DE102018113627A1 - Method and device for fault diagnosis in an electrical network having a ring structure and computer program product - Google Patents

Abstract

Method for fault diagnosis in an electrical network (1, 1 ') having a ring structure with a plurality of lines (L12, L13, L23) and a plurality of nodes (K1, K2, K3), at least two lines being outgoing lines (L12, L13), at least a line is a cross line (L23) connecting a pair of outgoing lines (L12, L13), a node is a collecting node (K1) fed by an AC voltage source (4) to which the outgoing lines (L12, L13) are connected, and at least two nodes are cross-connection nodes (K2, K3) to which the pair of outgoing lines (L12, L13) are connected to the cross line (L23), a node fault location AC resistance value between a fault location (F) on a faulty line and one the nodes (K1, K2, K3) as a function of cross-AC resistance values, each having a cross-AC resistance (Z, Z) of an energy conversion device (7a, 7) connected to an outgoing line (L12, L13) 7b) describe in a negative sequence system, - AC line resistance values, each of which describes an AC resistance (Z, Z, Z) of one of the lines (L12, L13, L23), and - outgoing line current values, each of which at the common node (K1) into one of the outgoing lines ( L12, L13) current flowing (I, I) describe in the opposite system, is determined.

Description

The present invention relates to a method of fault diagnosis in a multi-line, multiple-node, multi-node loop electrical network, wherein at least two lines are output lines, at least one line is a cross-line connecting a pair of output lines, a node is powered by an AC voltage source Is a collection node to which the outgoing lines are connected and at least two nodes are cross-connection nodes to which the pair of outgoing lines are connected to the cross-line.

In addition, the invention relates to a device for fault diagnosis in a ring structure having an electrical network and a computer program product.

Such a method is for example from the document DE 600 18 666 T2 which discloses a method of calculating the removal of fault current in an annular electric power supply network.

In modern electrical networks, which have a ring structure, but increasingly decentralized energy conversion facilities, such as wind turbines, combined heat and power or small hydropower plants are connected. These typically have a synchronous or asynchronous machine, which makes the electrical network much more complex and conventional methods for fault diagnosis provide insufficient results.

The invention is therefore based on the object of specifying a possibility for fault diagnosis in complex electrical networks with a ring structure.

To achieve this object, the invention provides in a method of the type mentioned that a node fault location AC resistance value between a fault location on a faulty line and one of the nodes as a function of Querwechselstromwiderstandswerten, each having a transverse AC resistance of an output line connected to an energy conversion device in a Describe negative sequence, AC line resistance values, each describing an AC resistance of one of the lines, and outgoing line current values, each describing a flowing at the collecting node in one of the outgoing lines current in the negative sequence, is determined.

The invention is based on the recognition that the node fault location AC resistance value, which is relevant in particular for the localization of the fault, is substantially influenced by the transverse AC resistance when connecting energy conversion devices to the electrical network. In this case, the invention makes use of the fact that the node fault location AC resistance value can be determined with sufficient accuracy by a consideration of the negative sequence of the electrical network and the transverse AC resistance value of the connected energy conversion devices is typically known and, in particular, constant over wide operating state ranges. With additional consideration of the typically also known line AC resistance values and the output line current values measured, for example, in the vicinity of the collector node, the node fault location AC resistance value can then be determined with little expense for fault diagnosis.

The method according to the invention thus advantageously makes it possible to diagnose faults in complex electrical networks with a ring structure, even if they are connected to these energy conversion devices. In particular, the method of the present invention allows the node fault location AC resistance value to be determined with high accuracy based on a priori known data in the form of the lateral AC resistance values and the AC line resistance values as well as measured near the collector node of the conducted current values. The method according to the invention is suitable for faults in the form of short-circuits, for example two-pole phase-phase faults or single-pole earth faults.

In general, the electrical network is a multi-phase, in particular three-phase, AC mains, such as a medium-voltage or low-voltage power supply network. The term "negative sequence" in the context of the invention refers to an analytical view of the electrical network according to the method of symmetrical components, the network is divided into a positive system, the negative sequence and a zero system. The AC resistance values may each describe an impedance or an admittance. They can be purely real or complex.

The energy conversion devices are usually distributed energy conversion devices. Examples of energy conversion devices are wind turbines, combined heat and power plants or hydropower plants. The energy conversion devices may have a synchronous machine or asynchronous machine designed to supply energy to the electrical network. The transverse alternating current resistance value can be derived or determined in the case of a synchronous machine from nameplate information and the like, since it is essentially constructive. In asynchronous machines, the transverse alternating current resistance depends to a small extent on the slip. Since asynchronous machines are normally operated with very little slip, however, a transverse alternating current resistance value for an asynchronous machine can be used for a given slip value without significantly impairing the accuracy of the method according to the invention. An energy conversion device can also have a converter for feeding into the electrical network. Also in this case, a cross-alternating current resistance value can be used when the inverter is designed to be fed to the negative sequence system.

The method according to the invention can have a step of retrieving the transverse alternating current resistance values and / or the line alternating current resistance values, for example from a memory unit or / or by means of a communication unit. Further, the method may include a step of measuring the outgoing line current values. The measuring preferably takes place at or near the collecting node.

In the method according to the invention, the determination of the node fault location AC resistance value preferably takes place in additional dependence of a network AC resistance value which describes an AC internal resistance of the AC voltage source in the negative sequence. By considering the AC resistance of the AC power source, the accuracy of the fault diagnosis can be improved.

Preferably, the determination of the node fault location AC resistance value takes place on the basis of a model based on an equivalent circuit diagram of the negative sequence of the electrical network and which models a fault current flowing at the fault location and flowing through it. The equivalent circuit diagram preferably has only passive components, the outgoing line current values being assumed as currents in the equivalent circuit diagram. In other words, the fault current may be considered to be through a negative sequence supply current source causing the measured currents described by the output line current values. Since the fault location may be between any pair of adjacent nodes, an equivalent circuit dependent on the fault location may be used.

