WO2016071070A1

WO2016071070A1 - Separating faulty network sections of a low voltage network from additional network sections

Info

Publication number: WO2016071070A1
Application number: PCT/EP2015/073272
Authority: WO
Inventors: Alfred Einfalt; Tobias GAWRON-DEUTSCH; Thomas Ritter; Andreas LUGMAIER; Ralf MOSSHAMMER
Original assignee: Siemens Ag Österreich
Priority date: 2014-11-05
Filing date: 2015-10-08
Publication date: 2016-05-12
Also published as: DE102014222598A1

Abstract

The invention relates to a method for separating faulty network sections of a low voltage network from additional network sections of the low voltage network, characterized in that a plurality of network sections are each separated from each other by a power switch (5, 6), wherein adjacent power switches (5, 6) have a wireless data connection (8) to each other in order to determine a line difference and disconnect the network section therebetween from the low voltage network, if a specified differential value of the currents which flow through adjacent power switches (5, 6) is exceeded, which differential value corresponds to an error. An extensive failure of the voltage supply in case of fault can thus be reduced.

Description

description

Disconnecting faulty network sections of a

Low-voltage network of other network sections

Technical area

The invention relates to a method for separating

faulty network sections of a low-voltage network of other network sections of the low-voltage network.

Low voltage grids are part of the electricity grid

Distribution of electrical energy to most of the final electrical consumers consisting of low voltage equipment. To avoid voltage losses are

Low-voltage networks in the spatial extent limited to a range of some 100 m to a few kilometers. They will therefore be regional over

Transformer stations (local network stations) from one

fed over higher-level medium-voltage network. They are commonly used in Europe with a mains voltage of 230 V.

(between each outer conductor and the neutral conductor) or 400 V (between the three outer conductors), in any case only up to 1000 V operated. Rated power of individual

Local grid transformers may vary depending on the destination grid planning of the respective distribution system operator, but are typically 250 or 400kVA for rural areas and 630 or 800kVA for inner city areas.

The classic network operation is due to the increasing penetration of decentralized, mostly renewable energy generation facilities (DEA) as well as the increasing

Development of electromobility facing great challenges posed. This is understood as a decentralized

Power Generation Plant (DEA), for example, a

Photovoltaic system or a wind turbine.

State of the art

In recent years, there has been a trend towards so-called "smart grids", which are the intelligent power grids

communicative networking and control of power generators,

Save, electrical consumers and network resources in power transmission and distribution networks of the electricity supply. The network stability in energy transmission and

Energy distribution networks are mainly divided into two problem areas: The predominant problem in rural energy distribution networks is the voltage, which is also referred to as the "U-problem." In urban areas

Power distribution networks, which have rather short line lengths due to the load density, is less the

Tension maintenance rather than the problem of utilization of resources prevailing. This is sometimes referred to as the "I problem." Decentralized feeders initially reduce the high utilization of lines and transformers, but in the rarest cases they also violate the recovery limits, and the probable bigger problem can be uncoordinated, additional loading burdens of electric vehicles.

In addition, e.g. in suburban areas

Network sections within a network area have both a rural and an urban character. To the last participant still by standards (for example by the EN50160) specified voltage limits or not to overload the resources, either network expansion must be operated or an active network management system can be used. The latter specifically targets producers, flexible consumers or even storage facilities

Power distribution to in order to maintain network operation in accordance with standards.

For urban networks, an additional solution is to mesh the networks. This is possible because of the historical growth of electricity grids, especially in the urban area, where there are a large number of mostly openly operated coupling points that can be closed for meshing. This will be the

Short circuit power raised in the network area and the

described effects are largely reduced.

In practice, the overall impedance becomes clear

reduced, whereby the often cited so-called

"Copper plate" is created.

The problem now is the treatment of this meshed

Network in case of error. A mesh network in electric power engineering is a special form of power network, which in the topology is determined by a multiplicity of knots and meshes. Mesh nets usually have several

Feed-in points and distribute electrical energy over several connecting lines to the individual consumers. In addition to the high short-circuit power that must be mastered in meshed networks, the selectivity suffers in the event of a fault and thus the number of affected customers increases. Usually, the protection concept in low - voltage networks consists of fuses (=

Overcurrent protection device, which interrupts the circuit by melting a fusible conductor, if the Amperage exceeds a certain value for a sufficient time) or non-directional protective relays at the outputs of the busbars of the transformer station of

corresponding low-voltage network. In the event of an error, this means that the fault location can not be switched off selectively. Instead, the entire network area must be switched off and the troubleshooting started.

