RU2792285C1 - Method of protection of power line from magnetizing current surges at power transformer - Google Patents

Abstract

FIELD: electric power industry.

SUBSTANCE: according to the invention, the protection uses a module that blocks the protection half-sets when a power transformer magnetizing current surge is detected and ensures their selectivity when the measuring current transformers are saturated. The module includes three identical blocks for detecting magnetizing surge currents in phase currents.

EFFECT: ensuring the selectivity of high-frequency protection during surges of the magnetizing current of power transformers in the network.

1 cl, 1 dwg

Description

The invention relates to the electric power industry, in particular to relay protection and automation (RPA) of power lines (TL) in the event of a magnetizing current inrush (BTN) of a power transformer in the network. Solves the problem of non-selective operation of high-frequency (HF) differential-phase protection (DFZ) or directional HF protection (HFZ) with absolute selectivity of power lines in the mode of switching on the power transformer at branch substations of the protected line or outside it.

According to [1], high-speed protection with absolute selectivity is installed on high-voltage and ultra-high voltage power lines with two-sided power supply. The use of DFZ or NVChZ for these purposes turns out to be problematic due to the possible non-selective operation of the protection in the BTN modes. The situation becomes more complicated when a device based on an electromechanical or microelectronic element base is used as the second, third or subsequent half-set of line protection with absolute selectivity, in which there are no BTN detection modules. In practice, the BTN in line protection is determined by the magnitude of the second harmonic in the inrush signal [2], and in the differential protection of the transformer, the shape of the inrush current curve is also controlled [3]. To identify the CTN in the power transmission line, only the information parameter by the magnitude of the second harmonic is applicable.

The closest to the claimed technical solution is the method described in [3], where, in order to eliminate the non-selective action of protection during BT, it is proposed to use a special module that, by the value of the second harmonic current or based on the ratio of the second harmonic current, for example, the zero sequence current, to the first harmonic current harmonics of the same sequence are detected by the BTN and temporarily blocks the protection action for shutdown. This method is chosen as a prototype of the invention. Its disadvantage lies in the fact that such a module, installed on the protection half-set, blocks only its half-set DPF (NVCHZ) and can operate non-selectively when the measuring current transformers (ITT) or intermediate current transformers (PTT) in the protection device itself are saturated. In the absence of such a module in the protection device at other ends of the line or its insufficient sensitivity, non-selective operation of semi-sets of other ends of the line, for example, made on electromechanical or microelectronic element bases, is possible. In addition, the second harmonic detection module can fail in case of line faults, accompanied by saturation of the ITT or PTT of the protection half-set, blocking its action to turn off the line fault from its end.

The purpose of the invention is to ensure the selective operation of high-frequency protection with absolute selectivity at BTN on power transformers of the network and at saturation of measuring or intermediate current transformers. This goal is achieved by blocking all semi-sets of line protection when detecting a BTN, and the BTN detection module itself is made three-channel with blocks for phase-by-phase detection of BTN in each phase and with control of the current in the phase, a blocking signal selection block by a majority body, a block for detecting the type of saturation depending on the type of connection of the secondary windings of the power transformer and a block for detecting current saturation in all phases in case of symmetrical three-phase faults, which unblocks the output signal of the module for ensuring selectivity in case of BTN.

The implementation of the method is illustrated in Fig. 1 is a block diagram of the operation logic of a protection half-set installed at one of the ends of the power transmission line, which is put into operation when a command is generated to start the RF transceiver. The block diagram of FIG. 1 contains the following blocks and elements:

уставка которого адаптивно формируется по значениям предшествующего режима, а выход РТ через элемент времени с выдержкой на срабатывание Т1 поступает на первый вход элемента памяти (ЭП), собранного на логических элементах «ИЛИ» D1 и «И» D2, выход которого является первым выходом A1 (B1, С1) блока 1 (2, 3); выход ФОС 1-й гармоники совместно с выходом ФОС 2-й гармоники поступают на 2-й ИО блока 1 (2, 3), который по отношению величин модуля тока 2-й гармоники к модулю тока 1-й гармоники

