SU834617A1 - Method of detecting post with damaged insulation in overhead electric power transmission lines - Google Patents

Description

I

The invention relates to electrical measuring equipment and can be used to determine electrical transmission in electrical networks with an insulated and compensated neutral.

Methods are known for determining support with damaged insulation on overhead transmission lines by monitoring the fault current through the metal parts of the support at the time of cutting D1.

However, the known methods provide reliable detection of a support with damaged insulation only in networks with a voltage of I10 kV and higher, but little effective in networks of 6-35 kV with an insulated and compensated neutral.

Closest to the present invention is a method for determining a support with damaged insulation on overhead electrical transmission lines in electric networks with an insulated and compensated neutral, which is based on remote measurement and comparison of emergency mode parameters in different parts of the network 2.

The disadvantage of this method lies in the low reliability of determining the support with damaged insulation at high x / transient resistance between the support and the ground.

The purpose of the invention is. Improving the reliability of determining the support with damaged insulation at large values of the transition resistance between the support and the ground.

Claims (2)

The goal is achieved by the fact that in the known method of determining the support with damaged insulation on overhead transmission lines in electric networks with insulated and compensated neutral, by measuring and comparing the parameters of the emergency mode, the electric field of 3 points outside the line, in the section, perpendicular to the axis of symmetry of the phase conductors, in the middle of the span of the line and at the place where the line support is installed at the same distance from the projection of the outermost wire to earth, the measured values of the electric field strength are compared, and the support with damaged insulation is determined by the factor of the excess of the electric field strength in the cross section at the support installation site compared to the value / intensity of the electric field in the middle span. FIG. 1 is a sketch of a portion of an overhead transmission line; Fig. 2 shows the distribution curves of the electric field intensity, explaining the essence of the method. The section of the overhead transmission line contains a support with damaged insulation 1, a support with intact insulation 2, phase circuits 3-5 and points 6-8 of measuring the strength of the electric field. The points - 6-8 measurements of the electric field intensity are located respectively at the place of installation of the support with damaged insulation 1, in the middle of the span and at the place of installation of the support with intact insulation 2, while all points 6-8 of the measurement of the intensity of the electric field are at the same distance U from the projection of the outermost phase wire 4 on the surface of the sempy outside the line alignment in sections perpendicular to the axis of symmetry of the phase conductors 3-5 at the operator level. According to the measured electric field strengths, it is possible to construct curves 9-I1 for the distribution of the electric field strengths (Fig. 2) in sections perpendicular to the axis of symmetry of the phase conductors 3-5 at the operator level, so that curve 9 corresponds to the cross section at the support with damaged insulation 1, curve 10 - section in the middle of the span, curve 11 - section at the support with intact insulation 2. Point 12 on curve 11 corresponds to the intensity of the electric p l at point 8 of measurement, point 13 on curve 10 to the intensity of the electric field at point 7 of measurement, and point 14 on curve 9 to the intensity of 4 electric field at point 6 of measurement . As can be seen from FIG. 2, curve 10 passes above curve 11 due to sagging of the phase conductors 3-5. The maximum sag is provided in the middle of the span, therefore the electric field in the middle of the span is always greater than near the support with intact insulation 2 when the measuring device (not shown) is located at the same height relative to the ground (the need to measure outside the alignment of the line is due to considerations safety techniques). In addition, in three-phase networks, when the operator is positioned with portable measuring instruments in the alignment of the line, there is a noticeable decrease in the value of the measurement signal due to balancing from the wires of the other two of the phase conductors 3-5. To determine the support with damaged insulation 1, it is necessary to measure the electric field strength at points 6-8, compare the measurement results and determine the support with damaged insulation 1. If support 1 fails, measurement point 6 has a signal whose value is determined by point 14 in curve 9, in measurement track 7, a signal whose value is determined by point 13 on curve 10; at measurement point 8, a signal whose value is determined by point 12 on curve 11. As can be seen from FIG. 2, the magnitude of the measured signal at point 6 of Bbmie measurement than at point 7 of measurement, which means damage to the insulation of support 1. Measuring and comparing the voltage levels of the electrical point of interest near the supports and in the middle of the span of an overhead transmission line allows one to reliably determine the support with damaged insulation at high transient resistance values between the support and ground. The invention of the method of determining the support with damaged insulation on overhead transmission lines in electric networks with, isolated and compensated by remote distance