CN103399265B - A kind of high voltage cable terminal partial discharge ultrasonic monitor - Google Patents

Abstract

An ultrasonic monitor for partial discharge at a high-voltage cable terminal. It includes a partial discharge sensor, a partial discharge signal acquisition and processing device and a power supply; the partial discharge sensor is composed of an ultrasonic sensor, and the three partial discharge sensors are respectively connected to the three signal acquisition input terminals of the partial discharge signal collector; the power supply and the partial discharge signal The collection and processing device is connected. The device of the present invention has the following advantages: 1. The structure is simple, the volume is small, it is easy to implement, and it is convenient for personnel to operate; 2. It is electrically isolated from the system to ensure the safety of the equipment; 3. The device will not damage the cable body and is easy to install. No need for cable line power failure; 4. Not subject to on-site electromagnetic environment interference, strong adaptability, and can be widely used; 5. High sensitivity, able to detect the discharge of the minimum 10pC, and realize the accurate measurement of partial discharge at the cable terminal.

Description

An Ultrasonic Monitor for Partial Discharge at High Voltage Cable Terminals

technical field

The invention belongs to the technical field of high-voltage power transmission and transformation, in particular to an ultrasonic monitor for partial discharge at a high-voltage cable terminal.

Background technique

In recent years, power cables have been widely used in urban power grids, followed by an increasing number of cable faults. As an important part of the cable, the cable terminal has a complex insulation structure, and there are many reasons that affect its insulation performance, and it is usually made manually on site, and poor craftsmanship is likely to leave hidden troubles, so the failure rate is much higher than that of the cable itself. Therefore, the evaluation of the insulation state of the cable terminal has very important practical significance for the safe and stable operation of the cable. As the precursor and main reason of insulation deterioration, partial discharge has been widely recognized by scholars at home and abroad. At present, the detection methods of cable partial discharge mainly include capacitive coupling method, inductive coupling method and directional coupling method based on pulse current, ultrasonic method based on partial discharge ultrasonic signal, ultra-high frequency method based on partial discharge ultra-high frequency signal and optical based method. The optical method of the signal, and the capacitive coupling method, the inductive coupling method and the ultrasonic method have good operation experience, and the directional coupling method, the ultra-high frequency method and the optical method have little research and operation experience, and it is currently impossible to carry out online monitoring of high-voltage cables . The capacitive coupling method is divided into built-in capacitive coupling method and external capacitive coupling method. The built-in capacitive coupling method usually installs the sensor on the semi-conductive layer of the cable. This method has high detection sensitivity and is not easily affected by external electromagnetic interference, but it needs to destroy the cable. The original structure, and the installation is very inconvenient, which is a huge hidden danger to the safe and stable operation of the cable; the external capacitive coupling method is to directly attach the metal electrode to the outer surface of the sheath of the cable or connector. Although it is easy to install, it is vulnerable to Due to the influence of the surrounding electromagnetic environment, the signal-to-noise ratio of the obtained signal is low, and in some cases, a power outage is required for system testing. The sensor of the inductive coupling method is generally made into a clamp type, which is large in size, easy to install, and has no effect on the cable body, but its sensitivity is low, it is susceptible to electromagnetic interference in the space, and the measurement is inaccurate. Ultrasonic method is one of the technologies that were successfully applied earlier in the field. The frequency band of the acoustic signal excited by partial discharge in the cable is between 20kHz-10MHz. Generally, the acoustic signal of 20kHz-300kHz can be used to detect the partial discharge signal in the cable. The frequency band of the piezoelectric crystal of the ultrasonic signal can basically cover this frequency band. Although the transmission attenuation of ultrasonic signals in different media is large, the transformer, GIS shell and the armor of the cable terminal are well connected, and the signal hardly attenuates. Installing the ultrasonic sensor on the transformer or GIS shell can effectively monitor the cable terminal of partial discharge. The ultrasonic method will not damage the structure of the cable, and the installation is very convenient, and it is less affected by external electromagnetic noise, so it is an ideal on-site monitoring method.

Domestic cable online monitoring technology research started relatively late, and is still under continuous development. At present, domestic detection and monitoring methods for XLPE power cables, especially cables with a voltage level of 110kV and above, are still very backward, and effective monitoring methods are lacking.

Contents of the invention

In order to solve the above problems, the object of the present invention is to provide an ultrasonic monitor for partial discharge at a high-voltage cable terminal.