Preferably, the node fault location AC resistance value is determined in accordance with a calculation rule which is selected as a function of the faulty line or which depends on the faulty line. The calculation rule can be an equation dependent on the location of the fault or selected as a function of the error location. Alternatively, it is possible to set up a system of equations of the equivalent circuit diagram in the evaluation of the calculation rule and to solve the node fault location AC resistance by solving the equation system, for example according to the node potential method or the mesh current method. Likewise, within the framework of the calculation rule, the equivalent circuit diagram can be successively analyzed and / or transformed for calculating the node-fault location AC resistance value, for example using the triangular-star transformation.

By means of an additional step, in the context of the method according to the invention, the faulty line can be determined as a function of fault current contribution values which describe a contribution of the current along the outgoing line to a fault current in the negative sequence caused by the fault.

For this purpose, the residual current contribution values can be compared with reference residual current contribution values which, for a respective outgoing line, describe the contribution of a current of the outgoing line in the case of an assumed error at the location of a crossconnecting node. The reference residual current contribution values may have been determined by a simulation, in particular with reference to the equivalent circuit diagram, or a measurement in advance or determined within the scope of the method according to the invention.

In addition, a respective residual current contribution value may be determined as a real part of the ratio of the current along the outgoing line to the sum of the currents of all outgoing lines. Alternatively or additionally, reference residual current contribution values may be used, each describing a real part of the ratio of the current along the outgoing line to the sum of the currents of all outgoing lines.

In the context of the method according to the invention, furthermore, depending on the node fault location AC resistance value and the line AC resistance value of a non-defective line, an error resistance value which describes an AC, reactive or effective resistance between the collecting node and the fault location can be determined. Thus, the node fault location AC resistance value may be construed as a proportion of the AC line resistance value of the faulty line, so that the fault resistance value can be calculated by simply adding the node fault location AC resistance value with one or more AC line resistance values of the non-faulty lines.

Particularly preferably, in the method according to the invention for fault diagnosis, a fault location information describing the distance from the busbar or a location of the measurement of an outgoing line current value to the fault location is determined. In this case, the fault location information can be determined as a function of the fault resistance value or its complex components. The fault location information is determined in particular by means of a function which indicates the distance as a function of the complex component, ie a resistance, conductance, reactance or susceptance. The function is typically known a priori and can be mapped, for example, in a look-up table. In other words, the fault location information can be determined as a function of a resistance, conductance, reactance or susceptance lining of the network.

In addition, in the method according to the invention preferably loads at other nodes of the outgoing lines are disregarded. This is based on the knowledge that such loads usually have no influence on the negative sequence affecting the desired accuracy of the fault diagnosis.

Preferably, a busbar is used as the collecting node and / or an infeed network is used as the alternating voltage source. The method can therefore be carried out in the immediate vicinity of the busbar or of a mains transformer, where it is particularly easy to fall back on the AC resistance values and output line current values required for the determination.

In addition, the invention relates to a device for fault diagnosis in a ring structure having electrical network, comprising a control device which is adapted to perform the method according to the invention. The device according to the invention is preferably designed as a relay device for use at the collecting node or at the busbar.

The device according to the invention may comprise a measuring unit for measuring one or more of the outgoing line current values and / or a separating unit, by means of which one of the outgoing current lines is separable from the collecting node in dependence on the determined node fault location AC resistance value and / or a communication unit for receiving the further outgoing line current values and or a memory unit for storing the transverse AC resistance values and / or the line AC resistance values and / or the AC line current resistance value.

Moreover, the invention relates to a computer program product for loading into a memory unit of a computer, in particular the control device of the device according to the invention, comprising software code, with which the inventive method is performed when the computer program product is executed on a computer.

All embodiments of the method according to the invention can be analogously transferred to the device according to the invention and the computer program product according to the invention, so that even with these the aforementioned advantages can be achieved.

• 1 ein Schaltbild eines elektrischen Netzes mit Ringstruktur;
• 2 ein Ersatzschaltbild des Gegensystems des elektrischen Netzes in einer ersten Darstellung;
• 3 ein Blockschaltbild eines Ausführungsbeispiels der erfindungsgemäßen Vorrichtung;
• 4 ein Flussdiagramm eines Ausführungsbeispiels des erfindungsgemäßen Verfahrens;
• 5 das in 2 gezeigte Ersatzschaltbild in einer zweiten Darstellung;
• 6 eine Funktion der Entfernung der erfindungsgemäßen Vorrichtung zu Orten im elektrischen Netz über einer Komponente eines Fehlerwiderstandswerts; und
• 7 ein Schaltbild eines weiteren elektrischen Netzes mit Ringstruktur.

Further advantages and details of the invention will become apparent from the embodiments described below as with reference to the drawings. These are schematic representations and show:

• 1 a circuit diagram of an electrical network with ring structure;
• 2 an equivalent circuit diagram of the negative sequence of the electrical network in a first representation;
• 3 a block diagram of an embodiment of the device according to the invention;
• 4 a flowchart of an embodiment of the method according to the invention;
• 5 this in 2 shown equivalent circuit diagram in a second representation;
• 6 a function of removing the device according to the invention to locations in the electrical network over a component of a fault resistance value; and
• 7 a circuit diagram of another electrical network with ring structure.

1 is a circuit diagram of a ring structure having an electrical network 1 which forms, for example, a middle or low voltage level of a three-phase power supply network.

