DE102018113627B4 - 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 node (K1, K2, K3) as a function of cross-AC resistance values, each of which has 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, which each describe 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 for fault diagnosis in an electrical network having a ring structure with a plurality of lines and a plurality of nodes, at least two lines being outgoing lines, at least one line being a cross line which connects a pair of outgoing lines, a node being fed 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 an electrical network having a ring structure and a computer program product.

Such a method is, for example, from the document DE 600 18 666 T2 known, which discloses a method for calculating the distance of residual current in an electrical power supply network with an annular design.

The document DE 603 17 344 T2 relates to a fault location technique for a section of a high voltage line using measurements of current and voltage made at terminals located at one end of the section of the power line.

In modern electrical networks that have a ring structure, however, decentralized energy conversion devices, such as wind power plants, combined heat and power plants or small hydropower plants, are increasingly being connected. These typically have a synchronous or asynchronous machine, which makes the electrical network much more complex and conventional methods for fault diagnosis only deliver inadequate 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 solve this problem, the invention provides in a method of the type mentioned at the outset that a node fault location alternating current resistance value between a fault location on a faulty line and one of the nodes as a function of transverse alternating current resistance values, each having a transverse alternating current resistance of an energy conversion device connected to an outgoing line Describe counter system, AC line resistance values, which each describe an AC resistance of one of the lines, and outgoing line current values, which each describe a current flowing in one of the outgoing lines at the common node in the opposite system.

The invention is based on the knowledge that the node fault location alternating current resistance value, which is particularly relevant for the location of the fault, when the energy conversion devices are connected to the electrical network is significantly influenced by their transverse alternating current resistance. The invention makes use of the fact that the node fault location alternating current resistance value can be determined with sufficient accuracy by considering the opposite system of the electrical network and the transverse alternating current resistance value of the connected energy conversion devices is typically known over wide operating state ranges and in particular is also constant. With additional consideration of the line AC resistance values, which are typically also known, and the outgoing line current values measured, for example, in the vicinity of the collecting node, the node fault location AC resistance value can then be determined with little effort for fault diagnosis.

The method according to the invention thus advantageously enables fault diagnosis in complex electrical networks with a ring structure, even when connected to these energy conversion devices. In particular, the method according to the invention allows the node fault location alternating current resistance value to be determined with high accuracy on the basis of known a priori data in the form of the transverse alternating current resistance values and the line alternating current resistance values and outgoing line current values measured in the vicinity of the collecting node. 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.

As a rule, the electrical network is a multi-phase, in particular three-phase, AC network, such as a medium-voltage or low-voltage power supply network. The term "negative system" in the sense The invention relates to an analytical view of the electrical network according to the symmetrical component method, the network being divided into a co-system, the opposite system and a zero system. The AC resistance values can each describe an impedance or an admittance. They can be purely real or complex.

The energy conversion devices are usually decentralized energy conversion devices. Examples of energy conversion devices are wind power plants, combined heat and power plants or hydropower plants. The energy conversion devices can have a synchronous machine or asynchronous machine designed for feeding energy into the electrical network. In a synchronous machine, the cross-alternating current resistance value can be derived or determined from information on the nameplate and the like, since it is essentially a result of the design. In asynchronous machines, the transverse AC resistance value depends to a small extent on the slip. However, since asynchronous machines are usually operated with very little slip, a cross-AC resistance value can be used for an asynchronous machine with 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. In this case too, a transverse AC resistance value can be used if the converter is designed to be fed into the opposite system.

The method according to the invention can have a step of calling up the transverse AC resistance values and / or the line AC resistance values, for example from a storage unit or / or by means of a communication unit. Furthermore, the method can have a step of measuring the outgoing line current values. The measurement is preferably carried out at or close to the collecting node.

In the method according to the invention, the node fault location alternating current resistance value is preferably determined as an additional function of an alternating current mains resistance value which describes an internal alternating current resistance of the alternating voltage source in the negative system. By taking into account the internal AC resistance of the AC voltage source, the accuracy of the error diagnosis can be improved.

The node fault location alternating current resistance value is preferably determined using a model which is based on an equivalent circuit diagram of the counter system of the electrical network and which models a fault current flowing into the counter system 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 can be viewed as from a current source feeding the negative sequence system, which causes the measured currents described by the outgoing line current values. Since the fault location can lie between any pair of neighboring nodes, an equivalent circuit diagram depending on the fault location can be used.

