method for determining a fault direction parameter on an ac transmission line, fault direction param

专利摘要:
METHOD FOR DETERMINING A FAULT DIRECTION PARAMETER IN AN AC TRANSMISSION LINE, FAULT DIRECTION PARAMETER INDICATOR, DIRECTIONAL OVERCURRENT RELAY AND USE OF THE DEVICE. The present invention relates to a method for determining a fault direction parameter of a fault in a transmission line. Failure direction parameter indicating device is AC (10) of a power distribution system (1) with respect to to a measurement location (12) of the transmission line (10). The method comprises: measuring, by means of a measurement unit (20), a time-dependent AC current from the transmission line (10) at the measurement site (12), thus obtaining current data in the time domain (80) indicative of the measured current; the measuring unit (20) comprising a current sensor for measuring the current at the measuring location (12) of the transmission line (10), but without a voltage sensor; transmit the current data to a decision logic section 36; obtaining a failure time (81) of the failure in the AC transmission line (10); identify a first time (t1) and a second time (t2) by identifying a characteristic periodically recurrent in the current data (80), so that the failure time (81) is between the first time (t1 ) and the second time (t2), in which the periodically recurring characteristic is selected from the group consisting of a crossing of zero, a maximum, a minimum and a greater gradient of the current data; extract from the current data (80) a deviation parameter (82; 86; 87) indicating a time deviation (81?) from the current at fault time (81), where the deviation parameter (82) it is a time interval between the first half (t1) and the second half (t2); calculate a deviation direction parameter by comparing the indicative deviation parameter (82; 86, 87) to a non-indicative deviation parameter (84); and establish the fault direction parameter based on the calculated deviation direction parameter.
公开号:BR112013008760B1
申请号:R112013008760-9
申请日:2011-10-14
公开日:2021-02-23
发明作者:Abhisek UKIL；Bernhard Deck；Vishal H. Shah
申请人:Abb Schweiz Ag；
IPC主号:

专利说明:

[001] Aspects of the invention relate to a fault direction parameter indicator device for a power distribution system, in particular a fault direction parameter indicator device to indicate a direction parameter of a failure in a transmission line. Additional aspects refer to a directional overcurrent relay which include such a fault direction parameter indicator device and which additionally include a circuit breaker. Additional aspects refer to methods for determining a fault direction parameter of a fault in a transmission line in a power distribution system. Background of the Technique:
[002] Directional overcurrent relays are widely used for the protection of power distribution systems such as radial and ring transmission subsystems and other distribution systems. These relays have a feature that enables them to determine a fault direction. Here, a failure usually means an overcurrent, usually from a short circuit. In addition, the fault direction is, in most cases, binary information that indicates whether the fault is a direct fault or a reverse fault. Here, on a power line that connects an upstream power supply to a portion of the downstream power distribution system (with the normal power direction from upstream to downstream), a direct direction is downstream. of the relay and the reverse or reverse direction is the upward flow of the relay.
[003] In smart electric grids, decentralized or distributed units can feed energy into the grid or consume energy from the grid. Therefore, in smart power grids the direction of energy flow can change over time. In this situation, "forward" and "reverse" can still be defined as above with respect to the current energy flow so that, for example, the direct direction will change if the energy flow is reversed.
[004] More generally, the fault direction is an indicator in which a fault has occurred on one side of a measurement location. In the example above, there are two directions, forward and reverse. If the measurement location is on a power grid node that has more than two sides, there may be more than one forward and reverse direction. For example, for a node to which a reverse line portion and two straight line portions are connected, the fault direction can include "forward-1", "forward-2" and "reverse".
[005] Directional information provides more detailed information about the location in which a fault occurred. This information can be used to disable a smaller portion of the power distribution system in the event of a failure. For example, a conventional main ring feeder for domestic supply has circuit breakers at its T junctions. If there is a fault in any of the lines on this conventional ring main feeder, the entire section of the line is normally interrupted. This situation can be improved when more detailed fault direction information is obtained. For this purpose, directional overcurrent relays can be installed on the line along switches. With such a switch-relay system, a measurement of the reference voltage allows the computation of the fault current and its direction. Directional information can then be used to disconnect only the appropriate section, instead of the entire line.
[006] Known directional overcurrent relays depend on a reference voltage phasor, also known as "voltage bias" to estimate the direction of the fault. When a fault occurs, the fault current has a characteristic phase angle in relation to the voltage phasor, the phase angle depends on the direction of failure. The fault direction is determined by comparing the current phasor (complex current value whose actual part is the current AC current) to a reference voltage phasor (known industrially as 'voltage bias') measured at a measurement location in the power line. This requires the measurement of both current and voltage. This approach becomes fallible when the fault is close to the relay because, in this case, the relay is almost grounded by the short circuit (known industrially as 'proximity faults').
[007] Additionally, overcurrent relays that include a voltage measurement unit are expensive. Since they have to be used in greater numbers for the above arrangement, this is a major cost factor.
[008] In "Fault Direction Estimation in Radial Distribution System Using Phase Change in Sequence Current" fr PRADHAN AK ET AL, IEEE TRANSACTIONS ON POWER DELIVERY, IEEE SERVICE CENTER, NEW YORK, NY, USA, volume 22, Number 4.1 October From 2007 (01/10/2007), pages 2065 to 2071, XP011191870, ISSN: 0885-8977, DOI: DOI10.11 09 / TPWRD.2007.905340, the fault direction estimation is proposed based on a phasor estimation. Current data in the time domain that indicates the measured current is not obtained.
[009] The document DE 19835731A1 proposes an initial experimentation configuration for estimating fault direction for analyzing the phase angle between current and voltage in an electrical network.
[010] In "Evaluation of a New Current Directional Protection Technique Using Field Data" by EISSA MM, IEEE TRANSACTIONS ON POWER DELIVERY, IEEE SERVICE CENTER, NEW YORK, NY, USA, volume 20, Number 2.1 April, 2005 (01 / 04/2005), pages 566 to 572, XP011129251, ISSN: 0885-8977, DOI: DOI: 10.1109 / WRD.2005.844356 the difference in phase relationship created by a fault is explored when making relays that respond to an angle of phase difference between two quantities, such as the fault current and the pre-fault current.
[011] “Smart Distribution Protection Using Current_Only Directional Overcurrent Relay” by Ukhil A. et al., Innovative Smart Grid technologies Conference Europe (ISGT Europe) 2010 IEEE PES, IEEE, Pisctaway NJ, USA, October 11, 2010, pages 1 -7, XP031803713, ISBN: 978-1-4244-8508-6 discloses a method for determining a failure direction parameter of a failure in an AC transmission line. Summary of the invention
[012] In view of the above, a method for determining a fault direction parameter according to claim 1, a fault direction parameter indicator device according to claim 10, a directional overcurrent relay according to with claim 12 and a use according to claim 11 are provided. Advantages, characteristics, aspects and additional details that can be combined with modalities described in this document are evident from the dependent claims, the description and the drawings.
[013] According to a first aspect, a method is provided to determine a failure direction parameter of a failure in an AC transmission line of a power distribution system in relation to a transmission line measurement location, for example, for outdoor applications. The method comprises: measuring an AC current dependent on the time of the transmission line at the measurement site by means of a measurement unit, thereby obtaining current data in the time domain that indicates the measured current, the measurement unit comprising a sensor current to measure the current at the measurement location of the transmission line, but no voltage sensor; transmit the current data from the measurement unit to a decision logic section; obtain a failure time of the failure in the AC transmission line; identify a first time and a second time by identifying a periodically recurring characteristic of the current data in such a way that the failure time is between the first time and the second time, in which the periodically recurring characteristic is selected from the group that it consists of a crossing of zero, a maximum, a minimum and a greater gradient of the current data; extract, from the current data, an indicative parameter of deviation that indicates a time deviation of the current in the time of failure in which the indicative parameter of deviation is a time interval between the first time and the second time; calculate a deviation direction parameter by comparing the indicative deviation parameter to the indicative non-deviation parameter and establish the fault direction parameter based on a signal from the calculated deviation direction parameter. The non-indicative deviation parameter indicates the absence of a time deviation from the current between the first and second times.
[014] According to another modality, the method that comprises the step of extracting the indicative deviation parameter includes choosing integral limits of a current integration time interval in such a way that the current integration time interval is a normal period length of the AC current or a multiple of its integral; and calculating a numerical integral of the current data over the current integration time interval.
[015] According to an additional modality, the method comprises determining a second fault direction parameter from the current signal by a second fault direction determination program, in which the second fault direction determination program includes receiving a current signal comprising pre-fault and post-fault current values of a complex number of an input section, determining a phase angle of the respective current values, determining a plurality of phase difference values between selected from the angles phase, add at least some of the phase difference values to obtain an accumulated phase difference parameter and determine the second fault direction parameter by comparing the accumulated phase difference parameter with a limit value and establish a direction parameter master fault from the first fault direction parameter and the second fault direction parameter and issue the dir parameter master fault indication.
[016] According to a second aspect, a fault direction parameter indicator device is provided to indicate a fault direction parameter of a fault in an AC transmission line of a power distribution system in relation to a measurement location of the transmission line. The fault direction parameter indicator device comprises a measuring unit, the measuring unit comprising a current sensor for measuring AC current at the transmission line measurement site, but no voltage sensor, where the unit measuring device is operationally coupled to an input section to transmit current data in the time domain obtained from the current measurement to the input section; an input section configured to receive current data in the time domain that indicates a time dependent current measured by a unit of measurement at the measurement site; a section of decision logic configured to determine the fault direction parameter based on current data in the time domain. The decision logic section comprises a subsection of fault deviation calculation configured to extract, from the current data, an indicative deviation parameter that indicates a time deviation from the current in a fault time, in which the extraction of the deviation parameter includes identifying a first time and a second time by identifying a periodically recurring characteristic of the current data, such that the failure time is between the first time and the second time and where the deviation parameter it is a time interval between the first and second times, in which the periodically recurring characteristic is selected from the group consisting of a crossing of zero, a maximum, a minimum and a greater gradient of the current data; a deviation direction calculation subsection configured to calculate a deviation direction parameter by comparing the indicative deviation parameter to an indicative non-deviation parameter that indicates an absence of a current time deviation; and a subsection of fault direction parameter setting configured to establish the fault direction parameter from the calculated deviation direction parameter. According to one aspect, the decision logic section is configured to perform any method steps described in this document.
[017] The above aspects allow the determination of a fault parameter such as a fault direction reliably and efficiently at a reduced cost. Cost reduction, among other factors, is possible due to the fact that no voltage measurement is necessary because the calculations are simple and can be performed at a sufficient speed with limited hardware.
[018] That is, simple calculations are possible because the deviation direction parameter can be calculated, according to aspects of the invention, based on current data in the time domain. In the present document, data in the time domain is data that represents a quantity, for example, current, as a function of time. In other words, a time can be assigned to the data points. The data may have been subject to operations that are slightly non-local in time, so that the data is somewhat obscured in time or may include information obtained in other times, provided that a specific time can still be rationally assigned to measurement (for example, a median time). For example, data can be subjected to a floating-point average operation or a low-pass filter to eliminate high-frequency noise. However, this non-local processing must be on a time scale that is less than a period of the AC current, for example, less than 0.2 times the AC period. This guarantees fast data availability and limited hardware requirements, as each of the data in the time domain can be obtained from a limited number of current measurements quickly after the current measurement. In contrast to calculations in the frequency domain, no Fourier Transform or the like is required, but only relatively local operations in the time domain. Thus, hardware requirements can be reduced.