The electrical network 1 includes one through a busbar 2 trained collecting node K1 by an AC source 4 in the form of a feeding network 5 is fed and on the departure lines L12 . L13 are connected, and two cross connection nodes K2 . K3 to which the outgoing lines L12 . L13 to a transverse line connecting them L23 are connected. Next to it is the electrical network 1 another node K4 on, to the one load 6 connected. The knot K4 divides the outgoing line into outgoing line sections L14 . L34 , To the exit lines L12 . L13 is each on the collecting node K1 opposite side of a cross connection node K2 . K3 a decentralized energy conversion device 7a . 7b connected, which in turn electrical energy into the electrical network 1 feeds. At a fault location F who exemplifies on the cross line L23 is located, there is an error, such as a short circuit, before, the cross-line L23 in a line section L2F between the cross-connection node K2 and the fault location F as well as in a line section L3F between the cross-connection node K3 and the fault location F divides.

In the outlet lines L12 . L13 each are also a measuring unit 8a . 8b and a separation unit 9a . 9b arranged. The measuring units 8a . 8b are there to measure the current along the outgoing lines L12 . L13 and the separation units 9a . 9b to separate the outgoing line L12 . L13 from the collecting node K1 educated. The separation units 9a . 9b as well as the measuring units 8a . 8b are in close proximity to the collecting node K1 , namely much closer to the collecting node K1 as at the energy conversion facilities 7a . 7b arranged. The collection node K1 , the AC source 4 , the measurement units 8a . 8b and the separation units 9a . 9b For example, they may be located in a substation or the like from which the energy conversion devices 7a . 7b several tens or hundreds of meters or several kilometers away.

2 is an equivalent circuit diagram of a negative sequence of the electrical network 1 in a first presentation. The negative sequence is based on an analysis of the electrical network 1 on a method of symmetric components.

This is an AC resistance Z _L12 the departure line L12 , an AC resistor Z _L13 the departure line L13 and an AC resistance Z _L23 the departure line L23 modeled. The AC resistance Z _L13 results as a series connection of AC resistors Z _L14 . Z _L34 the outgoing line sections L14 . L34 , At the error location assumed here F between the cross-connection nodes K2 . K3 results in the AC resistance Z _L23 further as a series connection of an AC resistance Z _L2F of the line section L2F and an AC resistance Z _L3F of the line section L3F , The decentralized energy conversion devices 7a . 7b are as cross-AC resistors Z _DEA1 . Z _DEA2 modeled. In addition, an internal AC resistance Z _N the AC voltage source 4 modeled. The equivalent circuit remains the load 6 are disregarded because their transverse impedance as much larger than the impedances of the transverse AC resistors Z _DEA1 . Z _DEA2 and therefore has little effect on the accuracy of the calculation. It is of course alternatively conceivable, the load 6 to be considered in the equivalent circuit diagram.

The equivalent circuit is modeled as a network with passive components. It is assumed that a fault current flowing through the negative sequence system I _F caused by the error and the measurement data of the measuring units 8a . 8b detected currents, namely a current I _A in the exit line L12 and a stream I _B in the exit line L13 , caused..

Although the AC resistances are designated as impedances with a Z, of course admittances can also be used to describe the AC resistances. Unless otherwise specified, sizes provided with an underscore are complex and refer to the negative sequence.

3 is a block diagram of an embodiment of a device 10 for fault diagnosis in the electrical network 1 ,

The device 10 includes a control unit 11 , the measurement unit 8a for measuring a current along the outgoing line L12 , the separation unit 9a , by means of which the outgoing line L12 from the collecting node K1 is separable, as well as a communication unit 12 and a storage unit 13 , The communication unit 12 is with the other outgoing line L13 assigned measuring unit 13 for a data transmission, which in turn is part of another device for fault diagnosis 10 ' is. The devices 10 . 10 ' can therefore be considered as a multi-function relay, which are installed, for example, in the aforementioned substation.

In an alternative embodiment, the device comprises 10 measurement units 8a . 8b and the separation units 9a . 9b for a respective outgoing line L12 . L13 , the control unit 11 and the storage unit 13 , In this case, form the control unit 11 and the storage unit 13 central units responsible for receiving data of the measuring units 8a . 8b and for driving the separation units 9a . 9b are set up.

In both embodiments, the control unit 11 for carrying out a method for fault diagnosis in the electrical network 1 that is described in more detail below:

4 is a flowchart of an embodiment of the method for fault diagnosis in the electrical network 1 ,

In a first step S1 is detected on one of the lines L12 . L13 . L23 there is an error without the faulty line or even the exact fault location F being known at this time. This error detection is performed by the control device 11 in a conventional manner known in the art.

In a following step S2 Outgoing line current values are detected, each at the collecting node K1 into one of the outgoing lines L12 . L13 flowing electricity I _A . I _B in the opposite system. The measurement is carried out by means of the measuring units 8a . 8b , where appropriate, measured values from the measuring unit 8b via the communication unit 12 be retrieved.

$$FC{C}_{real,B,F}=Re\left\{\frac{{\underset{\_}{I}}_B}{{\underset{\_}{I}}_A+{\underset{\_}{I}}_B}\right\}$$

In a next step S3 are used to determine the faulty line, here the cross line L23 , Residual current contribution values FCC _{real, A, F} , FCC _{real, B, F} determined. The residual current contribution values FCC _{real, A, F} , FCC _{real, B, F} describe in this case for a respective outgoing line L12 . L13 a contribution of the stream I _A . I _B to the fault current caused by the fault I _F in the opposite system. The determination of the residual current contribution values FCC _{real, A, F} , FCC _{real, B, F} takes place - regardless of the fault location F - as a real part of the ratio of the current along the outgoing line L12 . L13 to the sum of the currents of all outgoing lines L12 . L13 using the following equations, where the operator Re {·} describes the real part: $$FC{C}_{real.A.F}=Re\left\{\frac{{\underset{\_}{I}}_A}{{\underset{\_}{I}}_A+{\underset{\_}{I}}_B}\right\}$$

$$FC{C}_{real.B.F}=Re\left\{\frac{{\underset{\_}{I}}_B}{{\underset{\_}{I}}_A+{\underset{\_}{I}}_B}\right\}$$

