This study is focused on installations and faults diagnosis of high voltage underground cables and examined on the various ways through which they can be identified and corrected. It has been found that wear and tear is one of the major issues leading to electric faults like power loss. There has been seen that several causes of failure which could be identified with them and analyze better ways of detecting them. So, it has been looked at how to detect degradation of insulation of the underground cable. After a thorough analysis of fault detection techniques have been explained, the pre-location fault techniques is described; I illustrated many methods which aid to discover the fault location. I also developed a method which contributes in pre-location of the fault based on Matlab simulation and mathematical slope equation. This method was invented after the observation that the voltages measured at the local and remote substations, after filtering and after Fourier analysis, showed a linear behavior that was proportional to the respective distances between the fault location and the mentioned substations or generators. Thus, the developed method exploits such a linearity to estimate the fault location by interpolation, assuming that the parameters of the line are previously known and that dedicated devices are located on site in both substations to provide post-fault measurements of the faulted line. Finally, I clarify many pin-pointing methods to precisely determine the fault location.
Table of Contents
1.Introduction
1.1 Thesis Objectives
2. LITERATURE REVIEW
3. Differences between Underground Electrical Cables and Overhead Electrical Cables
4. Insulation and Methods of Protection of High Underground Cables
4.1 Phase Comparison Scheme
4.2 Directional Comparison Scheme
5. Economic Aspects of High Underground Cables
6. Technical Aspects of High Voltage Underground Cables
7. Common High Voltage Underground Cables Faults
8. Detection of High Underground Cables Faults
9. Analysis of High Underground Cables Faults pre-locating Methods
9.1 Cable Route tracers
9.2 Selecting a Tracer
9.3 Time Domain Reflectometry (TDR) Tests
9.4 DC Hi-potential Test
9.5 Cable pre-location
9.5.1 Sectionalizing
9.5.2 Electromagnetic Surge Detection
9.5.3 Arc Reflection
9.6 Pinpointing the fault
9.6.1: Acoustic Detection:
9.6.2 Electromagnetic Impulse Detector
9.6.3 Voltage Gradient Test
10. Solution and method to fix faults on High underground Cables faults
11. Discussions of High Underground Cables Recovery Solutions
11.1 Cable smoldering
11.2 Cable chopping
11.3 Cable Stripping
11.4 High-Temperature Incineration
12. Modeling & Simulation of High Voltage Underground Cable
12.1 Model Explanation
12.2 Measurment of Voltage modelling for different fault locations
13. Installing & Testing of High Voltage Underground Cable in Ras Tanura
13.1 Underground High Voltage Cable Constructions & Ratings
13.2 Important Standard & Specifications
13.3 High Voltage Underground Cable Installation
13.3.1 Materials and Equipment
13.3.2 Manpower Organizations
13.3.3. Quality Control
13.3.4. High Voltage Cable Installation Procedure
13.4 69 KV High Voltage Underground Cable Simulation & Testing
13.4.1 Simulation for Fault Points for 69 Kv Underground Cable
13.4.2 Calculation for pre-location faults
14. Conclusion
Objectives and Key Themes
This thesis focuses on the diagnosis and localization of faults in high-voltage underground cables, aiming to develop efficient detection and recovery methods. The primary research objective is to create a reliable fault location estimation method using Matlab simulation, which identifies fault positions based on voltage measurements at substations, ultimately facilitating faster repairs and minimizing power outages.
- Comparison between underground and overhead electrical cable systems.
- Investigation of insulation and protective schemes for underground cables.
- Technical and economic analysis of high-voltage underground cable installations.
- Development of a Matlab-based simulation method for fault location estimation.
- Exploration of effective cable recovery and environmental waste management techniques.
Excerpt from the Book
12.1 Model Explanation
Figure 12.1 shows the modelling scheme of high voltage underground cable rated 132 Kv.
Figure 12.1 depicts the whole modelled system including the following elements: generators, transmission lines (underground cables), breaker (to simulate fault to ground) and respective meters to capture and plot the results.
The parameters for every element can be defined per separate by double clicking upon every component block in the model. Figure 12.2 shows the main toolbar that uses Simulink to execute the main actions over a model. The value 0.5 indicates the time of simulation. In this case 0.5 seconds is chosen since the simulated fault occurs at instant 0.25 seconds, and thus, it is enough interval to obtain the needed measurements.
Figure 12.3 shows the block element that models a distributed parameter line in Simulink. All the parameters characterizing the simulated line are inserted in the form that opens on double-clicking over this block: length, positive and zero sequence resistances, positive and zero sequence inductances and capacitance of underground cable, among others. According to Figure 14, the model involves two distributed parameter lines, one representing the portion of cable between the local generator and the fault location (left), and the other one representing the portion of cable between the fault location and the remote generator (right). Thus, the parameter length for each of this portions, must be introduced independently for every simulation case in which the fault location is at different positions. It will be accomplished then that the sum of the lengths of the left portion of line and the right portion of line is always equal to the total length of the line L.
