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WO2001022104A1 - Procede de detection de mise a la masse defectueuse d'etat de haute impedance dans un reseau a tension moyenne - Google Patents

Procede de detection de mise a la masse defectueuse d'etat de haute impedance dans un reseau a tension moyenne Download PDF

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Publication number
WO2001022104A1
WO2001022104A1 PCT/FI2000/000816 FI0000816W WO0122104A1 WO 2001022104 A1 WO2001022104 A1 WO 2001022104A1 FI 0000816 W FI0000816 W FI 0000816W WO 0122104 A1 WO0122104 A1 WO 0122104A1
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Prior art keywords
zero
network
ground
line
unsymmetry
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English (en)
Inventor
Ari Nikander
Pertti JÄRVENTAUSTA
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ABB Substation Automation Oy
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ABB Substation Automation Oy
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Priority to AU72942/00A priority Critical patent/AU7294200A/en
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Anticipated expiration legal-status Critical
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
    • G01R31/52—Testing for short-circuits, leakage current or ground faults
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
    • G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
    • G01R27/16—Measuring impedance of element or network through which a current is passing from another source, e.g. cable, power line
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
    • G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
    • G01R27/16—Measuring impedance of element or network through which a current is passing from another source, e.g. cable, power line
    • G01R27/18—Measuring resistance to earth, i.e. line to ground

Definitions

  • the invention relates to a method according to claim 1 for detection of high-impedance ground-faults in a medium-voltage network and identification of a faulted sending end.
  • the applications of the invention can be found in medium-voltage networks, parti cu- larly in continuous detection of high-impedance ground faults of the network, identification of a faulted sending end and monitoring of the network condition utilizing for this purpose the measurement information of, e.g., a numerical multifunction relay.
  • the magnitude of the ground fault current imposed on the medium- voltage sending end is dependent on the total line-to-ground capacitance 3C 0 of the line section connected to the sending end.
  • the zero-sequence susceptance Bo of the sending end is computed based on the parameter values given by the line conductor manufacturers.
  • One problem herein arises from the inaccuracy of the parameter values that must be used in computations. From experience it is known that the value of the zero- sequence susceptance B 0 used in computations may be erroneous by up to 10-20 % in regard to the theoretically correct value.
  • the detection of high-impedance ground faults and identification of the faulted sending end is problematic due to the small magnitude of the fault current.
  • the most sensitive fault indicator directly measurable from a network under a fault situation is the zero-sequence voltage of the network.
  • fault detection based on a change in the RMS value of the zero-sequence voltage or a change in the line-to- ground leakage resistance does not necessarily detect directly the faulted sending end that must be determined by other means.
  • the method according to the inven- tion have been developed to provide independent status monitoring for each one of the sending ends. This goal is attained by way of determining the electrical insulation status and connection status of the network per sending end by way of continuous monitoring of line-to-ground admittances and level of line unsymmetry.
  • a significant benefit of the invention over conventional techniques is its realtime operation. This is based on up-to-date information available from the protective relays of the sending ends on the electrical length and insulation condition of the respective sending end.
  • the protective relay of the sending end also has information on the electrical length of the entire network and its insulation condition. The method does not require information transmission between the protective relay and the overlying systems or protective relays.
  • the fault detection technique disclosed therein is based of a method outlined as follows At the distribution substation are measured the hne-to-neutral voltages with their phase angles and therefrom is computed the zero-sequence voltage Uo of the network as a vector sum of the measured hne-to-neutral voltages, the network zero-sequence impedance Z 0 is computed, the zero-sequence voltage U 0 is compared with the hne-to-neutral voltages U v and the total zero-sequence impedance Z_o of the network. The thus obtained variables are then utilized for computing the fault impedances 2_ per each phase leg and the faulted phase leg is identified by being the leg with the largest real part of the fault impedance Z
  • the prior-art technique is handicapped among other things by the tendency of line conductor manufacturers to report the zero-sequence susceptance values on the "safe" side, whereby the ground-fault current values computed based thereon generally become larger that the actual values encountered
  • the computed parameters of line conductors involve terms of inaccuracy For instance, no information is submitted to a protective relay on the change of the electrical line length that is caused by a change in the network connection status
  • a fault location method based on monitoring the RMS value of the network zero- sequence voltage tells nothing about the location of the fault in the network. While a high-impedance fault may cause a larger change in the phase angle of the zero- sequence voltage than in the absolute value of the voltage, this information remains unutilized in said method.
