SU661672A1 - Device for centralized current protection of electric distributing network attachments - Google Patents

Description

The invention relates to electrical engineering, in particular, relates to the relay protection of elements of energy systems and can be used as backup protection for powered connections of electrical distribution networks.

The known backup protection of powered connections is connected to current transformers of powered connections and uses a diode max. 1 circuit. The protection highlights the damaged connection and reacts to the current value in it.

When triggered, the time delay protection acts to shut off the power supply breaker.

Also known is the maximum current protection on the basis of a diode max detector, which provides, with a first time delay, the effect of turning off the switch of the damaged feed connection, and, second time, of switching off the switch of the power connection 2.

The device consists of connected to the current transformers of the powered connections of the current converter into proportional voltages, rectifier units.

INPUTS which are connected to the outputs of the transducers, and the outputs are connected in parallel through individual reacting bodies to the input of the common threshold element.

To the output of the common reactive element are connected two elements of the delay time for actuation. The first element with a lower setpoint, when triggered, sends a signal to individual response organs. If there is a current at the input and a signal from the first element of the shutter, the individual reacting bodies work and act on the opening of the switches of the powered connections.

If a switch fails, the time delay element with a larger setting acts to shut off the power supply switch.

Such a device is closest to the invention in its technical essence.

The drawback of the device is the possibility of non-selective disconnection of intact connections when the phases of currents in damaged and intact connections are shifted. This is determined by the fact that at times when the instantaneous

the value of the voltage at the output of the converter. The damaged connection is close to QQr; current can flow through the individual reacting organs of the intact connections and trigger them.

The aim of the invention is to eliminate. nonselective disconnection of intact connections when the phase shift of the currents of damaged and intact connections.

This goal is achieved by the fact that a device for centralized current protection of connections of electric distribution networks contains for each powered connection a current converter R a voltage to the output of which a straightening unit is connected, the first output terminal of which is connected to the first input terminal of an individual organ whose output is connected with the switch-off circuit of the powered switch, the second output terminals of the rectifier unit are interconnected and connected to the first input clamping a common threshold element, the second input terminal of which is connected to the combined second input terminals of individual reacting bodies, the output of the common threshold element is connected to the inputs of the first and second time delay trigger elements, the output of the second of which is connected to the supply circuit breaker connection, additionally equipped with a logical element And, the first input of which is connected to the output of the common threshold element, the second input -

 to the output of the first element of the time delay to trigger, and the output to the combined third input terminals of the individual reacting bodies.

-... „- .. y., FIG. 1 shows a block diagram of the network and a block diagram of the device; in fig. 2 is a structural block diagram of an individual reactive body; in fig. 3 - timing charts of the device.

The device for centralized protection includes a power system 1, a power supply switch 2, a wiring 3, a power supply 4, a power switch 6 for the power connections, a transformer 6 for the current of the power connections.

The device consists of connected to transformers 7 current powered connections of current transducers into proportional voltages, rectifier blocks 8, the inputs of which are connected to the outputs of converters 7, and the outputs are connected in parallel through having small input

resistance individual reacting bodies 9 to the common threshold input

item 10.

The output of the common threshold element 10

   GBD connected to the input of the pulse puller 11, the output of which includes elements

12 and 13 time delay to trigger.

- With the release of a common threshold element 10

and time delay element 13 with less

the setpoint signals are given to the logical

element And 14, whose output is connected

to the combined third input terminals

individual reacting organs 9.

Straightening blocks 8 and a common threshold element 10 form a diode macsilicector, and the presence between the outputs of straightening blocks 8 and the input of a common threshold element 10 of individual reacting organs 9 does not affect its operation, since the latter are made in such a way that the internal resistance is significantly less than the internal resistance of the common threshold element 10.

In the circuit of the maxilizer, the maximum of the voltages at the outputs of the converters 7 is supplied to the input of the common threshold element 10. In this case, the current flows

only through that rectifier 8 and that individual reacting organ 9, which is connected to the converter, which currently has the highest output voltage.

