SU1205081A1 - Apparatus for determining impedance up to shortcircuit point in three-phase mains with isolated neutral - Google Patents

Abstract

The invention relates to a measurement technique and can be used to determine the location of a short circuit in a distribution network. The purpose of the invention is to increase the reliability of the determination of resistance to the point of short circuit. The device contains sensors of 1 line operation mode according to the number of monitored lines. Each sensor contains an inverter AC 2 to a DC voltage, a meter maximum 3 and minimum 8 (L m J S CL 00

Description

4 currents and a pulse shaper 5, a voltage conversion unit 6, a current conversion unit 7, a signal detection unit 8, arriving from blocks 6 and 7, a time delay element 9, a control unit 10 containing elements OR 11-13, a memory block 14, an AND element 15, a memory element 16, an OR-NOT element 17, a block 19 for calculating the resistance to the short circuit point and a block 20 for reading. The introduction of the sensor 1 in the invention relates to measurement technology and can be used to determine the location of a short circuit in the distribution network.

The purpose of the invention is to increase the reliability of the determination of the resistance to the place of the short lock of the device.

The drawing shows a schematic diagram of the proposed device.

The device contains n sensors 1 line operating mode (according to the number of monitored lines), - intended for measuring and converting current into the outgoing line into discrete signals, each of which contains converter 2 of the alternating current line into a constant voltage, the output of which is connected to the inputs meters of maximum 3 and minimum 4 currents designed to convert continuous signals to discrete, shaper 5 pulses, generating single pulses when the monitored line is turned on and off and whose input is connected to the output current of the minimum current 4, the voltage conversion unit 6 and the input current conversion unit 7 in the section of the busbar system, respectively measuring the reactive component of the emergency mode voltage and the input current, convert them to constant voltage, block 8 registration, intended for short-term storage of signals arriving at its first and second

05081

The operation of the line, the elements OR 11-13, the element 15, the element OR 17, the memory element 16 and the formation of new connections between the elements of the device prevent failures in the operation of the device and false fixation of information due to short-term load changes, self-starting motors while maintaining a high sensitivity of the device to short circuits m. 1 Cp. f-ly. 1 il.

0

5 0 5 Q

inputs from blocks 6 and 7, block 9 time outlays, intended for ot-. the settings from the aperiodic component of the short circuit current, the output of which is connected to the third input of the registration unit 8, the control unit 10 containing logic elements OR 11-13, designed for the logical addition of signals arriving at their inputs, n inputs of the element 11 11 are connected to the first the outputs n sensors 1 operating mode piny, n inputs of the element RSHI 12 connected to the second outputs n sensors 1 mode of operation of the line, n inputs of the element OR 13 connected to the third outputs n sensors 1 mode of operation of the line, the output element And And 11 is connected to the fourth input of the registration unit 8 and the input of the block 9 time delay, and the output of the OR element 13 is connected to the fifth input of the registration unit 8 and the second input of the memory element 14 intended to store the maximum current meter 3, the first input of the element 14 the memory is connected to the output of the logic element OR 11, the logic element AND 15, intended for the logical multiplication of the triggered signals of the maximum current meter 3 and the disconnection of the line, the first input of which is connected to the forward output of the element 14 m ti, and the second - to the output of the OR gate 12, element 16 is a memory for storing a signal intended disconnecting the line after actuation overcurrent meter 3, a first input

which is connected to the output of an AND 15 logic element, and the second to the output of an ILK 13 logic element, an OR-NOT 17 logical element intended to form a control signal for returning the device circuit to its initial state, the first input of which is connected to output of the logical element OR 11, wto | ) OW input - to the inverse output of

memory 14, and the third input to the output of the memory element 16, the signal delay element 18, designed to delay the return signal of the circuit by the arc quench when the line is disconnected, the input of which is connected to the output of the logical element OR NOT 17, and the output with the second inputs of the memory elements 14 and 16, as well as with the fifth input of the registration unit 8, the calculating unit 19, designed to determine the resistance value to the short circuit point, the input of which is connected to the output of the register 8 unit, is read to 20 before ly Hrane audio information on the magnitude of resistance to a short circuit, the first input of which is connected to the output unit 19 calculate, as a second - to the output of the OR gate 13 and the output signal of delay element 18.

The use in the circuit of the device of sensors 1 of the operating mode of the lines allows to control the parameters of the mode of all departing connections, as a result of which the device receives more complete information about the monitored object.

The circuit of the device control unit 10 (containing the OR elements 11-13, the memory elements 14 and 16, the AND element 15, the OR-NOT element 17, the signal delay element 18 and the communication between them) is designed so that the device controls only certain sequence of events, and this in the presence of sufficient information. From the information coming from the sensors of the mode of operation of the line, increases the accuracy of the device readings.

The device works as follows.

In the normal operating mode, there are no signals at the outputs of sensors 1 of the operating mode of the lines. At the output of conversion unit 6, the voltage signal is proportional to

the reactive voltage component of the busbar section, and at the output of the current conversion unit 7, the input current to the busbar section is proportional to the input current. Block 8 registration controls and remembers the amount of current 1pr normal mode. There are no signals at all outputs of logic elements and memory elements of control unit 10 with the exception of the inverse output of memory element 14, which supplies the second input of the OR-NOT 17 logic element with a signal that prevents its operation.