  • Prior- art detection methods of high-impedance faults do not facilitate network monitoring per sending end, because the direction of the fault must be determined after the fault detection that is performed on the basis of the changes measured in the zero- sequence currents of the energized sending ends.
  • the method disclosed in FI patent publication no. 100922 B allows fault resistance monitoring only generally in regard to all the sending ends of the network.
  • the computation of the network zero-sequence impedance in said method is based on the zero-sequence susceptance values reported by the line conductor manufacturers that are accurate only to within a given error margin.
  • the line-to-ground capacitances of the network can be measured by way of making ground fault tests, but such results are valid only for the connection status prevailing during the tests.
  • the network zero-sequence impedance must be computed within a higher-level system, whereupon the information can be submitted to the protective relay.
  • the benefits of the method include detection of the faulted phase leg, possibility of the fault direction determination and good sensitivity.
  • the goal of the invention is attained by way of computing for the line-to-ground admittance and degree of unsymmetry at each one of the sending ends a reference value under a reference connection status using measurement information obtained during an artificially caused deviation in the zero-sequence voltage or under an actual ground fault occurring in the network and then using these reference values for at least an essentially continuous realtime monitoring of the respective variable values in the network, whereby a possible fault situation can be detected on the basis of predetermined limit deviation values.
  • the invention provides significant benefits.
  • One of the major novelty factors of the present method over prior-art methods and published techniques is related to the simplicity of the practical implementation and possibility of embedding the method as a part of other network automation.
  • the application of the method does not need a priori knowledge on the electro- technical data of the network components (that is, the network data) nor realtime information on the concurrent connection status of the network.
  • the present method can be appreciated to form a black box, whose input signals are the measured zero-sequence voltages and currents, while the output of the box is an indication of a ground fault that is sent as a unilateral event signal to a higher level system.
  • the method can be implemented within a single compartmentalized cell terminal and the fault indication does not need communications with other protective relays or information processing systems, which makes the present method more robust and flexible than, e.g., the method disclosed FI patent publication no. 100922 B.
  • a secondary relay/substation (REC) implemented according to the invention can be erected on a field disconnector station of the network.
  • REC secondary relay/substation
  • this kind of application does not need for fault indication supplementary initial information or communications with the higher level relays or information systems, the practical implementation of the present method is substantially more straightforward to implement than the method described in cited FI patent publication no. 100922 B.
  • the present method can detect in a self-contained manner changes in the network connection status and, hence, in contrast to the method disclosed in cited FI patent publication no. 100922 B, does not need realtime connection status information produced by another system, thus making the present system different from that described in cited FI patent publication 100922 B.
  • a crucial novelty value of present method is in its self-contained continuous opera- tion as compared with, e.g., that described in reference publication [Lei94], whose method is chiefly related to monitoring on the basis of discrete measurements.
  • the present invention in contrast utilizes inherent deviations of the zero-sequence voltage of the network. Accordingly, the computational routines of the method do not need tuning of the network compensation or connection changes in the network as some prior art methods do.
  • the determination of line-to-ground admittances at the sending ends by measurements improves the accuracy of fault current computations over the values obtainable by computations based on network data and, furthermore, facilitates providing the protective relay with the most recent information on the electrical length of the line connected to the monitored sending end.
  • the method allows positive fault indication even if the fault should occur rapidly after a change in the sending end connection status.
  • the invention facilitates monitoring of the individual sending ends of the network as to their electrical condition.
  • a change in the line leakage resistance not only tells about a fault but also indicates the faulted sending end and the faulted phase leg thereof.
