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11 pages, 39918 KiB

Open AccessArticle

Aging Characteristics of Contact Electrodes of Low Voltage DC Switches

by Hyosung Kim

Energies 2021, 14(20), 6838; https://doi.org/10.3390/en14206838 - 19 Oct 2021

Cited by 3 | Viewed by 2169

Abstract

With the present state of the direct current (DC) distribution market, securing the safety of the DC distribution system is emerging as a major issue. Like AC distribution systems, DC switches and circuit breakers are one of the main means to ensure safety. [...] Read more.

With the present state of the direct current (DC) distribution market, securing the safety of the DC distribution system is emerging as a major issue. Like AC distribution systems, DC switches and circuit breakers are one of the main means to ensure safety. However, in the DC system, since there is no current zero point in the load current, the phenomenon occurring when the circuit is cut off is different from that of the AC system, so technical research is required to cope with this. In this study, the aging characteristics of the contact electrode of a 400 V class low voltage DC (LVDC) switch is studied for the development of wall-mount switches or circuit breakers for residential houses. As an arc extinguishing method to break DC load current, a prototype experimental circuit breaker that uses a magnetic extinguishing method that is effective for blocking low voltage low power DC is invented, and an automated experiment system is established. The DC switch test repeats the operation of turning it on and off 13,000 times, and continuously evaluates the performance of the electric contacts by calculating the voltage drop between the electrode contacts and the corresponding Ohmic resistance value when conducting every 500 times. This paper tests six contact materials to compare the aging characteristics of them by evaluating contact resistance during the test period. AW18-Cu composite material showed the most stable and excellent contact performance for LVDC switches during the entire test operation period. Full article

(This article belongs to the Special Issue DC Circuit Breaker Technologies State of Art)

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17 pages, 11650 KiB

Open AccessArticle

Operation Characteristics of Mechanical DC Circuit Breaker Combined with LC Divergence Oscillation Circuit for High Reliability of LVDC System

by Sang-Yong Park and Hyo-Sang Choi

Energies 2021, 14(16), 5097; https://doi.org/10.3390/en14165097 - 18 Aug 2021

Cited by 7 | Viewed by 2720

Abstract

DC systems are modernly starting to come into the spotlight again due to the carbon-neutral policy, the development of semiconductor devices for power, and the increase in digital loads. We need to prepare in advance solutions to problems that may arise from fault [...] Read more.

DC systems are modernly starting to come into the spotlight again due to the carbon-neutral policy, the development of semiconductor devices for power, and the increase in digital loads. We need to prepare in advance solutions to problems that may arise from fault currents due to transients for future DC power grid models. In the case of DC, there is no current zero-point because there is no frequency. Therefore, a large switching surge is generated when the circuit breaker cuts off the fault current. The possibility of insulation breakdown is greater than that of AC in severe cases. We consider power semiconductors or superconducting current limiters as an alternative. However, DC breaking cannot be safely achieved by itself. For reliable DC breaking, mechanical circuit breakers must be used with them. Among the mechanical shut-off methods, we adopted the divergence oscillation method. It has the biggest advantage compared to other methods in that it has a simple structure by composing passive elements and can artificially create zero current. In addition, it can be applied to a power semiconductor and a superconducting current limiter to perform a high-reliability cut-off operation. In this paper, we conducted simulation analysis by configuring the DC power grid and DC cut-off system through the PSCAD/EMTDC program. Results confirmed that the application of the LC divergence oscillation circuit can reduce the cut-off time and reduce the power burden of the mechanical DC circuit breaker (MCB). Full article

(This article belongs to the Special Issue DC Circuit Breaker Technologies State of Art)

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11 pages, 2541 KiB

Open AccessArticle

Improvement of DC Fault Current Limiting and Interrupting Operation of Hybrid DC Circuit Breaker Using Double Quench

by Sang-Jae Choi, Jun-Hyup Lee, Jin-Wook Lee and Sung-Hun Lim

Energies 2021, 14(14), 4157; https://doi.org/10.3390/en14144157 - 9 Jul 2021

Cited by 2 | Viewed by 1482

Abstract

In this paper, direct current (DC) fault current limiting and interrupting operation of hybrid DC circuit breaker (DCCB) using double quench, which consists of DCCB, a series resonance circuit, power electronic switch, surge arrestor, two separated current limiting reactor/resistor, and two superconducting elements, [...] Read more.

