Fault current limiter

This specification relates to fault current limiter (FCL). More particularly, to solve problems of protecting and designing current limiting impedance in a protective coordination system, as limitations of the related art, the fault current limiter may measure heat capacity of a current limiting impedance unit by detecting fault current flowing to the current limiting impedance unit and limiting the fault current flowing to the current limiting impedance unit according to the measured heat capacity, which may result in preventing the current limiting impedance unit from being damaged due to the fault current, preventing an extended accident due to the damaged current limiting impedance unit and enabling a stabilized system and line protection.

CROSS-REFERENCE TO RELATED APPLICATIONS

Pursuant to 35 U.S.C. §119(a), this application claims the benefit of earlier filing date and right of priority to Korean Application No. 10-2014-0057438, filed on May 13, 2014, the contents of which are all incorporated by reference herein in their entirety.

BACKGROUND OF THE DISCLOSURE

1. Field of the Disclosure

This specification relates to fault current limiter, and more particularly, fault current limiter, capable of preventing damage of fault current impedance unit due to fault current, by detecting the fault current flowing to the current limiting impedance unit and accordingly switching a flow path of the fault current.

2. Background of the Disclosure

In general, fault current limiters (FCLs) do not have blocking capabilities by themselves. Thus, the FCL allows the flow of limited fault current until a circuit breaker installed in a system blocks the fault current. In typical protective coordination, as illustrated inFIG. 1, for a fault F2, fault current should be blocked by a second circuit breaker CB2. When the CB2malfunctions due to having a trouble, a first circuit breaker CB1operates as backup protection. And, for a fault F1, fault current is blocked by the CB1. Hence, heat capacity of the conventional FCL impedance has been designed and manufactured even by taking into account a blocking time taken by the backup protection of the CB1due to the malfunctioned CB2. In the system illustrated inFIG. 1, the backup protection of the CB1is carried out due to the malfunctioned CB2, and thus a normal protective coordination system should operate. However, when even the CB1to operate as the backup protection fails to block the fault current due to its malfunction, a current over a reference value flows to the impedance of the FCL which has been designed based on the conventional normal protective coordination system. Therefore, the heat capacity of the impedance of the FCL increases over a designed value. This may be likely to cause damage to the FCL and a problem even in the system.

SUMMARY OF THE DISCLOSURE

Therefore, an aspect of the detailed description is to provide fault current limiter, capable of overcoming problems of protection and design of current limiting impedance in a protective coordination system, which are the limitations in the related art, in a manner of detecting fault current flowing to a current limiting impedance unit, measuring heat capacity of the current limiting impedance unit thereof, and accordingly limiting the fault current flowing to the current limiting impedance unit.

To achieve these and other advantages and in accordance with the purpose of this specification, as embodied and broadly described herein, there is provided fault current limiter (FCL) including a first switching unit configured to block an applied fault current and switch a flow path of the fault current, a current limiting impedance unit configured to limit the fault current, a second switching unit configured to switch over a flow path of the fault current connected to the current limiting impedance unit such that the fault current flowing toward the current limiting impedance unit can be limited, and a controller configured to detect the fault current, compare the detected result with a preset reference value, and control the second switching unit according to the comparison result.

In one exemplary embodiment disclosed herein, the fault current may be one of a ground fault current, a short-circuit current and an overload current.

In one exemplary embodiment disclosed herein, the first switching unit may allow the fault current to flow to the current limiting impedance unit when the fault current is applied.

In one exemplary embodiment disclosed herein, the first switching unit may include a superconductor configured to block the flow of the fault current in a manner that a resistance value thereof is increased by the fault current, and a contact switching portion configured to switch the flow path of the fault current toward the current limiting impedance unit,

In one exemplary embodiment disclosed herein, the current limiting impedance unit may include at least one current limiting impedance element.

In one exemplary embodiment disclosed herein, the second switching unit may include a current flowing portion connected in parallel to the current limiting impedance unit, and an auxiliary impedance portion connected in series to the current limiting impedance unit.

In one exemplary embodiment disclosed herein, the current flowing portion may be a flow path to which the fault current is bypassed for flow. The current flowing portion may be configured as a switching element that is open in a normal condition and closed during an operation.

In one exemplary embodiment disclosed herein, the auxiliary impedance portion may include at least one auxiliary current limiting impedance element, and a changeover switch portion configured to switch over a connection between the current limiting impedance unit and each of the at least one auxiliary current limiting impedance element.