  • Prior- art methods for detection of high-impedance faults were chiefly based on monitoring the zero-sequence voltage of the network or determining the total leakage resistance of the entire network. Therefore, the faulted sending end must be identified by other techniques.
  • One further advantage appreciated in the invention is that its implementation can be carried out without new equipment constructions or measurement arrangements in the network, but instead its computational algorithms are runnable on software that is programmed on existing numerical multifunction relays.
  • the line-to-ground admittance computation at a sending end is based on a change in the zero-sequence current and zero-sequence voltage instead of the absolute values of these variables, the error factor caused by the capacitance unsymmetry of the sending end is eliminated.
  • the zero-sequence current component due to the capacitance unsymmetry may play a significant part. Also a portion of the measurement error in the zero-sequence voltage can be eliminated.
  • a small neutral voltage always occurs even under normal conditions in a network grounded via a large reactance (resonant-ground system) or in an isolated-neutral network.
  • the neutral voltage can be altered by changing the tuning of the arc-suppression reactor.
  • a change in the connection status also causes a change in the neutral voltage in both a resonant-ground and an isolated-neutral network.
  • the neutral voltage under a normal condition may also be changed by means of an artificially generated capacitance unsymmetry.
  • a capacitor is connected to one phase leg of the network, whereby the neutral voltage of an operative network rises.
  • current injection to the neutral of the network can be used for changing the neutral voltage.
  • This can be implemented in a relatively simple manner by connecting a 230 V voltage to an auxiliary winding (500 V) or measurement winding of the arc-suppression reactor.
  • the current injection system can be isolated from the low-voltage circuit with the help of a suitable isolation transformer.
  • a capacitor can be used for current limiting.
  • the injection current may be smaller than 1 A and the duration of current injection need not be longer than a few seconds.
  • Equations 1-4 used in the invention for computing the line-to-ground admittances and degree of network unsymmetry are known to those versed in the art. These equations are described in, e.g. cited publications [Lei97] and [Lei94].
  • the inventiveness of the present invention is based on the novel and continued development and application of these computational techniques into a network protection method utilizing the capabilities of a numerical multifunction relay without any need to provide additional information to the relay from higher-level automa- tion systems of the network.
  • i sending end subindex
  • i 1,2,3,...
  • v phase subindex
  • 1,2,3 t sum of all the three phases
  • the summed line-to-ground admittance of all the three phases is predominantly capa- citive. Denoting the angular frequency corresponding to a nominal frequency of
  • the degree of unsymmetry can be defined for both the entire network and a single sending end.
  • the admittances are the line-to-ground admittances for the sending end concerned.
  • the line-to-ground admittance of a sending end can be computed from the change of the zero-sequence current and voltage (Eq. 3).
  • subindexes a and b refer to two separate measurements of the zero-sequence voltage and current.
  • the zero- sequence voltage and current phasors are compared with such a reference phasor that does not change during a ground fault.
  • Such an applicable reference phasor is one of the line-to-line voltages.
  • the use of the change of the zero-sequence voltage and current in the computation of the line-to-ground admittance eliminates the effect of zero-sequence component due to the capacitance unsymmetry on the end result of the computation.
  • the sending-end line-to-ground admit- tances may also be computed directly from the zero-sequence current and voltage, because herein the capacitance unsymmetry effect is negligible. This is because the zero-sequence current component related to the capacitance unsymmetry is not dependent on the zero-sequence voltage, whereby
  • the basic concept of the invention is that the line-to-ground admittances and degrees of unsymmetry of the sending ends are computed each time the zero-sequence volt- age of the network changes. In this manner it is assured that the line-to-ground admittances based on the measurement data obtained at the sending ends and the fault current values derived therefrom are at any time representative of instantaneous connection status of the network.
  • the goal of the method is to indicate ground faults having a fault resistance in the range of 100 - 200 kohm. For ground fault resistances smaller than 10 kohm, the faulted sending end can be detected directly on the basis of the change in its line-to-ground admittance.
  • the computation is supportive to the normal protection given by directional relays.
