CN204008979U - The early warning of power cable insulation On-line Fault and positioning system - Google Patents

Abstract

The utility model discloses an on-line early warning and positioning system for electric cable insulation faults, which comprises a wave reflection fault locator, a GPRS communication module, a high-frequency sensor, a ground wire, a host computer and a display. The utility model is simple in structure and safe in use. It monitors the grounding current signal on the grounding wire of the power cable through a non-contact high-frequency sensor, and then monitors the insulation fault of the power cable. The wave reflection fault locator only sends a signal to the host computer through the GPRS communication module when the wave reflection fault locator detects high-frequency transient traveling waves, which reduces the signal processing pressure of the host computer. The utility model monitors the operation status of the power cable in real time, and sets early warning information according to the number of monitored electrical signals, which helps electric power maintenance personnel to prepare for maintenance in advance or shorten the maintenance time when they arrive at the maintenance site.

Description

On-line early warning and location system for power cable insulation fault

technical field

The utility model belongs to the technical field of power cable fault detection, in particular to an on-line early warning and positioning system for power cable insulation faults.

Background technique

Cross-linked polyethylene (XLPE) power cables are more and more widely used due to their superior electrical, thermal and mechanical properties, easy laying, and simple operation and maintenance, and have become the mainstream of cable development. However, a large number of operating practices of power companies and power plants show that XLPE power cables are not maintenance-free. Common cable faults mainly include: 1) External reasons such as poor quality of intermediate head, loose crimped joint, excessive contact resistance, external force impact, etc., as well as the temperature rise of the cable head caused by long-term operation of the cable, causing the cable to overheat and burn through the insulation , Such faults can generally be found by maintenance personnel in their daily maintenance work; 2) Cable insulation breakdown, short-circuit faults, ground faults and other accidents, resulting in power outages, fires and other accidents, such faults are generally not easy to check, because the cable itself is very long , and it is often caused by some kind of defect, which makes this kind of failure unpredictable. Often, the specific location can only be known by checking the line after the accident, which not only takes time but also affects the time for line repair. At present, the detection of cable faults includes the bridge method and the wave reflection positioning method, but it is mainly aimed at the factory inspection of cables, and is designed as a hand-held detection device, which cannot meet the needs of online monitoring of power cable insulation faults.

Contents of the invention

The utility model aims at the deficiencies of the cable delivery detection device, and provides an online warning and positioning system for power cable insulation faults, which can monitor the condition of power cables in real time and in a centralized manner with multiple lines, and propose pre-alarm and pre-positioning according to the monitoring data, which is convenient and timely. The point of failure is convenient for maintenance personnel to maintain the power cable line.

The utility model solves the above technical problems through the following technical solutions:

An online early warning and location system for power cable insulation faults, comprising a wave reflection fault locator, a GPRS communication module, a high-frequency sensor, a ground wire, a host computer and a display, characterized in that:

Grounding wire, the metal sheath that comes with the power cable, one end is directly grounded, and the other end is grounded through a gap;

The high-frequency sensor adopts the open coil method, and is hung on the grounding wire of each section of power cable through the coil;

The wave reflection fault locator connects the high-frequency sensor through the signal line, records the electrical signal received by the high-frequency sensor, and locates the fault point;

The GPRS communication module sends the electrical signal data recorded by the wave reflection fault locator and the location data of the fault point to the host computer through wireless signals;

The upper computer receives the electrical signal data sent by the GPRS communication module and the location data of the fault point;

The display shows the electrical signal diagram received by the upper computer and the location data of the fault point.

In order to obtain better technical effects, the wave reflection fault locator is HDTDR-80 wave reflection method cable fault locator, PMDJ-102A cable terminal or TWPD-2622 digital partial discharge detector; The wave reflection fault locator of each section of power cable monitors the number of electrical signals, and sends corresponding early warning information according to the number of electrical signals monitored within the set time period; the alarm device receives the early warning signal sent by the counter and sends out an alarm prompt.

