DE2914900C2 - Method and device for fault direction detection in an electrical multi-phase network - Google Patents

Description

characterized,

f) that in the case of a two-pole short-circuit, the faulty condition of the invention is based on a method for misdirection detection according to the preamble of claim 1 and of a device for Implementation of such a method according to the preamble of claim 3.

With these generic terms, the invention refers to a state of the art, as it is in the CH-PS 4 22 129 or in DE-OS 23 33 112 is described. From CH-PS 4 22 129 is a method for fault direction detection known in electrical multi-phase networks, in which to avoid a dead zone 2-pole short circuit and to ensure a correct directional decision of the phase angle between Current and voltage in the measuring unit of a

phase voltage signal (Us') adhered, the supply relay in the sense of a current lag is increased together with the other faulty relay. The disadvantage here is that 2 selection logics required phase voltage signal (UY) are taken from the short circuit, namely one each for the distance and the direction decision is affected, also by this additional angle.

(λ) in the direction of its error-free phase position From DE-OS 23 33 112 is an error phase measuring

(Us) before the formation of this fault measurement voltage circuit for an electrical network protection device signal is rotated. known, in order to achieve an extensive Un

depending on the amplitudes of the measured voltages recorded as well as their harmonics a .Signal converter is provided, which is dependent on 2 measuring voltages, d. H. of output signals from a reference voltage transmitter and an error measuring voltage transmitter, supplies a time step signal, the amplitude of which depends on the phase shift of its two input signals and monitored in a downstream threshold value circuit for a limit value violation will. Activation circuits cause overcurrents or voltage drops or abnormal ones as a function of overcurrents Phase voltage ratios the activation of a selection circuit, the healthy and diseased network

(MZ) with an error direction detection phase for the formation of these 2 measurement voltages for the purpose of

Selects fault direction or fault distance determination. The selection circuit required here with reference voltage transmitter and error measuring voltage generators are comparatively expensive.

The invention as defined in claims 1 and 3 solves the problem of a method and a Specify device for faulty direction detection in an electrical multi-phase network, with simpler Averages also provide useful results in the near-fault range for multi-pole short circuits.

The additional phase angle shift introduced accordingly is at least one of those for the formation of the error measurement voltage used phase voltages has to

2. The method according to claim 1, characterized in that the additional angle (<x) is dimensioned to be at least equal to the total error angle of the voltage measuring device for obtaining the phase voltages.

3. Device for performing the method according to claim 1,

a) with a phase selection circuit (PA) triggered by an activation circuit (AR) in the event of a fault,

b) via a measured variable switching device ()

() g

circuit (FRD) is in control connection,

c) wherein the fault direction detection circuit has two control channels (1,2),

d) which are connected to the inputs of a difference generator (VD) ,

characterized.

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e) that the measured variable switching device (MZ) has inputs for the phase voltage signals (R, S, T, Φ), for the phase current signals (In, / _s , It) and for the linked phase current signals (Ir _s , Ist, Itr) , of which according to the

The result is that there is always a sufficient amplitude of this measurement voltage, even with phase voltages that are practically in-phase available and thus a perfect determination of the phase angle between the measured voltage and the measuring current is possible with respect to the changeover of the measuring voltage from a phase position in the phase out of phase is a reversal of the phase position, but this can be: close errors before and behind the measuring station not noticeable because the phase angle monitoring of the measuring voltage on the measuring current is related, which in turn when changing the fault system between forward and backward direction reverses its sign, while that of the measuring voltage remains unchanged

For the relevant state of the art, reference is also made to the AEG-Telefunken-Zeitschrift, Vol. 78, 1978, Issue 5, Pp. 177-182, referenced. There, the detection of the direction of the error is essentially based on limit value monitoring of the phase angle between the error measurement voltage and the error measurement current, assuming a direct use of the error measuring current as a reference indicator for the phase angle measurement unbalanced limit values of the voltage for leading and lagging measuring voltage are required are. Therefore, if necessary, an additional phase rotation of the measuring current for use as Reference pointer made.