In one step S4 the residual current contribution values FCC _{real, A, F} , FCC _{real, B, F} with reference residual current contribution values FCCreal, A, K2, ref, FCCreal, A, K3, ref, FCCreal, B, K2, ref, FCC _{real, B, K3, ref} compared that for a respective outgoing line L12 . L13 a contribution of a current I _{A, ref} , I _{B, ref} , which in the case of an assumed error at the location of a cross-connection node K2 . K3 in the exit line L12 . L13 flows, describe.

$$FC{C}_{real,B,K\mathrm{2,}ref}=Re\left\{\frac{{\underset{\_}{I}}_{B,ref,K2}}{{\underset{\_}{I}}_{A,ref,K2}+{\underset{\_}{I}}_{B,ref,K2}}\right\}$$

The reference residual current contribution values FCC _{real, A, K2, ref} , FCC _{real, A, K3, ref} , FCC _{real, B, K2, ref} , FCC _{real, B, K3, ref} are therefore already at the time of the occurrence of the error (a priori) known and may have been determined by simulation or measurement. They are in the storage unit 13 stored and are by the control unit 11 accessed. The reference residual current contribution values FCC _{real, A, K2, ref} , FCC _{real, B, K2, ref} , for which an error at the cross-connection node K2 is assumed, the following equations result: $$FC{C}_{real.A.\mathrm{<figure-callout\; id="2"\; label="K"\; filenames="DE102018113627A1\_0029.png"\; state="\{\{state\}\}">K</figure-callout>}\mathrm{2,}ref}=Re\left\{\frac{{\underset{\_}{I}}_{A.ref.K2}}{{\underset{\_}{I}}_{A.ref.\mathrm{<figure-callout\; id="2"\; label="K"\; filenames="DE102018113627A1\_0029.png"\; state="\{\{state\}\}">K</figure-callout>}2}+{\underset{\_}{I}}_{B.ref.K2}}\right\}$$

$$FC{C}_{real.B.\mathrm{<figure-callout\; id="2"\; label="K"\; filenames="DE102018113627A1\_0029.png"\; state="\{\{state\}\}">K</figure-callout>}\mathrm{2,}ref}=Re\left\{\frac{{\underset{\_}{I}}_{B.ref.K2}}{{\underset{\_}{I}}_{A.ref.\mathrm{<figure-callout\; id="2"\; label="K"\; filenames="DE102018113627A1\_0029.png"\; state="\{\{state\}\}">K</figure-callout>}2}+{\underset{\_}{I}}_{B.ref.K2}}\right\}$$

$$FC{C}_{real,B,K\mathrm{3,}ref}=Re\left\{\frac{{\underset{\_}{I}}_{B,ref,K3}}{{\underset{\_}{I}}_{A,ref,K3}+{\underset{\_}{I}}_{B,ref,K3}}\right\}$$

The reference residual current contribution values FCC _{real, A, K3, ref} , FCC _{real, B, K3, ref} , for which an error at the cross-connection node K3 is assumed, the following equations result: $$FC{C}_{real.A.K\mathrm{3,}ref}=Re\left\{\frac{{\underset{\_}{I}}_{A.ref.K3}}{{\underset{\_}{I}}_{A.ref.K3}+{\underset{\_}{I}}_{B.ref.K3}}\right\}$$

$$FC{C}_{real.B.K\mathrm{3,}ref}=Re\left\{\frac{{\underset{\_}{I}}_{B.ref.K3}}{{\underset{\_}{I}}_{A.ref.K3}+{\underset{\_}{I}}_{B.ref.K3}}\right\}$$

In this case, I _{A, ref, K2} and I _{A, ref, K3 describe} outgoing line current values along the outgoing line L12 and I _{B, ref, K2} and I _{B, ref, K3} outgoing line current values along the outgoing line L13 assuming the error at the cross-connection node K2 respectively. K3 ,

Depending on the comparison, the faulty line is determined using the following table: FCC _{real, A, F} FCC _{real, B, F} Faulty line > FCC _{real, A, K2, ref} <FCC _{real, B, K2, ref} L12 Λ ≤ 1 Λ ≥ 0 <FCC _{real, A, K2, ref} <FCC _{real, B, K3, ref} L23 Λ> FCC _{real, A, K3, ref} Λ> FCC _{real, B, K2, ref} > FCC _{real, A, K3, ref} > FCC _{real, B, K3, ref} L13 Λ≥0 Λ ≤ 1

der einen Fehler unmittelbar am Querverbindungsknoten K2 oder innerhalb der Energieumwandlungseinrichtung 7a beschreibt, und der Spezialfall $${\text{FCC}}_{\text{real}\text{,A}\text{,F}}={\text{FCC}}_{\text{real}\text{,A}\text{,K3}\text{,ref}}\text{ bzw}.{\text{ FCC}}_{\text{real}\text{,B}\text{,F}}={\text{FCC}}_{\text{real}\text{,B}\text{,K3}\text{,ref}},$$

der einen Fehler unmittelbar am Querverbindungsknoten K3 oder innerhalb der Energieumwandlungseinrichtung 7b beschreibt, genannt. Daneben weisen Fehlerstrombeitragswerte FCC_real,A,F > 1 oder FCC_real,A,F < 0 oder FCC_real,B,F > 1 oder FCC_real,B,F < 0 auf eine nicht dreipolige Leiterunterbrechung im elektrischen Netz 1 hin, da in solchen Fällen die Realteile der Gegensystemströme unterschiedliche Vorzeichen aufweisen.In addition to this are still the special case $${\text{FCC}}_{\text{real}\text{, A}\text{, F}}={\text{FCC}}_{\text{real}\text{, A}\text{, K2}\text{, ref}}\text{respectively},{\text{FCC}}_{\text{real}\text{, B}\text{, F}}={\text{FCC}}_{\text{real}\text{, B}\text{, K2}\text{, ref}}.$$

