SU1184045A1 - Device for automatic tuning of compensation current - Google Patents

Description

The invention relates to power engineering and is intended "for systems of automatic compensation of capacitive currents in high-voltage electrical networks of three-phase voltage 5 in the single-phase short circuit to earth mode, accompanied by an intermittent arc.

The purpose of the invention is to improve the device speed and accuracy of setting the compensation current.

FIG. 1 shows a block diagram of a device for automatically setting a compensation current; in fig. 2 - schematic diagram of the phase-15 frequency filter; in fig. 3 - phase-frequency characteristic of its phase-frequency filter; Fig.4 block diagram of the phase comparison unit. 20'

where is the characteristic resistance '

proportional to the quality factor of the circuit <3, calculated according to the expression

B

Consequently, the generalized contour detuning is

and phase angle:

agst ₈ Ω

The measuring winding 1 of the extinguishing reactor 2, included in the three-phase network neutral, is connected via input transformer 3 to the inputs of phase-frequency filter 4 and one 25 of the inputs of phase matching unit 5, the second input of which is connected to the output of phase-frequency filter. The input of the phase-sensitive amplifier 6 is connected to the output of the phase comparison unit, and the output is connected to the input of the executive org at 7 arc-suppressing reactors.

The phase-frequency filter (Fig. 3) is a series-connected capacitance C _{y, the} inductance b and the resistance K.

The operation of the device is based on measuring the phase angle between voltages. 0, and ϋ ₂ at the input and output of the phase-frequency filter. Options

filter selected so that your own> ______ 45

thirty

35

40

loop frequency

equals

circular network frequency.

When the input sig frequency changes, the resonance in the circuit is considered and the generalized detuning of the circuit

calculated by the formula

G = γ- ⁼

50

where x _to - reactance circuit.

Loop resistance

The phase characteristic of the proposed filter (Fig. 3) in the region of small detunings is close to a straight line and its slope is determined by the quality factor of the circuit: the higher the quality, the greater the phase slope has. If Δω> 0, then the phase angle tends to + Ϋ / 2 if To) <0, then к - 1Г / 2. Measurement of the phase angle cp between the voltages and, and C ₂ at the input and output of the phase-pass filter is performed in the phase comparison unit, where the pre-sinusoidal signals are converted in Shaper 8 and 9 into rectangular pulses using operational integral amplifiers as null-bodies, and then on scheme 10 matches. Such a construction of the phase comparison unit minimizes the error due to changes in the amplitude of the input voltage and _o , which varies exponentially. Rectangular pulses of duration proportional to the phase difference (p between voltage P ₍ nd and ₂ ) are fed to a phase-sensitive amplifier, which at the output generates a voltage proportional to the magnitude and sign of the phase angle ίρ. This signal goes to the executive element of the extinguishing reactor. The inductance of the reactor is changed to as long as the output of the phase-sensitive amplifier voltage is equal to zero.

one

ω С

ω ^}

Thus, in the proposed device, the sensitivity, and therefore

Actually, speed and accuracy depend only on the quality factor of the serial circuit of the phase-frequency filter and. There is no influence of the amplitude change. The input voltage in the mode of moving single-phase short circuit to earth.

The required Q-factor of the phase-pass filter can be easily achieved by using one of its numerous implementations using the active KS circuits as inductance.

The application of the proposed device allows you to use only

1184045

four

phase characteristics, which simplifies the circuit for automatic compensation and control of earth fault current. The sensitivity of the device can

5 to regulate in a wide range the changes in the quality factor of the phase-frequency filter, using for this purpose various methods of implementing high-quality inductances. The device does not respond to amplitude changes in the input quantities, which increases its noise immunity. In addition, it can be used with various types of arc extinguishing reactor.

Φί / 2.4

.

Claims (1)

DEVICE FOR AUTOMATIC ADJUSTMENT CURRENT COMPENSATION in the mode of a moving single-phase earth fault, containing an input transformer connected to the measuring winding of an extinguishing reactor, an actuator connected to the starting of an extinguishing reactor, characterized by the fact that, in order to improve its speed and accuracy, it is equipped with a phase-frequency filter, Phase comparison unit and Phase-sensitive amplifier, the input of the phase-frequency filter connected to the input transformer, the first input of the phase comparison unit is connected to the input, and the second input - to the output of the ph a frequency-frequency filter, a phase-sensitive amplifier is connected to the output of the phase comparison unit, the output of which is connected to the input of the actuator. > '1184045