SU834816A1 - Device for earthing protection in networks with insulated or compensated neutral wire - Google Patents

Description

one

The invention relates to devices for protecting an electrical network against, g-to-ground closure, preferably an insulated and compensated neutral network.

Known devices for protection against earth fault, based on the measurement of the values of the total zero-sequence current Dl "

However, the devices operate non-selectively at high transient currents in intact connections and may fail to operate at low established currents in damaged connections, since they have constant self-regulating zero-sequence current settings.

The closest in technical essence to the present invention is a ground fault protection device containing, according to the number of protected connections, current transformers of a zero-series network with terminating elements connected at the output, the outputs of which are connected to control electrodes. thyristors connected in series with the executive bodies filled in from the power source, and the starting body connected to the zero-sequence voltage transformer 2.

However, this device does not have sufficient selectivity and sensitivity, it is easy to work on input signals, the magnitude of which is equal to or greater than the thyristor rectifier current, and simultaneous disconnection of several connections and damage to the thyristors is possible.

. The sensitivity of the device depends on the type of thyristors used and zero-sequence current transformers.

Claims (2)

The purpose of the invention is to increase the selectivity and sensitivity of the vehicle for protection against earth fault. The goal is achieved by the fact that a device for protection against earth fault contains, by the number of protected connections, a zero sequence current transformer with matching terminals connected at the output, the outputs of which are connected to the control electrodes of the thyristors connected in series with the actuators supplied from power source, starting body, connected by its input, to the voltage transformer Nut of the left sequence, the power source of the thyristors and the executive, organ c, is provided with an actuation member for actuating actuators, the input of which is connected between the common point of the thyristors and one of the poles of their power source, and a sawtooth generator, the triggering input of which is connected to the output of the actuator, and the return input for the actuation of the actuation element actuators, the output of the sawtooth generator is connected to the control to the input of the newly introduced regulated power source of matching elements, which are made in the form of control power amplifiers. The drawing shows the block diagrams of the proposed device for connections, the total number of which can be any. The device contains a zero-sequence transformer Inpr (TNNP), a starting element (SW) transformers 3 and 4 zero-sequence currents (TTPD), protected connections 5 and 6, switches 7 and a block 9 of controllable amplifiers (CU) resistor 10, responsive bodies (PO) II and 12, executive units (IO) 13 and 14, adjustable power supply 15 of controlled amplifiers, generator 16 of sawtooth voltage (HPL), actuating fixation element 17 of any actuators, and power supply 18. The device works as follows. In the absence of a single-phase ground fault in the network, the control unit 9, as well as RO (thyristors) 11 and 12, IIO 13 and 14 are without voltage. Thyristors are closed, and the EUT is de-energized. When a ground fault occurs in the network, for example, at connection 5, zero-sequence currents begin to flow through the TTP 3 and 4, and a zero-sequence voltage appears at the output of the TNNP 1, under the effect of which SW 2 triggers and starts begins to produce a sawtooth voltage, which is supplied to the control input of an adjustable source 15 of power supply to the controlled amplifiers. As a result, all amplifiers of BUU 9 are energized, varying in time approximately linearly, and at their outputs appear signals proportional in magnitude to zero-sequence currents flowing through TNNP 1 and PO 2, and the signal at the amplifier output, connected to TTPR 3 and 4 of damaged attachment 5, the largest. When this signal reaches a value equal to or greater than the value of the response voltage PO I1 (thyristor open). The RO triggers and actuates the EUT 13. It sends a signal to turn off the switch 7. At the same time, a signal appears at the output of element 17, which returns the FPT 16. To its initial state (the voltage at its output becomes zero) and relieves voltage with CCD 9. The RO-11 and IO 13 return to the initial state is performed automatically when the rectified voltage of the power supply 18 is passed through a zero value. If during the first half period the zero sequence voltage does not disappear, then the device is restarted, triggers and continues its operation (automatic search of the damaged connection until the voltage and zero sequence currents disappear, i.e. until the single-phase ground fault is eliminated. The ground on connection 6 the device operates as described above. The use of the actuation element of the actuation of the actuators, the sawtooth generator and an adjustable power source controlled amplifiers provide protection against earth fault with increased selectivity and sensitivity, which works reliably when changing zero-sequence currents over large limits. This is achieved by automatically changing the input parameters of the device. In addition, there is no need to use amplifiers with a wide KIM linearity Formula of the invention; A device for protection against a short circuit or in networks with insulated and compensated neutral, containing the number of protected connections of zero-sequence current transformers with matching elements connected to the output, outputs connected to thyristor control electrodes connected in series with actuators powered from a power source, a triggering organ connected to the voltage transformer of zero sequence with its input thyristors and actuators, characterized in that, in order to increase the selectivity and sensitivity, it is equipped with a fixation element The actuators are connected, between the common point of the thyristors and one of the poles of their power source, and a sawtooth generator, the triggering input of which is connected to the output of the triggering organ, and the return input to the output of the aforementioned actuating fixation element The sawtooth generator is connected to the control input of the newly introduced regulated power source of the above-mentioned matching elements, which are made in the form of a controlled amplifier d. Sources of information taken into account in ex: pertise 1. Industrial Energy, 1968, No. 3, p. 4-6. 2. USSR author's certificate No. 660143, cl. H 02 H 3/16, 1977. with: In s -l1 Hzzh u / / / eleven 12