Pagsusi sa Pagkamalas ng Surge Arrester ug Pagpangandoy: Key Katuyuan sa Malfunction sa 10 kV Distribution Arresters

1. Pagpasilidad

Sa operasyon sa sistema sa kuryente, ang mga pangunahon nga kasangkapan naghahadlok gikan sa interna ug atmosperiko nga overvoltages. Ang surge arresters, partikular ang metal oxide arresters (MOAs) uban sa maayo nga nonlinear volt-ampere characteristics, mahimong kaayo sa proteksyon tungod sa ilang maayong performance, dako nga current-carrying capacity, ug matigas nga resistance sa pollution. Apan, ang dugay nga pag-expose sa power frequency voltages, sama sa kalidad sa komponente, proseso sa pagbuhat, ug eksternal nga yutang, nagpadayon sa MOAs nga mabag-o og init o explosion, na kinahanglan og siyentipikong pag-identify, paghukom, ug pag-prevent.

Ang makina nga paper nga ini nagbahin sa large-scale 10 kV distribution MOA failures sa usa ka rehiyon. Ang analisis nagpakita nga ang burst arresters gitukod sa usa ka modelo sa usa ka manufacturer. Tulo nga faulty-phase ug duha nga normal-phase MOAs sa modelo nga ini gibuwag ug gi-test aron masayri ang mga rason ug countermeasures.

2. Overview sa Fault

Ang mga faulty surge arresters gitukod sa 10 kV distribution lines sa usa ka 35 kV substation. Ang mga failure mahimong dugay sa panahon sa thunderstorm, ug ang abnormal/fault records sa substation dili makasagol sa faulty-phase arresters. Ang lima nga sampled arresters walay accurate protection action ug fault recording information. Ang lightning location systems nagpakita nga sa 2020, adunay 516 lightning strikes sa loob sa 10-km radius nga gitukod sa substation.

Human sa on-site installation, gibuhat ang handover tests (kasama ang insulation resistance testing, 1 mA DC reference voltage testing, ug leakage current testing sa 0.75 times the 1 mA DC reference voltage), tanan may qualified results.

3. Analysis sa Rason sa Failure

Tulo nga faulty-phase arresters (No.1, No.2, No.3) gibuwag; duha nga normal-phase arresters (No.4, No.5) gibuhat og tests ug buwag alang sa pag-compare, aron masayri ang rason sa large-scale failure.

3.1 Incomplete Nameplate Information

Sa tulo nga faulty-phase ug duha nga normal-phase arresters: 4 may manufacturing dates pero walay serial numbers; 1 may serial number pero walay date; ang uban nga impormasyon relatyibong kompleto.

Ang nameplates importante para sa operation ug maintenance personnel aron makakuha og basic equipment information. Ang nawalang manufacturing dates/serial numbers naghadlok sa service-life calculation ug quality tracing, nagpadayon sa centralized defect management.

3.2 Varistors Are All Fragments

Ang pagbuwag sa No.1 faulty arrester nagpakita: 6 varistors sa pagitan sa duha ka electrodes, uban sa burning marks ug white powder sa pipila ka surfaces; bisan parehas ang upper/lower surfaces, ang varistors irregular sa shape, walay uniform size o arrangement. Ang thicknesses include 18 mm, 20 mm, 23 mm, ug 25 mm. Tulo nga varistors may regular outer arcs (presumably gikan sa outer circles sa complete disc-shaped/annular varistors). Similar issues exist in the other two faulty-phase arresters.

Ang No. 5 intact surge arrester gibuwag (walay damage sa proseso, resulta sa Fig. 4). Sa sulod: 5 varistor pieces + 3 metal gaskets. Ang varistors may flat top/bottom surfaces, irregular fragments otherwise, similar sa uban: 3 pieces ~22mm thick, 1 at 20mm, 1 at 17mm. 3 pieces show regular outer arcs (from outer circles of complete disc/ring-shaped varistors); 2 show regular inner arcs (from inner circles of complete ring-shaped varistors).

