Outdoor SF6 Gas Circuit Breaker

Standards and approvals

The RHB-40.5 circuit-breakers comply with the IEC 62271-100 standard as well as of other major industrialised countries.

They have undergone the tests indicated below andensure service safety and reliability of the apparatus in allinstallations.

Type tests:
– Temperature rise test
– Di-electric test
– Short circuit test duties
– Short time current test

– Mechanical endurance test

Routine tests:
– Power frequency voltage with stand test
– Insulation test on auxiliary and control circuits
– Measurement of main circuit resistance

– Mechanical and electrical operation test

Service safety
The mechanical and electrical locking devices have been provided to prevent incorrect operations and to carry out inspection of the installations while guaranteeing maximum operator safety.

Structure
RHB-40.5 type circuit breaker is a porcelain column structure, with three phases separated, each has a gas-pressured arc extinguishing chamber, and the three-phase gas is connected through copper pipes. The circuit breaker is composed of a pillar porcelain bottle, a current transformer, an arc extinguishing chamber, an adsorber, a transmission box, a connecting rod, a chassis and a spring operating mechanism.

Porcelain sleeve

Porcelain sleeve is the supporting and insulating component of the main circuit of the circuit breaker and the power system. Because it is in communication with the circuit breaker shell, it is a part of the pressure vessel, so it has high strength and good air tightness.
The arc extinguishing chamber of the RHB-40.5 circuit breaker is mainly composed of static contacts, moving contacts, porcelain sleeves, cylinders and nozzles (see Figure 5). The porcelain sleeves and insulation rods form the ground insulation of the moving and static contacts. .

Adsorber
The adsorber is an aluminum alloy container. RHB-40.5 circuit breakers are each equipped with six, but three of them are placed in the gearbox and three are in the cooling cap. The F-03 molecular sieve is installed in the adsorber, and its role is to adsorb the water in the sulfur hexafluoride gas and the low fluoride formed by the decomposition of the arc.

Working principle

The breaking principle of RHB circuit-breakers is basedon compression and self-blast technique to obtain topperformances at all breaking current values, with minimumarc times, gradual arc extinction without chopping, and norestriking or switching overvoltages. This breaking technique-already widely appreciated and used in high voltage circuit-breakers, has been introduced into medium voltage with theHD4 series circuit-breakers for indoor installation.

Main contact separation

No electric arc is struck because the current flows through the arcing contacts. During its run downwards, the moving apparatus compresses the gas in the lower chamber. The compressed gas
flows from the lower to the upper chamber, thereby taking both the chambers to the same pressure.

Arcing contact separation

The current flows due to the electric arc which has struck between the arcing contacts. The gas cannot escape through the nozzle because the hole is still closed by the fixed arcing contact and cannot even escape through the inside of the arcing contact, because of the clogging effect of the electric arc.

– at low current values, the arc is extinguished when the current passes through its natural zero and the gas flows through the contacts. The low pressure level cannot chop the current and the modest amount of gas which “escapes” is sufficient to restore di-electric resistance between the two contacts, preventing restriking on the rising front of the recovery voltage.

– at high short-circuit values, the pressure wave generated by the electric arc closes the valve between the two chambers so that the circuit-breaker starts to operate as “pure self-blast”
apparatus. The pressure increases in the upper volume due to the gas heating and molecular dissociation due to the high temperature. The pressure increase is proportional to the arc current and ensures arc extinction during the first passage through zero current.

Circuit-breaker open

The arc has been extinguished, the self-generated pressure in the upper volume decreases because the gas is flowing through the contacts. The valve re-opens and a new jet of fresh gas flows in and “washes” the chamber. This means the apparatus is immediately ready to close and trip again up to its maximum breaking capacity.

1 Terminal
2 Insulating enclosure
3 Blasting nozzle
4 Moving arcing contact
5 Moving contact
6 Fixed arcing contact
7 Fixed contact
8 Insulating tie-rod
9 Cap with bursting valve (upon request）

Standard Equipment

1)GSH operating mechanism, complete with manualopening and closing push buttons, mechanical indicatorsfor circuit-breaker “open or closed” and for springs“charged or discharged”
2) Shunt opening release
3) Shunt closing release
4) Spring-charging geared motor
5) Lever for manual spring charging
6) Pressure switch with two levels (one per pole); suitable foroperation down to -25 0 C. For lower service temperatures,please contact us
7) Locking circuit for insufficient gas pressure (automaticopening with additional shunt opening release and lock inthe open position by means of closing circuit interruption)
8) Electrical contacts signalling: springs charged
9) Auxiliary contacts (13 NO + 13 NC) including those usedfor internal breaker-control circuit
10) Anti-condensation/heating circuit for low temperatureswith armoured anti-condensation heating elements andthermostat; solution provided for operation down to -25 0 C
11) The cabinet is fitted with cable gland plate for control,cables and with padlockable front door

The circuit-breaker is supplied with asymmetrical terminalconnections on one side of the poles only and with 4 holesas per NEMA form 4 Standards. The lower terminal is turnedtowards the rear of the apparatus, the upper terminalsare provided as standard turned towards the front of theapparatus but, on request, it can be turned towards the rearof the apparatus

Equipment supplied on request

12) MCB for geared motor protection
13) Signalling lamps placed inside the cabinet, in a position visible from the inspection window on the door. A single solution with 4 lamps is provided for:
– signalling circuit-breaker closed (red lamp)
– signalling circuit-breaker open (green lamp)
– signalling springs charged (yellow lamp)
– signalling insufficient gas pressure (white/amber lamp)
14) Selector switch for local/remote control
15) Control switch for local ON/OFF electrical operation through shunt closing and opening releases
16) YU undervoltage release
17) Electrical signalling of YU undervoltage release energised (or de-energised)
18) Single-phase socket
19) Illumination lamp which automatically switches on by means of a limit switch when the door is opened
20) Telescope metal structure to vary mounting height and arrangement of CT/PT mounting