the error directly at the cross-connection node K2 or within the energy conversion device 7a describes, and the special case $${\text{FCC}}_{\text{real}\text{, A}\text{, F}}={\text{FCC}}_{\text{real}\text{, A}\text{, K3}\text{, ref}}\text{respectively},{\text{FCC}}_{\text{real}\text{, B}\text{, F}}={\text{FCC}}_{\text{real}\text{, B}\text{, K3}\text{, ref}}.$$

the error directly at the cross-connection node K3 or within the energy conversion device 7b describes, called. In addition, residual current contribution values FCC _{real, A, F} > 1 or FCC _{real, A, F} <0 or FCC _{real, B, F} > 1 or FCC _{real, B, F} <0 indicate a non-three-pole conductor interruption in the electrical network 1 because in such cases the real parts of the negative sequence currents have different signs.

In a subsequent step S5 becomes a node fault location AC resistance value between the fault location F and an adjacent node K1 . K2 . K3 . K4 determined. In the in 2 shown case of a fault on the transverse line L23 Thus, alternatively, as the node fault location AC resistance value, the value of the AC resistance Z _L2F of the line section L2F or the value of the AC resistance Z _L3F of the line section L3F be calculated after the cross line L23 in step S4 was determined as faulty line.

The node fault location AC resistance value is determined according to a calculation rule that depends on the faulty line L23 is chosen or that of the faulty line L23 is dependent. This calculation specification is made by the control unit 11 executed. The control unit calls for this 11 known transverse AC resistance values, each one of the transverse AC resistances Z _DEA1 . Z _DEA2 , describe line AC resistance values, each one of the Impedances Z _L12 . Z _L23 . Z _L34 . Z _L14 as well as an AC line resistance value that determines the internal AC resistance Z _N describes from the storage unit 13 from. The lateral alternating current resistance values, the line alternating current resistance values, the AC mains resistance value as well as those in step S2 detected outgoing line current values are variables of the calculation specification.

In the following, the network-theoretical derivation of this calculation rule is based on the in 2 shown fault on the cross line L23 but this does not mean that the described analysis and transformation steps are also performed by the control unit 11 itself would have to be carried out:

The following values are known a priori: Z _L12 . Z _L23 . Z _L34 . Z _L14 . Z _DEA1 . Z _DEA2 , Further, measured values are further I _A . I _B known. From the determination of the faulty line follows the context Z _L23 = Z _L2F + Z _L3F for the node fault location AC resistance values. For better clarification of the derivation is on 5 Reference is made to an equivalent second representation of the equivalent circuit diagram in FIG 2 is.

In 5 are additionally a first partial fault current I _LF in a branch shown on the left between the fault location F and an adjacent node, here the cross connection node K2 , and a second partial fault current I _RF in a branch shown on the right between the fault location F and the other neighboring node, here the cross connection node K3 , shown. The partial fault currents I _LF . I _LR sum up the fault current I _F , There are also tensions U _L and U _R via AC resistors connected to the neighboring nodes, here voltages U _DEA1 . U _DEA2 over the transverse AC resistors Z _DEA1 respectively. Z _DEA2 , shown.

The partial fault currents I _LF . I _LR can be determined as follows:
For the tension U _N applies: $${\underset{\_}{U}}_N=-\left({\underset{\_}{I}}_A+{\underset{\_}{I}}_B\right)\cdot {\underset{\_}{Z}}_N$$

$${\underset{\_}{I}}_{DEA1}=-\frac{{\underset{\_}{U}}_{DEA1}}{{\underset{\_}{Z}}_{DEA1}}$$

This results in a mesh 14 following sizes: $${\underset{\_}{U}}_L={\underset{\_}{U}}_N-{\underset{\_}{I}}_A\cdot {\underset{\_}{Z}}_{\mathrm{<figure-callout\; id="12"\; label="L"\; filenames="DE102018113627A1\_0030.png"\; state="\{\{state\}\}">L</figure-callout>}12}={\underset{\_}{U}}_{\mathrm{<figure-callout\; id="1"\; label="D\; e\; A"\; filenames="DE102018113627A1\_0033.png"\; state="\{\{state\}\}">D\; </figure-callout>}eA1}$$

$${\underset{\_}{I}}_{\mathrm{<figure-callout\; id="1"\; label="D\; e\; A"\; filenames="DE102018113627A1\_0033.png"\; state="\{\{state\}\}">D\; </figure-callout>}eA1}=-\frac{{\underset{\_}{U}}_{DeA1}}{{\underset{\_}{Z}}_{\mathrm{<figure-callout\; id="1"\; label="D\; e\; A"\; filenames="DE102018113627A1\_0033.png"\; state="\{\{state\}\}">D\; </figure-callout>}eA1}}$$

$${\underset{\_}{I}}_{DEA1}=-\frac{{\underset{\_}{U}}_{DEA2}}{{\underset{\_}{Z}}_{DEA2}}$$

