Showing papers on "Power-system protection published in 1977"

Predicting Damage from 277-V Single Phase to Ground Arcing Faults

Abstract: Laboratory tests of arcing faults trapped between a corner of a simulated steel housing and single or multiple bus bars were found to be reasonably reproducible and caused relatively consistent burning damage. Single phase 277-V arcing fault tests using spacings of 1 to 4 in from bus bars to ground at current levels of about 3000 to 26 000 A indicate that damage is proportional to I 1.5 t. In this ``ballpark'' arc voltage and arc length need not be known to predict probable maximum damage. For coordinated short circuit and ground fault protection, an arbitrary practical limit is proposed such that I 1.5 t is numerically not greater than 250 times the ampere rating of the circuit. Probable maximum burning damage in cubic inches of copper, aluminum, and steel is predicted based on the tests. The arbitrary limit is achievable with commercially available equipment using simple time current band coordination. Lower limits can be achieved using more sophisticated ground fault protection equipment.

Fast generator protection against internal asymmetrical faults

Abstract: An on-line digital computer technique for the protection of a generator against internal asymmetrical faults is described in this paper. The proposed technique relies on the detection of a second harmonic component in the field current at the onset of a fault in the armature winding. Discrimination against external faults is achieved by monitoring the direction of the negative sequence power flow at the machine terminals. Tests have been conducted on a laboratory synchronous generator for various types of internal and external faults. Results show that the total time for internal fault detection and tripping is well within half a cycle of the 60 Hz signal. A simple extension to negative sequence relaying and loss of excitation relaying is proposed.

Digital differential protection of a generating unit scheme and real-time test results

Abstract: This paper presents an on-line digital computer technique used for differential protection of a synchronous generator. It provides fault detection and tripping well within half a cycle and is also capable of discriminating between internal and external faults. In the latter case, sufficient restraint signals are generated to overcome maloperation. Further, the scheme is highly reliable even with CT saturation due to heavy through faults on the generating unit. On-line tests using a laboratory synchronous generator show the results for different types of internal and external faults with varying fault incidence inception.

Power System Protection And Switchgear

Abstract: Power system protection and switchgear , Power system protection and switchgear , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

Distance protection performance during simultaneous faults

Abstract: The paper considers the performance of both unswitched and switched distance protection schemes using polarised-mho relays on systems subjected to simultaneous faults. The disturbances considered are flashoverfaults to earth, cross-country earth faults and open-conductor plus earth faults on a double-circuit 132 kV transmission system. Consideration is also given to protection performance for double earth faults separatedby a star-delta transformer. Differences in protection philosophies of British and Continental relay manufacturers are highlighted and a comparison is given for switched schemes employing overcurrent starter units.

Electrical power systems. Volume 2

Abstract: This textbook is intended for university and technical students studying electrical power systems. Each chapter provides an introduction, definitions, and basic theory development. This volume contains information on power system protection; circuit interruption and switching overvoltages; stability of power systems; travelling waves in transmission lines; insulation coordination; rectification, inversion and high-voltage dc systems; 3-phase network matrices and coordinate system transformations; power system analysis; and aspects of system integration and development. Appendices on matrix algebra and the economics of electrical power generation are included. (LCL)

Parallel ac electrical system with differential protection immune to high current through faults

Abstract: In systems, such as aircraft electric power generation systems, three phase AC generators are often operated in parallel when supplying power to load busses and differential protection networks are utilized in each phase of each generator for detecting current imbalance between the phase conductor at the load and the neutral conductor of each phase. In this invention there is provided voltage limiter means such as back-to-back Zener diodes across each of the current transformers related to the phase and neutral conductors which, in conjunction with the other portions of the differential protection networks: (1) prevents nuisance tripping on the occurrence of high current faults outside the differential protection zone (such as bus faults) due to normal variations of the current transformers, and (2) at the same time, provides differential protection for a generator channel over the required range, generally from very low differential fault currents to the very high differential fault currents. The high differential fault currents will appear as high through current faults for the unfaulted parallel channels.

Duration of Hidden Faults in Randomly Checked Systems

Abstract: The pdf of the duration of hidden (non self-reporting) faults is derived. It depends on the pdf of item's life and the pdf of the distance between checks.

A Penetrating Gaze at One Open Phase: Analyzing the Polyphase Induction Motor Dilemma

Abstract: Portions of the material proposed for a chapter in a new IEEE Standard (#399-the ``Brown Book'') being prepared by the Power System Analysis Subcommittee of the I & CPS Committee are presented. In order to establish a library of approved analytical methods, the material provides a review of the more important basic electrical circuit analysis techniques used for determining the voltage and current relationships which describe various power system network events and operating conditions. Certain simplified circuit arrangements are examined. They illustrate the power and merit of the analytical methods that evolve, as well as the errors that can occur because of improper regard for the restraints that apply. Using the analytical methods, the classical problem of a three-phase induction motor operating with one phase of the supply line open-circuited is studied in considerable detail. Finally, important observations and conclusions are presented regarding the motor protection requirements.

Reactor Protection System Design Using Micro-Computers

Abstract: Reactor Protection Systems for Nuclear Power Plants have traditionally been built using analog hardware This hardware works quite well for single parameter trip functions; however, optimum protection against DNBR and KW/ft limits requires more complex trip functions than can easily be handled with analog hardware For this reason, Babcock & Wilcox has introduced a Reactor Protection System, called the RPS-II, that utilizes a micro-computer to handle the more complex trip functions This paper describes the design of the RPS-II and the operation of the micro-computer within the Reactor Protection System

Electrical power systems. Volume 1

Abstract: This textbook is intended for university and technical students studying electrical power systems. Each chapter provides an introduction, definitions, and basic theory development. This volume contains information on power transmission; transmission line inductance; transmission line capacitance; overhead lines; underground cables; transformers; synchronous machines in power systems; power system fault calculations; and power system protection. (LCL)

Ground-Fault Protection of Electrical Systems with Emergency or Standby Power

Abstract: Providing reliable ground-fault protection in electrical systems having alternate emergency or standby power can present serious problems unless adequate equipment is selected and properly coordinated. Multiple neutral-to-ground connections may prevent adequate sensing of ground-fault currents and may also cause nuisance tripping of circuit breakers. This paper discusses various approaches that have been proposed to solve these problems. Particular emphasis is placed on code requirements and overall reliability of the electrical systems.

Improving protection of unit-connected generators

Abstract: Existing methods of generator and transformer fault protection of large units are reviewed and shortcomings pointed to. Various methods are compared in a qualitative manner and improvements suggested. Included are combustion detectors for the indication of incipient faults, installed inside the tank of transformers with nitrogen cushion on top.

Laboratory Aid for Power System Protection Using Operational Amplifiers

Abstract: The equipment described contains several modules with variable input signals and auxiliary components together with a family of typical relay function cards. Provision is also made in the front panel for the design of standard or new types of relays using operational amplifiers. The unit is used for protection experiments and final year projects.