Line Charging Current Research Articles

Enhanced two-terminal impedance-based fault location using sequence values

<span lang="EN-US">Fault at transmission line system may lead to major impacts such as power quality problems and cascading failure in the grid system. Thus, it is very important to locate it fast so that suitable solution can be taken to ensure power system stability can be retained. The complexity of the transmission line however makes the fault point identification a challenging task. This paper proposes an enhanced fault detection and location method using positive and negative-sequence values of current and voltage, taken at both local and remote terminals. The fault detection is based on comparison between the total fault current with currents combination during the pre-fault time. While the fault location algorithm was developed using an impedance-based method and the estimated fault location was taken at two cycles after fault detection. Various fault types, fault resistances and fault locations have been tested in order to verify the performance of the proposed method. The developed algorithms have successfully detected all faults within high accuracy. Based on the obtained results, the estimated fault locations are not affected by fault resistance and line charging current. Furthermore, the proposed method able to detect fault location without the needs to know the fault type.</span>

Current differential protection of double-circuit transmission lines in modal domain

In this paper, we present a new approach to protection of double-circuit transmission lines using modal transformation. The current differential principle is applied in the modal domain, and the relay characteristics are plotted in the alpha plane for numerical differential protection applications. Synchronized voltages and currents from both the ends are transformed to modal values. The transmission lines are modeled as equivalent $$\pi $$ model in modal domain, and line charging current is compensated. Electromagnetic transient program EMTP-ATP is used to simulate the double-circuit transmission systems, and the algorithm is implemented in MATLAB. The extensive case studies demonstrate the utility and the superiority of the proposed current differential scheme.

Synchrophasor Based Novel Fault Location Algorithm for Three- Terminal Transmission Line

A fault detection and location algorithm on three-terminal transmission line is proposed. Vast literature on fault location shows that to simplify the analysis, line charging currents are often ignored. To improve the accuracy of fault location, synchronized current and voltage measurements from three ends of the three-terminal line are utilized to detect and locate distance to fault while considering the line charging currents. The method first detects the zone at which the fault has occurred and then locates it from the respective line ends. Since three-terminal lines provide solutions for connecting existing system to the grid, facilitating bulk transfer of power, thus the fault detection and location on the same is important to maintain reliability and security of the system. Performance of the proposed algorithm is tested for various fault types, fault locations, fault resistances and fault inception angles. The 200-kV system is simulated in ATP/EMTP; however, the algorithm is developed in MATLAB. The extensive simulation studies demonstrate accuracy of the proposed scheme.

A new microcomputer-based approach for pilot differential protection of transmission lines

This paper presents a theoretical and experimental study of a new technique for pilot differential protection of transmission lines. The difference currents obtained from post- and pre-fault line currents, adjusted by calculated charging currents, are used to minimize the desensitizing effect of load and line charging currents. The experimental results are from a laboratory 16-bit microcomputer-based relay that was developed to test some of the features of this new approach. Off-line test results for various types of faults on a lumped parameter long transmission line model and real-time test results for a short transmission line model are presented.

Simplified approach for estimating current unbalances in e.h.v. loop circuits

Electromagnetic and electrostatic unbalances due to the omission of transposition of transmission lines have been treated rather thoroughly, even though separately, in the literature. As e.h.v. lines become longer, and operating voltages are increased, it becomes evident that the line-charging currents are growing to the same order of magnitude as normal load currents. Consequently, it is often necessary to consider the effect of both line-charging and load currents in causing negative- and zero-sequence components of line current. When the total line is composed of sections with different cross-sectional configurations, the rigorous analysis becomes quite formidable. Therefore, a simplified equivalent circuit for an untransposed transmission-line section is proposed which relates more directly to familiar methods of circuit analysis. An important aspect of this method is that it brings out clearly the nature of the unbalance problem and thereby facilitates extrapolation, via good engineering judgement, to more complex networks.

Gas-blast switch tests on 230-kv system

Performance of a gas-blast switch on a 230-kv system of the U. S. Bureau of Reclamation near Hoover Dam is reported in this article. This switch has proved to be an economical means of interrupting transformer magnetizing current, parallel load current, and line charging current.

A 230-Kv 10,000-Megavolt-Ampere Steel-Clad Impulse Breaker - Another Rating in a Line of High-Capacity High-Voltage Breakers [includes discussion

This paper describes a further step in the development of a line of high-voltage high-capacity steel-clad impulse oil circuit breakers to fulfill the industry requirements for increased interrupting ratings at 138 kv, 161 kv, 230 kv, and 330 kv. The 230-kv 10,000-megavolt-ampere breaker introduced in this paper follows the design concepts formulated for the initial step and offers the same excellent operating characteristics associated with the impulse oil-blast principle of interruption. A new tank configuration results in an oil reduction of 40 per cent over the 230-kv conventional round tank breaker while doubling the short-circuit interrupting rating of that design. It further minimizes ground shock disturbance during the interruption of heavy-duty fault currents and allows overall tank heights to be reduced to such an extent that it is now possible to ship 230-kv breakers with all three poles factory-assembled and welded to a unit base. Complete electrical, interrupting, and mechanical design tests demonstrated that the breaker meets all industry standards with ample margins of safety. Tests at the Switchgear Development Laboratory included both fault duty interruptions and the switching of line charging currents. These tests have fully proved the adequacy of the design and indicate that higher interrupting ratings could be obtained, with modifications.

New high-voltage outdoor load-interrupter switch

This new completely self-contained switch interrupts line-charging currents, transformer-magnetizing currents, and load currents of transmission voltages. It is composed of a modern vertical-break air switch combined with a porcelain-clad gas-filled chamber. It is small, lightweight, easily operated, and economical.

