Magnetic Circuit Breakers Research Articles

Superconducting Magnetic Energy Storage-Based DC Circuit Breaker for HVDC Applications

Superconducting Magnetic Energy Storage-Based DC Circuit Breaker for HVDC Applications

Probability-Based Customizable Modeling and Simulation of Protective Devices in Power Distribution Systems

Fused contactors and thermal magnetic circuit breakers are commonly applied protective devices in power distribution systems to protect the circuits when short-circuit faults occur. A power distribution system may contain various makes and models of protective devices, as a result, customizable simulation models for protective devices are demanded to effectively conduct system-level reliable analyses. To build the models, thermal energy-based data analysis methodologies are first applied to the protective devices’ physical properties, based on the manufacturer’s time/current data sheet. The models are further enhanced by integrating probability tools to simulate uncertainties in real-world application facts, for example, fortuity, variance, and failure rate. The customizable models are expected to aid the system-level reliability analysis, especially for the microgrid power systems.

Forecasting technical state and efficiency of electrical switching devices at electric complexes in oil and gas industry

This work is topical, since it allows predicting the physical state of the contact joints of low-voltage switching devices and to avoid their destruction, which occurs due to mechanical and chemical effects on the contacts during operation, leading to an increase in the transition resistance and overheating of the contacts. The following criteria were adopted as serviceability criteria for the contact connections of switching devices: the maximum temperature of their heating, the maximum value of the resistance of the pole of the device and its parts, as well as the excess of the temperature of the contact heated part over the ambient temperature. The authors obtained graphs of the dependence of the resistance value of the contact connections of magnetic starters and circuit breakers on the ambient temperature and load factor. The article determines the analytical dependence of the resistance of the magnetic starter contact connections on the ambient temperature. It also features mathematical models that take into account various operating conditions of switching devices, the input values of which are refined using regression analysis.

Investigating Phase Over-Current (OC) Protection in Medium-Voltage networks

Overcurrent protection is protection against excessive currents or current beyond the acceptable current rating of equipment. It generally operates instantly. Short circuit is a type of overcurrent. Magnetic circuit breakers, fuses and overcurrent relays are commonly used to provide overcurrent protection. There is always a need to protect expensive power equipment. Protective relaying is a very important part of any electric power system that comes into play during trouble, fault or abnormal condition. The purpose is to isolate unhealthy part of electrical power system while the rest continue their normal operation. The entire electric power system from source to load centers is exposed and subject to natural hazards. The effects of these hazards are capable of interrupting normal operations of the system. Since these hazards cannot be prevented, precautions are taken to minimize or eliminate their effect on the system. The relay is a basic component of any protection scheme. The information (or signals) received from the power system actuates the relay, when necessary, to perform one or more switching actions. The signals are proportional to the magnitudes and phase angles of power system voltages and currents. When the relay receives these signals, it decides to close (or open) one or more sets of normally open (or closed) contacts, and consequently, the trip coil of a circuit breaker will be energized to open the power circuit. This paper investigates over-current relay protection scheme applied to medium-voltage electrical network. Methods of current and time grading have been applied in the coordination of the overcurrent relays in a radial network. Different time/current characteristics of relays such as the normal inverse (NI), very inverse (VI), and extreme inverse (EI) have been examined in order to obtain optimum discrimination.

Investigating Phase Over-Current (OC) Protection in Medium-Voltage networks

Overcurrent protection is protection against excessive currents or current beyond the acceptable current rating of equipment. It generally operates instantly. Short circuit is a type of overcurrent. Magnetic circuit breakers, fuses and overcurrent relays are commonly used to provide overcurrent protection. There is always a need to protect expensive power equipment. Protective relaying is a very important part of any electric power system that comes into play during trouble, fault or abnormal condition. The purpose is to isolate unhealthy part of electrical power system while the rest continue their normal operation. The entire electric power system from source to load centers is exposed and subject to natural hazards. The effects of these hazards are capable of interrupting normal operations of the system. Since these hazards cannot be prevented, precautions are taken to minimize or eliminate their effect on the system. The relay is a basic component of any protection scheme. The information (or signals) received from the power system actuates the relay, when necessary, to perform one or more switching actions. The signals are proportional to the magnitudes and phase angles of power system voltages and currents. When the relay receives these signals, it decides to close (or open) one or more sets of normally open (or closed) contacts, and consequently, the trip coil of a circuit breaker will be energized to open the power circuit. This paper investigates over-current relay protection scheme applied to medium-voltage electrical network. Methods of current and time grading have been applied in the coordination of the overcurrent relays in a radial network. Different time/current characteristics of relays such as the normal inverse (NI), very inverse (VI), and extreme inverse (EI) have been examined in order to obtain optimum discrimination.

