SU534824A1 - Apparatus for selecting a faulty phase in a multi-phase AC mains - Google Patents

Description

In the selection device is damaged. phases in a multiphase ac electric network, containing phase value sensors connected to threshold blocks, were additionally connected sequentially phase-by-phase blocks for selecting emergency components of phase values (currents or voltages) and blocks for forming integral values of emergency components moreover, the outputs of the NIN units are connected to phase value sensors, and the outputs of the formation units are connected to the threshold units through the comparison unit in phase. The A-variance component of the current. The voltage i) is the sum of the instantaneous values of the indicated magnitudes taken at the moments of rotation shifted relative to each other by half the period of the washed frequency. In normal network modes of operation, the voltages at the outputs of the emergency components allocation unit are small and are determined by circuit errors, and for short circuits they are equal to phase values minus the currents (voltage) in the load mode. When calculating voltages and currents of a short distance, they are studied by their emergency components after the corresponding emf is entered. to the place of damage, provided that all other sources of voltage are shorted. The drawing shows a block diagram of a device for selecting a faulty phase in a multi-phase AC network. The device comprises a sensor 1 of phase values of voltages or currents, a block 2 for the allocation of emergency components for a voltage of scientific research institutes or currents; units 3 forming and coupling of integral values of modules of emergency components of voltages or currents, comparison unit 4, threshold 5 blocks Sensors 1 are measuring jibie transformers, sufficient accuracy of which must be ensured in the entire range of currents (circuits), BGyush- 2 are made with the aid of a transformer and a delay line or with the help of digital storage devices, and blocks 3 are rectifiers with smoothing filters or digital integrators. Block 4 is made using known tnyh circuits isolating the largest current (voltage NAM) - maksiselektooov. , Yorog blocks o have a delay time for actuation, which is sufficient for the shapes in blocks 3 of the required integral inputs & 1 st current, or voltage - .. The device works as follows. In normal network operation modes, the instantaneous values of electrical quantities supplied from sensors 1 to the inputs of blocks 2 are repeated every period of industrial frequency. Since the voltage at the output of the transformer transformer of block 2 is proportional to the current value of current (voltage, and the voltage at the output of the delay line of block 2 is proportional to the current (voltage) of the preceding half period, the voltage at the output of block 2 close to zero and the rest of the circuit does not come into action. With short circuits, the instantaneous values of the electrical quantities at the outputs of sensors 1 change abruptly. The voltage at the output of the matching transformer of unit 2 is also It does not change quickly, and the voltage at the output of the delay line of block 2 for half the period of the industrial frequency remains proportional to the current (voltage) of the previous mode. The sum of these voltages is proportional to the emergency component of the current (voltage). the components are supplied to blocks 3, where dc signals are generated, the magnitude of which is proportional to the average or amplitude values of the emergency components of the phase values. From the outputs of the blocks 3, the direct current signals arrive at block 4, where they are compared with the other two. In non-phase-trip modes, the phase is excluded from the comparison circuit. If the emergency component of the voltage of one of the phases is greater than the same values in the other two phases, then the output of block 4 for the corresponding phase is a signal proportional to the emergency component, it is fed to the threshold unit 5 of this phase. At the outputs of block 4 for the other two phases, there is no signal in this case. If the fault component of the voltage (current) in two phases is greater than the same value in the third phase, such a signal appears on the two corresponding outputs of block 4. The signal in the compared phases is considered large if the ratio of the values of voltages (currents) they are more than 1.3-1.5. The latter is necessary because of the possible errors in the operation of the circuit elements 1,2,3, Iss ;; edovoy and showed that in most of the npjr KoCifivjK.TeTp4 Kbix short spells. -r sig zutz 1O. IAAGR -

more than damaged ones. For example, on a number of voltages with a voltage of 50О-750КБ, this ratio in the worst case reaches 5-6. Therefore, the device in question can be implemented using voltages or currents.

When single phase short circuit on the line connecting the power source to the unloaded transformer, the emergency components of the currents of the damaged and intact phases on the transformer side are equal to each other. However, in this case, there is enough vepik difference in the emergency components of the voltage of the respective phases.

Thus, with single-phase short circuits, the proposed device provides for the selection of one damaged phase (in the case of primary protection), for other types of asymmetrical damage, the choice of two damaged phases.

With three-phase faults, the integral values of the emergency components of all phase values are approximately the same and the choice of the faulty phase is not performed, which must be taken into account by the protection logic circuit.

When oscillations in full phase solutions at the outputs of block 2, there can be significant unbalance voltages associated with a change in the industrial frequency, since in all phases these voltages (currents) are the same, the device is not activated.

When swings in non-phase modes, the device also does not come into action, since the voltage (current) of the disconnected phase may not be applied to the comparison circuit.

The sensitivity of the threshold units 5 and the device as a whole is determined by the error

the isolation of emergency components associated with the variation of the parameters of the circuit elements. Uncertainties of the frequency deviation from the nominal value

not included; since they are the same for all phases.

The use of the allocation of emergency components of voltages (currents), blocks the formation of integral values.

Emergency components and comparison unit can significantly (in order) increase the sensitivity of the device. device operation does not exceed 20 ms.

sixteen

Claims (2)

1. Proceedings of TsNIEL vol., 2, Gosznergoiz.lat 1954, p. 62-80. 2. Atabekov GI. Theoretical Esso .Q you relay protection of high-voltage networks, SEI, 1957, pp. 185-295 - prototype.