A method of determining a mode of operation of a protection device in a multi-phase power transmission system
Patent Information
- Application Number
- PCT/EP2026/054919
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2025-02-26
- Filing Date
- 2026-02-24
- Publication Date
- 2026-09-03
Smart Images
Figure EP2026054919_03092026_PF_FP_ABST
Abstract
Description
[0001] New PCT Patent Application Vossius & Partner based on IN 202511017034 Patentanwalte Rechtsanwalte mbB Hitachi Energy Ltd SiebertstraRe 3 Ref.: P240308W001 81675 Munchen Vossius Ref.: AL1042 PCT February 24, 2026
[0002] A METHOD OF DETERMINING A MODE OF OPERATION OF A PROTECTION DEVICE IN A MULTI-PHASE POWER TRANSMISSION SYSTEM
[0003] TECHNICAL FIELD
[0004] The present disclosure relates to a method of determining a mode of operation of a protection device in a multi-phase power transmission system, and a operation mode determination element for performing the method.
[0005] BACKGROUND
[0006] In a multi-phase power transmission system it is important to detect and remedy different kinds of faults, such as short-circuit faults between phases, and between one or more phases and ground, etc. Therefore, the transmission lines are monitored to protect them from harmful faults. Prior art solutions of fault protection typically utilize measurements of current or impedance. There are different kinds of fault protection, for instance distance protection, and differential protection. Further, each kind of fault protection may use several different modes of operation, which employs different quantities, such as magnitudes of phase currents, phase angle differences of currents or voltages, magnitudes of impedances, magnitudes of sequence currents, etc.
[0007] However, the growing diversity of power generating systems, with new types of renewables in addition to the traditional fossil fuel power plants, hydropower plants, and nuclear power plants and the introduction of power electronic devices, such as inverters, MMCs (Multi Modular Converters), super-capacitors, etc. set new requirements for the protection systems. It has shown that some modes of operation are more suitable for some kinds of power generating systems than other modes of operation. Control and protection principles currently used in electrical power systems, which are mainly based on the traditional behavior of synchronousgenerators are not fully applicable to power generation systems with power electronic devices. If a less suitable mode of operation is used, the risk of false fault detections, and associated unnecessary tripping of current breakers, and the risk of missing true faults will increase. When detecting a fault, depending on the position of the fault within the power transmission system, the character of the electrical quantities in the power transmission system may differ. Therefore, different modes of operation may be preferable to use depending on the position of the fault. If the mode of operation is fixed the risk of errors may become higher than if it would be possible to choose the most appropriate mode of operation.
[0008] SUMMARY
[0009] The present disclosure seeks to, at least partly, remedy the above discussed issues. To achieve this, a method of determining an operation mode for fault protection in a multi-phase power transmission system and an operation mode determination element as well as a computer program product, as defined by the independent claims, are provided. Further embodiments are provided in the dependent claims.
[0010] More specifically, there is provided, according to a first aspect of the present disclosure, a method of determining a mode of operation of a protection device in a multi-phase power transmission system, comprising:
[0011] - determining phase currents of the phases of the multi-phase power transmission system;
[0012] - determining sequence currents, comprising zero sequence current and negative sequence current, from the phase currents; - determining a zero sequence current decision value by means of a zero sequence current magnitude criterion and a zero sequence current magnitude ratio criterion, wherein the zero sequence current magnitude ratio criterion comprises a first magnitude ratio determined by means of a zero sequence current magnitude and a negative sequence current magnitude;- determining a negative sequence current decision value by means of a negative sequence current magnitude criterion and a negative sequence current magnitude ratio criterion, wherein the negative sequence current magnitude ratio criterion comprises a second magnitude ratio determined by means of the zero sequence current magnitude and the negative sequence current magnitude; and
[0013] - determining the mode of operation, within a group of several modes of operation, to be applied, by means of the zero sequence current decision value and the negative sequence current decision value.
[0014] By using a combination of magnitudes and magnitude ratios for the zero sequence current, and the negative sequence current, as specified above, it can be decided which mode of operation is preferred. Thereby, a less suitable mode of operation can be avoided.
[0015] It should be noted that for the purposes of this application, the term multi-phase means that the system has several phases of current / voltage, such as three phases or two phases, as readily understood by the person skilled in the art.
[0016] Moreover, for the person skilled in the art it would be understood that the multi-phase system is an alternating current (AC) system.
[0017] In an embodiment of the invention the zero sequence current magnitude criterion may comprise a comparison of the zero sequence current magnitude with a zero sequence current magnitude threshold, and the negative sequence current magnitude criterion may comprise a comparison of the negative sequence current magnitude with a negative sequence current magnitude threshold. By using the thresholds and setting them appropriately, like for example to set them to values related to specific grid codes or experiences and to obtain a more defined performance, the robustness and / or specific performance of the method may be increased.According to a further embodiment the first magnitude ratio and the second magnitude ratio may be the same. In other words, the same relation between the zero and negative sequence current magnitudes may be used for the zero and negative sequence current magnitude ratio criteria.
