DESCRIPTION OF THE EQUIPMENT
REV6 /REV1 OI 248 (EN) 107
A1 Description of the Equipment
A1.1 Purpose
Circuit breakers are used for power distribution in high voltage net-
works. They are installed in substations along with other switchgear
and are an essential functional and safety feature. In the event of a
system disturbance or line fault, circuit breakers interrupt the resul-
ting short-circuit currents within a few milliseconds. These breakers
are generally operated by remote control.
A1.2 Main Components
A circuit breaker consists of pole columns, base frame and opera-
ting mechanism
(see “Components Supplied” on Page 17).
Each pole column consists of a post insulator for insulating opera-
tional voltage to ground and a chamber insulator in which the inter-
rupter unit is located.
The base frame is a galvanized welded steel structure.
The operating mechanism consists of a steel structure that is self-
supporting and protected against corrosion. The door, floor, rear
panel, removable side panels, and roof are constructed of alumi-
num sheet.
A1.3 Operation
The pole columns and the gas piping form a common gas compart-
ment. The movable contacts of the interrupter unit are connected to
the operating mechanism by the insulating rods, the torque shafts
and levers of the pole column, and the connecting rods in the base
frame.
When current is interrupted, the transition from the closed position
to the open position occurs within a few milliseconds. During this
opening operation, the main contacts separate first. The arc that is
formed between the arc contacts that then open is quenched by a
gas flow within the interrupter unit. The main contacts, which have
already opened, are not eroded by the arc.
In third-generation circuit breakers, the necessary gas pressure is
generated in a pressure chamber by the energy of the arc itself as a
function of current. The operating mechanism only supplies the
energy required for contact movement and mechanical auxiliary
blow-out to ensure safe breaking of small currents.
During the closing operation, the arcing contacts are closed first
and then the main contacts.
The position is indicated visually by a position indicator.
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