WO2000038292A1 - Dispositif electrique - Google Patents

Dispositif electrique Download PDF

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Publication number
WO2000038292A1
WO2000038292A1 PCT/SE1999/002430 SE9902430W WO0038292A1 WO 2000038292 A1 WO2000038292 A1 WO 2000038292A1 SE 9902430 W SE9902430 W SE 9902430W WO 0038292 A1 WO0038292 A1 WO 0038292A1
Authority
WO
WIPO (PCT)
Prior art keywords
current
protective device
fault
electric protective
current level
Prior art date
Application number
PCT/SE1999/002430
Other languages
English (en)
Inventor
Lars Liljestrand
Original Assignee
Abb Ab
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Abb Ab filed Critical Abb Ab
Priority to EP99965668A priority Critical patent/EP1149450A1/fr
Priority to AU21357/00A priority patent/AU2135700A/en
Priority to JP2000590269A priority patent/JP2002534043A/ja
Publication of WO2000038292A1 publication Critical patent/WO2000038292A1/fr

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Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
    • H02H3/02—Details
    • H02H3/025—Disconnection after limiting, e.g. when limiting is not sufficient or for facilitating disconnection
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H1/00—Details of emergency protective circuit arrangements
    • H02H1/04—Arrangements for preventing response to transient abnormal conditions, e.g. to lightning or to short duration over voltage or oscillations; Damping the influence of dc component by short circuits in ac networks