Summary of Chapters
1. Introduction: Discusses the growing demand for power and the operational necessity of underground cables, outlining the study's goal to diagnose faults and propose effective location techniques.
2. LITERATURE REVIEW: Examines current methodologies for classifying and detecting underground cable faults, including software-based, AI, and traveling wave techniques.
3. Differences between Underground Electrical Cables and Overhead Electrical Cables: Highlights the structural and environmental differences, comparing the reliability and maintenance challenges of both systems.
4. Insulation and Methods of Protection of High Underground Cables: Analyzes various protection relay schemes like phase comparison and current differential to mitigate damage from overheating and system faults.
5. Economic Aspects of High Underground Cables: Evaluates the lifecycle costs of underground cables, focusing on procurement, installation, and long-term maintenance implications.
6. Technical Aspects of High Voltage Underground Cables: Investigates the complex technical factors, such as heat dissipation and voltage-dependent losses, that influence high-voltage underground operations.
7. Common High Voltage Underground Cables Faults: Categorizes prevalent fault types like open-circuit, short-circuit, and earth faults, and discusses diagnostic tools like the megger.
8. Detection of High Underground Cables Faults: Describes practical detection techniques ranging from behavioral monitoring to specialized devices like Magnetic CN Probing.
9. Analysis of High Underground Cables Faults pre-locating Methods: Details advanced pre-location techniques including TDR, DC high-potential tests, and electromagnetic surge detection.
10. Solution and method to fix faults on High underground Cables faults: Outlines practical repair procedures, emphasizing re-termination and rigorous testing post-repair.
11. Discussions of High Underground Cables Recovery Solutions: Reviews environmental recovery methods, critiquing traditional smoldering and promoting sustainable alternatives like cable chopping and stripping.
12. Modeling & Simulation of High Voltage Underground Cable: Explains the development of a Matlab/Simulink model to estimate fault locations based on the linearity of voltage behavior at substations.
13. Installing & Testing of High Voltage Underground Cable in Ras Tanura: Provides a comprehensive case study on installation standards, duct bank construction, and testing protocols for a 69 kV project.
14. Conclusion: Summarizes the thesis findings, confirming the effectiveness of the proposed interpolation-based estimation method and the importance of professional cable recovery practices.
Keywords
High Voltage, Underground Cable, Fault Detection, Cable Failure, Pre-location, Matlab Simulation, Pin-pointing, Power Distribution, Insulation, Protection Schemes, Cable Recovery, Cable Chopping, Splicing, Reliability, Substation
Frequently Asked Questions
What is the primary focus of this thesis?
The thesis focuses on the diagnostics, location, and repair of faults in high-voltage underground electrical cables, providing both theoretical analysis and practical installation guidelines.
What are the main thematic areas addressed in this work?
The work covers cable protection schemes, economic and technical installation aspects, various fault detection technologies, and simulation-based methods for fault pre-location.
What is the central research goal or problem?
The central goal is to improve the efficiency of fault diagnosis and localization in underground cables to reduce power restoration time and minimize repair expenses.
Which scientific methods are employed?
The author uses empirical literature review, comparative analysis of electrical infrastructures, and Matlab/Simulink software to model fault behavior and validate a linear interpolation method for fault location.
What is covered in the main body of the work?
The main body spans from fundamental differences between cable types to specific diagnostic techniques (TDR, arc reflection), detailed installation procedures for duct banks, and simulation results for 132 kV and 69 kV systems.
Which keywords define this work?
Key terms include High Voltage, Underground Cable, Fault Detection, Matlab Simulation, Pre-location, Pin-pointing, Insulation, and Cable Recovery.
How does the proposed interpolation method work for fault location?
It exploits the observation that post-fault voltages at substations A and B exhibit a linear relationship relative to the fault's distance, allowing for estimation by averaging the location calculations derived from both ends.
What specific case study is provided?
The thesis includes a detailed case study of a 69 kV high-voltage underground cable installation project in Ras Tanura, Saudi Arabia, covering everything from construction to final testing.
What are the environmental recommendations in this thesis?
The author strongly recommends abandoning the environmentally harmful practice of cable smoldering in favor of sustainable recovery methods like mechanical cable chopping and stripping to reclaim copper and insulation materials.
How are the simulated faults categorized in the Matlab model?
The simulations focus primarily on "single line to ground" faults, which account for approximately 75% of total transmission line faults, to test the accuracy of the proposed estimation algorithm.
- Citation du texte
- Hussain Mahdi (Auteur), 2015, Analysis techniques of diagnosis high voltage underground cables, Munich, GRIN Verlag, https://www.grin.com/document/337222
