4 Types of electrical circuit breakers
4 Types of electrical circuit breakers
An overview of the types of electrical circuit breakers
Types of electrical circuit breakers
Electrical breakers are divided according to the method used to extinguish the spark inside them, which is as follows:
1- Breakers are very oily
” The spark inside is extinguished using a large amount of oil – and the oil tank is connected to the ground, and the oil acts as an insulator between the poles of the breaker and each other and between the poles and the tank. “
2- The breakers are low in oil
” The spark is extinguished using a small amount of oil – the spark chamber in these breakers is isolated from the ground using stabilizing insulators. “
3- Compressed air circuit breakers
” The spark is extinguished by compressed air in its tanks.
4- Breakers with self-pressure air
” The spark is extinguished by air compressed by a piston during the opening movement of the cutter.
5- Sulfur hexafluoride breakers
It uses compressed sulfur hexafluoride gas (SF6) as an extinguishing medium for the spark resulting from the separation.
6- Vacuum partitions
A vacuum medium is used between the contact points to prevent sparks from occurring between them.
Breakers used in medium voltage distribution panels
A- Oily incisors – a lot of oil
As used in Czech-made distribution boards
B – Oil cutters – low oil
As used in the Yugoslav Radaknacher type distribution panels – Energo Invest
Russian-made distribution panels and Igmac distribution panels. Siemens “
Polish and Italian paintings.
C- Vacuum partitions:
As used in IMAC distribution panels ” Siemens ” And the paintings are Arab style
D- Circuit breakers charged with sulfur hexafluoride gas (SF6).
As used in Arab distribution panels. A.B.B”
First: Oil circuit breakers. A lot of oil ” Bulk – Oil “C.B””
The high oil cutter is composed of the following parts: as shown in (1) ” Tank 1″ – Top cover 8 – Penetration insulators 9 – Mechanical parts 16 – 21 Contact points 14-15.
In the high-oil switch used at medium voltage of 11.6 kV, one tank is used for the three phases – and the tank is of a thickness proportional to the mechanical stresses – and the tank and the upper cover are connected to the ground – and the tank is insulated from the inside with a material that prevents the spark from reaching the body of the tank from the inside – and it is provided The tank has an oil indicator to determine the oil level inside the tank “3” The tank has an upper opening for filling oil and a lower opening for emptying oil.
Form “1” The cutter shows a lot of oil – and it is cut in one of the three faces during the opening process (the moment of cutting). In the figure we find that the fixed contact point is “14” At the end of the penetration insulator “9” The moving contact point is “15” Mounted on an arm made of “16” bakelite insulating material. This arm moves vertically by rotating the “21” part. – The switch is connected by rotating part “21” With an external lever – the rotating movement turns into a straight, vertical movement that attracts the moving contact points upward to connect to the fixed point. The switch has a special part that keeps the cutter in the connected position.
The separation is done manually or with an electrical separation file by attracting the part that maintains the connection position, so the moving contact points become free to move and fall under the influence of their weight away from the fixed points to complete the separation.
§ When the breaker is opened while the current is passing, a high-temperature spark is formed that leads to the evaporation of a small portion of the oil. This evaporation leads to the formation of gases (70% of which are hydrogen). Hydrogen has the property of rapidly cooling the spark, which leads to its extinguishing. After extinguishing the spark, the gases exit to the upper part of the spark. The key is that it can mix with oxygen to form flammable gases, so the hydrogen must come out cold to the surface.
§ These breakers are vulnerable to increased pressure, so the tank mounting bolt “7” is installed Sideways to allow the tank to be separated from the upper part during increased pressure
§ An internal spark may occur between the faces and each other or between them and the tank when there is increased humidity in the oil or increased pollution.
Therefore, the following must be followed when operating oily switches
1- Ensure that the oil level in the cutter matches the mark on the oil level indicator.
2- Cleanliness of the ventilation hole.
3- The external contact points with the distribution bars in the cell must be strong and smooth to achieve good contact.
4- The fixed and moving internal contact point must be strong to achieve good contact, knowing that the lack of strong contact inside or outside the oil tank leads to an increase in the temperature of the contact point and thus leads to an increase in the temperature of the oil with the passage of high currents that may lead to the oil igniting during separation. With the palace.
5- Ensure that the oil is safe and conforms to technical specifications.
Second: The breakers are low in oil
Low-oil circuit breakers are designed to have the following properties:
1- Oil is used to extinguish the spark only, and the amount of oil is small but sufficient to extinguish the spark
2- The tank is designed to withstand high mechanical stresses and is therefore safe against explosions
And ignition if proper operating methods are followed
3- The body of the cutter is connected to the constant voltage Live-Tank
4- The cutter’s body is isolated from the ground with mounting insulators, which are made of Persulene.