In one exemplary embodiment disclosed herein, the preset reference value may be a reference value set according to a maximum rated capacity of the current limiting impedance unit.

In one exemplary embodiment disclosed herein, the controller may include a CT configured to detect the fault current, so as to measure magnitude and duration of the fault current and heat capacity of the current limiting impedance unit.

In one exemplary embodiment disclosed herein, the controller may control the second switching unit to limit the fault current flowing to the current limiting impedance unit, when the measured result exceeds the preset reference value.

In one exemplary embodiment disclosed herein, the controller may control an operation of the second switching unit according to a degree that the detected result exceeds the preset reference value.

Fault current limiter (FCL) disclosed herein may prevent a current limiting impedance unit from being damaged due to fault current, by detecting the fault current flowing to the current limiting impedance unit, measuring heat capacity of the current limiting impedance unit, and limiting the fault current flowing to the current limiting impedance unit according to the heat capacity.

In the FCL disclosed herein, the prevention of the damage on the current limiting impedance unit due to the fault current by way of limiting the fault current flowing to the current limiting impedance unit may result in preventing expansion of an accident due to the damaged current limiting impedance unit.

In the FCL disclosed herein, the prevention of the expanded accident due to the damaged current limiting impedance unit by way of preventing the damage on the current limiting impedance unit due to the fault current may result in enabling stabilization of a system and line protection.

In the FCL disclosed herein, the prevention of the expanded accident due to the damaged current limiting impedance unit by way of preventing the damage on the current limiting impedance unit due to the fault current may result in facilitating protective coordination with other equipment.

The FCL disclosed herein may be allowed for application thereof according to capacity, by virtue of the configuration of detecting the fault current flowing to the current limiting impedance unit, measuring the heat capacity of the current limiting impedance unit, and limiting the fault current flowing to the current limiting impedance unit according to the heat capacity.

The FCL disclosed herein may have an expanded lifespan by virtue of the allowed application according to the capacity.

A FCL having an appropriate capacity can be easily designed by virtue of the allowed application of the FCL disclosed herein according to the capacity.

DETAILED DESCRIPTION OF THE DISCLOSURE

The invention disclosed herein may be applied, but not limited, to fault current limiter (FCL) which limits fault current flowing on a circuit or line. The technology disclosed herein may also be applied to any type of protective equipment, such as the conventional switch, relay, surge absorber, electronic contactor and circuit breaker, to which the technical idea of the present invention can be applied, and to current limiter circuits included in the protective equipment. Specifically, the FCL may be usefully practiced by being applied to monitoring equipment and protective equipment for protecting circuits which require for protective coordination with systems and ambient protective equipment.

It should be noted that technological terms used herein are merely used to describe a specific embodiment, but not to limit the present invention. Also, unless particularly defined otherwise, technological terms used herein should be construed as a meaning that is generally understood by those having ordinary skill in the art to which the invention pertains, and should not be construed too broadly or too narrowly. Furthermore, if technological terms used herein are wrong terms unable to correctly express the spirit of the invention, then they should be replaced by technological terms that are properly understood by those skilled in the art. In addition, general terms used in this invention should be construed based on the definition of dictionary, or the context, and should not be construed too broadly or too narrowly.

Incidentally, unless clearly used otherwise, expressions in the singular number include a plural meaning. In this application, the terms “comprising” and “including” should not be construed to necessarily include all of the elements or steps disclosed herein, and should be construed not to include some of the elements or steps thereof, or should be construed to further include additional elements or steps.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings, and the same or similar elements are designated with the same numeral references regardless of the numerals in the drawings and their redundant description will be omitted.

In describing the present invention, moreover, the detailed description will be omitted when a specific description for publicly known technologies to which the invention pertains is judged to obscure the gist of the present invention. Also, it should be noted that the accompanying drawings are merely illustrated to easily explain the spirit of the invention, and therefore, they should not be construed to limit the spirit of the invention by the accompanying drawings.

Hereinafter, description will be given of fault current limiter (FCL) disclosed herein, with reference toFIGS. 2 to 7.

FIG. 2is a block diagram illustrating a configuration of fault current limiter disclosed herein.

FIG. 3is another block diagram illustrating the configuration of the configuration of the fault current limiter disclosed herein.

FIG. 4is a circuit diagram illustrating a configuration in accordance with an embodiment of fault current limiter disclosed herein.