In the event of a short circuit at one of the connections, the effective value of the voltage at the output of the converter 7 of this connection (the voltage Ugaj.j-Ha of Fig. 3) will be greatest. However, if there is a phase shift of the currents in the connections in ..: vicinity of moments of transition of instantaneous values, the voltage at the output of converter 7 of the damaged connection through zero will be the highest instant value of voltage at the output of the converter of intact connection (voltage U & u Fig. 3). In this case, the current will mainly flow through the individual reacting organ 9 of the damaged junction (current i fcgHa Fig. 3), and at time intervals when the instantaneous value of the output voltage of the converter of the faulty attachment 7 is close to zero, and through the individual reacting organs of the intact coupling (current i8t.9 in Fig. 3).

If the instantaneous value of voltage

5 Ugyj..if at the output of the converter 7 of the faulty connection exceeds the response voltage of the common threshold element 10 (voltage Ucp.roHa of Fig. 3), then discontinuous signals appear at its output.

0 These signals are converted to continuous by pulse extender 11, which triggers the triggering time 12 and 13.

Claims (2)

After a time equal to the setpoint of the element of time delay-13, a signal arrives at its output, arriving at the input of the logic element AND 14, to another input of which intermittent signals come from the output of the common threshold element 10. Therefore, at time intervals / when the instantaneous value. the voltage at the output of the transducer 7 of the damaged connection exceeds the response voltage of the common threshold element 10; signals from the logical element AND 14 are sent to the individual response organs 9. The individual response organs 9 you are completed in such a way that they trigger and have a continuous signal at the output only when at the same time the current from the converter 7 and the signal from the AND 14 gate are present at its inputs. This condition is fulfilled only for the individual reacting element 9 of the damaged connection. Therefore, the device first effects the disconnection of the switch 5 only for the damaged connection. If a failure of this switch occurs, then after the activation of the time delay element 12 with a larger setpoint, the effect is triggered on the opening of the power supply circuit breaker 2. An individual threshold organ can be accomplished, for example, by sequential switching on (see Fig. 3) of the control key 15, the threshold element 16 and the output pulse expander 17. The use of the proposed device makes it possible to eliminate non-selective shutdowns of intact connections during the phase shift of the damaged currents and intact attachments. Claim 1. Device for centralized current protection of connections of electrical distribution networks, containing for each powered connection connected to the current transformer of the connection current converter to voltage, to the output of which is connected.n straightening unit, the first output terminal of which is connected to the first input terminal of the india -, a visionary reacting organ, the output of which is connected to the circuit for disconnecting the switch of the powered connection, the second output terminals of the rectifier of the rectifier unit interconnected and connected to the first input terminal of the common pragm element, the second input terminal of which is connected to the combined second input terminals of the individual reacting bodies, the output of the common threshold element through the pulse expander is connected to the inputs of the first and second time delay elements to trigger, the output of the second one connected to the circuit breaker disconnecting the supply connection, characterized in that, in order to eliminate the non-selective disconnection of intact connection due to the phase shift of the currents of the damaged and intact connections, it is additionally equipped with a logic element I, the first input of which is connected to the output of the common threshold element, the second input to the output of the first time delay response element, and the output to the integrated control terminals of individual reacting bodies . 2. The device according to claim 1, characterized in that, in order to increase reliability, each individual reacting body is made by means of a series-connected input controlled key, a threshold element and an output pulse expander. Sources of information taken into account during the examination 1. Gelfand Ya. S. Relein protection of distribution networks. M., “Energy 1975 s. 294-296. 2. Development of the project of new relay protection of women GRU-6KV Dzerzhinskaya CHP. Part I, research report. Ivanovo Energy Institute. V.I. Lenin, Ivanovo, 1973, inv. No. B 258089, p. 91-93. OmSL rp S ( Suf10 s p n p s ig.9 IPP PP I