This book deals with fault location on transmission lines. Among many fault location methods, the impedance-based method has been taken for detailed considerations. In this method, the impedance parameters of the faulted line section are considered as a measure of the distance to fault. The impedance-based fault location appears to be still the most popular method. This is so, since impedance-based fault location algorithms exhibit various advantages and can be easily implemented into the products offered by the numerous manufacturers. The book begins (Chapter 1) with explaining the aim of fault location and its importance. In particular, the fault locators are considered as the devices that differ in many aspects from protective relays. Then, different fault location methods are shortly characterised.
In Chapter 2, the basics of the impedance-based fault location are presented. Division of fault location algorithms with respect to the fault locator input signals is performed and time intervals of fault locator input signals are defined. Then, signal processing methods for fault location are shortly reviewed. In relation to use of distributed digital measurements to fault location, their synchronisation with the aid of the GPS or by analytical synchronisation is described. The fault location error is defined and the sources of errors are characterised.
Chapter 3 reviews different configurations of the networks. The networks containing single-circuit lines, double-circuit lines, multi-terminal and tapped lines, composition of overhead line and cable, and series-compensated lines are presented. Then, the lumped-parameter and distributed-parameter line models are presented. The modal transformations are gathered.
In Chapter 4, the basics of transmission line faults are provided. The fault models are formulated using symmetrical components and phase co-ordinates approach. The analysis of arcing faults, including typical waveforms of current and voltage signals, obtained from the ATP-EMTP simulation, is presented.
Chapter 5 is focused on the measurement chains of fault locators. Transient performance of capacitive voltage transformers and their dynamic compensation are considered. The basics for current transformers are given. It has been shown how to counteract the negative effects of the possible saturation of current transformers, when
deriving fault location algorithms. The design of analogue low-pass filters is addressed.
In Chapter 6, a variety of one-end impedance-based fault location algorithms are presented. To this end, a uniform description of the faults and the fault loops has been applied. The algorithms presented are designed for locating faults on single-circuit lines, double-circuit lines and series-compensated lines. Both transposed and untransposed lines are taken into consideration. The algorithms are formulated for the lumped line models, however, at the end of the chapter, the way of improving fault location accuracy by introducing the distributed-parameter line model is presented.
Chapter 7 is focused on two-end and multi-end fault location algorithms. First, the algorithms utilising two-end synchronised measurements are presented for both phasor-based and time domain approaches. Then, the unsynchronised measurements as applied to fault location are considered in detail. Different options for measuring the synchronisation angle are introduced and various fault location algorithms are presented. Complete and incomplete two-end measurements are taken into account. Algorithms utilising measurements of distance relays from line terminals are described. Fault location on three-terminal and multi-terminal lines is addressed. The author presents fault location algorithms developed by himself or in cooperation, as well as algorithms selected from the vast literature of the subject. When presenting fault location on series-compensated lines, the considerations are intentionally limited to the basic network configuration with a single-circuit line and to using the one-end measurements. The other fault location algorithms can be found in the literature.
Fault location on power transmission lines is a critical aspect of power system protection and maintenance. It involves identifying the exact point of a fault along a transmission line to enable timely repairs, minimize downtime, and improve the reliability of power delivery. Accurate fault location is essential for efficient system operation, reducing repair costs, and ensuring the safety of maintenance personnel.
Types of Faults on Transmission Lines
Faults in power transmission lines can be classified into several categories:
- Symmetrical Faults (Three-phase faults): These involve all three phases equally and are rare but severe.
- Asymmetrical Faults:
- Single-line-to-ground faults (most common)
- Line-to-line faults
- Double-line-to-ground faults
Techniques for Fault Location
Fault location techniques are broadly categorized based on the type and amount of data they require. Common methods include:
1. Impedance-Based Methods
These are the most widely used methods in the industry:
- Utilize voltage and current measurements to calculate the impedance to the fault.
- Relatively simple and rely on fundamental frequency components.
- Accuracy may be affected by factors like line impedance variations, fault resistance, and mutual coupling in double-circuit lines.
2. Travelling Wave Methods
- Use high-frequency electromagnetic waves generated by faults to pinpoint their location.
- Highly accurate as the wave travel time directly correlates with distance.
- Require high-speed measurement equipment and are more suitable for long transmission lines.
3. Time-Domain Reflectometry (TDR)
- Send a test signal down the line and measure the time taken for the reflected signal to return from the fault point.
- Common in cable fault location but less so in overhead lines due to signal attenuation.
4. Artificial Intelligence-Based Techniques
- Leverage AI algorithms like machine learning or neural networks for fault detection and location.
- Require a large amount of training data but can handle complex fault conditions effectively.
5. Phasor Measurement Unit (PMU) Based Methods
- Use synchronized measurements from PMUs installed at different locations.
- Provide high accuracy and are particularly effective in modern smart grids.
Factors Influencing Fault Location Accuracy
- Line Length: Longer lines introduce more uncertainty due to factors like signal attenuation.
- Fault Resistance: High resistance faults, such as arcing faults, can skew measurements.
- System Configuration: Double-circuit and multi-terminal lines complicate fault location.
- Communication Latency: Real-time fault location depends on the timely exchange of data from sensors and relays.
Benefits of Fault Location
- Reduced Downtime: Quick identification of fault locations enables faster restoration of service.
- Cost Efficiency: Minimizes the resources and time spent on manual inspection.
- Enhanced Reliability: Improves the overall reliability and resilience of the power grid.
- Safety: Reduces the risk to maintenance personnel by pinpointing faults precisely.
Applications in Modern Grids
With the advent of smart grids and advanced monitoring systems, fault location techniques have become more sophisticated. Integration with SCADA systems and the use of IoT devices for real-time monitoring ensure rapid fault detection and response. These advancements are paving the way for automated and self-healing grids.
In summary, fault location on transmission lines is a vital component of power system operations, blending traditional methods with modern technology to enhance grid efficiency and reliability.
Reference/Source
Download
👇👇👇👇
Fault location on power transmission lines (PDF COPY)