Corona ring design guide is all about how you design the corona ring in transformer bushings, insulators, transmission lines, substations, high voltage laboratory, surge arresters and more.
The corona ring design and parameters affects the corona effect of real high voltage applications.
If you are the beginner of this area, just reading this guide and you will be able to get a clear and a crisp understanding of that.
CHAPTER 1: Why Is Corona Ring Design Important?
What Is A Corona Ring?
The corona ring is one of the most important parts of the high voltage testing equipment, and it’s also the first choice for many HV engineers, products managers and end users.
For the corona ring, it is an ideal device for corona treatment.
Generally the corona ring needs to be polished bright to achieve more smooth and no burr surface finish to ensure better corona control effect.
The corona rings are made of pure aluminum and alloy, with a surface treated by polishing or anodic oxidation, which makes it have a good surface hardness, dielectric strength and impact resistance. It also has a good insulation and can be easily repaired by grinding.
What Is The Purpose Of A Corona Ring?
A corona ring is an electrical device used to minimize the corona effect, which is due to high voltage and low current.
Corona rings are designed for transformers or power lines that operate at high voltages.
Corona rings are used essentially in high-voltage AC transmission lines and substations, where they are installed near the conductors in order to mitigate the negative effects of the coronal discharge.
The corona ring provides an alternative path for the electrons to move, preventing them from arcing between lines. This reduces noise, improves power quality and increases power factor. This can also extend the life of the transmission line by reducing ionized air particles that can damage insulation.
How Does The Corona Ring Work?
Corona rings are used to increase the voltage across a component or surface. Corona rings are generally made of aluminum and used in overhead power lines to increase the surface potential and reduce corona loss. These rings are mounted on crossarms.
Corona is an ionized gas occurring naturally in the environment, which can also be produced artificially by high-voltage electrical discharges.
Corona is generally unwanted, especially in electricity transmission where it wastes energy, increases conductor corona loss and radio interference, and can cause damage to insulators. Corona discharge from conductors may also produce ozone (O3) as a pollutant and can cause noise or audible sound.
High voltage corona discharges occur around most high voltage equipment such as power lines and transformers; the electric field strength required for corona depends on air density, moisture content, presence of contaminants or dust, insulation type, shape of the conductor, etc., but is typically 30–40 kV/cm for dry air at sea level pressure (atm).
At lower voltages the air is normally an insulator; however, as voltage increases a stage is reached where small areas of ionization occur and current flows through these paths creating characteristic “streamer” discharges.
CHAPTER 2: Corona Ring Design Parameters Optimization
Corona Ring Outer Diameter
The corona ring outer diameter is measured across the outside of the corona ring.
The outer diameter of corona ring depends on high voltage testing level.
As the high voltage level becomes higher, the diameter of the corresponding corona ring must be enlarged.
Corona ring with a larger outer diameter is better for corona shielding effects of tests.
Here we should introduce Highv design and processing capabilities of the large outer diameter of corona rings in impulse voltage generator system.
The biggest diameter dimension of one ring is 16000mm. And pipe inner diameter of ring is 3000mm.
Corona Ring Inner Diameter
The corona ring inner diameter is a measurement of the inside diameter of corona ring.
For a given corona ring, it is the largest possible inner diameter that would result when the ring is stretched to its maximum inside diameter.
The corona ring inner diameter is used in tolerance calculations for molded rubber and extruded rubber parts.
Pipe Wall Thickness And Outer Diameter
The measurements of pipe wall thickness and outer diameter is important to know the bending capacity of pipe production.
It is also important to know the weight of the pipe in accordance with its diameter, because it is proportional to the square of its radius.
The weight of a pipe with a diameter of 100 mm will be almost twice that of a pipe with a diameter of 50 mm.
In common usage the words pipe and tube are usually interchangeable, but in industry and engineering, the terms are uniquely defined.
Depending on the applicable standard to which it is manufactured, pipe is generally specified by a nominal diameter with a constant outside diameter (OD) and a schedule that defines the thickness.
Tube is most often specified by the OD and wall thickness, but may be specified by any two of OD, inside diameter (ID), and wall thickness. Pipe is generally manufactured to one of several international and national industrial standards.
While similar standards exist for specific industry application tubing, tube is often made to custom sizes and a broader range of diameters and tolerances.
So choosing the right size aluminum pipe is good for corona ring design and production.
Angle Of Inclination
The angle of inclination is the angle between a reference plane and another plane or line.
For example: If a line is inclined at 30°, it means that the line makes an angle of 30° with the reference plane (here the standard is corona ring).
Phase To Phase Spacing
Phase to phase spacing, or the distance between two corona rings, is an important consideration in the design of electrical systems.
This is why it is important that all electrical engineers and designers have a good understanding of what phase-to-phase spacing is and why it is so important.
So our team will help define phase-to-phase spacing between corona rings, discussing its importance, and providing some examples of when it can be used.
Mounting Bracket Design
The design of a mounting bracket is influenced by the way that the bracket will be used.
A mounting bracket must hold corona rings firmly in place and be resistant to displacement due to vibration, shock, heat, cold or other environmental factors.
The design of a mounting bracket begins with a determination of the size of the corona ring that is to be mounted, its weight and the anticipated loads that it will be subjected to during its use.
The surface where the bracket will be mounted should be considered along with the environmental conditions that are expected. Once these factors are known, an appropriate design can be made for a mounting bracket.
The choice of materials for a mounting bracket is influenced by the size and weight of an object as well as its intended use.
A large or heavy weight corona ring may require steel or iron construction while lighter items may use aluminum or stainless steel brackets.
The corona ring manufacturer should consider whether or not welding or riveting is required to construct a mounting bracket so that it maintains its structural integrity during its anticipated use.
Single Ring VS Corona Ring Set
Here two types of corona ring will be introduced.
One is single ring without any brackets.
Single Corona Ring Design:
- The Right Aluminum
- Outside Diameter
- Inner Diameter
- Pipe Diameter
- Wall Thickness Of Ring Body
Another one is known as corona ring set.
It is also known as phase to earth ring set.
The detailed design drawings will be offered by customers. So the finished corona ring will be produced as different applications.
Of course highv team could also help customer redesign new moulds and drawings.
Corona Ring Set Design:
- The Right Aluminum Material
- Outside Diameter
- Inner Diameter
- Pipe Diameter
- Wall Thickness
- The Horizontal Welding Bracket
- The Vertical Welding Bracket
- Other Welding Part
- Installed Flange Tube
- Other Fasteners (Nut, Bolts, Gasket, Lifting Eye, etc)
Corona Ring Design In Practice
Corona ring design is an important part of corona performance.
The design of corona rings will have a large impact on the cost and performance of the UHVDC converter.
In practice, it is quite difficult to make a corona ring that is perfectly round, but we have found that even with imperfections in the ring shape, we still get good results.
Corona ring design is a beautiful and unique way to create a piece high quality corona ring.
We hope you enjoyed our ultimate guide to corona ring design.
Now we’d like to hear from you: which tip from our’s guide are you going to learn first?
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