspection, there are abnormal phenomena that seriously affect the safe operation of the equipment;

3. The number of operations has reached the number of mechanical life times specified by the circuit breaker;

4. The accumulated breaking current reaches the cumulative breaking value specified by the circuit breaker.

Operation and maintenance of four SF6 load switches

1. During the operation and maintenance of the SF6 load switch, the maintenance process and related maintenance procedures must be performed;

2. Inspection inspection in operation

a Check that the outer insulation part (porcelain sleeve) of the circuit breaker should be intact, without damage, dirt and flashover discharge;

b According to the temperature-pressure curve, observe that the pressure gauge (or the indicated density controller) indicates that it should be within the specified range, and record the pressure and temperature values ​​regularly;

c The branch and closing position indicators shall be indicated correctly, and the opening and closing shall be in place;

d The overall fastener should be free from looseness and falling off;

e There should be no abnormal noise inside the energy storage motor and circuit breaker;

f The circuit breaker's opening and closing coils shall have no burnt smell, smoke and burns;

g The circuit breaker grounding shell or bracket grounding should be good;

h The circuit breaker casing or operating mechanism box should be complete and free of rust;

I The circuit breaker should be free from damage, deformation and serious corrosion.

Five SF6 load switch maintenance considerations

1. The circuit breaker is not allowed to perform the split operation under vacuum condition to avoid damage to the components of the arc extinguishing chamber;

2. When the mechanism is in normal maintenance, the energy of the split and closing springs should be released.

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