SU1317537A1 - Device for phase-to-phase short-circuit protection of different output electric power lines - Google Patents

Abstract

The invention relates to the field of electrical engineering and is intended to ensure the protection of electrical distribution networks against earth faults. The purpose of the invention is to simplify the device and improve reliability by disabling the second line in case of unsuccessful work of the executive body of the first line. When a double closure occurs

Description

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the second threshold organs of damaged lines are triggered to the ground, and at the same time the capacitor 13 starts charging. The setpoints for the operation of the first threshold organs are made stepwise - increasing, and the threshold organ with the minimum setpoint is triggered first. If the threshold setpoint of one of the damaged lines has the minimum setting, then a logical element of this line produces a pulse signal. As a result, the multivibrator 30 starts up, the key 15 closes and a signal is issued to actuate the actuator. When the switch 15 is closed in parallel with the capacitor 13, a resistor 14 is turned on. The voltage across the capacitor decreases to a level that is less than the minimum setting of the first threshold organs. When the actuator actuates the first damaged line, a double circuit with this

one

The invention relates to electrical engineering, in particular to devices for protection against double earth faults in a distribution electrical network with low capacitive currents.

The aim of the invention is to simplify the device and increase the reliability of work by disabling the second line in case of unsuccessful work of the executive of the first line organ.

FIG. 1 is a functional diagram of a device for protection against earth faults; FIG. 2- time diagram of the operation of the device nodes.

Sensors 1 - 4 zero-sequence current in which, for example, can be used transformer current transducers with windings connected according to the scheme of a zero-sequence current filter, installed on the pass-through. insulators of switchgear cabinets, through diodes 5-8 and limiting resistors 9-12 are connected to capacitor 13,

7537.

line is eliminated. The protection returns to its original state. If the executive body of the first line fails to work at the output of the element OR 29, the signal level is zero. After returning the standby multivibrator to the initial state and unlocking the switch 15, the capacitor 13 will start charging again. As soon as the voltage on the capacitor 13 exceeds the threshold of the first THRESHOLD of the second damaged line, similar elements of this line, the waiting multivibrator 30, key 15 will work. The advantage of this device is a simpler design of the lines with double ground connections in advance the selected shutdown sequence, as well as the possibility of shutting down the second damaged line if the executive body of the selected line fails. 2 Il.

parallel to which a controlled load is connected with a resistor 14 and a switch 15, as well as the inputs of the first threshold organs 16, 17 of the monitored lines 18, 19. The connection circuit to the capacitor of the first threshold organs of the lines 20, 21 is similar. The inputs of the second threshold organs 22, 23 lines 18, 19 through the diodes 24, 25 are connected respectively to sensors 1, 2. The circuit for connecting the second threshold organs of lines 20, 21 to sensors 3, 4 is the same. (The connection diagram of the threshold organs of lines 20, 21 is not shown in Fig. 1).

Diodes 5–8, as well as diodes — connected between the second threshold organs — the lines and the sensors 1–4, serve to rectify the alternating

output voltage and isolation of threshold organizations (elimination of their mutual influence). The outputs of the threshold bodies 16, 22 line 18 are connected to the log and the EC element. And 26, and the output element And is associated with a single (inclusive) trigger input 27. To the code of the tritter under

31

the keys of the executive organizer 28. The trigger 27 output is also connected via the ELI 29 logic element to the waiting multivibrator 30, controlling the state of the key 15. The zero input (switching off), the trigger 27 via the NOT 31 logic element is connected to the output of the threshold organ 22, Connection diagram the outputs of the threshold bodies 17, 23 of the element And 32, the trigger 33, the executive body 34, the logical element HE 35 line 19 and similar bodies of lines 20, 21. is similar to that described.

In the absence of ground faults, the output voltage of sensors 1–4 is practically zero and the threshold organs of lines 19–21 are in the state where the output signals of these organs are zero. The triggers are in a state in which signals are not sent to the executive units and the OR gate.

In the case of a single-phase ground fault, the threshold organs of the lines do not work, because their settings are greater than the maximum average value of the output voltages of zero-sequence current sensors 1–4. The waiting multivibrator in both cases is in the state in which the key 15 is open.