Analog results for a mesh 15 : $${\underset{\_}{U}}_R={\underset{\_}{U}}_N-{\underset{\_}{I}}_B\cdot \left({\underset{\_}{Z}}_{\mathrm{<figure-callout\; id="14"\; label="L"\; filenames="DE102018113627A1\_0032.png"\; state="\{\{state\}\}">L</figure-callout>}14}+{\underset{\_}{Z}}_{L34}\right)={\underset{\_}{U}}_{\mathrm{<figure-callout\; id="2"\; label="D\; e\; A"\; filenames="DE102018113627A1\_0029.png"\; state="\{\{state\}\}">D\; </figure-callout>}eA2}$$

$${\underset{\_}{I}}_{\mathrm{<figure-callout\; id="1"\; label="D\; e\; A"\; filenames="DE102018113627A1\_0033.png"\; state="\{\{state\}\}">D\; </figure-callout>}eA1}=-\frac{{\underset{\_}{U}}_{DeA2}}{{\underset{\_}{Z}}_{\mathrm{<figure-callout\; id="2"\; label="D\; e\; A"\; filenames="DE102018113627A1\_0029.png"\; state="\{\{state\}\}">D\; </figure-callout>}eA2}}$$

$${\underset{\_}{I}}_{R-F}={\underset{\_}{I}}_B+{\underset{\_}{I}}_{DEA2}={\underset{\_}{I}}_B+\frac{\left({\underset{\_}{I}}_A+{\underset{\_}{I}}_B\right)+{\underset{\_}{Z}}_N+{\underset{\_}{I}}_B\cdot \left({\underset{\_}{Z}}_{L12}+{\underset{\_}{Z}}_{L34}\right)}{{\underset{\_}{Z}}_{DEA2}}$$

For the partial fault currents I _LF . I _LR follows from the known values: $${\underset{\_}{I}}_{L-F}={\underset{\_}{I}}_A+{\underset{\_}{I}}_{\mathrm{<figure-callout\; id="1"\; label="D\; e\; A"\; filenames="DE102018113627A1\_0033.png"\; state="\{\{state\}\}">D\; </figure-callout>}eA1}={\underset{\_}{I}}_A+\frac{\left({\underset{\_}{I}}_A+{\underset{\_}{I}}_B\right)+{\underset{\_}{Z}}_N+{\underset{\_}{I}}_A\cdot {\underset{\_}{Z}}_{L12}}{{\underset{\_}{Z}}_{\mathrm{<figure-callout\; id="1"\; label="D\; e\; A"\; filenames="DE102018113627A1\_0033.png"\; state="\{\{state\}\}">D\; </figure-callout>}eA1}}$$

$${\underset{\_}{I}}_{R-F}={\underset{\_}{I}}_B+{\underset{\_}{I}}_{\mathrm{<figure-callout\; id="2"\; label="D\; e\; A"\; filenames="DE102018113627A1\_0029.png"\; state="\{\{state\}\}">D\; </figure-callout>}eA2}={\underset{\_}{I}}_B+\frac{\left({\underset{\_}{I}}_A+{\underset{\_}{I}}_B\right)+{\underset{\_}{Z}}_N+{\underset{\_}{I}}_B\cdot \left({\underset{\_}{Z}}_{\mathrm{<figure-callout\; id="12"\; label="L"\; filenames="DE102018113627A1\_0030.png"\; state="\{\{state\}\}">L</figure-callout>}12}+{\underset{\_}{Z}}_{L34}\right)}{{\underset{\_}{Z}}_{\mathrm{<figure-callout\; id="2"\; label="D\; e\; A"\; filenames="DE102018113627A1\_0029.png"\; state="\{\{state\}\}">D\; </figure-callout>}eA2}}$$

From a circulation of a total mesh from the stitches 14 . 15 and a mesh 16 also results: $${\underset{\_}{U}}_L-{\underset{\_}{I}}_{L-F}\cdot {\underset{\_}{Z}}_{L-F}={\underset{\_}{U}}_R-{\underset{\_}{I}}_{R-F}\cdot {\underset{\_}{Z}}_{R-F}$$

Describe Z _LF and Z _RF the AC resistances of the node fault location resistance values and correspond here Z _L2F respectively. Z _L3F , From the known relationship for the AC resistance of the faulty line Z _F = Z _LF + Z _RF , where present Z _L23 = Z _L2F + Z _L3F applies, therefore follows: $${\underset{\_}{U}}_L-{\underset{\_}{I}}_{L-F}\cdot {\underset{\_}{Z}}_{L-F}={\underset{\_}{U}}_R-{\underset{\_}{I}}_{R-F}\cdot \left({\underset{\_}{Z}}_F-{\underset{\_}{Z}}_{L-F}\right)$$

By transforming the equation, one obtains for the node fault location AC resistance value from the known values alone: $${\underset{\_}{Z}}_{L-F}=\frac{{\underset{\_}{U}}_L-{\underset{\_}{U}}_R+{\underset{\_}{I}}_{R-F}\cdot {\underset{\_}{Z}}_F}{{\underset{\_}{I}}_{L-F}+{\underset{\_}{I}}_{R-F}}=\frac{{\underset{\_}{U}}_{DeA1}-{\underset{\_}{U}}_{\mathrm{<figure-callout\; id="2"\; label="D\; e\; A"\; filenames="DE102018113627A1\_0029.png"\; state="\{\{state\}\}">D\; </figure-callout>}eA2}+{\underset{\_}{I}}_{3F}\cdot {\underset{\_}{Z}}_{L23}}{{\underset{\_}{I}}_{2F}+{\underset{\_}{I}}_{3F}}$$

Alternatively, the other node fault location AC resistance value may also be based on the AC resistance Z _RF respectively. Z _L3F be calculated. On the basis of the preceding derivation, the person skilled in the art can also determine corresponding calculation instructions for faults on other faulty lines. According to an alternative embodiment, the control unit performs 11 the previously described analysis and transformation steps in the context of the method itself.

In a following step S6 becomes a fault resistance value which is an AC, reactive or effective resistance between the collecting node depending on the node fault location AC resistance value and the line AC resistance value of a non-faulty line K1 and the fault location F described determined.

