WO2018192873A1 - Circuit électrique à sécurité intrinsèque à blindage contre les interférences à sécurité intrinsèque - Google Patents

Circuit électrique à sécurité intrinsèque à blindage contre les interférences à sécurité intrinsèque Download PDF

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Publication number
WO2018192873A1
WO2018192873A1 PCT/EP2018/059664 EP2018059664W WO2018192873A1 WO 2018192873 A1 WO2018192873 A1 WO 2018192873A1 EP 2018059664 W EP2018059664 W EP 2018059664W WO 2018192873 A1 WO2018192873 A1 WO 2018192873A1
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WO
WIPO (PCT)
Prior art keywords
shield
intrinsically safe
electrical circuit
ground
resistor
Prior art date
Application number
PCT/EP2018/059664
Other languages
English (en)
Inventor
Renato Kitchener
Gunther Rogoll
Original Assignee
Pepperl+Fuchs Gmbh
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 GBGB1706266.2A external-priority patent/GB201706266D0/en
Priority claimed from GBGB1712714.3A external-priority patent/GB201712714D0/en
Application filed by Pepperl+Fuchs Gmbh filed Critical Pepperl+Fuchs Gmbh
Publication of WO2018192873A1 publication Critical patent/WO2018192873A1/fr

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Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
    • H02H9/008—Intrinsically safe circuits

Definitions

  • the present invention relates to an intrinsically safe electrical circuit with an intrinsically safe interference shield, for use particularly, but not exclusively, as a digital data communications and control circuit for use in an intrinsically safe environment.
  • HMI Machine Interface
  • PLC programmable logic controllers
  • Ethernet non-time critical communications system
  • RTM Fieldbus
  • the various components of the system communicate with one another using a communications protocol, for example a Manchester encoding system.
  • Data telegrams are transmitted either on dedicated communications circuits, or on the same electrical circuits as the power to drive the field instruments.
  • the data telegrams serve to control and to monitor and diagnose the field instruments in use.
  • a typical combined two wire electrical power and communications circuit there is a power supply, an intrinsic safety barrier of some kind, a trunk section leading out into the field along a cable, and a number of device couplers with separate spurs connected thereto, on which the field instruments are mounted.
  • the trunk and the spurs together form the segment.
  • the intrinsic safety barrier divides the circuit into an intrinsically safe side and a non-intrinsically safe side.
  • the power supply, the PLCs and other systems like physical layer diagnostic modules which measure physical layer attributes of the electrical circuit and the network hardware, and in part the physical software or protocol being used, are located in the non-intrinsically safe side of the circuit, usually in a control room.
  • the trunk, the device couplers, the spurs and the field instruments are located in the intrinsically safe side, out in the field.
  • Intrinsic safety can be achieved in a number of known ways, from simply limiting the power so open or short circuits cannot form combustible arcs, to using active monitoring and isolating systems which allow higher power levels and act to isolate the power supply from open or short circuits to prevent combustible arcs.
  • any given circuit or combination of circuit faults must not feed a fault with more than 40uJ of energy in a gas group IIC environment. This can be less if a safety factor is applied. This limit equates to approximately 1 .x watts unless it is time restricted.
  • the shield In order to do this they are constructed from electrically conductive metals which are grounded at at least one end. As such the shield has parasitic inductance which absorbs any interference. The longer the shield, the greater the inductance. Therefore, it is preferable to ground the shield at both ends, and if possible, at multiple points along its length, and to provide an equipotential bonding (EB) system to equalize the potential between the groundings. The more grounding points used, the better the shield's ability to reject common mode noise or close coupled noise.
  • EB equipotential bonding
  • the preferred way to ground each shield is to segregate it at each junction box in a segment, or at each interposing device, at say, every 100 metres, and then treat each section as an individual cable, with its own grounding at each end.
