ON METHODS OF TELEMECHANIZATION OF DISPATCHER CONTROL OF MINES

TROFIMOV R. F.

Docent, Candidate of Technical Sciences

The attained degree of mechanization of mines imposes exceptionally high requirements on the organization of production, both with respect to the speed and accuracy of control and in regard to the perfection of management. The existing organization and means of dispatcher control solve only part of the possible tasks, since the means of dispatcher control in mines consist only of telephone communication. It is time to raise the question of the need to apply other, more advanced forms of dispatcher control. Such forms include remote control, telemonitoring, and automatic control and regulation. With the existing methods of control in power supply, such forms are inapplicable. In order for them to be applicable, it is necessary to transfer the power supply to remote control, to automate the operating processes of electrical machines, substations, etc. The implementation of the latter tasks is possible when a number of other questions have been resolved, to the consideration of which we shall now turn.

Sources of operating current

In solving these tasks, the choice of the most rational sources of operating current is a very important factor.

The use of storage batteries requires large initial expenditures and careful maintenance. In addition, storage batteries poorly tolerate the temperature conditions of unheated premises. When processes on the surface are automated, premises may be unheated. In underground workings and on the surface, in addition to the foregoing, special premises will be required. Thus, it is irrational to use storage batteries as a source of operating current. For mines, the most rational sources of operating current may be current transformers and power or lighting transformers of low capacity. Power or lighting transformers of low capacity, as a source of operating current for feeding relays with closing contacts, have one substantial drawback: when a short circuit occurs between phases near the installation point of the circuit breaker, the latter may fail completely to operate, since the voltage supplied to the tripping coil will be insufficient. With relays having opening contacts, the circuit breaker will operate for any voltage decrease caused by any reasons. In general, it should be noted that in these cases selectivity is practically unattainable. Power or lighting transformers should be used for switching-on and switching-off purposes, but at normal voltage.

For the purposes of tripping oil circuit breakers during short circuits, more advanced circuits are those that use current transformers as the source of operating current. One method was described by K. L. Plyusnin in the journal Elektricheskie stantsii No. 6, 1939, using rapidly saturating current transformers of type TKB-1, manufactured by the Elektroapparat plant. A second method, proposed by the author of the present article, using current transformers with two secondary windings placed on one core—one for supplying the protection and the other for the closing devices—was published in Elektricheskie stantsii No. 2, 1940. From what has been considered, it follows that at mine substations, current transformers and low-power power or lighting transformers should be used as sources of operating current. The former should supply the relays and tripping devices during short circuits in order to disconnect the damaged section, while the latter should supply the relays of automatic-control circuits and, as indicated above, the closing devices of oil circuit breakers.

Drives for Oil Circuit Breakers

The next question that must be resolved is the drive for oil circuit breakers. The drive must be capable of repeated operation and controlled at a distance. The use of a drive of the GP type and similar drives requires the installation at substations of storage batteries of a heavy type, which, as noted above, is irrational. It would be possible to supply a GP-type drive from an alternating-current source through cuprous rectifiers, but this method is still at the stage of factory investigation, and it is unlikely that such a drive will be compact and capable of forming a single unit with the boxes used in underground workings. Under mine conditions, pneumatic drives can be used, but in many cases they will require a special compressed-air power network and additional electrical sources of operating current, which likewise cannot be considered rational.

With the existing power-supply schemes for mine consumers (radial, non-automated), direct-action motor drives operating from an alternating-current source can be used; in these drives, the connection between the motor shaft and the circuit-breaker shaft is effected directly by means of a system of gears and worm transmissions. At the end of closing, the motor is automatically disconnected from the network. The disadvantage of motor drives is the consumption of a large current during closing and the complexity of the design. Despite these disadvantages, such drives are used for circuit breakers of small and medium capacity. A direct-action motor drive can form a single structural unit with the box.

For carrying out instantaneous reclosing operations (in automatic-control circuits), a motor drive operating from an alternating-current source and connected by a transmission system to a manual automatic drive of the KAM type (a proposal of the author of the present article) may be more rational. In this case it is made capable of being controlled at a distance. The combination of these two drives, with a small structural alteration of the free-tripping mechanism, will make it possible to use them for repeated operation and for instantaneous reclosing. All this is feasible if: 1) the clutch of the closing lever is coupled through a transmission system to the shaft of the motor drive; 2) there are two closing levers, arranged at an angle of 180°. These closing levers must form a single unit with the clutch; 3) such a system is provided with a locking device to give the levers a stable position; 4) the ...

wind-up levers so that they can freely pass by the wind-up pawl; 5) shift the upper part of the locking pawl to the left, which is possible if the pin into which the spring of this locking pawl bears is moved in the same direction.

The schematic drawing of such a drive with changes and additions is shown in Fig. 1. The motor and the stop device are not indicated in the figure. The operating procedure of the drive parts remains the same, but the MV will be switched on both by the motor and manually, and switched off by the tripping coils and also manually. If there is a single wind-up lever, the entire device, including the motor, must be brought into the initial position for switching on, which will require special springs and, consequently, an increase in motor power in order to overcome their counteraction during switching on. In the drive (Fig. 1) no return is required, since one of the wind-up levers is always ready for the next switching on.

Other types of drives not described above are inapplicable at mine substations.

