SU1698926A1 - Device for dc network protection - Google Patents

Abstract

The invention relates to electrical engineering, in particular, to relay protection of a direct current network. The purpose of the invention is to increase the reliability of operation by detuning from load currents. The goal is achieved by those. What is simultaneously taken into account is the integration time with the current increment due to the supply through a resistor 5 connected to the inverting input of the operational amplifier of the integrator 3, a predetermined voltage. This improves the detuning from the increment of load currents that have a short current rise time, for example, when passing through an air gap. 2 Il.

Description

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The invention relates to electrical engineering, to protection devices of direct current networks, and can be used to protect said networks from short circuit currents, in particular, traction networks.

A protection device is known that comprises an integrator, a first and a second comparator, a current derivative sensor, the output of the current derivative sensor is connected to the inputs of the first comparator and an integrator, the integrator output is connected to the input of the second comparator. This device determines the current increment during its rise. The latter is defined as the time taken by the derivative of the current of the threshold level of the first comparator.

A disadvantage of the known device is the neglect of the features of current buildup, in particular, the magnitude of the current rise time itself, i.e. the time of operation of the first comparator, which makes it difficult to tune out from the load mode with a rapid increase in current.

A current protection device is known, which contains a sensor of the derivative of the current, the output of which is connected to the inputs of the trigger and integrator based on an operational amplifier with an inverting input The output of the integrator is connected to the input of the comparator, the output of the trigger is connected to the control input of the integrator. The triggering organ is a comparator with a signal termination delay block, which allows the harmonic components to be tuned from the current derivative sensor signal.

The drawback of the device is also the absence of a detuning from the load mode with a large magnitude of the current increment with a rapid increase in the current.

The aim of the invention is to improve reliability in operation by detuning from load currents.

FIG. 1 shows a device for protection; in fig. 2 - timing diagrams explaining the operation of the device in the remote short-circuit mode. and loads.

Device for protection of direct current network, contains sensor 1, derivative of current, trigger 2, integrator 3, comparator 4, resistor 5 connected between inverting input of integrator 4 by voltage source 6 Output of derivative 1 of current derivative is connected to inputs of starting organ 2 and integrator 3. The output of the starting organ 2 is connected to the control input of the integrator 3. The output of the integrator 3 is connected to the input of the comparator 4, the output of the comparator 4 is the output of the device, the starting organ 2 can

is a comparator with a relatively low trigger threshold, which makes it possible to determine almost all the rise time of the current. Source 6 voltage

has the same polarity as the sensor of the current derivative 1 when the current increases.

The device works as follows.

0B in the mode of a remote short-circuit voltage, which is characterized by a continuous increase in current, which is explained by the maximum inductance of the network, the change in current is represented by curve 7. The value of the derivative

5, the current (curve 8) becomes less than the threshold element 9 of resetting the starting state of the starting organ 2 after some time. This time the presence of the signal of the starting organ 2 is represented by curve 10. Curve

0 11 shows the addition of the integrator output signal, produced as a result of the introduction of an additional resistor. The output signal of the integrator 3 is represented by curve 12. Curve 13 shows the signal of integrator 3 in the absence of an additional resistor 5. At the end of the current increment, the selected value of integrator 3 (curve 12) reaches the setting value of comparator 4, shown by segment 14, and the device gives a trip signal the switch.

In load mode, the running time of the starting organ 2, represented by curve 9 on the right, is shorter, as well as the additive in the output signal of integrator 3, and it does not reach the setting of comparator 4 (segment 14), the device does not work.

The adjustment of the value of the additive to the output signal can be made either by changing the value of the resistor 5, or by the value of the predetermined voltage of source 6. The value of the required additive can be determined based on the ratio of the magnitudes of the current increments at

5 к.з. and the load and their current rise times. So. at equal current increments k.z. and load the additive from the duration of the rise of the current should provide the required margin in excess of the setpoint

0 comparator 4.

The use of the device allows to reduce the number of false trips of protection, to increase the reliability of the supply of electricity.

Claims (1)

5 claims A device for protection of a direct current network containing a sensor of a derivative of a current, the output of which is connected to the input of the triggering organ and to the inverting input of the integrator, to the control input of which the output of the triggering organ is connected, the output of the integrator is connected to the input of the comparator characterized in that In addition to the load current detuning, a series-connected voltage source and a resistor are additionally introduced. the second output of the latter is connected to the in The goal is to increase the reliability of the operation of the 5th rotary integrator input. 6 ten // 12. /four 13 Cut / # .z. FIG. 2 ten -14 12  13 Mode // ship