Theory of Corona, Discharge & Generation

Theory of Corona Formation:

Corona discharge is a process by which a current flows from an electrode with a high potential into a neutral fluid, usually air, by ionizingthat fluid so as to create a region of plasma around the electrode. The ions generated eventually pass charge to nearby areas of lower potential, or recombine to form neutral gas molecules.

Some ionization is always present in atmosphere due to cosmic rays, ultra violet radiation ,and radioactivity. There for normal(low voltage) voltage no any formation of corona, but at the point of high voltage(nearly 30kv) at which corona accrued is called Critical Disruptive Voltage (it is minimum phase to neutral voltage at which corona occurs).

When potential gradient is reach above 30kv per cm value the velocity of electron acquire by electron is sufficient to strike  a neutral molecules with enough force to produce more electron from it. This process is continue with potential gradient, the result of this corona occurs as a spark between conductor. it is called Visual Critical Voltage (it is minimum phase to neutral voltage at which corona glow appears around the conductor).

Photo of Corona Formation:

Large corona discharges (white) around conductors energized by a 1.05 million volt transformer in a U.S. NIST laboratory in 1941

Corona Discharge vs. UV Ozone Generation

Ultraviolet (UV) ozone generation

Ultraviolet lamps have been used for decades to generate ozone.  This lamp emits UV light at 185 nanometers (nm). Light is measured on a scale called an electromagnetic spectrum and its increments are referred to as nanometers. 

Air (usually ambient) is passed over an ultraviolet lamp, which splits oxygen (O₂) molecules in the gas. The resulting oxygen atoms (O^-), seeking stability, attach to other oxygen molecules (O₂), forming ozone (O₃).

Critical to CD ozone systems is proper air preparation. The gas feeding the ozone generator must be very dry (minimum -80 degrees F), because the presence of moisture affects ozone production and leads to the formation of nitric acid. Nitric acid is very corrosive to critical internal parts of a CD ozone generator, which can cause premature failure and will significantly increase the frequency of maintenance.

Advantages of Corona Discharge ozone generation

1. Corona discharge ozone generators can use oxygen preparation thereby doubling the ozone output per given volume vs. dry air
2. Can create a more pure form of ozone without creating other harmful or irritating gases if using dry air or oxygen as a feed gas
3. Can create high quantities of ozone (up to 100-lbs/day)

Disadvantages of UV ozone generation

1. Considerable more electrical energy is required to produce a given quantity of ozone by UV radiation than by corona discharge.
2. UV lamps solarize over time, requiring periodic replacement

Difference between...!!!!

Difference between CT and PT

Current Transformer 

The secondary of a C.T can not be open circuited on any circumstance when it is under service. 

The primary winding of the CT is connected in series with the line carring the current to be measured. Hence it carries of the full line current. 

Potential transformers are used in usually in industrial and power plant settings to reduce the AC voltage of a power line to a lower value (typically 120 or 70 volts full scale) for instrumentation purposes. They are low power, have accurate voltage ratios and good galvanic isolation to isolate the instrumentation (and the operators) from dangerous voltages and power. Potential transformers can be wire-wound like a small power transformer or for very high voltages can take the form of a capacitive voltage divider or can exploit the electrical properties of optical materials. 

Transformers designated as current transformers have far more limited uses. Current or current sense transformers only lower current for use in meters and measuring devices, with little regard for power or voltage changes.

Potential transformer 

The secondary of a P.T can be open circuited without any damage being caused either to the operator or the transformer. 

The primary winding P.T is connected across the line of voltage to be measured. Hence the full line voltage is impressed across its terminal.

Current transformers are used to scale a large AC current which can be 10s of thousands of amps or more to be measured to a lower value, typically 1 or 5 Amperes that does not require heavy wires to carry the full current flow to be measured into the instrumentation. They are low power, do not disturb the current to be measured, have accurate current ratios, and like potential transformers, good galvanic isolation to isolate the instrumentation (and the operators) from dangerous voltages and power. 

Potential, power, or voltage transformers change commercial power from generators to high voltage and low current for nationwide distribution. Substations use similar transformers in reverse to reduce the voltage and increase the current to usable levels. 

Recent Trend In Electrical Technology

Smart Grid & Their Application in the Grid System

What is Grid?

Concept of smart grid is quite in the news and market but majority of the people actually don’t know that what exactly are the things which make a grid smart?

The term “Grid” refer to an “Electric Grid” basically describes a complete network which includes transmission lines, transformers, distribution substation all accessories that are used for delivery of electricity from generation plants to home and commercial scale.

The very first grid was built in decade of 1885-1895 and the with the passage of the time number of grids kept on increasing that’s why by now there are about more than 9200 grids all over the world which are providing about 1 million Megawatt power to the consumers.

As evolution has a direct relation with time so for an efficient functionality of grid, digital technology has been introduced in grid system. This new digital technology enables two way communications which guarantees the direct link between utilities and all consumers.

What is a Smart Grid Then?

In simple words, an automation system between utility and consumers. This smart grid consist of advance digital system, automation, computer and control which make sure to perform a duplex “two way” communication between the power provider and load consumer. 

In a typical electrical grid system, electricity provider only will know the power failure when a costumer call them. But in case of smart grid system, if electric supply fails, service provider will automatically respond to the affected area because the components of smart grid  provides enough data i.e. from the power transformer, maintransmission and distribution system and finally, to the home supply system (you may say the utility meter).

What Things Make a Grid “Smart”?

According to the Department of Energy (United States), Four types of advance technology will transform a typical electrical grid into Smart Grid which are as follow:

1. Fully automated and Integrated two way communication between the overall components of an electric grid.
2. Automatic Control for power distribution, faults and repairs.
3. Advance management panel, decision support software and mechanism.
4. Accurate sensing and measurement technologies.

Upgraded technology of smart grids has well-organized automation equipment and control system, whose response is accurate to meet the rapidly increasing demand for electricity. Time when these smart grids were not implemented all utilities companies were bound to send their respective workers to take meter reading and acquire data related to consumer.

What does a Smart Grid do?

Smart grid performs lots of smart jobs  . Some advantages of a smart grid are stated follow:

Efficient Transmission and Distribution of Electric Power.
Quickly restore electric power after power failure due to faults.
Lower cost for operation, maintenance, management  and electricity for both utilities and consumers.
Lower electric power tariff and rates due to reduced peak demand.
Provide better options of integration of renewable energy for self power generation systems.
Improve the security and protection.

Applications of a Smart Grid System.

Deployment of Digital Technology in smart grids ensures the reliability, efficiency and accessibility to the consumers regarding all utilities which count towards the economic stability of the nation. Right at the start of transition time it become perilous to execute testing, to improve the technology by up gradation, developing and maintaining standards on a standard threshold and also application of these efficient grids serve all these problems

Basic applications of smart grids are

• They improve the adeptness of transmission lines
• Quick recovery after any sudden breakage/disturbance in lines and feeders
• Cost Reduction
• Reduction of peak demand
• They possess the ability to be integrated with renewable energy sources on a large level which leads to sharing of load and reduction of load on large scale