Mfuko wa Insuliti ya Porcelene ya Mikoa inayofanikiwa kwa Miongozo ya IEE-Business: Usimamizi wa Uvunjishaji wa Impulse ya Mwanga wa Mstari wa Juu na Uchanganuzi

Vidole na porceleni na nguo na vidole za kifaa cha kivuli vya kifaa cha kivuli vya kiwango cha kutosha katika uwezo wa kutosha wa kivuli na nguvu ya kimikakia, lakini yana athari ya kuwa na changamoto za kutosha kwa wakati wa kupata majonzi. Hii inaweza kukatia matumizi ya mawasiliano ya umeme. Kufanikiwa kupunguza changamoto za kutosha kwa vidole vingineko, wafanyabiashara wanatumia nyevu ya silicone rubber (RTV) yenye uwezo mkubwa wa kutokutana na kutokutana na maji, kwa sababu ya kutoa vidole vya kivuli, kwa hivyo kupunguza hatari ya kutosha. Tangu mwanzo, RTV vya China vilikuwa vinavyofanyika mahali pamoja, njia inayojumuisha uchunguzi wa kutosha na usawa wa kutosha.

Baada ya hii, miundombinu ya utengenezaji kwenye vituo vilivyofanyika, kama vile kuchemsha au kuspraya, zilizinduliwa, kwa hivyo kunawezekana kutuma vidole vya RTV kama bidhaa kamili zinazotathmini na kutambuliwa, kwa hivyo kuongeza ubora wa bidhaa na kupromota matumizi yake kwa urahisi katika mitandao ya umeme. Lakini, RTV vya kivuli vina nguvu ya kimikakia chache na upana wa kutosha wa kivuli, kwa hivyo vinaweza kupata malipo kwa wakati wa usafiri, ukomitishia, ukoloni, na matumizi ya muda mrefu. Matukio ya kumaliza kama kuvunjika, kuvunjika, na kuvunjika ni yanayosimamishwa, yanayohitaji kutumia tena na kurekebisha, kwa hivyo kutengeneza gharama za matumizi.

Vidole vya disc suspension composite porcelain vyanzishwa kwa kutumia vidole vya porceleni kamili kama msingi, na kuvaa nguo ya high-temperature vulcanized silicone rubber (HTV) - uzito wa chini 3 mm - kwa kutumia mbinu moja ya kutengeneza kwa kutumia joto. Ingawa HTV, imeonyesha nguvu ya kimikakia inayobofya, na ufanisi unayobofya katika kutosha, kupungua, kutosha, viwango vya umeme, kupungua, na kutumia joto.

Kwa kuongeza, kwa kutumia nguo ya glaze kwenye uso wa porceleni na kutumia coupling agents maalum, upana wa kivuli kati ya porceleni na HTV silicone rubber unaongezeka, kwa hivyo kuongeza integriti na uniformity ya kitu. Kwa hivyo, vidole vya disc suspension composite porcelain vina nguvu ya kimikakia na ufanisi wa kupunguza kutosha kwa matumizi na matumizi nyingi, kufungua njia mpya kwa matumizi ya kivuli vingineko katika mzunguko wa umeme.

Utafiti unatoa taarifa kwamba wakati mzunguko wa umeme unapatikana na majonzi, overvoltage inayoletwa ina impulses yenye mstari wa juu sana, muda mfupi, na voltage peak sana, kwa hivyo kuwa na changamoto kwa vidole vya mzunguko. Impulses hizi zinaweza kuchanganya au kuchanganya vidole vya disc, na katika mabadiliko makuu, kunaweza kupeleka kwa kutumia mzunguko na kutumia mzunguko. Uwezo wa kudhibiti impulse steep-front ni muhimu katika ufanisi wa vidole.

Ingawa utafiti umefanyika sana kuhusu performance ya wave steep ya vidole vya porceleni na vidole vya glass, utafiti wa vidole vya disc suspension composite porcelain vimekuwa chache, na masharti yao yanayoweza kutambuliwa yamekuwa chache. Kwa hivyo, makala hii inafanya majaribio ya kudhibiti breakdown ya impulse kwenye vidole vya disc suspension composite porcelain ili kutafuta vipengele vya breakdown ya wave steep.

Majaribio ya impulse breakdown ya hewa yanaweza kutathmini ufanisi wa kudhibiti wave steep wa vyombo vya umeme, hususan kutathmini usalama na uwepo kwa muda, na kwa hivyo kunaweza kutumia matumizi ya kutosha katika ufanisi wa vidole. Utafiti huu unafanya majaribio ya kudhibiti breakdown ya impulse kwanza kutathmini ufanisi wa wave steep, basi kutengeneza simulasi ya distribution ya electric field kwenye voltage peak ya wave steep kwa kutumia matokeo ya majaribio ili kutafuta sababu za mabadiliko ya ufanisi, kwa lengo la kutumaini kwa kutosha kwa vidole vya composite porcelain katika mzunguko wa umeme.

