Description | ACB | VCB | SF6 |
Abbreviation of the Circuit Breaker | Air Circuit Breaker | Vacuum Circuit Breaker | Sulphur Hexa Fluoride Circuit Breaker |
Voltage Application | LV voltage application upto 690 Volts 50Hz/60 Hz | MV (Medium Voltage) from 11kV up to 33 kV | High Voltage and EHV application above 11kV to 1010 kV |
Arc Quenching Medium | Air | Vacuum | SF6 Gas |
Working Principle | Air act as a good dielectric medium. Since moving and fixed contact are kept in open air with closed package. Whenever the circuit breaker opens, the arc will be quenched by air | Free electron cannot be formed in vacuum, Since the vacuum filled In between the male and female contact. Whenever the circuit breaker interrupts, the arc will be quenched by vacuum. | SF6 Gases are absorbed the free electron, which is developed by the electric arc. Basically Sulphur hexafluoride (SF6) is an inert, heavy gas having good dielectric and arc extinguishing properties. It has high die-electric strength and outstanding arc quenching characteristics. |
Medium Pressure | In ACB, open air pressure is enough to quenching the arc | 10^-2 to 10^-6 torr vacuum pressure is maintained in the vacuum camper | 2 – 2.5 bar SF6 gas pressure to be maintained |
Refilling | ACB does not require any refilling process, Since open air is free of cost | Yes, In VCB, there is no chance of re-filling process, upon failure of vacuum we should replace the vacuum container. Therefore in VCB we do replacement | SF6 gas can be refilled upon decreasing in gas pressure. The process is just like filling air to your car tire. |
Application | Indoor application, ACB cannot be used in outside. | Indoor application | Mostly Outdoor application, sometime indoor application |
Maintenance | Frequent maintenance to be done. | Very rare, once installed means VCB works like any think | Periodic maintenance to be done |
Arc Chute | Arc chutes are used to reduce arc development. It separates the arc in to smaller part. ACB cannot be operate without arc chute | VCB does not require arc chute | SF6 Circuit breaker do not need arc chute arrangement. |
Arc Development | High | Less. Vacuum circuit breakers have minimal arcing (as there is nothing to ionize other than the contact material). The arc quenches when it is stretched a very small amount (less than 2–3 mm (0.079–0.118 in)). | Medium |
Current Transformer | CT can be placed inside of the circuit breaker | CT cannot be placed inside of VCB | CT arrangement will be done outside only. |
Rake in Rake out | Simple | Hard | Hard |
Spring Charge Motor | More than 1600A ACB comes with the spring charge motor | In VCB always manufactured with Spring charge motor | SF6 comes with spring charge motor |
protection Relays | Almost 90% of the sportive relays are placed inside of the ACB. | It needs external protective relay | It needs external protective relay |
Application | Feeder, MCC, PCC and all low voltage distribution | Starting of High voltage induction Motor | Used in HT PCC and Switch yard. |
Rating of the circuit breaker | Form 630 A to 6300A | From 1250 to 4000A | 630 A to 4000A (With different voltage level ) |
Cost (Rupees/Amps) | less. Typically A Siemens make ACB cost around 100 Rs/Amps | 125 Rs/Amps | 175 Rs/Amps |
Installation | Easy | Hard | Hard |
Short circuit Breaking Capacity | Very less | Very high | High |
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