An opposite problem arises with island-capable microgrids. A microgrid is generally a group of generators, memories and loads that are usually network-connected to higher-level networks, but can become autonomous in the event of major disruptions or market incentives.

In off-grid operation, where the supply is provided by distributed power generation systems (DEA), the available short-circuit power decreases in the event of a fault. DEA are usually only capable of 1.1 to 1.2 times the rated current in the

To deliver error case. This can be the necessary

Short-circuit current can not be supplied for quick release of the standard fuse used.

Since the usual protection concept for low-voltage networks is therefore passive, in meshed operation at a

Error case large-scale failures arise. In island operation, the errors could no longer be reliably resolved in the case of large blackouts. At the beginning of the electrical power supply, the concept of meshing was quite the practice and was only in

more recently by separation into e.g. open

Replaced double rings. The advantage is that it can react to errors much more selectively and also a structural n-1 security (if a

Line section fails, all customers can be immediately re-supplied from both sides after switching) is given in low-voltage networks.

Particularly in high and medium voltage networks, active concepts of network protection are already used for meshed operation. The network protection describes the technical

Arrangements with which the electric

Energy transmission network against the effects of errors

(Short circuit, ground fault) is protected in individual power supplies. The line protection devices measure the current via the current transformer and / or the voltage across the voltage transformer

distinguish the error case from normal operation. If the error is detected, then the associated circuit breaker is switched off and thus the faulty network segment is disconnected from the rest of the supply network. This will thus be protected from the effects of the error. Thus, in medium and high voltage networks usually distance protection devices or UMZ protection devices are used. With a DEV protection (independent maximum current time protection), when a set current amount is exceeded, eg. B. 400 A, after the associated delay time

Signal issued to switch off the circuit breaker. The delay time is independent of the actual flowing current. With existing message paths will also

Line differential protection devices used. These are in

In contrast to the distance and overcurrent protection devices, they are strictly selective. They each have a protection area between two current transformers (or both on both sides of the

Current transformer). For line differential protection, the currents are determined on both sides of the circuit breaker. The sum of the inflowing streams should be equal to the sum of the outflowing streams. If this basic requirement is not met, the protection triggers. A message path is used to transmit the measured value of the current from one side of the line to the other side. Thus, both protection devices know their own and the power of the remote station. If a difference is detected here, it is assigned via the assigned

Circuit breaker disconnected the line. digital

Protective devices can usually be operated as a UMZ protection in case of failure of the message path. However, then lacks the strict selectivity of

Line differential protection. In addition, as reserve protection for the line, distance and / or

Protection devices on both sides of the line with in use.

In principle, a directed overcurrent time protection (UMZ-R) would be possible, for example by means of selectivity over a

Staggering of the trip time and the direction information, but this is only really selective if the

Topology of the voltage network remains the same. However, this is not the case with medium-voltage and in particular low-voltage networks, whereby corresponding

Engineering effort would arise.

For a directional differential protection in

Low-voltage networks are also no

Message links between the protection devices.

Creating your own physical data connections would not be profitable. Presentation of the invention

An object of the present invention is to provide a network protection solution which is suitable both for meshed low-voltage networks and for autonomous networks

Low-voltage networks (island operation) reduced a large-scale failure of the power supply in case of failure.

This object is achieved by a method having the features of patent claim 1 and comprises a method for

Disconnecting faulty network sections of a

Low voltage network of further network sections of the

Low-voltage network, wherein a plurality of network sections are each separated by a circuit breaker, wherein adjacent circuit breaker to each other

Determination of a line difference in wireless

Data connection stand and disconnect the lying between them network section from the low voltage network, when a predetermined, an error corresponding difference value of the currents flowing through adjacent circuit breakers, is exceeded.

It is therefore proposed to be an intelligent

Low-voltage circuit breaker included

To provide protection functionality, where by "intelligent" is meant that the individual

Circuit breaker has so much knowledge about his environment and the laws in it to clarify with his neighbors a case of error and all inventive

Circuit breakers collectively ensure reliable grid operation. The structure of the circuit breaker for the method ^according to the invention thus corresponds to a multi-agent system in which different agents in loser Coupling pursue a higher-level goal - the network protection.

Functionally, this means that two adjacent

Circuit breaker each form a line differential protection to a selective shutdown of errors in

(partly) meshed low-voltage networks or island-capable microgrids. The circuit-breaker can be modeled as an agent having the following resources: measuring the currents on the connected lines, operating the disconnecting switches for these lines.

