SU1545287A1 - Device for differential arc protection of cells of factory-assembled switchgear - Google Patents

Abstract

The invention relates to electrical engineering and is intended for high-speed arc protection of cells of complete switchgears. The aim of the invention is to increase reliability and sensitivity. This is achieved by monitoring the state of photo sensors located in adjacent cells and connected in series and forming a bridge with resistors, to the output of which the comparison circuits are connected. Bandpass filters and second comparison circuits are also attached to the photosensors. The outputs of the comparison circuits are connected to the logical part of the device. If a short circuit occurs, accompanied by an arc inside the cell of the complete switchgear, the conductivity of the photosensors increases, which leads to the operation of the comparison circuits and the disconnection of the damaged cell. 1 hp f-ly, 2 ill.

Description

The invention relates to the field of electrical engineering and is intended for the relay protection of cells of a complete switchgear (KRU) and a complete switchgear of an outdoor installation (KRUN) from arc short circuits (SC) in them.

The purpose of the invention is to increase the reliability and sensitivity of protection against arc short circuits arising in a cell.

Fig. 1 shows the arrangement of photo sensors in separate cells (compartments) of a complete switchgear, which in this case consists of three cells; on

Fig. 2 illustrates the measuring and logical parts of a security device.

The device of differential arc protection of cells of switchgear 1 consists of photosensors 2-7, resistive dividers 8 and 9, comparators (threshold elements 10 and I, forming the first comparison circuits 12-14, having two outputs, filters (bandpass filters) 15-17 connected to the inputs of the second comparison circuits 18-20, the first, second and third logic circuits AND 21 - 23, the first delay element 24, the logic circuit OR 25, the second delay element 26

2

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Photo sensors are located inside the switchgear cells (KRUN), two in each cell and connected in series with the photosensors of adjacent cells. Circuits from series-connected photosensors are connected in parallel with each other and with resistors forming a voltage divider. Photo sensors and a resistive voltage divider form a bridge.

Comparison circuits 12-1A, consisting of comparators 10 and 11, have first and second outputs, the high level signal of which appears with a positive and negative input signal, respectively.

The protection device circuit includes filters that are made bandpass and tuned to the second harmonic component of the network frequency, which allows you to be rebuilt from interference signals. The luminous flux of an electric arc contains two main components: the constant component and the second harmonic. This makes it possible to use this informative feature, which is inherent practically only in the light flux of the arc, and to perform protection of a highly sensitive and reliable one.

In the absence of an arc, the short circuit formed by a resistive divider and photosensors is balanced and the signals at the inputs of the comparison circuits are close to ir / Li, and all the circuits 12-14 of the comparison are in an unworked state and the signal at their outputs is zero. The signals at the outputs of the filters 15–17 and of the comparison circuits 18–20, the AND 21–23, OR 25 logic circuits, delay elements 24 and 25 are also equal to zero.

Consider the operation of the device in different modes,

When a short circuit occurs, accompanied by an arc inside the switchgear cell, for example, in the middle cell (Fig. 01), the conductivity of sensors 4 and 5 increases, which leads to the appearance of a positive signal TJ. and a negative signal U;.,. This triggers the comparison circuits 12 and 13 and the output 0 on the second and first outputs, respectively, of high level signals, which causes the output signal at the output of the logic circuit 21 and OR 25 and turns off damaged cell and later shutter speed

time 0.1-0.3 s, disconnecting the input switch,

There is also a second channel that provides disconnection of a damaged cell without time delay, formed by a third AND circuit, the inputs of which receive signals from the outputs of the protected cell comparison circuit 13, second protected circuits 18 and 19 of the protected and adjacent cells controlling the level of the second harmonic component of the light This makes it possible to reliably shut off the damaged cell even when the photosensors of adjacent cells are illuminated, for example, when inspecting

The third channel, formed by logic circuit 22 22, allows you to turn off the damaged cell with the shortest possible time delay in this case. The output signals from the first output of the comparison circuit 13 and the second comparison circuit 19, i.e. in this case, it controls the relative level of the full signal of the protected and adjacent cells, as well as the absolute level of the second harmonic signal. This allows protection even when the photocell of the adjacent cell is out of operation or is removed from operation.

If an arc occurs in other cells, the protection works in the same way.

FULLY

Thus, protection allows, through differential comparison of signals, to reliably detect arcing: short circuit, increase sensitivity by controlling adjacent cells and controlling the presence of the second harmonic sotavluyu.

Claims (2)

Invention Formula but 1 o Device for differential arc protection of complete switchgear cells containing photosensors for installation in each cell, first comparison circuits AND logic, delay elements, voltage divider from a series of thermally connected resistors, in order to increase reliability and sensitivity , additionally introduced photo sensors, one for each cell, the first conclusions of the first group of photo51 Sensors located in different cells are connected to the first output of a voltage divider, the second output of which is connected to the second terminals of the second group of photo sensors located in the corresponding cells, the second terminal of each photo sensor is connected to the second output of the corresponding photo sensor of the adjacent cell and connected to the inputs the corresponding filter and the first comparison circuit, the second comparison circuit, whose inputs are connected to the filter outputs, the trip circuit of each protected cell formed by the first and second circuits , Third trehvhodo- howling AND circuit, first inputs of which are connected to the first output of the first comparing circuit protected cell, the second inputs of the second and third AND circuits are connected to the output of the second circuit Я76  -.the comparison of the protected cell, the third input of the third circuit AND is connected to the output of the second comparison circuit of the adjacent cell, the second input of the first circuit AND under the second output of the comparison circuit of the adjacent cell, the output of the second circuit AND, is connected to the input of the first delay element connected to the first input of an inputted OR element, the second and third inputs of which are connected respectively to the outputs of the first and third AND circuits, to the output of the OR element a second delay element is connected, the output of which is intended to be switched off in the circuit and an input switch, 2. The device according to claim. 1 and 2, is that the filter is made band-wise and tuned to the second harmonic component of the frequency of the protected network. Uh U; s ItL I Lkj m ro