General CIRCUIT BREAKER WITH SF6 GAS

ETK Type Circuit Breakers:

SF6 gas is used as insulating and arc quenching medium within ETK type circuit breakers. ETK breakers are suitable for rapid reclosing.

Main Components:

» Three separate poles (including electrically live parts. Pole housing is epoxy resin.)» Operating mechanism.» Chassis

ETK is suitable to use in Medium Voltage Metal Enclosed Switchgear and Controlgears. Switching tests of breaker were carried out inside MME* type cubicle.

Sealed pressure system is used for gas tightness. The gas leakage ratio of under 0.1% per year guarantees 25 years of lifecycle with no gasaddition.

* MME is air insulated, metal enclosed, LSC2A-PI type switchgear produced by ELKO.

Pole Structure and Interruption

1 Upper terminal

2 Fixed main contact

3 Fixed arcing contact

4 Moving arcing contact

5 Moving main contact

6 Lower terminal

7 Epoxy housing

8 Gas filling point

9 Molecular sleeve

The fixed and moving contacts belonging to main circuit are placed inside epoxy resin housing. The housing has a robust structure to resist the thermal and dynamic effects arising from the making and breaking operations of breaker. Precautions, to prevent the crush of pole due to unexpected pressure rise conditions, have been taken.

The breaking technique of ETK type breakers is based on “Puffer System”. While the arcing contacts are being separated, the superior insulation and thermal properties of SF6 gas enables ETK to;

• Cool down the arc temperature by directing SF6 gas, which is compressed in lower chamber during downward movement of arcing contact, towards arc,

• Prevent re-ignation by building up the dielectric strength between the contacts immediately

1

2

3

45

67

8

9

CIRCUIT BREAKER WITH SF6 GAS

Operating Mechanism

Operating Mechanism:

• placed in metal frame, having IP20 degree of protection • trip-free • suitable to cycle “O-0.3sec-CO-3min.-CO” • compact structure ensuring stability and mechanical reliability

The operating mechanism of ETK is based on stored energy within a spring.

» Storing Energy: • with geared DC motor (electrically) • with operating handle (manually)

» Releasing Energy: • with shunt releases (electrically) • with open/close button placed on mechanism (manually)

The standard components on Operating Mechanism:

• Manually operated stored energy mechanism (motor included) * Push-button for closing (1) * Push-button for opening (2)• “Spring Charged” and “Spring Discharged” display (3)• Position indicator (Open/Close) (4)• Mechanical operation counter (5)• Mechanical key* (6)• Charging limit switch• Anti-pumping circuit• Auxiliary contact block

Remark: The desired voltage ratings for DC motor and open/close coils should be stated at ordering.

* When the key is unplugged, the locking mechanism locks the breaker, at OPEN position, both electrically and mechanically.

CIRCUIT BREAKER WITH SF6 GAS

Dimensions and SF6 Gas

*Dimensions are in milimeters.

About SF6 Gas:

SF6 is one of the heaviest known gas, whose density is approximately five times higher than that of air. It is colorless, odorless, inflammable and non-toxic. Besides, this compound has chemically exceptional stability. In the range of service conditions (-25 to 50oC), the variation of pressure with temperature is linear and relatively small.

The overall heat transfer capability of SF6 is excellent. Thus, especially during interruption of high currents, the arc can be extinguished effectively by thermal transport.

The electronegative character of SF6 molecule provides excellent dielectric properties. The dielectric strength of SF6 is about 2.5 times higher than that of air.

After the electric arc formed by the opening of contacts, decomposition and ionization takes places. Addition to fluorine and sulphur, some other decomposition products arise, but the concentration of these products is 20-30 times under IDLH threshold limit value (IEC 1634). After the gas cools down, sulphur and fluorine again forms SF6 compound. Other decomposition products are absorbed using materials such as activated alumina or molecular sieves.

The environmental affects of SF6:

SF6 does not contribute significantly to stratospheric ozone depletion because it contains no chlorine. The contribution of SF6 to global warming is less than one part in ten thousand of the total contribution of the other agents and is thus negligible.

CIRCUIT BREAKER WITH SF6 GAS

Electrical Characteristics CIRCUIT BREAKER WITH SF6 GAS