  • the method is in the same manner applicable to an isolated-neutral network as to a resonant-ground network and does not need a change of the relay operating characteristics if the network-compensating reactor is disconnected from the network.
  • FIG. 1 the steps are described elucidating the operation principles of the invention in the determination of the electrical length of a line, indication of high-impedance ground faults and determination of a faulted sending end:
  • a reference value of the initial status (that is, the reference connection status, where- from computations begin) is computed for the line-to-ground admittance Y tEl of each sending end and for the degree of unsymmetry Ik,!, whereby an artificial shift of the neutral voltage or a change thereof caused by a switching status change or a ground fault is utilized for this purpose.
  • the computation follows the techniques disclosed in cited publication [Lei97].
  • zero-sequence current computed from the line-to-neutral currents of the sending end or, alternatively the zero-sequence current of the reactor branch if such a measurement value is available.
  • the zero-sequence voltage is computed as a phasor sum of the line-to-neutral voltages or, alternatively, is measured from the open-delta winding of the voltage transformers.
  • a reference capacitance Serving as the line-to-ground capacitance C t ⁇ in the computation of the degree of unsymmetry at each sending end is used a reference capacitance whose value is selected to be equal to the summed line-to-ground capacitance of all the three phase legs of the entire network in its reference connection status.
  • the summed line-to-ground capacitance of the entire network can be computed from the zero-sequence current change of each sending end using Eqs. 1 and 3.
  • the values of line-to-ground capacitance per sending end are required for determining the electrical length of the line and indication of high-impedance ground faults.
  • the zero-sequence voltage and sending-end current values denoted as Uo ref , lo ref i-
  • the zero-sequence current change at the faulted sending end is not used as such for fault indication, but instead the fault-situation zero-sequence voltage, sending-end zero- sequence current and precomputed value of the line-to-ground admittance are utilized for computing a parameter k which is representative to the unsymmetry of the sending end and whose change can be used for fault indication.
  • the computation is performed simultaneously for each one of the sending ends, whereby the faulted sending end is found directly from the result of the computation and there is no need to identify the fault at the network level as is suggested in FI patent publication 100922 B. This approach gives higher sensitivity in fault location than what can be attained by detecting the fault merely from the change in the line-to-ground admit- tance of the faulted sending end.
  • the computed line-to-ground admittance values of the sending ends are compared with the reference values Y t&ref - If the sending-end line-to-ground admittance does not differ from the reference value Yt Br ef by more than a preset error tolerance ⁇ Y t E, caused by computational and measurement inaccuracy errors, the status of the sending end is assumed to be unchanged and the sending end obviously has no ground fault. In this case the stored reference value is not changed. If the deviation of the sending-end line-to-ground admittance value from the reference value Yt&r e f is greater than ⁇ Y tE ⁇ , it is plausible to assume that the sending-end connection status has been changed or that the sending end is affected by a ground fault.
  • a change in the connection status may also be inferred from the summed line-to-ground admittance change of the entire network, which is computed from the zero-sequence current of the feeding power source.
  • this approach is applicable only when the change in the electrical line length exceeds the possible deviation due to measurement inaccuracy in the computed value of the entire network's admittance.
  • the computed degrees of unsymmetry at the sending ends are compared with the stored reference values
  • An alternative method of monitoring the degree of unsymmetry is to monitor the ground-leakage resistances of the different phase legs at the sending ends.
  • the moni- toring of the leakage resistances may be arranged to take place in parallel with the monitoring of the degree of unsymmetry. If the degree of unsymmetry at any sending end changes, it is possible to infer from the leakage resistance R f whether a ground fault or a change in the connection status has occurred. This inference also gives such information on the faulted phase leg that may be utilized in the location of faults not identifiable by visual inspection. For instance, it is possible in conjunction with lightning arresters to determine which one of three phases has a defective arrester. Arc arresters are typically used for overvoltage protection of substations and underground cables. The physical location of phase-leg conductors at substations and underground cable terminations are generally identified.