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

By means of an additional step, within the scope of the method according to the invention, the faulty line can be determined as a function of fault current contribution values which, for a respective outgoing line, describe a contribution of the current along the outgoing line to a fault current in the opposite system 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 event of an assumed fault at the location of a cross-connection node. The reference residual current contribution values can have been determined by means of a simulation, in particular using the equivalent circuit diagram, or a measurement in advance or can be determined in the context of the method according to the invention.

In addition, a respective residual current contribution value can 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 fault current contribution values can be used, each of which describes a real part of the ratio of the current along the outgoing line to the sum of the currents of all outgoing lines.

Within the scope of the method according to the invention, an error resistance value which describes an AC, reactive or active resistance between the collecting node and the error location can also be determined depending on the node fault location alternating current resistance value and the line alternating current resistance value of a non-faulty line. The node fault location alternating current resistance value can therefore be interpreted as a proportion of the line alternating current resistance value of the faulty line, so that the fault resistance value can be calculated by simply adding the node fault location alternating current resistance value to one or more line alternating current resistance values of the non-faulty lines.

In the method for fault diagnosis according to the invention, 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 particularly preferably determined. The fault location information can be determined as a function of the fault resistance value or its complex components. The fault location information will be determined in particular on the basis of a function which specifies the distance as a function of the complex component, that is to say 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 coverage of the network.

In addition, loads at other nodes of the outgoing lines are preferably not taken into account in the method according to the invention. This is based on the knowledge that loads of this type generally have no influence on the negative system that affects the desired accuracy of the fault diagnosis.

A busbar and / or a feed-in network is preferably used as the bus node. The method can therefore be carried out in the immediate vicinity of the busbar or a mains transformer, where the AC resistance values and outgoing line current values required for the determination can be easily accessed with particular advantage.

In addition, the invention relates to a device for fault diagnosis in an electrical network having a ring structure, comprising a control device which is set up to carry out the method according to the invention. The device according to the invention is preferably designed as a relay device for use on the bus node or on the busbar.

The device according to the invention can be a measuring unit for measuring one or more of the outgoing line current values and / or a separation unit, by means of which one of the outgoing current lines can be separated from the collecting node depending on the determined node fault location alternating current resistance value and / or a communication unit for receiving the further outgoing line current values and / or have a storage unit for storing the cross-AC resistance values and / or the line AC resistance values and / or the mains AC resistance value.

The invention also 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 method according to the invention is carried out when the computer program product is executed on a computer.

All explanations of the method according to the invention can be transferred analogously to the device according to the invention and the computer program product according to the invention, so that the advantages mentioned above can also be achieved with these.

• 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 result from the exemplary embodiments described below, such as with reference to the drawings. These are schematic representations and show:

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

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

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

In the outgoing lines L12 , L13 are also each a measuring unit 8a , 8b and a separation unit 9a , 9b arranged. The measuring units 8a , 8b are used to measure current along the outgoing lines L12 , L13 and the separation units 9a , 9b to separate the outgoing pipe L12 , L13 from the collection node K1 educated. The separation units 9a , 9b as well as the measuring units 8a , 8b are in close proximity to the collection node K1 , namely much closer to the collection node K1 than at the energy conversion facilities 7a , 7b , arranged. The collection node K1 , the ac voltage source 4th , the measuring units 8a , 8b and the separation units 9a , 9b can be located, for example, in a transformer station or the like, from which the energy conversion devices 7a , 7b are several tens or hundreds of meters or several kilometers away.

2nd is an equivalent circuit diagram of a counter system of the electrical network 1 in a first representation. The opposite system is based on an analysis of the electrical network 1 according to the method of symmetrical components.

There is an AC resistor in it Z _L12 the outgoing line L12 , an AC resistor Z _L13 the outgoing line L13 and an AC resistor Z _L23 the outgoing line L23 modeled. The AC resistance Z _L13 results as a series connection of AC resistors Z _L14 , Z _L34 the outgoing pipe sections L14 , L34 . At the fault location F assumed here between the cross-connection nodes K2 , K3 the AC _resistance Z _L23 also results as a series connection of an AC resistance Z _L2F the line section L2F and an AC resistor Z _L3F the line section L3F. The decentralized energy conversion facilities 7a , 7b are as cross AC resistors Z _DEA1 , Z _DEA2 modeled. In addition there is an internal AC resistance Z _N the AC voltage source 4th modeled. The load remains in the equivalent circuit diagram 6 evidently disregarded, since their cross-impedance is significantly larger than the impedances of the cross-AC resistors Z _DEA1 , Z _DEA2 can be assumed and therefore has little influence on the accuracy of the calculation. However, it is of course alternatively conceivable that the load 6 to be taken into account in the equivalent circuit diagram.

