7 Maimaituka na Bincike da Dukurin Karkashin Kwallon Kashi a Fara Iya Da Turanci Don Takaicewa Masu Kayan Aiki

1. Ingantaccen da Yawancin Haliyar Daɗiyya na Makaranta

A lokacin da mafi yawan daɗiyya na makaranta ya fara, haliyar daɗiyyarsa ya zama da ma'adani. Wannan nan, haliyar daɗiyyarsa tana da muhimmanci a zama kusa, kuma lokacin da shiga abin daɗiyya zai iya zama wata tsari mai mahimmanci don inganta. A wasu lokutan, daɗiyyar daɗiyya zai iya gane zuwa baya da ya sake yi, kuma za a fara daɗiyya daga bakwai. A halin daidai, daɗiyyar daɗiyya zai iya gane zuwa baya da ya sake yi, kuma za a fara daɗiyya daga bakwai. A halin daidai, daɗiyyar daɗiyya zai iya gane zuwa baya da ya sake yi, kuma za a fara daɗiyya daga bakwai. Saboda haka, ingantaccen da yawancin haliyar daɗiyya zuwa haliyarsa a makaranta ya zama wata muhimmancin dalilin shigowar abin daɗiyya. Dukan da aka fara da haliyar daɗiyya bayan shigowa da haliyarsa a makaranta suna da muhimmanci wajen neman daidaito da shigowar abin daɗiyya.

Don ingantaccen da yawancin haliyar daɗiyya, yana da kyau a kare da cututtuka da sauransu. Cututtuka suke da sabon irin waɗanda suke da uku: cututtuka masu siffar, cututtuka masu ruwan, da cututtuka masu ciwo.

• Cututtuka Masu Siffar: Dukkan abubuwa da za a shiga suka da kyau a sauƙa da kyau. Sauƙar da kyau ta haɗa a lokacin da ake amfani da rukunin mutanen jiki mai lafiya, ba a samu lashe ko abubuwa masu samun.

• Cututtuka Masu Ruwan da Ciwo (kawai ruwa): Tushen da ya fi daidai shine tushen kasa, wanda ana da biyu masu muhimmanci:

(1) Kasa da Kiyaye:

• Bayan da dukkan abubuwa an shiga, ake shiga takalma a kan kofin da ke cikin tanki. Aka buɗe dukkan kofin da ke cikin tanki saboda hakan, abubuwa masu (kawai kula), ba tankin da gas relay ba, za su kasance da tankin mai gaba.

• Aka shiga kofin kasa ko kofin standard a kan kofin da ke cikin tanki.

• Kabla da ake kasa tanki, ake buɗe kasa ga kungiyoyi kawai don neman adadin kasa da ake iya samun. Idan kasa ya kawo 10 Pa, ake duba kungiyoyi ko ake fada pumpa kasa.

• Jirgin tanki daidai a lokacin da ake kasa.

• Idan pumpa kasa ya samu adadin kasa da ya fi daidai (ba a kawo 133.3 Pa ba), ake ɗaukan pumpa kasa don inganta wannan adadin kasa. Pumpa kasa ya kamata a yi aiki har zuwa 24 awa.

(2) Shiga Ruwan da Kasa:

• A lokacin da ake shiga ruwan, ake ɗaukan pumpa kasa. Aka buɗe dukkan kofin da ke cikin tanki saboda hakan, abubuwa masu da tankin mai gaba za su shiga ruwan da kasa.

• Aka amfani da filter kasa. Ruwan ya kamata a shiga a kan kofin da ke cikin tanki, tare da ruwan ya fito daga bahaushe zuwa kasa, don kare ƙaramin cututtuka.

• Idan adadin ruwan ya zama kusan 200–300 mm daga kofin tanki, ake ɗauka kofin kasa da kaɗa kasa, amma ake ɗauka shiga ruwan da filter kasa.

• Idan babu on-load tap changers (OLTC), ake ɗauka shiga ruwan har zuwa lokacin da adadin ruwan ya zama kusan blanking plate gas relay.

• Idan akwai OLTC, ake ɗauka filter kasa idan insulating cylinder da selector switch ya shiga ruwan, don kare ɗauka switch daga tanki.

• Dukkan lokutan, ake ɗauka shiga ruwan da kasa saboda hakan, don kare adadin ruwa mai gaba. Idan ake ɗauka kasa da ake ɗauka shiga ruwan, kadan ruwa ne ke jiye zuwa kasa. Wannan ruwa zai kare ɗauka zuwa conservator, kuma ba zai iya ƙara daɗiyyar daɗiyya.