FIG. 5is another circuit diagram illustrating the configuration in accordance with the embodiment of the fault current limiter disclosed herein.

FIG. 6is an exemplary view illustrating a control setting in accordance with an embodiment of fault current limiter disclosed herein.

FIG. 7is a flowchart illustrating sequential steps of operating fault current limiter disclosed herein.

As illustrated inFIG. 2, the fault current limiter (FCL)500includes a first switching unit100that blocks applied fault current and switches a flow path of the fault current, a current limiting impedance unit200that limits the fault current, a second switching unit300that switches a flow path of the fault current connected to the current limiting impedance unit200to limit the fault current flowing toward the current limiting impedance unit200, and a controller400that detects the fault current, compares the detected result with a preset reference value, and controls the second switching unit300according to the comparison result.

The FCL500refers to protective equipment which limits fault current generated due to abnormal conditions, such as faults (accidents) occurred on a system and lines.

The FCL500may be protective equipment which performs a function of limiting a magnitude (amount, strength, etc.) and flow duration of the fault current.

The FCL500may protect the line from the fault current through protective coordination with other protective equipment, such as a circuit breaker which breaks the line, a switch, a relay and the like.

For example, the FCL500may be installed between a circuit breaker A performing a main protecting function and a circuit breaker B performing a sub protecting function. The FCL500may limit the fault current after the operation of the circuit breaker A performing the main protecting function and until before the operation of the circuit breaker B performing the sub protecting function, thereby enabling the protective coordination for preventing expansion of an accident.

The fault current may be a current which is generated due to an abnormal state, such as faults occurred on a system and a line.

That is, when the fault current has a magnitude (strength) over a rated value, it may be likely to cause breakdown of facilities, loads and the like connected to the system and the line.

The fault current may be one of a ground fault current, a short-circuit current and an overload current generated on the system and the line.

Hereinafter, description will be given of a configuration and an operation according to an embodiment of the first switching unit100, with reference toFIGS. 3 to 5.

The circuit of the FCL500, as illustrated inFIG. 3, may be configured by dividing into two parts.

The circuit configuration of the FCL500may be divided into two parts, namely, a part including the first switching unit100connected to an input terminal of the FCL500, and another part including the current limiting impedance unit200, the second switching unit300and the controller400which are connected to the first switching unit100.

As one of the two circuit parts of the FCL500, the first switching unit100may allow the fault current to flow to the current limiting impedance unit200when the fault current is applied.

The first switching unit100, as illustrated inFIG. 4, may include a superconductor110whose resistance value is increased by the fault current so as to block the flow of the fault current, and a contact switching portion120that switches over the flow path of the fault current such that the fault current can flow toward the current limiting impedance unit200.

The superconductor110may be a variable resistor which maintains a resistance value allowing for a flow of a current during a normal operating state and increases the resistance value when the fault current is applied.

For example, the superconductor110may maintain a resistance value of 10[Ω] such that a current can flow. However, when the fault current is applied, the superconductor110may recognize it and increase the resistance value up to 10 [KΩ] to make it difficult for the current to flow.

That is, when the fault current is applied, the resistance value of the superconductor110may increase, and accordingly the fault current can be blocked by the increased resistance value, without flowing along the existing flow path.

The contact switching portion120may perform a function of switching over the flow path of the fault current which has been bypassed due to the increased resistance value of the superconductor110.

The contact switching portion120may include at least one switching element121and123.

The contact switching portion120may additionally include a relaying element122that enables an operation of the at least one switching element121and123.

The at least one switching element may be configured as one contact switching element of a contact a121or a contact b123.

The contact a121refers to a contact which is closed in a normal condition and opened during an operation.

The contact b123refers to a contact which is opened in a normal condition and closed during an operation.

The relaying element122may be relayed when a current flows, so as to enable the operations of the contact a121and the contact b123.

The contact switching portion120may be configured such that the relaying element122and the contact b123are connected in parallel, and the parallel-connected relaying element122and contact b123are connected to the contact a121in series.

That is, one end of the relaying element122may be connected to one end of the contact b123and the other end of the relaying element122may be connected to the other end of the contact b123. Here, the other ends of the relaying element122and the contact b123may be connected to one end of the contact a121.

When the relaying element122is relayed in response to a current applied thereto, the contact a121and the contact b123may operate such that the contact a121can be open and the contact b123can be closed.

