Vacuum insulated switchgear is a type of electrical safety equipment that uses vacuum for insulation instead of air or any other medium. This makes it superior to several other types of electrical switchgear in a number of ways. Here, we will take a look at these vacuum switchgear advantages and how they benefit users.
What Does Switchgear Mean?
Before we can discuss the benefits of vacuum switchgear, you may want to know what switchgear means. In very simple terms, switchgear is a type of electrical apparatus that contains devices to protect and control electrical circuits and equipment.
Switchgear forms an essential piece of equipment where electricity is heavily used. This includes residential buildings, factories, power plants, and other facilities such as utility installations and power generating stations.
Vacuum Insulated Switchgear
When switchgear circuit breakers or isolators and other devices stop the flow of electricity, an arc is created. This can cause extensive damage to the equipment if not properly managed. Arcing is also a safety risk to switchgear operators.
In order to effectively control the arc, the switchgear must be properly insulated.
Different insulation mediums such as air, oil, and gas may be used— or all matter can be evacuated to remove molecules that may ionize and propagate the arc. This is what gives rise to vacuum insulated switchgear- or VIS for short. So, what is a vacuum circuit breaker and what does it do? See below.
Vacuum Circuit Breaker Function
As the name suggests, vacuum switchgear uses a vacuum to dissipate an electrical arc. The vacuum is created by evacuating the air from a sealed chamber. Once the desired level of vacuum has been reached, the chamber is sealed and the switchgear can be used.
A vacuum circuit breaker is designed with the breaking contacts in a steel, vacuum chamber. The chamber is then encased in a glass or ceramic insulator.
During operation, the moving contact, which is usually made from a copper alloy, is actuated by a magnet or spring. Its action breaks the connection, resulting in an arc that’s quickly broken in the vacuum environment. This is what gives the vacuum fault interrupter switchgear its many advantages.
Advantages of Vacuum Insulated Switchgear
The use of vacuum circuit breaker switchgear provides several advantages over other types of insulation mediums, which makes it more attractive to use in a variety of situations— especially medium voltage systems. Let’s take a look at some of them.
1. Superior Dielectric Strength
The dielectric strength of a vacuum is far superior to that of air or any other gas. Dielectric strength means the ability of a material to withstand electric stress without breaking down. A vacuum has an infinite dielectric strength as not many molecules are present to ionize and propagate an arc.
The higher dielectric strength of vacuum insulated switchgear results in a number of benefits. For one, it allows for a much higher voltage to be used in the equipment. Two, it allows for a much shorter distance between the breaker contacts for more compact switchgear components.
2. Better Arc Quenching
The effectiveness of a circuit breaker is measured by its ability to quench an arc. An arc is created when the circuit breaker breaks the flow of electricity. This arc must be quickly extinguished to avoid damage to the equipment.
In a vacuum circuit breaker, the vapor of the metal contacts when the arc first occurs provides ions that could prolong the discharge. But this vapor quickly settles on the contacts, leaving the arc with nothing to advance it. This is what we call ‘arc quenching’, which is better when the dielectric strength is higher.
3. Simpler Breaker Mechanism
Unlike circuit breakers using insulation mediums such as air and SF6, vacuum switchgear operates in an almost matter-free environment. This means a simpler mechanism to operate it. In other mediums, the contacts are normally in a pressurized chamber and not easy to move.
The contacts of a vacuum breaker are also close together. That in itself makes the breaker compact and simple enough to open and break. As a result, it’s possible to use a simple spring to actuate the moving contact during the current breaking action.
4. Almost Maintenance-Free
Switchgear circuit breakers have to open contacts in high voltage and high voltage currents. This produces an arc that gradually wears off the contacts. When the dielectric strength of the insulating medium is not high enough, it can mean accelerated erosion and higher switchgear maintenance needs.
Vacuum circuit breakers do not suffer extreme arcing when breaking the flow of electricity and contact erosion is minimal— almost non-existent. That means they do not require frequent maintenance. In addition, it means breakers that will last longer than those that use air and gas.
5. Increased Safety
The use of vacuum in switchgear makes it safer in two ways. First, eliminates the need for any material that may harm the environment such as SF6 gas. So there is no chance of the equipment leaking any harmful gases into the environment, which makes vacuum breakers an eco-friendly option.
Secondly, with vacuum insulated switchgear, the arc is quickly extinguished by the high dielectric strength of the vacuum. This means there is no danger of damage to equipment, fires starting or risk to switchgear operator safety.
Vacuum Circuit Breaker vs. SF6 Breaker
As we have seen, vacuum switchgear breakers use evacuated chambers to provide insulation. SF6 gas switchgear is a comparable option. So, what’s the difference between the two types of equipment? Let’s find out in this brief comparison between vacuum and sf6 circuit breaker switchgear.
Different Insulation Mediums
The most obvious difference between vacuum and SF6 circuit breaker operation is the fact that they use different insulation mediums. As we have seen, vacuum breakers use a vacuum to provide the required insulation, while SF6 circuit breakers rely on sulfur hexafluoride gas.
Different Operating Pressures
Another difference between vacuum and SF6 breakers is the operating pressure. Vacuum breakers operate at a much lower pressure than SF6 circuit breakers. As a result, these breakers can handle higher voltages and use simpler operating mechanisms.
Different Environmental Impacts
Another notable difference between vacuum and SF6 switchgear is the environmental impact. As we have seen, vacuum breakers do not use any harmful materials, so they have no negative impact on the environment. SF6 circuit breakers, on the other hand, use sulfur hexafluoride gas, which is a greenhouse gas.
In terms of which breaker is better, it really depends on the application. If safety is critical, then vacuum circuit breaker switchgear may be the best option. However, if cost is a concern in higher voltages, then an SF6 breaker may be a better choice.
Both types of breakers have their own advantages and disadvantages, so it’s important to choose the one that’s best suited for the application.
Vacuum insulated switchgear is a reliable and safe option for many electrical applications. It has many advantages over many other types of switchgear, including a longer life expectancy, better arc quenching, and minimal maintenance requirements.
However, it’s good to note that vacuum switchgear is more expensive than other options when it comes to higher voltages above 38Kv. As such, it’s important to weigh the cost against the benefits before making a decision.