The utility model is simple in structure and safe in use. It monitors the grounding current signal on the grounding wire of the power cable through a non-contact high-frequency sensor, and then monitors the insulation fault of the power cable. The wave reflection fault locator only sends a signal to the host computer through the GPRS communication module when the wave reflection fault locator detects high-frequency transient traveling waves, which reduces the signal processing pressure of the host computer. The utility model monitors the operation status of the power cable in real time, and sets early warning information according to the number of monitored electrical signals, which helps electric power maintenance personnel to prepare for maintenance in advance or shorten the maintenance time when they arrive at the maintenance site.

Description of drawings

Fig. 1 is the structural representation of the utility model;

Fig. 2 is a structural schematic diagram of the power cable of the utility model when it fails.

Detailed ways

Further explain the content of the utility model below in conjunction with accompanying drawing and embodiment.

An online early warning and location system for power cable insulation faults, including a wave reflection fault locator 4, a GPRS communication module 5, a high-frequency sensor 3, a grounding wire 2, a host computer, a display, a counter and an alarm,

Grounding wire 2, the metal sheath of each section of power cable 1 on the transmission line is used as the grounding wire 2, one end of which is directly grounded, and the other end is grounded with a gap;

The high-frequency sensor 3 adopts an open coil method, and is hung on the ground wire 2 of each section of the power cable 1 through the coil;

Wave reflection fault locator 4, install a wave reflection fault locator 4 on each section of power cable 1, connect the corresponding high-frequency sensor 3 through the signal line, record and save the electrical signal received by the high-frequency sensor 3, and perform fault detection point positioning;

The GPRS communication module 5 sends the electrical signal data recorded by the wave reflection fault locator 4 and the location data of the fault point to the host computer through wireless signals;

The host computer receives the electrical signal data and the location data of the fault point sent by the GPRS communication module 5;

Display, showing the electrical signal diagram received by the host computer and the location data of the fault point;

The counter records the number of electrical signals monitored by the wave reflection fault locator 4 of each section of the power cable 1, and sends corresponding early warning information according to the number of electrical signals monitored within the set time period;

The alarm device sends out an alarm prompt after receiving the early warning signal sent by the counter.

As an optimization, the wave reflection fault locator 4 is HDTDR-80 wave reflection method cable fault locator, PMDJ-102A cable terminal or TWPD-2622 digital partial discharge detector.

The metal sheath of a single-core power cable is usually grounded directly at one end and grounded at the other end through a protective gap. Under normal operation of the cable, the steady-state grounding current of its metal sheath is extremely small, mainly capacitive current. Assuming that the three-phase core wire voltages of the single-core cable under normal operating conditions are The load current is Taking phase A as an example, the steady-state ground current of its metal sheath under normal operation can be expressed as:

${\stackrel{<span\; class="notranslate">\; \&Center\; Dot;</span>}{\mathrm{<span\; class="notranslate">\; I</span>}}}_{\mathrm{<span\; class="notranslate">\; gA</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; j\&omega;C</span>}{\stackrel{<span\; class="notranslate">\; \&Center\; Dot;</span>}{\mathrm{<span\; class="notranslate">\; u</span>}}}_{\mathrm{<span\; class="notranslate">\; A</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

In the formula: C is the equivalent capacitance between the cable core wire of each phase and the metal sheath of the phase.

When the cable has a metal sheath insulation fault at X, the resistance to ground at X changes from infinite to a resistor 6 with a resistance value _Re , as shown in Figure 2.

Take the potential of the grounding point G of the cable sheath as the reference potential, and the fault point X forms a current path through the ground and G. The steady-state ground wire current of the sheath can be expressed as:

In the formula: M _AA is the mutual inductance coefficient of the cable core wire to the A-X-Re-G circuit; L is the equivalent inductance from the fault point of the sheath to the grounding terminal.

Comparing formula (1) and formula (2), it can be found that when a fault occurs, the ground current generated by the cable metal sheath has an increase compared with the steady state, which is the transient ground current.

The transient ground current signal is received by the high-frequency sensor 3, and the number of transient ground current occurrences is counted to provide early warning for power cable insulation faults. According to our production practice, there are three types of early warning: 1) Yellow early warning: when the cable is abnormal Finally, the utility model collects the transient current signal in the first time and appears in a yellow warning state, indicating that the power cable has arcing phenomenon, and should be closely watched; 2) Orange warning: when dozens of transients are detected every day When the current signal occurs, the utility model will give an alarm in the form of an orange warning, reminding maintenance personnel to arrange maintenance as soon as possible; The user should carry out power-off maintenance immediately.