Hereinafter, an example of the circuit configuration and the operation of the first switching unit100will be described, with reference toFIG. 4.

One end of the superconductor110may be connected to the input terminal of the FCL500such that a current applied to the FCL500can flow to the superconductor110.

The other end of the superconductor110may be connected to one end of the contact a121included in the contact switching portion120, such that the current flowed to the superconductor110can flow through the contact a121which is in a closed state.

The superconductor110may also be connected in parallel to the relaying element122and the contact b123included in the contact switching portion120, such that the current bypassed by the superconductor110can flow to one of the relaying element122and the contact b123.

That is, one end of the superconductor110may be connected to one end of each of the relaying element122and the contact b123and the other end of the superconductor110may be connected to the other end of each of the relaying element122and the contact b123. Here, the other ends of the superconductor110, the relaying element122and the contact b123may be connected to one end of the contact a121.

An initial resistance value of the superconductor110may be smaller than a resistance value of the relaying element122.

That is, the superconductor110, the relaying element122and the contact b123may be connected in parallel to one another. Here, since the resistance value of the superconductor110is smaller than the resistance values of the relaying element122and the contact b123, the current applied to the FCL500may flow toward the superconductor110.

When the current is applied to the FCL500, the current may be applied to the superconductor110which has the smallest resistance value among the superconductor110, the relaying element122and the contact b123, and then flow through the contact a121which is connected in series to the superconductor110.

When the fault current is applied to the FCL500, the resistance value of the superconductor110may be increased by the fault current. The increased resistance value of the superconductor110may bypass the fault current to flow toward the relaying element122. In response to the flow of the fault current, the relaying element122may be relayed to operate the contact a121in a closed state and the contact b123in an open state. Accordingly, the contact a121may be open and the contact b123closed, thereby switching over the flow path of the fault current.

Once the flow of the fault current is blocked and the flow path of the fault current is switched over by the first switching unit100, the fault current may be bypassed by the first switching unit100and thus flow toward the current limiting impedance unit200.

Hereinafter, description will be given of configurations and operations of the current limiting impedance unit200, the second switching unit300and the controller40according to an embodiment disclosed herein, with reference to FIG.5.

As one part of the circuit configuration of the FCL500, the current limiting impedance unit200may limit the magnitude and flow duration of the fault current when the fault current flows by bypassing the first switching unit100.

The current limiting impedance unit200may include at least one current limiting impedance element.

That is, the current limiting impedance unit200may include a plurality of current limiting impedance elements.

The current limiting impedance element may be configured as a resistor having resistance.

The current limiting impedance element may be a resistor with high resistance, so as to limit the magnitude and duration of the fault current.

As one part of the circuit configuration of the FCL500, the second switching unit300may switch over the flow path of the fault current applied toward the current limiting impedance unit200, when the magnitude and duration of the fault current is more than rated values of the current limiting impedance unit200, thereby limiting the fault current applied toward the current limiting impedance unit200.

That is, the second switching unit300may switch the flow path of the fault current which flows toward the current limiting impedance unit200, thereby performing a function of protecting the current limiting impedance unit200from the fault current.

The second switching unit300may include a current flowing portion310connected in parallel to the current limiting impedance unit200, and an auxiliary impedance portion320connected in series to the current limiting impedance unit200.

The current flowing portion310may be a flow path to which the fault current is bypassed so as to flow therealong. The current flowing portion310may be configured as a switching element which is opened in normal conditions and closed during an operation.

The current flowing portion310may be a flow path to which the fault current applied to the current limiting impedance unit200is bypassed by the current limiting impedance unit200for flow.

The current flowing portion310may be closed when the fault current applied to the current limiting impedance unit200is more than a rated value of the current limiting impedance unit200, such that the fault current applied to the current limiting impedance unit200can flow toward the current flowing portion310.

That is, when the fault current applied to the current limiting impedance unit200is more than the rated value of the current limiting impedance unit200, the current flowing portion310may be closed such that the fault current applied to the current limiting impedance unit200can flow toward the current flowing portion310. Accordingly, the current flowing portion310can serve as a substitute flow path for the current limiting impedance unit200.

The auxiliary impedance portion320may include at least one auxiliary current limiting impedance element321, and a changeover switch portion322that switches a connection between the current limiting impedance unit200and each of the at least one auxiliary current limiting impedance element321.

