First, the operation and maintenance of SF6 circuit breaker
1. During the operation and maintenance of the SF6 circuit breaker, it must be observed that the DL/T 639-1997 SF6 electrical equipment safety, operation, and maintenance personnel's safety precautions shall be observed.
2. Inspection during operation
1) Inspect the external insulation (porcelain sleeve) of the circuit breaker should be intact, no damage, dirt and flashover discharge;
2) According to the temperature-pressure curve, observe that the pressure gauge (or indicator density controller) should be within the specified range, and record the pressure and temperature values ​​periodically;
3) The indicator of the position and closing position should be correct, and the points should be in place;
4) The overall fastener should be free from loosening and shedding;
5) There should be no abnormal sound inside the energy storage motor and circuit breaker;
6) The split and closing coils of the circuit breaker should be free of burnt smell, smoke and burns;
7) The circuit breaker grounding enclosure or bracket grounding should be good;
8) The circuit breaker shell or operating mechanism box should be complete and free from corrosion;
9) The circuit breakers shall be free from damage, deformation, and severe corrosion.
3, SF6 circuit breaker operation and maintenance
1) Annually carry out anti-corrosion treatment and replenishment on the rusted part of the shell;
2) The lubrication of circuit breakers and transmission parts should be lubricated on a regular basis (once every six months), and operation should be performed 3 times;
3) Qualitative leak detection of all sealing surfaces of the circuit breaker once every two years, there should be no leakage point above 10-6 atm.cm3/s;
4) The SF6 gas trace moisture test should be conducted once a year. The test result should be controlled against the moisture-temperature curve and should not exceed 300ppm (20°C);
5) Other items, such as insulation, operation tests, etc., may be periodically performed in accordance with relevant regulations, and the test results shall comply with relevant standards.
6) Inspection Precautions
(1) Circuit breakers are not allowed to operate in a vacuum state to avoid damage to the arc extinguishing chamber parts;
(2) The mechanism shall release the energy of the split and closing springs during normal maintenance.
4. When overhauling, the main technical parameters should meet the requirements of Table 1:
Table 1
Second, the possibility of failure analysis and maintenance
1, leak analysis and processing (density relay signaling)
1) Density relay signaling
(1) An error occurs in the value of the density relay's action value, and the signal is erroneously sent out. Adjust or replace it. If the secondary connection fails, find the error point and correct the wiring.
(2) The circuit breaker body leaks, finds the cause of the leak, and then performs the processing.
2) When the SF6 gas normally leaks to the density relay to signal, it can press SF6 gas pressure-temperature curve to make up the air to bring it to the rated pressure; when the replenishment gas is replenished, it can be carried out under the live running state.
3) When the pressure of SF6 gas rapidly drops or zero gauge pressure occurs, the operation should be immediately exited; and analyze whether the leak is due to the following reasons:
(1) There is a problem with the quality of the welded part and the weld leaks;
(2) Leakage of the casting surface (pinhole or trachoma);
(3) The Bolts and threads of the seal aging or sealing area are loose;
(4) Leakage at the gas line connection;
(5) Leakage of pressure gauges or density relays should be replaced.
Find out the specific cause of the leak and perform the inspection with the help of the manufacturer.
Note: When there is a serious leakage fault in the circuit breaker during operation, when the operation or maintenance personnel needs to approach the equipment, attention should be paid to the approach from the windward direction. If necessary, a gas mask and protective clothing should be worn and the safety distance from the live equipment should be taken into account.
2. The speed of rejection or closing is low
1) When the closing iron core has a small stroke, the positioning member and the roller can not be unbuckled and the core stroke can be adjusted.
2) Continuous closing operation for a short time so that the coil heats up and the closing force is reduced;
3) The auxiliary switch is not switched or has poor contact. Adjust it and check if the contacts of the auxiliary switch are burned. Replace the burned one.
4) Permanent deformation of the closing spring and insufficient closing power;
5) The closing coil is broken or burned and should be replaced;
6) The closing iron core is stuck and should be checked and adjusted to make it flexible;
7) The sector plate is not reset or the gap with the axle is too small (less than 1mm). The reason is that the gate is not in place or adjusted improperly and should be readjusted;
8) The buckle connection between the sector plate and the half shaft is too small and should be adjusted in the range of 2 to 4 mm, or the damage of the buckled joint between the sector plate and the half shaft should be replaced;
9) The heat treatment on the closing locator or the cam on the cam is low in hardness and deformed and should be replaced;
10) The mechanism or the body has a stuck phenomenon, and it is necessary to perform a slow-motion check or a disassembly check to find out where the inflexible part is re-adjusted;
11) In the sub-gate circuit string, that is, during the closing process, the sub-coil has current (its voltage exceeds 30% of rated operating voltage), and the sub-gate core is lifted up. At this time, check whether the secondary circuit wiring is faulty. And correct mistakes;
12) If the power supply voltage drop is too large, the voltage of the closing coil terminal cannot reach the specified value. At this time, the power supply should be adjusted and thickened;
13) If the control circuit is not connected, check for any open circuit. If the lead wire at the terminal of the coil is not tight and the contact is poor, etc., identify the problem and perform targeted processing.