  • the leakage resistances of the different phases can be computed from Eq. 5 written as:
  • Uo zero-sequence voltage.
  • the zero-sequence current at the sending end comprises a zero-sequence-voltage- dependent component Quo) and an unsymmetry-dependent component (I k ) in accordance with Eq. 6 below.
  • the line-to-ground capacitances per phase are not exactly equal.
  • the effect of the error caused by capacitance unsymmetry can be reduced in the following manner.
  • the capacitance-unsymmetry-dependent component of the zero-sequence current can be determined with the help of Eq. 6, whereupon its effect on the leakage resistance may thus be eliminated.
  • the leakage resistances at each phase leg can be monitored on a continuous basis without allowing the capacitance unsymmetry to have any effect on the computational result. Changes in the zero-sequence voltage do not affect the capacitance-unsymmetry- dependent component of the zero-sequence current. In this manner, the status monitoring can be carried out on a continuous basis without a need for deviations to occur in the zero-sequence voltage.
  • the unsymmetry-dependent component of the zero-sequence current may also be used as a direct fault indicator according to Eq. 6.
  • a ground fault causes a change equal to the fault current in the unsymmetry-depen- dent component of the zero-sequence current.
  • I OKI unsymmetry-dependent current component of sending end i in a normal condition
  • Io ⁇ f ⁇ unsymmetry-dependent current component of sending end i in a fault condition.
  • the fault resistance may also be determined from Eq. 8 [Lei97].
  • the computation is carried out replacing the absolute values of zero- sequence current and voltage by the changes of these variables:
  • ⁇ I 0l (zero-sequence current I 0 of sending end i during fault) - (zero-sequence current I 0 of sending end i before fault)
  • Indication of a high-impedance fault and detection of a faulted sending end from the degree of unsymmetry or by means of Eqs. 5, 7 or 8 require the line-to-ground admit- tances of the sending ends to be known a priori for a situation prevailing before the fault. If the change in the zero-sequence voltage is caused by a ground fault, the line- to-ground admittances can be computed for all sound sending ends. In contrast, if the change in the zero-sequence voltage is caused by a change in the connection status, the line-to-ground admittances can be computed for all those sending ends that maintain their connection status unchanged. In the following is described a method for indication of a change in the connection status and determination of a new line- to-ground admittance value after a change in the connection status.
  • a change in the connection status of a sending end can be indicated and distinguished from a line fault with the help of the changes occurring in the zero-sequence voltage and current.
  • the sending-end line-to-ground admittance Y 0l is already known in the initial condition.
  • the change in the sending-end line-to-ground admittance is denoted as ⁇ Yo.
  • Eq. 9 The formulation of Eq. 9 is based on the assumption that the zero-sequence current caused by the capacitance unsymmetry is not changed due to the change in the connection status.
  • the detection of connection status change can be performed in a reliable manner. If the sending end has no change in its connection status nor a ground fault, the change ⁇ Y 0 in the line-to- ground admittance remains zero. Simultaneously, the method makes it possible to compute an estimate for the change in the electrical length of the line. Then, the line- to-ground admittance of the sending end can be corrected to a value corresponding to its new connection status.
  • the ground fault detection is implemented by means of computing the leakage resistance per sending end with the help of Eqs. 5 and 8.
  • the new value of line-to-ground admittance can be determined using one of the methods described below:
  • the changed situation is allowed to continue until a new change in the zero-sequence voltage of the network occurs due to a ground fault or connection operation, whereby the new value of line-to-ground admittance can be computed.
  • the neutral voltage can be altered artificially, e.g., by changing the tuning of the arc-suppression reactor. Another possibility is to change the electrical length or capacitance unsymmetry of the network. If the substation is equipped with a centralized compensation system, the neutral voltage can be shifted by means of connecting an adjustable or constant voltage supply to an auxiliary winding (e.g., to a 500 V winding) of the arc-suppression reactor. These techniques for shifting the neutral voltage are known in the art. Typically, they have been used for determination of network parameters and tuning of the arc-suppression reactor.
  • the zero-sequence susceptance of the network is determined with the help of the network data.