An inventive circuit breaker is consequently

at least have the following knowledge:

- topological information about the neighboring ones

breakers

- Current throughput through the adjacent circuit breakers. He may also have the following knowledge:

- Load limits of the connected cables

- technical information about the neighboring ones

Circuit breakers, such as reaction speed

if appropriate, information on how topology changes relating to the adjacent circuit breakers can be detected.

If the circuit breaker over all points of here

enumerated knowledge, he can autonomously all

Decisions that fall within the remit of the

Line differential protection fall.

By using wireless communication, it is not necessary to provide physical data connections between the circuit breakers. For the application of the method according to the invention must be determined which circuit breaker the two

Line ends of a network section are assigned, so which circuit breaker with respect to a particular

Netzabschnittes considered to be adjacent. There are at least three options for this:

First, it can be provided that the determination of which circuit breakers are adjacent and in wireless data communication with one another for the purpose of determining a line difference is performed by a circuit breaker higher than the circuit breakers

Location is done and not by the circuit breaker

is changed. This embodiment may be for first

Pilot applications or demonstrations, or if it is ensured that there are no topological changes. The superordinate body is then usually a specialist who enters the definition manually. The determination can then only be changed manually by a specialist. For a practical, namely permanent, use in many low-voltage networks, this option is not suitable due to the high engineering effort.

The second possibility is that the determination of which circuit breakers are adjacent, by a parent circuit breaker takes place and a

Circuit breaker when allocating a new adjacent circuit breaker a wireless data connection to the new adjacent circuit breaker for the purpose of determining a

Line difference builds up. In this embodiment, a circuit breaker receives at least those topology changes that result in a change in its neighbors

communicated central system, for example from a so-called

Geographic Information System GIS. As an intermediate stage, an intelligent local network station (iONS) for the passing of the provide relevant neighbor changes. If the

Information transmission regarding the topology change is sufficiently fast, the circuit breaker can even respond to this change of / the neighbor and build the necessary data connection to the new neighbor.

To a possibly independent configuration of the

According to the invention, it is provided in a third embodiment that the definition of which circuit breakers are adjacent by the respective

Circuit breaker occurs and a circuit breaker when assigning a new adjacent circuit breaker for the purpose of determining a line differential a wireless

Data connection to the new adjacent circuit breaker builds.

So there is an independent neighbor detection by the individual circuit breaker. The circuit-breaker determines its communication-technical neighbors and coordinates this information with the one about its so-called "electrical" neighbors

Topology change, so if there is a new circuit breaker as a neighbor, a neighbor detection is performed (for example, the technical information about the new adjacent circuit breaker is determined) and the

appropriate data connection established accordingly. For the methods for neighbor detection are basically

different methods possible. The second and third characteristics offer the advantage of selectivity over a UMZ-R solution

Functionality of the line differential protection. In particular, the third expression leads in the direction

Automation of the low voltage network, because the

Line switches in the sense of "Plug & Play" can be inserted into the low-voltage network without manual engineering effort.

With the method according to the invention, with regard to the desired automation of low-voltage networks, an additional functionality can also be provided in that a message is sent to a higher-level regulatory authority of the low-voltage network even when a network section is overloaded. Thus, the I-problem mentioned above can be taken into account, so an overload detected (and this counteracted if necessary) before an error occurs.

The inventive method is usually

computer-aided. Accordingly, the subject invention can also be implemented as a computer program product comprising a program and directly into a memory of a circuit breaker of a

Low-voltage network is loadable, with program means to perform all the steps of the inventive method when the program is executed by the circuit breaker.

The invention also includes a low-voltage network with at least one circuit breaker according to the invention for

Disconnecting faulty network sections of the

Low voltage network of further network sections of the

Low-voltage network for carrying out the method according to the invention. The low voltage network is thereby

characterized in that the circuit breaker with a

adjacent circuit breaker for determining a

Line differential is in wireless data connection and a disconnecting device, which is designed such that the lying between the two circuit breakers

Mains section is disconnected from the low voltage network, when a predetermined, an error corresponding difference value of the currents flowing through the adjacent circuit breaker, is exceeded.

Brief description of the figures

To further explain the invention, reference is made in the following part of the description to the figure, from the further advantageous embodiments, details and

Developments of the invention can be seen. The figure shows a schematic representation of a meshed low-voltage network.

Embodiment of the invention

The figure shows a meshed low voltage network, e.g. a local area network, with three network stations 1,2,3. Each network station 1,2,3 is represented by a transformer, departing from the busbar 4 each three electrical lines. The electrical cables of the

Low-voltage network shown as solid lines, in contrast to the dashed lines shown

Data connections between the individual circuit breakers. The circuit breakers are shown as small circles, wherein the inventive method with reference to two

adjacent circuit breaker 5, 6, is explained.

