EP0923800A1 - Eclateurs et transformateurs de protection de surtension - Google Patents

Eclateurs et transformateurs de protection de surtension

Info

Publication number
EP0923800A1
EP0923800A1 EP97937349A EP97937349A EP0923800A1 EP 0923800 A1 EP0923800 A1 EP 0923800A1 EP 97937349 A EP97937349 A EP 97937349A EP 97937349 A EP97937349 A EP 97937349A EP 0923800 A1 EP0923800 A1 EP 0923800A1
Authority
EP
European Patent Office
Prior art keywords
voltage
transformer
spark gap
spark
arc
Prior art date
Legal status (The legal status 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 status listed.)
Withdrawn
Application number
EP97937349A
Other languages
German (de)
English (en)
Inventor
Christopher John Kossmann
John Richard Gumley
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Erico Lightning Technologies Pty Ltd
Original Assignee
Erico Lightning Technologies Pty Ltd
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
Priority claimed from AUPO2117A external-priority patent/AUPO211796A0/en
Priority claimed from AUPO5532A external-priority patent/AUPO553297A0/en
Application filed by Erico Lightning Technologies Pty Ltd filed Critical Erico Lightning Technologies Pty Ltd
Publication of EP0923800A1 publication Critical patent/EP0923800A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01T—SPARK GAPS; OVERVOLTAGE ARRESTERS USING SPARK GAPS; SPARKING PLUGS; CORONA DEVICES; GENERATING IONS TO BE INTRODUCED INTO NON-ENCLOSED GASES
    • H01T4/00—Overvoltage arresters using spark gaps
    • H01T4/08—Overvoltage arresters using spark gaps structurally associated with protected apparatus
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F19/00—Fixed transformers or mutual inductances of the signal type
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F38/00—Adaptations of transformers or inductances for specific applications or functions
    • H01F2038/006—Adaptations of transformers or inductances for specific applications or functions matrix transformer consisting of several interconnected individual transformers working as a whole