The at least one auxiliary current limiting impedance element321may be connected as one node to at least one flow path without any element.

The at least one auxiliary current limiting impedance element321is an auxiliary element of the current limiting impedance unit200, and may be configured to limit magnitude and duration of the fault current.

That is, the at least one auxiliary current limiting impedance element321may be connected in series to the current limiting impedance unit200, so as to limit the magnitude and duration of the fault current along with the current limiting impedance unit200.

That is, the at least one auxiliary current limiting impedance element321may perform a function of supplementing a limiting capability (resistance value) of the current limiting impedance unit200, which limits the fault current, in a manner of adding its resistance value to the resistance value of the current limiting impedance unit200.

The at least one auxiliary current limiting impedance element321may be configured as the same element as the current limiting impedance element included in the current limiting impedance unit200.

The at least one auxiliary current limiting impedance element321may be a resistor having resistance.

The at least one auxiliary current limiting impedance element321may be configured as a resistor having high resistance, so as to limit the magnitude and duration of the fault current.

The changeover switch portion322may switch over the connection between the current limiting impedance unit200and the at least one auxiliary current limiting impedance element321.

The changeover switch portion322may include at least two changeover switches.

The changeover switch portion322may allow the current limiting impedance unit200to be connected in series to one of the at least one flow path without any element and the at least one auxiliary current limiting impedance element321.

An example illustrating the circuit configurations and operations of the current limiting impedance unit200and the second switching unit300will now be described with reference toFIG. 5.

One end of the current limiting impedance unit200may be connected as one node to an input terminal of the FCL500and one end of each of the superconductor110, the relaying element122and the contact b123, such that the fault current bypassed by the superconductor110, the relaying element122and the contact b123can flow toward the current limiting impedance unit200.

The one end of the current limiting impedance unit200may also be connected to one end of the current flowing portion310included in the second switching unit300such that the fault current flowing toward the current limiting impedance unit200can be bypassed toward the current flowing portion310and flow toward the current flowing portion310.

The other end of the current limiting impedance unit200may be connected to one end of the changeover switch portion322included in the second switching unit300. Accordingly, the other end of the current limiting impedance unit200may be connected to one of one end of the at least one flow path without any element and one end of the at least one auxiliary current limiting impedance element321, by way of the switching of the changeover switch portion322.

The other end of the at least one flow path without any element and the other end of the at least one auxiliary current limiting impedance element321may be connected as one node to the other end of the current flowing portion310, so as to be connected to the first switching unit100or a flow path of an output terminal of the FCL500.

When the fault current flows to the current limiting impedance unit200due to the flow path of the fault current being switched over, the fault current is limited by the current limiting impedance unit200with a high resistance value. Here, when the fault current is more than a rated value of the current limiting impedance unit200, the current flowing portion310included in the second switching unit300is closed such that the fault current flowing to the current limiting impedance unit200can be bypassed to flow to the current flowing portion310, or the current limiting impedance unit200and the auxiliary current limiting impedance element321may be serially connected by the changeover switch portion322of the auxiliary impedance portion320included in the second switching unit300, and accordingly the resistance value of the current limiting impedance unit200and the resistance value of the auxiliary current limiting impedance element321may be added to each other so as to limit the fault current.

The flow path of the fault current which is connected to the current limiting impedance unit200can thusly be changed over by the second switching unit300, thereby enabling the limit of the fault current and the protection of the current limiting impedance unit200from the fault current.

The controller400may be included in the front of the current limiting impedance unit200.

The controller400may be located between the superconductor100, the relaying element122and the contact b123and the current limiting impedance unit200, to detect the fault current flowing to the current limiting impedance unit200.

The controller400may detect the fault current flowing to the current limiting impedance unit200, and compare the detected fault current with the preset reference value.

The preset reference value may be a reference value which is set based on a maximum rated capacity of the current limiting impedance unit200.

That is, in order to prevent the current limiting impedance unit200from being damaged due to the fault current, the controller400may detect the fault current and compares the detected fault current with the reference value, which is set based on the rated value of the current limiting impedance unit200, to thusly control the second switching unit300according to the comparison result, thereby protecting the current limiting impedance unit200from the fault current.

The controller400may include a CT410for detecting the fault current, thereby measuring the magnitude and duration of the fault current, and heat capacity of the current limiting impedance unit200.

The CT410may refer to a device which detects a current flowing on a flow path.