3, Rejection or opening speed is low
1) The adjustment of the half shaft and the sector plate is improper, and the buckle quantity is too large (the buckle quantity should generally be adjusted within the range of 2 to 4 mm);
2) If the auxiliary switch is not switched or has poor contact, adjust it and check if the contacts of the auxiliary switch have burned and burned.
3) If the sub-gate core is not fully reset or has stuck, check whether the sub-gate electromagnet assembly is blocked, and if so, remove it;
4) Disconnected coil or burnout should be replaced;
5) When the parameters of the sub-gate circuit are not properly matched, the voltage of the sub-gate coil terminal cannot reach the specified value, and it should be readjusted;
6) The control loop is not turned on, check the open circuit, and then perform the processing.
7) The mechanism or the body has a jamming phenomenon, which affects the opening speed, and can be divided or disassembled and reassembled.
8) The pre-stretching length of the opening spring does not meet the requirements, and the pre-stretching length is properly adjusted;
9) The gate spring fails, and the gate power is insufficient. The gate spring can be replaced.
4, closing spring does not store or store energy is not in place
1) The automatic air switch of the control motor shall be closed at the "minute" position;
2) Check the control loops for errors, disconnections, and poor contacts.
3) Poor contact of the contactor should be adjusted;
4) The trip switch is cut off too soon, should be adjusted, and check the trip switch contacts are burned out, there are burns to be replaced;
5) Check the energy storage part of the organization, whether there is jamming, poor fitting, or broken parts, etc. If any, remove it.
5, moisture exceeding the standard (infiltration of water)
1) Replace the adsorbent;
2) Vacuum, dry or replace SF6 gas.
Third, dismantling maintenance protection
1. When the following conditions occur, SF6 circuit breaker should be returned to the manufacturer for disassembly and overhaul
1) The operating time of the circuit breaker has reached 10 years; after the inspection, there are abnormal phenomena that seriously affect the safe operation of the equipment.
2) The number of operations has reached the number of mechanical life specified by the circuit breaker;
3) The cumulative breaking current reaches the cumulative breaking value specified by the circuit breaker.
4) Note: The judgment of the abnormal phenomenon and the cumulative breaking value can refer to the manufacturer's diagnosis instructions.
2, dismantling repair process and requirements
1) When the circuit breaker is dismantled and overhauled, care should be taken to ensure that the maintenance environment is clean, dry, and well-ventilated. The necessary protective measures such as gas masks, protective clothing and protective gloves should be provided. There should be SF6 gas and chemical waste treatment equipment and measures.
2) Procedures (Specific requirements are detailed in "DL/T639-1997 Safety Measures for Operation, Test and Repair of Sulphur Hexafluoride Electrical Equipment")
(1) Maintenance personnel wear gas masks to release SF6 gas from the circuit breaker (the discharged gas should be discharged through 10% NaOH solution), then vacuum, the absolute pressure should reach 133Pa, and then flush with nitrogen 3 times. Pressure 0.2MPa (gas is still discharged through NaOH solution);
(2) After the maintenance personnel wears protective clothing and gas masks to open the SF6 circuit breaker cover, temporarily evacuated the site for 30 minutes;
(3) The maintenance personnel wear gas masks, oxygen respirator and protective gloves to remove the adsorbent, remove the dust with a vacuum cleaner and a brush, and clean the metal and insulating parts with acetone;
(4) Demolition of the waste after disposal to neutrality (after soaking in 20% NaOH solution for 12 hours);
(5) After the dismantling, the main parts are to replace the parts that have worn out, burned and corroded more severely, replace the fasteners, springs, insulation parts, aging seal rings, insulation parts, and replace the adsorbent (replacement of the adsorbent and waste Things should be properly handled according to relevant regulations), etc.;
(6) Re-clean all parts (using industrial alcohol). Insulation parts are sent to the oven and baked at 80-100°C for 4 hours. Then the adsorbent is assembled after drying at 500-550°C for 2 hours. After that, the parts are repaired. Standards and customer special requirements for assembly, assembly should be rapid, and timely closure of the body;
(7) After the entire assembly is completed, vacuum is then applied to 133Pa to maintain the vacuum pump for more than 30 minutes. Then the vacuum pump is stopped after 30 minutes of observation to read the vacuum value, and then wait for more than 5 hours to read the vacuum value for the second time. The difference between the readings is not more than 65Pa. Otherwise, find the leak point. Absolutely prevent the operation when vacuuming, so as to avoid vacuum pumping accident;
(8) Dry the air-filled pipe and fill it with qualified SF6 gas to the rated pressure (20 °C);
(9) After inflating for 24 hours, use the SF6 gas leak detector with a sensitivity of 10-8 atm.cm3/s to measure the leakage rate. The required annual leakage rate is ≤ 1%, and the micro water content is ≤150PPm (20 °C). Pay attention to pipes, fittings, valves, etc.
(10) After the circuit breaker assembly is completed, the main technical parameters shall reach the factory standards, and the mechanical characteristics and electrical performance tests shall be performed according to the factory standards.
(11) The used protective equipment will be cleaned after the work is completed and the maintenance personnel should take a bath.
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