RU2470433C1 - Method to detect glazed frost effects on wires of power transmission line - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: invention relates to power engineering and can be used to detect glazed frost on wires of a power transmission line. The method includes sending a radio pulse along a power transmission line from the start of the line to the end of the line, and monitoring of a parameter related to change of radio impulse distribution along a wire section whenever glazed frost occurs. A feature of the method is the fact that using a radio pulse of a bell shape makes it possible to use this method on lines comprising equipment of high-frequency communication.

EFFECT: higher reliability of glazed frost effects detection, which will make it possible to timely carry out preventive heating of wires and to reduce probability of accidents occurrence.

Description

The invention relates to the electric power industry and can be used to detect ice on the wires of a power line.

A known method for detecting ice based on monitoring changes in the capacity of the wire-to-ground line when ice appears (AS USSR No. 448527, M. Cl. N 02 07/16, 10.30.74). The disadvantage of this method is the low sensitivity and, therefore, the low reliability of information about the onset of ice formation.

A known method for detecting ice on wires of a power line, including location of a portion of a wire by probe pulses and monitoring a parameter associated with a change in the conditions of their propagation over a portion of a wire when ice appears (Kazadaev A.P., Livshits A.L., Rudakova PM About icing sensors for overhead power lines. Materials of the II All-Union meeting "Melting ice on overhead power lines. Ufa, 1975, p.165-174). In the known method, a pulse signal partially reflected from the near boundary of the icing zone is recorded using a receiving device, and the propagation time of probe pulses from the beginning of the wire section to the near boundary of the icing zone and vice versa is used as a control parameter.

However, the fixation of partially reflected pulses is significantly difficult with a smooth change in the thickness of ice deposits along the wire, which is usually observed in practice, since the amplitude of the pulse grows slowly and it is poorly distinguished from interference. In the case when the wire is evenly covered with ice over the entire length, the known method does not provide detection of the appearance of ice. In addition, in this method, the requirements for the sensitivity and noise immunity of the receiving device of the reflected pulses are very high.

The closest analogue of the invention is a method for detecting ice formation on wires of a power line, including locating a portion of a wire with probing pulses and monitoring a parameter associated with a change in the conditions of their propagation over a portion of a wire when ice appears (Patent No.RU 2287883 C1 of 04/15/2005). The difference between the method is that the wire section is limited by high-frequency chokes, the probe propagation time from the beginning of the limited section of the wire to its end and back is taken as a control parameter, the average temperature of this section of the wire is determined, and the appearance of ice is judged by the change in the probe propagation time pulses caused by the appearance of ice, taking into account the influence on the controlled parameter of the temperature change in the length of the wire section.

The disadvantage of this method of detecting ice is that a short duration video pulse is used for sensing. Such a video pulse has a wide range of frequencies, which interferes with RF communications on the same power line. In addition, the main energy of the video pulse is concentrated in the low frequencies of the spectrum (starting from 0 Hz), and high frequencies are required to measure the propagation time of the probe pulses. Finally, the energy of the radio pulse is small due to the short duration of the video pulse.

The purpose of the invention is to overcome these disadvantages of the prototype, which will increase the accuracy and sensitivity when detecting ice.

This goal is achieved by the fact that the method for detecting the appearance of ice on the wires of the power line uses the transmission of a radio pulse from the beginning of the line to the end of the line and the control of a parameter associated with a change in the propagation conditions of the radio pulse over a portion of the wire when ice appears, take the propagation time as a control parameter the radio pulse from the beginning of a limited section of the wire to its end, determine the average temperature of this section of the wire, and about icy lines are judged by the change in the propagation time of a high-frequency signal caused by the appearance of ice, taking into account the influence on the controlled parameter of the temperature change in the length of the wire.

This increases the accuracy of measuring the propagation time of the radio pulse and, accordingly, the reliability of detecting the appearance of ice. The accuracy of measuring the transit time of a high-frequency signal is increased due to the following features of the proposed method.

Firstly, the radio pulse will have a longer duration, due to which the accuracy of measuring the propagation time of the radio pulse is increased. It is practically possible to increase the duration of the radio pulse (to the time the radio pulse passes from the beginning of the power line to its end and vice versa:

τ≤2 · L / C, where L is the length of the power line, C is the propagation speed of the radio pulse along the power line (approximately equal to the speed of light 3 · 10 ⁸ m / s). Under this condition, the reception of reflected signals will occur after the end of the transmission of the radio pulse. Consider, for example, a power line with a length of L = 30 km. In this case, the maximum possible length of the radio pulse will be equal to τ = 0.2 ms. Accordingly, the width of the spectrum of the radio pulse ΔF≈1 / τ = 5 kHz. The total energy of the radio pulse will be 200 times greater, compared with a standard video pulse with a duration of τ = 1 μs.

Secondly, the spectrum of the radio pulse has a maximum at the frequency F filling the radio pulse. Therefore, the main energy of the radio pulse (the maximum in the spectrum of the radio pulse) will be concentrated at a high frequency F, which increases the accuracy of measuring the propagation time of the radio pulse.

Thirdly, the bell-shaped shape of the envelope of the radio pulse leads to a narrowing of the spectrum of the radio pulse (compared with the spectrum of a rectangular signal). An example of a simple implementation of the bell-shaped form f (t) of the envelope of a radio pulse is the so-called “von Gunn window”:

f (t) = {1-cos (2πt / τ)} / 2, where t varies from 0 to τ (Digital filters. R.V. Hamming, Moscow, Sovetskoe Radio, 1980). This form of the radio pulse leads to a strong suppression of the side lobes of the spectrum of the radio pulse (compared with the spectrum of a rectangular signal). As a result, almost all the energy of the radio pulse will be concentrated in a frequency band of width ΔF≈1 / τ.

The practical value of the proposed method is associated with the fact that almost every high voltage power line has RF communication equipment necessary for the operation of RF protection of the power line, as well as for the transmission of telemechanics, relay protection and emergency control commands. In this case, HF communication transmits signals directly along the power line itself, in a narrow frequency band, a few tens of kilohertz wide, and the working frequency of HF communication can range from 40 to 1000 kHz. The use of a radio pulse with a bell-shaped envelope shape, having a longer duration, allows you to shift the frequency spectrum of the radio pulse to the frequency region, which lies away from the operating frequencies of the RF communication on the same transmission line. As a result, the location-based ice detection device and HF communications will be able to work on the same transmission line without interfering with each other.

The above estimates show the undeniable, obvious advantages of the proposed method over the prototype.

Improving the accuracy and reliability of determining the formation of ice on the wires of the power line will allow timely preventive heating of the wires, which will reduce the likelihood of accidents.

Claims (1)

A method for detecting the appearance of ice on wires of a power line, including transmitting a high-frequency signal through a power line from the beginning of the line to the end of the line and monitoring a parameter associated with a change in the propagation conditions of the high-frequency signal over a portion of the wire when ice appears, take the propagation time of the high-frequency signal from beginning of a limited section of wire to its end, determine the average temperature of this section of wire, and the appearance icing is judged by the change in the propagation time of the high-frequency signal caused by the appearance of ice, taking into account the influence on the controlled parameter of the temperature change in the length of the wire, characterized in that the high-frequency signal uses a radio pulse having a bell-shaped envelope, leading to a minimum width of the spectrum of the radio pulse, the frequency of the radio pulse is selected from the condition of the detuning from the operating frequencies of the RF communication via the power line, the duration of the radio pulse is taken less than or equal to 2L / C, where L is the length of the power line, C is the propagation speed of the high-frequency signal along the power line.