The CT410may be located between the superconductor100, the relaying element122and the contact b123and the current limiting impedance unit200, so as to detect the fault current flowing to the current limiting impedance unit200.

The heat capacity of the current limiting impedance unit200may refer to a quantity of power consumed by the current limiting impedance unit200due to the fault current.

The heat capacity may be measured by [Equation 1], as follows.
W=I2Rt[KWh]  [Equation 1]

where w denotes heat capacity of the current limiting impedance unit200, I denotes magnitude of the fault current flowing to the current limiting impedance unit200, R denotes a resistance value of the current limiting impedance unit200, and t denotes duration of the fault current flowing to the current limiting impedance unit200.

In case where the magnitude of the fault current for measuring the heat capacity, for example, flowing to the current limiting impedance unit200, is 10 [A], the resistance value of the current limiting impedance unit200is 100 [KΩ], and the duration of the fault current flowing to the current limiting impedance unit2002 [s], the heat capacity may be 20000 [KWh] or 20 [MWh].

When the measured result exceeds the preset reference value, the controller400may control the second switching unit300to limit the fault current flowing to the current limiting impedance unit200.

For example, when the measured result is 20000 [KWh] and the preset reference value as the rated value of the current limiting impedance unit200is 15000 [KWh], the measured result may exceed the preset reference value. Accordingly, the controller400may control the second switching unit300to limit the fault current flowing to the current limiting impedance unit200.

When the measured result exceeds the preset reference value, the controller400may control one of the current flowing portion310and the auxiliary impedance portion320included in the second switching unit300to limit the fault current flowing to the current limiting impedance unit200.

When controlling one of the current flowing portion310and the auxiliary impedance portion320included in the second switching unit300, the controller400may perform the control according to priorities of the current flowing portion310and the auxiliary impedance portion320.

That is, the controller400may preferentially control the current flowing portion310to be closed, such that the fault current flowing to the current limiting impedance unit200can be bypassed toward the current flowing portion310. Afterwards, when the current flowing portion310malfunctions or it is difficult to fast close the current flowing portion310, the controller400may control the auxiliary impedance portion320to limit the fault current flowing to the current limiting impedance unit200.

The controller400may control the operation of the second switching unit300according to a degree that the measured result exceeds the preset reference value.

For example, degrees that the measured result exceeds the preset reference value may be divided into levels. Accordingly, an operating time of the second switching unit300may be controlled or one of the current flowing portion310and the auxiliary impedance portion320may be controlled according to a level to which the comparison result corresponds.

A detailed example will be described further with reference toFIG. 6. The operating time of the second switching unit300may be set to be reduced according to the degree that the measured result exceeds the preset reference value. Accordingly, the controller400may control the operating time of the second switching unit300to be reduced according to the level corresponding to the comparison result.

In the instance illustrated inFIG. 6, when the measured result is 20 [KWh] and the preset reference value is 10 [KWh], the measured result exceeds the preset reference value by 10 [KWh]. Accordingly, the controller400may control the operating time of the second switching unit300to be reduced by 0.01 [s] corresponding to the exceeded degree. Or, when the measured result is 50 [KWh] and the preset reference value is 20 [KWh], the measured result exceeds the prefer reference value by 30 [KWh]. Accordingly, the controller400may control the operating time of the second switching unit300to be reduced by 0.03 [s] corresponding to the exceeded degree.

As another example, one of the current flowing portion310and the auxiliary impedance portion320can be controlled according to the degree that the measured result exceeds the preset reference value. Thus, the controller400can control one of the current flowing portion310and the auxiliary impedance portion320according to a level to which the comparison result corresponds. When the degree that the measured result exceeds the preset reference value is low, the controller400may control the auxiliary impedance portion320to operate to limit the fault current. On the other hand, when the degree that the measured result exceeds the preset reference value is high, the controller400may control the current flowing portion310to operate so as for the fault current to be bypassed.

The aforementioned operating order of the FCL is illustrated inFIG. 7.

As illustrated inFIG. 7, the sequential steps of operating the FCL500may include applying fault current (S10), operating a first switching unit (S20), allowing the fault current to flow to a current limiting impedance unit (S30), measuring magnitude and duration of the fault current, and heat capacity of the current limiting impedance unit (S40), comparing the measured result with a preset reference value (S50), controlling a second switching unit according to the comparison result (S60), and limiting the fault current flowing to the current limiting impedance unit (S70).

