Ac Voltage Indicator Buying Guide

Ac Voltage Indicator Buying Guide

2021-10-23
NOYAFA
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SHENZHEN NOYAFA ELECTRONIC CO.,LIMITED has made a lot of effort in differentiating its ac voltage indicator from competitors. Through continually perfecting the materials selection system, only the finest and most appropriate materials are applied to manufacture the product. Our innovative R&D team has made achievement in enhancing the aesthetic appearance and functionality of the product. The product is popular in the global market and believed to have a wider market application in the future.To make NOYAFA an influential global brand, we put our customers at the heart of everything we do, and we look to the industry to ensure that we are better placed to meet the changing needs of customers around the globe, both today and in the future.In this customer-oriented society, we always focus on the quality of customer service. At Best Cable Tester Supplier in China _ Noyafa, we make samples of ac voltage indicator and other products with extreme care, relieving the worries of customers about our quality. To satisfy various needs of customers, we are also dedicated to customizing the products with innovative spirits to make them more competitive in the market.
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Cable Tracker, Cable Management Software for Residential Homeowners
Cable Tracker, Cable Management Software for Residential Homeowners
Cable Tracker Software is a free software that allows you to track and control your cable network.It allows you to monitor incoming and outgoing cable signals and send email alerts when a signal goes down or up. You can also use it to manage your cables remotely, do security checks on them, as well as get updates on their status.The automated cable tracker can save you time by identifying all the cables that go to your property or business and follow them to determine the source of the power.Cable Tracker Software is the most popular software for monitoring your cable TV service. With Cable Tracker you can quickly and easily view your subscription history, watch TV shows, get alerts when new episodes of your favorite shows are on demand, set reminders to watch a show or go back to some other channel.It is a piece of software that tracks all the TV& cable channels for subscribers and shows the complete list of all channels in a user's reach.Cable Tracker Software is an office product that allows users to manage all their cable connections and subscriptions.Cable Tracker Software is a professional software for TV/Cable network data analysis. It detects the end-user channel usage and compares it to the cable's own data. It can also provide a report on the advertising commission paid to each of these channels.This section is dedicated to the latest technology that has been adopted in the industry.Choosing the right cable company is one of the most important decisions you can make. If you're going to buy your cable service, make sure that the options are in line with what is best for your needs.Cable Tracker for Residential and Business provides a number of different options to choose from and filters them according to features, price and package. The idea is simple: if you can't decide which option will be best for your needs, Cable Tracker should help you by giving an overview of all possible alternatives.The cable tracker is one of the best-selling digital video recorder products in the market. The device allows users to record all kinds of properties, such as homes, offices and shopping centers. This device has several benefits:We should not think of these devices as an alternative to traditional video recorder solutions. Instead they are a complementary tool that provides more features to enable better recording and longer recording times for a fixed price.Cable Tracker is an innovative, multi-dimensional tool that enables cable companies to monitor and track all the homes and businesses in their networks. Once installed, it provides data on subscribers, company owned IP address and IP port numbers, cable companies’ technical data such as fiber optic cables and access points, IP address for each customer’s account manager (AMR), etc. Also keeps track of numerous other details such as current/past billing cycle dates, internet traffic measurements (download/upload speeds), weather app usage (solar panel usage), etc.Cable Tracker Software is a tool for tracking and monitoring the internet cable TV network usage.In this chapter, we will get acquainted with the term “Cable Tracker”. The purpose of this software is to be a complete solution for creating content for cable channels and digital video distribution systems.This software can generate content templates in order to save time when creating content for various types of cable channels or other digital video distribution systems. It also allows you to make changes to the template before submitting it to your client.The "Cable Tracker" is a list of cable providers' basic cable packages. It has been used by millions of people all over the world and has been a best-seller for many weeks.Cable Tracker is a service that helps you find cable TV, broadband and voice services at any time.This is a section that I thought would be useful for readers. It's the one thing that if you are a content writer you will never forget. It’s the most important thing to keep in mind while writing your articles.Cable Tracker is a real-time tracking and monitoring tool that enables users to monitor their cable TV subscriptions, VOD services and internet usage.Note: Cable Tracker is developed by Esri. Esri provides using built-in tools to manage residential and business customers' cable TV, internet, telephone etc. usage with a single interface in the cloud.Section: Media personals for children in the 21st centuryIntroduction: In this section we will discuss the different ways in which children are trying to find their way into the media industry. We will discuss how they are using social media platforms like Facebook and Twitter, and Snapchat as well as traditional ways of finding jobs like news agencies or newspapers online. We will see how technology has helped them in terms of searching jobs but also how it has helped
How to Pay for Lc/sc/fc/st Fiber Optic Cable Tester for Troubleshooting?
