Vigezo Viwili vya Msimbo kwa Utengenezaji na Uanzishaji wa GIS

Hii ni kifungu kidogo kinachoelezea faida na sifa za teknolojia za vifaa vya GIS (Gas-Insulated Switchgear), na kuelezea muktadha muhimu ya kudhibiti ubora na hatua za kudhibiti mtazamo wakati wa uwekezaji wa majengo. Linastahimili kuwa majaribio ya kutahama nyuzi zinaweza kupendekeza tu sehemu chache ya ubora muundo na kazi ya uwekezaji wa vifaa vya GIS. Tangu tu kupunguza udhibiti wa ubora kamili kote katika mchakato wa uwekezaji - hasa katika maeneo muhimu kama mazingira ya uwekezaji, upimaji na matumizi ya absoventi, matumizi ya gas chamber, na utafiti wa umwagiliaji wa silaha - tunaweza kuaminika kusaidia uwekezaji wa GIS kuwa salama na safi.

Kutokana na maendeleo ya mifumo ya umeme, viwango vyenye urefu zaidi vilivyotolewa kwa burudisho na ufanisi wa vifaa vya kiwango cha awali. Kwa sababu hiyo, vifaa vya umeme vya kiwango cha juu zinafanyika zaidi katika steshoni za umeme. Katika hizi, Gas-Insulated Metal-Enclosed Switchgear (GIS) inapata utumi zaidi kutokana na faida nyingi zake. Kwa hiyo, uwekezaji wa GIS na kufanya kazi yake imekuwa muhimu kwenye kujenga steshoni za umeme.

1. Sifa za Teknolojia za Vifaa vya GIS

• Muundo mdogo unaotumia ukuta ndogo

• Ufanisi wa kazi unaoaminika na ustawi wa usalama mzuri

• Inaondoka athari mbaya za nje

• Muda mfupi wa uwekezaji

• Usafi rahisi na muda mrefu wa kutathmini

2. Muktadha Muhimu ya Kudhibiti Mtazamo na Hatua za Kudhibiti katika Uwekezaji wa GIS

Kwa sababu ya integretioni ya juu na muundo wa kimbo wa vifaa vya GIS, chochote kilichoondokeka wakati wa uwekezaji katika majengo linaweza kuongeza hatari yenye kuburudisha vifaa au hata ajali za grid. Kulingana na tajriba kutokana na uwekezaji wa GIS nyingi, dharura ya kudhibiti vibaya kifuatacho ni muhimu wakati wa uwekezaji na kufanya kazi.

2.1 Kudhibiti Mazingira ya Uwekezaji

Chane chemchemi SF₆ ni sensitive sana kwa maji na vitu vinavyovunjika, kwa hiyo mazingira ya uwekezaji ya majengo yanapaswa kukudhikisha. Kwa sababu gas chambers yanapaswa kufunguliwa wakati wa uwekezaji, kazi inapaswa kutekelezwa tu wakati wa joto la siku na ujanja wa mazingira unapaswa kuwa chini ya 80%. Mara moja chamber imewekwa kufunguka, kazi ya vacuum processing inapaswa kuanza mara moja ili kuchukua muda mfupi. Kwa uwekezaji wa nje, mwanga unapaswa kuwa chini ya Beaufort scale 3. Ikiwa lazima, hatua za kuokoa chini ya eneo limelipatikana linapaswa kutumika, na kutengeneza chane chemchemi ndani ya eneo lisalama linapaswa kukudhikisha. Eneo la uwekezaji linapaswa likae sauti na kijani.

Wanawekezaji wanapaswa kuwa na nguo zenye mikono na saruji isiyokuwa na fibra zinazofunguka. Nywele zinapaswa kufunika kwa kofia, na mask ya uso inapaswa kutumika. Katika masharti ya joto, hatua za kutengeneza chane chemchemi zinapaswa kutumika ili kuzuia maji kutokana na machozi kutempuka katika chamber.

