Generator Circuit Breaker Research Articles

Voltage Escalation and Reignition Behavior of Vacuum Generator Circuit Breakers During Load Shedding

Voltage Escalation and Reignition Behavior of Vacuum Generator Circuit Breakers During Load Shedding

Prevention of tank rupture of faulted power transformers by generator circuit breakers

AbstractInternal fault arcs in power step‐up transformers occasionally occur at different locations inside the tank. In this study it has been investigated to what extent generator circuit breakers (GCB) between generator and transformer may prevent explosion or severe damage due to pressure rise caused by the fault arc. Using sources from literature, study of fault cases that occurred in the past, and research of arc‐current and arc‐voltage conditions, a procedure was established to check the probability to what extent a GCB may reduce severe transformer damage and increase safety by prevention of fire. Following this procedure some actual fault‐case studies show that GCB are effective in saving the transformer tank with a probability up to more than 80 %. Comparison with failure data verify the calculations.

Insulation co-ordination aspects for power stations with generator circuit-breakers

The generator circuit-breaker (gen.c.b.) located between the generator and the step-up transformer, is now being applied world-wide. It has become a recognized electrical component of power stations which is largely due to economical advantages and increased power station availability. Technical protection considerations for power stations have always been the reason for discussion and the object of improvement. With the use of a gen.c.b., some points of view need to be considered anew. Not only the protection system in case of fault conditions will be influenced, but also the insulation co-ordination philosophy. The results of some calculations concerning expected overvoltages are presented. These calculations are based on a transformer rated 264/15.5 kV, 220 MVA, but the results are transferable to other power plants. Some measurements carried out on a transformer of the same rating complement the calculations. The findings may contribute to an improvement in insulation co-ordination and protection of the electrical system generator/step-up transformer. >

A new IEEE/ANSI standard for generator circuit breakers

A new IEEE/ANSI standard for generator circuit breakers applied between generator and step-up transformer has been developed by an IEEE Working Group. This was necessary since the requirements for such breakers deviate in many respects from those of general purpose circuit breakers. This paper highlights special aspects of generator circuit breaker application and describes major differences to the standards C37.04, -06 and -09 for transmission and distribution circuit breakers.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Synthetic Testing Method for Generator Circuit Breakers

Today, generator circuit breakers are air-blast circuit breakers, mainly to cope with the non zero passage current requirements. Their breaking capacity is extremely high (275 kA/24 kV). The testing station power is not always great enough to perform a complete testing through a direct circuit. The low ohmic value parallel resistor in those breakers makes it difficult to perform the synthetic tests. The authors bring forward a rather simple circuit arrangement to test at one time the breaking capacity of the main chamber. They wish to demonstrate the effectiveness of the testing method with an arc model.

Short Circuit Testing Methods for Generator Circuit Breakers with a Parallel Resistor

ANSI-Standard C37.09-1979 describes design and testing of AC high voltage circuit-breakers under fault conditions. For synthetic test methods application guide ANSI/IEEE C37.081-1981 is added. Presently, generator circuit-breakers of the airblast type are built with a low ohmic parallel damping resistor. At this time there are no standards establishing test circuits or test procedures for this type of circuit-breaker. This article outlines the problems involved in testing generator circuit-breakers equipped with parallel resistors and gives a qualitative analysis of several test circuits.

Short-Circuit Testing Methods for Generator Circuit-Breakers with a Parallel Resistor

Short-Circuit Testing Methods for Generator Circuit-Breakers with a Parallel Resistor

Synthetic Testing of Circuit Breakers Equipped With a Low Ohmic Parallel Resistor (With Special Respect to Generator Circuit Breakers)

The application of classical synthetic testing methods to powerfull generator circuit breakers (GCB's) which are equipped with alow ohmic parallel resistor is strongly limited since an extremly high energy supply by the circuit's source capacitor bank is required. This capacitor bank has to be of a size usually not available in ahigh power testing station.

Synthetic Testing of Circuit Breakers Equipped With a Low OHMIC Resistor with Special Respect to Generator Circuit Breakers

Synthetic Testing of Circuit Breakers Equipped With a Low OHMIC Resistor with Special Respect to Generator Circuit Breakers

Investigation of Inherent Transient Recovery Voltage for Generator Circuit Breakers

The transient recovery voltage (TRV) for generator circuit breakers is investigated. The TRV for fault currents from the generator as well as from the system through the generator step-up transformers is calculated: A generalized expression for the TRV is developed and dimensionless plots made. Test results on two generating units are presented, showing good agreement with calculated values. A basis of rating for generator breaker TRV is also presented. TRV waveshapes and TRV parameters are suggested as part of the basis of rating.