How to Pay for Lc/sc/fc/st Fiber Optic Cable Tester for Troubleshooting?
At NOYAFA, we support the idea of customers arranging the lc/sc/fc/st fiber optic cable tester for troubleshooting shipment by yourselves or by your assigned agents. If you have been working with the assigned freight forwarders for years and totally trust them, it is advisable that your goods can be entrusted to them. However, please know that once we deliver the products to your agents, all the risks and responsibilities during the cargo transit will be transferred to your agents. If some accidents, such as bad weather and poor transportation condition, lead to cargo damage, we are not responsible for that.With over lc/sc/fc/st fiber optic cable tester for troubleshooting years of experience servicing lc/sc/fc/st fiber optic cable tester for troubleshooting, we take pride in making sure your investment is protected and performing optimally at all times. With carefully selected materials, our lc/sc/fc/st fiber optic cable tester for troubleshooting have received much fame until now. lc/sc/fc/st fiber optic cable tester for troubleshooting's high performance can meet the requirements of many special industries for lc/sc/fc/st fiber optic cable tester for troubleshooting.Once you try us, we're sure you'll be back for more! Get more info!· Related Questions:1. May NOYAFA offer warehousing services?NOYAFA, as one of the strongest enterprises among similar competitors, holds a completed and fine warehousing service system. We pay attention to the customers’ requirements and communication with our staff working in the warehousing services department. We have a complete infrastructure construction in the warehouse and reasonable warehouse space allocation and efficient utilization rate of warehouse space, which can benefit the administrator to store the products. And all those can ensure that we can provide an extraordinary experience for our customers, and this kind of service can also build our company’s brand. ——————— 2. Can our logo or company name be printed on lc/sc/fc/st fiber optic cable tester for troubleshooting?The customized logo is available for lc/sc/fc/st fiber optic cable tester for troubleshooting. We offer professional design and creation of high-quality products and personalized ideas. We'll affirm the layout with you before manufacturing. ——————— 3. What kind of packing is provided for lc/sc/fc/st fiber optic cable tester for troubleshooting?NOYAFA has some general packaging guidelines that will help you prepare your package for shipping. Please consult our Customer Service for detailed information. We ensure the package we choose is the most suitable for your items. We are passionate about our service, and we take the responsibility for what we pack very seriously. ——————— 4. What are NOYAFA shipping modes?At NOYAFA, there are numerous options for delivering lc/sc/fc/st fiber optic cable tester for troubleshooting. When determining the form of transportation, the cost, the urgency of the shipment, the value of the goods being shipped as well as the volume and weight of the goods need to be evaluated. Air freight is a critical mode of transport. It serves markets and supply chains that demand speed. Land shipping, probably one of the earliest forms of transporting cargo, can transport goods of almost any size. Rails and trucks are usually the vehicles used to transport the goods. Ocean freight is less expensive and the most popular method of shipping goods. It is suitable for a wide range of products with long lead times. We will prioritize your needs and choose the best method of transport.