  • a novel feature of the present invention is that the error margin of the zero-sequence susceptances can be reduced by virtue of assuming each line section to contribute by a given percent proportion to the total zero-sequence susceptance Bo at the sending end. Then, the computations are made using the value prevailing before the change in the connection status as the total zero-sequence susceptance value. Resultingly, the upper level control system can compute the percent change in the sending end zero-sequence susceptance, whereby the new value of line-to-ground admittance is obtained.
  • Method a of the above-described alternatives is not useful in cases where the ground fault occurs rapidly after a change in the network connection status, whereby a new line-to-ground admittance value has not yet been computed.
  • the degree of unsymmetry or line-to-ground leakage resistance computed on the basis of the ground admittance value valid before the connection status change is not physi- cally correct, while it may be sufficiently close to indicate the fault.
  • the computation of the sending end line-to-ground admittance and the degree of unsymmetry can be based on the reference value Ioreti and the values of the zero-sequence voltage and current that were valid during the fault. Since the value of I 0ref i was measured during the earlier connection status, the values of line-to-ground admittance and degree of unsymmetry computed from Eqs. 3 and 4 are not physically correct. However, the changes occurring in these parameter values make it possible to detect a ground fault on the monitored sending end. Even if the sending end would be found to be in an "uncertain" state after the connection status change, the fault indication is yet entire feasible.
  • One possibility of determining the line-to-ground admittance of the monitored send- ing end after a change in the connection status is to use first method c and, after the network has undergone a change in its neutral voltage, use the alternative method a for computing the line-to-ground admittance.
  • Knowing the degree of compensation in the network is important, since this param- eter has a significant effect on the suppression conditions of the arc occurring during a ground fault and, thus, on the short-duration outages on customer services.
  • Such medium-voltage networks that have the ground fault compensation implemented using fixed arc-suppression reactors or tunable reactors having a stepwise adjustable tap selection, the determination of network degree of compensation is rather inaccurate on the basis of network data and the nominal specifications of the reactor.
  • the arc-suppression reactors may also be located in a distributed manner around the network. Then, a change in the connection status of the network also changes the network degree of compensation. Modeling techniques to be described later facilitate computational determination of network degree of compensation for each different connection status.
  • the network degree of compensation can be monitored in the same fashion as is described for the line-to-ground admit- tances and degree of capacitance unsymmetry. The computation of degree of compensation also permits automatic tuning control of the arc-suppression reactor after a change in the connection status.
  • the summed ground capacitance E of the three phase legs of the network can be determined from the change of the zero-sequence current at the sending end with the help of Eqs. 1 and 3. If the network includes distributed arc-suppression elements, the susceptances of the separate reactors connected to the sending ends must be subtracted from the term CDQ E and added to the term l/ ⁇ L 0 ⁇ which represents the susceptance of a reactor connected to the star point of the main transformer at the substation or, respectively, a star point formed with the help of a grounding transformer.
  • L OE can be determined with the help of the zero-sequence current and zero-sequence voltage of the sending end or, alternatively the zero-sequence current and zero-sequence voltage of the reactor branch.
  • an overcompensation status of a given sending end can be identified by a measurement of its line-to-ground admittance.
  • a protective system based on the measurement of the losin ⁇ value (which is a common practice in networks compensated with distributed arc-suppression elements) operates erroneously when the ground fault occurs elsewhere in the network.
  • the zero-sequence susceptances of the lines connected to the sending ends can be computed during ground faults. It must be noted that networks having overhead lines are particularly subject to a relatively high rate of temporary ground faults that elevate the neutral voltage of the network. Then, the zero-sequence susceptances of the sound sending ends can be computed directly from the reactive component (I 0 sin ⁇ ) of the sending-end zero-sequence current and the zero-sequence voltage of the network. On the other hand, the protective relay of the faulted sending end measures the ground fault current invoked by the rest of the network. Therefore, the portion of the ground fault current produced by the faulted sending end does not contribute to this measurement.