Definitions

  • the present invention relates to the technology of igniting spark gaps, particularly lightning arresters.
  • the present invention also relates to lightning protection and transient protection.
  • the present invention has many applications, such as electrical transmission lines, electrical supplies and sources, and telecommunications.
  • Known transient protectors for controlling switching and lightning induced transients comprise spark gaps which are commonly called voltage switching devices and metal oxide varistors (mov) which are known for their voltage clamping function. There are also solid state devices which fall into those categories but these are mostly incapable of economically handling high energy transients. Each of these devices have technical advantages and disadvantages.
  • the spark gap can handle very high currents as the initial switch-on voltage of the arc is a low 50V. However, when these devices are placed across a power line, the low arc voltage will cause a follow current to flow after the transient has passed. Thus, in simple terms, there is a problem associated with turning off the arc, once the transient has passed. These currents can only be restricted at the next power zero crossing.
  • a further disadvantage of the spark gap is that they require a relatively high spark over voltage. Values are typically 3.5kV which is a high level for protecting a 240Vac circuit.
  • the spark gap may have a mov placed in series which will act to add voltage to that of the arc. The combined voltage then becomes sufficient to limit the power follow current.
  • the disadvantage of this arrangement is that the mov becomes the limiting device as far as power handling capability is concerned.
  • movs may be used without a spark gap.
  • 275V on a 240Vac circuit they will have no follow current and can enter conduction at around 450V with voltage rising as the transient current increases.
  • Devices designed to protect 240Vac circuits would typically rise to values of 1500V as they near their energy absorption limit. Further, the mov suffers degradation with each high energy pulse and so has a finite lifetime.
  • this spark gap trigger mechanism is disclosed in copending PCT application No. PCT/AU95/00768, as noted above.
  • the aim of this mechanism is to produce an additive voltage in series with the gap when a transient exceeds a preset value. This is performed by a step up transformer.
  • the present invention can be considered an improvement to the invention disclosed in PCT/AU95/00768. Normally, such an additive voltage technique would not be considered by those skilled in the art, since the transformer winding in series with the gap would be subject to the entire transient current flow once conduction commences. The inductance of this winding plus the high dl/dt of typical transients would mean that some thousands of volts would be added to the arc voltage. This would totally negate any perceived advantage in causing the gap to trigger at a low voltage.
  • One aspect of the present invention is directed to a transformer of special construction adapted to produce an additive voltage.
  • This aspect of the present invention is based on using a matrix transformer for the triggering of spark gaps.
  • Matrix transformers have theretofore been used in power supply design, but in such designs, the matrix transformer is not used in a saturated mode.
  • the inductance can be further reduced by utilisation of at least partial cancellation of magnetic fields.
  • This aspect may be provided in the form that the secondary conductor of the matrix transformer is folded back on itself so that, in the saturated mode, the magnetic linkage between the forward and reverse section will act to further reduce the inductance.
  • a new electrode for sparkgaps comprising at least two frustro conical sections mutually opposed, and being spaced by an insulative material, the sections having a hollow therethrough, into which a conductor can be placed.
  • circular magnets are provided in an annular form of a 'ring' located at ends of the sections away from the insulative material. The overall effect is to continually move the arc to cold metal on the electrodes to minimise burning, and to lengthen the arc by slewing it from the vertical. The lengthening of the arc acts to increase the voltage of the arc and to reduce the level of follow current. Also, since the arc is not constrained within a conductor, it will be motivated to move outward in a radial direction.
  • Figure 1 illustrates a 4:1 step up transformer
  • Figure 2a illustrates a 6:1 step up transformer
  • Figure 2b illustrates the proximity of the return wire to the core section
  • Figure 3a illustrates a basic triggering device
  • Figure 3b illustrates a a 8:1 step up transformer sidactor triggering with straight wire in series with the spark gap
  • Figure 4 illustrates a step up transformer in loop back system to further reduce inductance
  • Figure 5 illustrates a 8:1 step up transformer in loop back system using E-l cores
  • Figure 6 illustrates a gas arrester triggering with two series connected spark gaps used to reduce follow current
  • Figure 7 illustrates a resistor biasing of capacitive divider
  • FIG. 8 illustrates an alternative capacitive element arrangement
  • Figure 9 illustrates an isolation between the primary and secondary trigger transformer
  • Figure 10 illustrates a 12:1 transformer with two "U" sections
  • FIG. 11 illustrates a new electrode
  • Figures 12a, 12b and 12c illustrate magnetic fields and arc movement around the electrode
  • Figures 13a and 13 b illustrate a second magnetic effect
  • Figures 14a and 14b illustrate an alternative electrode construction
  • Figure 15 illustrates an example application of the aspects disclosed.
  • Normal transformer windings even when the core is magnetically saturated, are wound one upon another and so reinforce each other in a manner to produce a high residual inductance. Values of the order of 4 microhenries are typical.
  • One improvement over conventional winding is to use a toroidal core. When this core saturates, the windings do not directly complement each other in order to increase inductance. Each turn produces a north and south pole along a line which is at right angles to the winding direction. Since the windings continually change direction around the 360 degrees of the toroidal core, the additive effects due to normal winding are reduced. Typical values would be 0.5 microhenries.