A New High-Voltage Outdoor Load Interrupter Switch [includes discussion

This new completely self-contained switch interrupts line-charging currents, transformer-magnetizing currents, and load currents of transmission voltages. It is composed of a modern vertical-break air switch combined with a porcelain-clad gas-filled chamber. It is small, lightweight, easily operated, and economical.

New Design Oil Circuit Breakers for 7,500,000-Kva 230-Kv Service

As a logical step in the trend toward achieving a minimum oil content but still retaining the advantages of the time-proved dead-tank construction a new 230- kv circuit breaker built around a novel design of tank has been developed. The extra volume of oil which contributes nothing to the insulation nor to the efficiency of the circuit breaker in interrupting performance has been eliminated and the required amount of oil reduced to the point where simplified methods of oil handling and maintenance procedures are possible. Design tests on the circuit breaker prove its adequacy in meeting design standards and extensive High Power Laboratory tests reveal a superior performance in interrupting fault and line-charging currents. The quantity of oil used and the design of the contacts is such as to permit a number of fault interruptions without maintenance operation.

The application of phase-comparison principles to power-swing conditions on long high-voltage transmission lines

The paper concerns the protection of long high-voltage transmission lines on which the power-swing conditions are complicated by appreciable line-charging currents. Phase-comparison protection only is considered, depending on the difference in phase between the line currents at the two ends of the line. The problem involved is the study of the power-swing conditions and the setting of them on a phase-comparison diagram on which the protection relay characteristic is already drawn.The application of phase-comparison principles is here developed to a stage which suggests their wider use than at present, and limitations are defined in terms of line constants, including line length and voltage.The diagrams obtained show conclusively which load and power-swing conditions appear in the “trip” section of the phase-comparison field, and a simple envelope is derived mathematically and drawn to include all load and power-swing characteristics of the line. It is shown that the relay settings are determined by the no-load and light-load conditions, and not by the power-swing conditions, which are a problem of impedance protection relays. Although complicated to construct, power-swing curves are already available on the impedance diagram 1. The provision of an easily constructed phase-comparison power-swing diagram should assist in applying phase-comparison protection to long lines.

High-Voltage Oil Circuit Breakers for 5,000,000- to 10,100,000-Kva Interrupting Capacity

The paper describes some of the special design features for steel-tank oil circuit breakers rated 5,000,000 kva at 138 kv, 161 kv, and 230 kv, and rated 7,500,000 or 10,000,000 kva at 230 kv. The method of verifying these interrupting capacities both in the manufacturers' high-power laboratory and by field tests on a customer's property is outlined, with special consideration given to the problems of switching line-charging currents and of interrupting high power repeatedly, under both standard duty and rapid reclosing duty cycles.

Performance Test of the Allgemeine Elektricitats Gesellschaft Free-Jet Air-Blast 220-Kv 2,500-Megavolt-Ampere Reclosing Circuit Breaker

Tests of a representative sample of this circuit breaker were made on the system of the Bonneville Power Administration in order to provide an opportunity for American manufacturers and operating engineers to study the operation of this circuit breaker in interrupting faults and line charging currents. A single pair of interrupting contacts in open air, ease of contacts visual inspection, maintenance and replacement attracted much attention and favorable comment, particularly from operating engineers. The circuit breaker successfully interrupted fault currents in about six cycles (average) as compared with three cycles of fast oil circuit breakers of American manufacture. Interruption of line charging current, although successful, was accompanied by many restrikes. It is hoped that these tests and the analysis of the test data will facilitate development of an American circuit breaker which will retain the favored features of the European prototype but will be faster in interrupting fault currents and practically free from restrikes in interrupting line charging currents.

Corona Tests at High Altitude

This paper describes some corona tests which were made in Peru on a 70-mile transmission line located at an average altitude of 13,300 feet. The voltages range from 40,000 to about 72,000. The method employed in the tests is described and the calculations are given. The corona losses were found by subtracting the core and copper losses of the transformers and the line copper losses due to the line charging currents from the total loss measured. Core-loss tests were made on the transformers in order to check these against the shop tests. The highest voltage experimented with was 72,300 when a corona loss of 153 kw. was found, or a little over two kw. per mile of line. The results are compared to ``Peek's law'' and a wide divergence found, amounting to over 800 per cent at about 66,000 volts and a loss of 58 kw. Close correspondence is found between these tests and those made by Faccioli on the Shoshone-Leadville line, and the equation of the loss-voltage curve obtained is the same as was established by Faccioli, and shows this relation to be logarithmic and not quadratic for the voltage range investigated. It is shown that the results are in good agreement with the formulas deduced by Professor Ryan from extensive laboratory tests. Finally test data are given for a test made during rainy weather and this shows no appreciable difference from tests made during fair weather.

Corona tests at high altitude

This paper describes some corona tests which were made in Peru on a 70-mile transmission line located at an average altitude of 13,500 feet. The voltages range from 40,000 to about 72,000. The method employed in the tests is described and the calculations are given. The corona losses were found by subtracting the core and copper losses of the transformers and the line copper losses due to the line charging currents from the total loss measured. Core-loss tests were made on the transformers in order to check these against the shop tests. The highest voltage experimented with was 72,300 when a corona loss of 153 kw. was found, or a little over two kw. per mile of line. The results are compared to “Peek's law” and a wide divergence found, amounting to over 800 per cent at about 66,000 volts and a loss of 58 kw. Close correspondence is found between these tests and those made by Faccioli on the Shoshone-Leadville line, and the equation of the loss-voltage curve obtained is the same as was established by Faccioli, and shows this relation to be logarithmic and not quadratic for the voltage range investigated. It is shown that the results are in good agreement with the formulas deduced by Professor Ryan from extensive laboratory tests. Finally test data are given for a test made during rainy weather and this shows no appreciable difference from tests made during fair weather.