For this purpose, only the AC line resistance value for the AC resistance Z _L12 the departure line L12 to the node fault location AC resistance value for the AC resistance Z _L2F added: $${\underset{\_}{Z}}_{A-F}={\underset{\_}{Z}}_{\mathrm{<figure-callout\; id="12"\; label="L"\; filenames="DE102018113627A1\_0030.png"\; state="\{\{state\}\}">L</figure-callout>}12}+{\underset{\_}{Z}}_{L-F}$$

Alternatively, the AC line resistance value for the AC resistance becomes Z _L13 the departure line L13 to the node fault location AC resistance value for the AC resistance Z _L3F added: $${\underset{\_}{Z}}_{B-F}={\underset{\_}{Z}}_{\mathrm{<figure-callout\; id="14"\; label="L"\; filenames="DE102018113627A1\_0032.png"\; state="\{\{state\}\}">L</figure-callout>}14}+{\underset{\_}{Z}}_{L34}+{\underset{\_}{Z}}_{R-F}$$

In a subsequent step S7 For fault diagnosis, a fault location information describing the distance from the busbar or a location of the measurement of an outgoing line current value to fault location F is determined. For this either resistances RA-F = Re {ZA-F}, RB-F = Re {ZB-F} or reactances X _AF = Im {Z _AF }, X _BF = Im {Z _BF } are determined, where the operator Im {·} Describes the imaginary part. From known resistances or Reaktanzbelägen the network 1 Thus, the removal of the fault location F from the collecting node K1 or the location of the measurement. In addition shows 6 a function of removing the device 10 to places in the electrical network 1 over a component of an error resistance value.

7 is another example of a network 1' with a ring structure, which, however, compared to the in 1 shown network 1 has four parallel outgoing lines. In such a network 1' or networks with even more outgoing lines, the method described above can be applied analogously.

$$FC{C}_{real,B,F}=Re\left\{\frac{{\underset{\_}{I}}_B}{{\underset{\_}{I}}_A+{\underset{\_}{I}}_B+{\underset{\_}{I}}_C+{\underset{\_}{I}}_D}\right\}$$

$$FC{C}_{real,C,F}=Re\left\{\frac{{\underset{\_}{I}}_C}{{\underset{\_}{I}}_A+{\underset{\_}{I}}_B+{\underset{\_}{I}}_C+{\underset{\_}{I}}_D}\right\}$$

$$FC{C}_{real,D,F}=Re\left\{\frac{{\underset{\_}{I}}_D}{{\underset{\_}{I}}_A+{\underset{\_}{I}}_B+{\underset{\_}{I}}_C+{\underset{\_}{I}}_D}\right\}$$

It will be in the step S2 for all outgoing lines, outgoing line current values, each one current I _A . I _B . I _C . I _D describe captured. In step S3 Corresponding to residual current contribution values for a respective outgoing line are determined: $$FC{C}_{real.A.F}=Re\left\{\frac{{\underset{\_}{I}}_A}{{\underset{\_}{I}}_A+{\underset{\_}{I}}_B+{\underset{\_}{I}}_C+{\underset{\_}{I}}_D}\right\}$$

$$FC{C}_{real.B.F}=Re\left\{\frac{{\underset{\_}{I}}_B}{{\underset{\_}{I}}_A+{\underset{\_}{I}}_B+{\underset{\_}{I}}_C+{\underset{\_}{I}}_D}\right\}$$

$$FC{C}_{real.C.F}=Re\left\{\frac{{\underset{\_}{I}}_C}{{\underset{\_}{I}}_A+{\underset{\_}{I}}_B+{\underset{\_}{I}}_C+{\underset{\_}{I}}_D}\right\}$$

$$FC{C}_{real.D.F}=Re\left\{\frac{{\underset{\_}{I}}_D}{{\underset{\_}{I}}_A+{\underset{\_}{I}}_B+{\underset{\_}{I}}_C+{\underset{\_}{I}}_D}\right\}$$

$$FC{C}_{real,B,Kx,ref}=Re\left\{\frac{{\underset{\_}{I}}_{B,ref}}{{\underset{\_}{I}}_{A,ref}+{\underset{\_}{I}}_{B,ref}+{\underset{\_}{I}}_{C,ref}+{\underset{\_}{I}}_{D,ref}}\right\}$$

$$FC{C}_{real,C,Kx,ref}=Re\left\{\frac{{\underset{\_}{I}}_{C,ref}}{{\underset{\_}{I}}_{A,ref}+{\underset{\_}{I}}_{B,ref}+{\underset{\_}{I}}_{C,ref}+{\underset{\_}{I}}_{D,ref}}\right\}$$

$$FC{C}_{real,D,Kx,ref}=Re\left\{\frac{{\underset{\_}{I}}_{D,ref}}{{\underset{\_}{I}}_{A,ref}+{\underset{\_}{I}}_{B,ref}+{\underset{\_}{I}}_{C,ref}+{\underset{\_}{I}}_{D,ref}}\right\}$$

und anhand eines gegenüber der oben gezeigten Tabelle erweiterten Bedingungssatzes der Fehlerort bestimmt. Im Schritt S5 erfolgt die Bestimmung des Knoten-Fehlerort-Wechselstromwiderstandswerts analog anhand einer Berechnungsvorschrift, der ein entsprechend erweitertes Ersatzschaltbild zugrunde liegt. Dabei ist zu beachten, dass die Berechnung bei einem Netz, das eine zusätzliche Querleitung 17 aufweist, nicht möglich ist.In step S4 Accordingly, reference residual current contribution values are determined for all nodes Kx with transverse lines and all outgoing lines $$FC{C}_{real.A.Kx.ref}=Re\left\{\frac{{\underset{\_}{I}}_{A.ref}}{{\underset{\_}{I}}_{A.ref}+{\underset{\_}{I}}_{B.ref}+{\underset{\_}{I}}_{C.ref}+{\underset{\_}{I}}_{D.ref}}\right\}$$