  • the shield is not powered because there is no power or energy source connected to it. Therefore in existing systems it is not energy restricted either, as there is no apparent need. This is despite the fact that the shield is like an outer core providing mechanical protection for the powered cores inside it, and is therefore actually more prone to suffering mechanical damage. This is not considered an issue though because any fault to ground or earth of the shield is thought of as non- incendive, because it is supposed to be at the same potential to ground or earth due to the EB system.
  • the shield can be connected to ground at only one point, and be cut back and insulated at the ungrounded end, and/or the shield can be capacitively grounded with no more than 10nF.
  • the integrity of the capacitor should meet the IEC60079 part 1 1 standard, and they generally don't. Also, this does not address the issue of an exposed shield touching any grounded metal structure and still creating an incendive situation. This is particularly so when the cable is considered to be intrinsically safe and no additional mechanical protection or acre is provided.
  • the shield is a cable, and there is a cable specification for a current carrying wire, which is the permissible Lo/Ro calculation, in accordance with the IEC60079 part 1 1 standard. It is
  • the present invention is intended to address some of the above issues.
  • an intrinsically safe electrical circuit comprises a power supply, a load and a cable connecting said power supply and said load and comprising positive and negative cores, in which said circuit comprises an incendive arc prevention mechanism which passively and/or actively limits the power in said positive and negative cores to render them intrinsically safe, in which said cable comprises an electrically conductive interference shield surrounding said positive and negative cores along the length of the cable, and in which said shield is rendered intrinsically safe by being connected to ground at at least a first end thereof via a power limiting resistor.
  • the invention involves power limiting the shield with a resistor to render it intrinsically safe. As discussed above this is not something which has ever been done before because intrinsic safety is not something which would be considered for an unpowered physical component.
  • This invention sets out to change the existing approach to the shield, and to now treat it as an intrinsically safe circuit as such, as opposed to a non-intrinsically safe 'wire' with no potential or energy source.
  • an intrinsically safe circuit as such, as opposed to a non-intrinsically safe 'wire' with no potential or energy source.
  • the shield must also still carry out its original function of protecting the powered communications cores from EMC and RFI interference.
  • the shield can be connected to ground at the first end via a capacitor mounted in parallel with the power limiting resistor. This allows the shield to maintain its original function.
  • the shield In order to operate correctly the shield must also be free from ground loops, or loops that could damage the shield and/or the cable, or in the worst case set up enough stored energy in its natural inductance to cause ignition at a given voltage. At the same time it is preferable for the shield not to float to 'any DC potential', although this is the case for the intrinsically safe cores because they are galvanically isolated. All these requirements are addressed by connecting the shield to ground at at least its first end via a suitably sized power limiting resistor, as set out above. This provides an effective output/input resistance (Ro), which in turn is connected to ground.
  • Ro output/input resistance
  • One possible fault scenario is a connection of the shield to one of the intrinsically safe cores. However, this is generally at a voltage of less than 50V, so the requirements for the shield are less arduous.
  • the L/R ratio must be take into account, as must the length of the shield, and this must be factored into the parameter specification for the resistor.
  • the IEC60079 standard allows at part 14 for both ends of a shield to be grounded. However, this would only apply when the groundings are made to an EB that is controlled and maintained, so both ends of the shield are at zero volts. However, this is ambiguous because under fault conditions an EB has some potential across it because current is flowing. This potential is obviously unknown, but in practice it could be anything from a few millivolts up to a few volts. This would be incendive for a directly connected shield, in accordance with the standard's assessment in part 1 1 .
  • Figure 4 illustrates the calculations and assessment for various lengths of cable, with various potential differences applied.
  • the cable is copper braided and has a resistance of 13.6 Ohms/km and an inductance of I mH/km.
  • Figure 3 is based on there being a source resistance of the EB of 0.1 Ohms
  • Graphs 1 , 2, 3, 4 and 5 relate to EB potential differences of 4V, 2V, 1 .5V, 1V and 0.5V respectively.
  • the Lo/Ro ratio calculations as per the IEC60079 part 1 1 standard are above the required limit. Anything above the 40uJ limit has to be considered to have incendive potential, if a resulting arc is sustained for more than 10ms.