  • method c In the case a change occurs in the connection status of the sending end, the above- described method c must be used.
  • the zero-sequence susceptance of the sending end can be measured at a higher accuracy when the neutral voltage rises the next time.
  • method c gives a sufficiently accurate estimate of the zero-sequence susceptance of the sending end after a connection change.
  • the method disclosed herein is cost-efficient inasmuch it dispenses with the installation of new measurement techniques or equipment.
  • the only operation required to implement the method is the programming of a new functional software routine for the protective relay.
  • an implementation of the present method when carried out by way of placing only one multifunction relay at a substation with communications to the older-generation numeric relays is the most cost-efficient alternative.
  • the neutral voltage is generally sufficiently high for the computation of the parameters needed.
  • a disadvantage that may be encountered is that in ground-isolated overhead networks with properly transposed conductors and in underground cable networks the steady-state zero-sequence voltage and, hence, the zero-sequence currents of the sending ends may be too small for reliable compu- tation of the line-to-ground admittances.
  • the line-to-ground admittances can be computed in conjunction with ground faults occurring in the network or, alternatively, by shifting the neutral voltage of the network in an artificial manner.
  • the method needs at least one multifunction relay per each substation.
  • the measurement data required include one line-to-line voltage, the neutral voltage, the zero- sequence current of the sending end or, alternatively, the zero-sequence current of the arc-suppression reactor branch and the zero-sequence currents of the sending ends. In practice all of these measurement values are available at essentially any substation.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Emergency Protection Circuit Devices (AREA)
  • Testing Of Short-Circuits, Discontinuities, Leakage, Or Incorrect Line Connections (AREA)

Abstract

L'invention concerne un procédé de détection de mise à la masse défectueuse de haute impédance dans un réseau de tension moyenne. Conformément à ce procédé, le degré d'asymétrie (|kI|) et/ou l'admission à la masse (YtEi), ainsi que la tension séquence-zéro (U0) de chaque extrémité d'envoi (i) sont déterminées. Selon la présente invention, on détermine, pour les valeurs de l'admission à la masse (YtEi) et du degré d'asymétrie (|kI|) de chaque extrémité d'envoi (i), une valeur de référence (YtEiref et |kIref|), basée sur les informations de mesure obtenues au moyen d'une déviation artificielle de la tension neutre réalisée dans un état de connexion de référence. On stocke dans une mémoire des valeurs de référence de l'admission à la masse (YtEiref) et du degré d'asymétrie (|kIref|) de chaque extrémité d'envoi (i), ainsi que les valeurs d'état de connexion normale de la tension séquence-zéro (U0ref), les courants séquence-zéro (I0refi) des extrémités d'envoi (i) et le courant séquence-zéro (I0refs) de la source d'énergie d'alimentation, la tension séquence-zéro (U0) est évaluée au moins en permanence pour l'essentiel et, si ladite tension séquence-zéro (U0) varie au-delà d'une différence limite prédéterminée (ΔU0as) pour chaque extrémité d'envoi (i) sont calculées de nouvelles valeurs d'admission à la masse (YtEi) et de degré d'asymétrie (|kI|). Les valeurs calculées en dernier de l'admission à la masse (YtEi) sont comparées avec les valeurs de référence (YtEiref) et à partir de cette comparaison, on détermine si la différence dépasse l'inexactitude (ΔYtEi) de la technique de mesure employée, ainsi, si la comparaison produit une valeur supérieure à ladite inexactitude (ΔYtEi), on vérifie par exemple, sur la base de la modification, dans tout le réseau de l'admission à la masse totalisée qui peut être calculée à partir du courant de séquence-zéro de la source d'énergie d'alimentation, si une modification est survenue dans l'état de connexion du réseau et, si c'est le cas, les valeurs calculées en dernier de l'admission à la masse (YtEi) et du degré d'asymétrie (|kI|) sont stockées comme nouvelles valeurs de référence, alors, que si aucune modification ne s est produite dans l'état de connexion du réseau, une mise à la masse défectueuse est notifiée.
