SU1121741A1 - Device for determining short-circuit hazard - Google Patents

Abstract

A DEVICE FOR DETERMINING A SHORT CIRCUIT HAZARD, containing a power dump unit, consisting of a series-connected measuring unit, a summing operational amplifier, and a threshold ttf, mane. element with a reacting element, characterized in that, in order to increase accuracy and speed, it is equipped with a direct voltage minimum sequence relay, a swing blocking element, memory elements, a maximum voltage drop signal selector unit and a controllable gain unit, and the output the undervoltage relay is connected to the first input of the corresponding memory element, to enable the inputs of each of which the output of the swing lock element is connected, the outputs of the memory elements, Connected to the inputs of the maximum voltage reduction unit, the output of which is connected to the input of the controllable gain unit, the output of which is connected to the input of the summing switch amplifier, and the control inputs of the controllable gain unit are intended to be connected to the equipment transmitting signals of the composition and power system mode.

Description

I1 The invention relates to electrical engineering, in particular, to automation devices of energy systems, in particular, to an automation device for determining the risk of a short circuit in order to preserve the stable operation of a power system. The stability of the power system during short circuits x depends on the power drop. To determine it, it is necessary to fix the power flows through the BceNi transmission lines, departing from the monitored node of the power system, and the initial power of the main cross section connections, in which there is a danger of stability disturbance, in order to achieve the necessary effects of the automation device. In connection with the absence of the possibility of fixing the total power flow across all power lines, the power release latching is performed according to the magnitude of the decrease in the voltage of the direct sequence at the power system node. A device for determining the risk of a short circuit in terms of the decrease in the voltage of a direct sequence, containing several minimum voltage relays of the direct sequence, a blocking from oscillations, which starts the minimum voltage relay for short circuits, is known. The signal passes through the coincidence circuit to the device output if the short circuit duration exceeds the specified L. Such a device allows determining a complete power shedding only with a constant circuit and the operating mode of the power system. The dependence of the transmitted power on the voltage value at the nodes of the power grid is complex and is determined by the number of operating power plants and power lines connected. Therefore, the use of a direct-sequence minimum-voltage relay with a constant setting of the triggering settings does not reflect a complete power shedding upon a change in the mode and pattern of operation of the power system, although it allows fixing the short circuit and its duration. The closest to the present invention is a device for determining the risk of a short circuit by fixing a power loss at fault with 11 sensitivity dependence on the power of the initial mode, containing a meter connected in series of the current value of the active power, the block of storing the signal of the original power, forming the power drop signal, forming together measuring unit summable operational amplifier, threshold element with reacting element zj. However, this device can determine the total power loss only in the presence of power flow meters on the outgoing lines at the installation site of the automation device and in the presence of a signal transmission body on the magnitude of the power of the main connections of the section in which there is a danger of stability disturbance. Since the telecast of signals about the power of all the main links of the cross section is practically absent, the known device does not provide the required accuracy of determining the power drop at short circuit in all operating modes of the power system. Due to the insufficient speed of existing telemetry devices, it is also necessary to ensure a short delay of the device for determining the risk of a short circuit. The aim of the invention is to improve accuracy and speed. The goal is achieved by the fact that the device dp for determining the risk of a short circuit, containing a power release organ consisting of a series-connected measuring unit, a summing operational amplifier, a threshold element with a reactive element, is equipped with a minimum-voltage relay of a direct sequence, a blocking element against oscillations , memory elements, a block of maximum voltage reduction and a controllable gain block, and the code of the minimum voltage relay with The first input of the corresponding memory element is connected to the permitting inputs of each of which is connected to the output of the blocking element against oscillations, the outputs of the memory elements are connected to the inputs of the extraction unit of the signal of maximum voltage reduction, the output of which is connected to the input of the controlled amplification unit, the output of which connected to the input of the summing operational amplifier, and the control inputs of the control gain unit are designed to be connected to the equipment transmitting signals about the composition and mode of the power system. Figure 1 shows the characteristic of the output signal of a real differentiation unit; 2 is a block diagram of a device for determining the risk of a short circuit; FIG. 3 is a block diagram of a signal block proportional to the maximum voltage drop of the direct sequence. Accuracy and speed in determining the total power shedding at short-circuit can be increased by introducing an analog signal into the power shedding unit 2 proportional to the maximum voltage reduction with a coefficient leading to power shedding in the cross section determined by the computer prior to the power system. In order to ensure high speed of the device proposed, the great reduction in the voltage of the direct sequence should be determined with a minimum delay. The output of the control of the real differentiation unit has the form shown in FIG. Reducing the time to reach the maximum S;) is possible by reducing the constant differentiation of the block bill. However, high accuracy is not achieved as the signal changes rapidly. For a more accurate signal distribution, proportional to the &U; | , and entering it into the power dump body, it is necessary to memorize the value of the analog signal} | Not enough time to trigger a power shedding device. An increase in the constant differentiation of the 4SB block reduces the change in the signal tl with time, which increases the accuracy of the device, but an increase in the signal rise time to u.lj max can lead to a forced shutdown of more generator power. Due to the fact that, when determining the duration of a short circuit with several undervoltage relays, the latter perform a quick conversion of the voltage drop of the direct follower 414. to output a logic signal, it is advisable to use for the sake of speed the data of the minimum-voltage relay of the direct sequence and the ability to instantly convert the logic signals at their output to an analog signal proportional to the largest decrease in voltage & u ,, .. defined by the expression 1 max nom min; where, c is the smallest of the settings that triggered the undervoltage relays. This makes it possible to reduce the time for determining the total power shedding. Thus, the essence of the invention is that the additional sequential connection of the minimum voltage of the direct sequence of memory elements to the relay output, the maximum voltage reduction unit and the controllable voltage gain unit, the output of which is connected to the input of the summing operational amplifier allows to provide a constant signal proportional to the decrease in the voltage during a short circuit by time Attenuated to trigger the power shedding organ, and preliminarily taking into account the network power and the number of operating generators using signals from the appropriate equipment to the control inputs of the voltage controlled gain unit, improves accuracy and speed when fixing the total power shedding in the power system short circuit The device contains a unit 1 measuring the current value of three-phase active power, a unit 2 for storing a signal proportional to the initial power, a unit 3 for selecting a signal proportional to a power dump, a measuring unit 4 summing the operational amplifier 5, a threshold element with reacting element 6, a block 7 for blanking the signal is proportional to the voltage of the direct sequence, the minimum voltage organs 8, the swing lock 9, the memory elements 10, the signal extraction unit 11 are proportional to. the maximum voltage reduction of the direct sequence, the unit 12 of the controlled voltage boost.

