Pagsusi sa Kasiguraduhan ug Reliability Assurance sa Medium-Voltage Switchgear

Isipagawas nga nangilin-an sa operasyon sa sistema sa kuryente, nakakita ko nga ang mga switchgear sa medyo bataasan (MV) naglalambigit og importante nga papel sa distribusyon, pagkuha, ug proteksyon sa kuryente. Ang pagseguro sa ilang operational nga seguridad ug reliabilidad mao ang importanteng—ang bisan unsa nga sayop mahimong makadaghan kaayo ang buong sistema sa kuryente. Aron mapadako ang reliabilidad, kita kailangan ibutang sa unang dapit ang optimisasyon sa disenyo, pagsiguro nga ang MV switchgear magamit sa maayong paagi ug protektahan ang estabilidad sa grid.

1. Pahayag sa Switchgear sa Medyo Bataasan

Sa akong praktikal nga gibuhat, ang MV switchgear nagpasabot sa metal-clad switchgear isip gi-defini sa GB 3906—2020 AC Metal-Clad Switchgear and Controlgear for Rated Voltages from 3.6 kV to 40.5 kV: ang mga opisina nga kompletamente gibungkag sa metal nga casing maliban sa mga incoming/outgoing conductors.

Sa sistema sa kuryente, ang MV switchgear nagbuhat sa mga key functions: switching, pagkuha, distribution, ug proteksyon sa paggama, transmisyon, ug distribusyon stages. Sa panahon sa operasyon, gikuha ko ang iyang konfigurasyon batas sa demand sa grid—connecting o disconnecting sa mga opisina/feeders aron maprotektahan ang estabilidad. Kon may mga sayop sa mga opisina sa grid o lines, gisiguro nako ang MV switchgear aron matunanan ang mga sayop nga bahin, sigurado nga walay interupsiyon sa suplay sa kuryente sa mga lugar nga wala naapektuhan.

2. Kahalagahan sa Pagseguro sa Reliabilidad sa MV Switchgear

Ang MV switchgear adunay maluwas nga aplikasyon sa sistema sa kuryente. Kon ang China's grid expansion ug daghan nga kompleksidad, ang grids karon mas dako nga load para mapasabot ang social demands. Sa akong kasinatian, lang makapili sa MV switchgear reliability mao kini makapugos sa maayong pagdistribusyon, pagkuha, ug proteksyon, busa maintindihan ang kabuokan nga estabilidad sa grid.

Bisan unsa nga insidente sa seguridad o sayop sa operasyon sa MV switchgear mahimong madisrupt ang sistema sa distribusyon, kompromiso sa suplay sa kuryente. Sa severe cases, mahimong makadaog ang widespread outages, resulta sa economic losses sa social production. Busa, gitumong nako ang panginahanglan sa pagpadako sa MV switchgear reliability pinaagi sa multi-faceted measures, sigurado nga stable nga function ug support sa grid.

3. Strategiya sa Pagpadako sa MV Switchgear Reliability
3.1 Rasyonal nga Disenyo sa Enclosure Structure

Ang scientific nga disenyo sa enclosure mahimong pundok sa pagseguro sa MV switchgear reliability, ang una nga priority sa engineering practice. Bisag hain:

• Busbar Chamber Optimization: Ang tradisyonal nga disenyo sa busbar chamber gamiton ang insulators sa branch busbars, pero ang dust accumulation sa insulators sa panahon mahimong flashover risks. Gisiguro nako ang D-type main busbars—ilang mas taas nga strength ug tensile resistance wala na gikinahanglan ug insulators, solbion sa contamination-related nga safety issues.

• Bushing Design: Implementing three-phase integrated bushing designs sa busbar chambers prevent eddy current effects, improve electric field uniformity, ug padako ang creepage distance, thereby boosting insulation reliability.

Kini nga mga disenyo optimization align sa industry best practices, ensuring MV switchgear meets safety ug performance requirements sa real-world operations.

3.2 Rasyonal nga Disenyo sa Insulation Structure

Arong mapadako ang seguridad ug reliabilidad sa medium-low voltage switchgear, strengthening insulation design kay essential. Sa practical design, aside sa meet sa insulation requirements, factors such as design cost ug environmental protection usahay nga consider.

3.2.1 Rasyonal nga Seleksyon sa Insulating Gases

Sa medium-voltage switchgear, ang SF₆ gas ang primary insulating medium. Pero, ito toxic ug high GWP (Global Warming Potential). While CO₂ greenhouse gas high GWP, SF₆ gas 23,900 times GWP than CO₂, highlighting significant harm sa natural environment. Sa medium-low voltage switchgear non-critical interrupting performance, design-wise, we can attempt replace SF₆ gas with N₂ or dry air. Compared with SF₆ gas, the insulation performance of N₂ and dry air can reach 30% of that of SF₆ gas. The performance comparisons among N₂, dry air, and SF₆ gas are shown in Table 1.