превышающему значение уставки, определяет наличие БТН в сети, а выход этого ИО, поступая на второй вход логического элемента «И» D2 ЭП, инициирует срабатывание и является вторым выходом А2 (В2, С2) блока 1 (2, 3); кроме того, выход ФОС 1-й гармоники является третьим выходом A3 (В3, С3) блока 1 (2, 3);- identical blocks 1, 2 and 3 for detecting BTN, respectively, in the currents of phases A, B and C, each of which consists of filters of orthogonal components (OPC) of the 1st and 2nd harmonics; the output of the FOS of the 1st harmonic is supplied to two measuring elements (MO), the first of which is the maximum current relay (RT)

the setting of which is adaptively formed according to the values of the previous mode, and the output of the RT through a time element with a response delay T1 is fed to the first input of the memory element (EM) assembled on the logical elements "OR" D1 and "AND" D2, the output of which is the first output A1 (B1, C1) block 1 (2, 3); the output of the FOS of the 1st harmonic, together with the output of the FOS of the 2nd harmonic, is fed to the 2nd IO of block 1 (2, 3), which, in relation to the values of the current module of the 2nd harmonic to the current module of the 1st harmonic

exceeding the setting value, determines the presence of the BTN in the network, and the output of this IO, going to the second input of the logic element "AND" D2 of the EA, initiates operation and is the second output A2 (B2, C2) of block 1 (2, 3); in addition, the output of the FOS of the 1st harmonic is the third output of A3 (B3, C3) block 1 (2, 3);

- block 4 blocking the high-frequency channel with a continuous high-frequency signal when detecting a BTN in at least two phases, consisting of a majority body assembled on the logic elements "AND" D3, D4 and D5 and the element "OR" D6, the output of which is fed to the first input of the logical element "AND" D7, the other inputs of which receive the signal "Start HF DFZ" ("Start HF LFZ") from the protection module DFZ (NVCHZ), the output of block 5 and the deblocking signal from the output of block 6 to the inverse input of the element " AND »D7, and its output is the output of the module and goes to the transceiver to block the RF channel with a continuous RF signal when a BTN is detected in the network;

и состоящий из логического элемента «И» D8 и программируемой накладки HI; на входы элемента «И» D8 поступают вторые выходы А2, В2, С2 соответственно с блоков 1, 2, 3, а его выход через программируемую накладку H1, оперативно включенного в положение «0-1», поступает на вход логического элемента «И» D7 блока 4. При соединении вторичных обмоток силового трансформатора в «звезду» в схеме

на вход логического элемента «И» D7 блока 4 с программируемой накладки HI, оперативно включенного в положение «0-2», поступает сигнал логической "1";- block 5, which detects the BTN in all three phases when connecting the secondary windings of the power transformer into a "triangle" in the circuit

and consisting of a logical element "AND" D8 and a programmable overlay HI; the inputs of the "AND" element D8 receive the second outputs A2, B2, C2, respectively, from blocks 1, 2, 3, and its output through the programmable overlay H1, operationally switched on to the "0-1" position, is fed to the input of the logic element "AND" D7 block 4. When connecting the secondary windings of the power transformer into a "star" in the circuit

to the input of the logic element "AND" D7 unit 4 with a programmable overlay HI, operationally included in the position "0-2", receives a logical signal "1";

где ν=A, В, С, различают БТН и насыщение во всех трех фазах при КЗ; на входы этих трех ИО поступают третьи выходы A3, ВЗ и СЗ блоков 1, 2 и 3 соответственно, а их выходы, объединенные по схеме «И» на логическом элементе D9, деблокируют посредством инверсного входа элемента «И» D7 блока 4 пуск ВЧ-сигнала для блокировки полукомплектов защит при БТН.- block 6, which by comparing the values of currents in phases A, B, and C, either a symmetrical load mode, or a three-phase short circuit without saturation or with saturation in all phases and consisting of three similar UTs, which, in relation to the levels of the current modules of the phases located in given range, for example,

where ν=A, B, C, distinguish between BTN and saturation in all three phases during short circuit; the third outputs A3, VZ and SZ of blocks 1, 2 and 3, respectively, are fed to the inputs of these three IOs, and their outputs, combined according to the “AND” circuit on the logic element D9, are released by means of the inverse input of the element “AND” D7 of block 4, the start of the RF- signal for blocking of protection half-sets at BTH.

The method is carried out as follows.