In order to achieve the above object, the high-voltage cable terminal partial discharge ultrasonic monitor provided by the present invention includes a partial discharge sensor, a partial discharge signal acquisition and processing device and a power supply; wherein: the partial discharge sensor is a partial discharge signal sensor, which is composed of ultrasonic sensors, three The partial discharge sensors are respectively installed on the surface of the cable terminals, and are respectively connected to the three signal acquisition input ends of the partial discharge signal acquisition and processing device;

The partial discharge signal acquisition and processing device is a partial discharge signal acquisition and processing and display module, which collects the partial discharge signal of the three-phase power cable through the partial discharge sensor, then converts it into a digital signal, and performs corresponding processing, and finally according to the obtained result Display or output alarm signal;

The power supply is the working power supply of the partial discharge signal acquisition and processing device, which is connected with the partial discharge signal acquisition and processing device.

The partial discharge signal acquisition and processing device includes: a partial discharge signal amplifier, a hardware filter, a partial discharge signal collector, a partial discharge signal processor, a display and an alarm, wherein: the partial discharge signal amplifier is composed of a three-way differential amplifier circuit , for respectively amplifying the input signals of the three PD sensors, the three input terminals are respectively connected to the three PD sensors, and the three output terminals are respectively connected to the three input terminals of the hardware filter;

The hardware filter is composed of three-way filter circuits, which are used for shaping and filtering the three-way partial discharge input signals, and its three output terminals are respectively connected to the three sampling input terminals of the partial discharge signal collector;

The partial discharge signal collector is a three-channel analog-to-digital converter, which is used to convert three partial discharge analog signals into digital signals, and its output terminal is connected to the partial discharge signal processor;

The partial discharge signal processor is a digital signal processor, and its output terminal is connected with the display and the alarm, which is used to read the partial discharge digital signal from the partial discharge signal collector, and perform subsequent processing and calculation on it, so as to Discharge signal to identify the type of partial discharge, and determine the amplitude of the partial discharge signal, and then transmit the obtained information to the display and alarm;

The display and alarm are used to display the relevant information of the partial discharge signal, and give a real-time alarm according to the set warning value.

Described power supply is USP power supply circuit, and it comprises: A, B, C phase current transformer, three-phase rectification circuit, voltage stabilizing circuit, charging and discharging control circuit and storage battery; Wherein: A, B, C phase current transformer are The three current transformers installed on the three-phase power cables, the three outputs of which are respectively connected to the three-phase input circuits of the three-phase rectifier circuit, when the load current of the three-phase power cables is within the working range of the current transformers, A, B, and C phase current transformers obtain current from the three-phase load side and deliver it to the three-phase rectifier circuit;

The three-phase rectification circuit is used to rectify the three-phase output of the A, B and C phase current transformers, and its DC output terminal is connected with the input terminal of the voltage stabilizing circuit;

The voltage stabilizing circuit is a DC voltage stabilizer, the output terminal of which is connected to the input terminal of the charging and discharging control circuit, and is used for stabilizing the DC output of the three-phase rectifying circuit;

The charging and discharging control circuit is connected to the battery, and at the same time connected to the partial discharge signal acquisition and processing device through the power supply output terminal; the charging and discharging control circuit is used to control the charging and discharging of the battery according to the load current of the three-phase power cable, that is, when the load current When the current transformer is within the working range, the current transformer obtains the current from the load side, and the current is rectified and stabilized to supply the partial discharge signal acquisition and processing device, and at the same time to charge the battery; when the load current is lower than the current transformer’s working When within the range, the battery supplies power to the PD signal acquisition and processing device;

The battery is an energy storage battery, which is used to store electric energy and output electric energy when needed.

The partial discharge ultrasonic monitor at the high-voltage cable terminal provided by the present invention adopts an ultrasonic sensor with large gain, wide frequency band, good linearity and high sensitivity, and designs a corresponding signal amplification circuit and a filter circuit, and develops a partial discharge ultrasonic signal follow-up with the help of ARM The processing program can effectively monitor the partial discharge of the cable terminal, find insulation defects in time and track them in real time, and realize the display of the discharge amplitude of the partial discharge signal and the release of alarm information. At the same time, the UPS is used to take power from the load side, and finally realizes the on-line monitoring of partial discharge at the cable terminal.