  • the stored energy each time is above the incendive 40uJ limit for gas group classification IIC. As such, these examples would fail the assessment for distributed cable inductance and for lumped inductance.
  • the potential difference across an EB system may only be high under fault conditions which have a low probability of occurring, but this is still not satisfactory for Zone 0 installation. For example, it's not permitted to terminate a 230VAC cable with no energy limiting means in place in a Zone 0 environment. As such, if the shield is going to be intrinsically safe it cannot be treated differently to this.
  • the shield is normally grounded at the device, which may be in zone 0, and if the other end of the cable is floating, then connection and
  • X/1 .5 will be the voltage used to size the safety components to include a safety factor.
  • an additional resistor can be mounted in series between the shield and the capacitor. This allows for the capacitance of the capacitor to be higher, which might be desired in certain instances.
  • the shield can be grounded at both ends. Therefore, preferably the shield can also be connected to ground at a second end thereof via a second power limiting resistor. This increases the ability of the shield to deal with two fault scenarios. For example, if the shield is cut in two, the two remaining parts will each be grounded via a resistor at one end. Therefore, if a further fault occurs on one or on both remaining parts it can be contained.
  • grounding the shield at both ends improves its ability to perform its primary function of protecting communications cores inside it from the effects of external interference such as RFI and EMC.
  • the shield has parasitic inductance which absorbs any interference. The longer the shield, the greater the inductance. Therefore, it is preferable to ground the shield at both ends, and if possible, at multiple points along its length, because the more grounding points used the better the shield's ability to reject common mode noise or close coupled noise.
  • the second end of the shield can have the same components as the first end. Therefore, the shield can be connected to ground at the second end via a second capacitor mounted in parallel with the second power limiting resistor. Further, a second additional resistor can be mounted in series between the shield and the second capacitor.
  • the potential for the shield to be incendive depends on the potential difference between the first and second ends, and on the energy stored therein. Therefore, while it is possible to ground both ends of the shield without an EB between the groundings, it is far better to provide one in order to reduce the likelihood of an incendive potential difference arising. This is despite the fact that such a potential difference can arise with an EB anyway, as described above.
  • both the first end of the shield and a second end thereof can be connected to ground and an equipotential bond can be provided between the groundings.
  • a monitoring device can be mounted to the shield which can measure the voltage difference between the groundings.
  • the monitoring device can comprise a detection function for detecting hard ground faults occurring on the shield, and a reporting function which can issue reports on the detection of hard ground faults occurring on the shield.
  • the reporting function can be made intrinsically safe in any of the known ways.
  • a second end of the shield can be left floating, and a measuring device can be provided between the second end and the ground which can measure the potential difference between the first end and the second end of the shield.
  • a physical electrical EB is not a viable or a practical option to install due to the distance between instantiations, plots or plants.
  • a POTS telephone cable that spans 1 km between an exchange and a house will not have an an additional EB system or structure spanning the two, and local electrical supply grounds may come from separate utility supplies or
  • the ground potential difference between the exchange and the house will be unknown and/or uncontrolled, particularly if there is a ground fault in the exchange or the house.
  • the present invention is principally directed to use in industrial settings where EB systems are used, it ca also be applied to installations without an EB. In such cases the maximum possible voltages are used for the component sizing.
  • the various resistors and capacitors referred to above can be single components, but they can also be a plurality of components which collectively provide the same function. Therefore, the resistor and/or the capacitor and/or the additional resistor can comprise a plurality of such resistor or capacitor components accordingly, which can be arranged in parallel and/or in series. Likewise, the second resistor and/or the second capacitor and/or the second additional resistor can comprise a plurality of such resistor or capacitor components accordingly, which can be arranged in parallel and/or in series.
  • Figure 1 is a diagrammatic view of an intrinsically safe electrical circuit according to the present invention
  • Figure 2 is a diagrammatic view of a first shield of an intrinsically safe electrical circuit according to the present invention
  • Figure 3 is a diagrammatic view of a second shield of an intrinsically safe electrical circuit according to the present invention.
