Looking for answers on what makes Air-insulated switchgear different from gas insulated switchgear?
You are lucky because we’ve got you covered!
You see,
The differences between the gas insulated substation and air insulated substation are massive.
You will find five major deliberations in the differences between the two HV substations.
In this post, we will categorize all of them.
Ownership
When we talk about ownership, it talks about the total cost of having the equipment.
On a deep level comparison, you need to weigh the upfront expenses of GIS an AIS against the needed lifelong maintenance.
Such units basically have a thirty-year minimum life span.
In fact, gas insulated switchgear is more likely to cost between ten percent to forty percent more than air-insulated switchgear.
Maintenance
In case you didn’t know yet
Gas insulated substations need less maintenance.
On standard, GIS require to be inspected visually every 4 years or more.
That depends on the particular manufacturer suggestion for your device.
Gas insulated switchgear only require to be re-greased after at least twenty years.
Take note that this differs among manufacturers.
AIS must be inspected each year visually to two years.
Once evaluated, every compartment should be assessed.
Compared to GIS, the individual elements and compartments are insulated and could be tracked.
On average an AIS breaker will require at least 4 hours of maintenance for every 2-year time.
When we talk about maintenance, Air-insulated switchgear need more effort.
That’s true especially because of the carefulness of the inspections.
You see,
Inspections cover having:
- a technique torque
- clean
- draw out
- lubrication
- vacuuming the unit
Furthermore;
They must be checked for visual indications of copper corrosion.
That is something, which does not happen in gas insulated switchgear because the units are sealed.
That sealing also safeguards the components from environmental damage.
Operation
Gas insulate systems are simpler to care.
That’s because they provide front rather than rear access.
They also offer their own integrated testing instruments.
You see;
Arc flashes are very rare in a gas insulated substation.
That’s mainly because all the interior elements are insulated.
The cable compartment is only accessible too.
Now, because the parts are insulated, no linkage or cables could come in contact along with the live parts.
Setting up
On the other hand;
Installing a gas insulated system could be quicker than installing its metal-clad counterpart.
That’s mainly because GIS is smaller and weightless.
GIS substations are faster to install, provided the technician does not need to manage the gas.
The average installation period is lowered by at least 30 percent along with a GIS installation.
GIS substations take up less space than air-insulated substations.
Moreover, the physical footprint of a gas-insulated substation is at least 35 less than AIS.
Structure
The last factor you need to consider the structure of the equipment.
The gas insulated system utilizes a gas sulfur hexafluoride for insulation.
Meanwhile, AIS utilizes air insulation within the metal clad system.
As you can see,
SF6 is five times bulkier than air.
It also provides great extinction behavior.
AIS employs 3-position draw out circuit breakers.
GIS substations utilize mounted and fixed circuit breakers.
The sealed mounted beakers are considered ‘sealed-for-life’ technology.
On the contrary;
AIS switchgear could be eliminated for troubleshooting and maintenance.
Design Standards
When it comes to design, AIS has:
IEC (e.g. IEC 62271-1, IEC 62271-200, IEC 62271-100 …etc)
While GIS features IEC (e.g. IEC 62271-1, IEC 62271-200, IEC 62271-100 …etc)
The media utilized for switching in AIS is air, SF6, vacuum or oil while SF6 or vacuum is utilized in GIS
Size
Regarding the size:
AIS is bigger as clearances are in the air.
Therefore some safe clearances should be kept to satisfy the dielectric performance.
On the other hand, GIS is smaller.
That’s because it combines more than a single function in one gas tank
It lowers overall lineup footprint and dimensions too.
Sensitivity to Pollution
GIS is excellent.
The gas tank offers high ingress protection with IP67 with less sensitivity to humidity, altitude, and environment.
Meanwhile, AIS is moderate
Humidity and pollution can have impacts on insulation, which is exposed to air
Cable termination requirements
AIS doesn’t need any particular requirements.
Normal cable termination types could be utilized.
GIS on the other side needs particular cable terminations.
This is to keep proper insulation with lowered air clearances in cable connection compartment
Type of execution with switching devices
GIS has fixed switching devices while AIS have drawn out according to design
Modularity
The modularity of GIS depends on the design of the range.
You see future extension must be considered at early phases.
Including future functions could be realized along with some limitation about the number of extensions
Meanwhile, AIS has modular by nature of the design.
The future functions could be included through an extension process without particular limitations.
In a nutshell, AIS provides more flexibility toward upgrades and extension
Need for gas pressure monitoring
GIS might need for both switching devices and busbars integrating SF6 gas.
AIS might need only for switching devices integrating SF6 gas.
To sum up,
We hope in this short comparison, we’ve provided you helpful insights about the differences between GIS and AIS.