Definitions

  • the present invention relates in a first aspect to an electric protective de- vice of the kind specified in the preamble of claim 1.
  • the invention relates to an electric circuit as specified in the preamble of claim 9.
  • the invention relates to a method as specified in the preamble of claim 11.
  • the invention also relates to a use of the electric protective device as specified in the preamble of claim 17. The device and method thus concern protecting components from the effect of a fault current in an electrical power system. Such is the result of a short circuit in the system.
  • a consequence of a short circuit in an electrical power system is that the current increases from the nominal load current to a value given by the short cir- cuit impedance of the system and the impedance of the fault.
  • the short circuit current can reach levels of more than 100 times the nominal current.
  • the high short circuit current causes thermal and mechanical stress on the equipment upstream the fault. Therefore, short circuit currents have to be interrupted to reduce the stress and the damages.
  • Another consequence of the short circuit is that the voltage will drop in a large part of the power system until the fault is cleared.
  • a device of the kind specified in the preamble of claim 1 includes the features specified in the characterizing portion of this claim, in that an electric circuit as specified in the preamble of claim 9 includes the features specified in the characterizing portion of this claim, in that a method as specified in the preamble of claim 12 includes the measures specified in the characterizing portion of that claim, and by the use specified in claim 17.
  • the current thus is not immediately interrupted but only limited by the fault current limiter (FCL).
  • FCL fault current limiter
  • Limitation of the current takes place as soon as a tripp condition indicating the increased current level is met and this almost immediately, i.e. within 1 ms. Thereby, the electric equipment is immediately protected, but the current is not yet interrupted.
  • This offers a possibility to postpone the decision whether to interrupt the current or not until it is possible to determine if it is a fault current or a current transient load. Such a determination can be done after about 10 to 20 ms.
  • the current has passed through at least one half cycle and it is then easy to distinguish a fault current from other reasons for the increased current level. In the first case, the current is interrupted at that moment, otherwise not. Without limiting the current, a fault current would have destroyed the equipment before it would have been possible to evaluate whether it was a fault current or not.
  • FCL fault current limiters
  • Very high currents can be achieved when a short circuit occurs in a power system.
  • the amplitude of the current depends on the short circuit impedance of the system at the location of the fault and the type of fault (single line ground fault, 2-phase line-to-line fault or 3-phase fault).
  • a limited fault current has a constant amplitude.
  • the amount of energy dissipated by the FCL will also be much less as the FCL will limit the current during a short period only until stable conditions are reached. A FCL will not only limit the current, but also allow stable conditions to be resumed much faster.
  • the trip condition is the current level itself. Therefore, a reliable and simple way of activating the FCL is achieved.
  • the FCL is activated when the current reaches a level of 2 - 5 times the normal load current, preferably about 3 times.
  • the opening of the circuit breaker occurs as soon as possible after the current is limited.
  • the detection of the reason for the increased current therefore is made within 50 ms and preferably within 20 ms after activation of the FCL.
  • the FCL includes a variable resistor that can alternate quickly between a state of low and high resistance. Thanks to a resistor with the specified properties being included as an essential component in the FCL, the current can be greatly limited when the resistor is controlled to its state with very high resistance. Since this occurs very rapidly, the current can be limited before it causes damage to the electrical equipment connected. The increase of resistance also enables oscillations in the circuit to be quickly dampened.
  • a FCL of this type can also be made extremely small, simple and inexpensive, and without electric arcs.
  • the resistor is of a type having pressure-dependent resistance so that the resistance decreases with increasing pressure, and vice versa. With a resistor of this type, it is easy to rapidly alternate from the extreme states of the resistor. This therefore constitutes a preferred embodiment of the invention.
  • the pressure-dependent resistor is of a type comprising a powder where, in compressed state, the powder behaves as a homogenous conductor and in decompressed state has a large number of contact points and consequently high total resistance.
  • a powder-based variable resistor is described in PCT/SE 98/00679, the content of which hereby is incorpo- rated in this application by reference.
  • the resistor used in the present application is suitably of the type described in said PCT-application.
  • the device includes means for resetting the FCL after the detection of a increased current level.
  • the FCL is reset irrespective of the detected increased level being due to a fault current or an inrush current.
  • the circuit breaker is arranged to be closed again after its opening and after resetting the FCL.
  • Figure 1 is a schematic representation of the principle of the invention
  • Figure 2 is a graph illustrating fault current and inrush current without current limitation
  • Figure 3 is a graph similar to that of fig. 2, but with current limitation
  • Figure 4 is a schematic illustration of a power network illustrating when short circuit occurs
  • Figure 5 is a graph illustrating the current as a function of time when the invention is applied to the network of fig. 4
  • Figure 6 is a similar graph, but without current limitation
  • Figure 7 is a schematic illustration of the power network of fig. 4 illustrating energizing of a transformer
  • Figure 8 is a graph similar to that of fig. 5 when the invention is applied to the network of fig. 7
  • Figure 9 is a similar graph, but without current limitation
  • Figure 10 shows schematically a resistor in compressed state according to an embodiment of the invention
  • Figure 1 1 shows schematically the resistor of fig. 10 in expanded state.
  • Block 104 represents measuring one or more parameters directly or indirectly indicating a high current. This might be the current level itself, the voltage 5 level or some other parameter or combination of parameters. If it is detected in block 104 that the trip condition is met, e.g. that the current level is more than three times the normal current level, the FCL 101 is activated to limit the current. The detection of whether the trip condition is met and the activating of the FCL is performed very rapidly, within less than one ms. Therethrough, the current is lim- l ⁇ ited before the increased current causes any damage to the electric equipment downstream the protective device. This gives time to analyse whether the increased current is a fault current or not.
  • Block 102 represents detecting means to evaluate if the increased current is a fault current or a transient load current. Since the current now is limited, it is
  • Figure 3 is a graph correspondingly illustrating the currents when current limitation is applied, where F 2 is a fault current and T 2 is an inrush current.
  • the activation of the current limiter is arranged to occur at about 3kA in the example 0 shown.
  • the fault current can be clearly distinguished from the inrush current already during the first cycle after limiting the current, i.e. within 20 ms
  • Figure 4 is a sche- 5 matic diagram of a part of an electric network to which the invention is applied
  • branch 15 of the network three electrical components 1 1 , 12, 13 are illustrated, of which 12 is a transformer and 13 a motor
  • 12 is a transformer and 13 a motor
  • a short circuit is represented
  • a protective device 10 according to the invention is provided
  • Figure 5 illustrates the situation in Figure 4 At point A, an increase in the current exceeding trip condition is detected Almost immediately (within 1 ms), the current is limited At point B, occurring one cycle later, the increased current is identified as a fault current, and at point C, another 30 ms later, the current is interrupted
  • Figure 6 illustrates what would have happened, if the protective device 10 had not been present, i e when using the technique of directly interrupting the current as soon as a fault current is identified
  • the very high current due to the short circuit would last during the time it takes to identify a fault current and the time required to activate the CB As shown in the figure, this time from A' to C 0 adds up to more than two cycles, maybe even three cycles
  • Figure 7 illustrates the same network as in fig 5 in a situation when the transformer 12 is to be energized by closing the contact 16 No short circuit is at hand
  • Figure 8 is a diagram similar to that of fig 5 illustrating the course of ac- 5 tion during the energizing of the transformer As soon as the circuit breaker 16 is closed, the energizing current increases the current level above trip level, which is detected at A" and the current is limited accordingly At point B", one cycle later, it is detected that the current is not a fault current Therefore, the current limited is reset and the power supply continues without interruption 0
  • Figure 9 illustrates the situation shown in fig 7, but without current limitation As shown, the main difference is that with current limitation (fig 8), the cur- rent is limited for about one half-cycle, which is an advantage, since the transformer reaches steady state faster
  • Figures 10 and 1 1 illustrate the principle of a variable resistor according to one embodiment of the invention
  • Figure 10 shows the resistor in a position with very low resistance and in Figure 1 1 , the resistance is very high
  • the device can easily be described as a container 1 of non-conducting material, having a wall 2, 3 of conducting material at each end, each of the end walls 2, 3 being connected to a conductor 4, 5
  • a powder e g T1B2
  • the end wall 3 is displaceable laterally in the figure and is in a position in
  • the powder 6 is firmly compressed so that it acquires electric properties similar to those for equivalent material in solid form
  • the powder will therefore constitute a good conductor with a resistivity in the vicinity of m ⁇ cm
  • the compression force is a few MPa
  • the displacement of the movable end wall 3 from the position shown in Figure 10 to that shown in Figure 1 1 takes place in approximately 100 ⁇ s and the increase in volume is approximately 20%
  • the negative pressure wave caused by the rapid increase in volume together with the inherent spring force in the powder particles caused by the increase in volume results in the powder particles spreading through the available space so that the loosened state ensues
  • the invention is not limited to the use of the described technique for current limiting.
  • Other operation principles for the FCL such as mechanical switches with arc-chambers, LC-resonance limiters, semiconductor limiters, increasing impedance fuses and superconductors fall within the scope of the present invention.