  • Figure 4 is a graph of the calculations and assessment for various lengths of cable, with various potential differences applied;
  • Figure 5 is a diagrammatic view of a third shield of an intrinsically safe electrical circuit according to the present invention.
  • Figure 6 is a diagrammatic view of a measuring system part of the third shield shown in Figure 4.
  • an intrinsically safe electrical circuit 100 comprises a power supply 101 , a load 102 and a cable 103 connecting the power supply 101 and the load 102, and comprising positive and negative cores 104 and 105.
  • the circuit 100 comprises an incendive arc prevention mechanism 106 which passively and/or actively limits the power in the positive and negative cores 104 and 105 to render them intrinsically safe.
  • the cable 103 comprises an electrically conductive
  • FIG. 1 shows the invention in its most basic form, according to claim 1 , and is provided for illustrative purposes only.
  • FIG. 2 illustrates a different arrangement in which cable shield 1 is mounted between terminations A and B.
  • Grounding 6a is provided at a first end 1 a of the shield 1
  • grounding 6b is provided at a second end 1 b of the shield 1 . If both potentials are equal then both terminations A and B are grounded to both groundings 6a and 6b.
  • Each termination A and B is grounded in the same way with one or more resistors 2a, 2b, with one or more capacitors 4a, 5a, 4b, 5b, and with one or more additional series resistors 3a, 3b.
  • additional series resistors 3a, 3b are optional, and also that each component 2a, 2b, 3a, 3b, 4a, 4b, 5a and 5b can be made up of two or more of the same type of component arranged in series and/or in parallel.
  • An EB is provided between the groundings 6a and 6b in the known way.
  • the components 2a, 2b, 3a, 3b, 4a, 4b, 5a and 5b are sized in value in accordance with the required safety factor in order to render the shield 1 non- incendive for the given application and hazardous area type.
  • they are sized in value to deal with any connection or disconnection between terminations A and B, and or between groundings 6a and 6b. They can also deal with any fault grounding at any point between terminations A and B, as well as any connection or disconnection of the groundings 6a, 6b.
  • They are also sized in value to offer the best low impedance path for any RFI/EMC connection to ground.
  • the IEC60479-1 standard on electrical safety sets out that a current through the human body of 5mA may be detectable but it will not result in muscle reaction.
  • a current through the heart though must be below 1 mA. Therefore, to satisfy this limit the resistance provided to the shield 1 should be a minimum of 71 kOhms, when using a potential of 250V rms.
  • resistors 2a and 2b are 360kOhms.
  • the resistors 2a and 2b are this size they also meet all other intrinsic safety requirements.
  • the IEC60079 part 1 1 standard determines a necessary size in value for each resistor 2a, 2b, 3a, 3b and each capacitator 4a, 4b, 5a, 5b. For example, if the potential difference is 12V, then each resistor 2a and 2b can be as low as 3.6 Ohms, and each pair of capacitors 4a and 5a, 4b and 5b can be as high as 1 .4 uF (micro- Farad) without requiring the additional series resistors 3a and 3b.
  • each pair of capacitors 4a and 5a, 4b and 5b can be higher in accordance with the IEC60079 part 1 1 standard. Therefore, the additional series resistors 3a and 3b can be removed if they are not required. However, their presence does provide a mechanism to deal with a short circuit occurring in any of the capacitors 4a, 4b, 5a, 5b. If this happened then the additional series resistors 3a, 3b can deal with it. As they are positioned in parallel with resistors 2a, 2b, all the resistors 2a, 2b, 3a, 3b can be sized in value and power accordingly.