In this paper, direct current (DC) fault current limiting and interrupting operation of hybrid DC circuit breaker (DCCB) using double quench, which consists of DCCB, a series resonance circuit, power electronic switch, surge arrestor, two separated current limiting reactor/resistor, and two superconducting elements, were suggested. The suggested hybrid DCCB can perform the interrupting operation after twice or once DC fault current limiting operation according to DC fault current amplitude. To verify the effective operation of the suggested hybrid DCCB, the modeling for the components of DCCB, the surge arrestor, and the SCE was carried out and its DC operational characteristics were analyzed. Through the analysis of the modeling results for the suggested hybrid DCCB, the advantages of hybrid DCCB were discussed. Full article

(This article belongs to the Special Issue DC Circuit Breaker Technologies State of Art)

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13 pages, 5891 KiB

Open AccessArticle

DC Solid-State Circuit Breakers with Two-Winding Coupled Inductor for DC Microgrid

by Jung-min Park, Hyung-jun Byun, Sung-hun Kim, Si-hwan Kim and Chung-yuen Won

Energies 2021, 14(14), 4129; https://doi.org/10.3390/en14144129 - 8 Jul 2021

Cited by 3 | Viewed by 2168

Abstract

Ensuring a protection scheme in a DC distribution system is more difficult to achieve against pole-to-ground faults than in AC distribution system because of the absence of zero crossing points and low line impedance. To complement the major obstacle of limiting the fault [...] Read more.

Ensuring a protection scheme in a DC distribution system is more difficult to achieve against pole-to-ground faults than in AC distribution system because of the absence of zero crossing points and low line impedance. To complement the major obstacle of limiting the fault current, several compositions have been proposed related to mechanical switching and solid-state switching. Among them, solid-state circuit breakers (SSCBs) are considered to be a possible solution to limit fast fault current. However, they may cause problems in circuit complexity, reliability, and cost-related troubles because of the use of multiple power semiconductor devices and additional circuit configuration to commutate the current. This paper proposes a SSCB with a coupled inductor (SSCB-CI) that has a symmetrical configuration. The circuit is comprised of passive components like commutation capacitors, a CI, and damping resistors. Thus, the proposed SSCB-CI offers the advantages of a simple circuit configuration and fewer utilized power semiconductor devices than the other typical SSCBs in the DC microgrid. For the analysis, six operation states are described for the voltage across the main switches and fault current. The effectiveness of the SSCB-CI against the short-circuit fault is proved via simulation and experimental results in a lab-scale prototype. Full article

(This article belongs to the Special Issue DC Circuit Breaker Technologies State of Art)

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13 pages, 4423 KiB

Open AccessArticle

Impact on Current-Interrupting Characteristic by Parameter Settings of Superconducting Hybrid DC Circuit Breaker

by Sang-Jae Choi and Sung-Hun Lim

Energies 2021, 14(9), 2469; https://doi.org/10.3390/en14092469 - 26 Apr 2021

Cited by 5 | Viewed by 1622

Abstract

DC faults cause severe disruption in not only the DC system but also the AC system because the fault current is very large and rapidly increases. The DC circuit breaker used to separate the DC faults from the power system is still being [...] Read more.

DC faults cause severe disruption in not only the DC system but also the AC system because the fault current is very large and rapidly increases. The DC circuit breaker used to separate the DC faults from the power system is still being researched, but it is very expensive due to the use of multiple power semiconductors to interrupt a large fault current in a short time. However, if the quench characteristic of a superconductor is used, the amplitude of fault current can be reduced. Therefore, it is possible to effectively interrupt a large fault current even if a relatively cheap mechanically passive DC circuit breaker is used. In the current study, a superconducting hybrid DC circuit breaker is proposed, and the limiting characteristics of each element are analyzed. By using two superconducting elements, the quench occurs sequentially twice according to the magnitude of the fault current, and the current-limiting reactor and resistance are used. If a current-limiting reactor is used in the DC system, the fault current rises slowly at the beginning of the fault, and the use of resistance can reduce the magnitude of the fault current. The inductance of the current-limiting reactor and resistance parameter settings of the hybrid DC circuit breaker was analyzed by the step-changing case method, and the interrupting characteristic of the DC circuit breaker was improved. Full article

(This article belongs to the Special Issue DC Circuit Breaker Technologies State of Art)

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13 pages, 3652 KiB

Open AccessArticle

Operation Characteristics for the Superconducting Arc-Induction Type DC Circuit Breaker

by Sangyong Park and Hyosang Choi

Energies 2020, 13(15), 3897; https://doi.org/10.3390/en13153897 - 30 Jul 2020

Cited by 4 | Viewed by 2130

Abstract

The multi-terminal direct current network is expected to commercialize while carrying out projects related to DC power systems worldwide. Accordingly, it is necessary to develop a DC circuit breaker required for the DC power system. A DC circuit breaker should be developed to [...] Read more.