[0018] Furthermore, the zero sequence current magnitude ratio criterion may comprise that the first magnitude ratio is greater than a first magnitude ratio threshold, and the negative sequence current ratio criterion may comprise that the second magnitude ratio is less than a second ratio threshold.
[0019] In a further embodiment the zero sequence current magnitude criterion may comprise a combination of a first zero sequence sub-criterion that the zero sequence current magnitude is greater than a first zero sequence current magnitude sub-threshold, and a second zero sequence sub-criterion that the zero sequence current magnitude is greater than a second zero sequence current magnitude sub-threshold times a maximum magnitude of the phase currents. By taking the phase currents into account in this way a situation of one or more very large fault currents, which may produce or create a large absolute error from a small relative deviation, will not be influenced by an unwanted fulfillment of the first magnitude subcriterion and / or which may distort other calculations made by the protection device, can improve the final outcome of the operations performed by the protection device.
[0020] Furthermore, the negative sequence current magnitude criterion may comprise a combination of a first negative sequence sub-criterion that the negative sequence current magnitude is greater than a first negative sequence current magnitude sub-threshold, and a second negative sequence sub-criterion that the negative sequence current magnitude is greater than a second negative sequence current magnitude sub-threshold times a maximum magnitude of the phase currents.According to a further embodiment the group of several modes of operation may comprise determining a direction of a fault by means of one of current phase angles, delta values, the zero sequence current, the negative sequence current, and a transmission line impedance.
[0021] According to a second aspect of the present disclosure there is provided a operation mode determination element configured to determine a mode of operation of a protection device in a multi-phase power transmission system by performing the method described above.
[0022] Furthermore, according to a third aspect of the present disclosure there is provided a computer program product comprising instructions which, when the program is executed by a computer, cause the computer to carry out the method described above.
[0023] BRIEF DESCRIPTION OF THE DRAWINGS
[0024] The present disclosure will by way of example be described in more detail with reference to the appended drawings, which show example embodiments of the disclosure.
[0025] Fig. 1 illustrates a protection device comprising an embodiment of a protection element according to the present disclosure.
[0026] Fig. 2 illustrates an embodiment of the present method.
[0027] Fig. 3 is a diagram illustrating current ranges defined by the method.
[0028] DETAILED DESCRIPTION
[0029] The present disclosure will now be described more fully hereinafter with reference to the accompanying drawings, in which currently preferred embodiments of the disclosure are shown. This disclosure may, however, be embodied in many different forms and should not be construed as limitedto the embodiments set forth herein; rather, these embodiments are provided for thoroughness and completeness and fully convey the scope of the disclosure to the skilled person.
[0030] An embodiment of the present operation mode determination element will be described as applied to an exemplifying kind of protection device, as shown in Fig. 1. The protection device 100 is a distance protection device, which comprises an input terminal 110, the operation mode determination element 120, a phase selector 130, a fault direction determination element 140, a protection zone selector 150, a logic element 160, and an output terminal 170. The operation mode determination element 120 is connected, at an input thereof, with the input terminal 110, and at an output thereof, with the direction determination element 140 and the protection zone selector 150. The phase selector 130 is connected, at an input thereof, with the input terminal, and at an output thereof, with the fault direction determination element 140 and the protection zone selector 150. The fault direction determination element 140 is additionally connected, at an output thereof, with the logic element 160. The protection zone selector 150 is additionally connected, at an output thereof, with the logic element 160. The logic element is additionally connected with the output terminal 170.
[0031] The protection device 100 is connected some measurement device of a multi-phase power transmission system, such as an IED (Intelligent Electronic Device), capable of measuring electric quantities, such as current and voltage, on the transmission lines of the multi-phase power transmission system. For instance, if the power transmission system is a three-phase power transmission system, i.e. it comprises three transmission lines, one for each phase, the measurement device measures the phase currents and phase voltages on the three transmission lines. However, this is common technology readily understood by the person skilled in the art and it is neither shown in the drawings nor further explained herein. The protection device 100 receives the measured currents and voltages at its input terminal 110. At the output terminal 170, the protection device provides an operate signal, which, if the protection device has determined that a truefault has been detected on one or more transmission lines, trips one or more brokers in the power transmission system.
[0032] The present method employs sequence currents, which are determined from the phase currents. The determination of the sequence currents may be done in different ways. From a computing perspective it is convenient to provide the sequence currents in a phasor notation, i.e. a notation where each value is represented by a magnitude and a phase angle. For example, for the three-phase power transmission system, the phase currents received at the operation mode determination element 120 are sampled and a full cycle Discrete Fourier Transform (DFT) filter, or some other appropriate type of filtering, is applied. Then, the phasors of the sequence components for the currents are calculated by using a well-known matrix equation, as shown below for the current signals.
