RU78582U1 - PORTABLE DEVICE FOR HIGH VOLTAGE TESTS OF POWER CABLE LINES WITH DISTANCE RECORDER TO THE PLACE OF INJURY INJURY - Google Patents

Abstract

The utility model relates to electrical apparatuses and can be used to determine the distance to the place of electrical breakdown of the weakened cable line insulation during diagnostics by increased DC voltage using the electromagnetic wave voltage form at the beginning of the line.

A portable device for high-voltage testing of power cable lines with a distance recorder to the location of insulation damage, consisting of a measuring body: an analog-to-digital converter, an information processing unit, a digital distance indicator, and reflectogram visualization unit combined with a high-voltage source consisting of an adjustable inverter and a step-up transformer , high voltage rectifier and protective resistance. The joint work of which is ensured by the connection unit, consisting of a voltage divider that lowers the test voltage to a safe value necessary for the operation of the analog-to-digital converter and the operation of the test parameter control unit, the terminating resistors in it ground free cable conductors. Relay protection ensures the safe operation of the device and personnel, disconnecting it during breakdown of insulation during the test. The information processing unit in the measuring organ provides the operation of a digital distance indicator and a trace visualization unit.

Description

The utility model relates to electrical apparatuses and can be used to determine the distance to the place of electrical breakdown of the weakened cable line insulation during diagnostics by increased DC voltage using the electromagnetic wave voltage form at the beginning of the line.

A device is known for determining the distance to the place of damage to cable lines by the method of oscillatory discharge (instruction manual for the Iskra device, website www.zao-ehp.ru), consisting of means for outputting an oscillogram (visual indicator), a wave sensor, and a signal amplification unit. This device allows you to record the waveform of the voltage or current of the electromagnetic wave that occurs in the cable line under the influence of the test voltage as a result of an oscillatory discharge at the time of insulation breakdown (short circuit).

The device is characterized by the following disadvantages: lack of a source of test voltage - which entails the need for additional equipment, time and place for assembly of the circuit; the absence of additional special purpose resistors makes it difficult to determine the distance with interphase faults in cable lines. This is due to the fact that with this type of damage, additional circuits are involved in the transient, distorting the shape of the current and voltage. Such damage requires the use of special test circuits.

Closest to the claimed utility model is a device for determining the location of damage to cable lines by vibrational

discharge, (operating instructions for the “Flight-305” reflectometer, website www.elektronpribor.ru), consisting of an oscillogram output means (trace visualization unit), an integrated microprocessor, an analog-to-digital converter, and a signal amplification unit. This device allows you to measure on cable lines using one of three methods: pulse reflectometry; vibrational discharge method; pulse-arc method.

The device is characterized by the following disadvantages: lack of a source of test voltage - which entails the need for additional equipment, time and place for assembly of the circuit; the absence of additional special purpose resistors makes it difficult to determine the distance with interphase faults in cable lines. This is due to the fact that with this type of damage, additional contours are involved in the transient process, distorting the shape of the current and voltage. Such damage requires the use of special test circuits.

The objective of the utility model is the ability to significantly speed up and simplify the search operations to determine the location of damage to power cable lines during its testing. Known devices, this set of works cannot be performed.

The problem is solved due to the fact that a portable device for high-voltage testing of power cable lines with a distance recorder to the place of insulation damage, consisting of a measuring body: an analog-to-digital converter, an information processing unit and a trace visualization unit combined with a high-voltage source: an adjustable inverter, step-up transformer, high-voltage rectifier and protective resistance, the joint operation of which is provided by the connection unit, consisting present of voltage divider resistors, and to connect

devices to the conclusions of the cable line requires only a high-voltage wire.

On figa presents a structural diagram of a portable device for high-voltage testing of power cable lines with a recorder distance to the place of damage to the insulation, figb shows the voltage waveform at the beginning of the cable line at the time of breakdown of insulation during a single-phase short circuit, figv - voltage waveform in the beginning of the cable line at the time of insulation breakdown during an interphase short circuit with a terminating resistor, Fig. g illustrates the voltage waveform at the beginning of the cable line at the time of insulation breakdown and with an interphase short circuit without terminating resistors in the connection unit.

