SU1742751A1 - Method of determination of uniform cable electric length - Google Patents

Abstract

Use: instrumentation technology, in particular the determination of the electrical length of a homogeneous cable. Summary of the Invention: Two synchronized sinusoidal voltages of multiple frequencies are applied to the controlled cable, the electromagnetic field voltage above the voltage cable of these frequencies is measured, the phase shift between the measured voltages is measured and the electrical cable is calculated using the formula 1 or more.

Description

The invention relates to an instrumentation technique and can be used to determine the electrical length of a cable.

The aim of the invention is to improve the measurement accuracy.

The drawing shows the block diagram of the device

The device contains a generator 1 divider 2, an adder 3, a monitored cable 4, a sensor 5, a receiver 6, a multiplier 7, a phase detector 8 and an information processing unit 9. Moreover, the first and second outputs of the generator 1 are connected respectively to the first input of the adder 3 and the input of the divider 2, the output of which is connected to the second input of the adder 3, the output of which is connected to the core of the cable 4. The output of the sensor 5 is connected to the input of the receiver 6, the first and second outputs which is connected respectively with the first input of the phase detector 8 and the input of the multiplier 7, the output of which is connected to the second input of the phase detector 8, the output of which is connected to the input of block 9.

The generator 1 generates a continuous sinusoidal signal with frequency ez, which is fed to divider 2, where it is divided by frequency n times, at its output a signal with frequency f | is obtained. These two signals are synchronized, i.e. phase relationships between signals with frequencies fi and fa do not vary with time. The two signals are then simultaneously applied to the adder O, summed up and form the measuring voltage which is supplied to the cable 4.

The electromagnetic field around the cable created by the measuring voltage is sensed by the sensor 5 and processed in the receiver 6, the signals with frequencies fi and fa are extracted and amplified, the signal with frequency fi is multiplied in frequency n times in multiplier 7, then compared in phase using a phase detector 8, the phase shift between these signals is proportional to the electrical length of cable I, calculated in block 9 using the formula

X

fe

XI SP

Aff

one

where is the measured phase shift;

P 1, the phase coefficients of the signals at frequencies fi and f2, respectively;

n is a natural integer greater than one.

Claims (1)

Claims The method for determining the electrical length of a uniform cable is that a measuring voltage is applied to the core of the cable to be monitored relative to the earth, characterized in that, in order to improve the measurement accuracy, the measuring voltage is formed as the sum of two synchronized sinusoidal signals t f f 1 with frequencies fi and T2 -, where n is natural an integer greater than one measures the strength of the electromagnetic field above the cable, separates the voltage from the measured signal at frequencies fi and f2, multiplies the voltage at frequency f by n times in frequency, measures the phases of the signal at frequency f2 and multiplied signal , calculate the phase difference of these signals and determine the electrical length of the controlled cable I by the formula I- o p 1 P - / 32 where Dose is the calculated phase difference; 1, the phase coefficients of the signals at the frequencies ft and T2, respectively, while the frequencies fi and f2 are selected in the non-linear portion of the phase-frequency characteristic of the cable being monitored. /// /// /// /// /// /// /// /// /// ///