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

Although the AC resistors act as impedances with a Z. , admittances can of course also be used to describe the AC resistances. Unless otherwise stated, sizes with an underscore are complex and relate to the opposite system.

3rd is a block diagram of an embodiment of an apparatus 10th for fault diagnosis in the electrical network 1 .

The device 10th comprises 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 collection node K1 is separable, and a communication unit 12th and a storage unit 13 . The communication unit 12th is with that of the other outgoing management L13 assigned measuring unit 13 connected for data transmission, which in turn is part of a further device for fault diagnosis 10 ' is. The devices 10th , 10 ' can therefore be considered as multi-function relays that are installed, for example, in the aforementioned substation.

In an alternative embodiment, the device comprises 10th Units of measurement 8a , 8b and the separation units 9a , 9b for a respective outgoing line L12 , L13 , the control unit 11 and the storage unit 13 . The control unit 11 and the storage unit 13 central units used to receive data from the measuring units 8a , 8b and to control the separation units 9a , 9b are set up.

• 4 ist ein Flussdiagramm eines Ausführungsbeispiels des Verfahrens zur Fehlerdiagnose im elektrischen Netz 1.

The control unit is in both exemplary embodiments 11 to carry out a method for fault diagnosis in the electrical network 1 set up that is described in more detail below:

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

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

In a subsequent step S2 outgoing line current values are recorded, each one at the common node K1 into one of the outgoing lines L12 , L13 flowing current I _A , I _B describe in the opposite system. The measurement is carried out using the measuring units 8a , 8b , for which purpose measured values from the measuring unit 8b via the communication unit 12th 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 for a respective outgoing line L12 , L13 a contribution of electricity 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 the sum of the currents of all outgoing lines L12 , L13 using the following equations, the operator Re {·} describing the real part: $$F\mathrm{C.}{\mathrm{C.}}_{real,A,F}=Re\left\{\frac{{\underset{\_}{\mathrm{I.}}}_A}{{\underset{\_}{\mathrm{I.}}}_A+{\underset{\_}{\mathrm{I.}}}_B}\right\}$$

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

In one step S4 become the residual current contribution values FCC _{real, A, F} , FCC _{real, B, F} with 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} compared that for a respective outgoing line L12 , L13 the contribution of a stream I _{A, ref} , I _{B, ref} which, in the event of an assumed fault at the location of a cross-connection node K2 , K3 into the outgoing 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 known at the time the error occurs (a priori) and can be determined by simulation or measurement. They are in the storage unit 13 and are saved 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: $$F\mathrm{C.}{\mathrm{C.}}_{real,A,\mathrm{<figure-callout\; id="2"\; label="K"\; filenames="DE102018113627B4\_0029.png"\; state="\{\{state\}\}">K</figure-callout>}\mathrm{2,}ref}=Re\left\{\frac{{\underset{\_}{\mathrm{I.}}}_{A,ref,K\mathrm{2nd}}}{{\underset{\_}{\mathrm{I.}}}_{A,ref,K\mathrm{2nd}}+{\underset{\_}{\mathrm{I.}}}_{B,ref,K\mathrm{2nd}}}\right\}$$

$$F\mathrm{C.}{\mathrm{C.}}_{real,B,\mathrm{<figure-callout\; id="2"\; label="K"\; filenames="DE102018113627B4\_0029.png"\; state="\{\{state\}\}">K</figure-callout>}\mathrm{2,}ref}=Re\left\{\frac{{\underset{\_}{\mathrm{I.}}}_{B,ref,K\mathrm{2nd}}}{{\underset{\_}{\mathrm{I.}}}_{A,ref,K\mathrm{2nd}}+{\underset{\_}{\mathrm{I.}}}_{B,ref,K\mathrm{2nd}}}\right\}$$

