RU156984U1 - 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 arranged parallel to the wires of an overhead power line connected in series to a chain, one end of which is connected to the ground electrode through an actuator containing resistors and a display with memory, characterized in that the rods are fixed to the phase wires by means of insulators.

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, as a result, you have to connect the signal from the antenna converter to an amplifier with a large input impedance and a triangular arrangement of wires is required for mounting the sensor.

Known overhead power line with an antenna sensor voltage zero sequence [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 wires of the line, and the combined end of the three antenna voltage converters is connected to one output of the Executive body, the other output of which is connected to the ground electrode.

The disadvantage of this device is the possibility of using it only with the location of the antenna converters and wires of the power line along the vertices of a regular triangle between the phases of the line, which complicates the installation.

The closest to the utility model in terms of technical essence and result is a device for detecting phase voltage asymmetry in networks with isolated neutral, containing antenna sensors of induced voltage in the form of rods parallel to the wires of an overhead power line connected in series to a circuit, one end of which is connected to the ground electrode through an executive body containing resistors and a display with memory [3].

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

To achieve this goal, the induced-voltage antenna sensors in the form of rods located parallel to the wires of the overhead power line are connected in series in a chain, one end of which is connected to the ground electrode through an actuator containing resistors and a memory display, and the rods near the support are mounted on phase wires through insulators.

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 fixed on insulators 2. Antenna voltage sensors in the form of rods 6 connected in series to a chain are fixed under phase wires near the support 1 by means of insulators 7. 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.

. Расстояния от проводов 3, 4, 5 до стержней 6 одинаковые и определяются длиной изоляторов 7. Наведенные на стержнях напряжения равны между собой по величине и сдвинуты по времени друг относительно друга на 120 градусов. Подведенная к исполнительному органу 8 геометрическая сумма напряжений на стержнях составляет в нормальном режиме незначительное напряжение небаланса.The device operates as follows. On a power line with an interphase (linear) voltage of 10,000 V, the voltage in normal mode on each of the wires 3, 4, 5 relative to earth 14 is

. The distances from the wires 3, 4, 5 to the rods 6 are the same and are determined by the length of the insulators 7. The voltages induced on the rods are equal in magnitude and are 120 degrees shifted in time relative to each other. The geometric sum of the stresses on the rods brought to the executive body 8 is in normal mode a slight unbalance voltage.

In existing electric networks, the insulation of one of the phase wires relative to the ground is most often damaged, for example, when the knitting of the high-voltage wire 3 to the insulator 2 is destroyed. Then the phase wire is connected to the ground electrode 12 through the traverse and the grounding trigger 12. An earth fault mode appears, in which the capacitive the current closes through the grounding descent 11, the grounding of the support 12, through the capacities of undamaged phases 4 and 5 relative to the ground and through the 10 kV winding of the transformer supplying the line. The voltage of the wire 3 relative to the ground becomes close to zero, and on the rod 6 under this wire the voltage is close to zero. The voltage on the other phase wires 4 and 5 relative to the ground increases to almost 10,000 V. Then the voltages on the rods suspended under wires 4 and 5 also increase. The geometric sum of these voltages is supplied to the executive body 8, on the display 10 the inscription "Short circuit to ground in the 10 kV network" is displayed

To confirm the operability of the device, theoretical calculations of a three-phase power line by the phase coordinate method were performed [4]. For the calculation, we used a three-phase power line with an interfacial voltage of 10000 V with the location of high-voltage wires 3, 4, 5 in a triangle. The calculated parameters are accepted: the distance between phases 3-4, 4-5 and 5-3 - 1 m; the length of each rod 6 is 5 m, the distance from the phase wire to the rod (insulator length) is 20 cm. The resistance of the actuator 8 is 1.1 megohms.

In the normal mode of operation of a three-phase power line, when each of the three phase wires 3, 4, 5 has a voltage of 5774 V relative to ground 14, the unbalance voltage supplied to the actuator 8 is 5.1 V. Under the action of such a voltage through the resistor 9 and a light indicator or a display with memory 10 flows a small current, from which the light indicator 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 phase voltage on wire 3 relative to earth 14 is close to zero, and the phase voltage on wires 4 and 5 increases to almost 10000 V. The induced voltage on the chain of three rods 6 is 210.5 AT.

In the mode of closing the phase wire 4 to ground 14, the voltage on wire 4 relative to earth 14 is close to zero, and the phase voltage on wires 3 and 5 increases almost to the phase-to-phase 10000 V. The induced voltage on the chain of three rods 6 is 222 V.

In the mode of closing the phase wire 5 to ground 14, the voltage on wire 5 relative to earth 14 is close to zero, and the phase voltage on wires 3 and 4 increases to almost 10000 V. The induced voltage on the chain of three rods 6 is 210.9 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.

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, Н02Н 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 855849, Н02Н 3/16, / R.Sh. Sagutdinov, V.Ya. Zharkov - application No. 2856696 / 24-07 // Bull. No.30 on 08/15/81

3. The decision to grant a patent for a utility model by application No. 2014116178/07 (025472) IPC Н02Н 3/16. Application date 04/22/2014.

4. 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 isolated neutral, containing antenna sensors of induced voltage in the form of rods parallel to the wires of an overhead power line connected in series to a chain, one end of which is connected to the ground electrode through an actuator containing resistors and a display with memory, characterized in that the rods are fixed to the phase wires by means of insulators.

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