1 Air Impulse Breakdown Test Setup

1.1 Specimen

Chaguo la vidole vya AC disc suspension composite porcelain HU550B240/650T vilivyotengenezwa na mtengenezaji aliyochaguliwa kama sample ya majaribio. Vidole vya kivuli vina structura ya triple-umbrella, kama inavyoelezwa kwenye Chumba 1. Viwango vyake vyenye kutosha vimeelezea kwenye Meza 1.

1.2 Test Platform and Scheme
Generator ya 2400 kV ya impulse voltage uliyotumiwa kwa ajili ya majaribio. Cap ya insulator iliyowekwa chini kwenye plate ya metal ya grounded, na ball socket standard iliyowekwa kwenye pin end ili kupunguza concentration ya electric field kwenye cemented area ya karibu na pin. Mfano wa setup ya insulator unaelezwa kwenye Chumba 2.

Majaribio ya impulse breakdown ya hewa yalifanyika kwenye insulators samples 20. Njia za majaribio ya impulse breakdown ya hewa zinajumuishwa katika steepness method na amplitude method, na amplitude method ni inayotumika zaidi kwa insulators za disc.

Utafiti huu ulitumia amplitude method, ambayo haihitaji linearly ya front ya impulse bali tu amplitude ya breakdown voltage kama criteria, na front time inayohusishwa kati ya 100 na 200 ns na deviation ya amplitude kati ya ±10%. Wakati wa majaribio, kila insulator alipata five positive-polarity impulse voltages followed by five negative-polarity impulses, na sequence hiyo ilikutana mara moja. Interval kati ya impulses consecutive ilikuwa kati ya dakika 1 na 2.

Utafiti kutoka kwa watu wa kitaalamu na wengine wa kimataifa unatoa taarifa kwamba kutumia silicone rubber kwenye surfaces za insulator huongeza rate ya propagation ya surface streamers kwenye insulators za porceleni, kwa hivyo kupunguza ufanisi wa kudhibiti steep-front impulse. Lakini, ufanisi wa insulation kwenye head ya insulator haukubadilika katika matumizi halisi.

Hali hii imeithibitishwa na zaidi ya kumi na tano wa manufacturers wa disc insulator wa kimataifa: ingawa profile ya shed ni deep-rib au alternating-umbrella type, au ingawa structura ya head ni cylindrical au conical, insulators zote zinachopata reduction fulani ya ufanisi wa kudhibiti steep-wave baada ya coating silicone rubber.

Kwa hivyo, standards zenye kusambaza zimebadilishwa, kupunguza amplitude ya impulse breakdown test ya hewa kwa insulators za disc coated RTV kutoka 2.8 p.u. hadi 2.2 p.u. Matokeo ya majaribio ya mapema yanatoa taarifa kwamba kudhibiti haipatikani sana kwenye 2.2 p.u. Kwa hivyo, utafiti huu alichagua insulators za porceleni bila coating RTV na kufanya majaribio ya impulse breakdown ya hewa kwenye voltage ya standard ya 2.8 p.u., na front time ya voltage ikawekwa kati ya 100–200 ns.

Majadiliano ya tofauti ya polarity ya voltage na location ya breakdown yakatokana na kuwa kati ya 15 breakdown events, 14 ilifanyika under positive polarity na moja tu under negative polarity. Kati ya positive-polarity breakdowns, 8 ilifanyika kwenye head na 6 kwenye sheds; na negative-polarity breakdown moja ilifanyika kwenye head. Pia, arcing ilionyeshwa kwenye surface ya insulator kabla ya breakdown ya sheds, lakini hakukuwa na arcing hivi kwenye breakdown ya head.

Lakini, kwa kutumia reference, all steep-front breakdowns of porcelain insulators occurred at the head, na kwa kutumia reference, insulators za porceleni zilidhibiti kwenye head both before and after RTV coating. Kwa kinyume, majaribio hili linatoa taarifa kwamba bila one-time injection-molded HTV overcoat, breakdowns ya steep-wave kwenye vidole vya porceleni vinginevyo vilifanyika tu kwenye head. Baada ya HTV overmolding, breakdowns kwenye composite porcelain insulators vilifanyika sasa kwenye head na kwenye neck, kwa hivyo kutumia HTV silicone rubber coating huongeza njia ya kudhibiti.

