RU148063U1 - DEVICE FOR REGISTRATION OF PHASE VOLTAGE ASYMMETRY IN NETWORKS WITH ISOLATED NEUTRAL - Google Patents

Abstract

A device for detecting phase voltage asymmetry in networks with insulated neutral, containing antenna sensors of induced voltage in the form of rods located parallel to the wires of the overhead power line, an actuator, one output of which is connected to the ground electrode, characterized in that the rods are fixed on a support on insulating bases on a safe distance from the wires of the power line and are connected in series in a chain, one end of which is connected with the second output of the executive A bar containing resistors and a display with memory.

Description

The utility model relates to electrical engineering and can be used to detect earth faults of all kinds in electrical networks with an insulated neutral of 6 ... 35 kV and primarily on overhead power lines.

A known zero-voltage voltage sensor of an overhead power transmission line when the wires are arranged on a support along the vertices of a triangle [1], comprising an antenna located parallel to the wires of the overhead line connected to one of the terminals of the executive body, with the ground terminal connected to the other terminal. The specified antenna is made of one rod located in the center of the triangle, at the tops of which there are wires.

The disadvantage of this sensor is that it has a low output power, therefore it is necessary to connect the signal from the antenna converter to an amplifier with a large input impedance and disconnecting the line is required for mounting the sensor.

The closest to the utility model in terms of technical essence and result is an overhead power line with an antenna of zero sequence voltage sensor [2], containing three antenna converters located at the vertices of a regular triangle, the center of gravity of which coincides with the center of gravity of the triangle formed by the line wires, and the combined the end of three antenna voltage converters is connected to one terminal of the actuator, the other terminal of which is connected to the ground electrode.

The disadvantage of this device is the possibility of using it only when the antenna converters and wires of the power line are located at the vertices of a regular triangle between the phases of the line, which complicates the installation, which requires disconnecting the line.

The purpose of the utility model is to expand the scope of multi-rod antenna voltage sensors for a three-phase power line with insulated neutral at any location of its wires.

To achieve this goal, antenna voltage sensors in the form of rods are mounted parallel to each other on a support on insulating bases under current-carrying wires at a safe insulating distance from the wires and are connected in series to a chain, one end of which is connected to the ground electrode through an actuator. The actuator may be, for example, a series-connected resistor and a light indicator (or a resistor and a display with memory). When there is sufficient voltage on the rods, the indicator light will light up or a message will appear on the display with a memory - “network short to ground”.

In FIG. 1 shows a section of a power line with one support 1, on which three phase current-carrying high-voltage wires 3, 4, 5 are mounted on insulators 2. At a safe insulating distance from current-carrying wires 3, 4, 5, antenna voltage sensors are installed in the form of rods 6 connected in series in the chain. The rods are fixed to the support 1 through the insulating base 7 and are directed parallel to the wires of the overhead power line. One end of the chain is connected to the actuator 8, containing a series-connected resistor 9 and a light indicator or display with a memory 10, connected through the grounding descent 11 to the ground electrode 12, located as the underground part 13 of the support 1, in the ground 14.

. Но из-за разного расстояния стержней в цепочке относительно токоведущих проводов емкости между проводами и цепочкой будут не одинаковые. Это приводит к появлению напряжение небаланса, наведенного в цепочке из стержней 6. Расчеты этих наведенных напряжений были выполнены методом фазных координат [3] для расположения стержней, показанного на фиг. 1.The device operates as follows. On a power line with an interphase voltage of 10 kV in normal mode, on each of the wires 3, 4, 5 relative to earth 14, the voltage is

. But due to the different distance of the rods in the chain relative to the current-carrying wires, the capacitances between the wires and the chain will not be the same. This leads to the appearance of an unbalance voltage induced in the chain of rods 6. The calculations of these induced voltages were performed by the phase coordinate method [3] for the location of the rods shown in FIG. one.

For the calculation, a three-phase 10 kV power line with the location of wires 3, 4, 5 in a triangle was used. The initial data for the calculation: the distance between phases - 1 m; the length of each rod 6 is 5 m, the distance between the rods is 20 cm; the upper rod is removed from the lower phase wires by a safe distance of 1 m.

The following types of modes were calculated: normal mode and modes with violation of the insulation of phase wires 3, 4, 5 relative to earth 14, for example, when insulators 2 are damaged at any point on the power line. In this case, the wires are connected through the grounding slopes with the grounding of the support. It is also possible to short circuit through an arc or short circuit when a wire breaks. At the same time, the following modes with insulation violation are considered: the closure of the phase wire 3 to ground 14; short circuit of a phase wire 4 to earth 14; the phase wire 5 is shorted to ground 14. When any of the phase wires 3, 4, 5 is shorted to ground 14, the voltage on the wire with damaged insulation is close to zero, and on the wires with undamaged insulation, the voltage relative to earth 14 rises almost to linear (interphase) voltage of 10000 V. Under the action of the increased voltage of two phase wires, an increased voltage is induced on the rods.

We present the results of calculations when a resistor 9 and a light indicator (or display with memory) 10 with a total resistance of 2 MΩ are connected to a chain of three rods 6 when they are horizontally arranged under the phases of the power line.

The unbalance voltage in normal mode is small and is 23 V. Under the action of such a voltage, a small current flows through the resistor 9 and the indicator light or display with memory 10, from which the indicator light 10 will not light, and there will be no message on the display with memory.

In the mode of closing the phase wire 3 to ground 14, the voltage on wire 3 relative to earth 14 is close to zero, and the voltage on wires 4 and 5 increases to almost 10,000 V. The induced voltage on the chain of three rods 6 is 157.2 V.

In the mode of closing the phase wire 4 to ground 14, the voltage on wire 4 relative to ground 14 is also close to zero, and the voltage on wires 3 and 5 also increases to almost 10,000 V. The induced voltage on the chain of three rods 6 is 127.6 V .

In the mode of closing the phase wire 5 to ground 14, the voltage on wire 5 relative to earth 14 is also close to zero, and the voltage on wires 3 and 4 also increases to almost 10000 V. The induced voltage on the chain of three rods 6 is 118.3 V .

From the above calculation results it follows that if the insulation of any of the phase wires is damaged, the induced voltage on the chain of rods 6 increases sharply. In this case, the indicator light will glow, or a message “on the network short to ground” will be displayed on the display, signaling a violation of the phase voltage symmetry.

As the number of rods in the chain increases, the induced voltage increases. So in a chain of five rods it increases by about 20 V compared to a chain of three rods.

Information sources:

1. The voltage sensor of the zero sequence of the overhead power line with the location of the wires on the support along the vertices of the triangle. Patent SU 674144, H02H 3/16, / R.Sh. Sagutdinov A.I. Selivakhin. - application No. 2471487 / 24-07 // Bull. No 26 on 07/18/79.

2. Overhead power line with zero sequence antenna voltage sensor. Patent SU 855 849, H02H 3/16, / R.Sh. Sagutdinov, V.Ya. Zharkov - application No. 2856696 / 24-07 // Bull. No.30 on 08/15/81

3. Melnikov N.A. The matrix method of analysis of electrical circuits. - M .: Energy, 1972. - 231 p.

Claims (1)

A device for detecting phase voltage asymmetry in networks with insulated neutral, containing antenna sensors of induced voltage in the form of rods located parallel to the wires of an overhead power line, an actuator, one output of which is connected to an earthing switch, characterized in that the rods are fixed on a support on insulating bases on a safe distance from the wires of the power line and are connected in series in a chain, one end of which is connected with the second output of the executive A bar containing resistors and a display with memory.

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