Ang maong pagtungha sa unang panahon mahitungod sa konpigurasyon sa proteksyon sa 10KV distribution transformer

1. Wiring Forms of Ring - Main Unit
1.1 Composition of Ring - Main Unit

Ang Ring - Main Unit (RMU) gisusun batas. Kasagaran, adunay tulo ka mga batas, kinahanglan duha ka mga batas para sa entry ug exit sa ring cable ug usa ka batas para sa transformer circuit.

1.2 Configuration of Protection Modes for Ring - Main Unit

Ang tanang ring cable feeder compartments ug ang transformer feeder compartments mogamit og load switches, kasagaran ang three - position load switches nga may mga functions sa making, breaking, ug grounding. Ang mga transformer feeder compartments usab adunay high - breaking - capacity backup current - limiting fuses alang sa proteksyon. Gipruwebihon na sa praktikal nga operasyon nga kini usa ka simple, reliable, ug economical nga power distribution method.

1.3 Characteristics of Protection Configuration for Ring - Main Unit

Ang load switch gigamit aron iswitch ang rated load currents. Adunay characteristics sama sa simple structure ug low cost, pero dili makaputli sa short - circuit currents. Ang high - breaking - capacity backup current - limiting fuse nagserbiyis bilang protective element ug makaputli sa short - circuit currents. Ang pagcombine niining duha ka elements organically makakatugot sa operation ug protection requirements sa power distribution system sa iba't ibang normal ug fault operation modes. Ang pagdetermine sa circuit breaker parameters ug ang design ug manufacturing sa iyang structure gibuhat sa strict accordance sa standards.

Adunay lahi-lahi nga operation ug protection functions, kung diin ang iyang structure komplikado ug ang iyang cost mataas, kung diin ang large - scale use impractical. Sa ring - main units, adunay daghan nga load switch ug high - breaking - capacity backup fuse combination devices. Ang operation ug protection functions alang sa electrical equipment, wala eksakto ang sama, girealize pinaagi sa duha ka simple ug inexpensive components. Busa, ang load switch gigamit aron kompleto ang daghang load switching operations, samantalang ang high - breaking - capacity backup current - limiting fuse gigamit aron maprotektahan ang equipment diin dili kasto magshort - circuit. Kini maayo nga nagsolve sa problema, avoiding the use of complex and expensive circuit breakers while meeting the actual operation requirements.

• Ang mga circuit breakers adunay tanang protection ug operation functions, apan mahal sila.

• Ang mga load switches adunay basically sama nga performance sa circuit breakers, apan dili makaputli sa short - circuit currents.

• Ang combination sa load switch ug high - breaking - capacity backup current - limiting fuse makaputli sa short - circuit currents. Ang breaking capacity sa pipila ka fuses mas taas pa kay sa circuit breakers. Busa, ang paggamit niining combination dili lang sama effective sa paggamit sa circuit breaker, apan ang cost mahimong mapadami.

1.4 Advantages of the Combination of Load Switch and High - Breaking - Capacity Backup Fuse

Ang combination sa load switch ug high - breaking - capacity fuse adunay sumala nga advantages:

1.4.1 Good Performance in Switching No - Load Transformers

Ang majority sa loads sa ring - main units mao ang distribution transformers. Kasagaran, ang capacity dili mas taas sa 1250 KVA, ug sa rare cases, makarating sa 1600 KVA. Ang no - load current sa distribution transformer kasagaran about 2% sa rated current, ug ang no - load current sa larger distribution transformer mas gamay. Kapag ang ring - main unit nagswitch sa small current sa no - load transformer, maayo ang performance ug dili magenerate og high overvoltage.

1.4.2 Effective Protection of Distribution Transformers

Lalo na sa oil - immersed transformers, ang paggamit sa load switch uban ang high - breaking - capacity backup current - limiting fuse mas effective kay sa paggamit sa circuit breaker. Pwede sad nga ang latter dili maka provide effective protection. Relevant information shows that when an oil - immersed transformer has a short - circuit fault, ang pressure generated by the arc rises, ug ang bubbles formed by oil vaporization will occupy the space originally belonging to the oil. Ang oil will transfer the pressure to the transformer oil tank. As the short - circuit continues, ang pressure further increases, causing the oil tank to deform and crack.