When a double ground fault occurs in the network, the output voltage of zero-sequence current sensors installed on damaged lines rises sharply. In this case, the second threshold organs of the damaged lines are triggered, and at the same time the capacitor 13 starts charging. The settings of the first threshold organs are different. With stepwise increasing adjustment, the threshold organ with the minimum setpoint is triggered first. If the threshold organ of one of the damaged lines has a minimum setpoint, the AND gate generates a pulse signal. The trigger of this line goes into another state, as a result of which the waiting multivibrator 30 is started, the switch 15 is closed, and the actuator triggers a signal. When the key 15 is closed in parallel with the capacitor 13, the resistor 14 is turned on whose resistance is chosen so that at maximum 74

the voltage at the output of the current sensors of the zero sequence of damaged lines, the voltage on the capacitor 13 is reduced to a level less than

 the minimum setting of the first threshold organs. In this case, the first threshold organ of the second damaged line does not fail. When the executive body of the first damaged line is triggered, the double circuit with this line is disconnected is eliminated, the threshold organs of the damaged lines return to their original state

element 31, a pulse signal appears, in connection with which the trigger of this line returns to its original state. After a predetermined time, it returns to its original state.

waiting, multivibrator 30, opens the switch 15 of the controlled load.

FIG. 2 depicts graphs of output voltages of functional organs of lines 18, 19, and general organs of the device. The numbers to the right of the graphs correspond to the numbers of the organs related to lines 18, 19 and to the general organs. The capacitor 13 is charged to a voltage equal to the voltage

settings of threshold authority 16 (Y 16). In case of unsuccessful work of the executive authority of the first line of the state of the second threshold authority and the trigger of this line does not change,

at the output of the element OR 29, the signal level will be zero. After the standby multivibrator returns to the initial state and the switch 15 is opened, the capacitor 13 will

Va will start charging. As soon as the voltage on the capacitor 13 exceeds the threshold of operation of the first threshold organ of the second damaged line, similar elements of this line, the waiting multivibrator, the key 15, will operate in the described sequence.

If the first threshold organ of the intact line has the minimum setpoint, the executive organ of this line will not work, since the second threshold organ will be in the initial state.

Since it is possible to disable the pre-selected line with double ground loops, it is necessary to rank the monitored lines according to some feature. For example, you can turn off when

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double closures are primarily lines with less responsible consumers. Then the minimum threshold should be the first threshold organ of the lowest rank, and the thresholds of the first threshold organs of the other lines should increase as the significance of the line increases.

Claims (1)

Thus, in the proposed device, it is simpler to protect the lines with double ground loops with a preselected shutdown sequence for any combination of damaged lines, and it is also possible to disable the second damaged line in case of unsuccessful operation of the selected line executive. Invention Formula A device for protection against short-circuits between the phases of different outgoing power lines, containing a zero-sequence current sensor, two threshold elements, AND and NOT logic elements, a trigger and an actuator on each line, the input of the second threshold element connected to the zero-sequence current sensor; first Ss ± i ge i GB 27 Ov ± Editor N.Slobod nickname O (pueZ Compiled by R. Vaskova TehredM.Hodanich Proofreader L. Patay Order 2429/49 Circulation 618 VNIIPI USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5 Manufacturing and printing company, Uzhgorod, st. Project, 4 75376 and the second threshold organs are connected with two inputs of the logical element AND, the output of the element AND is connected to the single input of the trigger, zero The trigger input is NOT connected to the output of the second threshold organ via a logic element, and the trigger output is connected to the executive branch, characterized in that 0 in order to simplify the device and increase reliability by disconnecting the second line in case of unsuccessful work of the executive body of the first line, the input of the first threshold 5 organ of each line is connected to a newly introduced capacitor connected through newly introduced limiting resistors and diodes with current sensors zero sequence All controllable lines are parallel to the capacitor and a controlled load is connected in the form of a series-connected resistor and a key, the control input of the switch is connected to the output of the newly introduced standby multivibrator, and the input of the multivibrator is connected to the outputs via the newly introduced logical element OR triggers each line. -t -f -t -tSubscription