A Brief Guide to Selecting Cable Length Testers
A Brief Guide to Selecting Cable Length Testers
The LinkRunner LTRA offers a variety of cable testing techniques, including TDR, wiremapping, office identification and toning. The LTRA is designed to help troubleshoot wiring problems such as excessive cable routing, cable breaks, wall panels, patch panels, etc. It uses a combination of TDR and resistance measurements to map the wire, measure cable length and detect anomalies such as short, open or split pairs.The LRAT can measure an accurate cable length of 100 m or less with an accuracy of plus or minus 2 m. It can also be used to test terminated cables connected to an internal cable mapping port (WMAP) or an external cable identification accessory, as well as undermined and open cables. For pre-assembled and non-assembled cables, the fault detection is accurate to within 0.8 m of the error distance.This tester is a wiremapper that checks connections for CAT 5E / 6 certification, but can also test performance at higher frequencies. The threshold for the low voltage resistance is set insulated for 5 mO to a contact resistance of 0.1 O. This is measured with an embedded resistance at 100 O (1 mO x 1) to achieve an accuracy of less than -0.1 o (5 mO).In fact, certification testers can test wire diagrams, length attenuation, and crosstalk from one connection to another, helping you troubleshoot and save the results in a printed report for the customer. Cable certification testers are automated, so it's so easy to get a pass or fail at the touch of a button. Installers use certification testers to test cables that are being laid.There are a large number of cable testers on the market today, which means that there may be the right device for your purposes. To help you find the best network cable tester for your use I have compiled a list of test products that work well. As someone with extensive experience as an electrician, I can say that the Elegiant Network Cable Tester is the best tool for testing cable connections.I came across the Elegiant Network Cable Tester while working on establishing a LAN connection for a local company. As a consumer, I used the handheld network cable tester with RJ11, RJ12, RJ45 for the Cat 3 types Cat 5E, Cat 6 and Cat 6A. The broad compatibility of the device does not complicate your work in the analysis of cable connections.Cable Prowler (tm) provides complete cable testing for all categories of network, coaxial and telephone cables. Selecting, selecting and purchasing a suitable network cable tester is a complicated and challenging task. Purchasing the right network cable tester can save you a lot of inconvenience and trouble.Includes low-voltage and high-voltage subsystems, HVX-compliant automation, enabling extended testing of insulation resistance, dielectric breakthrough, Zener diode breakthrough, voltage upgrade, 4-wire measurements, and advanced measurements. With the changing landscape of corporate cabling, there is a demand for testing equipment you can rely on. Hopefully this article has helped you choose the best network cable tester for your profession and field of work.Advanced measurement options provide increased x5 / 2 wire resistance resolution for backplane, complex networks, capacitors, wire pairs, capacitors, twist pairs, and cable length testing. Copper remains the first choice for telephone data and video lines. Integrated Intellitone digital / analog tones are located on the cable or wire pair in the active network.It is an expensive device that requires trained operators and many failures due to problems with the wirecard. Other crews use low-cost cable ties to ensure the connections are correct before the certification tester is turned on. Instead of letting the crew find and fix their own wiremap problems, tests and fixes can be made before the cable is installed, and tester costs are not wasted on simple problems.
How Can Screwdriver Organizers Help DIY Technicians?
How Can Screwdriver Organizers Help DIY Technicians?
Most technicians love to spend their time in their workshops. And for them, their screwdrivers are of utmost importance. It is hard to complete any task when you dont have high-quality screwdrivers handy. Screwdrivers are available in a number of sizes and just having them is not enough. You must also take care of them if you want them to last long. Make sure that you keep them safe and secure at all times. What can be better than modular screwdriver organizers to keep your screwdrivers safe, secure, handy, and organized?All your screwdrivers are in one place but still disorganized. You might face this every single day. And this might be resulting in you wasting a lot of time on finding the right sized screwdriver when you are on a job. What can be worse than this is losing some of them! Being a technician, you can afford any of these situations. It is important that you make sure that all your screwdrivers are handy and safe whenever you need them.How to find Suitable Screwdriver Organizers?There can be any reason why you need to buy a screwdriver organizer. A screwdriver organizer comes as a savior for you. It offers a convenient storage solution so that you can keep your screwdrivers in place without any hassle. And that also means that you dont have to worry about losing them again. The best part about investing in good-quality screwdriver organizers is that they allow quick search so that you dont have to waste your time. Why do you need to buy a Screwdriver Organizer?It is not just your screwdrivers that the toolbox organizer will hold. It will also help you in keeping your other precious tools in place. This way you will able to easily find your tools and keep them back in place after use. The screwdriver organizers come with spaces where you can place the screwdrivers easily. With modular screwdriver organizers, you get enough space to keep your long, short, stubby, and every type of screwdriver.Such organizers are not less than a blessing for DIY technicians who have to work using their tools on a daily basis and also for the people who like to do little tasks of their homes on their own. When you have screwdriver organizers, you will be able to save your screwdrivers from scratches and other harms. As the toolbox organizers come with strong magnets, your tools will never be misplaced. You will always them where they were kept. If you are in search of high-quality modular screwdriver organizers, look no further and visit the official website of Toolbox Widget, We have toolbox organizers for all your tools. While you will keep your tools in a toolbox, it is advised that you clean them properly and apply light oil on your tools before keeping them. To find out more about the toolbox organizers that we have in our inventory, give our official website a visit.