When a short circuit occurs on one of the lines on the first output of sensor 1 of the operating mode of this line, as a result of the operation of the maximum current meter 3, a signal appears through the logic element OR 11 to the fourth input of the registration unit, thereby giving a command to detect the current the previous mode (If-o), which does not have time to change its value during the signal transit time. In addition, this signal starts the time block 9, which after a predetermined period of time, for example, 0.1 s, outputs to the third input of the recording unit 8 a signal for detecting the current 1 and the reactive component of the emergency mode CDr p. The signal from the output of the logical element OR 11 also changes the state of the memory element 14 and blocks the operation of the OR-NOT 17 logic element. The registration unit 8 after storing and Iq provides information to the input of the calculation unit 19, in which the calculation reactive resistance to the point of short circuit by the formula

.. and, p

I.-i

,

whereupon information about the value of x is transmitted to the input of read unit 20.

Subsequently, the short circuit is turned off by the relay protection. In this case, the maximum current meter 3 triggers to return, and then the minimum current meter 4 and a single pulse appear at the first output of the pulse shaper 5, which, through the logical element OR 12, the logical element AND 15

and memory element 16 transmits a control action to the third input of an OR-NOT 17 logic element, which removes the signal from its output resulting from the return

meter 3 maximum current. Since in this case the delay time of the signal in the delay element 18 is longer than the signal duration at the output of the logical element ORI17, the output of the signal delay element 18 does not pass this signal and the device can continuously store information about the reactance value for a short time. Whose closure, which is proportional to the length of the line to the point of short circuit, since the specific reactance of the distribution networks is assumed to be 0.4 ohms / km, this allows you to get a direct reading of the distance -No to the place of short circuit. .

In case of unsuccessful automatic reclosing of the line, the fixing process is repeated. In the case of a successful AR, i.e. the disappearance of the short circuit, the minimum current meter 4 returns to its original position, and at the second output of the pulse shaper 5, a single pulse appears, which through the logic element OR 13 transmits a control action to the return of the circuit to its initial state, during which the memory is erased 1e and Uq in the recording unit 8, the resistance value to the short circuit point in the reading unit 20 and the memory elements 14 and 16.

If a short-term increase in the current in the line is not accompanied by its disconnection, then after the meter 3 returns the maximum current, there are no signals at the inputs of the OR-NOT 17 logic element, and a signal appears at its output, which with some delay returns the circuit to the initial state.

In the proposed device, fixation and long-term storage of information on the magnitude of the reactive resistance to the short-circuit location occurs only in the event of a short circuit on the line and its disconnection by means of a line monitor. This allows you to eliminate failures in the operation of the device and false fixation of information due to short-term load changes, self-starting of engines, disconnection of the line by operating personnel, while maintaining a high sensitivity of the device to short circuits m.

Since the maximum current meter 3 controls the current in the line and not at the input of the device, its setpoint can be chosen equal to the setpoint of the maximum current protection of the line, providing protection of the entire length. line in case of short circuit.

Thus, the use of the proposed device allows to increase the reliability of fixing resistance to a short circuit location, the labor productivity of operating personnel in the process of searching for damaged elements in the distribution network, reducing undersupply of electricity and national-economic damage from consumers.

Claims (2)

1. A device for resistance to a short circuit in a three-phase network with insulated neutral, containing a time delay block, a recording block, a computing block, a read block, are blocks of current transducers and voltages that are connected to the first and second inputs of the check block, output The time block is connected to the third input of the registration block, the output of the registration block is connected to the input of the calculation block, the output of which is connected to the first input of the readout block, characterized in that, in order to increase nor the reliability of the determination of the resistance to the short circuit location, n sensors of the line operating mode, the first second and third logic elements OR, the first and second memory elements, the AND element, the OR OR NOT element, the signal delay element, n inputs of the first SHSh element connected to the first outputs n line operation mode sensors, p. inputs of the second element OR connected to the second outputs n line operation mode sensors, d) inputs of the third element OR connected to the third outputs n line mode operation sensors, output first wow 7 the OR element is connected to the input of the time delay element, the first input of the first memory element, the first input of the OR element and the fourth input of the registration unit, the output of the second element OR is connected to the second input of the AND element, the output of the third element OR is connected to the second the input of the first memory element, the second input of the second memory element, the fifth input of the registration unit, the second input of the reading unit, the output of the time delay element is connected to the third input of the registration unit, the first output of the first memory element is connected to v The second input of the first memory element is connected to the first input of the AND element, the output of the AND element is connected to the first input of the second memory element, the output of which is connected to the third input of the IPI-NE element, the output of the OR- NOT connected to the input of the delay element of the signal whose output is connected to the fifth input of the recording unit. 2050818 The second outputs of the line mode operation sensors | are connected to the second inputs of the OR element, the third outputs h of the line operation mode sensors are connected to the third inputs of the third element, and the inputs of the line operation sensor are connected to the terminals for connection to the control object. 2. The device according to claim 1, 10 and 10, each of the sensors of the line operating mode contains a line current transducer, meters of maximum and minimum line currents, a pulse generator 15, and the line current transducer rotor is connected to the input of the line operating mode sensor , the output of which is connected to the inputs of the meter maximum and minimum currents 20 lines, the output of the minimum current line meter is connected to the input of the pulse generator, the first output of which is connected to the second output of the line operating mode sensor, the second 25, the output of which is connected to the third output of the line operation mode sensor.