Yana da kyau a nuna cewa muhimmancinsa ya shafi ɗauka shiga ruwan da kasa; ba a iya amfani da shiga ruwan da kasa a lokacin da ake shiga ruwan da kasa. A lokacin da ake shiga ruwan da kasa, kawai ruwa da take fito daga paper insulation zuwa ruwan zai iya kare ɗauka da filter kasa. Amma ruwa da take fito a paper zai iya ƙara da kasa, kuma ƙaramin ruwan da paper zai iya ƙara da kasa.

2. Muhimmancin Shiga Ruwan

Shiga ruwan ita ce wata matsalolin da ake samu a cikin transformers. Dalilai suna da uku, da cututtukan da ake samu a cikin design da production suna da muhimmanci (misali, design da ba ake daidai, cututtukan da ake samu a cikin machining, ko kwalitoci da ba ake daidai). Cututtukan da ake samu a cikin installation da ake yi a wurin da ba ake daidai (misali, cututtukan da ake samu a cikin cleaning da flange surfaces, presence of oil, rust, weld spatter; aged gaskets with lost elasticity; uneven flange mating surfaces not corrected).

Muhimmancin shiga ruwan ya kamata aiki da kyau:

• Kabla da ake shiga, ake buɗe test sealing pressure ga coolers, conservators, risers, da oil purifiers, kuma ake ɗauka repair any leaking parts.

• Aka duba da prepare all flange sealing surfaces. Any misalignment during lifting must be corrected before installation; serious cases should be addressed jointly with the manufacturer.

• Ba da shiga, ake buɗe test sealing overall: apply no more than 0.03 MPa pressure on the tank cover for 24 hours, with no oil leakage allowed.

3. Test Partial Discharge

Test partial discharge (PD) ita ce wata test induced voltage withstand da PD measurement capability. According to GB 50150-91:

• Partial discharge tests are recommended for 500 kV transformers.

• For 220 kV and 330 kV transformers, PD tests are recommended if testing equipment is available.

Although the test voltage for PD testing is lower than that of standard induced voltage tests, the duration is extended by over 60 times. Combined with sensitive instruments monitoring internal discharge development, the destructive potential is controllable. Thus, PD testing combines characteristics of both non-destructive and destructive tests, effectively detecting insulation defects. As a result, it has gained rapid popularity. Most project owners now perform PD tests on newly installed or overhauled transformers, achieving significant benefits—early detection of installation flaws, identification of unstable factory PD performance, and ensuring successful initial energization.

4. Impulse Closing Test at Rated Voltage

The impulse closing test at rated voltage is primarily intended to verify whether the magnetizing inrush current generated during energization will cause the transformer differential protection to operate. It is not designed to test the insulation strength of the transformer.

In fact, during the impulse closing test, aside from relay protection monitoring, there are no instruments to detect possible overvoltages, and no measurable data is recorded. Therefore, from the perspective of insulation assessment, the test lacks conclusive value and is essentially meaningless.

That said, insulation failures in transformers have occurred during impulse closing tests—usually due to pre-existing serious defects that become apparent immediately upon energization. Conversely, there are numerous cases where transformers passed five impulse closures without issue, yet failed (burned out) within minutes to days after commissioning.

5. Insulation Condition Assessment

Insulation condition assessment includes measuring insulation resistance, absorption ratio, polarization index, DC leakage current, and dielectric loss tangent (tan δ).

After installation, the transformer’s insulation condition may have deteriorated to varying degrees compared to factory conditions, and measurement methods between site and factory may differ. Therefore, when comparing commissioning test results with factory data, comprehensive analysis is required to make accurate judgments. These results should also serve as a baseline for future preventive testing.

It is particularly important to note: when insulation resistance is very high, the absorption ratio may decrease. In such cases, an absorption ratio below 1.3 should not automatically be attributed to moisture in the insulation.

6. Understanding and Function of the Breather

If the bladder in the conservator is analogous to the lung, then the breather acts as the nose. When load or ambient temperature increases, causing the oil in the tank to expand, the bladder "exhales" through the breather to prevent excessive pressure. Conversely, it "inhales" to prevent vacuum formation in the tank. If the breather becomes blocked, minor consequences include false oil level indications; severe cases may trigger gas relay or pressure relief device operation, leading to accidents.

Breather blockage can occur not only if the shipping seal is forgotten to be removed but also during operation due to:

• Moisture absorption and degradation of the desiccant (color-changing silica gel)

• Accumulation of dust in the oil cup

Therefore, two maintenance tasks are essential:

• Ensure the silica gel in the breather has sufficient moisture-absorbing capacity and prevent saturation. Replace or regenerate the silica gel when 1/5 of it has changed color.

• Regularly clean the oil cup, refill with clean oil, and maintain the oil level above the air baffle to ensure incoming air passes through an oil bath, filtering out dust particles.