SU1116489A1 - Detection member for protecting three-phase electric installation against asymmetric short circuit - Google Patents

Abstract

A mist BODY FOR PROTECTION AGAINST THREE-PHASE FAULT NESGOSHETRICHNOGO ELEKTROUSTANOV, KI comprising symmetrical components filter, -upravl emy generator sinusoidal voltage, the phase discriminator, a first delay line and an output adder, the three measuring inputs symmetrical component filter constituents are connected to each phase current sensors phases of electrical installation, and the output of the filter of symmetric components is connected to the first input of the output adder and the first input of the phase discriminator, the output of which Through a series-connected first integrator, it is connected to the input of a controlled sinusoidal voltage generator, characterized in that, in order to expand the use area by increasing the duration of the emergency component at the output of the selective organ, it additionally introduces a controlled voltage divider, comparator and the second integrator, the output of the controlled sinusoidal voltage controlled generator (/) is connected to the first input of the controlled divider voltage, to the second the input of which is connected to the output of the second integrator, the output of the controlled voltage divider is connected to the second input of the said phase discriminator and the second input of the output output adder, the first input of the comparator is connected to the output output of the filter of the symmetric components, the second input of the comparator is connected to the output of the controlled the voltage divider and the comparator output to the input of the second integrator.

Description

one

The invention relates to electrical engineering, in particular, to relay protection and automation of power systems.

In a series of relay protection devices, it is necessary to obtain an emergency component of an inverse or zero sequence, which must be distinguished from the background unbalance of the normal mode.

A device is known comprising a controlled oscillator of periodic oscillations, a phase discriminator and an integrator connected in cascade with it. At the output of the device, a periodic voltage (in particular, of rectangular form) is formed, which coincides in phase with the control voltage, and the value of the rectangular output voltage remains unchanged as the control voltage (1.

Circuits are known to distribute the emergency component of the reverse or zero sequence, which contain a delay line, which are used in remote blocking starting mechanisms of remote protection and where the almost instantaneous value of the emergency component is fixed for 8-12 ms, while for reliable determination of the phase of the emergency the zero-sequence current and voltage components need a time of at least 15-20 ms 2.

Considering that the time during which the output signal of the expressive organ is only a small part of the constant time of the delay line, the required duration of the output signal in the known device cannot be obtained.

The aim of the invention is to expand the scope of use by extending the duration of the emergency component at the output of the vigorous organ.

To achieve this goal, in the detection organ for protection against asymmetrical short-circuit of the three-way electrical installation, which contains a filter of symmetrical components, a controlled sinusoidal voltage generator, a phase discriminator, a delay line and an output adder, three measuring inputs Ultra symmetric S4892

Other components are connected in phases.

The current sensors in the phases of the electrical installation, and the output of the symmetric components filter are connected to the first input of the output adder and the first input of the phase discriminator, the output of which through a sequentially connected first integrator is connected to the input of a controlled gey ... sinusoidal voltage generator. a voltage divider, a comparator and a second integrator, the output of the said controlled sinusoidal voltage generator is connected to the first input of the controlled voltage divider, The second input of which is connected to the output of the second integrator, the output of the controlled voltage divider is connected to the second input of the said phase discriminator and the second input of the above output adder, the first input of the comparator is connected to the output output of the filter of the balanced components, the second input of the comparator is connected to the output of the control voltage divider, and the comparator output to the input of the second integrator.

The structural diagram of the distinguishing organ is shown in the drawing.

The conveying body contains a filter 1 of symmetrical components and a controlled generator of sinusoidal voltage 2, the output of the filter

1 symmetric components connected to the first input of the phase discriminator 3, cascaded with which the first integrator 4 is connected, the output of which is connected to the input of a controlled sinusoidal voltage generator 2. To the output of the filter

1Symmetric components are also connected to the first input of the output

5 adders 5, between the second input

whose output is controlled by a generator of sinusoidal voltages

2 includes a controlled voltage divider 6, the output of which is connected to the second input of the phase discriminator 3, and the inputs of comparator 5 are connected to both inputs of the comparator 7, the output of which through the second integrator 8 is connected to the control divider 5

voltage 6 ..