Investigation of Inherent Transient Recovery Voltage for Generator Circuit Breakers

The transient recovery voltage (TRV) for generator circuit breakers is investigated. The TRV for fault currents from the generator as well as from the system through the generator step-up transformers is calculated. A generalized expression for the TRV is developed and dimensionless plots made. Test results on two generating units are presented, showing good agreement with calculated values. A basis of rating for generator breaker TRV is also presented. TRV waveshapes and TRV parameters are suggested as part of the basis of rating.

Three Phase Dynamic Simulation of Air Blast Generator Circuit Breakers -- Theory and Modeling

Simulations of three-phase faults at the generator terminals have shown the existence of non-zero currents in all three phases for several cycles. Particularly in the application of generator circuit breakers, there could be a serious problem in that the delayed current-zero phenomenon might inhibit normal circuit opening. This investigation was undertaken to develop a method of modeling the circuit breaker arcing characteristics and determine the influence of arc gap resistance on the normal fault current decay. The paper presents the fundamental theory of the non-zero current phenomenon along with the basic operation and modeling of typical air-blast circuit breakers.

Technico-Economical Response of the Generator Circuit Breaker to Future Generation Ratings

The increase of power units of generators and main transformers, and of short- circuit-carrying capability of transmission networks, compel the interrupting switchgear manufacturers to improve continuously the performances of the equipment in order to make best use of the new techniques through properly adapted testing facilities and methods. The problem raised by high nominal currents has been examined and solutLons proposed for extra- high short-circuit currents beyond 300 kA.

Some Design Aspects of Generator Circuit-Breakers for Rated Currents up to 50 000 A

Rated currents above the self-cooled values up to 50 kA demand forced cooling. In this connection the following aspects are explained:-Normal operating conditions and the effects of temperature changes of the various coolants to the load current carrying capability.-Abnormal operating conditions caused by failures of the cooling systems.

Simulation of a synchronous generator connected via a delta—star transformer

A mathematical model of a 3-phase synchronous machine, connected to the infinite bus through a delta?star transformer and a transmission line, is given. Symmetric and asymmetric faults on the low-voltage side and on the high-voltage side of the transformer are analysed by using 3-phase variables. Since the simulation is in terms of the direct-phase quantities, the digital-program solution can very easily simulate simultaneous fault conditions as well as sequential faults on either side of the power transformer. By applying proper constraint conditions, the model can be readily used to include symmetric and asymmetric faults for an unloaded alternator, and power-frequency transients following the closure of the generator circuit breaker. The validity of the analysis developed is examined by comparing the digital results with the theoretical results for 3-phase faults on a generator on open circuit, and with a number of experimental results. Versatility is demonstrated by the range of experimental results considered and by further studies.

Electrical Features of Raccoon Mountain Pumped-Storage Plant

This paper describes unique features of the electrical equipment and some of the considerations involved in its selection for a 1,700-MVA underground pumped-storage project with four reversible pump/turbines. Considerations of cost and maintenance of the machines, transmission system, and powerhouse construction led to selection of generator/motors with direct water-cooled stator and rotor windings, static-converter synchronous starting of pumps with synchronous dynamic braking, use of generator circuit breakers, and underground main transformers with self-contained 161-kV single-section cables having 1,100-ft change in elevation.

A Half Cycle Air Blast Generator Breaker for High Power Testing Fields

Generator breakers in high-power testing fields, the back-up breakers, have the function of safety breakers: they have to protect both the generator and the test breaker from being overstressed by a short-circuit current of undesired duration. The heavy short-circuit currents of modern generators enforce the development of generator circuit-breakers of high breaking capacities. In this paper a generator c. b. is described having a rated breaking capacity of 160 kA at a service voltage of 15.4 kV. This circuit-breaker is a half-cycle breaker capable of interrupting a symmetrical current at the first current zero passage. Due to its short minimum arcing time this breaker is suitable for syn- chronized breaking operations and so permits an economical testing of circuit-breakers. This testing method is also described.

Static control and protection of aircraft electric power systems

THE generation end of a conventional aircraft electric-power system consists of several basic units. These are the generator, voltage regulator, generator circuit breaker, and the control and protection panel. The basic functions of the control and protection panel are those of opening and closing the field of the generator, and supervising the opening and closing of the generator circuit breaker. In a parallel-generator system, supervising the opening and closing of the bus tie circuit breaker is another basic function. In order that these control functions be performed in a logical manner, a control and protection panel must sense voltages and currents throughout the electric system. These various voltages and currents are measured, compared with standards, time-delayed if necessary, mixed with each other in logic circuits, amplified, and finally used to perform the necessary control functions. The panel protective functions include such circuits as overvoltage protection, undervoltage protection, overexcitation protection, underexcitation protection, underspeed protection, stability protection, and differential current protection. The panel control functions include lockout circuits to prevent cycling of circuit breakers, and a circuit for automatic paralleling of generators.