Karkashin Maye da Karkashin Gashi SF6 a Circuit Breakers

Kwakwalwa a Mafi Girmanin Karkashin Maye

Don karkashin maye, kwakwalwa zai iya ba da tushen fasahar pumpi ko lokacin faduwar gaba-gaban kisa ga wasu lokaci. Kwakwalwa mai yawa a cikin valves zai iya ba da kawo masu kisan kisa. Idan oil ya kasa a tsakiyar nitrogen ta accumulator cylinder, zai iya ba da kusa da kisan kisa, wanda ke taimaka wa kula da kisan amfani da SF6 circuit breakers.

Saboda harsuna da kisan kisa da abubuwan da suka shafi kisan kisa, da kuma harsuna da kisan kisa da sababbin halittuwar solenoid coils, first-stage valve push rods, ko auxiliary switch signal issues, duka abubuwan da suka shafi kisan kisa suna da shi ne saboda kwakwalwa—kafin kusan kisa da nitrogen.

Abubuwan da ake fi sani da kusan kisa a karkashin maye sun hada da: three-way valves da drain valves, high/low-pressure oil pipes, joints of pressure gauges and pressure relays, damaged seals at piston rods of working cylinders and accumulator cylinders, and sand holes in low-pressure oil tanks.

(1) Kwakwalwa a joints na pipe da high/low-pressure oil lines, pressure gauges, and pressure relays

Kwakwalwa a joints na pipe tana da muhimmanci sosai a dukkan abubuwan da suka shafi kisan kisa, kusan 30%. Oil pipes da joints sun samun sealing da "ferrules". Idan accuracy na machining, strength na tightening, ko burrs a connection, ba daidai ba, zai iya ba da kwakwalwa. A lokacin bincike, koyi joint ita da koyi; idan kwakwalwa yake daɗe, koyi oil pipe ita da koyi da kuma saukar da shi daidai. Tightening torque a lokacin assembly ba zai iya zuwa sosai ko kadan don ba daidai ferrule—koyi kawai har zuwa lokacin da ba za a koyi oil seepage ba.

(2) Kwakwalwa saboda sealing da ba da shiga

Karkashin maye suna amfani da nau'o'i biyu na sealing: rigid sealing da elastic sealing. Elastic sealing sun hada da:

• "O"-ring rubber seals, wadannan sun amfani da elastic deformation don static ko dynamic sealing a flat ko circular surfaces.

• "V"-type seals, wadannan suna da direction—the open side of the "V" must face the high-pressure side.

Idan quality ko installation da ba da shiga, burrs a piston rods, contaminants a oil, ko wear a lokacin movement, zai iya ba da sealing failure. Insufficient compression, aging, ko damage suna da shi ne saboda kwakwalwa. Idan wannan conditions an samu, sealing should be replaced.

(3) Kwakwalwa a valve body seal

Sealing a mating surfaces of valves such as three-way valves and drain valves mostly uses rigid sealing, typically achieved through valve line sealing. For example, ball valves rely on tight contact between a steel ball and the valve seat for sealing, while conical valves depend on tight fit between the conical surface and the valve port.

Main causes of leakage at valve mating surfaces include: poor sealing fit accuracy, excessive surface roughness and flatness errors, poor machining precision, presence of impurities at the mating surface during assembly or operation, leading to damage of the sealing surface.

Handling methods:

• Remove burrs from relevant components;

• If the hydraulic oil is dirty or substandard, replace or filter it;

• For faulty ball valve seals, reassemble carefully—the sealing surface should not be too wide, and a new, high-precision steel ball must be used;

• For poor conical seals, carefully lap and repair;

• If seal wear is severe and irreparable, replace the entire component.

(4) Kwakwalwa a housing

Housing leakage usually results from defects in castings or welds that expand under pressure shock from the hydraulic system. For example, if there is seepage at the welds of oil tanks or nitrogen cylinders (accumulators), welding repair is required.

(5) SF6 Gas Replenishment

Before charging SF6 circuit breakers, qualified SF6 gas should be used to purge the charging pipeline for 5 seconds to remove air inside the pipeline. During operation, ensure cleanliness of the charging interface. In high humidity conditions, an electric hot air blower may be used to dry the interface. Ideally, adjust the charging pressure to be nearly equal to the internal SF6 pressure in the circuit breaker before connecting the charging hose. The pressure difference should generally be less than 100 kPa. Direct high-pressure charging without a pressure reducer is prohibited. The pressure of the gas charged into the circuit breaker should be slightly higher than the specified value to compensate for gas consumed during future moisture measurements.

(6) SF6 Gas Moisture Detection

The moisture content in SF6 gas significantly affects the arc-quenching performance, insulation strength, and service life of electrical equipment. When moisture exceeds limits, toxic or corrosive compounds may form under high temperatures during arcing, corroding metal components inside the arc chamber and potentially causing circuit breaker explosion.

Therefore, moisture measurement should be conducted 24 hours after SF6 gas is filled into the equipment. Before measurement, check that the internal SF6 gas pressure is slightly above rated pressure. Measurements should be taken during dry weather with low ambient humidity, using dedicated pipelines, typically no longer than 5 meters. The measurement pipeline must be flushed with dry nitrogen or qualified new SF6 gas before measurement.

(7) SF6 Gas Leak Detection

Common leak locations on SF6 circuit breakers include: drive rods and scratched seals in support insulators, poor sealing at charging valves, cracks at the base of porcelain supports, flange connections, sand holes at the interrupter cover, triple-box cover plates, gas piping joints, density relay interfaces, secondary pressure gauge joints, welds, and mismatch between sealing grooves and seals (gaskets).

Before testing, blow away any surrounding SF6 gas. Then slowly move the leak detector probe 1–2 mm above the test point. Under normal conditions, the detector needle remains stable. If the needle fluctuates and residual gas is suspected, blow air to disperse it for 1 hour and then continue measuring.