Landscapes

  • Emergency Protection Circuit Devices (AREA)
  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Keying Circuit Devices (AREA)

Abstract

L'invention concerne un dispositif de protection électrique qui comprend un limiteur de courant (101). Ce limiteur de courant est agencé pour être activé si un niveau prédéterminé de courant supérieur au niveau normal est atteint. Selon cette invention, des moyens de détection (102) détectent si l'augmentation du niveau de courant est un courant de défaut ou une variation de charge transitoire, et un disjoncteur (103) est agencé de façon à se déclencher s'il s'agit d'un courant de défaut, et à ne pas interférer dans un autre cas. Cette invention concerne aussi un procédé correspondant, un circuit ajouté au dispositif et une utilisation dudit dispositif.
PCT/SE1999/002430 1998-12-22 1999-12-20 Dispositif electrique WO2000038292A1 (fr)

Priority Applications (3)

Application Number Priority Date Filing Date Title
EP99965668A EP1149450A1 (fr) 1998-12-22 1999-12-20 Dispositif electrique
AU21357/00A AU2135700A (en) 1998-12-22 1999-12-20 An electric device
JP2000590269A JP2002534043A (ja) 1998-12-22 1999-12-20 電気装置

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE9804496A SE9804496L (sv) 1998-12-22 1998-12-22 Elektrisk skyddsanordning
SE9804496-9 1998-12-22

Publications (1)

Publication Number Publication Date
WO2000038292A1 true WO2000038292A1 (fr) 2000-06-29

Family

ID=20413818

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/SE1999/002430 WO2000038292A1 (fr) 1998-12-22 1999-12-20 Dispositif electrique

Country Status (5)

Country Link
EP (1) EP1149450A1 (fr)
JP (1) JP2002534043A (fr)
AU (1) AU2135700A (fr)
SE (2) SE9804496L (fr)
WO (1) WO2000038292A1 (fr)

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4236186A (en) * 1979-01-17 1980-11-25 Mitsubishi Denki Kabushiki Kaisha Power breaker system
EP0074186A1 (fr) * 1981-08-13 1983-03-16 Mitsubishi Denki Kabushiki Kaisha Dispositif limiteur de courant
WO1998049694A2 (fr) * 1997-04-14 1998-11-05 Abb Ab Resistance electrique variable

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4236186A (en) * 1979-01-17 1980-11-25 Mitsubishi Denki Kabushiki Kaisha Power breaker system
EP0074186A1 (fr) * 1981-08-13 1983-03-16 Mitsubishi Denki Kabushiki Kaisha Dispositif limiteur de courant
WO1998049694A2 (fr) * 1997-04-14 1998-11-05 Abb Ab Resistance electrique variable

Also Published As

Publication number Publication date
EP1149450A1 (fr) 2001-10-31
SE9804496L (sv) 2000-06-23
JP2002534043A (ja) 2002-10-08
AU2135700A (en) 2000-07-12
SE9804496D0 (sv) 1998-12-22
SE516373C2 (en) 2002-01-08

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