During the daily inspection of power cable lines, when inspectors inspect the power cable lines, they only need to focus on checking the connection joints of each section of power cables to avoid poor quality joints, loose crimped joints, excessive contact resistance, and external shocks, etc. External faults, corresponding to the defects of the power cable itself, are monitored by the utility model power cable insulation fault online warning and positioning system. Set a high-frequency sensor 3 on the grounding wire of each section of power cable, and connect it to the wave reflection fault locator 4 through the signal line. The fault locator 4 is in working condition.

When there are defects, micropores and moisture in the main insulation of the cable, due to the distortion of the electric field at the defects or micropores, under the action of the electric field, the phenomenon of water tree aging occurs. With the growth of water trees, the electric field at the tip of water trees will become more concentrated, and the local high electric field intensity will eventually lead to electric trees at the tip of water trees, which will lead to the breakdown of the main insulation of the cable. When the water branches cause the main insulation breakdown of the cable, an arc will be generated, which will cause the water vapor to evaporate and dry. Therefore, when the arc is extinguished, the main insulation of the cable will return to the level that can withstand the normal operating voltage.

The utility model reminds monitoring personnel to pay attention to line safety according to the above-mentioned early warning method, and arranges maintenance work early.

The utility model is simple in structure and safe in use. It monitors the grounding current signal on the grounding wire of the power cable through a non-contact high-frequency sensor, and then monitors the insulation fault of the power cable. The wave reflection fault locator only sends a signal to the host computer through the GPRS communication module when the wave reflection fault locator detects high-frequency transient traveling waves, which reduces the signal processing pressure of the host computer. The utility model monitors the operation status of the power cable in real time, and sets early warning information according to the number of monitored electrical signals, which helps electric power maintenance personnel to prepare for maintenance in advance or shorten the maintenance time when they arrive at the maintenance site. The utility model monitors the insulation state of the high-voltage cable under the operating voltage, analyzes the steady state and transient characteristics of the grounding induction current signal of the power cable in real time, judges the change trend of the insulation state, and needs to find dangerous signs from the change trend. The results can be used to comprehensively judge the operation status of the cable, to discover the hidden danger of the insulation failure of the power cable in advance and to give a timely warning, and to accurately locate the location of the fault point within an error range of about 2m, which greatly improves the efficiency of maintenance.

Claims (4)

1. A power cable insulation fault on-line early warning and location system comprises a wave reflection fault locator, a GPRS communication module, a high-frequency sensor, a ground wire, an upper computer and a display, and is characterized in that: Grounding wire, the metal sheath that comes with the power cable, one end is directly grounded, and the other end is grounded through a gap; The high-frequency sensor adopts the open coil method, and is hung on the grounding wire of each section of power cable through the coil; The wave reflection fault locator connects the high-frequency sensor through the signal line, records the electrical signal received by the high-frequency sensor, and locates the fault point; The GPRS communication module sends the electrical signal data recorded by the wave reflection fault locator and the location data of the fault point to the host computer through wireless signals; The upper computer receives the electrical signal data sent by the GPRS communication module and the location data of the fault point; The display shows the electrical signal diagram received by the upper computer and the location data of the fault point. 2. The online warning and location system for power cable insulation faults as claimed in claim 1, wherein said wave reflection fault locator is HDTDR-80 wave reflection method cable fault locator, PMDJ-102A cable terminal or TWPD -2622 digital partial discharge detector. 3. The power cable insulation fault on-line early warning and location system as claimed in claim 1 or 2, is characterized in that, also comprises counter, respectively records the electric signal times that the wave reflection fault locator of every section power cable monitors, and according to The number of electrical signals monitored within the set time period sends out corresponding early warning information. 4. The on-line early warning and location system for power cable insulation faults according to claim 3, further comprising an alarm device, which sends an alarm prompt upon receiving the early warning signal sent by the counter.