$$FC{C}_{real.B.Kx.ref}=Re\left\{\frac{{\underset{\_}{I}}_{B.ref}}{{\underset{\_}{I}}_{A.ref}+{\underset{\_}{I}}_{B.ref}+{\underset{\_}{I}}_{C.ref}+{\underset{\_}{I}}_{D.ref}}\right\}$$

$$FC{C}_{real.C.Kx.ref}=Re\left\{\frac{{\underset{\_}{I}}_{C.ref}}{{\underset{\_}{I}}_{A.ref}+{\underset{\_}{I}}_{B.ref}+{\underset{\_}{I}}_{C.ref}+{\underset{\_}{I}}_{D.ref}}\right\}$$

$$FC{C}_{real.D.Kx.ref}=Re\left\{\frac{{\underset{\_}{I}}_{D.ref}}{{\underset{\_}{I}}_{A.ref}+{\underset{\_}{I}}_{B.ref}+{\underset{\_}{I}}_{C.ref}+{\underset{\_}{I}}_{D.ref}}\right\}$$

and determined on the basis of a comparison with the table shown above condition set the fault location. In step S5 the determination of the node fault location AC resistance value is carried out analogously on the basis of a calculation rule which is based on a correspondingly extended equivalent circuit diagram. It should be noted that the calculation for a network, which is an additional transverse line 17 not possible.

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Cited patent literature

• DE 60018666 T2 [0003]

Claims (14)

Method for fault diagnosis in an electrical network (1, 1 ') comprising a ring structure with a plurality of lines (L12, L13, L23) and a plurality of nodes (K1, K2, K3), wherein at least two lines are outgoing lines (L12, L13), at least a line is a cross line (L23) connecting a pair of output lines (L12, L13), a node is a collecting node (K1) fed by an AC power source (4) to which the output lines (L12, L13) are connected, and at least two nodes are cross connection nodes (K2, K3) to which the pair of outgoing lines (L12, L13) are connected to the cross line (L23), characterized in that a node fault location AC resistance value between a fault location (F) on a faulty one Line and one of the nodes (K1, K2, K3) as a function of - Querwechselstromwiderstandswerten, each having a transverse AC resistance (Z _DEA1 , Z _DEA2 ) connected to an outgoing line (L12, L13) n describe energy conversion means (7a, 7b) in a negative sequence, - line AC resistance values respectively describing an AC resistance (Z _L12 , Z _L13 , Z _L23 ) of one of the lines (L12, L13, L23), and - outgoing line current values, one at the collecting node (K1) in one of the outgoing lines (L12, L13) current flowing (I _A , I _B ) in the negative sequence describe is determined. Method according to Claim 1 in which the determination of the node fault location AC resistance value takes place in additional dependence of a mains AC resistance value which describes an internal AC resistance (Z _N ) of the AC voltage source (4) in the negative sequence system. Method according to Claim 1 or 2 in which the determination of the node fault location AC resistance value takes place on the basis of a model on which an equivalent circuit of the negative sequence of the electrical network (1, 1 ') is based and which has a fault current (I _F ) flowing into and flowing through the negative sequence at the fault location (F) ) modeled. Method according to one of the preceding claims, wherein the node fault location AC resistance value is determined according to a calculation rule which is selected as a function of the faulty line or which depends on the faulty line. Method according to one of the preceding claims, wherein the faulty line is determined as a function of fault current contribution values which, for a respective outgoing line, contribute the current (I _A , I _B ) along the outgoing line (L12, L13) to a fault current ( I _F ) in the negative sequence. Method according to Claim 5 wherein the residual current contribution values are compared with reference residual current contribution values which describe, for a respective outgoing line (L12, L13), a contribution of a current along the outgoing line in case of an assumed error at the location of a cross connection node (K2, K3). Method according to Claim 5 or 6 in which a respective fault current contribution value is determined as a real part of the ratio of the current (I _A , I _B ) along the outgoing line (L12, L13) to the sum of the currents (I _A , I _B ) of all the outgoing lines (L12, L13) and / or reference fault current contribution values are used, each describing a real part of the ratio of the current along the outgoing line (L12, L13) to the sum of the currents of all the outgoing lines (L12, L13). Method according to one of the preceding claims, wherein a fault resistance value which describes an AC, reactive or reactive resistance between the collecting node (K1) and the fault location (F) is determined as a function of the node fault location AC resistance value and the line AC resistance value of a non-faulty line becomes. Method according to one of the preceding claims, wherein for fault diagnosis, a fault location information describing the distance from a busbar (2) or a location of the measurement of an outgoing line current value to the fault location (F) is determined. Method according to one of the preceding claims, wherein loads (6) at further nodes (K4) of the outgoing lines (L12, L13) remain unconsidered. Method according to one of the preceding claims, wherein a busbar (2) is used as the collecting node (K1) and / or an infeed network (5) is used as the alternating voltage source (4). Device (10, 10 ') for fault diagnosis in an electrical network (1, 1') having a ring structure, comprising a control unit (11) which is capable of carrying out a method according to one of the Claims 1 to 11 is set up. Device after Claim 12 in which the device (10, 10 ') comprises a measuring unit (8a, 8b) for measuring one or more of the outgoing line current values and / or a separating unit (9a, 9b), by means of which one of the outgoing current lines (L12, L13) from the collecting node (8) K1) is separable in dependence on the determined node fault location AC resistance value and / or a communication unit (12) for receiving the further outgoing line current value (s) and / or a memory unit (13) for storing the transverse alternating current resistance values and / or the line alternating current resistance values and / or of the AC line resistance value. Computer program product for loading into a memory unit (13) of a computer, comprising software code, with which a method according to one of the Claims 1 to 11 is performed when the computer program product is run on a computer.

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