Thursday, 29 February 2024

Maintenance Testing Of SF6 Gas Vacuum Circuit Breakers

Introduction Of "Maintenance Testing Of SF6 Gas Vacuum Circuit Breakers":

In This Post, We Will Understands The Procedures Of Maintenance & Testing Of Vacuum Circuit Breakers And SF6. It Is Necessary To Examine These Units To Check For Physical Harm And Erosion From Impurities In The Insulation And Oil.

Let's Understand The "ASPECTS OF SF6 GAS (SULFUR HEXAFLUORIDE)":-

Toxicity: In Its Pure Form, Sf6 Has No Taste, Color, Smell, Or Toxicity. Suffocation Could Result From It, Though, As It Can Cut Off Oxygen. Suffocation May Happen Suddenly If The Air's Typical Oxygen Content Drops From 21% To Less Than 13%. Circuit Breaker Tanks Should Therefore Be Emptied After Opening.

Toxicity Of Arc Products: When An Electric Arc Is Applied To Sf6 Gas, Toxic Breakdown Products Are Produced. Metal Fluorides, Which Result In A White Or Tan Powder, Are The Breakdown Products. Additionally, Toxic Vapors With A Rotten Egg Stench Are Generated. Avoid Breathing In The Fumes That Are Still Present In A Circuit Breaker That Has Experienced Arcing Or Corona Discharges. Before Servicing The Circuit Breaker, Remove The Defective SF6 Gas From It And Cleanse It With Fresh Air.

Physical Characteristics: SF6 Has A Density Of Almost Five Times That Of Air Under Identical Conditions, Making It One Of The Heaviest Known Gases. Sf6 Is A Soft Gas Because It Is More Dynamically Compressible Than Air And Exhibits Little Change In Vapor Pressure Across A Broad Temperature Range. Sf6 Has A Heat Transfer Coefficient Higher Than That Of Air And Has Convection Cooling Properties That Are Roughly 1.6 Times Larger Than Air's.

Dielectric Strength: For A Given Electrode Spacing, Sf6's Dielectric Strength Is Roughly Three Times That Of Air At One Atmosphere Pressure. The Dielectric Strength Grows As Pressure Rises, Reaching A Roughly Similar Value To Transformer Oil At Three Atmospheres. Circuit Breakers That Employ Sf6 Heaters Must Prevent The Gas From Liquefying Because Liquefying Gas Lowers Dielectric Strength Due To A Drop In Pressure. Electrode Spacing, Arrangement, And Electrical Setup All Affect The Precise Dielectric Strength In Relation To Air.

Arc Quenching: Sf6 Quenches Spurious Arcing Around 100 Times More Effectively Than Air. Additionally, Sf6 Has A Large Thermal Heat Capacity, Allowing It To Absorb Arc Energy Without Experiencing A Significant Temperature Increase.

Electrical Arc Breakdown: Corona And Arcing In Sf6 Do Not Happen Until Much Later Than The Voltage Level At Which Corona And Arcing In Air Begin Due To SF6's Arc-quenching Capabilities. If SF6 Is Continuously Exposed To Corona, It Will Gradually Degrade.

Every By Product Of SF6 Breakdown Or Arc Is Hazardous. Small Amounts Of Arc Products Are Produced During Current Interruption During Typical Circuit Breaker Operation, And These Products Typically Recombine To Sf6. Molecular Sieve Filter Material In Circuit Breakers Often Removes Arc Products That Either Do Not Recombine Or Combine With Any Oxygen Or Moisture Present.

Managing SF6 Without Errors.

The Instruction Manuals From The Manufacturers Go Into Great Detail About How To Handle Sf6 That Is Not Defective. Typically, These Procedures Entail Taking The Sf6 Out Of The Circuit Breaker, Filtering It, Storing It As A Liquid In A Gas Cart, And Then Putting It Back In The Circuit Breaker Once The Circuit Breaker Maintenance Is Finished. Sf6 That Is Not Defective Does Not Require Any Particular Clothing Or Safety Measures.

Managing Erroneous SF6.

Hazardousness.

Failed SF6 Gas: This Gas Has An Odor Similar To Rotten Eggs And Can Irritate The Upper Respiratory Tract And Eyes, As Well As Produce Nausea. Normally, Faulty Sf6 Gas Smells So Bad That No One Can Endure Prolonged Exposure At A Level That Could Permanently Harm Them.

Solid Arc Products: Solid Arc Products Are An Ash-like, White Or Off-white Powder That Is Poisonous. Skin Contact May Result In Discomfort Or Perhaps A Painful Fluoride Burn. In The Event That Solid Arc Products Come Into Contact With Skin, Thoroughly Wash The Area Right Away With Lots Of Water. Use A Vacuum To Remove Arc Products If Water Isn't Accessible.

Requirements For Clothing And Safety Gear.-

The Following Gear And Clothing Should Be Used When Handling And Extracting Solid Arc Products From Faulty Sf6:

Coveralls: When Removing Solid Arc Products, Coveralls Must Be Worn. Once All Solid Arc Products Have Been Cleaned Up, Coveralls Are Not Necessary. When Removing Solid Arc Products, Disposable Coveralls Are Advised; However, If Disposables Are Not Available, Conventional Coveralls Can Be Worn As Long As They Are Cleaned At The End Of The Day.

When Extracting Solid Arc Products From A Malfunctioning Dead-tank Circuit Breaker, Hoods Must Be Worn.

Gloves: When Handling Solid Arc Products, Gloves Are Required. It Is Advised To Use Inexpensive, Disposable Gloves. After Use, Non-disposable Gloves Need To Be Cleaned In Water And Allowed To Air Dry.

If A Full Face Respirator Is Not Being Worn, Safety Glasses Are Advised When Handling Solid Arc Products.

Wearing A Cartridge-style Respirator Is Necessary While Accessing A Dead-tank Circuit Breaker That Has An Internal Issue. The Respirator Should Only Be Used When There Is Enough Oxygen In The Air To Sustain Life, As It Does Not Provide Oxygen And Will Only Remove Solid Arc Products From The Air That Is Breathed.

When An Odor Is Detected By The Respirator, The Filter And Cartridge Need To Be Replaced. When Working On Circuit Breakers With Interrupter Units That Are Well-ventilated And Too Small For A Man To Penetrate, Respirators Are Not Required.

When A Cartridge Type Is Unsuccessful Because It Offers A Work Period That Is Too Short Before The Cartridge Becomes Contaminated And An Odor Is Detected, Air-line Respirators Should Be Utilized.

Before An Employee Enters The Circuit Breaker Tank When Using An Air-line Respirator, There Must Be A Minimum Of Two Respirators In Operational Condition On The Premises.

Waste Disposal: All Materials Utilized In The Large-scale Sf6 Arc Product Cleanup Operation Must Be Disposed Of As Hazardous Waste In A 55-gal Drum.

The Following Things Need To Be Thrown Away:

A. Every Solid Arc Product; B. Every Disposable Protective Gear; C. Every Cleaning Cloth; D. Respirator Filter; E. Molecular Sieve From Gas Cart And Breaker; F. Vacuum Filter Element.
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