SU46295A1 - Device for blocking the balance protection of parallel lines - Google Patents

Description

One of the main advantages of the lateral differential (balance) protection of parallel feeders over simple maximum protection from the reverse power relay is the quick disconnection of the damaged area.

Under the conditions of modern electrical systems / where sustainability issues become so urgent, this feature of balance protection is very valuable.

But along with the advantages of eight-defense, contributing to its spread, the indicated protection creates some operational inconveniences. This should include the following cases of line operation, when

.. the principle of transverse differential protection is violated and differential protection must be temporarily disconnected and replaced by another type of protection (maximum, remote, etc.): 1) disabling one of the parallel lines at the ends with transferring the entire load to the remaining line (Fig. 1), 2) work in parallel lines with unequal load, for example, temporary work of a double line on

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different buses (Fig. 2) and pi parallel operation on common buses while simultaneously feeding the second substation through one of the line taps (Fig. 3); 3) finding one of the lines under load and the other under voltage (Fig. 4), for example, in the case of testing the second line with a jog or "lifting from zero" with the linear oil switched off at the receiving end.

All of the above cases of double-line operation, which may temporarily occur for purely operational reasons, require the output of eight-dimensional protection for the duration of this mode.

Otherwise, with the through short circuits and the direction of power from the buses, the octagonal protection can act and the oil of one of the lines is turned off, not agreeing with the exposure of the rest of the network (Fig. 5).

It should be noted that in this case, the eight-protection scheme of the double, impedance start line is meant.

In the first of the above cases, such a temporary outage

The eight-pass order is automatically carried out by blocking the i- and dc current using the luaiio control of both liners. Chews concern the remaining cases of pno.JTbi doo1 lines listed above, when temporary disabling of eight-dimensional protection is required, the latter is carried out in practice by operational / operational personnel by hand.

As an example, one can mention the schemes with special plug switches accepted by Mosenergo,

A description of these schemes can be found in articles x published in the journal Electric Power Stations in recent years.

The practice of exploiting networks protected by the Siemens Eight has shown that when switching over to the network, there are cases of improper protection by the fault of the exploitation personnel who forget to make; corresponding switchings in protection circuits (see, for example, the article by engineer L. N. Goldberg and P. S. Klimenko in the journal Electric Stations No. 2, 1932).

In view of this, it is highly advisable to implement a figure-of-eight protection scheme, which provides for automatic shutdown of the latter when unbalance appears in the above cases and automatically switches it into operation to restore normal operation of parallel lines.

il

The proposed device for blocking the balance protection of parallel lines and its purpose is to achieve this goal. For this, a time relay is attached to the balance protection, and, according to the invention, the turn-off time winding circuit is conducted through the contacts of the start-up current relay, and the contacts of the time relay or the last controlled intermediate are connected to the switch-off circuit that controls the starting balance contacts gee; this achieves the opening of the switch-off circuit by the indicated interlocking contacts and, thereby, removal of the balance protection from the normal operation of lines with unequal loads.

In FIG. 1-5 depict the above-mentioned lines of operation when the principle of balance protection is violated; FIG. b-12-electric circuits of the device in various forms; FIG. 13 and 14 are two schemes for switching the device on to the balance protection circuit.

The action of the proposed device, consisting of a time relay and an intermediate one, is based on the following (Fig. 6). During normal operation and parallel operation of the feeders, the current and voltage triggering units (RD and PMN) of the eight-point protection keep their contacts open, with the main DC circuit between the RD and RMN passing through the closed

I / Y auxiliary intermediate relay contacts.

When an unbalance current appears, the RD closes the contact and, via an intermediate relay plus DC, is applied to the RV time, which has a delay greater than the time of the eight-hour protection (for example, 2 seconds).

If the unbalance is caused by a short circuit on one of the paired lines, the voltage triggering body will also come into effect and as a result of the directional function, the corresponding oil valve will turn off (rather than have the time relay act, shown in FIG. . 6) .. i

In the case, if the occurrence of unbalance current was caused by any switchings in the pair line and a temporary transition to one of the previously mentioned modes, the actuation of the current starting organ will not be accompanied by the triggering of the voltage organ, as a result of which the oil jerk does not follow, and the time relay shown in FIG. 6, and the intermediate Pfl relay will open the contacts. Thus, the eight-dimensional protection will be taken out of work.