As indicated in Table 1, N₂ and dry air are non-greenhouse gases, posing no threat to the ecological environment. They also have low boiling points, eliminating concerns about liquefaction during normal use, even in extremely cold regions. Notably, N₂, as the main component of air, features stable chemical properties. However, excessively high N₂ concentration can cause asphyxiation due to oxygen deprivation. When designing with N₂ as the insulating gas, ventilation and protective equipment must be configured. In contrast, using dry air as the insulating gas avoids such issues. Through comprehensive comparison, dry air can be adopted to replace SF₆ as the insulating gas in switchgear insulation design.

When using dry air as the insulating gas, the design of the minimum air gap should be considered. According to relevant standards, for a rated voltage of 12 kV, the minimum air gap between phases and from phase to ground should be 125 mm. If the condensation test is passed, the minimum air gap can be slightly smaller than 125 mm. Employing dry air as the insulating gas allows for an appropriate reduction in the minimum air gap.

3.2.2 Enhancing Breakdown Voltage in Gas Gaps

During the design process, to ensure the safety and reliability of medium-low voltage switchgear, the breakdown voltage in gas gaps should also be enhanced, with specific methods as follows:

• Improving the electric field distribution in medium-low voltage switchgear. This can be achieved by optimizing electrode shapes based on actual conditions or making full use of space charges to enhance electric field uniformity. If the electric field uniformity is extremely poor, adding barriers is also an option.

• Suppressing the ionization process of dry air. Applying high pressure in medium-voltage switchgear can weaken the ionization process of dry air. Alternatively, using high vacuum in medium-voltage switchgear can achieve the same effect.

When using high pressure or high vacuum, the gas tank strength is required to be extremely high, and leakage problems are prone to occur in practical applications, leading to serious consequences. Therefore, in actual design, improving the electrode shape and adding barriers in extremely inhomogeneous electric fields are more feasible methods to increase the breakdown voltage in gas gaps.

3.3 Rasyonal nga Seleksyon sa Mga Komponente

Ang core components sa medium-voltage switchgear, including vacuum circuit breakers, vacuum interrupters, ug contacts, directly affect the equipment's operational safety ug reliabilidad, requiring strict quality control.

Take ABB switchgear as an example. Its vacuum interrupters undergo rigorous pre-shipment inspections: automatic high-voltage tests verify the insulation strength, while spiral magnetron devices measure internal pressure within a chamber filled with inert gas. After a specified isolation period, a second pressure test is conducted, and results are compared to ensure sealing performance meets standards.

In manufacturing, ABB vacuum interrupters require strict environmental and process controls. Produced at CalorEmag's German factory, they are professionally assembled by regional medium-voltage switchgear enterprises before centralized supply. High-performance alloys like Cu-Cr and W-C-Ag are prioritized for component materials to ensure durability.Assembly occurs in dedicated cleanrooms using a "one-time sealing and exhausting" process: under 800°C high temperature, high vacuum is first achieved, followed by simultaneous welding and sealing to guarantee process reliability.

The R&D evolution of vacuum interrupters reflects continuous performance optimization: early assemblies exposed to air relied solely on insulating partitions for isolation. Subsequent improvements included insulating sleeves over interrupters and contacts to balance electric fields, followed by integral casting for interrupters and contacts to enhance phase-to-phase insulation and impact resistance, while adopting eco-friendly materials to integrate performance with environmental considerations.

3.4 Rasyonal nga Plan sa Design Validation Tests

After the design of medium-voltage switchgear is completed, experimental validation becomes a critical phase. The actual validation must strictly comply with relevant standards, such as GB 3906—2020 AC Metal-Clad Switchgear and Controlgear for Rated Voltages from 3.6 kV to 40.5 kV, GB/T 11022—2020 Common Technical Requirements for High-Voltage AC Switchgear and Controlgear Standards, and GB/T 1984—2014 High-Voltage AC Circuit Breakers.

Key Points for Type Tests

Comprehensive performance verification shall be conducted for the electrical components and auxiliary elements of medium-voltage switchgear to ensure technical parameters meet the requirements. When design processes or production conditions change, type tests must be re-conducted to guarantee equipment safety and reliability. For normally produced equipment, a temperature rise test is typically required every 8 years; mechanical operation tests are carried out to inspect operational performance; meanwhile, safety verification items such as short-time withstand current and peak withstand current tests are also necessary.

Taking ABB medium-voltage switchgear as an example, it has passed experimental validations in multiple countries under the most stringent standards to date, demonstrating exceptional safety and reliability. Take the internal arcing test as an example, which verifies:

• The fixing methods and closed status of switchgear doors, covers, and other components;

• The firmness of fixing dangerous components;

• The structural stability of the equipment casing under combustion or other hazardous scenarios;

• Whether indicators are arranged in compliance with production specifications;

• The completeness of protective measures and the flammability rating of the equipment.
  Only by ensuring the equipment's non-flammability can operational safety be fundamentally guaranteed.

4 Conclusion

As a core component of the power system, the operational reliability of medium-voltage switchgear directly affects grid safety. Therefore, it is essential to strengthen the safety and reliability design of the equipment, strictly optimize technical parameters in accordance with standards, and build a solid safety defense through systematic validation tests, ensuring that medium-voltage switchgear stably performs distribution, protection, and control functions in the power system.