2.2 Matumizi ya Absoventi katika Gas Chambers za GIS

Absoventi zinatumika katika GIS ni 4A molecular sieve, ambayo ni isiyokuwa na mawasiliano, na dielectric constant ndogo, na isiyokuwa na chane chemchemi. Ina uwezo mkubwa wa kuhifadhi na inaweza kushiriki joto na arc exposure. Absoventi inapaswa kukusanya katika chombo cha vacuum drying oven kwa maji 200–300°C kwa masaa 12. Mara moja baada ya kukusanya, inapaswa kutengenezwa na kuiweka katika chamber kwa dakika 15. Chamber iliyopewa absoventi inapaswa kuanza kazi ya vacuum processing mara moja ili kuchukua muda mfupi.

Kabla ya uwekezaji, absoventi inapaswa kutathmini na kurekodiwa kwa tarehe ya baadaye ya huduma. Ikiwa uzito unategemea zaidi ya 25% wakati wa utafiti, inamaanisha kwamba imetegemea maji mengi na inahitaji kutengenezwa tena. Absoventi kutoka kwenye arc-extinguishing chambers haipaswi kutengenezwa tena.

2.3 Kazi ya Vacuum Processing ya Gas Chambers

Kazi ya vacuum processing inapaswa kuanza mara moja baada ya uunganishaji wa chamber. Valve ya kuhakikisha inapaswa kutumika katika pipeline iliyohusiana, na mtu anayejitahidi kudhibiti mchakato ili kuzuia pump oil kutembelea nyuma katika chamber ikiwa kuna kosa la umeme. Pump ya vacuum inapaswa kuanza kwanza ili kuthibitisha kazi sahihi kabla ya kufungua valves zote za pipeline. Waktu kusimamia, valves zinapaswa kufunga kabla ya kusimamia pump.

Baada ya kupata pressure ya ndani chini ya 133 Pa, pump ya vacuum inapaswa kusambaza kwa dakika 30, kisha kusimamia na kusimamia. Absolute pressure (PA) inarekodiwa baada ya dakika 30 ya kusimamia. Baada ya muda tofauti wa 5 saa, pressure (PB) inapakuliwa tena. Chamber inapata kuwa well-sealed ikiwa PB – PA < 67 Pa. Tu baada ya kupita hii test ya seal, SF₆ gas inayokuwa qualified inapaswa kupelekwa katika chamber.

Katika mchakato wa vacuum processing, vigeuze masharti ambapo side moja ya insulator ya disk-type (insulator ya disk) ina pressure ya rated operating, na side nyingine ina high vacuum, kwa sababu hii inaweza kusababisha damage ya mekanikal. Ikiwa lazima, reduce pressure katika side ya pressurized chini ya 50% ya thamani ya rated.

2.4 Enclosure Grounding

Kwa sababu ya muundo wa kimbo wa GIS, electrical clearance kati ya conductors na kati ya conductors na metal enclosure ni chache. Ikifika breakdown na ndani, current kali ya fault zitatemeka kwa grounding conductors kwenye grounding grid. Pia, kwa sababu GIS enclosure ni ya metallic material ya looped, system faults asymmetrical zinaweza kuleta voltages kubwa katika enclosure kwa sababu ya magnetic induction, ambayo inaweza kusababisha damage ya vifaa au kusababisha hatari kwa watu.

Kwa hiyo, kazi ya grounding inapaswa kufanikiwa kwa viwango vya juu. Steshoni za umeme zinazotumia GIS zinapaswa kutumia copper grounding grids ili kukusanya resistance ya grounding kamili. Vitambatano vyote kati ya enclosure na grounding grid pia yanapaswa kutumia copper materials. Kwa sababu ya presence ya disk-type insulators na rubber seals kati ya gas chambers, bonding copper bars yanapaswa kutengenezwa kati ya enclosures. Cross-sectional area ya bonding bars hizi yanapaswa kuwa sawa na ya main grounding grid.

GIS hutumia multiple-point grounding scheme. Idadi na mahali pa grounding points yanapaswa kufuata maagizo ya manufacturer na design specifications.

2.5 Main Circuit Resistance Testing

Utafiti wa resistance ya main circuit ni muhimu katika uwekezaji wa GIS. Hii si tu inathibitisha integrity ya contact connections kati ya modules, bali pia inathibitisha phase sequence sahihi ya main busbar. Kwa switchgear zilizofungwa sana, phase sahihi na majengo ya thamani ni muhimu sana. Katika ufaao, rework imekuwa inafanyika kwa sababu ya phase sahihi au majengo ya thamani yasiyofaa.