  • the matrix transformer of this invention has the advantage of zero complete turns. The winding is actually a straight piece of wire as shown in Figure 1. When the secondary is folded back as in Figure 4, typical values of inductance under core saturation reduce to 0.15 microhenries.
  • the secondary may be made up of more than one turn to achieve larger output voltage as shown in Figures 2a and 2b, but there will also be an increase in the saturated core inductance.
  • normal transformers achieve a voltage increase by using a single core and a suitable turns ratio.
  • the principle noted above is applied by using a number of individual transformers of preferably 1 :1 ratio which are parallel connected in the primary and series connected in the secondary.
  • the step up ratio is determined by the number of transformers.
  • the cores of the transformers are ferrite.
  • the disadvantages of the spark gap are alleviated and triggering voltage becomes controlled at a relatively low value, typically in the range of 500-600V for a 240Vac circuit.
  • the follow current becomes controlled and a long lifetime is assured.
  • the need to decouple downstream devices is substantially eliminated, as the residual voltage from the invention leaves only a few amperes to flow in the direction of the equipment.
  • a further advantage is that the low residual currents have insufficient energy to induce significant voltages into adjacent cables.
  • Figure 1 shows a preferred arrangement of the present invention.
  • Conventional practice is to wind a transformer on a single core and to increase 5a voltage by setting an appropriate turns ratio.
  • multiple cores are used with their primaries being parallel connected to the trigger source.
  • Figure 1 shows how a 4:1 step up transformer can be achieved using this technology.
  • Each primary winding can be a single turn, while the secondary is a straight piece of wire passing through each core. As the secondary wire passes through each core, a voltage is added in the same manner that would occur with an in
  • the secondary winding may be a straight piece of wire which, over a distance of approximately 100mm, can have an induced voltage exceeding 4kV.
  • the parameters of the core material are then selected to allow them to saturate at very low flow currents in the secondary, typically 1-2 amps.
  • the ability of a straight piece of wire in the secondary of a multiple core transformer matrix to be able to develop very high voltages, and then, to have the cores saturate with low levels of subsequent current flow is not immediately obvious.
  • the benefit is a reduction in inductance to values as low as 50-150 nanoHenries, depending on the number of cores required, the number of turns for the specific application, and the consequential length of wire used.
  • Figure 3b shows an example of a triggering device in which a pulse is created at a transient level of approximately 500V.
  • the straight wire secondary builds up to approximately 4000V, while the winding inductance in the saturated mode will reduce to approximately 200 nanoHenries.
  • Other arrangements where the present invention is equally applicable are shown in PCT/AU95/00768.
  • the gas arrester fires at a voltage determined by the transient level and the capacitance ratio of the two capacitors. The energy of the capacitor is then dumped into all primary windings with their parallel connection arrangement.
  • the transformer secondary can be made of heavy cable or flat strip in order to carry the full impulse of the spark gap. This could be a 100kA x 8/20 usec impulse. In a practical situation, some 4kV can be added to the line transient of say 500V to make an impressed voltage on the gap of 4.5kV. This incremental voltage can be achieved in the order of 50 nanoseconds. Conversely, the winding inductance of the secondary can be reduced to as little as 150 nanohenries in the saturated core mode. The overall effect is that a 20kA impulse with a 10 microsecond rise time with dl/dt of 2kA/usec can be impressed across 0.15 microhenries.
  • E-E or E-l shaped magnetic material By combining two adjacent toroids, E-E or E-l shaped magnetic material can be used.
  • the circuit of Figure 4 can be reproduced with just four E cores as shown in Figure 5. In this arrangement, each E core now provides a 2:1 step up voltage.
  • Figure 6 is another variation where two spark gaps are used in series so 8
  • the voltage increment supplied by this invention is placed in series with the centre junction of the two spark gaps. Because of the series nature of the key components, the invention will work equally well if the trigger transformer secondary winding is placed between line and spark gaps, or between spark gaps and ground.
  • the capacitive divider of Figure 6 sets the firing voltage of the gas arrester.
  • the two capacitors in series also serve to provide the necessary pulse current required in the primary of the trigger transformer to magnetise the core.
  • Optional biasing resistors may be added across each or both of these capacitors as shown in Figure 7. The resistor function to bias the capacitor voltage, and also bleed any voltage across these capacitors when the voltage is disconnected. This biasing may or may not have frequency dependence. If the ratio of R1/R2 - C2/C1 is used, the biasing resistors and capacitors will create a frequency independent division of the mains voltage. Typically, the values of these resistors would be greater than 100 kiloohms to limit resistor power dissipation when operating at mains voltage.
  • a further arrangement of the capacitive elements involves the trigger transformer arrangement of Figure 8.
  • the capacitor C1 provides the energy for the trigger to switch through the transformer primaries.
  • This circuit may have some or all of the optional resistors across the capacitors for biasing.
  • the resistor R2 may be added. This acts to make the trigger circuit frequency dependent. At low sinusoidal mains type frequencies, values for the resistors and capacitors are chosen such that the voltage between point "P" and "Q" is too low to trigger the gas arrester. As this frequency is increased, the impedance of capacitor C2 reduces, however the resistor impedance does not. The net effect if that the voltage of point "P" increases. The intention of this frequency dependent trigger is to have a lower gas arrester firing voltage to fast transients than to slow mains frequency voltage waveforms.