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

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

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

Describe it I _{A, ref, K2} and I _{A, ref, K3} 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 if the fault is accepted 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, there is the special case $${\text{FCC}}_{\text{real},\text{A},\text{F}}={\text{FCC}}_{\text{real},\text{A},\text{K}\mathrm{2,}\text{ref}}\text{respectively}.{\text{FCC}}_{\text{real},\text{B},\text{F}}={\text{FCC}}_{\text{real},\text{B},\text{K}\mathrm{2,}\text{ref},}$$

the one error immediately at the cross-connection node K2 or within the energy conversion facility 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 one error immediately at the cross-connection node K3 or within the energy conversion facility 7b describes, called. In addition, residual current contribution values have FCC _{real, A, F} > 1 or FCC _{real, A, F} <0 or FCC _{real, B, F} > 1 or FCC _{real, B, F} <0 to a non-three-pole open circuit 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 a neighboring node K1 , K2 , K3 , K4 determined. In the in 2nd shown case of a fault on the cross line L23 can therefore optionally be the value of the AC resistance as the node fault location AC resistance value 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 found to be a faulty line.

The node fault location alternating current resistance value is determined in accordance with a calculation rule which is dependent on the faulty line L23 is selected or by the faulty line L23 is dependent. This calculation rule is carried out by the control unit 11 executed. The control unit calls 11 known cross-AC resistance values, each one of the cross-AC resistances Z _DEA1 , Z _DEA2 , describe AC line resistance values, each one of the AC resistances Z _L12 , Z _L23 , Z _L34 , Z _L14 describe, as well as a line AC resistance value, the internal AC resistance Z _N describes from the storage unit 13 from. The cross AC resistance values, the line AC resistance values, the line AC resistance value and those in the step S2 outgoing line current values are variables of the calculation specification.

• Es sind folgende Werte a priori bekannt: Z _L12 , Z _L23 , Z _L34 , Z _L14 , Z _DEA1 , Z _DEA2 . Als gemessene bzw. abgerufene Werte sind ferner I _A , I _B bekannt. Aus der Ermittlung der fehlerhaften Leitung folgt der Zusammenhang Z _L23 = Z _L2F + Z _L3F für die Knoten-Fehlerort-Wechselstromwiderstandswerte. Zur besseren Verdeutlichung der Herleitung wird dabei auf 5 Bezug genommen, die eine äquivalente zweite Darstellung des Ersatzschaltbilds in 2 ist.

In the following, the network theoretical derivation of this calculation rule is based on the in 2nd shown error on the cross line L23 described, but this does not mean that the described analysis and transformation steps also by the control unit 11 should be carried out by yourself:

• The following values are known a priori: Z _L12 , Z _L23 , Z _L34 , Z _L14 , Z _DEA1 , Z _DEA2 . As measured or retrieved values are also I _A , I _B known. The relationship Z _L23 = Z _L2F + Z _L3F for the node fault location AC _{resistance values} follows from the determination of the faulty line. For better clarification of the derivation, 5 Reference, which is an equivalent second representation of the equivalent circuit in 2nd is.

In 5 are also a first partial fault current I _LF in a branch shown on the left between the fault location F and a neighboring 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 to the fault current I _F . There are also tensions U _L and U _R via AC resistances connected to the neighboring nodes, here voltages U _DEA1 , U _DEA2 across the cross ac resistors Z _DEA1 respectively. Z _DEA2 , shown.

• Für die Spannung U _N gilt: $${\underset{\_}{U}}_N=-\left({\underset{\_}{I}}_A+{\underset{\_}{I}}_B\right)\cdot {\underset{\_}{Z}}_N$$
  

The partial fault currents I _LF , I _LR can be determined as follows:

• For the tension U _N applies: $${\underset{\_}{U}}_N=-\left({\underset{\_}{\mathrm{I.}}}_A+{\underset{\_}{\mathrm{I.}}}_B\right)\cdot {\underset{\_}{\mathrm{Z.}}}_N$$
  