[019] Additionally, this method allows estimating, for example, the direction of a fault even if the fault is located close to the relay or the substation, known as a 'proximity fault'. The direction of such failures is difficult to estimate by using a conventional voltage-based method due to the inlet voltages at the measurement site tending to zero. Since the above aspects depend on a current measurement, there is no such problem in this case.
[020] In addition, the above allows the selection of a phase angle sensitivity independent of a current measurement sample rate. In particular, a phase angle sensitivity can be obtained that is less than the normal phase change between two current measurements (sampling angle). Brief description of the Figures:
[021] Details will be described below with reference to the figures, in which: Figure 1 shows a power distribution system that includes a measurement unit and a fault direction indicator device according to a modality; Figure 2 shows a current phasor diagram useful for understanding aspects of the invention; Figure 3 shows a time diagram by current useful to understand aspects of the invention; Figure 4 shows the measurement unit and the fault direction indicator device of Figure 1 in greater detail; Figure 5 shows a section of the decision logic of a fault direction indicator device according to a modality in greater detail; Figures 6a to 6d show current time diagrams that illustrate a method for determining the direction of failure according to an embodiment of the invention; Figures 7, 8 and 9 show additional current time diagrams that illustrate respective methods for determining the direction of failure according to modalities of the invention; Figure 10 shows an energy distribution system that includes a circuit breaker according to an embodiment; Figure 11 shows a section of additional decision logic for a fault direction indicator device according to an embodiment of the invention; and Figure 12 shows a measurement unit and a fault direction indicator device according to an additional embodiment of the invention. Detailed Description:
[022] Reference will now be made in detail to various modalities, one or more examples of which are illustrated in each figure. Each example is provided as an explanation and should not be considered as a limitation. For example, the features illustrated or described as part of a modality can be used or in conjunction with any other modality to obtain yet another additional modality. The present disclosure is intended to include such modifications and variations. In particular, the examples below refer to a fault direction indicator device. However, the methods described in this document can also be used in other protection functions (other than steering estimation).
[023] Within the following description of the drawings, the same reference numbers refer to the same or similar components. Generally, only the differences with respect to the individual modalities are described. Unless otherwise specified, the description of a part or aspect in one modality also applies to a corresponding part or aspect in another modality.
[024] In this document, when reference is made to a current value measured at a specific time or to a current value measurement in the time domain, such terminology implies that a time can be assigned to such a measurement, but not necessarily that the measurement is completely local in time. For example, the measurement can be obscured or time or it can include information obtained in other times, as long as a specific time can still be rationally assigned to the measurement (for example, a median time). For example, measurement data in the time domain can be obtained by processing a time-dependent measurement through a low-pass filter to eliminate high frequency noise.
[025] Furthermore, if it is stated that pre-failure and post-failure signals are transmitted, it does not necessarily imply that a distinction between pre-failure and post-failure signals would be known at the time of transmission. Such a distinction can also be made at a time after transmission, for example, after signal processing or after obtaining additional information from other sources. Device: Overview
[026] Figure 1 shows a power distribution system 1. In this document, transmission line 10 connects a power supply 2 (for example, a distributed generation source bus) to an electrical network 4, such as to supply the mains 4 from the power supply 2. Additionally, a measuring unit 20 is connected to the transmission line 10 at a measuring location 12. In relation to the measuring location 12, the transmission line is divided into an upward or reverse flow, portion (source side 2 between the source and relay) and a downward or direct flow, portion (electrical side 4 between the relay and line or electrical network). As described above, in smart power grids, the direction of energy flow can change over time, but "forward" and "reverse" can still be defined in relation to the flow of current energy.
[027] The measuring unit 20 is adapted to measure a current flowing in the transmission line 10 at the measuring location 12. A fault direction indicator device 30 receives a current signal that indicates the current measured from the unit measurement 20 and has the functionality to indicate a direction of a fault in a transmission line 10 from the current data, that is, to indicate whether the fault occurred in the reverse direction or in the direct direction in relation to the measuring location 12 .
[028] The measuring unit 20 comprises a current sensor to measure the current at the measuring site 12 of the transmission line 10. It does not comprise any voltage sensor. The measurement unit 20 is operationally coupled to the fault direction indicator device 30 (more precisely, to the input section 32 of the same shown in Figure 4 below) to transmit a current signal obtained from the current measurement to the device fault direction indicator 30 (for input section 32).
[029] As will be described in greater detail below, the fault direction indicator device 30 has the functionality to display directional information by using only the current data provided from the measurement unit 20 without any reference voltage. This results in a major cost advantage due to the fact that there is no need for a voltage sensor in the measurement unit 20. Since a common power distribution system requires many relays like the one shown in Figure 1, the overall cost advantage can be significant.
[030] Generally, the configuration will be more complex, for example, when the transmission line 12 is not directly connected to the upstream power supply 2, but is connected via a bus of a more complex network. Similarly, the downward flow configuration can be more complex. In addition, for simplicity, only a single phase line is shown. Generally, the network will have more phases (normally, three phases). The case of more than a single phase line will be further described below.
[031] Now, with reference to Figure 4, the fault direction indicator device 30 of Figure 1 is described in more detail. The fault direction indicator device 30 has an input section 32 and a decision logic section 36. Input section 32 is adapted to receive transmission line data, that is, data related to the transmission line and, more particularly, to the current signal of the measuring unit 20 without receiving any voltage signal.
[032] Therefore, the transmission line data received by input section 32 consists of the current signal and possibly other different voltage data, but does not include any voltage data or, for example, mixed voltage-current data. In other words, the transmission line data is free of data that results from a voltage measurement.
[033] The decision logic section 36 is operationally connected to the input section 32 to receive the transmission line data (which also includes the case of data processed from the transmission line data). The decision logic section 36 comprises a first fault direction determination program to determine the fault direction from the transmission line data and to output the determined fault direction as a first fault direction indicator. Fault Direction Determination Program: General Introduction
[034] In the following, the decision logic section 36 and, more particularly, the first fault direction determination program will be described in more detail. The program's task is to extract the direction information from the transmission line data, that is, especially from the current signals in the event of a failure. With the algorithms described below, the direction of the fault is detected from current measurements without the use of voltage signals. Underlying Model:
[035] Now, before the decision logic is described in detail, the model according to which the fault direction can be derived from the current will be described only with reference to Figures 1 to 3. Figure 1 shows two faults of the power transmission line 10, a downstream failure F2 and an upstream failure F1.
[036] In the case of the F1 upstream fault, the fault current IF1 flowing from the mains 4 to the F1 fault is: IF1 = V4 / Z4-F1 (1), where V4 is the mains voltage electrical 4 and where Z4-F1 is the impedance between electrical network 4 and the fault location of the F1 fault. (Here, all quantities are CA quantities given as phasors, that is, complex numbers). Similarly, in the case of a downstream flow fault F2, the fault current IF2 flowing from source 2 to fault F2 is: IF2 = V2 / Z2-F2 (2), where V2 is the voltage at source 2 and where Z2-F2 is the impedance between source 2 and the fault location of the F2 fault.
[037] The impedances Z4-F1 and Z2-F2 are not exactly known and may differ from each other. However, because line 10 is generally almost purely inductive with negligible resistance and capacitance, impedances Z4-F1 and Z2-F2 are almost purely imaginary with a negative imaginary component.
[038] Now, if Ipre is the pre-fault current from source 2 to mains 4, then the total post-fault current I1 in the event of an upstream failure F1 is Il = I pre - IF1 = Ipre - V4 / Z4-F1 (3).
[039] Similarly, the total post-fault current I2 in case of downstream flow failure F2 is I2 = Ipre + IF2 = Ipre + V2 / Z2-F2 (4).
[040] Please note the difference in the signal which is due to the fault current IF1 being directed in the opposite direction to the pre-fault current (from mains 4 to fault F1), where the fault current IF2 is directed in the same direction as the pre-fault current (from source 2 to fault F2).
[041] This signal difference is visible in the current phasor diagram in Figure 2. Here, the current represented as a complex number in the complex plane, jumps from Ipre to I1 or I2 as given in Equations (3) and (4) , in the event of an upward flow failure or downward flow failure, respectively. Here, the short-circuit current phasors -IF1 and IF2 over which the current phasor can jump can have mutually opposite signals due to the difference in signal in Equations (3) and (4) and due to Z4-F1 and Z2- F2 are both imaginary with a negative imaginary component. Thus, the phase angle of the post-fault current (I1 or I2) in relation to the pre-fault current Ipre has a phase change depending on and indicating the fault direction: For example, a positive phase angle change may indicate failure in the upward flow direction, while a negative phase angle change may indicate failure in the downward flow direction. Thus, it is possible to determine the direction of the post-fault current (forward and reverse / reverse) with respect to the Ipre only, without requiring any bus voltage. Therefore, the current alone contains enough information to determine the fault direction, that is, the information contained in the phase change of the current during the fault.
[042] Figure 3 is a diagram showing a current idealized as a function of time in the event of a fault in a fault time 81. The pre-fault current before fault time 81 is a sinusoidal shaped AC current with AC cycle or AC period T. After the fault, the post-fault current is again a sinusoidal-shaped AC current, but with a greater magnitude and, more importantly here, with a phase shift ΔΦ in relation to the pre-fault current . In other words, whether the pre-fault current can be described by dependence on time; ■ Í, then the post-fault current can be described by a time dependency c - Io - el (wt + Δ <p), where c is a real number and a> = 2π / T is the frequency, T being the CA period. This phase shift ΔΦ leads to a deviation in the time domain 81 ’of the current. This time deviation 81 ’has the magnitude Δt = Δcp / co = 5 (Δ ^ / 2π) ^ T. As shown in Figure 3, due to the phase shift ΔΦ, the periodic current curve after the fault 81 is shifted by the time deviation Δt (reference signal 81 ’) in relation to the current before the fault 81. Basic algorithm of the decision logic section:
[043] To determine the fault direction, the inverse problem of the model discussed above must be solved: The problem is to extract the phase shift from some, possibly with noise, current data, so that the fault direction can be determined based on the phase shift. A possible algorithm is described below with reference to Figures 6a to 6d. In Figures 6a and 6c a negative phase shift that indicates a direct failure is shown, where in Figures 6b and 6d a positive phase shift that indicates a reverse failure is shown.
[044] According to the algorithm, currents are continuously measured by a measurement unit 10 at the measurement site 12 (see Figure 1) also during normal operation. If a feeder protection system such as a current-only protection device, for example, from ABB is used as the unit of measurement, such a system continuously monitors the AC properties of the current and adapts the sampling frequency such that the number of samples per AC cycle corresponds to the sampling rate. Alternatively, a fixed sampling frequency can also be used for sampling, the frequency being based on, for example, a clock signal. In Figures 6a to 6d, current diagram 80 is shown as a function of smooth time, which corresponds to a very high sample rate. In the case of a lower sample rate, this soft current function would be replaced by a set of discrete data points similar to the data points in Figure 7.
[045] During operation, zero crossing times are determined, that is, times in which the current changes its signal. In Figures 6a to 6d, these zero crossing times are denoted as t0, t1 and t2. Here, t0 and t1 are obtained during normal operation, that is, before a fault 81; and t2 is obtained after fault 81. The zero crossing times t0, t1, t2 are obtained as times between two subsequent current measurements In and In + 1 (measured at times tn and tn + 1) which have the opposite sign. The zero crossing time can then be obtained, for example, as (tn + tn + 1) / 2 or, more precisely, by triangulation as tn - (tn + i - tn) • In / (In + i - In).
[046] In the event of a fault, indicated by reference signal 81, a fault signal is emitted by the feeder protection system and received by the fault direction indicator device. The fault can be detected, for example, by the current (in any phase) exceeding a limit value. According to a possible modality, at the moment of the failure or in a short period after the failure, a start command is issued. If the fault persists for some time, that is, if the current still exceeds the limit after a few AC cycles (say, two AC cycles), an excursion command is issued that causes a part of the power distribution system to be disconnected. Alternatively, the excursion command can also be issued beforehand if the current exceeds a higher additional limit. The start and excursion signals are generally emitted from, for example, a feeder protection system in response to the current exceeding a threshold value or some other event that indicates failure.
[047] The fault direction indicator device shall emit directional information at the time of the excursion command that is normally issued after the excursion interval. That is, an "excursion" command is issued in a few cycles (say, in n cycles with n> 1 or even n> 2) after the "start" eating or the failure event. In particular, the "excursion" command must be issued after n = 2 cycles after the detected fault event or after the "start" command.
[048] Therefore, when the excursion command is issued or just before the excursion command is expected to be issued, the fault direction indicator device has a number of crossing times at pre-failure zero, for example, t0 and t1, available and at least one crossing time at zero post-failure t2. From these times, the decision logic section calculates a zero crossing time interval with no faults 84, defined as the time intervals between two zero crossing times without neighbors between times t0 and t1. Alternatively, the zero crossing time interval without faults 84 can be obtained by averaging several of such time intervals before a failure, for example, the last five time intervals. Alternatively, time slot 84 can be obtained from an external source, for example, an AC current generator with half the AC period.
[049] Additionally, the decision logic section calculates a zero crossing time interval of fault 82, defined as the time intervals between the two zero crossing times neighbors t1 and t2 that have fault 81 between them. . The zero crossover time interval of fault 82 is an indicative deviation parameter because it contains information about the current time deviation at fault time 81: If the zero crossing time interval of fault 82 is greater than the zero crossing time interval without faults 84, as in Figures 6a and 6c, then the time deviation is positive, which indicates a negative phase shift. If, on the other hand, the zero crossing time interval of failure 82 is less than the zero crossing time interval without faults 84, as shown in Figures 6b and 6d, then the time deviation is negative, which indicates a positive phase shift.
[050] Then the decision logic section extracts this time deviation information by comparing the zero crossing time interval of fault 82 to the zero crossing time interval of failure 84, that is, the corresponding time interval in which a time deviation is absent. For this purpose, the decision logic section calculates a deviation direction parameter that indicates the direction of time deviation. For example, this deviation direction parameter can be a difference between time intervals 82 and 84, optionally divided by time interval 84. Then, by the sign of the deviation direction parameter, the deviation direction is established: For example , a positive sign can indicate a positive deviation (the zero crossover time interval of failure 82 is greater than the zero crossover time interval without failure 84) and a negative sign can indicate a negative deviation (the time interval zero crossing fault 82 is less than the zero zero crossing time interval without fault 84).
[051] In addition, the magnitude of the deviation direction parameter can indicate how significant the difference is between the zero zero crossing time interval 82 and the zero zero crossing time interval 84 and thus how reliable the drift information is determined.
[052] As discussed above with reference to Figures 1 to 3, the direction of deviation allows to indicate the direction of failure. According to the above, the decision logic section establishes the fault direction parameter based on the calculated deviation direction parameter. For example, a positive shift direction parameter that indicates a negative phase shift can indicate a direct failure and a negative shift direction parameter that indicates a positive phase shift can indicate a reverse failure.
[053] More generally, the decision logic section can determine the fault direction parameter by comparing the deviation direction parameter OD to a limit value. According to the example above, a direct fault will be determined if OD> 0 and a reverse fault will be determined if OD <0. In practice, a lower limit number ε is used as a limit and a direct fault will be determined if OD> ε and a reverse fault will be determined if OD <-ε. A neutral fault (indicating an unknown fault direction) will be issued if | OD | <ε. Thus, for situations in which the OD deviation direction parameter is close to zero so that its signal cannot be reliably determined, the generation of a potentially fallible signal will be avoided. The determined fault direction (direct, reverse or neutral) is then emitted.
[054] With respect to the sign of the deviation direction parameter, it is noted that although the sign indicates the fault direction, the assignment of a particular signal (positive or negative) to a particular fault direction (direct or reverse) depends on a number of line parameters, as well as signal conventions, so there may be situations in which a direct fault is expected if OD <0 and a reverse fault is expected if OD> 0.
[055] Figure 7 is a current-time diagram similar to the diagrams in Figure 6c. However, in Figure 7 instead of an idealized current as in Figure 6c, more realistic sampled current data with a non-zero sample rate is shown. As in Figure 6c, the negative phase shift at fault 81 is clearly visible. As in Figure 6c, this negative phase shift leads to a greater than normal fault zero crossing time interval 82. Therefore, the fault direction can be extracted as described above.
[056] As an additional difference with respect to Figure 6c, it can be seen that a DC current component is present due to the fault, which displaces the total current curve towards negative values. Consequently, the smaller half-cycles (for example, half-cycle between crossings at zero t1 and t2) are additionally increased in length and the upper half-cycle (for example, half-cycle between crossings at zero t2 and t3) is decreased additionally. Therefore, the DC current leads to an additional change in time interval 82 that is independent of a time deviation from the current and can therefore introduce errors.
[057] The problem associated with the DC current can be reduced by identifying, rather than zero crossings, some other periodically recurring characteristic of current data 80. For example, a maximum, a minimum or a greater gradient of current data can be selected. These periodically recurring characteristics of the current data may be less dependent on the additional DC current.
[058] Alternatively, the DC current can be corrected by displacing the current curve vertically in such a way as to deflect the effect of the DC current. For this purpose, the decision logic section calculates the average DC current over a period (for example, from time t1 to t3) by summing the current values sampled during this period and dividing the sum by the number of sampled currents . Then, the average DC current is subtracted from each of the current values.
[059] Figure 8 is a current-time diagram similar to the diagram in Figure 6a that illustrates a situation in which the phase shift occurs close to the zero crossing in such a way that multiple zero crossings are generated at times t1, ta , Also.
[060] According to one modality, the algorithm is modified as follows in order to produce correct results in this type of situation: The decision logic section checks for multiple (two or more) zero crossings of short intervals that occur in a short time interval less than a predetermined timeout. The time limit is a little less than a period T, for example, a period multiplied by a factor of 0.3 or 0.2 or 0.1 or even less. If the decision logic section finds such multiple intersections at zero short intervals (here: t1, ta, tb), then it checks whether multiple intersections at zero are an odd number. If not, then the decision logic section determines the nearest additional zero crossover and includes this additional zero crossing over multiple short interval zero crossings in order to obtain an odd number. Subsequently, the decision logic section checks whether a failure is observed during the short time. If so, the multiple zero-crossing at short interval t1, ta, tb are replaced by their lower limb t1 and the zero-crossing time interval at fault 82 is calculated as starting with t1. The other zero crossings of the short interval ta, tb are then ignored. Alternatively, the last interval tb can be taken and the zero crossing time interval of failure ending with tb.
[061] In the event that no fault is detected near such multiple crossings at zero short intervals, then this may be due to noise in the current data. In this case, either the time intervals ending with zero intersections of the short interval can be ignored as fallible when calculating the zero crossing time interval without fail 84 (see Figure 6a to 6d) or the zero crossing time of medium can be used and the other times t1, tb can be ignored.
[062] Therefore, as a general aspect, the decision logic section monitors whether the current data contains at least two of the periodically recurring characteristics in times close to the failure time 81 than a predetermined limit; and, in this case, it ignores at least one among at least two periodically recurring characteristics. In particular, the decision logic section obtains an odd number of the periodically recurring characteristics and selects only one of the periodically recurring characteristics and ignores the others.
[063] Figure 9 is a current-time diagram in which yet another modality is illustrated. According to this modality, the decision logic section first determines a length of period 85. For example, the length of period 85 can be determined as twice the zero crossing time interval without fail 84, where the interval zero crossing time without faults 84 can be determined as above or according to a similar method (for example, the duplicate can be determined by using the times of penultimate crossings at zero neighbors). Alternatively, period length 85 can be obtained from an external source, for example, an AC current generator.