  • resistors 2a, 2b and/or in resistors 3a, 3b with each pair of capacitors 4a and 5a, 4b and 5b). For example, if this was 1 Watt then this resistance must not be lower than 144Ohms at 12V. If the resistors 2a, 2b allow 1 W dissipation then they will also act to limit the current, and therefore the power passing through the shield 1 , and will therefore protect it from an overcurrent situation in which it might overheat or damage the integrity of the whole cable. As such, the resistors 2a, 2b, 3a, 3b will also perform as current limiting devices for shield faults to ground at one point between terminations A and B. Two such ground faults simultaneously occurring between terminations A and B is improbable, as it is for any intrinsically safe circuit. To help mitigate against this the arrangement show in Figure 2 can be provided at regular intervals, so the shield 1 has a shorter span. This can be done by
  • the shield 1 operate as follows. As it comprises intrinsically safe protection mechanisms at both ends 1 a and 1 b it can handle open circuits and short circuits occurring at either end 1 a and 1 b, and between terminations A and B.
  • the components at one end 1 a or 1 b of the shield 1 must be treated as acting independently in order for the requirements of the IEC60079 standard to be met. From such a perspective they do so by reacting to the short circuit by power limiting the shield 1 and therefore preventing any incendive arcs from occurring. Each end 1 a and 1 b can both react in this way in a compound fashion.
  • the shield 1 can be used as a probe to determine any potential difference across the EB system, and/or to detect the occurrence of a ground fault. This is a function which is not currently provided for with any known structures.
  • Figure 3 shows a second embodiment of the present invention in which a shield 7 comprises the same arrangement and components as shield 1 described above, except that voltage monitoring equipment 8 is attached across the resistors 9a and 9b.
  • the monitoring equipment 8 is intrinsically safe in accordance with the IEC60079 part 1 1 standard using any known method. It also has input impedance which is high enough not to affect the voltage across the resistors 9a and 9b, or to create significantly false readings, or to fail to meet the requirements of the
  • the resistors 9a and 9b can be split into two or more resistors, so that a potential divider will reduce the input voltage to the monitoring equipment 8).
  • the monitoring equipment 8 can detect if a ground fault has occurred anywhere between terminations C and D, and it can measure the potential difference between terminations C and D or resistors 9a and 9b.
  • the monitoring equipment 8 comprises suitable communications mechanisms of any of the known kinds so it can report its measurements to the control room, and alarms or other suitable actions can then be taken to rectify any actual fault, or to address the breach of a pre-defined fault condition.
  • Figure 3 shows the monitoring equipment 8 being located at a particular point, but it will be appreciated that it can be dispersed at one or more points between terminations C and D or resistors 9a and 9b.
  • the monitoring equipment 8 could be provided at both ends of the shield 7.
  • Monitoring points may also be inserted in series and/or in parallel (if in series then it may also measure current) with any of the components of the shield 1 .
  • the monitoring equipment 8 may operate by injecting voltage and/or current, and/or it may operate by measuring voltage and/or current, for DC and/or AC
  • shield 10 is illustrated as part of a powered data communications cable 1 1 which extends from a control room 12 to a device 13.
  • the cable 1 1 comprises power and return cores 14 inside it.
  • the shield 10 is grounded 15 at a first end 10a thereof in the same ways as shields 1 and 7 described above via a resistor 16, capacitors 17 and 18 and additional resistor 19 (which as described above is optional).
  • its second end 10b is not connected to ground and is left floating at the device 13.
  • a shield which is left floating at one end can be a design choice, but it can also be an arrangement which arises in the event that a shield like shields 1 and 7 described above is cut part way along its span. Therefore, while the below described monitoring is applied at the device 13, it could equally be applied anywhere along the length of a shield according to the present invention, and in particular one which is only resistively grounded at one end due to being cut.
  • the second end 10b of the shield 10 is grounded 21 with an intersecting series grounding capacitor 22 inserted.
  • This is permitted by the IEC60079 parti 4 standard as long as the total capacitance value connected from the shield to ground is less than 10nF for that given section of shield.
  • the capacitor 22 acts as a shunt for high frequency interference, and blocks the possibility of large circulating currents in the shield.
  • Figure 6 illustrates the arrangement of the capacitor 22 in greater detail. In particular, it is arranged between the second end 10b of the shield 10 and the local ground 21 .