Idadi ya impulses applied before breakdown ilirekodiwa, na matokeo yameonekana kwenye Chumba 4. Kama inavyoelezwa, 12 insulators vilidhibiti kwenye first five impulses, moja vilidhibiti kwenye 7th impulse, na mbili vilidhibiti kwenye 15th impulse. Reference inatoa taarifa kwamba insulators za porceleni coated with RTV wanapata reduction significant ya ufanisi wa kudhibiti steep-wave, na probability ya kudhibiti kwa insulators za large-tonnage ikiwa ni juu, kwa hivyo kutumia silicone rubber coating hutumia ufanisi wa kudhibiti steep-wave. Katika majaribio hili, 80% ya HTV overmolded composite insulators vilidhibiti kwenye first four impulses, kwa hivyo kutumia kuonyesha kuwa presence ya HTV silicone rubber hutumia ufanisi wa kudhibiti steep-front impulses.

3 Electric Field Distribution Simulation at Steep-Wave Voltage Peak

Analysis of the test results in Section 2 reveals that, compared to porcelain insulators, the breakdown path of composite insulators has changed and their steep-wave withstand performance has significantly decreased. This section employs simulation to calculate the electric field distribution of the composite insulator at the peak of the impulse voltage, aiming to investigate the causes of the altered breakdown path and reduced steep-wave performance.

2.1 Simulation Model

Observations from the air impulse breakdown tests indicate that when shed flashover occurs in composite insulators, arcs develop along the insulator surface to the breakdown location. The presence of arcs influences the electric field distribution and must be considered in the model. However, due to the irregular shape of arcs, establishing a 3D model for computation would be challenging, especially because the silicone rubber layer is thin and much smaller in dimension compared to the overall insulator, making 3D meshing difficult. Therefore, to qualitatively analyze the impact of the silicone rubber layer and arcs on the electric field distribution, a two-dimensional axisymmetric model is adopted for simplification in this section. The simulation model is shown in Figure 5.

2.2 Materials and Boundary Conditions

The 50% lightning impulse flashover voltage of the insulator is 145 kV, and the peak value of the 2.8 p.u. steep-front impulse voltage is 406 kV. Since most of the test specimens experienced positive-polarity breakdown, in the simulation, the pin (steel pin) is set as the high potential (406 kV) and the cap (steel cap) as zero potential. The relative permittivity values of the materials are listed in Table 2.

2.3 Simulation Results and Analysis

In the model without a silicone rubber coating, the electric field distribution of the porcelain insulator at the peak of the steep-front impulse voltage is shown in Figure 6(a). As seen in Figure 6, the electric field intensity is mainly concentrated at the insulator's head, reaching up to 50 kV/mm, indicating a high likelihood of head flashover—consistent with field experience and related studies.

To comparatively analyze the effect of the silicone rubber coating, the electric field distribution of the composite insulator model with one-time injection-molded silicone rubber was calculated, with results shown in Figure 6(b). It can be observed from Figure 6(b) that the maximum electric field occurs at the end of the arc on the lower surface of the insulating body, approximately 219.4 kV/mm; the field strength at the arc end on the upper surface is lower, at 41.21 kV/mm; and significant field concentration also exists at the pin head, with a maximum of 50.68 kV/mm.

Thus, under the influence of the silicone rubber coating, the surface resistivity of the insulator increases, significantly raising the ratio of volume capacitive current to surface resistive current in the sheds. This leads to a substantial increase in the electric field component perpendicular to the insulator surface, causing the arc to closely follow the surface after initiation.

Under the influence of the HTV coating, surface arcs propagate along the insulator surface when subjected to steep-front voltage, resulting in a sharp rise in local field strength—far exceeding that at the pin head—making breakdown more likely at the arc tip and leading to shed flashover. This indicates that the steep-wave withstand performance is affected by the HTV coating on the shed surface. Additionally, the simulation shows a relatively high electric field at the insulator head, which correlates with the observed head flashovers in tests.

3 Conclusion

Air impulse breakdown tests were conducted on composite insulators to analyze their steep-wave breakdown characteristics, and electric field distribution simulations were performed at the peak of the steep-front voltage. The following conclusions were drawn:

• Under 2.8 p.u. steep-front impulse voltage, 15 out of 20 composite insulator specimens experienced breakdown, with 80% occurring within the first four impulses, indicating that the presence of HTV silicone rubber significantly reduces the steep-wave withstand performance of composite insulators.

• Among the 15 breakdown events, in addition to flashovers at the pin head, six occurred at the sheds, indicating a clear change in the overall breakdown path compared to conventional porcelain insulators.

• Simulation results show that the surface arc propagation in composite insulators causes a significant increase in shed electric field intensity at the voltage peak, reaching 217.64 kV/mm, making shed flashover more likely. In contrast, for insulators without a silicone rubber layer, the maximum field during arc development is located at the pin head, reaching 49.55 kV/mm, where breakdown primarily occurs.