Principle of interruption and pole
sectional view
GI-E Range
E28670
E28673
Principle of interruption (the puffer type technology)
fig.3
DE60330
fig.2
Precompression:
At the beginning of the opening motion, the piston causes a slight compression of the
SF6, filling the compression cylinder before the arcing contacts are open.
E28672
E28671
fig.1
The principle of interruption of the circuit breaker GI-E range is based on the puffer
type technology.
Gas compression is self-generated in the puffer cylinder by contact motion during the
opening operation. The SF6 gas pressure necessary to extinguish the arc is selfregulated as the arc core restricts the gas blow and causes the increase of the gas
pressure up to the arc extinguishing value. The pressure of SF6 gas blown towards
the arc is proportional to the value of the current to be interrupted.
b The main contacts and the arcing contacts are initially closed and the opening
spring is charged (fig. 1).
b Thanks to the energy released by the spring, the moving contact is dragged to the
open position.During the opening operation the following phases take place
subsequently:
fig.4
Arc quenching and cooling:
v Separation of the main contacts and transfer of all current on the arcing contacts
circuit (fig. 2).
v Separation of the arcing contacts and priming, between the arcing contacts, of the
electrical arc (fig. 3).
v Cooling of the arc thanks to the pressurised blow of SF6 gas which is generated
in the compression chamber. The blow of SF6 gas is driven towards the arc through
appropriate insulated nozzle.
v Arc quenching at the crossing of the zero current.
v Completion of the opening stroke of the moving contact, increasing the gap
between the contacts and sweeping away any arc product (fig. 4).
b The SF6 gas decomposed by the electric arc recombines itself restoring stable
molecules.
The SF6 gas by product is easily absorbed by the molecular sieves which are
contained in an adequate quantity in the breaker pole.
Pole sectional view
b The components of a pole of a circuit breaker GI-E range, namely the main and
arcing contacts and the blow nozzle, are the same as adopted for the indoor circuit
breakers.
b They are highly reliable and time proven since these breakers have been working
successfully for many years.
b The switching of the rated normal current and of the rated short-circuit current
takes place inside the “puffer type” breaking chambers.
b In accordance with standard IEC 694 (96) 6.8.3, the poles of the circuit breaker
GI-E range provide a sealed pressure system, for which no further gas processing is
required during its expected operating life.
b The poles are filled with SF6 gas at the pressure of 400 kPa gauge referred to
20°C.
b Steady control of the SF6 gas pressure inside the pole is achieved by means of
pressure switch with two monitoring contacts.
b Thanks to the excellent SF6 gas chemical characteristics and to the excellent
quality of the components utilised, the poles do not lose their own insulating
properties during their service life, even after many switching operations.
b The breaker poles contain molecular sieves which maintain the purity of the SF6
gas without any renewal, even after a large number of interruptions.
LEGEND:
1 Cover
2 Molecular sieves
3 Upper terminal
4 Upper insulator
5 Fixed main contact
6 Fixed arcing contact
7 Blast nozzle
8 Moving main contact
9 Moving arcing contact
10 Compression chamber
11 Lower terminal
12 Lower insulator
13 Insulating rod
14 SF6 gas
15 SF6 gas filling valve
16 Operating shaft
17 Crank gear box
18 Pressure switch
7