[064] The decision logic section then calculates a numerical time integral (that is, the sum or other numerical approximation of a current time integral) from the current data. The integral limits are chosen such that the integral is taken over the current integration time interval being the normal length of period 85 or a multiple of the integral of the same; and that fault 81 is included in the integral. In Figure 6, the integral is taken from the last crossing at zero before fault 81 for a period length. The integral can be represented by the dotted area 86 between the time axis and the positive portion of the current curve minus the dotted area 87 between the time axis and the negative portion of the current curve.
[065] This integral is an indicative deviation parameter that depends on the deviation as follows. As seen in Figure 9, the current curve data after fault 81 is shifted to the right due to the positive deviation in the fault time 81. The deviation therefore leads to an increase in the area of positive current 86 and a decrease in the negative current area 87. Therefore, a positive deviation is indicated by a positive integral.
[066] In the event that the fault is in a negative current region instead of the positive current region 86 shown in Figure 9, then a positive deviation would be signaled by a negative integral. Therefore, a deviation direction parameter is obtained by multiplying the integral described above by the current signal during the fault.
[067] An integral that indicates an absence of a time deviation would ideally be zero, since in the absence of a deviation the integral would be expected to be zero or close to zero, that is, less than a predetermined limit ε. Thus, from the deviation direction parameter, that is, from the integral with the signal being adapted as described above, the fault direction parameter can be calculated in analogy to the above description with reference to 6th to 6th. The method of Figure 9 can, in some cases, be more robust than the zero crossing method with respect to noise since it depends on a sum of many measurements by which some noise effects are canceled. In a variation of the method, the DC current can be compensated in the same way as described in relation to Figure 7.
[068] Therefore, as a general aspect of the invention, the deviation parameter is a numerical time integral of current data within a time interval that includes the failure time. The time interval can be an integral multiple of a CA period or a parameter related to the CA period, for example, a CA period. A parameter indicative of non-deviation can be zero or a comparable integral of current data within a time interval that does not include the time of failure. The deviation direction parameter can be based on the deviation parameter multiplied by a signal, especially by a signal that depends on the current data at the time of failure. Fault direction determination program: Three Phase Calculation
[069] In the discussion above, only a single line system has been described. In reality, most power distribution systems have three phases of current. For such a three-phase system, a single representation for all currents in all three current phases can be used. Therefore, according to one embodiment, the current signals from all three current phases I1, I2, I3 are combined into a combined current signal. Depending on the single representation, the positive sequence component or positive phase sequence current (PPS) signal IPPS = 1A + etwT / 3 • i2 + e2 '^ r / 2. /., can be used. Then, the combined current signal can be evaluated, as described above, by calculating crossings at zero or other parameters that indicate deviation based on the combined current signal. Therefore, the same analysis as mentioned above for the case of a single line can be performed and the method described above can be applied with the current signal being the positive sequence component or some other combined current signal.
[070] However, in practice this approach is not always stable and can result in a false determination of the direction of failure. Especially when using the positive phase sequence component, the phase angle is influenced, for example, by the frequency divergence, inherent imbalances in the three-phase line input and measurement noise. Consequently, the angle of the current PPS signal is less stable than desired.
[071] Therefore, according to an additional modality, the parameters that indicate deviation and, based on these, the deviation direction parameters are calculated for each current phase individually as described above instead of being calculated for a current signal. Combined. As a result, the deviation direction parameters for the individual current phases are more stable than the combined current signal. Then, the maximum of the three deviation direction parameters is taken and, by using the maximum, the fault direction parameter is obtained as described above. There are other methods to combine the indicative deviation parameter, for example, by taking into account the median of the parameters that indicate deviation, for example, the zero crossing time interval of fault 82, for each phase.
[072] According to an alternative modality, three individual current fault direction parameters are calculated, one for each current phase p. Then, a majority decision algorithm or unanimous vote is used to determine the failure direction parameter to be issued. Current Limit
[073] The above method depends on the pre-fault current as the polarizing quantity, instead of, for example, the voltage. Therefore, to judge the direction, the baseline information, the relay must see pre-fault current valid for a certain duration to obtain reliable zero crossings or other periodically recurring characteristics of the current data. If there is no valid pre-failure current of sufficiently stable phase oscillations, the results would be less reliable. Therefore, the magnitude of the fundamental component of the input signal (current) is compared to a current limit. If the current is not above the current limit for at least two cycles, direction information is not output. Instead, a "neutral" signal is issued that indicates inconclusive directional information.
[074] As a limit, 10% of the current rating can be chosen. Therefore, the magnitude of the fundamental component of the current must be above 10% of the nominal current value for at least two cycles, otherwise the "neutral" signal is emitted. Such types of cases can occur when, for example, the device is switched on during a fault condition, that is, on a case of being switched on to a fault state. Fault direction determination program
[075] Figure 5 shows a signal processing sequence for a fault direction determination program of the decision logic section 36 according to the above algorithm. First, current data in the time domain is received from the input section for each of the three current phases (arrows 33). Then, for each current phase, a deviation direction parameter calculation module 43 calculates the deviation direction parameter which indicates the time deviation direction for the current phase. For example, the deviation direction parameter can be the difference between the zero zero crossing time interval 82 and the zero zero crossing time interval 84 shown in Figures 6a to 6d and 7 and can be calculated from according to the method described above.
[076] Then, a maximum selection section 44 selects the maximum of the deviation direction parameters for each current phase and the maximum deviation direction parameter is transmitted to a direction logic 46 and optionally to a limit comparator 48 Direction logic 46 determines, based on the maximum deviation direction parameter, the fault direction parameter (forward or reverse or optionally neutral) as described above.
[077] According to one modality, the limit comparator 46 receives current values compared to one or more fault limit (s). Based on the comparison, the limit comparator 46 then determines whether an "interrupt" signal should be sent. Possibly, if only an intermediate limit is reached, the limit comparator 48 issues a "start" command that initiates a cycle wait signal executed by a cycle wait module 47 and the limit can be monitored again after the waiting for decision on the "interrupt" command.
[078] In the case of an interrupt command, not only is the interrupt command sent, but also the fault direction parameter determined by direction logic 46 is sent by a relay status module 49 as a directional signal 37.
[079] Some of the steps above can be performed continuously, even in the absence of a failure. In addition, a failure time indicator section (not shown) can be provided to determine the time of a failure and transmit the failure time to the deviation direction parameter calculation module 43. Fault direction determination program: Two programs
[080] In an optional mode, decision logic 36 may additionally comprise a second fault direction determination program in addition to the (first) fault direction determination program described above. The second fault direction determination program determines the fault direction from the current data in addition, but according to a different algorithm. Then, the second fault direction determination program issues a second fault direction indicator. The first fault direction determination program and the second fault direction determination program can be run either on the same hardware (for example, in parallel) or on different pieces of hardware.
[081] For example, the second fault direction determination program can determine the fault direction from an additional algorithm as described in EP Application No. 10172782.4 and especially with respect to its description of Figures 5 and 6 thereof. This additional algorithm is described below:
[082] According to the additional algorithm, currents are continuously measured by a measurement unit 10 at measurement location 12 (see Figure 1) also during normal operation. If a feeder protection system such as a current-only protection device, for example, from ABB is used as the measuring unit, such a system continuously monitors the AC properties of the current. In addition, a protection device is generally capable of representing the current as a complex number with a real part representing the measured current and the imaginary part representing phase information. The current values of the complex number are then transmitted, as a current signal, to the fault direction indicator device. The fault direction indicator device stores the complex number current values in a temporary storage for some time. Here, the current values are referred to as , where j is an index that represents the sample number, some j smaller being the oldest sample and some j larger being the more recent sample.
[083] Next, k will indicate the index that corresponds to a time close to the failure event, ideally the index that corresponds to the time of the last sample before the failure event. Therefore, the currents Ij.J <K,, represent the pre-fault currents before the fault and the currents Ij.J> K, represent the post-fault currents.
[084] When the excursion command is issued or shortly before the excursion command is expected to be issued, the fault direction indicator device has a plurality of available fault current values, that is, complex number values of the sampled current measurements taken after the failure. These post-fault current values are also referred to as
with 1 <i <n * N, N being the sample rate.
[085] From the post-fault current values, the decision logic section then determines a plurality of phase difference values, that is, the phase difference values
between the i-th values of post-fault current
and the respective i-th values of pre-fault current
. Here, the i-th values of pre-fault current
are defined as samples taken in an integer number m of cycles before the i-th values of post-fault current
corresponding. So if
then,
. Here, the parameter m indicates how many cycles must be between the i-th pre-fault and post-fault currents, and can, in principle, be chosen freely with m> n. Usually m = n is chosen. In one example, m = n = 2, therefore, the pre-fault current value
is the current sample done two cycles before the post-fault current value
corresponding. The complex phase difference
between two complex numbers a and b is calculated as
In addition, the phase difference values
they can be calculated using, for example, Fourier analysis or other methods.
[086] After obtaining the plurality of phase difference values
the decision logic section accumulates them in an accumulated phase difference parameter _ . This is usually done by adding the phase difference values according to the formula:

[087] The decision logic section then determines a fault direction parameter by comparing the accumulated phase difference parameter to a limit value. For example, a reverse fault will be determined if ΔΦ> 0 and a direct fault will be determined if ΔΦ <0. In practice, a small limit number ε is used as a limit and a neutral fault (indicating an unknown fault direction) will be determined. issued if | ΔΦ | <ε. There may also be situations in which a reverse failure is expected if ΔΦ <0, and a direct failure is expected if ΔΦ> 0.
[088] Figure 11 shows a signal processing sequence for a fault direction determination program of the decision logic section 136 according to the additional algorithm above. First, the current signal comprising the complex number pre-fault and post-fault current values is received from the input section (arrows 133). Then, a phase angle extraction module 141 determines the phase angle of the respective current values. The phase values can be computed, for example, by Fourier analysis or other methods. In particular, if the arcotangent function is used as described above, this function can be implemented by a table query in order to speed up the computation. The phase angles are stored in a phase angle storage 142. In the event of a failure, the N * n pre-failure angles are available and the N * n post-failure angles are or will soon be available. Thus, a phase angle subtractor 143 subtracts the i-th post-failure angle from the i-th pre-failure angle and thus determines the i-th phase difference value
for i = 1 ... n * N. Then, a maximum selection section 144 selects the maximum of the phase difference values for each current phase and the maximum phase angle difference is stored in a storage section.
[089] The steps above or some of the steps above can be performed continuously, even in the absence of a failure. In addition, a failure time indicator section 148 can use the maximum phase difference to determine the time of a failure in the case where a start command is issued, for example, by comparing the maximum phase difference of each sample ia limit value or by obtaining the maximum phase difference.
[090] After the failure, an accumulator 147 accumulates the maximum phase difference for n post-failure cycles, for example, 2 post-failure cycles, for example, by the sum of the phase differences, to obtain the phase difference parameter accumulated _ã. So, by comparing
at a limit value, a determination section 149 determines the direction of failure as described above.
[091] As shown in Figure 12, the algorithms in Figure 5 can be combined as follows with an additional algorithm such as the algorithm described with reference to Figure 11: The fault direction indicator device 30 has an input section 32 (as in Figure 4) and two decision logic sections 36 and 136. The input section transmits current data to both decision logic sections 36 and 136. Decision logic section 36 is adapted to perform any method described in the present document, in particular any method according to claim 1 of the present application. The additional decision logic section 136 is adapted to perform any additional method described in this document that is different from the method performed by the decision logic section 36, in particular the method described with reference to Figure 11. The decision logic sections 36 and 136 issue respective fault direction parameters and, optionally, a parameter indicating the reliability of their calculation. In the case of the method of claim 1, such as a parameter indicating reliability can be the magnitude of the deviation direction parameter or an amount derived therefrom.
[092] The fault direction indicator device 30 further comprises a decision joining program 38 to determine a master fault direction from the respective fault direction parameters issued by decision logic sections 36 and 136. Then, the resulting determined master fault direction is issued by the decision joining program 38.
[093] In the event that the decision logic sections 36 and 136 are in mutual disagreement about the direction of failure, the decision union program 38 can determine the direction of failure as neutral or by weighting the decision, that is, by assigning of different weights to the first and the second fault direction indicator and when taking the result with the highest weighting into account. The weights can be determined by taking into account the parameters that indicate the reliability of the calculations in the decision logic sections 36 and 136. In addition, in the case of mutual disagreement (and possibly similar weights associated with each of the disagreing sides) , the decision splicing program can emit a neutral output which can, in a circuit breaker configuration, possibly lead to the switch disabling a larger portion of the network.
[094] The decision union above can be generalized to three or more sections of decision logic. The decision-making union program may include a (possibly weighted) voting routine.
[095] The use of more than one section of decision logic is particularly useful when different types of fault direction determination programs are used. Thus, for example, the second fault direction determination program can be programmed according to a learning-based algorithm or machine rule-based algorithm. Then, in the case of mutual agreement between the different approaches, the risk of an error is reduced and stability is increased. In addition, errors can be detected more easily due to even if a fault direction determination program issues an incorrect result, this error can be detected and overcome, or at least it will lead to a neutral output and not an incorrect output anymore. problematic. Relay / Circuit Breaker
[096] Although the fault direction indicator device 30 (see, for example, Figure 1) is useful in its own right, it is particularly useful when integrated with a monitoring system or a circuit breaker (relay) system. For this purpose, an optional communication section of the fault direction indicator device 30 allows it to transmit the determined fault direction (ie, the fault direction indicator that indicates, for example, a direct or reverse fault) to another unit of the power distribution network, for example, for a circuit breaker, for a control unit or for a supervision unit to supervise the transmission line 10.
[097] Figure 10 shows a configuration in which the power distribution system 1 includes a circuit breaker 50. The circuit breaker 50 is operationally coupled to the fault direction indicator device 30, possibly via a central control unit (not shown) ). Therefore, the circuit breaker can receive from the fault direction indicator device 30 at least one of the first, second and third fault direction indicators or some other fault direction information obtained therefrom, such as fault information. neutral possibility or exit. This output can then trigger circuit breaker 50 or the central control unit to take the appropriate action, for example, to cut the appropriate section, not the entire line 10. In the case of an "inconclusive information" output, a portion greater than the entire line 10 can be cut. Direction of energy flow
[098] In some embodiments, the decision logic section 36 (see, for example, Figure 1) further comprises an energy flow direction determination program to determine the energy flow direction from the line data transmission. The monitoring of the energy flow can be carried out at regular intervals or permanently, regardless of a failure.
[099] Additional energy flow information from the energy flow direction determination program can also be used to control circuit breaker 50 shown in Figure 10. The flow of power from mains 4 to source 2 is undesired , since the energy is thus wasted. Therefore, if this unwanted energy flow is detected (possibly for a predetermined time interval), circuit breaker 50 can be activated to interrupt the appropriate section in order to limit energy waste.
[0100] Thus, in this case, the device 30 can be described as an energy flow direction connection device to detect if there is an unwanted energy flow. This device is especially useful for distributed generation units such as solar / wind power systems. These units can stop producing, in which case the energy will start to flow in the opposite direction (from mains 4 to generator 2). From the point of view of the currents involved, this situation is similar to an upstream failure condition (as described above), except that there is no real failure. Thus, the directional device can detect this type of situation with the algorithms described in this document and activate circuit breaker 50 or issue a warning. Smart power grids:
[0101] In current networks, the delivery of energy occurs through the transmission of the electrical network (HV) through HV transformers to the electrical distribution network and through the distribution transformers to the LV and end users. This can also be called a "top-down" flow of energy from the main power plants through the various transmission networks to the power plug on the wall. The protection scheme for the power plant and the grid are made in accordance with the above. With the introduction of more distributed energy generation, mainly by alternative energies, the direction of the energy flow may, however, change under certain environmental conditions. For example, distributed units can sometimes act as power supplies that supply power to the grid and, at other times, consume grid power.
[0102] A known directional overcurrent function, with reference to voltage phases, cannot adapt or distinguish when the energy flow (or current at a given voltage phase angle) changes direction due to more energy being generated by the generation units distributed than is consumed in the power grid to be protected. The known directional overcurrent function is unable to adapt to the modified situation since the modified pre-failure condition (inverted energy flow) is not taken into account since the voltage phase has not been modified.
[0103] By using the pre-fault current as a reference for directional information according to a modality of the present invention, under fault conditions the protection function is enabled to adapt to the modified situation, that is, to the energy flow modified pre-failure. Thus, the function described in the patent application will always protect the network by "shutting down" the power supply by firing in the direct direction because the direct direction is always defined as the direct direction of failure from the point of view of the power supply current. .
[0104] For example, consider a first case in which the energy flows are in the normal direction of the central power supply for distributed units. Then, in the event of a fault, assume that the relay trips in the forward condition and locks in the reverse condition, the relay will isolate the main power supply from the fault location: The relay in the forward direction for failure trips, while the relay in the forward direction. reverse blocks. As the fault is still present, it may be that some energy is still fed into the fault, although the relay has previously blocked, from a distributed unit located after the fault. In this case, the current flow will change, since the distributed unit is feeding the fault. If the current is again overloading the set point, that is, activating an excursion command, the previously blocked relay will now trip since the fault is now in the direct direction of that relay. This is an example of how a protection system for currents can adapt to modified conditions and protect and isolate the source of the failure.
[0105] In a second case, the distributed units feed energy into the distributed network. In the event of a fault, the relay trips in the forward direction and locks in the reverse direction. In this way, the distributed unit is disconnected from the fault since the pre-fault current was in the direction of the HV mains connection (direct to the central power supply as seen from the mains). In addition, in this example, if the fault is still present after the distributed unit is disconnected, the power direction is reversed and the HV mains supply the fault. Thus, the blocking relay now sees a modified pre-fault current: Now this relay will also see a direct current flow and will trip immediately so that the fault becomes completely isolated. General aspects of the invention
[0106] The above method can be varied in some ways. In the following, some general aspects of the invention will be described.
[0107] For example, although some methods have been described above based on zero crossings, alternatively some other periodically recurrent characteristics of the current can be used in an analogous manner. Therefore, the indicative deviation parameter is extracted as follows: A first time and a second time are determined by the identification of two neighbors of the periodically recurring characteristics of the current data, in such a way that the failure time is between the first time and the second half. The indicative deviation parameter (82) is then, for example, the time interval between the first time and the second time.
[0108] Such periodically recurring characteristics can be a maximum, a minimum or a greater gradient of the current data and / or its magnitude. Some of these characteristics have a full AC cycle period and some half AC cycle. This can have a consequence for the time within which the fault direction can be determined. Generally characteristics with an AC half-cycle period, such as zero crossing and characteristics based on the magnitude of the current allow for faster determination of the fault direction.
[0109] According to an additional aspect, According to an additional aspect, the limit value corresponds to a deviation that is less than the sampling rate of the phase angle.
[0110] According to an additional aspect, the transmission line comprises a plurality of phases, especially three phases and the method comprises measuring the current in each phase; and determining parameters that indicate respective deviations for each of the plurality of phases separately. According to an additional aspect, from the three phases, a maximum of parameters that indicate deviation is selected. Here, the maximum refers to the absolute value. According to an additional aspect, a magnitude of the current values is compared to a limit value. In case the magnitude of a respective one among the current values is less than the limit value, at least some of the parameters that indicate deviation are discarded and / or a "neutral" command is issued.
[0111] According to an additional aspect, the measurement includes measuring a current, but not measuring the voltage of the transmission line. According to an additional aspect, the fault direction parameter is obtained as "direct fault" or "reverse fault" based on the signal of the accumulated phase difference parameter. According to an additional aspect, the fault direction parameter is obtained as "neutral" if the absolute value of the deviation direction parameter is less than a limit value.
[0112] According to an additional aspect, an additional method for obtaining a fault direction parameter is taken into account. The additional method includes the following: transmitting a current signal that indicates the measured current to a decision logic section, the current signal comprises a plurality of pre-fault current values and a plurality of post-fault current values; determine, by the decision logic section, a plurality of phase difference values that indicate the respective phase differences between the respective among the pre-fault current values and the respective among the post-fault current values; accumulating the plurality of phase difference values in an accumulated phase difference parameter; obtain the fault parameter by comparing the accumulated phase difference parameter to a limit value; and issue the determined fault parameter.
[0113] In accordance with an additional aspect, a fault direction indicator device according to claim 10 is provided.
[0114] According to an additional aspect, the fault direction indicator device comprises the measuring unit, the measuring unit comprising a current sensor to measure the current at the transmission line measurement site, but no sensor voltage, where the measuring unit is operationally coupled to the input section to transmit the current signal obtained from the current measurement to the input section.
[0115] In accordance with an additional aspect, a directional overcurrent relay comprising a fault direction indicator device as described in this document is provided. The relay additionally comprises a circuit breaker operationally coupled to the fault direction indicator device to receive, from the fault direction indicator device, the fault direction parameter, possibly in a processed form, that is, a parameter that includes information from the fault direction parameter.
[0116] In an additional aspect, any of the devices described in this document are used in an external environment and / or smart grid power distribution network, that is, a power distribution network with distributed units, the electrical network being adapted in such a way that the distributed units can feed energy into the electrical network during normal operation.
[0117] Although the foregoing is directed at modalities, other modalities and additional modalities can be developed without departing from the scope determined by the claims.