Если величина тока с учетом коэффициента отстройки, равного K_отс=1.2÷1.5, превышает модуль этого же тока, взятого за 1 или 2 периода ранее, то происходит срабатывание РТ и подготовка к срабатыванию ЭП. При этом происходит запоминание значения модуля предшествующего тока

на время до 0.1÷0.5 сек.The module constantly monitors three phases of the network and, based on the results of the operation of the FOS of the 1st harmonic, determines current surges in the line by means of the maximum RT

If the current value, taking into account the detuning factor equal to K _ots =1.2÷1.5, exceeds the module of the same current, taken 1 or 2 periods earlier, then the RT is triggered and the EA is prepared for triggering. In this case, the value of the module of the previous current is stored

for up to 0.1÷0.5 sec.

действие выхода максимального РТ задерживается на элементе времени Т1 с уставкой на срабатывание до 50 мс. Появление сигнала на выходе ЭП может быть только лишь при условии срабатывания ИО

т.е. при выявлении в фазном токе составляющих 2-й гармоники, которые появляются в сигналах тока либо при БТН в сети, либо при глубоком насыщении ИТТ или ПТТ; выход ИО

поступает на вход элемента «И» D2 ЭП, а его выход является первым выходом A1 (B1, С1) блока 1 (2, 3). Таким образом, на выходах A1, В1 и С1 блоков 1, 2 и 3 соответственно и, как следствие, на выходе всего модуля будет активный сигнал только лишь при появлении в цепях тока устройства составляющих второй гармоники, превышающих уставку срабатывания ИО, реагирующего на отношение уровней модуля тока 2-й гармоники к модулю тока 1-й гармоники.This time should be sufficient for the end of the transient process in the FOS of the 1st and 2nd harmonics and reliable operation of the EUT, which reacts to the ratio of the levels of the current module of the 2nd harmonic to the current module of the 1st harmonic. For detuning from the response time and return of the specified IO at the moment of transition from one mode to another, for example, occurring during load switching or in the event of a short circuit in the network, when due to the transient process in the FOS, non-selective operation of the IO is possible

the action of the maximum PT output is delayed by the time element T1 with a trip setting of up to 50 ms. The appearance of a signal at the output of the EA can be only if the IO is triggered

those. when the components of the 2nd harmonic are detected in the phase current, which appear in the current signals either during the BTN in the network, or during deep saturation of the ITT or PTT; IO output

enters the input of the element "AND" D2 EP, and its output is the first output A1 (B1, C1) block 1 (2, 3). Thus, at the outputs A1, B1 and C1 of blocks 1, 2 and 3, respectively, and, as a result, at the output of the entire module there will be an active signal only when the components of the second harmonic appear in the current circuits of the device, exceeding the setting of the operation of the EUT, responsive to the ratio of levels 2nd harmonic current module to 1st harmonic current module.

накладка H1 должна быть оперативно переведена в положение «0-1». При возникновении несимметричного КЗ в линии, сопровождающегося насыщением измерительных трансформаторов тока, и условии установки программируемой накладки HI в положение «0-1» срабатывания модуля не произойдет, т.к. для этого должно наблюдаться насыщение во всех трех фазах тока с появлением в них составляющих 2-й гармоники. При симметричных КЗ с насыщением ИТТ во всех фазах срабатывания модуля также не будет, т.к. в отличие от насыщения при КЗ в трех фазах при БТН ток в одной фазе будет иметь периодический характер и будет значительно меньше по величине относительно величин токов в двух других фазах. Поэтому в данном режиме даже в случае идентификации 2-й гармоники во всех фазах и, как следствие, появления в сигналах А2, В2 и С2 блоков 1, 2 и 3 соответственно логических единиц на входе элемента D8 блока 5, сопровождающегося его срабатыванием и поступлением логической единицы на вход элемента D7 блока 4, срабатывания блока 4 и всего модуля в целом не произойдет, т.к. одновременно с этим действием при симметричном КЗ срабатывают все три ИО блока 6, и от элемента «И» D9 этого блока поступит сигнал на инверсный вход элемента «И» D7 блока 4, блокирующий передачу сплошного ВЧ-сигнала в ВЧ-канал.Available in the network of switched-on power transformers with the connection of the windings according to the "star / delta" scheme

