RU2455654C1 - Method for identification of damaged section and nature of damage within electric power grid of ramified topology - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: method is based on installation of a master device at the substation feeding the grids which devices accepts HF signals from slave devices located at the end of each line within the grid. The slave devices supply HF positive-sequence voltage to all the three phase conductors of the transmission line which conductors are phase-shifted relative to each other by 120 degrees. The master device accepts and records three-phase HF voltage received by the mater device from each slave device individually. During joint processing of all the three-phase HF signals recorded from all the slave devices one identifies the damaged grid section and the nature of damage. The method specificity consists in connection of the master device and the slave devices to a low voltage using for connection to the grid a measuring voltage transformer (secondary circuits) or the auxiliary power transformer (low-voltage side 0.4 kV).

EFFECT: possibility of damage identification; absence of necessity to install special devices for connection of HF equipment to a HV grid.

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Description

The invention relates to the relay protection of electrical systems and can be used to determine the damaged area and the type of damage in the power grid with a branched topology. The scope of this relay protection is medium-voltage overhead power transmission networks.

The known location-based method of WMD, which allows you to determine the distance to damage in a straight line (see international application Soraghan JJ Automatic fault location in cabling systems. Patent, IPN: WO 98/1370 (02.04.98); Shalyg G.M. Method for determining the distance to the place of damage to the power line and communication Patent No. 185405 (07.10.1966); patent RU 2269789 C1 (02.10.2006)). Continuous improvement of this method over several decades has allowed us to reach accuracy unattainable by other methods. The location method provides a large range of measured distances, low measurement error. But all this applies to unbranched cables, wires, etc.

In networks with a complex branched topology, there is a problem associated with the ambiguity of determining damage, the solution of which is impossible only on the basis of location-based pulsed sounding from one (master) device.

There is a method that monitors the network and uses reflectometry data to determine the presence of defects in wires and cables in networks with a branched topology (prototype of the invention, see patent RU 2319972 C1 (03.20.2008), Karpov A.V., Zakirov A.N. Method determining the presence of defects in wires and cables in network segments with a branched topology), and consists in the fact that the leading terminal equipment simultaneously performs location-based sensing and measurement of the carrier phase received from the slave terminal equipment, data for They are stored in the memory of a microcomputer, the measured phase value and the shape of the trace are compared with previous values, and if the phase or shape of the trace changes, the presence or absence of damage in the probed segment is determined.

A known method for determining the location of damage in networks with a branched topology (prototype of the invention, see patent RU 2386974 C1 (12/23/2008), Karpov A.V., Zakirov A.N.), adopted as a prototype based on network monitoring and data use scatterometry, measured by the master device in the network, characterized in that the master device pre-collects information about the integrity of the segments in the controlled section of the network by interrogating the slave devices (network scan), while the master device generates a scanning a marker (CM frame) with an empty information field for a slave nearby the network, which in turn preliminarily changes the contents of the information field of the CM frame with a code unique to this slave and passes it to the next slave in the link, which performs the same operations as the previous one slave device; the described process of transmitting an SM frame occurs up to the end in the slave link n or to the first damaged segment associated with a specific slave i; Further, the slave devices n or i transmit the SM frame with the information field that had formed by that moment back to the master device (reflection of the SM frame) by relaying through the same slave devices intermediate in the link, and the master receives the reflected SM frame and stores the corresponding information field in the micro memory A computer that determines the presence or absence of damage in network segments.

The disadvantage of these inventions is that a high-frequency information signal is transmitted over the network. The following properties of power lines are not taken into account:

- when transmitting high-frequency signals through one phase of a three-phase power line, the signals will be directed to the other wires of the power line (due to electromagnetic coupling between the wires of the power line). As a result, short circuit or break of one phase wire - will not lead to blocking the transmission of high-frequency signals through power lines. In fact - the above methods will not work in a real power line;

- both of the above methods do not distinguish the type of damage in the power line: single-phase earth fault, interphase fault, open-circuit of one phase, etc.

The objective of the invention is to determine the damaged area and the type of damage in the power grid with a branched topology.

The technical result is achieved by the fact that the master device performs a preliminary collection of information about the integrity of the segments in a controlled area of the network by interrogating the slave devices (network scan). In this case, the slave devices located at the network boundaries (at each end of the branched network line) generate a high-frequency direct sequence voltage U1: high-frequency voltages Ua, Ub, Uc are supplied simultaneously to all three phase wires A, B, C of the power line, and voltage data phase shifted relative to each other by 120 degrees. The master device located on the substation supplying this network receives and records the three-phase high-frequency voltage (records the voltages Ua, Ub, Uc) transmitted separately by each slave device. Joint processing of all three-phase high-frequency signals from all slaves allows you to uniquely determine:

1) damaged network segment,

2) type of damage (single-phase earth fault, interphase fault, open-circuit of one phase, etc.).