In Fig. A, an adjustable inverter (HP) 1 is connected to a step-up transformer (TP) 2, which is connected to a high-voltage rectifier (BB) 3. The protective resistance (SZ) 4 is connected to the connection unit (PSU) 5 connected in it through a voltage divider Rd ₁ , Rd ₂ to the core of the cable line A, (B), (C), free conductors B, (C), (A) and C, (A), (B) are connected through the terminating resistors Rc ₁ to the ground. To the voltage divider Rd ₁ , Rd ₂ , from the connection unit (PSU) 5, the test parameters control unit (BKIP) 6 and the analog-to-digital converter (ADC) 8 are connected. Relay protection is connected to the test parameters control unit (BKIP) 6 ) 7, which is connected with a high-voltage rectifier (BB) 3. An analog-to-digital converter (ADC) 8 is connected to an information processing unit (BOI) 9, which has an output to a digital distance indicator (DIR) 10 and a trace visualization unit (BVR) 11 .

The utility model operates as follows: an adjustable inverter (IR) 1 converts the supply voltage to a voltage of increased frequency (10 kHz) and feeds it to a step-up transformer (TP) 2, which increases the voltage amplitude to 10 kV, then

the voltage is supplied to the high voltage rectifier (BB) 3 with a voltage multiplication that provides the necessary level of test voltage. The rectified voltage, through the protective resistance (SZ) 4, which eliminates the overload of the rectifier diodes in case of insulation breakdown, through the connection unit (BP) 5, which ensures the normal functioning of the measuring part, (contains a measuring transducer - voltage divider R _d1 , R _d2 and matching resistors R _c1 - free for grounding the cable cores), gradually charge the insulation of the cable line A, B, C, having a distributed capacitance to the test voltage. In the presence of a defective area with weakened insulation, electrical breakdown occurs at this location. At the breakdown point, an ionized conductive channel (plasma) is formed, the resistance of which is practically zero - a short circuit. As a result, during breakdown, an electromagnetic wave is formed, which propagates on both sides of the line from the place of the insulation defect. Since the resistance at the ends of the lines A, B, C is much greater than the wave resistance, and at the breakdown point there is a short circuit, conditions are created for multiple reflections of the formed electromagnetic wave. The wave amplitude gradually decreases, so the voltage form at the terminals of the A, B, C lines acquires the character of damped oscillations, the period of which is proportional to the length of the cable section from the beginning of A, B, C to the breakdown point. This voltage from the output of the line, through the voltage divider R _d1 , R _d2 gets to the input of the analog-to-digital converter (ADC) 8 and the test parameters control unit (BKIP) 6. The analog-to-digital converter (ADC) 8 digitizes the analog signal from the measuring transducer R _d1 , R _d2 and transfers it to the information processing unit (BOI) 9 (made on the basis of the microcontroller), which analyzes the received information from the analog-to-digital converter (ADC) 8 and performs the necessary operations to display the results on a digital input distance dictator

(CIR) 10, which displays information in digital form about the distance from the output of the cable line to the place of a short circuit at the time of electrical breakdown of insulation. The information processing unit (BOI) 9 transmits the received signal to the reflectogram visualization unit (BVR) 11 containing a liquid crystal screen, by which a cable line is diagnosed and the place of damage is determined. Test Parameters Control Unit (BKIP) 6 - allows you to monitor the test parameters during the test of the cable line, relay protection (RE) 7 disconnects the power supply of the high-voltage part of the installation during insulation breakdown, by a low-current DC relay.

Information on the transient process in the line displayed by Fig.6, allows to judge the distance from the beginning of the cable line to the place of breakdown. It is known that the period of free oscillations in a line closed on one side and open on the other is four times the travel time of an electromagnetic wave: T = 4 · t _ave . The distance can be determined by knowing the time and speed of the wave:

.

To get an idea of the functioning of the device, the most difficult fault from the point of view of determining the location of damage in the cable line is the core-core. Using the device, a trace (Fig. C) was obtained, which allows assessing the place of damage, the waveform of Fig. G does not make it possible to judge the place of insulation damage during breakdown in the cable line during the test and cannot be used in the process of detecting a defect.

Thus, the use of the proposed device makes it possible to obtain a visual image of the time diagram of the voltage of the electromagnetic wave, reducing time and increasing the efficiency of the process of determining the location of damage to the cable line based

the use of a simple, widely used method of vibrational discharge in diagnosing a line.

Claims (1)

A portable device for high-voltage tests of power cable lines with a distance recorder to the location of insulation damage, consisting of an analog-to-digital converter and a trace visualization unit, characterized in that the measuring body, in addition to the above, includes: an information processing unit, a digital distance indicator combined with a high-voltage source, consisting of adjustable inverter, step-up transformer, high-voltage rectifier and protective resistance, joint work which is provided by the connection unit, consisting of a voltage divider, terminating resistors and the provided relay protection, and a control unit for measuring parameters.