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

This results in one stitch 14 following sizes: $${\underset{\_}{U}}_L={\underset{\_}{U}}_N-{\underset{\_}{\mathrm{I.}}}_A\cdot {\underset{\_}{\mathrm{Z.}}}_{L\mathrm{12th}}={\underset{\_}{U}}_{\mathrm{<figure-callout\; id="1"\; label="D\; E\; A"\; filenames="DE102018113627B4\_0033.png"\; state="\{\{state\}\}">D\; </figure-callout>}EA1}$$

$${\underset{\_}{\mathrm{I.}}}_{\mathrm{<figure-callout\; id="1"\; label="D\; E\; A"\; filenames="DE102018113627B4\_0033.png"\; state="\{\{state\}\}">D\; </figure-callout>}EA1}=-\frac{{\underset{\_}{U}}_{DEA1}}{{\underset{\_}{\mathrm{Z.}}}_{\mathrm{<figure-callout\; id="1"\; label="D\; E\; A"\; filenames="DE102018113627B4\_0033.png"\; state="\{\{state\}\}">D\; </figure-callout>}EA1}}$$

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

The same results for a stitch 15 : $${\underset{\_}{U}}_R={\underset{\_}{U}}_N-{\underset{\_}{\mathrm{I.}}}_B\cdot \left({\underset{\_}{\mathrm{Z.}}}_{\mathrm{<figure-callout\; id="14"\; label="L"\; filenames="DE102018113627B4\_0032.png"\; state="\{\{state\}\}">L</figure-callout>}14}+{\underset{\_}{\mathrm{Z.}}}_{L34}\right)={\underset{\_}{U}}_{DEA\mathrm{2nd}}$$

$${\underset{\_}{\mathrm{I.}}}_{\mathrm{<figure-callout\; id="1"\; label="D\; E\; A"\; filenames="DE102018113627B4\_0033.png"\; state="\{\{state\}\}">D\; </figure-callout>}EA1}=-\frac{{\underset{\_}{U}}_{DEA\mathrm{2nd}}}{{\underset{\_}{\mathrm{Z.}}}_{DEA\mathrm{2nd}}}$$

$${\underset{\_}{I}}_{R-F}={\underset{\_}{I}}_B+{\underset{\_}{I}}_{DEA2}={\underset{\_}{I}}_B+\frac{\left({\underset{\_}{I}}_A+{\underset{\_}{I}}_B\right)\cdot {\underset{\_}{Z}}_N+{\underset{\_}{I}}_B\cdot \left({\underset{\_}{Z}}_{L14}+{\underset{\_}{Z}}_{L34}\right)}{{\underset{\_}{Z}}_{DEA2}}$$

For the partial fault currents I _LF , I _LR follows solely from the known values: $${\underset{\_}{\mathrm{I.}}}_{L-F}={\underset{\_}{\mathrm{I.}}}_A+{\underset{\_}{\mathrm{I.}}}_{\mathrm{<figure-callout\; id="1"\; label="D\; E\; A"\; filenames="DE102018113627B4\_0033.png"\; state="\{\{state\}\}">D\; </figure-callout>}EA1}={\underset{\_}{\mathrm{I.}}}_A+\frac{\left({\underset{\_}{\mathrm{I.}}}_A+{\underset{\_}{\mathrm{I.}}}_B\right)\cdot {\underset{\_}{\mathrm{Z.}}}_N+{\underset{\_}{\mathrm{I.}}}_A\cdot {\underset{\_}{\mathrm{Z.}}}_{L\mathrm{12th}}}{{\underset{\_}{\mathrm{Z.}}}_{\mathrm{<figure-callout\; id="1"\; label="D\; E\; A"\; filenames="DE102018113627B4\_0033.png"\; state="\{\{state\}\}">D\; </figure-callout>}EA1}}$$

$${\underset{\_}{\mathrm{I.}}}_{R-F}={\underset{\_}{\mathrm{I.}}}_B+{\underset{\_}{\mathrm{I.}}}_{DEA\mathrm{2nd}}={\underset{\_}{\mathrm{I.}}}_B+\frac{\left({\underset{\_}{\mathrm{I.}}}_A+{\underset{\_}{\mathrm{I.}}}_B\right)\cdot {\underset{\_}{\mathrm{Z.}}}_N+{\underset{\_}{\mathrm{I.}}}_B\cdot \left({\underset{\_}{\mathrm{Z.}}}_{\mathrm{<figure-callout\; id="14"\; label="L"\; filenames="DE102018113627B4\_0032.png"\; state="\{\{state\}\}">L</figure-callout>}14}+{\underset{\_}{\mathrm{Z.}}}_{L34}\right)}{{\underset{\_}{\mathrm{Z.}}}_{DEA\mathrm{2nd}}}$$