Upon the restoration of the normal parallel mode, the operation of the lines, the current starting device will open its contacts and the RP will return to its original position.

Shown in FIG. The circuit can be simplified by combining the RP and PB Q one relay, as shown in FIG. 7. For this, it is necessary to have a timed relay with open contacts, designed for a long time under voltage. Such a time relay can be made without much difficulty.

In the above schemes, the eight-current protection start-up body serves at the same time as the starting body of the proposed device assigned to automatically blocking the eight.

At the same time, however, it should be borne in mind that the setting of the starting current body of the eight-protection device must exceed the unbalance current in case of through short circuits, which in its turn may significantly exceed the unbalance current in normal parallel lines,

In increasing the sensitivity of the proposed device for systems where the unbalance current in the case of dilution in parallel to the lines may be less than the unbalance current in case of through short circuits, it is advisable to use the device according to fig. eight.

Shown in FIG. 8, the switching device provides that the switching device has an independent starting body, which is one sensitive current relay, the installation of which can be reduced in comparison with the setting of the eight starting current body.

In the case of combining RP and RP in one relay, as was shown in FIG. 7, the proposed device l of the automatic blocking of the eight, equipped with a separate starting feather organ, will take on a rather simple appearance, since it will consist of only two relays (Fig. 9).

It should be noted that, as shown in FIG. 8 and 9,

A sensitive PA current relay must be designed for a continuous flow of load current.

In the event that it is not designed for this, then with a current of unbalance exceeding the setting of the current starting device of the G8, the PA coil should be bypassed.

FIG. 10 and 11 depict circuits similar to the previous ones and which provide for shunting the current coils of the RA at high unbalance currents.

A device for automatic blocking is most conveniently carried out independently of the start-up body of the eight-point protection using a self-current start (relay A in Fig. 12) installed on the difference of currents at least at one of the phases and fixing the presence of unbalance with unequal load lines. The sensitivity of this organ should be selected above the unbalance current in the normal mode of paired lines (regardless of the magnitude of the inrush current unbalance in the pass-through short).

One of the possible options for switching on an eight-dimensional protection equipped with an automatic interlock using Siemens RIV-6 and RSz relays is shown in FIG. 13.

To this eight-point protection, both feeders should also be provided for an additional set of maximum or distance protection associated with the installations of the rest of the system and the eight designed for inactivity for the time of parallel lines or short circuits on the receiving substation buses.

In the absence of additional sets of maximum or distance spool, on both feeders, an eight-dimensional protection circuit with a lock according to FIG. 12 takes the form indicated in FIG. 14. As can be seen from the drawing, the proposed device, consisting of an intermediate relay PfJ, a time relay PB and a sensitive current relay A, is inactive both during normal operation of paired lines and during

- disconnection of one of the lines. The device comes into effect only when diluting lines, blocking the circuit of half-second exposure of the RS relay. It should be borne in mind that in the case of testing one of the lines with a push for the first few seconds corresponding to the time delay RV, the half-second RSz circuit is not yet broken and, therefore, if turned on for a short time, the feeder being tested will turn off with a delay of 0 5 sep. This is one of the conveniences of the circuit of FIG. 13. . The proposed device for automatically blocking the eight-point protections is essentially quite simple, reliable and cheap, which means it can be successfully applied to existing paired lines equipped with balance protection, as well as to constructed and projected lines.

As already noted, the above options for automatic blocking of eight-protection are designed for protection circuits equipped with a current triggering organ with a volt-metering interlock.

With the same success, they can be applied in the same way in eight-dimensional protection, having a minimum impedance relay as a starting organ.

The subject matter of the invention.

Claims (2)

1. A device for blocking the balance protection of parallel lines during normal operation of both lines with unequal loads, containing a time relay and characterized in that the time relay winding circuit is routed through the starting current relay contacts and the time relay controlled by the latter relay included in the switch-off circuit, controlled by the contacts of the starting body of the balance protection, the purpose of opening the switch-off circuit by the indicated interlocking contacts and, thereby, withdrawal of the balancer panels out for lines during normal operation with unequal loads. 2. At the device according to claim 1, the use of a common for time relay and for balance protection of a starting organ.