  • a measuring device 23 measures the voltage between 10b and 21 , which gives an indication of the difference in voltage between the two ground points 21 and 15, and therefore across the EB system 20.
  • the measuring device 23 will be measuring DC or AC voltage (and/or inferred current). If a hard ground were used instead then no voltage would be measurable unless a series resistor 24 were inserted, as shown in Figure 6. If so, the voltage measurement would indicate AC or DC voltage and/or current.
  • the value of the resistor 24 is chosen to perform current and/or voltage measurement, and will be sized according to the required value and rating, to conform with the IEC60079 part 14 and/or 1 1 standards.
  • the resistor 24 can isolate 25 the resistance should the voltage increase to an incendive level, at which point a warning is given.
  • the resistor 24 may have a low value so as to act as closely to a hard ground as it can, but still high enough to measure the current. If this is isolated 25, then the grounding effect will be diminished, so it is important to maintain it if this is critical for noise reduction. These functions are obviously supported by the capacitor 22. If the capacitor 22 could deal with these issues itself then the resistor 24 would not be necessary. However, as it is included then if an open circuit at the control side grounding 15 were to occur, the resistor 24 will prevent the shield 10 from floating.
  • the measuring device 23 provides galvanic and/or optical data and/or power isolation from the signal cores 14 to ground 21 .
  • the isolation is afforded by one or more resistors 26, which may be capacitors if measuring AC only.
  • the capacitor 22 is a measuring instrument which is integrated with the device 13, which in this example is a switch 27.
  • the measuring device 23 communicates its measurement of the voltage across 10b and 21 as shown at 28 to the switch 27. It can do this using any known kind of analogue or digital signal. Any injected signal between 10b and 21 will be non-incendive, and the arrangement shown in Figure 6 will adequately isolate point 10b from point 21 to meet the relevant IEC60079 safety standards where required.
  • the switch 27 will in turn communicate the measured voltage and/or current via the cores 14 in any of the known ways to the control room 12.
  • the switch 27 comprises a digital data communication such as 4-20mA+HART (RTM), HART (RTM), Fieldbus (RTM) (which uses the term - 'device coupler' rather than switch), or a new high speed variant currently known as APL (which uses the term switch).
  • RTM digital data communication
  • HART HART
  • RTM Fieldbus
  • APL a new high speed variant currently known as switch.
  • the measured voltage and/or current will be converted into the relevant protocol for communication.
  • This could also be a modulation of one or more of the Physical Layer Attributes, for example, quiescent current modulation. Therefore the arrangement shown in Figures 5 and 6 acts as a safety warning system and a solution, which is able to measure the potential difference between the ground potentials at the opposite ends 10a and 10b of the shield 10. This provides an indication of the potential hazard and/or an EB fault condition, which can be announced to any maintenance crew working on the cable 1 1 , or in its vicinity.
  • the fault could be any earth fault in equipment sharing the same EB system 20 as the shield 10.
  • This solution provides these beneficial features without introducing an explosion potential, and without the need to run additional signal cables, wireless ports, power cables or batteries because it can send its
  • the arrangement shown in Figure 5 could be designed, but it could also be an arrangement which is implemented for measuring in the event that a shield like shields 1 and 7 described above is cut part way along its span. Therefore, while the measuring capacitor 22 is applied at the device 13, it could equally be applied anywhere along the length of a shield 10, including at its first end 10a.
  • the measuring principal demonstrated by the arrangement shown in Figures 5 and 6 can be employed on a trunk cable and/or on one or more spur cables.
  • the measuring system may be multiplexed for the spurs. Therefore, any number of the control/instrument cables may be monitored in this way throughout a plant.
  • the data can be collated and analysed not only for explosion safety, but also for monitoring ground faults in the EB infrastructure so faulty equipment can be identified for proactive/preventative action taken.
  • shields like shield 1 are provided with capacitors 4a, 4b, 5a and 5b and resistors 2a, 2b, 3a and 3b arranged in other combination (series and/or parallel), with any number thereof. All that is required is that the resulting arrangement meets the requirements of the IEC60079 standard, as well as the requirements for EMC/RFI suppression.