Fig. 1

1—housing of the automatic box, 2—shaft, 3—shaft lever, 4—wind-up lever, 5—wind-up pawl, 6—disk, 7—locking pawl, 8—disk roller, 9—disk pin (tripping), 10—spring, 11—roller, 12—latch lever, 13—roller lever, 14—tripping coil.

Automatic Control of Electrical Machines and Substations

As is known, the purpose of control automation is to speed up operations, increase the reliability of operation and the productivity of electrical machines, transformers, and networks, reduce energy consumption, simplify servicing, etc.

At the present time, the schemes and principles of automation of control of drainage installations, ventilation, hoisting, underground and surface transport, and other individual mechanisms or complexes of mechanisms located on the surface or in underground workings have been developed quite fully, and they (the schemes) are sufficiently described in the literature. True, some of them may still undergo changes and simplifications.

There is no special description in the literature of the automation of mine substations. Automation of surface mine substations, like that of all substations of industrial enterprises, must be reduced to the introduction of reserve transformers and feeders, as well as special schemes and devices for applying automatic reclosing when there are overhead lines beyond the surface substations, or blocking devices that do not allow substations to be disconnected when automatic reclosing is performed in the networks feeding the surface substations. All these questions have been sufficiently covered in the literature. Automation of underground substations and networks, with the existing radial power-supply schemes, must also be reduced to connecting reserve feeders. A more rational method may be considered the paired and automated feeders proposed by the author of the present article, which are described in the journal Ugol’, No. 2, 1940.

As calculations show, paired feeders require an increase in the volume of nonferrous metals not by 100%, but only by 40–60%.

Mine converter substations can also be automated, and there are enough circuits for this.

The brief survey given above shows that almost all mine mechanisms and substations can be automated. But this automation must be subordinated to centralized control from one location, using telemechanical devices for this purpose. Telemechanics—the technology of control at a distance—makes it possible to carry out centralized control and supervision both of individual mechanisms and apparatus and of entire complexes of mechanisms and devices, and serves as the technical basis of dispatching. On the basis of telemechanics and automation, entire installations can operate without service personnel or with a very small number of service personnel. Automated surface and underground substations, and even some distribution points, ventilation, water drainage, converter substations for contact electric-locomotive haulage, and in some cases transport, can be subordinated to telemechanical control from the dispatcher’s station. This type of technology, moreover, makes it possible to monitor the operation of all mechanisms and devices of the mine. We shall now choose the most rational method of telemechanization of dispatcher control.

Methods of Telemechanization of Dispatcher Control Applicable in Mines

The choice of the type of remote-control devices is determined by the number of objects served by them and by the nature of the communication lines that can be used. The number of objects of individual installations monitored from the dispatcher’s station will be from 1 to 10–12. The number of signals transmitted to the dispatcher’s station can be reduced to a minimum. Thus, for example, from each feeder it will be necessary to transmit two signals concerning the position of the oil circuit breaker. From the dispatcher’s station it will also be necessary to transmit two signals for controlling the oil circuit breakers. The same number of signals will be required for controlling electric machines with automatic starting and regulation, etc. In general, it is possible to limit oneself to transmitting signals only from those objects with respect to which immediate measures are required on the part of the dispatcher. Thus, the total number of signals transmitted from the dispatcher’s station and to it for controlling individual installations will be from 4 to 40. The latter figure refers to central substations.

At present there exist low-channel and multi-channel telemechanical devices. The former are used for a large number of objects located at a considerable distance from the dispatcher’s station. These systems considerably reduce the number of communication wires, but they require very complex and expensive transmitting and receiving devices, including protective measures against incorrect transmission of signals. Moreover, when telemechanical devices of several controlled installations are connected to one communication channel, any damage to the communication channel or damage to transmitting and receiving elements will interrupt telemechanical communication at once with all the controlled installations. In multi-channel telemechanical devices, the need to use transmitting and receiving equipment is eliminated. In this case it will be necessary to connect the transmitting elements directly with the actuating elements.

Such devices are simple, reliable, and inexpensive (for distances up to 4–4.5 km).

In power systems, taking into account the considerable simplicity and high reliability of multichannel remote-control devices, they accept the extra expense of multicore cables and use these devices even in cases where it would be more economical to use low-channel devices. In mines, a large number of signals will be required for devices located on the territory of the mine yard and close to it, or located on the surface not far from the dispatcher’s station. Thus, the principal installations will require short communication lines. The remaining installations, with a small number of signals, will be located at a distance of no more than 2–2.5 km. On the basis of the foregoing, it may be concluded that the most rational telemechanical devices for mines are multichannel devices. As communication channels, special cable lines should be used, or the wires of telephone lines should be employed.

An equally important question is that of telemetering. The number of quantities subject to telemetering can be reduced to a minimum, and one or two quantities can be measured at each point. It is necessary to measure currents in order to judge the degree of loading of mechanisms, electrical machines, transformers, and networks, as well as voltages (at central substations). The field of application of telemetering may be expanded to include longwalls and workings. To limit the number of indicating instruments on the dispatcher’s panel, it is advisable to use telemetering on demand, employing for this purpose switches installed at the dispatcher’s station. As telemetering devices, it is most expedient to use devices with electronic rectifiers, as the simplest and, for the given conditions, sufficiently accurate.

Conclusion

At first glance it may seem that the use of means of telemechanics and telemetering will require complex equipment and many communication channels, but in fact this will not be so expensive and bulky a system, and it will make it possible—most importantly—to raise mines to a higher level in the organization of dispatcher control, for which the need has already become urgent.