From one round of a total stitch from the stitches 14 , 15 and a stitch 16 there is also: $${\underset{\_}{U}}_L-{\underset{\_}{\mathrm{I.}}}_{L-F}\cdot {\underset{\_}{\mathrm{Z.}}}_{L-F}={\underset{\_}{U}}_R-{\underset{\_}{\mathrm{I.}}}_{R-F}\cdot {\underset{\_}{\mathrm{Z.}}}_{R-F}$$

Describe it 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 Z _L23 = Z _L2F + Z _L3F applies in the _present case, it follows: $${\underset{\_}{U}}_L-{\underset{\_}{\mathrm{I.}}}_{L-F}\cdot {\underset{\_}{\mathrm{Z.}}}_{L-F}={\underset{\_}{U}}_R-{\underset{\_}{\mathrm{I.}}}_{R-F}\cdot \left({\underset{\_}{\mathrm{Z.}}}_F-{\underset{\_}{\mathrm{Z.}}}_{L-F}\right)$$

By transforming the equation one obtains for the node fault location alternating current resistance value solely from the known values: $${\underset{\_}{\mathrm{Z.}}}_{L-F}=\frac{{\underset{\_}{U}}_L-{\underset{\_}{U}}_R+{\underset{\_}{\mathrm{I.}}}_{R-F}\cdot {\underset{\_}{\mathrm{Z.}}}_F}{{\underset{\_}{\mathrm{I.}}}_{L-F}+{\underset{\_}{\mathrm{I.}}}_{R-F}}=\frac{{\underset{\_}{U}}_{DEA1}-{\underset{\_}{U}}_{DEA\mathrm{2nd}}+{\underset{\_}{\mathrm{I.}}}_{\mathrm{3rd}F}\cdot {\underset{\_}{\mathrm{Z.}}}_{L23}}{{\underset{\_}{\mathrm{I.}}}_{\mathrm{2nd}F}+{\underset{\_}{\mathrm{I.}}}_{\mathrm{3rd}F}}$$

Alternatively, the other node fault location AC resistance value can 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 rules for faults on other faulty lines. According to an alternative embodiment, the control unit performs 11 the analysis and transformation steps described above as part of the process itself.

In a subsequent step S6 depending on the node fault location alternating current resistance value and the line alternating current resistance value of a non-faulty line, an error resistance value which has an alternating current, reactive or active resistance between the collecting node K1 and describes the fault location F.

For this purpose, only the AC line resistance value for the AC resistance is used Z _L12 the outgoing line L12 to the node fault location AC resistance value for the AC resistance Z _L2F added: $${\underset{\_}{\mathrm{Z.}}}_{A-F}={\underset{\_}{\mathrm{Z.}}}_{L\mathrm{12th}}+{\underset{\_}{\mathrm{Z.}}}_{L-F}$$

Alternatively, the AC line resistance value for the AC resistance Z _L13 the outgoing line L13 to the node fault location AC resistance value for the AC resistance Z _L3F added: $${\underset{\_}{\mathrm{Z.}}}_{B-F}={\underset{\_}{\mathrm{Z.}}}_{\mathrm{<figure-callout\; id="14"\; label="L"\; filenames="DE102018113627B4\_0032.png"\; state="\{\{state\}\}">L</figure-callout>}14}+{\underset{\_}{\mathrm{Z.}}}_{L34}+{\underset{\_}{\mathrm{Z.}}}_{R-F}$$

In a subsequent step S7 an error location information describing the distance from the busbar or a location of the measurement of an outgoing line current value to the error location F is determined for error diagnosis. For this purpose, either resistances R _AF = Re { Z _AF }, R _BF = Re { Z _BF } or reactances X _AF = Im { Z _AF }, X _BF = Im { Z _BF } are determined, the operator Im {·} den Imaginary part describes. From known resistance or reactance coatings of the network 1 can thus remove the fault location F from the collection node K1 or from the location of the measurement. This shows 6 a function of device removal 10th to places in the electrical network 1 over a component of a fault resistance value.