pad H1 must be promptly moved to position "0-1". If an asymmetric short circuit occurs in the line, accompanied by saturation of the measuring current transformers, and if the programmable HI overlay is set to the “0-1” position, the module will not operate, because for this, saturation should be observed in all three phases of the current with the appearance of the components of the 2nd harmonic in them. In case of symmetrical short circuits with saturation of the ICT, there will also be no operation of the module in all phases, since in contrast to saturation during a short circuit in three phases, with a BTN, the current in one phase will have a periodic character and will be much smaller in magnitude relative to the currents in the other two phases. Therefore, in this mode, even in the case of identifying the 2nd harmonic in all phases and, as a result, the appearance of logical units in the signals A2, B2 and C2 of blocks 1, 2 and 3, respectively, at the input of element D8 of block 5, accompanied by its operation and the arrival of a logical units to the input of element D7 of block 4, block 4 and the entire module as a whole will not operate, because Simultaneously with this action, with a symmetrical short circuit, all three IOs of block 6 are triggered, and from the “AND” element D9 of this block, a signal will be sent to the inverse input of the “AND” element D7 of block 4, blocking the transmission of a continuous RF signal to the RF channel.

БТН может наблюдаться только в двух фазах, поэтому на выходе элемента «И» D8 блока 5 будет логический «0». Однако оперативный перевод накладки HI в положение «0-2», соответствующий соединению обмоток силового трансформатора по схеме «звезда/звезда»

обеспечит при БТН надежную блокировку всех полукомплектов защиты.If there are power transformers in the network diagram with the connection of the windings according to the "star / star" scheme

BTN can be observed only in two phases, so the output of the element "AND" D8 block 5 will be logical "0". However, the prompt transfer of the HI overlay to the "0-2" position, corresponding to the connection of the power transformer windings according to the "star / star" scheme

will ensure reliable blocking of all protection semi-sets with BTH.

Thus, according to the principle of its operation, the proposed method makes it possible to ensure the selectivity of the line protection with absolute selectivity with RF channels when the current transformers are saturated and to detune from the magnetizing current surges of power transformers in the network.

Information sources

1. Rules for the installation of electrical installations, 7th ed., Approved. Order of the Ministry of Energy of Russia dated July 8, 2002 No. 204.

2. Fedoseev A.M., Fedoseev M.A. Relay protection of electric power systems: Proc. for universities. - M.: Energoatomizdat, 1992.

3. Dmitrenko A.M. Differential protection of transformers and autotransformers. - Electricity, 1975, N 2, p. 1 - 9.3.

4. Terminal for differential-phase protection of the 110-220 kV line of the "TOR 300 DFZ 51 x" type. Manual. Description of protection functions AIPB.656122.011-013 RE2.

Claims (1)

A method for protecting a power transmission line in the event of a magnetizing current surge of a power transformer, characterized in that, in order to ensure selectivity in detecting a magnetizing current surge, blocking of the action of a protection semi-set is used, characterized in that, in order to ensure protection selectivity in the modes of magnetizing current surge and saturation of measuring current transformers in protection a module was introduced that blocks all half-sets of line protection when a magnetizing current surge is detected and selectively disconnects the line when the measuring current transformers are saturated, including three identical blocks for detecting magnetizing current surge in phase currents, each of which includes a filter of the orthogonal components of the first harmonic, the filter outputs are fed to two measuring element of the blocks, the first of which is the maximum current relay, the setting of which is adaptively formed according to the values of the previous mode, and the output of the maximum current relay through a time element with a delay of cp batting is supplied to the first input of the block memory element, the output of which is the first output of the blocks, the filter of the orthogonal components of the second harmonic, the output of which, together with the output of the filter of the orthogonal components of the first harmonic, is fed to the second measuring element of the blocks, which, in relation to the level of the current module of the second harmonic to the current module of the first harmonic determines the presence of a magnetizing current surge in the network, and its output is connected to the second input of the block memory element and is the second output of the blocks, the first outputs of the blocks are connected to the first inputs of the majority element of the output block of the module, which, by means of a continuous RF signal, when a magnetizing current surge is detected blocks all protection half-sets with its output signal in at least two phases, the second input of the module output block receives an enabling signal when the protection half-set with absolute selectivity is triggered, the third input of the module output block receives a signal from the detection block magnetization inrush current in phases depending on the type of connection of the windings of the power transformer, the inputs of which receive the second outputs of the inrush detection blocks in each of the phases, and the fourth input of the output block of the module receives a deblocking signal from the block, which detects by comparing the values of currents in the phases of the line or load mode, or three-phase damage without saturation or with saturation in all phases, consisting of three similar measuring elements, combined according to the “AND” scheme, the inputs of which receive the third outputs of the surge detection blocks in each of the phases, and the output of the output block of the module is blocking line protection half sets signal.

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