Brief Introduction of Tester for High Voltage Cable Fault
Brief Introduction of Tester for High Voltage Cable Fault
Brief introduction to high voltage cable fault tester product nickname: cable fault tester, high voltage cable fault tester, cable fault tester, point tester, path tester, cable fault Pathfinder, cable fault tracker, portable cable fault location system, cable fault flash tester, cable fault point tester, cable path tester, working principle of high voltage cable fault tester, Smooth wired communication and power transmission depend on the normal operation of cable lines. Once the line is blocked, it will cause the communication to find out the fault in time and eliminate it quickly, which will cause great economic losses and poor social impact. Therefore, the cable fault tester is an important tool to maintain all kinds of cables. The cable fault intelligent tester adopts a variety of fault detection methods, applies contemporary * advanced electronic technology achievements and devices, adopts computer technology and special electronic technology, and combines the company's long-term successful experience in developing cable tester. It is a new high-tech, intelligent and fully functional product. Dear customers: the company also has power cable fault tester, cable fault locator and cable fault tester products. You can call the company's service phone through the web page to learn more product details. Perfect and beautiful service is our pursuit. New and old customers are welcome to buy their favorite products at ease. We will serve you wholeheartedly!
Characteristics and Principle of Cable Fault Locator
Characteristics and Principle of Cable Fault Locator
Cable fault locator is a comprehensive cable fault detection instrument, which can test the faults such as high resistance flashover fault, high and low resistance grounding, short circuit, cable disconnection and poor contact. The cable fault locator is equipped with an acoustic pointing instrument, which can be used to accurately determine the * * position of the fault point. It is especially suitable for testing power cables and communication cables of various models and different levels of voltage. Adopt a variety of detection methods and apply contemporary * advanced electronic technology achievements. Using computer technology and microelectronics technology, it has the characteristics of high intelligence, complete functions, wide range of use, accurate test, convenient use and so on. The host of the cable fault tester is used to measure the nature and total length of the cable fault and the approximate position between the cable fault point and the test end. The cable fault locator determines the * * position of the cable fault point based on the approximate position of the cable fault point determined by the host of the cable fault tester. For buried cables with unknown direction, a pathfinder shall be used to determine the underground direction of the cable. The basic method of power cable fault test is to apply high-voltage pulse to the fault power cable to produce breakdown at the cable fault point. When the cable fault breakdown point discharges, it generates electromagnetic wave and sound at the same time. Dear customers: the company also has cable fault detector, buried cable fault detector and underground pipeline detector products. You can call the company's service phone through the web page to learn more product details. Perfect service is our pursuit. New and old customers are welcome to buy their favorite products at ease. We will serve you wholeheartedly!
What Is a Cable Pricker
What Is a Cable Pricker
Cable stabbing device Preface: according to the relevant safety work regulations of the power industry, manual stabbing is unsafe and will cause personal injury in case of error. In order to solve this problem, we have made a cable identification instrument and safety stabbing device, which can identify and stab the cable when it is impossible to judge whether the cable is charged at the construction site. The high-voltage cable safety stabbing device is divided into single gun and double gun. The main difference is that one can stab at one angle or two angles, and adopts non-contact control (remote control and timing). The instrument and provides power supply. The battery can be isolated from the power system to ensure the safety of the power system. At the same time, people can also stand at a far position and stab completely through remote control. Disassembly of cable stabbing device: where the final removal work needs attention after each test is completed, each stabbing shall be completed once. The voltage level electroscope corresponding to the power supply cable shall be used to confirm that the bound cable and equipment are dead, and then the stabbing device can be removed or stabbed at another angle. A cable must be pricked in two to three directions. After that, remove the pricker and finally remove the grounding wire. After pricking, use the equipped through needle to push the piston rod in the barrel back into the bottom of the barrel, and wipe and maintain the device for reuse. Safety of cable stabbing device: 1. Electronic control ensures that even if the device power is turned on and the "confirm" key is pressed by mistake to enter the selected mode, it is necessary to conduct secondary confirmation or mode selection again; The device will not act automatically because it enters the timing mode by mistake. A second confirmation is required to enter the selected mode. 2. The electronic control ensures that even if the power supply of the device is turned on and a key of the remote controller is pressed by mistake, the device will not act. The device will not act until the C and D keys on the remote controller are pressed at the same time. 3. The electronic control ensures that the device will not operate until you press the C and D keys of the remote control at the same time after prompting to stay away from the site. 4. In the timing mode, the remote controller does not work, and there will be no misoperation caused by mispressing the remote controller. Through the above understanding.. I believe you have a more detailed understanding and understanding of what the cable pricker is. If you have any questions, please feel free to discuss it at any time.
How to Contact Your After-sale Service Division?
How to Contact Your After-sale Service Division?
