Ayyuka na Ring Main Units a Cikin Sistemai na Kashi

Wannan yakin tattalin arziki da kuma yadda mutanen yaɗuwa a cikin hankali da zahiriya su, musamman a birane da yawan zafi mai yawa, inganci na gagarumar zahiriya ita ce. Tushen sadarwa ta hanyar wurin ring main za su iya bincike masu ma'ana ga gagarumar zahiriya, bayyana tsakanin, da kuma haifar da nasararsa da juyin al'amuran da za su iya faruwa daga wasu abubuwan sauran da kuma ci gaban sadarwa. A matsayin wani babban wurin na wurin ring main, Ring Main Unit (RMU) ana amfani da shi a kan sadarwa masu tashar da kuma sadarwa masu tashar da kuma sadarwa masu tashar da kuma sadarwa masu tashar, saboda muhimmancin abubuwan da suke da shi kamar tsari mai yawa, tsari mai yawa, adadin da ya fi kyau, da kuma yadda ake iya bincike parametere, addinin da kuma dalilin zahiriya.

1. Turukan Ring Main Units

A cikin sadarwa, abubuwan da suke da shi don in yi aiki a wurin ring main sun hada da cable branch boxes da RMUs. Cable branch boxes suna da adadin da ya fi kyau da kuma yadda ake iya yanayi a wurare da ke nuna mafi kyau, musamman a birane da yawan zafi mai yawa, inda ya fi kyau a samun wurin da ya kamata a kan RMUs, sun nuna mafi kyau. Amma, zuwa RMUs, hasashe da suka da cable branch boxes sun hada da ba da inganci a tsarin dalilin (musamman wajen hafara rayuwa), tsari mai yawa, da kuma nasararsa. Idan an yi aiki, mai rubutu ya tabbatar da ya fi kyau a canza RMUs don wurin ring main. RMUs suna da dukkuka da suke da shi kamar air-blast RMUs, piston-type RMUs, vacuum RMUs, da SF6 RMUs. Daga cikinsu, air-blast da piston-type RMUs suna zama da ba da inganci saboda nasararsa da kuma ba da inganci a load switches. Vacuum RMUs da SF6 RMUs ana amfani da su a cikin sadarwa saboda addinin da kuma ingancin aiki da kuma ci gaban sadarwa.

1.1 Vacuum Ring Main Units

Shekarun da aka yi a cikin tashar da kuma amfani da vacuum circuit breakers da vacuum switchgear ta yi da aikin da vacuum technology ta yi da iyakokin da a China. RMUs masu vacuum da aka yi a China sun nuna addinin da kuma ingancin a type tests, amma ba su da amfani masu yawa. Sababbin da ya fi kyau shine ba da inganci a operating mechanism. Tsarin operating mechanisms masu vacuum switches ta yi da iyakokin, da kuma saboda tasirin raw materials, processing technology, da kuma quality control, adadin da aka yi a China ba su da inganci. Aiki da kuma ci gaban sadarwa suna da nasararsa, kuma yadda ake iya cutar da darajan vacuum a vacuum RMUs ta fi kyau a cikin ci gaban sadarwa.

1.2 Muhimmanci da Hasashe na SF6 Ring Main Units

Amfani da SF6 RMUs a cikin sadarwa suna da amfani masu yawa saboda imported products. Suna da karfi a kan power supply departments saboda addinin da kuma ingancin aiki, fully insulated sealed design, da kuma ba da ci gaban sadarwa. Misalai na SF6 RMUs sun hada da Schneider's RM6, ABB's SafeRing, da Siemens' 8DJ20. Amma, akwai kuma nasararsa a cikin aiki.

1.2.1 Muhimmanci na SF6 RMUs:

(1) Addinin da ya fi kyau: SF6 RMUs suna da addinin da ya fi kyau, suna iya yi aiki da rated active loads 100 times. Suna da breaking capacity da kuma suke da kula.

(2) Ci gaban sadarwa: Tsari na cabinet surface design ta yi da iyakokin. Wiring diagram prompts ta yi da iyakokin don in bayyana aiki. Wasu abubuwan ta dogara precautions a cabinet surface, don in haifar da nasararsa. Most RMU products suna da devices masu live status detection, don in bayyana tsari mai yawa, da kuma electromagnetic locks, don in haifar da nasararsa. Kuma, transparent acrylic observation window ta yi da iyakokin don in tafiya tsari mai yawa, ta fi kyau.

(3) Inganci: Modern RMUs suna da inganci da suke da shi kamar yadda ake iya yanayi a cikin sadarwa, da kuma yadda ake iya yanayi a cikin sadarwa. Kuma, yadda ake iya yanayi a cikin sadarwa ta fi kyau, da kuma yadda ake iya yanayi a cikin sadarwa.

1.2.2 Hasashe na SF6 RMUs:

(1) Ba da inganci: Ana iya zaba ne daga cikin dukkuka da aka bayyana a cikin sadarwa, ba su da inganci don in haifar da karin aiki.

(2) Ba da inganci: Ba su da inganci don in haifar da karin aiki.