In the case of a fault direction detection for two-pole Short circuits, the corresponding line-to-line voltage is to be used as the error measurement voltage. These Measurement voltage has very low amplitudes, especially in the case of near-range errors, and may not allow a flawless one Evaluation. In addition, the affected phase voltages in the Close-up error range approximately in phase, so that the difference pointer is not only in its size, but also is fraught with great uncertainty in its sense of direction, especially with regard to the inevitable Phase angle error of the two phase voltages (scatter of the transducers, etc.). This also becomes the Directional decision unsafe and unusable even in the near error range.

Further features and advantages of the invention will become apparent on the basis of the exemplary embodiments shown in the drawings explained. Herein shows

Fi g. 1 shows a vector diagram of measuring current and measuring voltages in the complex plane for a common fault direction detection,

F i g. 2 shows a phasor diagram of a three-phase system with the associated phase and measurement voltages for two-pole short circuit with additional phase angle shift of a measuring voltage according to the invention,

F i g. 3a and 3b each have a section from a phasor diagram according to the type of FIG. 2 for illustration different possibilities of additional phaser, angle shift of phase voltages and

4 shows the basic circuit diagram of a device for Error direction detection according to the invention.

In Fig. 1, the rotation of the fault measurement current Ik is shown in a modified phase position according to pointer / *, - 'for the purpose of fault direction detection. For the error measurement voltage, there are then two limit angles p? Arranged approximately symmetrically on either side of Ik ' , the exceeding of which corresponds to a change between the forward and backward error direction with respect to the measurement location. Error measurement voltages Ukl- \ or UK ₁ : 2 are indicated in the two-sided Crenzlage with respect to ///. The indicated shift from Ik to / jc 'has the advantage of balancing the limit angle monitoring, but in principle it is also possible to work with an unchanged Ik . An inversion of the tripping area, as it is often desired for reasons of circuit simplification, can be carried out by inversion of voltages and currents according to the border lines £ · | indicated by dashed lines and reach gi.

In Fig. 2 is the formation of an error measurement voltage

ίο Uk for two-pole faults between Us and i / r is indicated as the difference between the phase voltages Us' and Ut which are reduced in their amplitude and which are approximated in their phase position. The indicated relationships do not yet correspond to a proximity error in which the pointers i / s 'and Ut' approach each other much more closely and lead to a very low amplitude of Uk . According to the invention, the phase voltage LV is therefore, for example, converted into a modified position Ut "by rotating it through an additional angle λ .

In Fig. 3 shows the relationships with a closer approximation to reality for a two-pole near fault. The additional rotation with the angle λ from Ut to Ut " leads with sufficient dimensioning with certainty from the hatched uncertainty range S _T in the measurement of this phase voltage. Of course, the second phase voltage Us' is also subject to such an uncertainty range, With the indicated position of both pointers, this can lead to the mentioned falsifications of the directional decision .

As shown in FIG. 3a, the additional rotation of the phase voltage is connected to a certain rotation of the measurement voltage Uk ' as well, but this is a higher order error which is practically negligible. However, especially when monitoring the phase angle of the measurement voltage with respect to the non-rotated measurement current, it is advisable to perform the additional rotation on the phase voltage that is lagging behind in the phase sequence, because this results in a rotation of the measurement voltage in the sense of a symmetry, but in any case not an increased asymmetry, of the critical phase angle on both sides of Ik is connected (see Fig. 1).

In the exemplary embodiment according to FIG. 3b, both error measurement voltages t / 5 'and Ut' of a two-pole short circuit are provided with additional rotations in modified positions i / s "and Ut" . A somewhat greater effort is required for this, but a rotation of the measurement voltage Uk ″ is largely avoided.

The direction of the additional rotation is to be selected in each case so that the phase voltage affected by the fault from their error-related phase position in the direction of their error-free normal phase position within the

ω multiphase system is shifted. This arises clearly also from FIG. 2 and F i g. 3a and 3b.