[0033]
[0034] The character "a” denotes a complex operator; a = e''120° = e7*1200,anc| j > j = V3!. Thus, the positive, negative and zero sequence current phasors h, I2, Io are all determined by different combinations of the phase currents IA, IB, IC.
[0035] According to an embodiment of the present method, as illustrated in the flow chart of Fig. 2, it comprises the following operations. Determining 201 phase currents of the phases of the multi-phase power transmission system. Determining 202 sequence currents, comprising zero sequence current and negative sequence current, from the phase currents. Determining 203 a zero sequence current decision value lOstart by means of a zero sequence current magnitude criterion lOmag and a zero sequence current magnitude ratio criterion lOratio, wherein the zero sequence current magnitude ratio criterion comprises a first magnitude ratio determined by means of a zero sequence current magnitude and a negative sequence current magnitude.
[0036] lOstart = lOmag & lOratio Eqn. 2Determining 204 a negative sequence current decision value I2start by means of a negative sequence current magnitude criterion I2mag and a negative sequence current magnitude ratio criterion I2ratio, wherein the negative sequence current magnitude ratio criterion comprises a second magnitude ratio determined by means of the zero sequence current magnitude and the negative sequence current magnitude.
[0037] I2start = I2mag & I2ratio Eqn. 3 Determining 205 the mode of operation, within a group of several modes of operation, to be applied, by means of the zero sequence current decision value lOstart and the negative sequence current decision value I2start.
[0038] According to an embodiment the zero sequence current magnitude criterion lOstart may comprise a comparison of the zero sequence current magnitude lOmag with a zero sequence current magnitude threshold mO, and the negative sequence current magnitude criterion I2start may comprise a comparison of the negative sequence current magnitude I2mag with a negative sequence current magnitude threshold m2. More particularly, the zero sequence current magnitude and the negative sequence current magnitude may be set to be greater than their respective thresholds. Furthermore, according to an embodiment of the method the zero sequence current magnitude ratio criterion lOratio comprises that the first magnitude ratio is greater than a first magnitude ratio threshold rO, and the negative sequence current ratio criterion comprises that the second magnitude ratio is less than a second ratio threshold r2. According to an embodiment the first magnitude ratio is the same as the second magnitude ratio. Typically, the first and second magnitude ratios are the zero sequence current divided by the negative sequence current. The inverse of that is usable as well, but then of course the thresholds and comparisons will have to be modified accordingly. Thus, an example of the zero sequence current decision value lOstart and the negative sequence current decision value I2start is illustrated as follows:
[0039] lOstart = ( lOmag > mO ) & ( IOmag / l2mag > rO ) Eqn. 4 I2start = ( I2mag > m2 ) & ( IOmag / l2mag < r2 ) Eqn. 5The zero sequence current decision value lOstart and the negative sequence current decision value I2start are true when both criteria of the respective equation are fulfilled. If at least one criterion is not fulfilled, the associated decision value, lOstart or I2start, is false. A false decision value means that the associated zero or negative sequence current is not usable in the determinations of the fault direction, carried out by the fault direction determination element 140. Then the mode of operation that is determined to be used does not rely on the discarded sequence current.
[0040] Further, according to an embodiment of the method, the zero sequence current magnitude criterion comprises a combination of a first zero sequence sub-criterion that the zero sequence current magnitude lOmag is greater than a first zero sequence current magnitude sub-threshold msO, and a second zero sequence sub-criterion that the zero sequence current magnitude lOmag is greater than a second zero sequence current magnitude sub-threshold mdO times a maximum magnitude of the phase currents max(lA, IB, IC). Similarly, the negative sequence current magnitude criterion may comprise a combination of a first negative sequence subcriterion that the negative sequence current magnitude I2mag is greater than a first negative sequence current magnitude sub-threshold ms2, and a second negative sequence sub-criterion that the negative sequence current magnitude I2mag is greater than a second negative sequence current magnitude sub-threshold md2 times a maximum magnitude of the phase currents max(lA, IB, IC).
[0041] (lOmag > mO) = (lOmag > msO ) & (lOmag > mdO * max(lA, IB, IC)) Eqn. 6 (I2mag > m2) = (I2mag > ms2) & (I2mag > md2 * max( IA, IB, IC)) Eqn. 7
[0042] The first zero sequence sub-criterion in the zero sequence current magnitude criterion and the negative sequence sub-criterion in the negative sequence current magnitude criterion use static thresholds. The second zero sequence sub-criterion and the second negative sequence subcriterion draw on a dynamic comparison which depends on the network conditions and pre fault currents will be adjusted dynamically inside the faultdetection calculation. That gives a dynamic robust security to the fault detection procedure performed by the protection device 100.