The device of the present invention has the following advantages:

1. Simple structure, small size, easy to realize, and convenient operation by personnel;

2. It is electrically isolated from the system to ensure the safety of the equipment;

3. The device will not damage the cable body, and the installation does not require power failure of the cable line;

4. It is not subject to interference from the electromagnetic environment on site, has strong adaptability, and can be widely used;

5. High sensitivity, able to detect the discharge of the minimum 10pC, and realize the accurate measurement of the partial discharge of the cable terminal.

Description of drawings

Fig. 1 is a schematic composition diagram of an ultrasonic monitor for partial discharge at a high-voltage cable terminal provided by the present invention.

Fig. 2 is a block diagram of the partial discharge signal acquisition and processing device in the high voltage cable terminal partial discharge ultrasonic monitor provided by the present invention.

Fig. 3 is a block diagram of the power supply in the high-voltage cable terminal partial discharge ultrasonic monitor provided by the present invention.

Detailed ways

The ultrasonic monitor for partial discharge at a high-voltage cable terminal provided by the present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

As shown in Figure 1, the ultrasonic monitor for partial discharge at the high-voltage cable terminal provided by the present invention includes: a partial discharge sensor 1, a partial discharge signal acquisition and processing device 2 and a power supply 3; wherein: the partial discharge sensor 1 is a partial discharge signal sensor, which consists of Composed of ultrasonic sensors, three partial discharge sensors 1 are respectively installed on the surface of the cable terminal, and are respectively connected to the three signal acquisition input terminals of the partial discharge signal acquisition and processing device 2;

The partial discharge signal acquisition and processing device 2 is a partial discharge signal acquisition and processing and display module, which collects the partial discharge signal of the three-phase power cable through the partial discharge sensor 1, then converts it into a digital signal, and performs corresponding processing, and finally according to the obtained Display the results or output alarm signals;

The power supply 3 is the working power supply of the partial discharge signal acquisition and processing device 2 , which is connected with the partial discharge signal acquisition and processing device 2 .

As shown in Figure 2, described partial discharge signal acquisition and processing device 2 comprises: partial discharge signal amplifier 21, hardware filter 22, partial discharge signal collector 23, partial discharge signal processor 24 and display and alarm 25, wherein : The partial discharge signal amplifier 21 is composed of three differential amplifier circuits, which are used to amplify the input signals of the three partial discharge sensors 1 respectively, and its three input terminals are respectively connected with the three partial discharge sensors 1, and the three output terminals Be connected with three input ends of hardware filter 22 respectively;

The hardware filter 22 is composed of a three-way filter circuit, which is used for shaping and filtering the three-way PD input signals, and its three output terminals are respectively connected to the three sampling input terminals of the PD signal collector 23;

The partial discharge signal collector 23 is a three-channel analog-to-digital converter, which is used to convert the three-way partial discharge analog signals into digital signals, and its output terminal is connected to the partial discharge signal processor 24;

The partial discharge signal processor 24 is a digital signal processor, and its output terminal is connected with the display and alarm 25 for reading the partial discharge digital signal from the partial discharge signal collector 23, and performing subsequent processing and calculation on it, Thereby identifying the type of partial discharge according to the partial discharge signal, and determining the amplitude of the partial discharge signal, and then sending the obtained information to the display and alarm device 25;

The display and alarm device 25 is used to display the relevant information of the partial discharge signal, and perform real-time alarm according to the set warning value.

The functions of the partial discharge signal collector 23 and the partial discharge signal processor 24 can be completed by a high-performance ARM microcontroller chip.

As shown in Figure 3, the described power supply 3 is a USP power supply circuit, which includes: A, B, and C phase current transformers 31, a three-phase rectifier circuit 32, a voltage stabilizing circuit 33, a charging and discharging control circuit 34 and a storage battery 35; Wherein: A, B, and C-phase current transformers 31 are three current transformers installed on the three-phase power cable, and its three outputs are respectively connected with the three-phase input circuit of the three-phase rectifier circuit 32, when the three-phase power When the load current of the cable is within the working range of the current transformer, the A, B, and C phase current transformers 31 can obtain current from the three-phase load side and deliver it to the three-phase rectifier circuit 32;

The three-phase rectification circuit 32 is used to rectify the three-phase output of the A, B, and C-phase current transformers 31, and its DC output terminal is connected to the input terminal of the voltage stabilizing circuit 33;