Consider the proposed method as an example of a simple network (Fig. 1, a single-line diagram of a three-phase network), which is powered by substation 1, and has several network sections: 2, 3, 4, 5, 6. A master device 7 is installed on the power substation 1, Slaves 8, 9, 10 are installed at each end of the lines. Slaves 8, 9, 10 generate a high-frequency direct sequence voltage U1: high-frequency voltages Ua, Ub, Uc are applied to all three phase wires A, B, C of the power line, and voltage data phase shifted relative to each other n 120 degrees. Slave devices 8, 9, 10 supply high-frequency voltage to the line in series (first 8, then 9, then 10), while they do not interfere with each other. The master device 7 receives and records the three-phase high-frequency voltage (voltages Ua, Ub, Uc) transmitted separately by each slave device and, based on the voltages Ua, Ub, Uc, determines the voltages of the zero sequence U0, the direct sequence U1 and the negative sequence U2.

In the absence of damage, the master device 7 will receive from all the slaves 8, 9, 10 the voltage of the direct sequence U1, the voltage of the zero sequence U0 and the negative sequence U2 will be zero. That is, a sign of a normal state (without damage) are the values:

Without damage: U1> 0, U0 = 0, U2 = 0.

If a damage occurs on the line in section 4, the relationships between the symmetrical components U0, U1, U2 received from the slave devices 8, 9, 10 will change. And depending on the path along which the high-frequency signal passes from the slave device to the master device 7, there will be different relations between the symmetric components of U0, U1, U2 are obtained. This allows you to determine on which part of the network (2, 3, 4, 5, 6) the damage occurred and determine the type of this damage.

So, if damage 11 is a single-phase fault to ground (OZZ), then the voltage of the zero sequence U0 will be different from zero, and the voltage of the negative sequence U2 will be zero:

OZZ: U1> 0, U0> 0, U2 = 0.

If damage 11 is a two-phase short circuit 2FZ (for example: a short circuit between phases A and B), or a break in one phase (for example: phase A), then all symmetrical components will become non-zero:

2FZ or Open A: U1> 0, U0> 0, U2> 0.

It is quite easy to distinguish a two-phase circuit from a break in one phase: if, for example, phase A breaks, the phase voltage Ua will be close to zero.

Detection of a damaged area is carried out by comparing signals from various slaves. When considering the signal path from the slave to the master, it is important whether there is damage on this path. It is easiest to understand the principle in the event of a break in one phase, for example phase A in section 4 (damage 11). Then the phase voltage Ua will be close to zero for the signals of the slaves 9 and 10, since for both slaves 9 and 10, the signal path to the master 7 includes section 4. At the same time, for the slave 8, the phase voltage Ua will be close to other phase voltages Ub and Uc value, because for the slave device 8, the signal path to the master device 7 does not include section 4. Thus, by comparing the signals from the slaves 8, 9 and 10, it is possible to determine the damaged section 4.

A feature of this method is the connection of the master and slave devices to low voltage, using a voltage transformer (secondary circuits) or an auxiliary power transformer (low side 0.4 kV) to connect to the network. This is possible, since the measuring voltage transformer and the auxiliary power transformer operate not only at an industrial frequency voltage of 50 Hz, but also at high-frequency audio signals (1-10) kHz. As a result, there is no need to install special devices for connecting high-frequency equipment to the high-voltage network.

Thus, the invention relates to the relay protection of electrical systems and allows you to determine the damaged area and the type of damage in the power grid with a branched topology. In addition, this method does not require the installation of special devices connecting to the power line.

Claims (1)

A method for determining the damaged area and the type of damage in a power network with a branched topology, based on monitoring the network by a master device located on the substation supply network that scans the network, preliminary collects information about the integrity of network segments by polling slave devices, characterized in that the slave devices located on the boundaries of the network at each end of the branched network line, high-frequency voltage of a direct sequence is supplied to all three phase water of the power line, phase-shifted relative to each other by 120 °, and the master device receives and records the three-phase high-frequency voltage received by the master from each slave device separately, while the joint processing of all recorded three-phase high-frequency signals from all slave devices determines network section and type of damage.