In the circuit according to Fi g. 4 is a triggering device AR a phase selection circuit PA at _t; -worfen. whereby the phase-

b5 selection signals sk. Vs. s /, s. /, In a manner not shown for the measurement variable connection of a distance protection or the like (see the lines leading upwards), but in the present case also for the

Control of a measuring signal connection device MZ can be used. This is a conventional control circuit with binary input signals from the phase selection circuit and analog inputs for the phase connections R, S, T, 0SOWIe for the measuring currents Ir, Is, It, Irs, Ist, Itr and the corresponding ones to be switched through according to the various error cases Analog outputs A \ to -4j. This control circuit has a logic function which, for the sake of simplicity, is identified by a truth table entered in the circuit with the input and output variables already specified. In order to switch through the phase connections and measuring currents, this control circuit has the required analog switches in a customary manner that does not need to be explained in more detail and which are controlled in accordance with the logic functions shown in the truth table.

Two channels 1 and 2 for measuring voltages are connected to the outputs A 1 and A2 , which lead to a differential amplifier VD . In one of the channels, possibly also in both channels, as indicated by dashed lines, a phase rotation element PD is switched on for the introduction of the additional angle oc . The output of the differential amplifier VD and the output A3 assigned to the respective measuring current are each led via a rectangular signal shaper RF and, with the aid of a timer ZG and a simple locking AND gate Gu, enable the detection of an exceedance of the limit phase angle determined by the time interval of ZG q> _g . In the event of such an excess, a flip-flop FF is set and an error direction signal a _{r is} generated, which is assigned to a predetermined error direction. A reset input R to the flip-flop FF is provided for resetting the total error direction detection circuit FRD.

As the MZ truth table in the first three lines shows, the circuit is also suitable for fault direction detection in the case of single-phase faults. A phase connection is switched through to zero on each of the voltage channels, while a phase current is switched through in each case in the current measuring channel. In order to avoid a phase rotation in the case of a single-pole fault, the channel 1 expediently remains free of a phase-shifting element, which corresponds to an operating mode according to FIG. 3a. This avoids a stronger influence on the single-pole fault direction decision.

Ir, Is, h.

Irs, is, Itr

A], Ai, Ai

1.2

VD

PD

FF

RS

ZG

GU

Sr FRD

= Measuring currents

= Analog outputs

= Channels

= Differential amplifier

= Phasing element

= Flip-flop

= Square wave formers

= Timer

= Lock AND gate

= Error direction signal

= Error direction detection switch

tion

= Reset input

For this purpose 2 sheets of drawings

Designation list = Us ", Ut" Error measurement current Ik St. Phasing Ik ' Uk " Critical angle 8 = AR Measuring voltages UKgU U _Kg 2 PA Boundary lines gUg2 = sr, Ss, St, Sfi = Error measurement voltages Uk, Uk ' MZ Phase positions Us, Ut R.S.T. & Phase voltages Us ', Ut' Additional angle Locations Uncertainty area Measuring voltage Excitation device Phase selection circuit Phase selection signals Measuring signal switching device Phase connections

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Claims (1)

Patent claims: 1. Method for detection of faulty directions in an electrical multi-phase network, a) in which method phase voltage signals (Ur, Us, U ₇ ^ are derived from the phase voltages and phase current signals (IrJs, It) are derived from the phase currents, b) from these signals, in the event of a short circuit, an error measurement voltage signal (U _K , U _K ') assigned to the short circuit voltage and an error measurement current signal (Ik. / ^ assigned to the short circuit current) are formed, c) whereby in order to form the error measurement voltage signal (Uk, Uk) at least one of the phase voltage signals (Ut '), which are faulty due to a short circuit, is rotated by a predeterminable additional angle (λ) in the direction of the fault-free phase position (U _T ) of this fault-affected phase voltage, d) the phase difference between the error measurement voltage signal (Uk, Uk ') and the error measurement current signal (Ik, Ik ' ^ formed and e) when a first limit value (Ukc i.! Pc) is exceeded or a second limit value (Ukc2, φα) is undershot, an error direction signal ^ is generated which characterizes the error direction with respect to the measurement location, g) Phase selection circuit (PA) two phase voltage signals can be switched through individually to a first (Αή and a second output (A ₂ ) and a phase current signal or a concatenated phase current signal to a third output (Ax) , that the first output (A \) of the measured variable switching device (MZ) are connected to a first input and the second output (A2) via a phase rotation element (PD) to a second input of the differential generator (VD) and that the output of the Difference former and the third output (A ₃ ) of the measured variable switching device are connected to two inputs of the error direction detection circuit (FRD).