The multi-terminal direct current network is expected to commercialize while carrying out projects related to DC power systems worldwide. Accordingly, it is necessary to develop a DC circuit breaker required for the DC power system. A DC circuit breaker should be developed to protect the DC power system and the consumer from the transient state on the line in any case. Currently, the use of power semiconductors increases the performance of DC circuit breakers. However, power semiconductors are expensive and suffer series of losses from frequent failures. Therefore, the DC circuit breaker must have a reliable, stable, and inexpensive structure. We proposed a new type of arc-induction type DC circuit breaker. It consists of a mechanical blocking contact, an induction needle and a superconducting magnet. It blows the arc with an induction needle using the Lorentz force according to the high magnetic field of the superconducting magnet. The arc-induction needle absorbs the arc and flows through the ground wire to the ground to extinguish the arc. We established this principle of arc induction as a mathematical model. In addition, the Maxwell program was used to secure data of electric and magnetic fields and apply them to mathematical models. The results obtained through numerical analysis were analyzed and compared. As a result, we confirmed that the magnitude of the force exerted on the electrons between the mechanical contacts with the superconducting magnets increased about 1.41 times and reasoned the arc-induction phenomenon out numerically. Full article

(This article belongs to the Special Issue DC Circuit Breaker Technologies State of Art)

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Review

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15 pages, 3259 KiB

Open AccessReview

Modeling and Estimation of Break Arc Extinction Distance in Low Voltage DC Systems

by Yong-Jung Kim and Hyo-Sung Kim

Energies 2021, 14(20), 6646; https://doi.org/10.3390/en14206646 - 14 Oct 2021

Cited by 3 | Viewed by 1967

Abstract

Recently, as DC power generation and DC loads such as renewable energy and EVs increase, the need for a low-voltage direct current (LVDC) distribution system has gradually emerged. The DC system has various advantages, such as system stability, transmission efficiency, and connectivity to [...] Read more.

Recently, as DC power generation and DC loads such as renewable energy and EVs increase, the need for a low-voltage direct current (LVDC) distribution system has gradually emerged. The DC system has various advantages, such as system stability, transmission efficiency, and connectivity to renewable power generation compared to AC distribution systems. One of the important technical issues for commercialization of DC distribution system is safety. Since the DC system does not have a current zero point, unlike the AC system, a breaking arc accompanied by a high-temperature plasma is easily generated when the circuit is cut off. The arc can cause fire accidents that threaten people and facilities. In order to prevent customers and facilities from the accidents caused by the arc in the DC system, a study on the characteristics of the DC breaking arc is necessary. An important factor of characteristics for the DC breaking arc fault is an arc extinction distance at which the DC breaking arc is completely extinguished. There are two major behaviors in DC breaking arc; one is active behavior where the arc voltage is inversely related with the arc current for a given gap distance, the other is passive behavior where the arc voltage is negatively proportional to the arc current according to Kirchhoff’s voltage rule. This paper combines the two arc characteristics together to establish a DC breaking arc model, and proposes a method to estimate the arc extinction distance. Experiment results verify the method under various power and load conditions. Full article

(This article belongs to the Special Issue DC Circuit Breaker Technologies State of Art)

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9 pages, 2282 KiB

Open AccessReview

Gate Drive Controller for Low Voltage DC Hybrid Circuit Breaker

by Hyosung Kim

Energies 2021, 14(6), 1753; https://doi.org/10.3390/en14061753 - 22 Mar 2021

Cited by 6 | Viewed by 2014

Abstract

With the advent of direct current (DC) loads such as LED lighting, IT equipment, electric vehicles, and DC powers generated from renewable energy sources, low voltage DC (LVDC) distribution system is becoming a hot issue. One of the hurdles in the LVDC distribution [...] Read more.

With the advent of direct current (DC) loads such as LED lighting, IT equipment, electric vehicles, and DC powers generated from renewable energy sources, low voltage DC (LVDC) distribution system is becoming a hot issue. One of the hurdles in the LVDC distribution system is arc flash at the contact points that occurs during the circuit is opening. Unlike alternating current, direct current has no zero points and sustains constantly. Therefore, there is a risk of electric fire due to continuous generating arcs when the load current is interrupted with an existing electrical contact type circuit breaker. Recently, the concept of a hybrid circuit breaker that takes advantage of traditional electrical contact type switch and the arcless semiconductor switch has been proposed, but how to cooperatively operate the two switches has become an issue. This paper analyzes the principle of a hybrid circuit breaker for blocking LVDC current and proposes a gate drive controller for it. Through 400V class LVDC cutoff test, the operation of the proposed hybrid circuit breaker is verified and the characteristics are analyzed. Full article

(This article belongs to the Special Issue DC Circuit Breaker Technologies State of Art)

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