Para malihok ang damage sa oil tank, ang fault kinahanglan matipon sa 20 ms. Kon gamiton ang circuit breaker, tungod sa presence sa relay protection, plus its own operation time ug arc - extinguishing time, ang total opening time generally not less than 60 ms, which cannot effectively protect the transformer. But, ang high - breaking - capacity backup current - limiting fuse adunay quick - breaking function. Coupled with its current - limiting function, it can clear the fault and limit the short - circuit current within 10 ms, effectively protecting the transformer. Busa, ang high - breaking - capacity backup current - limiting fuses dapat gamiton para maprotektahan ang electrical equipment as much as possible instead of circuit breakers. Even if the load is a dry - type transformer, ang fuse protection acts quickly ug better than using a circuit breaker.

1.4.3 In Terms of Coordination of Relay Protection

Sa majority sa cases, dili naayon ang paggamit sa circuit breaker sa ring - main unit. Tungod kay ang protection settings sa circuit breaker sa head end sa ring distribution network (i.e., ang 10KV feeder circuit breaker sa 110KV or 220KV substation) generally as follows: ang time for instantaneous protection is 0s, ang time for over - current protection is 0.5s, ug ang time for zero - sequence protection is 0.5s. Kon gamiton ang circuit breaker sa ring - main unit, even if the setting time is 0s for operation, due to the dispersion of the inherent operation time of the circuit breaker, it is difficult to ensure that the circuit breaker in the ring - main unit, rather than the upper - level circuit breaker, acts first.

1.4.4 High - Breaking - Capacity Backup Current - Limiting Fuse Can Provide Protection for Downstream Equipment

Sama sa current transformers, cables, etc. Ang protection range sa high - breaking - capacity backup current - limiting fuse can be from the minimum melting current (usually 2 - 3 times the rated current of the fuse) to the maximum breaking capacity. Ang current - time characteristic sa current - limiting fuse generally a steep inverse - time curve. After a short - circuit occurs, it can melt and clear the fault in a very short time. Kon gamiton ang circuit breaker for protection, it will inevitably greatly increase the thermal stability requirements of other electrical components such as cables, current transformers, and transformer bushings, increasing the cost of electrical equipment and the project cost. Here, it should be pointed out that when using the combination of a load switch and a high - breaking - capacity backup fuse, the two should be well coordinated. When the fuse does not melt in three phases, the striker of the fuse should immediately trip the load switch to prevent single - phase operation.

2. Wiring Forms of High - Voltage Chambers for Terminal Users

Ang standard GB14285 - 1993 "Technical Code for Relaying Protection and Safety Automatic Devices" stipulates that when selecting the protective switchgear for a distribution transformer, when the capacity is equal to or greater than 800 KVA, a circuit breaker with a relaying protection device should be selected. This regulation can be understood based on the following two aspects of needs:

• Kon ang capacity sa distribution transformer makarating sa 800 KVA ug above, sa past, most of them were oil - immersed transformers ug equipped with gas relays. Gamiton ang circuit breaker can cooperate with the gas relay to effectively protect the transformer.

• Para sa users with a device capacity greater than 800 KVA, tungod sa various reasons, a single - phase grounding fault may cause the zero - sequence protection to act, causing the circuit breaker to trip and isolate the fault, so as not to cause the feeder circuit breaker of the main substation to act and affect the normal power supply of other users. In addition, the standard also clearly stipulates that even if a single transformer does not reach this capacity, but if the total capacity of the user's distribution transformers reaches 800 KVA, this requirement should also be met. At present, the wiring scheme of most users' high - voltage switchgear rooms is a basic wiring method, and based on this, wiring methods such as one - main - one - standby incoming lines or double incoming lines with busbar sectioning can be derived.

3. Conclusion

Ang protection configurations for 10kV distribution transformers mainly include circuit breakers, load switches, or load switches with fuses. Considering technical, economic performance, and operation management factors comprehensively, whether in a 10kV ring - main unit or a high - voltage power distribution unit for terminal users, the protection configuration of a load switch combined with a high - breaking - capacity backup current - limiting fuse can not only provide rated load current but also interrupt short - circuit currents and has the performance of switching no - load transformers, which can effectively protect distribution transformers. Therefore, the configuration of a load switch combined with a high - breaking - capacity backup current - limiting fuse is recommended as the protection mode for distribution transformer protection.