[0043] The above-described criteria provide areas for the zero sequence current IO and the negative sequence current I2 were they are usable, as illustrated in Fig. 3. It can be seen that the area for the zero sequence current and the area for the negative sequence current partly overlap. Where they overlap, both sequence currents can be used by the fault direction determination element, while outside of the area for the zero sequence current IO modes of operation using it will be disqualified for use, and so on.
[0044] The magnitude thresholds may be settable by the user providing an adaptability to specific networks.
[0045] Thus, turning again to the protection device 100, before adding the operation mode determination element 120, different conclusions were made by the fault direction determination element 140 and the protection zone selector 150 depending on the output of the phase selector 130, which in turn led to a particular final output from the logic element 160. The fault direction determination element 140 generally, had a number of modes of operation to choose from. The modes of operation used different algorithms to determine the direction of the fault. The algorithms could, for instance, employ phase angles of currents, such as the phase currents or one or more sequence currents, etc., as mentioned above. With the introduction of the operation mode determination element 120, according to the present disclosure, an additional factor in the basis for the determinations made by the fault direction determination element and the protection zone selector 150, which may alter their outputs, and ultimately may alter the output of the protection device 100. In other words, an output which would have caused a tripping may be an output which does not cause any tripping. The risk of generating a false tripping signal as well as the risk of missing a true fault are decreased.While the present disclosure has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive.
[0046] Although features and elements are described above in particular combinations, each feature or element can be used alone without the other features and elements or in various combinations with or without other features and elements.
[0047] Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the present disclosure, from a study of the drawings, the description, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single processor or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain features are recited in mutually different dependent claims does not indicate that a combination of these features cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.
Claims
New PCT Patent Application Vossius & Partner based on IN 202511017034 Patentanwalte Rechtsanwalte mbB Hitachi Energy Ltd SiebertstraRe 3 Ref.: P240308W001 81675 Munchen Vossius Ref.: AL1042 PCT February 24, 2026Claims:
1. A method of determining a mode of operation of a protection device in a multi-phase power transmission system, the method comprising: - determining phase currents of the phases of the multi-phase power transmission system;- determining sequence currents, comprising zero sequence current and negative sequence current, from the phase currents; - determining a zero sequence current decision value by means of a zero sequence current magnitude criterion and a zero sequence current magnitude ratio criterion, wherein the zero sequence current magnitude ratio criterion comprises a first magnitude ratio determined by means of a zero sequence current magnitude and a negative sequence current magnitude;- determining a negative sequence current decision value by means of a negative sequence current magnitude criterion and a negative sequence current magnitude ratio criterion, wherein the negative sequence current magnitude ratio criterion comprises a second magnitude ratio determined by means of the zero sequence current magnitude and the negative sequence current magnitude; and- determining the mode of operation, within a group of several modes of operation, to be applied, by means of the zero sequence current decision value and the negative sequence current decision value.
2. The method according to claim 1 , wherein the zero sequence current magnitude criterion comprises a comparison of the zero sequence current magnitude with a zero sequence current magnitudethreshold, and wherein the negative sequence current magnitude criterion comprises a comparison of the negative sequence current magnitude with a negative sequence current magnitude threshold.
3. The method according to claim 1 or 2, wherein the first magnitude ratio and the second magnitude ratio are the same.
4. The method according to any one of the preceding claims, wherein the zero sequence current magnitude ratio criterion comprises that the first magnitude ratio is greater than a first magnitude ratio threshold, and wherein the negative sequence current ratio criterion comprises that the second magnitude ratio is less than a second ratio threshold.
5. The method according to any one of the preceding claims, wherein the zero sequence current magnitude criterion comprises a combination of a first zero sequence sub-criterion that the zero sequence current magnitude is greater than a first zero sequence current magnitude sub-threshold, and a second zero sequence subcriterion that the zero sequence current magnitude is greater than a second zero sequence current magnitude sub-threshold times a maximum magnitude of the phase currents.
6. The method according to any one of the preceding claims, wherein the negative sequence current magnitude criterion comprises a combination of a first negative sequence sub-criterion that the negative sequence current magnitude is greater than a first negative sequence current magnitude sub-threshold, and second negative sequence sub-criterion that the negative sequence current magnitude is greater than a second negative sequence current magnitude sub-threshold times a maximum magnitude of the phase currents7. The method according to any one of the preceding claims, wherein the protection device is a distance protection device, and wherein the group of several modes of operation comprises determining a direction of a fault by means of one of current phase angles, delta values, the zero sequence current, the negative sequence current, and a transmission line impedance.
8. An operation mode determination element configured to determine a mode of operation of a protection device in a multi-phase power transmission system by performing the method of claim 1.
9. A computer program product comprising instructions which, when the program is executed by a computer, cause the computer to carry out the method of claim 1.14