Ang varistors sa standard metal-oxide surge arresters regular discs, rings, o cylinders. Ang ilang dimensions link strictly to voltage ratio (residual/reference voltage), potential gradient, current-carrying capacity, raw materials, ug firing processes. Bago ang core assembly, gi-test ang bawat varistor (power-frequency, DC, high-current impulse, square-wave, etc.). Only passed pieces are assembled.

Ang pagbuwag nagpakita nga ang arresters gingamit unconventional varistors: inconsistent counts of varistors/metal gaskets across same-model units; irregular shapes, varying thicknesses, ug uneven outer arcs. Thus, cores are patched from fragments of conventional varistors (different specs/electrical params), not 10 kV standard ones. Comparison of faulty vs. normal phases confirms this is a factory defect, not fault-induced.

Ang mga varistors niini may subpar electrical performance. Uneven contact areas worsen overvoltage resistance, current-carrying capacity, ug stability—easily causing breakdowns during line surges.

3.3 Poor Sealing of Composite Jacket

Pagbuwag sa No. 3 faulty arrester: ang usa ka end sa composite jacket seals well with the electrode (Fig. 5); ang uban wala'y cast sealing. Only a little sealant fills the electrode-arc-shield gap—ineffective for protection, causing gaps and severe electrode rust (Fig. 6).

Kini nga poor sealing stems from inadequate casting in production, not faults.

Ang composite jacket wala'y casting seal sa usa ka side sa arc-isolating cylinder, ug ang threaded surface sa electrode block severely rusted. This shows that even with sealant, moisture can seep into the arc-isolating cylinder through thread gaps. During operation, moisture adhering to the varistor core assembly surface increases leakage current and resistive components, causing severe heat. Long-term operation leads to rising temperatures inside the arc-isolating cylinder, possibly melting and bursting the cylinder wall, gradually deteriorating the surge arrester's operational quality.

When inspecting No. 4 surge arrester, uneven thickness of the composite jacket was found at one electrode end. A micrometer measured the thickest part at 4.985 mm and the thinnest at only 0.275 mm, as shown in Figure 7. The figure also shows the center electrode column perforation of the jacket is not a standard circle, indicating poor sealing here.

Ang composite jacket mainly made of silicone rubber. Its uneven thickness results from poor process control and eccentricity during the vulcanization stage of production. For conventional 10 kV surge arresters, the composite jacket has a uniform thickness of 3–5 mm. Over-thin silicone rubber exhibits poor aging resistance and is prone to cracking. It not only allows moisture to penetrate and adhere to the surface of the insulating cylinder, causing moisture-induced faults, but may also impair the external insulation performance of the equipment, becoming a key factor restricting product quality.

3.4 Qualified in Conventional Tests, Unqualified in Special Tests

DC voltage-related tests were performed on the No. 5 normal surge arrester, with results shown in Table 1.

To verify its over-current withstanding capability, a high-current impulse test was conducted on the No. 4 normal surge arrester. Even when the test impulse current was far below the standard-specified value, the arrester still experienced breakdown and shattering, resulting in a failed test. Detailed data are presented in Table 2.

4. Recommendations

When bidding and procuring surge arresters (especially for distribution networks), clearly define supplier qualifications and technical specs. Choose suppliers with mature processes and good performance; avoid overly low-cost bids.

During acceptance of delivered distribution network arresters, construction and operation units must follow standards like “Five-Pass”. Conduct item-by-item checks, retain factory test reports to ensure qualification rates.

Use provincial material inspection centers’ test platforms. Perform sampling tests (AC/DC, high-current impulse, sealing) for 10 kV arresters to block unqualified products from grid connection.

After installation, before commissioning, strictly follow GB 50150–2016 for on-site tests. Issue standardized reports, archive as required. Ensure full-process data management (production → transport → acceptance → handover test → commissioning).Post-commissioning, enhance patrols/records. In rainy seasons, use infrared imaging. For abnormal heating, power off and replace promptly to prevent fault expansion.