The between the adjacent circuit breakers 5, 6

lying electrical line forms a network section, the by means of the circuit breaker 5, 6 from the rest

Low voltage network could be disconnected. This

Network section has an error 7. About the

between the circuit breakers 5, 6 existing

Data connection 8 are now continuously transmitted the current throughputs of the other circuit breaker and compared with their own power flow. If this results in a difference value that corresponds to a fault (earth fault or short circuit), the disconnecting devices switch both

Circuit breaker 5, 6 the intervening network section from the network.

The data connection between the circuit breakers must generally be robust to the current provision of a

To ensure line difference. The easiest way is to use standardized data connections.

For the third embodiment of the method according to the invention, it is also necessary that the

Circuit breaker recognize each other as neighbors and a circuit breaker assigns the respective neighbors to the outgoing network sections. This is it

necessary to establish a fast connection too

ensure peer-to-peer communication between the circuit breakers and / or multi-hopping.

Multihopping is the simultaneous transfer of data from multiple nodes or devices in a network to a specific node. The data connection should help to determine the line difference continuously with little effort (with low "base load"), but with topology changes a good availability

exhibit. At the range of the data connection are no high demands to make, it is enough a maximum Range of 1000 m or a line of sight connection.

The data connection or the units which make these available should be retrofitted to existing ones

Circuit breakers can be installed.

The data connection could be about the same as 802.11p

standardized extension of the WLAN standard and with the ETSI G5 standardized Geonetworking be realized. However, the frequencies used would not be in the frequency range of 5.9 GHz reserved for IST applications, but in the normal WLAN frequency range of 2.4 or 5.6 GHz according to 802.11abg. These extensions allow you to build a meshed wireless network without a dedicated master and with minimal base load (no beaconing). The communication can take place at any time without BSSID (the Basic Service Set Identification (BSSID) uniquely designates every Basic Service Set (BSS) of a WLAN): according to the 802.11p speech, ie "OCB" - "outside the context of a BSSID".

Reference sign list:

1 first network station

2 second network station;

3 third network station;

4 busbar

5 first circuit breaker

6 second circuit breaker

7 fault location

8 data connection between first and second

Circuit breaker 5, 6

Claims

claims

1. Method for separating faulty network sections

a low-voltage network of further network sections of the low-voltage network, characterized in that a plurality of network sections each by a

Circuit breaker (5, 6) are separated from each other, wherein adjacent power switch (5, 6) to each other

Determination of a line difference in wireless

Data connection (8) stand and that between them

Disconnect lying network section from the low voltage network, if a given, an error corresponding

Difference value of the currents passing through adjacent

Circuit breaker (5, 6) flow, is exceeded.

2. The method according to claim 1, characterized in that the determination of which circuit breaker (5, 6) are adjacent and for the purpose of determining a line difference with each other in wireless data connection (8), by a circuit breaker (5, 6) superordinate point takes place and is not changed by the circuit breaker.

3. The method according to claim 1, characterized in that the determination of which circuit breaker (5, 6) are adjacent, by a the circuit breakers (5, 6)

superordinate place takes place and a circuit breaker at Assignment of a new adjacent circuit breaker a wireless data connection (8) to the new adjacent

Circuit breaker for the purpose of determining a

Line difference builds up.

4. The method according to claim 3, characterized in that the higher-ranking point comprises a local network station.

5. The method according to claim 1, characterized in that the determination of which circuit breaker (5, 6) are adjacent, carried by the respective circuit breaker and a circuit breaker in association with a new

adjacent circuit breaker to establish a line differential, a wireless data connection (8) to the new adjacent circuit breaker.

6. The method according to any one of claims 1 to 5, characterized

characterized in that already at overload of a

Network section a message to a parent

Regulatory instance takes place.

A computer program product comprising a program and loadable directly into a memory of a circuit breaker (5, 6) of a low voltage network, comprising program means for carrying out all the steps of the method according to any one of claims 1 to 6 when the program of

Circuit breaker (5, 6) is executed.

8. Low-voltage network with at least one circuit breaker (5, 6) for disconnecting faulty network sections of the low-voltage network of further network sections of the low-voltage network for carrying out the method according to one of claims 1 to 7, characterized in that the power switch (5, 6) with an adjacent

Circuit breaker for determining a line difference in wireless data connection (8) is and a

Separating device which is designed so that the lying between the two circuit breakers (5, 6)

Network section is disconnected from the low voltage network, if a given, an error corresponding

Difference value of the currents passing through the neighboring ones

Circuit breaker flow, is exceeded.