In the step (S10) of applying the fault current, fault current which is generated due to a fault occurred on a system and a line may be applied to the FCL.

In the step (S20) of operating the first switching unit, the first switching unit may operate such that the fault current applied in the step (S10) of applying the fault current can be bypassed to the current limiting impedance unit for flow.

In the step (S30) of allowing the fault current to flow to the current limiting impedance unit, the fault current which has been bypassed by the operation of the first switching unit in the step (S20) of operating the first switching unit can flow to the current limiting impedance unit.

In the step (S30) of allowing the fault current to flow to the current limiting impedance unit, the magnitude and duration of the fault current may be limited by a current limiting impedance element included in the current limiting impedance unit.

In the step (S40) of measuring the magnitude and duration of the fault current and the heat capacity of the current limiting impedance unit, the magnitude and duration of the fault current, which has flowed in the step (S30) of allowing the fault current to flow to the current limiting impedance unit, may be detected, thereby measuring the heat capacity of the current limiting impedance unit according to the fault current on the basis of the detected result.

In the step (S50) of comparing the measured result with the preset reference value, the heat capacity of the current limiting impedance unit, which has been measured in the step (S40) of measuring the magnitude and duration of the fault current and the heat capacity of the current limiting impedance unit, may be compared with the preset reference value.

In the step (S50) of comparing the measured result with the preset reference value, the preset reference value may be a reference value set according to a maximum rated capacity of the current limiting impedance unit, and the heat capacity of the current limiting impedance unit may be a quantity of power consumed by the current limiting impedance unit due to the fault current.

In the step (S60) of controlling the second switching unit according to the comparison result, according to the comparison result between the measured result and the preset reference value in the step (S50) of comparing the measured result with the preset reference value, when the measured result exceeds the preset reference value, the second switching unit may be controlled to limit the fault current flowing to the current limiting impedance unit.

In the step (S60) of controlling the second switching unit according to the comparison result, the second switching unit can be controlled such that the fault current flowing to the current limiting impedance unit can be bypassed for flow, or the fault current flowing to the current limiting impedance unit can be limited by adding a resistance value of the current limiting impedance unit.

In the step (S70) of limiting the fault current flowing to the current limiting impedance unit, the second switching unit may be controlled in the step (S60) of controlling the second switching unit according to the comparison result, such that the fault current can be limited from flowing to the current limiting impedance unit. This may result in protecting the current limiting impedance unit from the fault current.

The embodiments of the FCL disclosed herein may be practiced by being applied to FCLs limiting fault current flowing on a line.

The embodiments of the FCL disclosed herein may be applied to switches, relays, surge absorbers, electronic contactors and circuit breakers.

The embodiments of the FCL disclosed herein may be applied to any type of line protective equipment and current limiting circuits included in the protective equipment.

The embodiments of the FCL disclosed herein may be applied to monitoring devices and protective equipment for protecting lines which require for protective coordination with systems and ambient protective equipment.

Fault current limiter (FCL) disclosed herein may prevent a current limiting impedance unit from being damaged due to fault current, by detecting the fault current flowing to the current limiting impedance unit, measuring heat capacity of the current limiting impedance unit, and limiting the fault current flowing to the current limiting impedance unit according to the heat capacity.

In the FCL disclosed herein, the prevention of the damage on the current limiting impedance unit due to the fault current by way of limiting the fault current flowing to the current limiting impedance unit may result in preventing expansion of an accident due to the damaged current limiting impedance unit.

In the FCL disclosed herein, the prevention of the expanded accident due to the damaged current limiting impedance unit by way of preventing the damage on the current limiting impedance unit due to the fault current may result in enabling stabilization of a system and line protection.

In the FCL disclosed herein, the prevention of the expanded accident due to the damaged current limiting impedance unit by way of preventing the damage on the current limiting impedance unit due to the fault current may result in facilitating protective coordination with other equipment.

The FCL disclosed herein may be allowed for application thereof according to capacity, by virtue of the configuration of detecting the fault current flowing to the current limiting impedance unit, measuring the heat capacity of the current limiting impedance unit, and limiting the fault current flowing to the current limiting impedance unit according to the heat capacity.

The FCL disclosed herein may have an expanded lifespan by virtue of the allowed application according to the capacity.

A FCL having an appropriate capacity can be easily designed by virtue of the allowed application of the FCL disclosed herein according to the capacity.