In normal operation, three-phase electrical installation at the output

 five,

filter 1 symmetrical components

there is an output voltage of the variable frequency, caused, for example, by the natural asymmetry of the load or the difference in resistance of the individual phases of the installation.

The controlled sinusoidal voltage generator 2 produces a sinusoidal voltage unaffectedly. The output of phase discriminator 3 has an output voltage, the sign of which depends on the sign of the angle of shift between the output voltage of the filter 1 of the symmetrical components and the output voltage of the controlled divider 6. Output voltage Phase discriminator 3 through the first delay line 4 controls the frequency of the generator 2, which ensures the coincidence of the phase voltage at the output of the filter symmetric components of the generator 2 and controlled divider 6.

At the output of the comparator 7, there is an output voltage, the sign of which is determined by the sign of the difference in absolute values of the input voltages of the adder 5. This output voltage through the second delay line 8 affects the transfer coefficient of the controlled divider 6, which ensures the equality of the input voltages of the adder 5. Since two equal and phase-matching sinusoidal voltages are applied to the direct and inverting input of the adder 5, its output voltage is zero.

Thus, the elements entering the device provide continuous alignment of the amplitude values of the voltages at the input of the adder and their coincidence in phase, and consequently, the absence of output voltage at a constant value of the components of the reverse (zero) sequence, both in absolute value and in absolute value. and by the angle, or by their slow change, when the time is constant 164894, ..

the above components are substantially longer than the time constant of the delay lines.

When an asymmetrical short-circuit of a three-phase electrical installation occurs, a voltage appears at the output of the filter 1 of symmetrical components, which represents the vector sum of the normal component and the component of the normal mode.

Due to the inertia of the delay lines at the time of the occurrence of damage, the voltage at their outputs corresponds to the normal mode and the voltage at the second input of the adder also corresponds to the component of the normal mode in magnitude and phase. The output voltage of the device is equal to the vector difference of the output voltage of the filter of the symmetric components and components of the normal mode and, therefore, the value of the emergency component.

5 While during the time of 5-10% of the constant time of the delay lines, the voltage at their outputs varies little the output voltage of the device almost completely corresponds to the alarm value of the symmetric components, and it is during this period that it is used for the operation of the measuring bodies of the relay protection.

When performing delay lines on operational amplifiers, a time constant of 5–10 s can be considered quite achievable, which ensures obtaining an emergency component of symmetric components for 0.2–0.5 s, i.e. significantly more than the known device.

Thus, when using the invention, it is possible to include zero-sequence or reverse-sequence power directives on the accident components, which expands the field of application of the device.

Claims (1)

IDENTIFICATION AUTHORITY FOR PROTECTION AGAINST ASYMMETRIC SHORT CIRCUIT OF A THREE-PHASE ELECTRICAL INSTALLATION -, KI, containing a filter of symmetrical components, a controlled generator of a sinusoidal voltage, a phase discriminator, a first delay line and an output adder, three measuring inputs of the filter of the symmetrical components of the sensor are electrically connected in phase to phase the output of the filter of symmetrical components is connected to the first input of the output adder and the first input of the phase discriminator, the output of which through An integrally switched on first integrator is connected to the input of a controlled sinusoidal voltage generator, characterized in that, in order to expand the scope of use by increasing the duration of the emergency component at the output of the detecting organ, a controlled voltage divider, a comparator and a second integrator are additionally introduced into it, the output the aforementioned controlled sinusoidal voltage generator is connected to the first input of a controlled voltage divider, to the second input of which the output of the second integrator is switched on, the output of the controlled voltage divider is connected to the second input of the mentioned phase discriminator and the second input of the said output adder, the first input of the comparator is connected to the mentioned output of the filter of symmetrical components, the second input of the comparator is connected to the output of the controlled voltage divider, and the output of the comparator - to the input of the second integrator. 1P6489 1 11-16489 2