Unit 11 Тфг.З) consists of an OR-NOT 13 circuit, potentiometers 14 for setting reference voltage, proportional to the difference of nominal voltage and pickup voltage of a separate undervoltage relay, resistors 15 and 16 of the inputs and the feedback circuit of the amplifier, transistor switches 17 and amplifier 18.

The measuring unit 4 consists of a unit 1 for measuring the current value of three-phase active power, the output of which is connected in parallel with the unit 2 for storing a signal proportional to the initial power, and unit 3 for extracting a signal proportional to the power drop. The outputs of block 4 are connected in series with the summations of the operational amplifier 5 and the threshold element with the reacting element 6.

Parallel to block 4, a signal block 7 is successfully transmitted, proportional to the voltage of the direct sequence, a minimum voltage organ 8, memory elements 10, a signal 11 block proportional to the maximum reduction of the voltage of a direct sequence, controlled voltage gain block 12 . The series-connected blocks 7 and 8 form a direct-sequence undervoltage relay. In parallel with the minimum voltage unit 8, an interlock from the swings 9 is turned on. The output of the minimum voltage relay is connected to the first input of the corresponding memory element 10, and the output of the block 9 from the anti-swing device is connected to the enable input of each memory element 10.

The device works as follows.

At the moment of a short circuit due to the fact that the voltage across the direct sequence is abruptly reduced, the blocking unit 9 permits the passage of the signals from the minimum voltage devices 8 to the output of the corresponding memory elements 10 and to the inputs of the block 11.

Depending on the depth of landing 1 time ull | one, two, or all under voltage relays may operate. At the same time, at the corresponding input of the OR-NOT 13 circuit, the logical signal is O if the organ 8 connected to the input of the circuit OR-NOT 13 via the memory element 10 did not work, or the signal 1 if it worked. At the same time, at the input of the OR-NO 13 circuit, connected via element 10 to the output of the organ 8, which has the lowest response voltage and all the activated organs, there will be a signal O, which prohibits the transmission of logical signals about triggering to the output of the circuits 13, included in the circuit 8 with a greater setpoint of tripping on voltage D114. Consequently, in these chains, the keys 17 are open and shunt the corresponding input resistances 15 of the amplifier 18, only the key 17 at the output of the IPI-NO 13 circuit in the circuit: the booster body 8 with the lowest setpoint is closed with the signal O at its input, and the output of the amplifier 18 the corresponding potentiometer 14 is supplied with a voltage proportional to

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With standard analog signals it corresponds to (j ,, 10 V

Subsequently, the output voltage of the block 11 is supplied to the input of the controlled gain block 12, to the control inputs of which the computer receives a code on television channels corresponding to the value of the conversion coefficient of the analog signal. 11, j to the power drop in the cross section, in which there is a danger stability impairment.

The code arriving at the control inputs of unit 12 must simultaneously take into account the composition of the network, since the number of dynamic power lines and the magnitude of the dangerous power shedding, which may cause instability, change from the number of power lines turned on. Consequently, the inputs of the summing operational amplifier 5 receive not only a signal about power reset on the power line at the installation site of the automation device, but also a signal proportional to the total reset of power in all other section lines, which ensures greater accuracy of fixation of full power reset during short circuit71

Cania and high speed device.

The proposed device, by memorizing logical signals about the operation of the minimum-voltage relay in a straight-line sequence using memory elements 10, ensures that the signal at the output of block 11 is constant for a time sufficient for the power deceleration unit to appear and the signal at the output of element 6, and turn on the output of block 1717418 .

kovki from swinging on resolving. the input of the memory element 10 provides the input signal) g of the block 11 only for a short circuit time. five

Technical and economic efficiency is determined by the increase in the accuracy of the new equipment and the speed of the VIA, which provide a reduction in the switchable power of the generators to maintain stability during power drops during short circuits.

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Claims (1)

A DEVICE FOR DETERMINING A SHORT-CIRCUIT HAZARD, comprising a power reset unit, consisting of a series-connected measuring unit, a summing operational amplifier, a threshold element with a reacting element, characterized in that, in order to improve accuracy and speed, it is equipped with a direct sequence undervoltage relay ^ a blocking element against swings, memory elements, a signal isolation unit for maximum voltage reduction and a controlled gain unit, and the relay output the minimum voltage is connected to the first input of the corresponding memory element, to the allowing inputs of each of which is connected the output of the oscillation blocking element, the outputs of the memory elements are connected to the inputs of the maximum voltage reduction signal isolation block, the output of which is connected to the input of the controlled gain block, the output of which, connected to the input of the summing operational amplifier, and the control inputs of the controlled gain block are designed to be connected to equipment transmitting signals about the composition and power system mode. SU ..., 1121741>