权利要求:
Claims (12)
[0001]
1. Method for determining a failure direction parameter of a failure in an AC transmission line (10) of a power distribution system (1) in relation to a measurement location (12) of the transmission line (10) , the method comprising: - measuring, by means of a measuring unit (20), a time-dependent AC current from the transmission line (10) at the measurement site (12), thus obtaining current data in the time domain ( 80) indicative of the measured current, the measuring unit (20) comprising a current sensor to measure the current at the measuring site (12) of the transmission line (10), but no voltage sensor; - transmitting the current data from the measuring unit (20) to a decision logic section (36); - obtaining a failure time (81) of the failure in the AC transmission line (10); - extracting, from the current data (80), a parameter indicative of deviation (82, 86, 87) indicative of a time deviation (81 ') of the current at the time of failure (81); - calculate a deviation direction parameter when comparing the indicative deviation parameter (82, 86, 87) to the indicative non-deviation parameter (84), where the indicative non-deviation parameter (84) indicates the absence of a deviation from current time between a first time and a second time; and - establish the fault direction parameter based on a signal from the calculated deviation direction parameter; CHARACTERIZED by the steps of: - identifying a first time (t1) and a second time (t2) by identifying a periodically recurring characteristic of the current data (80), so that the failure time (81) is between the first time ( t1) and the second time (t2), in which the periodically recurring characteristic is selected from the group consisting of a crossing of zero, a maximum, a minimum and a greater gradient of the current data; and where the indicative deviation parameter (82) extracted is a time interval between the first time (t1) and the second time (t2).
[0002]
2. Method, according to claim 1, CHARACTERIZED by the fact that the indicative deviation parameter (82, 86, 87) is selected from the list consisting of a time interval (82) that includes the failure time (81) and a numerical time integral of current data (86, 87) within a time interval (85) that includes the failure time (81).
[0003]
3. Method, according to claim 2, CHARACTERIZED by the fact that it additionally includes monitoring whether the current data contains at least two of the periodically recurring characteristics at moments closer to the failure time (81) than a predetermined limit; and, in this case, ignore at least one of the at least two periodically recurring characteristics.
[0004]
4. Method, according to any of the preceding claims, CHARACTERIZED by the fact that the step of extracting the indicative deviation parameter includes choosing integral limits of a current integration time interval so that the integration time interval current is a normal period length of the AC current or an integer multiple thereof; and calculating a numerical integral (86, 87) of the current data over the current integration time interval (85).
[0005]
5. Method, according to any of the preceding claims, CHARACTERIZED by the fact that the transmission line comprises a plurality of phase lines, the method comprising measuring the current in each of the phase lines; and determining a respective indicative deviation parameter (82, 86, 87) for each of the plurality of phase lines separately.
[0006]
6. Method, according to claim 5, CHARACTERIZED by the fact that it additionally includes selecting the deviation parameter (82, 86, 87) from the phase line for which a difference between the deviation parameter (82, 86 , 87) and the indicative parameter of non-deviation (84) is greater in magnitude.
[0007]
7. Method, according to any of the preceding claims, CHARACTERIZED by the fact that the measurement includes measuring a current, but without measuring the voltage of the transmission line (10).
[0008]
8. Method, according to any of the preceding claims, CHARACTERIZED by the fact that the fault direction parameter includes "direct fault", "reverse fault" and "neutral", the method additionally including comparing the magnitude of a difference between the deviation parameter parameter (82, 86, 87) and the non deviation parameter parameter (84) to a limit value and, if the magnitude of the difference is less than the limit value, issue a "neutral" command.
[0009]
9. Method, according to any of the preceding claims, CHARACTERIZED by the fact that the fault direction parameter is a first fault direction parameter, the method further comprising: - determining a second fault direction parameter from the current signal by a second fault direction determination program, wherein the second fault direction determination program includes receiving a current signal comprising complex number pre-fault and post-fault current values from a input section, determine a phase angle from the respective current values, determine a plurality of phase difference values between angles selected from among the phase angles, add at least some of the phase difference values to obtain a phase difference parameter accumulated phase, and determine the second fault direction parameter when comparing the accumulated phase difference parameter to a limit value; and - establish a master fault direction parameter from the first fault direction parameter and from the second fault direction parameter and issue the master fault direction parameter.
[0010]
10. Fault direction parameter indicating device (30) to indicate a fault direction parameter of a fault in an AC transmission line (10) of a power distribution system (1) in relation to a measurement location (12) of the transmission line (10), the fault direction parameter indicating device (30) comprising: - a measuring unit (20), the measuring unit (20) comprising a current sensor for measuring a current AC at the measurement site (12) of the transmission line (10), but without a voltage sensor, where the measurement unit (20) is operationally coupled to an input section (32) to transmit the current data in the time domain (80) obtained from the current measurement for the input section (32); - the input section (32) configured to receive current data in the time domain (80) indicative of a time dependent current measured by the measurement unit (20) at the measurement site (12); - a decision logic section (36) configured to determine the fault direction parameter based on current data in the time domain (80), - a deviation direction calculation subsection (46) configured to calculate a parameter deviation direction when comparing the deviation parameter parameter (82, 86, 87) to a non deviation parameter parameter (84), where the non deviation parameter parameter (84) indicates the absence of time deviation of the current between a first half and a second half; and - a fault direction parameter setting subsection (49) configured to establish the fault direction parameter based on a calculated deviation direction parameter signal; CHARACTERIZED by the fact that the decision logic section (36) comprises: - a fault deviation calculation subsection (43) configured to extract, from the current data (80), an indicative deviation parameter (82, 86, 87) indicating a time deviation (81 ') of the current in a fault time (81), in which the extraction of the indicative deviation parameter (82, 86, 87) includes identifying a first time (t1) and a second time (t2) when identifying a periodically recurring characteristic of the current data (80), so that the failure time (81) is between the first time (t1) and the second time (t2), and in which the deviation parameter (82) is a time interval between the first time (t1) and the second time (t2), in which the periodically recurring characteristic is selected from the group consisting of a crossing of zero, a maximum, a minimum and a greater gradient of current data.
[0011]
11. Device according to claim 10, CHARACTERIZED by the fact that said device is for use in an external environment and / or smart grid power distribution network.
[0012]
12. Directional overcurrent relay, CHARACTERIZED by the fact that it comprises a fault direction parameter indicator device (30), as defined in claim 10 and a circuit breaker (50) operationally coupled to the fault direction indicator device (30) for receive, from the fault direction parameter indicating device (30), the fault direction parameter.