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

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

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

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

Doing so in step S2 for all outgoing lines outgoing line current values, each a current I _A , I _B , I _C , I _D describe captured. In step S3 are determined in accordance with residual current contribution values for a respective outgoing line: $$F\mathrm{C.}{\mathrm{C.}}_{real,A,F}=Re\left\{\frac{{\underset{\_}{\mathrm{I.}}}_A}{{\underset{\_}{\mathrm{I.}}}_A+{\underset{\_}{\mathrm{I.}}}_B+{\underset{\_}{\mathrm{I.}}}_{\mathrm{C.}}+{\underset{\_}{\mathrm{I.}}}_D}\right\}$$

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

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

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

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

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

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

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 are determined according to reference residual current contribution values for all nodes Kx with cross lines and all outgoing lines $$F\mathrm{C.}{\mathrm{C.}}_{real,A,Kx,ref}=Re\left\{\frac{{\underset{\_}{\mathrm{I.}}}_{A,ref}}{{\underset{\_}{\mathrm{I.}}}_{A,ref}+{\underset{\_}{\mathrm{I.}}}_{B,ref}+{\underset{\_}{\mathrm{I.}}}_{\mathrm{C.},ref}+{\underset{\_}{\mathrm{I.}}}_{D,ref}}\right\}$$

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

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

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

and determines the location of the fault on the basis of a set of conditions that is expanded compared to the table shown above. In step S5 the node fault location alternating current resistance value is determined analogously on the basis of a calculation rule which is based on a correspondingly expanded equivalent circuit diagram. It should be noted that the calculation for a network that has an additional cross line 17th has, is not possible.

Claims (14)

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), 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) depending on - Cross-AC resistance values, each of which describes a cross-AC resistance ( Z _DEA1 , Z _DEA2 ) of an energy conversion device (7a, 7b) connected to an outgoing line (L12, L13) in a counter system, - AC line resistance values, each of which has an AC resistance ( Z _L12 , Z _L13 , Z _L23) ) describe one of the lines (L12, L13, L23), and - outgoing line current values, which each describe a current ( I _A , I _B ) flowing in the opposite system at the common node (K1) into one of the outgoing lines (L12, L13). Procedure according to Claim 1 , wherein the node fault location alternating current resistance value is determined as an additional function of a mains alternating current resistance value which describes an internal alternating current resistance ( Z _N ) of the alternating voltage source (4) in the opposite system. Procedure according to Claim 1 or 2nd , wherein the node fault location alternating current resistance value is determined using a model which is based on an equivalent circuit diagram of the counter system of the electrical network (1, 1 ') and which has a fault current ( I _F. ) flowing into and flowing through the counter system at the fault location (F) ) modeled. Method according to one of the preceding claims, wherein the node fault location alternating current resistance value is determined according to a calculation rule which is selected depending on the faulty line or which is dependent 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, make a contribution of the current ( I _A , I _B ) along the outgoing line (L12, L13) to a fault current caused by the fault ( I _F ) describe in the opposite system. Procedure according to Claim 5 , the residual current contribution values being compared with reference residual current contribution values which describe a contribution of a current along the outgoing line for a respective outgoing line (L12, L13) in the event of an assumed fault at the location of a cross-connection node (K2, K3). Procedure according to Claim 5 or 6 , wherein a respective residual 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 outgoing lines (L12, L13) and / or reference residual current contribution values are used, each of which describes 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). Method according to one of the preceding claims, wherein depending on the node fault location alternating current resistance value and the line alternating current resistance value of a non-faulty line, a fault resistance value that describes an alternating current, reactive or active resistance between the collecting node (K1) and the fault location (F) is determined becomes. Method according to one of the preceding claims, wherein error location information describing the distance from a busbar (2) or a location of the measurement of an outgoing line current value to the error location (F) is determined for error diagnosis. Method according to one of the preceding claims, loads (6) at further nodes (K4) of the outgoing lines (L12, L13) being disregarded. Method according to one of the preceding claims, wherein a busbar (2) is used as the bus node (K1) and / or a feeding network (5) is used as the AC 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 used to carry out a method according to one of the Claims 1 to 11 is set up. Device after Claim 12 , the device (10, 10 ') - 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 ( K1) can be separated depending on the determined node fault location alternating current resistance value and / or - a communication unit (12) for receiving the further outgoing line current values and / or - a storage unit (13) for storing the cross-current resistance values and / or the line alternating current resistance values and / or the mains alternating current 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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