A hybrid circuit breaker based on current commutation approach for multi feeders DC railway substations

The paper presents an economic hybrid circuit breaker for limiting and interrupting the faults in DC railways substations. For fast fault current interruption, the hybrid breaker incorporates high speed mechanical contacts actuated by power semiconductor devices. Additionally, to avoid formation of electric arc, a commutation circuit is used to inject a counter current during fault interruption. In a real railway substation, each feeder is connected to the main DC bus through an expensive air magnetic DC circuit breaker and to an auxiliary DC bus through another expensive breaker. This leads to high cost especially in railway substation with multi feeders which are used to energize the vehicle transmission lines. In this paper, all DC breakers in DC railway substations are replaced by the suggested circuit breaker, which consists of a high speed mechanical contact with two semiconductor devices in each feeder and only one commutation circuit for injecting the counter current in all faulted feeders. The fault diagnosis is designed to detect the abnormal condition (current or voltage) in all feeders and direct the injected current from the commutation circuit to the faulted feeder only when the abnormal reaches a predetermine level. The suggested breaker is able to detect and interrupt any cascading of faults.

RESEARCH AND EVALUATION OF FUNCTIONAL PARAMETERS OF LOW VOLTAGE DEVICES

To assess the operability and technical condition of low-voltage devices, it is proposed to use the resistance of contact connections. The probability of failure-free operation is proposed to be evaluated by the dependence of the resistance of the contact connections of the apparatus on the number of switching operations. As a result of wear, the initial value of the contact resistance of the switching device increases and reaches a critical value at which the switching device fails. Due to the fact that in the process of research there are both complete contact failures and short-term switching of only one time, the contact resistance is exceeded by the contact resistance of the threshold value. For magnetic starters, circuit breakers and contactors, based on the results of the experimental studies carried out, in order to achieve the critical resistance value of the apparatus, аn average of three times the initial resistance. At the same time, the quantitative characteristics of the functioning efficiency are determined by the methods of probability theory and mathematical statistics. The set of the obtained quantitative indicators allows to determine the actual level of reliability of contacting, and also extends the possibility of predicting performance ratings in the design. In the present article, a method for the complex evaluation of the efficiency of low-voltage apparatus has been developed and the laws of the change in the resistance of contact connections and the probability of failure-free operation of low-voltage switching devices have been revealed, depending on the operating conditions.

History of Aircraft Wiring Arc-Fault Protection [History

In both new and aging military and civilian aircraft, all critical power wiring has been typically protected against overheating by using combinations of thermal and magnetic circuit breakers or solid-state power controllers (SSPCs). However, the conventional types of these protective devices do not detect and react to hazardous arcing faults, and it is important that they do so to mitigate the risk of aircraft fires caused by aging, damaged insulation, wire chafing, wire breakage, chemical exposure, maintenance procedures, and contamination. Most aircraft electrical systems operate at 115 Vac, 400 Hz, both single and three phase. In addition to this ac power, they utilize 28 Vdc. Hazardous arcing faults can occur in all these power systems between parallel conductors, to ground, or in series (due to a broken or frayed wire or at a loose connection).

A Review Paper on Current Transformer

A current transformer, also known as series transformer is a type of instrument transformer. Current transformer is an electric device which “steps down” the current, by means of primary and secondary winding. Current transformer produces an alternating current in its secondary which is proportional to the alternating current in its primary. Current transformer plays a vital role in protective systems such as relays and meters, so it is essential to obtain maximum accuracy. Current transformer is used with many electric instruments such as Wattmeter, power factor meters, as trip coils in magnetic circuit breakers, or MCB's and hence it can be said that Current transformer can be used in those applications where current is very high to be measured directly. An extensive review process of around 10 research papers results three major key issues “Burden, Saturation condition during fault, Variable phase error and variable ratio error, ” which have important role in the enhancement of accuracy. Study of these issues result various solutions and techniques which make the use of current transformer more dominant and effective.

Is My UPS Distribution System Coordinated?

This paper reviews typical uninterruptible power supply (UPS) distribution systems for the petroleum and chemical industries, focusing on the selectivity of interrupting devices during short-circuit conditions. When selectivity is not achieved, alternative solutions are proposed. Distribution-system-selectivity comparisons are performed for standard circuit-breaker panelboards, fuse panelboards, and custom panelboards utilizing hydraulic magnetic circuit breakers. When remote panels are implemented, application considerations should include oversizing feeder cables or using step-up/step-down transformers. To determine the ride through response of operating plant individual UPS loads, the voltage-depression time during UPS distribution-system-fault clearing is compared with the load ride through capability. General guidelines are provided for improved UPS distribution-system performance

고조파 전류에 의한 배선용 차단기 동작 특성

Malfunction and nuisance tripping of molded case circuit breaker(MCCB) caused by harmonic currents have been reported. But no data is available on the behavior of MCCB under harmonic currents. This paper tested the effects of harmonic currents on four common types of MCCB(thermal, thermal magnetic, magnetic and electronic types). Results of experiment detected no nuisance tripping with any of the breakers tested under test currents, included harmonic current, below rated currents. Additionally it was found that varying harmonic loading conditions did not affect manufacturer specified trip times for thermal only and thermal magnetic circuit breakers. However, under overloaded conditions, trip times of the magnetic only circuit breakers were gradually slowed according to increasing of harmonic currents, and it could cause hazardous overheating of cables. So, the use of magnetic only circuit breakers in the place harmonic currents we serious must be avoided.