  • shields like shield 1 are provided with transient and/or voltage clamping diodes and the like such that they perform the same functions as components 2a, 2b, 3a, 3b, 4a, 4b, 5a, and 5b, provided they operate in a bi-polar way to account for the far end EB potential being positive or negative in respect to the local potential.
  • semiconductors are used instead, but if so they must be used with adequate protection means so that they can be classed as infallible in accordance with the IEC60079 standard.
  • shields like shield 1 are provided with additional reactive components in series and/or in parallel with one or more of the components 2a, 2b, 3a, 3b, 4a, 4b, 5a, and 5b.
  • This reactance includes inductors and/or infallible inductors.
  • a shield like shield 1 is only connected to ground via a resistor at one end and the other end is left disconnected.
  • the present invention provides a shield for an intrinsically safe cable which is itself rendered intrinsically safe in order to prevent incendive situations arising as a result of potential differences occurring on it.
  • the present invention also provides a shield with a secondary measuring function to provide alerts in the event of such potential differences, or other faults, occurring. This is particularly beneficial because the shield can act as a tool to detect faults in other equipment which effect the same EB system the shield is grounded to.

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  • Emergency Protection Circuit Devices (AREA)

Abstract

L'invention concerne un circuit électrique à sécurité intrinsèque comprenant une alimentation électrique, une charge et un câble connectant ladite alimentation électrique et ladite charge et comprenant des noyaux positif et négatif, ledit circuit comprenant un mécanisme de prévention d'arc générateur d'incendie qui limite passivement et/ou activement la puissance dans lesdits noyaux positif et négatif pour les rendre intrinsèquement sûrs, ledit câble comprenant un blindage électroconducteur contre les interférences entourant lesdits noyaux positif et négatif le long du câble, et dans lequel ledit blindage est rendu intrinsèquement sûr par une connexion à la masse au niveau d'au moins sa première extrémité par le biais d'une résistance de limitation de puissance.
PCT/EP2018/059664 2017-04-20 2018-04-16 Circuit électrique à sécurité intrinsèque à blindage contre les interférences à sécurité intrinsèque WO2018192873A1 (fr)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
GB1706266.2 2017-04-20
GBGB1706266.2A GB201706266D0 (en) 2017-04-20 2017-04-20 Intrinsically safe screen means
GBGB1712714.3A GB201712714D0 (en) 2017-08-08 2017-08-08 Equipotential bond measuring device and communication means
GB1712714.3 2017-08-08

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WO2018192873A1 true WO2018192873A1 (fr) 2018-10-25

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20070183108A1 (en) * 2006-01-24 2007-08-09 Fisher Controls International Llc Flameproof Apparatus Using Non-Grounded Energy-Limiting Barrier
US20090180226A1 (en) * 2006-02-03 2009-07-16 Pepperl & Fuchs Electrical Circuit with Incendive Arc Prevention
CN203117325U (zh) * 2013-02-01 2013-08-07 西安秦骊成套电器有限公司 一种直流测量方式的运行电缆接地状态检测电路
US20150087187A1 (en) * 2013-09-20 2015-03-26 Avedis Kifedjian Audio interface connector with ground lift, kit, system and method of use

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20070183108A1 (en) * 2006-01-24 2007-08-09 Fisher Controls International Llc Flameproof Apparatus Using Non-Grounded Energy-Limiting Barrier
US20090180226A1 (en) * 2006-02-03 2009-07-16 Pepperl & Fuchs Electrical Circuit with Incendive Arc Prevention
CN203117325U (zh) * 2013-02-01 2013-08-07 西安秦骊成套电器有限公司 一种直流测量方式的运行电缆接地状态检测电路
US20150087187A1 (en) * 2013-09-20 2015-03-26 Avedis Kifedjian Audio interface connector with ground lift, kit, system and method of use

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