Measurement of Air Breakdown Voltage: Sphere Gap Method Report

This report details a student's project on measuring air breakdown voltage using the standard sphere gap method. The project involved understanding the principles of air breakdown, including streamer and Townsend theories, and designing experimental setups with sphere gap arrangements. The student, acting as team leader, managed the project, defined objectives, and oversaw the experimental procedures, including considerations for environmental factors like temperature and pressure. The report outlines the application of engineering knowledge, calculations for air density and humidity corrections, and the analysis of results obtained from varying sphere distances. The student's responsibilities included team management, testing arrangements, and ensuring the accuracy of the results. The project aimed to determine the air breakdown voltage for high-voltage equipment insulation design, with detailed attention to electrode configurations and the impact of environmental conditions. The report concludes with a project overview, highlighting the student's contribution and the successful determination of air breakdown voltage through various calculations and experimental setups.

COMPETENCY
DEMONSTRATION REPORT
Career Episode 2
SRI CHANDANA MUTHARAJU

CE 2.1 Project Information
Name of the project: Measurement of Air Breakdown Voltage Using Standard Sphere
Gap Method
Location of the project: [PLEASE FILL]
Project Duration: [PLEASE FILL]
Organization: [PLEASE FILL]
Role and Designation during the time: Team Leader
CE 2.2 Project Background
CE 2.2.1 Characteristics of the project
Power growth has been continuously increasing in every country and so it was in mine.
High Voltage power equipment are the greatest concern in the sector of the power generation and
I had interest in this region of concern. The insulations might became waste due to many actions
and might behave as a conductor when the voltage went equals the air breakdown voltage
between the gaps. Air gaps behaves as the insulator in high voltage electrical works those in
addition uses many liquid insulations such as solid insulation (paper, polyester), (transformer oil,
and gas insulation (N2, SF6, CCl2F2 CO2, and many more). I was aware with the fact that air
breakdown voltage is 30 kV/cm and it has greater significance on the insulation design for the
high voltage electrical equipment. I had attempted to determine breakdown voltage
experimentally that was delivered at standard temperature and pressure and had diameter of 25
cm.

CE 2.2.2 Objectives developed for the project
It was my duty in the project to assign the roles and responsibilities of every individual in
the project and for the successful accomplishment of the project I had to develop the following
objectives for the project:
 To lead the project and manage the efficiency and accuracy of the project
 To measure the air breakdown voltage
 To use standard sphere gap method in manner to determine the air breakdown
voltage
 To “discuss breakdown in gases a brief review of the fundamental principles of
kinetic theory of gases”
CE 2.2.3 My area of work
I had to apply my theoretical knowledge related to the breakdown mechanisms
and use the skills and knowledge for the determination of air breakdown voltage. I had been
taught about the two major types of this mechanism that includes Streamer theory and Townsend
theory and I had arranged the testing arrangements in the gaseous medium. I had developed the
following arrangements in the gaseous medium as explained in the figure below:

Figure 1: “Test arrangement for Townsend’s Discharge”
For this project, electrode configuration was the other important sector and I had
executed the experiment on both the arrangements of the sphere including the vertical and
horizontal alignment. Following figure explained the configuration of the horizontal and vertical
aligned sphere gap arrangement:
Figure 2: Sphere Gap Arrangements

CE 2.2.4 Project Group
CE 2.2.5 My responsibilities throughout the project
I was responsible for the team management and executing the activities of the team and
mine in and effective and efficient manner. I was also responsible for monitoring the growth of
the project and thus, ensure that the project is being executed as per the plan and manage the
circumstances those might have affect the calculated value. I was also responsible for the testing
arrangements and manage the whole setup where the whole team could execute the experiment
and determine the needed value. I had developed the following setup for the project:

Figure 4: Test Sphere Arrangement
CE 2.3 Distinctive Activity
CE 2.3.2 Engineering knowledge and skills applied in the project
I was also considering the environmental factors while executing the project that includes
room temperature and atmospheric pressure and considered these facts I the calculation of the air
break down voltage. I had established the following circuit be setup according to the established
setup and results were calculated on the basis of following circuit diagram:

Figure 5: “Schematic Circuit showing the source and Breakdown voltage measuring
unit using standard sphere gap method”
Dielectric strength was another concerning factor for the determination of the air
breakdown voltage and “the dielectric strength of a longer air gap is, in many cases, less than
proportional to air density.” I had used the following formula for the determination of air density
correction factor (K d):
K d = (P / Po) m X ({273 + to} / 273 + t) n
Where the parameters denote the following: p = “atmospheric pressure under test”, t =
“temperature (in degree centigrade) under test conditions.” I had also calculated the factor of
humidity correction for the efficient output of the project and used the formula:
K = [1 + (0.002 X (h / δ – 8.5))], where δ is the relative air density factor and h is the
humidity.
CE 2.3.3 Accomplishment and task performed
The project had many phases and many considerations had to be made while delivering
the project and it was important to consider the environmental factors in manner to manage the

accuracy of the data calculated. I had delivered the electrode configuration of the sphere gaps
considering the horizontal and vertical alignment of the spheres as stated in the above figure. Io
had made the calculations for the correction for air insulation where the constant factors were
calculated that lead to the accuracy in the calculation of the air breakdown voltage. I and my
team had calculated various results through these calculations and established the result and
average value was determined as the exact value of the experiment.
CE 2.3.4 Identified issues and their solutions
2.3.4.1 Issues
Determining the actual value was the primary concern for the overall project for which, I
had choose the laboratory where, the whole setup was made according to the arrangement. I had
identified that environmental factors including the pressure and temperature is capable of
affecting the value and hence, It will alternatively affect the whole project.
2.3.4.2 Solutions
I had selected the laboratory for the experiment and gaseous environment for the rings in
manner to manage the accuracy and efficiency of the calculated value of the air breakdown
voltage.
CE 2.3.5 Plan to produce creative and innovative work
We had executed the project considering the values determined through shifting the
spheres distance that helped in calculating the precise value of the voltage. I had determined that
the relative air density and maximum electric field factor characteristics have been derived
through executing the expiring in different pressure and temperature. I was successful in
identifying that “with increase of temperature the maximum electric field and relative air density

factor are decreased and with increase of pressure the maximum electric field and relative air
density factor are increased.”
CE 2.3.6 Collaborative work
The whole team performed as a whole and contributed in the successful deployment of
the project. I was leading the team towards the objectives and goal set before the execution if the
experiment and it was always my intention to keep them on the track. I had assigned every team
member individual role and tried to feel them as a part of the project. I was assigned to the
testing and experimental setup and other members were assigned to the calculation, recording,
wiring, power supply and other sectors. Every member of this project had contributed in the
determination of the breakdown Voltages considering the aspects related to the electrodes types
and had been measured in Point - Rod (square), Rod (Square) – Rod (Square), Point - Point, Rod
(circular) – Rod (circular), and Rod (circular) – Point.
CE 2.4 Project Review
CE 2.4.1 Project Overview
I had developed the project for the determination of the air breakdown voltage through
utilizing the sphere gap analysis and that has resulted in the positive manner. Various aspects
were made for the determination of the air breakdown voltage that includes the consideration of
the gap distances between the spheres and results were noted down in the table. Thereafter, I had
calculated the air break down voltage considering the distance between the point and the sphere
and data were calculated at various gap distances. After these two calculations we had calculated
the air break down voltage through considering the gap distances between the sphere and point
and relative data were calculated. After these calculations and recording, we had determined the

air break down voltage considering the ROD’s distances between the sphere and square and
related data were calculated through manipulating the gaps.
CE 2.4.2 My contribution to work
I had executed my knowledge and skills of the electrical engineering in manner to
determine the maximum resistance that an insulator can behold in high voltage and tried to
present an accurate value that could be used in the betterment in the electrical power field. I had
contributed in leading the team towards the successful accomplishment of the project. I had
executed the technical works that include the set up and arrangements of the experiment and
executed various experiments displacing the various distance aspects. I had executed the
activities listed in the above paragraph and calculated the respective values of the air breakdown
voltage. I had successfully determined the voltage at different aspects and various calculations
were performed that helped in the determination of the air breakdown voltage.