DE2717681A1 - METHOD AND DEVICE FOR DETERMINING A MINIMUM OF THE ANGULAR IMPEDANCE AND A MINIMUM OF THE REACTANCE BY MEASUREMENT TO CREATE A DISTANCE PROTECTION FOR A LINE FOR TRANSPORTING ELECTRICAL ENERGY - Google Patents

Description

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Addition to P 25 51 872.1

i'iU.-UiLn JJ CüNTRÖLÜ UT D'li ^ UIPülf-Iüirj? (I.C.E.) » 41, rue Crozatier, F-75ü12 Paris (France)

"Procedure and Vorricntun ^ for the detection of a minimum the angular impedance and a minimum of the reactance uurch lie ^ sun ^ to create distance protection for a line for the transport of electrical energy "

709884/0658

The invention relates to a method and an apparatus for detecting a minimum of the angular impedance and a minimum of the reactance by measurement to create a distance protection for a line to. Transport of electrical energy.

All systems that are currently used for measurements on an electrical protective circuit and in particular for impedance and reactance measurement with the aim of creating distance protection as equipment for lines in high-voltage networks are used, are affected by the aperiodic component and the harmonics, which the input quantities, d. H. Carry the voltages and especially the current intensities with you in the event of a fault in the high-voltage lines.

As for the aperiodic component, im is used generally a device that causes a more or less long time delay (sometimes up to 0.2 seconds), to await the return of the symmetrical wave with the aim of making a correct measurement.

According to the present addition to the measuring method according to the main patent (DT-OS 2 351 872) the symmetrical wave is restored almost instantly and consequently the above time constant is switched off, the presence of which affects the response speed of the distance protection, which is the most important requirement for maintaining stability of the network in the event of a fault, because the target response time is shorter or equal to kO ma.

According to the invention, this is achieved in that each input variable (current intensity and voltage) has an active filter associated with an operational or functional

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amplifier is combined. This filter which is a band pass filter is, enables in the same way the blocking of the harmonic harmonics of the fundamental frequency, which in the The voltage and current to be treated occur and consequently the accuracy of the impedance or reactance measurement affect.

The drawing shows an example of the additional invention for impedance and reactance measurement according to de « llauptpatent illustrated.

Fig. 1 shows according to the present additional invention

Device completed by filters for measuring the angular impedance according to FIG. 2 of the main patent;

FIG. 2 shows the device for reactance measurement completed according to the additional invention by filters according to FIG. K of the main patent;

Fig. 3 shows an embodiment of one according to the invention usable bandpass filter of known type; and

FIG. K is a characteristic curve which, in order to illustrate the effect of the filter on the different frequencies in the ordinate direction, shows the amplitude component passed by the filter for the individual frequencies plotted in the abscissa direction.

FIG. 1 shows the angular impedance measurement according to FIG. 2 of the main patent, according to which the current I and the voltage U feed the primary windings of the transformers T. and T. The resistor R. connected between the terminals of the secondary winding of the transformer T. supplies a current strength of one bar proportional controllable voltage RI, and this voltage is via resistors R. and R_ the inputs one each

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Operational amplifier 11 or _o \ 2 supplied, which at the same time receive the voltage U, which is fed to you via the resistors R. or R ^ from the secondary part of the transformer T, which feeds _{the resistor R 1n.} This voltage tapped off by the resistor R ₁ is then filtered by means of a filter P _{1 in} accordance with the present additional invention. The amplifier forms the vector sum from U and RI and delivers a voltage V a - (U + RI) at the output, while the amplifier 12 forms the difference -Ü + RI and delivers this value at the output,

in series The capacitor C. and the resistor R-, which are / are connected between the terminals of the secondary circuit of the transformer T, supply a current i which is phase-shifted by an angle -P and which, after passing through a filter F, one of the two inputs Phase comparator 13, ^ k is supplied, the other inputs of which are connected to the output of one of the operational amplifiers 11, 12.

The reactance measurement can also be carried out as described in the main patent with reference to FIG. K , but using the filters according to the present additional invention in the manner illustrated in the present FIG. 2. The phase comparators 23 and 2k compare the phase shift between:

on the one hand, a variable proportional to the current intensity I, the image of which is tapped off at the resistor R, however is filtered by means of the filter F-; and

on the other hand, a quantity which is either the vector sum or the vector difference of the _{voltage U obtained at the terminals of the resistor R 1n} but filtered by the filter F. and a voltage zl proportional to I, the phase angle of which γ? is true ^be ₂ ~ R ^- of the phase shift circuit C. ₁ The operational amplifiers 21 and 22 form the sum or difference of U and zl, and the resistances

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—6—

K to R ₁ Q play a role analogous to the resistors R _{1 to K 0} according to FIG. 1.

Vie explained in the main patent, the quadrangular characteristic is obtained by grouping the + circuits according to Figo 2 and k of the main patent (Fig. 1 and 2 of the present application), which is achieved with high accuracy thanks to the action of the filters F to Pl,

For example, FIG. 3 shows the diagram of a band-pass filter of known construction which can be used as filters F. to F. This scheme of the bandpass filter with increased overvoltage coefficient has a first stage, which is mounted as a follow-up circuit and gives the whole circuit a high input impedance and consists of an operational amplifier 1 in series with a resistor R, while the second stage has an operational amplifier 2, whose Passband can be set by connecting the resistors R ₂₁ and R " _{2 in series} , which is connected between the two inputs of the filter. The filter is completed by the capacitors C ₂ and C_ and the resistors 2R in the switching arrangement shown.

Fig. K shows the characteristic of the transmitted amplitude component plotted in the ordinate direction as a function of the frequencies plotted in the abscissa direction, and as can be seen, the filter ensures strong attenuation on both sides of the central frequency of 50 Hz and thus holds back the aperiodic component and the upper harmonics.

both

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Claims (1)

Claim Method and device for detecting a minimum of the angular impedance and a minimum of the reactance by measurement to create a distance protection for a line for the transport of electrical energy, in which the measurement takes place according to a four-sided impedance characteristic (characteristic square), starting for each side of the characteristic square From an input current and an input voltage, two vector quantities can be formed, one of which with the help of of an operational amplifier is obtained, and the phases of the two quantities are compared in a phase comparator which, depending on the position of the point characteristic of the impedance in relation to the side of the square, has two states supplies, according to patent (UT-OS 2 351 H72), characterized in that in the circuits for forming the two quantities, the phases of which are compared, two Bandpass filters can be switched on in order to reduce the measurement Interference of aperiodic components and harmonic oscillations of the input voltage and the input current to withdraw without introducing a time constant. 709884/0658