(3) Ba da inganci: Ana buƙata specialized accessories, kamar specific cable terminations, wanda ke da adadin da ya fi kyau.

(4) Tsari mai yawa: Idan ba a yi aiki da tsari mai yawa, ba su da inganci don in haifar da karin aiki.

Saboda ba da inganci a cikin fully sealed SF6 RMUs, amfani da expandable semi-sealed SF6 RMUs a cikin sadarwa ta yi da amfani. Semi-sealed RMUs suna da independent gas compartments, don in haifar da karin aiki, da kuma yadda ake iya yanayi a cikin sadarwa. Yanzu, widely used RMUs sun hada da Schneider's SM6, ABB's Uniswitch, da Siemens' 8DH10. Idan domestic manufacturers suna da ilimi game da SF6 load switch technology, adadin da kaɗai da kuma addinin da kaɗai suna da amfani. Amma, yanzu, market for domestic 10kV and 20kV SF6 RMUs ta yi da foreign companies (like Schneider or ABB).

2. Nasararsa a cikin SF6 Ring Main Units

2.1 Moisture Content in SF6 Gas

SF6 RMUs ba su da moisture content test reports. Power supply companies, as the equipment operators, ba su da yadda ake iya cutar da moisture content. Level of moisture in SF6 gas directly affects its arc-extinguishing performance and the safe operating performance of the equipment. For SF6 RMUs that have been in operation for years, assessing the state of their arc-extinguishing capability is a challenge.

2.2 SF6 Gas Leakage Issues

SF6 RMUs may have sealing issues leading to gas leaks. Practical experience shows that although imported equipment generally has good sealing performance, leakage incidents still occur. Since most units lack gas monitoring devices, users may be unaware of leaks, potentially creating hidden dangers. This is particularly concerning regarding the performance (insulation, switching, etc.) of the RMU at zero gauge pressure and its ability to withstand internal arc faults. Many of these products use manual operating mechanisms, and operators work in close proximity. An accident could have serious consequences. Currently, including a pressure indicator has become a mandatory requirement, included as a necessary accessory for semi-sealed RMUs.

2.3 Mechanism Issues

In distribution transformer protection, combination units using load switches plus fuses are common. The load switch interrupts load current, and the fuse interrupts short-circuit and overload currents. In Hebei's distribution network, incidents occurred with fully sealed RMUs where the fuse blew, but the load switch failed to open reliably, preventing the faulty transformer from being de-energized and causing severe damage. The cause was an excessive travel in the trip wire of the operating mechanism controlled for tripping, which prevented the impact force from the fuse striker pin from successfully activating the load switch's tripping mechanism. This defect can be resolved by adjusting the trip wire and the tightness of the nuts. Additionally, simulating the fuse operation for transformer feeder units has been included as a mandatory pre-commissioning test.

2.4 Material Issue of the Equalizing Shield

Semi-sealed RMUs typically cannot use touchable cable terminations. Equalizing shields are often used to address insufficient phase-to-phase distance at the cable termination connection points. However, aluminum equalizing shields are highly susceptible to damp environments. Even when used with anti-condensation heaters, their effectiveness in humid conditions is limited. In 20kV distribution systems, severe corrosion of these shields has been observed. Surface roughness and white powdery corrosion products disrupt the electric field uniformity on the shield surface, negating the equalizing effect. Due to the small phase-to-phase distances around the shields, combined with daily temperature variations, condensation forms at the bottom of the gas compartment and can flow back to the shield area, creating a discharge path. The epoxy material of the insulating barriers at the bottom of the gas compartment can suffer severe electrical corrosion, eventually leading to interphase discharge paths and ultimately surface insulation breakdown. This entire discharge process is gradual. To address condensation, power supply companies can modify the RMU's equalizing shield, switching to silicone rubber insulating cable end covers. These covers internally use a semiconductor layer, which can still provide an equalizing effect. The improved RMU design has passed condensation and withstand voltage tests and is slated for trial operation in the distribution network.

3. Recommendations for SF6 RMU Selection

(1) Choose expandable RMUs: Their flexible configuration, easy installation, and ease of expansion represent the future direction for SF6 RMU use.

(2) Consider maintenance: Ideally, the SF6 load switch should be equipped with a device to monitor SF6 pressure. Otherwise, it should have passed a zero-gauge pressure switching test.

(3) Consider climate and location: Select products that have passed condensation tests. For small ring main units, like terminal units, where future expansion is not considered, using fully sealed RMUs can significantly reduce the impact of condensation on the equipment.

Summary

Years of operational practice show that among various RMU types, SF6 RMUs offer high performance, reliability, compact size, low space requirements, and minimal maintenance, leading to their widest application. Considering various factors such as maintenance costs, secondary investments, and reliability, it is recommended, where conditions allow, to prioritize the use of SF6 RMUs in distribution network renovation and construction projects. During planning and construction, sufficient consideration should be given to incorporating automation devices and adopting safe, reliable, and advanced equipment to enhance distribution levels, making the distribution network more reliable and secure.