The voltage stabilizing circuit 33 is a DC voltage stabilizer, and its output terminal is connected with the input terminal of the charging and discharging control circuit 34, and is used for stabilizing the DC output of the three-phase rectifying circuit 32;

The charging and discharging control circuit 34 is connected with the storage battery 35, and is connected with the partial discharge signal acquisition and processing device 2 through the power supply output terminal at the same time; the charging and discharging control circuit 34 is used to control the charging and discharging of the storage battery 35 according to the load current of the three-phase power cable , that is, when the load current is within the working range of the current transformer, the current transformer obtains the current from the load side, and the current is rectified and stabilized to supply the partial discharge signal acquisition and processing device 2, and at the same time to charge the storage battery 35; when the load current When it is lower than the working range of the current transformer, the battery 35 supplies power to the partial discharge signal acquisition and processing device 2;

The storage battery 35 is an energy storage battery for storing electric energy and outputting electric energy when needed.

The working principle of the ultrasonic monitor for partial discharge at the high-voltage cable terminal provided by the present invention is as follows: when partial discharge occurs at the cable terminal, ultrasonic waves will be radiated, and the ultrasonic signal can be collected and Electric conversion, and through the differential amplifier circuit to obtain the ultrasonic partial discharge signal of millivolt level, the signal is filtered and shaped, and then the analog-to-digital conversion is carried out to obtain the corresponding partial discharge digital signal; then the partial discharge digital signal is processed by the digital processor Identify, analyze and calculate to determine the type and intensity of partial discharge for further processing, timely discover insulation defects at cable terminals, and realize real-time tracking.

Claims (1)

1. a high voltage cable terminal partial discharge ultrasonic monitor, sensor (1), Partial discharge signal acquisition processing device (2) and power supply (3) are put in the described high voltage cable terminal partial discharge ultrasonic monitor office of comprising; Wherein: sensor (1) is put for local discharge signal sensor in office, it is made up of ultrasonic sensor, the surface that sensor (1) is arranged on cable termination is respectively put in three offices, and is connected with three signals collecting input ends of Partial discharge signal acquisition processing device (2) respectively;

Partial discharge signal acquisition processing device (2) is local discharge signal acquisition process and display module, it puts by office the local discharge signal that sensor (1) gathers three-phase electrical cable, then digital signal is converted thereof into, and process accordingly, the last result according to obtaining carries out showing or output alarm signal;

The working power that power supply (3) is Partial discharge signal acquisition processing device (2), it is connected with Partial discharge signal acquisition processing device (2);

It is characterized in that: described power supply (3) is USP feed circuit, and it comprises: A, B, C phase current mutual inductor (31), rectified three-phase circuit (32), mu balanced circuit (33), charge-discharge control circuit (34) and accumulator (35); Wherein: A, B, C phase current mutual inductor (31) is for being arranged on three current transformers on three-phase electrical cable, its three tunnel exports and is connected with the three-phase input circuit of rectified three-phase circuit (32) respectively, when the load current of three-phase electrical cable is within operation of current transformers scope, A, B, C phase current mutual inductor (31) obtains electric current from three-phase load side, and is flowed to rectified three-phase circuit (32);

Rectified three-phase circuit (32) carries out rectification for exporting the three-phase of A, B, C phase current mutual inductor (31), and its DC output end is connected with the input end of mu balanced circuit (33);

Mu balanced circuit (33) is direct current stabilizer, and its output terminal is connected with the input end of charge-discharge control circuit (34), carries out voltage stabilizing for the direct current exported rectified three-phase circuit (32);

Charge-discharge control circuit (34) is connected with accumulator (35), is connected by power supply output terminal with Partial discharge signal acquisition processing device (2) simultaneously; Charge-discharge control circuit (34) controls for the discharge and recharge of load current to accumulator (35) according to three-phase electrical cable, namely when load current is within operation of current transformers scope, current transformer obtains electric current from load side, this electric current supplies Partial discharge signal acquisition processing device (2) after rectifying and voltage-stabilizing, and is accumulator (35) charging simultaneously; When the working range of load current lower than current transformer, be that Partial discharge signal acquisition processing device (2) is powered by accumulator (35);

Accumulator (35) is energy-storage battery, for storage of electrical energy, and exports electric energy when needs.