PCT/FI2000/000816 1999-09-23 2000-09-22 Procede de detection de mise a la masse defectueuse d'etat de haute impedance dans un reseau a tension moyenne Ceased WO2001022104A1 (fr)

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AU72942/00A AU7294200A (en) 1999-09-23 2000-09-22 Method for detection of high-impedance ground faults in a medium-voltage network

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FI19992044 1999-09-23
FI992044A FI112283B (fi) 1999-09-23 1999-09-23 Menetelmä keskijänniteverkon suuri-impedanssisten maasulkuvikojen ilmaisemiseksi

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EP1870717A1 (fr) 2006-06-20 2007-12-26 ABB Technology AG Système et procédé de détermination des admittances entre phase et terre d'une ligne électrique triphasée.
US7720619B2 (en) 2006-08-04 2010-05-18 Schweitzer Engineering Laboratories, Inc. Systems and methods for detecting high-impedance faults in a multi-grounded power distribution system
WO2011029464A1 (fr) * 2009-09-09 2011-03-17 Siemens Aktiengesellschaft Identification de défauts dans des réseaux d'alimentation en énergie présentant un point neutre non relié à la terre ou une disparition du point neutre
WO2011038757A1 (fr) 2009-09-30 2011-04-07 Areva T&D Uk Limited Procédé de détection de défaut à la terre à impédance élevée pour la protection différentielle de lignes de transmission aériennes
WO2014194941A1 (fr) 2013-06-05 2014-12-11 Siemens Aktiengesellschaft Détection de défauts à la terre dans des réseaux de distribution d'énergie à point neutre compensé
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US9160158B2 (en) 2012-10-12 2015-10-13 Schweitzer Engineering Laboratories, Inc. Coordinated high-impedance fault detection systems and methods
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US10161986B2 (en) 2016-10-17 2018-12-25 Schweitzer Engineering Laboratories, Inc. Electric power system monitoring using distributed conductor-mounted devices
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CN108508314A (zh) * 2018-02-24 2018-09-07 安徽合凯电气科技股份有限公司 一种高精度选线跳闸装置
CN112731054B (zh) * 2020-12-19 2022-06-14 国网河南省电力公司电力科学研究院 基于零序残压抑制的配电网单相接地故障选线方法

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1870717A1 (fr) 2006-06-20 2007-12-26 ABB Technology AG Système et procédé de détermination des admittances entre phase et terre d'une ligne électrique triphasée.
US7720619B2 (en) 2006-08-04 2010-05-18 Schweitzer Engineering Laboratories, Inc. Systems and methods for detecting high-impedance faults in a multi-grounded power distribution system
US7945400B2 (en) 2006-08-04 2011-05-17 Schweitzer Engineering Laboratories, Inc. Systems and methods for detecting high-impedance faults in a multi-grounded power distribution system
WO2011029464A1 (fr) * 2009-09-09 2011-03-17 Siemens Aktiengesellschaft Identification de défauts dans des réseaux d'alimentation en énergie présentant un point neutre non relié à la terre ou une disparition du point neutre
WO2011038757A1 (fr) 2009-09-30 2011-04-07 Areva T&D Uk Limited Procédé de détection de défaut à la terre à impédance élevée pour la protection différentielle de lignes de transmission aériennes
US9160158B2 (en) 2012-10-12 2015-10-13 Schweitzer Engineering Laboratories, Inc. Coordinated high-impedance fault detection systems and methods
WO2014194941A1 (fr) 2013-06-05 2014-12-11 Siemens Aktiengesellschaft Détection de défauts à la terre dans des réseaux de distribution d'énergie à point neutre compensé
CN104280663A (zh) * 2013-07-03 2015-01-14 刘宝稳 一种小电流接地系统单相接地故障在线监视与选线方法
US10161986B2 (en) 2016-10-17 2018-12-25 Schweitzer Engineering Laboratories, Inc. Electric power system monitoring using distributed conductor-mounted devices
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AU7294200A (en) 2001-04-24
FI19992044A7 (fi) 2001-03-23

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