Abox ” Figure 2 “
Installation:
Figure “2” shows Installing one of the low-oil breakers ” Russian type ” It is used in medium voltage networks and consists of three current units for three phases, and each unit is installed in the circuit breaker “Figure 3”. Of moisture-absorption-resistant insulating tube “6” – It is connected on both sides by metal parts (the upper part “7” and the lower part “3”)
In the upper part:-
From the cutter there is a moving contact point “8” And the mechanical parts for separation and connection – the upper part has the “11” entry hole. And the ventilation hole is “12”
And in the lower part:-
From the cutter there is a fixed contact point “2” And the spark extinguishing chamber “4” And oil level indication “5” It is noted that the oil level must cover the spark chamber, and there is a hole in this part to extract the oil “13”. When the switch is disconnected, a spark is generated between the two contact points inside the chamber – the spark chamber cuts the spark – and the oil extinguishes it.
[]Components of electrical circuit breakers
1- Bottom cover
2- Fixed contact points
3- The lower part of the body
4- Spark room
5- Oil level indication
6- A cylinder of insulating material to absorb moisture
7- The upper part
8- Moving contact points
9- Cylinder to facilitate movement
10- Oil return sump
11- Oil entry hole
12- Ventilation hole
13- Oil leakage
Precautions to be followed when operating low-oil switches:
1- Change the oil every 3 times due to a short circuit in the network.
2- Take care not to reconnect after disconnecting the breaker during the short peak hour.
3- Take care not to perform disconnection and connection maneuvers on normal loads during peak hours.
4- Be careful not to reconnect it immediately after disconnecting the switch – but it must be reconnected after that
Sufficient time for the oil to return to its normal temperature.
5- Check the oil level in the switches.
6- Ensure that there is no oil leakage.
7- Follow regular maintenance procedures.
8- Set class times to the stipulated times
Therefore, the following must be adhered to:
1. Numbering the keys in the station for ease of following, operating and monitoring the keys.
2. Make a record to track the number of times of short-term and regular dismissal.
3. Creating prevention records to record device control and tests.
Disadvantages of using electrical oil as a medium to extinguish the spark:
1- The lifespan of the contact bits in the switches is short and requires frequent and frequent maintenance
2- The possibility of popping is high because the gaseous products from the oil analysis after extinguishing the spark are formed
Flammable
3- Arc recoil tendency
4- Uneconomical use in industrial loads that need to be disconnected and restarted
Frequent delivery.
5- The duration of the electric arc at low currents is large.
6- Humidity and dust reduce the intensity of electrical isolation
For these reasons, research turned to the necessity of using another medium to extinguish the spark – sulfur hexafluoride gas, SF6, which has excellent and multiple properties that help eliminate all of these aforementioned defects in the use of electrical oil in electrical breakers, as well as the use of vacuum breakers.
Third, vacuum circuit breakers:
Operating theory
The theory of operation of these breakers depends on the absence of a spark during separation of the connection points inside a vacuum medium – and the vacuum medium has a high quality of insulation in relation to air insulation, and this property helps to reduce the distance between the separation points to millimeters, which helped reduce the separation time for the breakers. .
Installation
“Figure 4” It shows the installation of the breaker used in the EGIMAC 11 KV distribution panels. We find that the breaker unit is composed of:
A vacuum metal spark chamber containing fixed and moving contact points connected to the mechanical parts for separation and connection – and the upper points are the fixed points.
Penetrating insulators for fixed and moving points are installed above and below the spark chamber to prevent an electric arc from occurring outside the spark chamber.
Precautions to be followed when operating:
1- Do not expose the cutter to any mechanical shocks that may lead to a breakage of the cutter.
2- Clean the upper and lower penetration insulators of the cutter from dust and moisture.
3- Recording short disconnection times and the normal load for each circuit breaker.
Fourth: Circuit breakers charged with sulfur hexafluoride gas
Sulfur hexafluoride gas is used as a medium to extinguish a spark or an electric arc, and it is used as an insulating medium due to the following properties:
1 – It has an ability equal to 2.5 insulating strengths of air at atmospheric pressure, and the insulating strength can be increased to 10
Air isolation times increase in pressure
2- A density higher than that of air
3- It has the ability to absorb electrons, which cause sparks, and turns into fluoride hexa gas
Sulfur.
4- It has a high cooling capacity that helps extinguish the spark
The cutter charged with sulfur hexafluoride gas is used in 11 KV Arab distribution panels. Breakers of this type are similar in structure to low-oil breakers in that there are moving contact points and fixed contact points – but these points move in a medium charged with sulfur hexafluoride gas.
It is connected to the charged tank and is shown to indicate the gas pressure level inside the cutter.
When operating these circuit breakers, the following must be taken into account:
1 – Monitor the gas pressure inside the spark chamber and record it during the shift
2- Take care not to use force and expose the keys to mechanical shocks that may lead to their breakage and gas leakage
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