Characteristic Analysis and Modification of PM-Type Magnetic Circuit Breaker

This paper presents the operating characteristic analysis of a permanent magnet (PM)-type magnetic circuit breaker using the two-dimensional finite-element magnetic field solution, taking into account nonlinearity of the material and the eddy current. The effect of the eddy current on the dynamic characteristic of the breaker is analyzed from the finite-element analysis. A new modified model to decrease the eddy current is proposed. The characteristics of the two models are compared.

Measurements of fast rise-time transients switching large 13.2 kV motors

A method of fast rise-time transient voltage measurements on actual 13.8 kV switchgear installations is presented. The system configurations as well as the instrumentation and test set-up are described. Results are presented from both low voltage (50 V) and rated voltage (13.8 kV) tests. Measurements on air magnetic and vacuum circuit breakers are included. >

Effects of system parameters and circuit breaker characteristics on switching large synchronous motors

Interturn insulation breakdown in stator windings resulted in the failure of thirteen 21000 HP synchronous motors. To confirm if the failures were caused by steep-front voltage surges, field measurements were conducted during switching operation of one of the compressed air magnetic circuit breakers in one of the affected plants. The results indicate that the number of motors running in parallel with the one being switched affects the magnitude of the generated overvoltage. It is concluded that the failures occurred as a result of breaker tripping during aborted motor starts (while running-up to speed).< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Turn Insulation Capability of Large AC Motors Part 1 - Surge Monitoring

Failure of many large ac motors in generating stations is caused by failure of the turn insulation in the stator winding. Fast risetime surges resulting from circuit breaker switching operations can cause severe voltage stress on the turn insulation due to the non-uniform distribution of voltage across the winding. In order to characterize the surge environment as seen by typical utility motors in normal service, an extensive program of surge monitoring has been undertaken. This work was done as one part of an EPRI funded project to investigate the turn insulation capability of large ac machines. The results of monitoring switching surges for 26 motors controlled by air magnetic circuit breakers and 7 motors controlled by vacuum switchgear in 11 utilities are presented. No significant surges were ever detected during circuit breaker opening operations. Surges with magnitudes as high as 4.6 pu were measured during normal motor starting operations. Tests on a motor switched by an air magnetic circuit breaker, and then a vacuum contactor, showed no significant differences in surge risetimes and magnitudes as recorded at the motor terminals. However vacuum switchgear does give rise to a large number of steep fronted transients for each motor closing operation. Some correlation was found between motor feeder cable types and switching surge characteristics.

Research on a New Type Magnetic Puffer Gas Circuit Breaker

The magnetic repulsive force which arises between a secondary short circuit ring and a primary coil through which short circuit current flows was used for a new magnetic puffer gas circuit breaker. A floating piston type magnetic puffer circuit breaker showed much success in experiments and the examples of theoretically calculated results together with a fixed piston type magnetic puffer circuit breaker are shown by the authors for the first time. It is proved that the interrupting performance of SF6 gas circuit breakers is much improved with the addition of a simple magnetic drive mechanism as shown in the following.

Testing Magnetic Air Circuit Breakers for 5-Cycle Performance

Magnetic air circuit breakers are now rated 8 cycles even though they inherently demonstrate 5-cycle performance. It is therefore the responsibility of the manufacturer to test the circuit breakers so that the duty imposed by the system does not result in misapplications. To assure proper application as 5-cycle breakers the tests should show that: 1. The interrupting time does not exceed 5 cycles. 2. The rated interrupting current shall be symmetrical amperes. 3. An asymmetrical current, whose total rms value is 10% greater than the rated interrupting current, be interrupted. 4. All interrupting tests be made with a recovery voltage equal to the system voltage.

Leakage-flux suppression in magnetic air breakers

THE MAGNETIC AIR CIRCUIT BREAKER, during the past two decades, has become a most effective and widely used circuit-interrupting device. The need for increased ratings in magnetic air circuit breakers has required critical studies of and improvements in the various factors involved in the interrupting process in these devices. One important factor, the magnetic field, has been improved in a number of ways, but the inherently large leakage flux has not been appreciably affected by these improvements. Studies made on such a-c energized magnetic field structures indicated that the total leakage flux was 50% or more of the total flux emerging from the magnet core.

A new 5-kv 50,000-kva de-ion air circuit breaker

Continuous development work on magnetic air circuit breakers has produced many outstanding changes, as is demonstrated by this electrically and mechanically improved design. Its better operation and reliability is verified by test data.

Flux Measurements in Magnetic Air Circuit Breaker Interrupters [includes discussion

Flux Measurements in Magnetic Air Circuit Breaker Interrupters [includes discussion