SU858163A1 - Device for maximum current protection of radial networks - Google Patents

Description

one

This invention relates to relay protection of power supply elements.

Maximum overcurrent protection devices are known that are made with time delays selected on a stepped basis (from consumers to a power source) to ensure selectivity 1.

However, with a large number of stages of exposure time protections feed-. elements may reach values that are unacceptable under the stability conditions of the electrical system and electrical installations of consumers due to a decrease in voltage during short periods of time.

According to the Electrical Installation Rules (ПУЭ item P1-2-7), a relay protection device with dummy exposures ensuring selectivity of action is allowed to disconnect short circuits with time delays possibly according to the requirements of the reliability of the electrical system, while the protection acts as a backup,

In order to accelerate short circuit tripping, in addition to the maximum current protection used as the back-up circuit, other

Types of protection, for example current cut-offs, built up by short-circuit current on an adjacent element

from the network. Current cutoffs are usually caused by damage to the part of the protected zone, and if the network elements are located in close proximity, their application is not possible at all. To ensure

| n sufficient reliability of the electrical network in this case comes with a complex relay protection.

The closest in technical essence to the proposed device is a selective maximum

 protection of radial networks with interlocking protection of the feeder from protection of outgoing feeders; On the feed feeder, a cut-off is established, the action of which is blocked when

20 protection work on any of the outgoing connections. This blocking is accomplished by including in the supply protection circuit of the feeder of the open contacts of the relay, which is triggered by

 The closure of the contacts of the current relays in the protection circuit of the outgoing connection,

Such a lock eliminates the false action of the cut-off during a short circuit on the outgoing lines and at the same time allows a time delay of no more than 0.12 s, in which the cut-off time is reliably blocked in the end-to-end short circuit mode G. However, according to the requirements of the Rules devices of electrical installations (ПУЭ п.Ш-2-16) should be provided for redundancy in case of failure of the circuit breaker at the outgoing connection (long-distance backup), the second stage of protection should be set up on the feeder (backup a), the action of which is not blocked and the time delay is longer than the time of protection of the outgoing attachment. Consequently, backup protections, located closer to the power source, must be performed with time delays selected on a stepped basis. For branched radial networks, the delay protections can reach values that are unacceptable to stability conditions. According to the requirement of the Rules for the Electrical Device Installation (ПУЭ п, Ш-2-17), in these cases special devices for the failure protection of switches (LOC) should be provided. The purpose of the invention is to increase the speed of long-distance protection without disturbing selectively. This goal is achieved by providing a device for maximum protection of radial networks, providing current relays of waste and power connections with short-circuit contacts connected in series with time relay coils with deceleration to actuation, the contacts of which through the closure of the block contacts each of its switch connected to the electromagnets of the shutdown of these switches, are additionally introduced on to With the outgoing connection of the latching relay, its protection, the latching relay, the protection of the waste connections, and the general relay - repeater of the protection protect any of the waste connections, while the latching relay coil of the protection of the outgoing connection is parallel to the coil of the time relay with a response delay through the disconnecting contact of the latching relay to the protection of the outgoing connection, and to the circuit of the output time relay of protection with a delay for the actuation of the supply recipient. A disconnection of the disconnecting contact is re-fixing the start of the protection of any of the outgoing connections. FIG. 1 shows the protection circuit of the outgoing connection} in FIG. 2, the protection circuit of the supply feeder. The device contains, contacts 1, 2 and 3 current relays of the outgoing connection, time relay 4, relay 5 of the start release protection of the outgoing connection with a delay time drop, For example RP-252, contacts 5a, 56 ,,,, 5p relays of outgoing connections, closing contacts b of the switch, switch-off electromagnet 7, relay 8 of fixing the protection action of the outgoing connection, for example RP-23, overlays 9a, 9b, 9p, instantaneous relay 10, e.g. RP-23, k contacts 11, 12, 13 of the current relays of the supply feeder, output relay 14 of protection with a slowdown response, for example RP-251 or time relay, closing contacts 15 of the switch, shutdown electromagnet 16, In normal mode, contacts 1, 2, 3 and 11, 12 , 13 current relays are open, there is no voltage on relays 4, 5, 8, 10, 14, as well as on electromagnets 7 and 16. In the event of a short circuit on one of the outgoing connections, any of the contacts 1, 2, 3 (FIG. 1) and any of the contacts 11, 12.13 (FIG. 2) closes. When the contacts 1, 2, 3 close, relay 4 is activated and 5 (fig, 1). From the 3-pins contact of the relay 4 through the contacts b of the switch, a pulse is applied to the electromagnet 7, From the contacts 5a, 56 ,,, 5p (fig, 2), through the corresponding pads 9a, 96 ,,, 9, the relay 10 is triggered and opens the relay 14 , block the protection of the feeder, t, e, when the contacts 11, 12, 13 are closed, the relay 14 does not work. The time delay for the operation of relay 14 must be greater than the total response time of relay 5 and relay 10 (at least 0.12 s). When the contacts 4 are closed (FIG. 1), the relay 8 is triggered and, by its opening contacts, breaks the relay 5 circuit. When the relay 5 disappears, the relay OU disappears (FIG. 3), and the protection of the feeder unit is unlocked. The time delay for the falling out of the relay 5 makes it possible to rebuild from the switch off time. With a close short circuit (before the outgoing connection), the protection of the feed feeder is not blocked,. relay 14 is also activated by its closing contacts, through contacts 15 the switch sends a pulse to the electromagnet 16. If there is an outgoing connection in the protection circuit, the relay is turned on, the relay 8 is not installed and the circuit of relay 5 is interrupted by closing the contacts of the relay on.

The application of the proposed protection device allows refusing installation of backup protection on some stages and reducing redundancy protection time on other stages, refusing in some cases the installation of additional current cut-offs (for example, for low-voltage transformers) and special devices for failure backup of switches. (UROV).

Claims (2)

1. Chernobrov, N. Relein, protection. M., Energie, 1971, 2. Winer C, G. and Apsit G, A. An improved scheme for the protection and automation of substations of 6-10 KB industrial enterprises with continuous technology. New technology of power supply of industrial enterprises, f1 ,, MDNTI, 1975. .fa Behind L 3 fn UL Jt (Ljtil FIG. 2 ten IS sixteen