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同族专利:

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公开号 | 公开日

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CN103250063B|2015-08-12|

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EP2628015B1|2014-06-25|

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EP2628015A1|2013-08-21|

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WO2012049294A1|2012-04-19|

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US9366715B2|2016-06-14|

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CN103250063A|2013-08-14|

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US20130221977A1|2013-08-29|

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BR112013008760A2|2020-09-01|

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法律状态:
2020-09-15| B06U| Preliminary requirement: requests with searches performed by other patent offices: suspension of the patent application procedure|

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2020-11-10| B25A| Requested transfer of rights approved|Owner name: ABB SCHWEIZ AG (CH) |

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2020-12-01| B25G| Requested change of headquarter approved|Owner name: ABB SCHWEIZ AG (CH) |

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2021-01-05| B09A| Decision: intention to grant|

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2021-02-23| B16A| Patent or certificate of addition of invention granted|Free format text: PRAZO DE VALIDADE: 20 (VINTE) ANOS CONTADOS A PARTIR DE 14/10/2011, OBSERVADAS AS CONDICOES LEGAIS. |

优先权:

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申请号 | 申请日 | 专利标题

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EP10187546|2010-10-14|

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EP10187546.6|2010-10-14|

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PCT/EP2011/067995|WO2012049294A1|2010-10-14|2011-10-14|Fault direction parameter indicator device using only current and related methods|

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