  • this device in combination with a spark gap is protecting between a line voltage and earth, then there will be an issue of earth leakage current to consider.
  • the capacitive divider will only draw miiliamps of current from the mains if there is no triggering.
  • An alternative arrangement can be used to prevent the capacitive current flowing into the earth line if the secondary of the trigger transformer is isolated from the primary. A typical application for this is given in Figure 10.
  • the capacitive divider is driven between the line to neutral. If a transient exists between line to neutral, the trigger circuit will operate the spark gap and the surge current will be passed from active line to earth.
  • the improvement over the prior art is beneficial because it produces a faster triggering pulse, from a smaller package with significantly lower saturated inductance.
  • spark gaps When spark gaps are designed for only random operation such as would occur with lightning events, their operation frequency may be several times per year. With this invention, operation is caused at a lower incident voltage such as would occur with switching impulse generated within a building. These may occur several times per day and increase the operating duty several hundred times that for lightning. Spark gap life time then becomes an important criteria as electrode burning may significantly alter performance criteria.
  • the use of the trigger transformer of this invention allows a controlled high voltage to be placed in series with the gap while the impressed transient is at a low voltage. This allows the primary design parameters of current spark gaps to be improved. For example, the current initial spark gap may be increased from 1 mm to 2mm, and result in the doubling of the initial arc voltage. This will minimise the initial magnitude of the power follow current.
  • the initial gap can be extended in length by designing the trigger transformer to have a high output voltage.
  • FIG. 11 shows how two truncated conical elements are separated by an insulating medium. A permanent magnet is shown at 1 and 4, insulation is shown at 2 and conductive cones are shown at 3. The insulation is designed to make the initial arc track along the insulator surface.
  • Figure 12a shows the magnetic field when two gaps are connected in series. Each insulation is made in the form of a curve as shown in Figure 12b. This will make the arc move out horizontally on the upper surface, then down and return on the lower surface.
  • Numeral 8 illustrates current flow around the insulator. Since both horizontal sections are in the same magnetic field, the upper section will move in one direction 6 and the lower section will move the opposite direction 7 according to Figure 12c.
  • Numeral 5 indicates that the arc is vertical at initiation.
  • the second magnetic effect is shown in Figure 13a. It is achieved by passing the conductor for the lower electrode vertically down through the center of the cones. Numeral 9 shows the conductor in cone electrode. Numeral 10 shows return current in arc. The magnetic effect of the downward conductor current flowing to the lower electrode will then act upon the magnetic effect of the upward return current in the arc. Thus, the arc will be slewed by the permanent magnet and radially expanded at a rate dependent on the magnitude of the arc current as illustrated in figure 13b. Numeral 11 shows arc movement. This is an electromagnetic effect.
  • FIG. 14a an improved electrode is shown which is particularly suited to the advantages of the incremental voltage triggering made possible by this 10a invention.
  • Permanent magnets are shown at 12, insulators at 13 and conductive cones at 14.
  • the arcs within multiple gaps may be both rotated and forced to extend their arc length to reduce follow current and to assist the extinction process as illustrated in 14b.
  • Numeral 15 illustrates the magnetic force.
  • the current path again is made to form a "U" by passing an insulated wire conductor down through the center of the truncated conical sections forming the electrodes. When the arc is triggered by the transformer, it is in the reverse arm of the "U".
  • the arc is triggered by the transformer, it is in the reverse arm of the "U".
  • spark gap technology has not been realised in any prior art, since the design criteria was always to minimise the length of the initial gap and to achieve the lowest spark over voltage.
  • the innovative aspects of the trigger transformer leads to a consequential improvement in spark gap technology.
  • the technology of this invention may use a single gap for the lower line voltages such as 115Vac.
  • a further improvement may be obtained by placing two such gaps of this concept in series. Once the combined voltage of the gaps exceeds the instantaneous value of the power supply voltage, the arc will extinguish. Conduction of any follow currents may be restricted to values of 1 millisecond or less, and will be incapable of tripping a circuit breaker.
  • the invention enables use of an insulating piece with a physical magnitude determined by the available trigger transformer voltage, and a double magnetic effect by combining permanent and electromagnetic fields to both slew the initial arc and to extend it radially.
  • the arc voltage is increased to reduce follow current and the arc extinguishes earlier. It cannot be maintained if the arc voltage exceeds that of the power supply.
  • Figure 14 shows a schematic of the invention in use. Where the circuit is used with equipment designed to operate at 240V, the diodes may be designed 12
  • the final advantage lies with the parameters of downstream filters. Normally filters are tested with a waveform of 8/20 microsecond. However, these are not representative of the surges found in nature where tail lengths of some 100's of microseconds exist.
  • the residual transient of this invention exists only in the period before transformer core saturation, a time of approximately 100 nanoseconds. This time period is relatively constant and essentially independent the waveform of the impressed transient. Because of this very short time and the prior clamping, the inclusion of a simple L/C filter will further reduce the residual voltage and will complete the overall design.

