SU41597A1 - Device to protect mercury rectifier plants - Google Patents

Description

When parallel operation of mercury rectifiers, it is difficult to protect them under the obligatory condition of selectivity of operation of protective devices of individual network elements.

The nature of the difficulties associated with this issue is derived from a review of the concept of a mercury rectifying installation with several mercury rectifiers operating in parallel on a common network, shown in FIG. 1 drawing.

In the event of a short circuit in a network or in an external DC network, it is desirable to have a certain time delay on the installation protection devices so that instantaneous non-establishing short circuits do not result in the disconnection of all parallel operating units and thus do not damage the entire voltage installation.

On the other hand, in case of reverse ignition and short circuits on the anodes inside mercury rectifiers, in order to avoid melting of the anodes, deterioration of the vacuum and prolonged outage of a defective mercury rectifier, it is necessary that it be quickly disconnected from both the DC side and from the AC.

(426)

This requirement is so essential that, in the absence of satisfactory protection schemes satisfying both the first and the second conditions, during the design and operation, they gave preference only to the conditions for protection of mercury rectifiers from reverse ignitions, refusing for IT to delay oil. Nominal switch VM. In this case, the basic protection scheme is usually reduced to the following (Fig. 1): the oil switch of the VM on the AC side is installed without a time delay; in one pole from the side of direct current, the high-speed automatic reverse current (BAU) is switched on.

In this case, with reverse ignition in one of the mercury rectifiers, all units P operating in parallel with it feed short from the DC side, and the high-speed automatic machine of the defective mercury rectifier, due to the presence of reverse current, has time to turn off earlier than it will come MB switches all other (healthy) units. On the AC side, the diseased unit shuts down after approximately 0.25 seconds (the switch / IED proper time). Overload

In the external network, the high-speed circuit breaker does not work, and all units are protected by an oil switch on the AC side.

On the DC side, normal maximum automata (not shown in Fig. 1) can be switched on to the second pole of each unit, which can be achieved by shutting down all units from the overloads not on the AC side, but on the DC side.

This issue, however, is of no fundamental importance, and with perceptible additional costs these automata are unlikely to significantly improve the operating conditions of the installation.

When the installation is protected according to the above scheme, the mercury rectifier is protected against reverse ignitions, but any overcurrent points of the installation of maximum automatic switches or a VM switch entail an instant, limited by its own time of operation of the automatic devices, shutting down all units and removing the current setting, which is a significant disadvantage in the operation, especially of installations such as traction, where instantaneous load peaks can be observed quite often.

In order to eliminate this drawback, a device is proposed for selectively protecting mercury rectifier installations, in which a reverse current relay connected to a direct current circuit is provided with interlocking contacts included in the control circuit.

Supplying the reverse current relay with interlock contacts included in the control circuit of the switching devices, in order to realize the selective action of the latter, namely, to prevent the operable mercury rectifier from shutting down, is generally well known.

In the proposed device, normally unplugged reverse current relay contacts are included in the coBiVrecTHo special control circuit with maximum relay contacts located on the AC side and a time relay controlled by others (maximum relays also located on the AC side.

The proposed device satisfies the listed conditions of instantaneous disconnection during reverse ignition and disconnection with a time delay in overloads in the external network, operates both in parallel operation and in operation of one unit, and costs a negligible cost for an additional set of maximum instantaneous relay ( in addition to the main kit, acting in conjunction with a relay of hephemen and protecting the installation from overload) and on one electromagnetic relay of reverse current, installed in the constant circuit th power of each unit.

FIG. 2 of the drawing shows a trilinear schematic diagram of the proposed device for protecting one mercury rectifier in the normal mode of the latter, and FIG. 3- the scheme according to FIG. 2

From the AC side, two sets of PMM, PMM and PMM, PMM of maximum relays controlling the time relay PB are included in the mercury rectifier circuit. The circuits of these relays include normally open interlocking contacts of the relay of reverse current included in the rectifier circuit from the direct current side, to that very pole in FIG. 1, which includes Bao.

For PMMi and PMM relays, the moving current is set to the permissible transient overload of the mercury rectifier (on the order of 200% of the nominal); these relays, in conjunction with the time relay PB, provide protection against overload in the external DC network with any desired time delay. For PMM and PMM relays with normally open contacts, the moving current is set to about 90-lOO o from the nominal circuit current; These relays in conjunction with the electromagnetic relay ER, which during idle operation j of a mercury rectifier are closed circuits, which open at the time when I reaches the external DC network,; approximately 80-90 / ,, nominal value of the PIA, carry out protection from backward: hall-ganiy,

The mode of operation of the protection is as follows (Fig. 3). During idle operation of mercury rectifiers current / g in the external network of direct current is less than 80-90 ° / o; therefore, the relay contacts are closed; current / AC side less than 90-100% of nominal; consequently, the contacts of the PMMu and PMM relays are open. The contacts of the RMM and PMM relays are also open. Consequently, the time relay coil RV does not receive power; the relay contacts are open and off, and the oil switch coil is not idle while not receiving power; VM oil switch remains on.

In normal operation: / g more than 80-90 ° / 0; / more than 80-90 o, but less than 90-100%; therefore, the relay opens its contacts, and the remaining relays remain in the same position, i.e. with open contacts; the oil switch remains on.

With a small overload, when / g is more than 90-100%, and / j is more than 90, but less than the installation current of the PMMi and PMMz relays, these relays continue to keep their contacts open, but both other maximum relays RMMz and PMM close their contacts; but since the relays of the electronic relay remain open, the oil switch remains on.

In the event of a prolonged overload or short circuit in an external DC network, the current / g is made more permissible, and the current / i is greater than the established moving current of the PMM-1 and PywyWai relays and all maximum relays close their contacts, and since the relay contacts remain open, the time relay coil receives power, and after a set time delay the relay RV closes its contacts; I turn it off, and the oil switch coil receives power through the auxiliary contacts of the relay RV and the VM switch turns off the rectifier with a time delay.

In the event of a short circuit (reverse ignition) inside a mercury rectifier, the value of direct current in the normal direction through the pole on which the relay is installed decreases to zero when one mercury rectifier is operating and takes the opposite direction when several mercury rectifiers work in parallel; Consequently, the current / g is less than 80-900 / 0, and the current L is greater than 90-OO / V and more than the current setting of the RMM and BC; all relays РЭМ, РММ, РММ PMMi, РМЛ / 2 close their contacts, time relay РВ comes into effect; Turning off the oil switch coil is supplied with power via the relay contacts of the relay and the PMM or RL / L / 4, and the oil switch turns off without time delay.

The subject matter of the invention.

A device for protecting installations with mercury rectifiers, consisting of maximum and reverse current relays, which is powered by the direct current side and equipped with interlocking contacts located in the control circuit to prevent non-selective shutdown of the serviceable rectifier, characterized in that it is normal the open blocking contacts of the reverse-voltage relay are included in the circuit of the switching-off coil VM of the oil switch in series with the normally open contacts of the instantaneous maximum relays PvMMg, PMM, located on the AC side, and the relay circuit RE, RZhMd, PMM, are shuit with normally open contacts of the RV time relay, controlled by the instantaneous maximum PMMj, PMM. Relays, also located on the AC side and reacting to more than the relay PMM and PMM, the current strength, so that during a short circuit on the DC side, the VM coil can be powered only through the RV relay contacts, i.e. with a proper time delay, and during reverse ignition, the VM coil can be powered without exposure time through the relay contacts RE and RMM. or re and PMM.j.

to the author's testimony of D. S. Livshits

NO 41597

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