SU1575266A1 - Electric three-phase circuit with zero phase - Google Patents

Abstract

This invention relates to the field of electrical engineering, in particular, to three-phase electric networks supplying power receivers susceptible to disturbances in power quality. The aim of the invention is to improve the quality of electric power in susceptible electric consumers by providing a three-phase symmetric system of voltages at the break of one of the phases of the supply network, as well as ensuring the equality of the potential of the artificial zero phase to the ground potential. A three-phase electrical network consists of a three-phase system with phases 1-3, to which electrical receivers 13-15 are connected, which violate the voltage quality, a three-phase voltage system converter 4 without a zero phase into a three-phase voltage system with an artificial zero phase. connected inputs and outputs in the form of a transformer, the primary and secondary windings of which are connected according to the zigzag scheme. Electrical receivers 16-18, susceptible to voltage disturbance, are connected to the secondary windings. The electrical network contains a key 12, which is connected between the midpoint of the primary winding of the transformer and the zero phase of the network, and a key switching unit that closes the key 12 when one phase of the network is broken. The switching unit consists of current sensors 5-7 and voltage sensors 8-10 and logic circuit 11. 1 Cp

Description

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The invention relates to electrical engineering, in particular to three-phase electrical networks supplying electric receivers susceptible to power quality disturbances (CLE), and is an improvement of the device according to the author. No. 1304124, the invention can be used to supply various susceptibility factors with CEE to receivers.

The aim of the invention is to improve the quality of electric power in susceptible power consumers by providing a three-phase symmetric voltage system when one of the phases of the supply network is broken, and also by ensuring that the potential of the artificial zero phase is equal to the potential of the earth.

Fig. 1 is a schematic diagram of a three-phase electrical network; Figure 2 shows the principal circuit diagrams of a switching unit.

A three-phase electrical network consists of three phase conductors 1-3 and a neutral conductor, a converter 4 of a three-phase voltage system without a zero phase into a three-phase voltage system with an artificial zero phase, connected to three phase conductors, DT7 sensors, DT7, DT2 DTZ, inputs that are connected to the network between the input terminals and converter terminals, 8-Voltage sensors (DN1, DN2, DNZ), AND 11 logic circuit, to the input of which are connected the outputs of 5-7 current sensors and 8- 10 voltages, key 12 included between average the primary point of the converter and the zero phase of the network;

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c 45 2, Q in th,., 2, the key input is connected to the output of logic circuit 11. The power receivers 13-15, violating the quality of electricity (Z, Zz, Z3), are connected to phase voltages of a three-phase network with zero phase, and electrical receivers 16–18 susceptible to faulty CEE (Z, Zj-, Zg) are connected to terminals 19-22, i.e. on phase voltages. three-phase system with artificial zero phase. The same terminals 19-22 are connected to the inputs of voltage sensors 8-10. Converter 4 of a three-phase voltage system without a zero phase into a three-phase voltage system with an artificial zero phase is made with galvanically developed inputs and outputs in the form of a three-phase transformer, the primary and secondary windings of which are connected according to a zigzag scheme. The artificial zero phase, formed by the middle point of the secondary winding, is grounded,

The key switching unit (Fig. 2) consists of current sensors 5-7, voltage sensors 8-10, and a logic circuit made of logic element 23 and an amplifying element on transistor 24 and resistances 25-27. Logic element 23 performs logic functions 2-2-2AND-ZILI-NOT. I

The network works as follows. When one of the phases is broken (for example, phase 1), the current sensor 5 and the sensor 8 are activated. When combined sensors 5 and 8 are triggered, logic circuit 11 outputs a signal to the closure of key 12. This causes the g: zero connection phase and midpoint of the primary winding of the converter 4, Thus, the primary winding of the converter 4 has

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connected to phases 2 and 3 and the neutral wire of the mains supply, which leads to recovery of phase 1. Consequently, a symmetrical three-phase voltage system will be obtained at the output of converter 4. Performing converter 4 with galvanically open inputs and outputs allows the artificial zero phase 22 to be grounded and thus to achieve high stability of phase voltages. Current sensors 5-7 and voltage sensors 8-10 can be implemented, for example, on the basis of comparators, in which the input signal is compared with the reference signal. When the input signal disappears or decreases below a predetermined level, the sensor outputs a signal to the logic element 23, At simultaneous operation of the DT and DN of one of the phases, the logic circuit 11 outputs a signal to the control electrode of the switch 12, which can be performed

not, for example, based on a triac. Thus, the connection of zero and artificial zero-phases occurs only with the simultaneous disappearance of the current in the phase and the corresponding phase voltage. The necessity of triggering the control circuit while simultaneously issuing signals from the DN and DT is caused by the fact that the zero and the artificial neutral wires should be connected only in the event of a phase failure, while the current in the phase can disappear even if there is a short circuit in the line to the location DT. In addition, the phase voltage in a system with an artificial zero phase can also disappear in case of a short circuit in this system. The combined use of DT and DN ensures the closure of the key only in the event of a phase failure on the line.

Claims (2)

1. Electric three-phase network with a zero phase auth.St. No. 1304124, five 0 characterized in that, in order to improve the quality of electric power1 of susceptible electrical consumers by providing a three-phase symmetric system of voltages at one of the phases of the supply network, and also by ensuring equality of the potential of the artificial zero phase to the potential of the earth, key switching unit, which closes the key when one of the phases breaks and opens it at the breakage elimination, and the three-phase voltage system converter without zero phase into the three-phase voltage system with the claim solid phase, made with galvanically separated inputs and outputs in the form of a three-phase transformer, the primary and secondary leads of which are connected in a zigzag scheme, and the artificial zero phase formed by the output of the midpoint of the secondary winding is grounded while the network zero phase, and its control input is connected to the output of the key switching unit. thirty 2 .. A network pop.1, which reveals that the key switching unit consists of three current sensors, three voltage sensors and a logic circuit whose output is the output of the key switching unit, with the inputs of the voltage sensors connected to phase voltages a three-phase system with an artificial zero phase, and the current sensor inputs are connected to the mains phases between its input terminals and converter clamps immediately before the last, the voltage and current sensors outputs are connected to the logic circuit inputs, which turn on to Switch on in the absence of current and voltage in the phases of the same name and its shutdown in the presence of current and voltage in all phases. FIG. g