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

Abstract

Cette invention, qui a trait aux techniques des éclateurs d'allumage, notamment aux déchargeurs de foudre, concerne également la protection contre la foudre et les transitoires. Les applications de cette invention sont nombreuses, notamment dans les domaines des lignes de transport d'énergie électrique, des accessoires électriques, des sources de courant et des télécommunications. L'un des aspects de l'invention porte sur l'utilisation de transformateurs matriciels aux fins du déclenchement des éclateurs. Dans un autre mode de réalisation, le conducteur secondaire du transformateur matriciel est replié sur lui-même de sorte que, en mode de saturation, le couplage magnétique existant entre les parties antérieure et postérieure contribue à réduire encore l'inductance. Un autre aspect de cette invention a trait à une électrode d'éclateur, comprenant au moins deux parties tronconiques à l'opposé l'une de l'autre et séparées par une substance isolante, ces parties étant pourvues d'un trou traversant à l'intérieur duquel il est possible de placer un conducteur.
EP97937349A 1996-09-04 1997-09-03 Eclateurs et transformateurs de protection de surtension Withdrawn EP0923800A1 (fr)

Applications Claiming Priority (5)

Application Number Priority Date Filing Date Title
AUPO211796 1996-09-04
AUPO2117A AUPO211796A0 (en) 1996-09-04 1996-09-04 An improvement in the triggering of spark gaps for the control of overvoltage transients
AUPO553297 1997-03-07
AUPO5532A AUPO553297A0 (en) 1997-03-07 1997-03-07 Improvements in transient and overvoltage protection by application of an incremental triggering to a two element spark gap
PCT/AU1997/000567 WO1998010498A1 (fr) 1996-09-04 1997-09-03 Eclateurs et transformateurs de protection de surtension

Publications (1)

Publication Number Publication Date
EP0923800A1 true EP0923800A1 (fr) 1999-06-23

Family

ID=25645257

Family Applications (1)

Application Number Title Priority Date Filing Date
EP97937349A Withdrawn EP0923800A1 (fr) 1996-09-04 1997-09-03 Eclateurs et transformateurs de protection de surtension

Country Status (2)

Country Link
EP (1) EP0923800A1 (fr)
WO (1) WO1998010498A1 (fr)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE10231431B4 (de) * 2002-07-11 2014-03-20 Dehn + Söhne Gmbh + Co. Kg Gekapselter, druckfester Überspannungsableiter mit einer Funkenstrecke
ZA200803120B (en) * 2005-09-14 2010-10-27 Univ Witwatersrand Jhb Spark gap protection device
CN110808149B (zh) * 2019-10-11 2022-02-22 西安交通大学 一种低漏感的多级多原边多副边脉冲变压器及其绕制方法

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Publication number Priority date Publication date Assignee Title
US3154718A (en) * 1962-03-16 1964-10-27 Joslyn Mfg & Supply Co Secondary lightning arrester with arc spinning means
US3626237A (en) * 1968-12-12 1971-12-07 Gen Signal Corp Line electrical surge arrestor
DE2627648C2 (de) * 1976-06-19 1982-05-19 Dehn + Söhne GmbH + Co KG, 8500 Nürnberg Funkenstrecke
US4112330A (en) * 1977-05-20 1978-09-05 General Motors Corporation Metallized glass seal resistor compositions and resistor spark plugs
US4187524A (en) * 1978-02-10 1980-02-05 Westinghouse Electric Corp. Series capacitor protection equpment with extended range dual sparkover feature
DE3016265C2 (de) * 1980-04-26 1984-05-17 ANT Nachrichtentechnik GmbH, 7150 Backnang Überspannungsableiter mit Funkenstrecke
US4486805A (en) * 1983-03-07 1984-12-04 Dayton-Granger, Inc. Lightning arrester with improved spark gap structure
US4665357A (en) * 1984-04-23 1987-05-12 Edward Herbert Flat matrix transformer
WO1991017556A1 (fr) * 1990-05-04 1991-11-14 Fmtt, Inc. Structures a noyaux magnetiques pour transformateurs matriciels et inducteurs matriciels
AU714162B2 (en) * 1994-11-29 1999-12-23 Erico Lightning Technologies Pty Ltd Ignition apparatus and method

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Also Published As

Publication number Publication date
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