Manufacturers mara nyingi hupeleka standard values za contact resistance kwa internal connections. Loop resistance inapaswa kutathmini kwa section kwa section wakati wa assembly, ili kutambua mapema na kusindikiza contacts zisizofaa. Resistance iliyopimwa kwa kila section haipaswi kuwa zaidi ya sum ya maagizo ya manufacturer kwa saba connections zote zilizowekwa katika section hii.

Baada ya assembly kamili, utafiti kamili wa loop resistance unapaswa kutathmini, na matokeo hayo haipaswi kuwa zaidi ya theoretical calculated value.

Special Note: Utafiti wa loop resistance haipaswi kutathmini chambers zinazokuwa zinapewa vacuum processing. Kwenye sub-atmospheric pressure, dielectric strength ndani ya chamber ni chache sana. Hata volts kadhaa tu zinaweza kusababisha surface discharge kwenye disk-type insulators, kutengeneza discharge traces zinazokuwa weak insulation points na potential fault sources wakati wa kazi. Kwa hiyo, checks zinapaswa kufanyika kwa kina kabiliana na resistance measurement yoyote ili kuzuia testing katika chambers zilizokuwa zinapewa vacuum.

2.6 Withstand Voltage Test

Properties nzuri za insulation za SF₆ zinaweza kusaidia GIS kupata muundo wa kimbo. GIS hutumia grounded aluminum alloy enclosures, na kwenye operating pressure, gap kati ya conductors ndani au kati ya conductors na grounded enclosure ni chache. Kwa sababu ya factory pre-assembly ya juu, components muhimu zinatumika zinapewa zilizosambazwa. Lakini, component displacement wakati wa transport au introduction ya tiny impurities wakati wa uwekezaji wa majengo kunaweza kusababisha distortion ya electric field distribution ndani. Kama porcelains-insulated equipment, even minor burrs or particles in GIS interrupters can cause abnormal discharge or breakdown.

Kwa hiyo, on-site withstand voltage testing serves as the final defense to verify GIS performance and installation quality.

According to acceptance test regulations, the on-site test voltage is 80% of the factory test voltage. For example, for a 110 kV GIS, the main circuit withstand test voltage is 80% of the factory test voltage: 230 kV × 80% = 184 kV, applied for 1 minute. The test should be conducted at least 24 hours after complete gas filling. Surge arresters and voltage transformers should not be included in the test. High-voltage outgoing cables should be tested together after being connected to the GIS. Before the test, insulation resistance should be measured and confirmed satisfactory.

Test Procedure: Increase voltage at a rate of 3 kV/s to the rated operating voltage (63.5 kV), hold for 1–3 minutes to observe equipment status, then raise to 184 kV and maintain for 1 minute. Repeat this procedure for each phase.

GIS that passes the withstand voltage test may be put into service. However, this test cannot detect all potential defects. In service, GIS must withstand not only power-frequency voltage but also lightning and switching overvoltages. The breakdown field strength of SF₆ gas varies with voltage type. For coaxial cylindrical electrode systems, the 50% breakdown voltage of SF₆ can be empirically expressed as:

U₅₀ = (AP + B)μd

Where:
P — Chamber pressure
d — Electrical clearance (mm)
μ — Electric field utilization factor
A, B — Constants dependent on voltage waveform

Thus, breakdown voltage varies with voltage type and polarity. Different internal defects exhibit different sensitivities to various voltage waveforms. Power-frequency AC voltage is sensitive to insulation breakdown caused by moisture, impurities, or metal particles in SF₆, but less sensitive to surface scratches or poor conductor surface conditions.

Therefore, power-frequency withstand tests cannot detect all internal defects. Enhancing process controls during installation and improving overall installation quality remain the most important measures to ensure safe GIS operation.

3. Conclusion

This paper analyzes key process and quality control points in the on-site installation and commissioning of GIS equipment. It demonstrates that on-site withstand voltage testing can only partially reflect the overall quality and workmanship of installed GIS. More importantly, it highlights that only through strict control of every installation process—ensuring full compliance with procedures and work instructions—can GIS equipment be safely and reliably commissioned from the outset.

It is hoped that this summary may serve as a useful reference for colleagues in the power construction industry.