This will be emailed to you once the 4 in 1 cable tester are delivered. Tracking info will be attached so that you can follow the logistics. Any questions can be asked after the delivery.SHENZHEN NOYAFA ELECTRONIC CO.,LIMITED concentrates on developing high-quality products such as 4 in 1 cable tester and 4 in 1 cable tester. At the same time, it also guarantees the upgrade and maintaince of 4 in 1 cable tester. We have successfully applied for patents of technology for 4 in 1 cable tester.We are there to support you with our dedicated, highly trained staff. Inquire now!· Related Questions:1. What services are offered for 4 in 1 cable tester?NOYAFA's services don't restrict to supplying 4 in 1 cable tester. Customer support is available to requirements. One of our key values is that we never leave customers alone. We promise we'll take good care. Let's find out together the correct solution for your problem! ——————— 2. Does NOYAFA have forwarder?At NOYAFA, we work closely with logistics partners so that we can deliver your products promptly. We have built stable partnerships with reliable and experienced logistics companies. Whether it is sea freight or air transport, we can meet your requirements and ensure the accurate, safe, and on-time delivery of your products. Our long-term cooperation relationships with logistics companies also allow us to get more favorable freight. Of course, if you have your own freight forwarder, we can deliver the products to the designated location. ——————— 3. How about NOYAFA shipping services?NOYAFA renders professional shipping services. We have co-operated with reliable and experienced third-party-logistics companies to handle the shipping of our global business. And inside our company, we have established a mature shipment management system. Before the shipment, we carefully treat not only the printing of packing and shipping slips but also the various sizes of boxes or packages to avoid any shipping damage. More importantly, we always make sufficient communication with customers as to how their packages were shipped and when to expect it. ——————— 4. What are NOYAFA shipping modes?The mode of transportation is an important consideration when planning the shipment process. NOYAFA provides several shipping methods for customers by working with several international logistics companies. In the current market, there are mainly three kinds of transportation modes which are respectively air freight, ocean freight, and rail/road freight. You may choose any of the three different modes of transport depending on several factors such as budget, time, and types of goods being transported. Normally, shipping by sea has been practiced for thousands of years and remains pivotal to today's global trade. 90% of all international trade is accomplished through maritime transportation. However, if the order is urgent, you may choose air freight which may cost more.
Cable Fault Detection and Search Method
Cable Fault Detection and Search Method
For direct short circuit or broken cable fault, the multimeter can be used for direct measurement and judgment; For indirect short-circuit cable fault and grounding cable fault, use a megger to telemeter the insulation resistance between core wires or the insulation resistance between core wires and ground, and judge the cable fault type according to its resistance value. The following describes the method of cable fault finding: zero potential method. Zero potential method is also known as potential comparison method. It is suitable for short cable core to ground fault. This method is simple and accurate, and does not need precision instruments and complex calculation. The measurement principle is as follows: connect the cable fault core wire in parallel with the comparison wire of the same length. When applying voltage ve at both ends of B and C, it is equivalent to connecting the power supply at both ends of two parallel uniform resistance wires. At this time, the potential difference between any point on one resistance wire and the corresponding point on the other resistance wire must be zero. On the contrary, the two points with zero potential difference must be the corresponding points. Because the negative pole of the micro voltmeter is grounded and equipotential with the cable fault point, when the positive pole of the micro voltmeter moves to the point when the indicated value is zero on the comparison wire, it is equipotential with the cable fault point, that is, the corresponding point of the cable fault point. S refers to single-phase knife switch, e refers to 6e battery or 4 No. 1 dry batteries, and G refers to DC microvolt meter. The measurement steps are as follows: 1) connect battery E on phase B and C core lines, and then lay a comparison conductor s with the same length as the fault cable on the ground. The conductor shall be bare copper wire or bare aluminum wire, with equal cross section and no intermediate joint. 2) The negative pole of the micro voltmeter shall be grounded, and the positive pole shall be connected with a long flexible conductor. The other end of the conductor shall be fully contacted when sliding on the laid comparison conductor. 3) Close the knife switch s, slide the end of the flexible conductor on the comparison conductor, and the position when the microvolt meter indicates zero is the position of the cable fault point. High voltage bridge method high voltage bridge method is to measure the DC resistance of cable core with double arm bridge, then accurately measure the actual length of cable, and calculate the cable fault point according to the positive proportional relationship between cable length and resistance. For direct short circuit between cable cores or short circuit point, the contact resistance is less than 1 & omega; The judgment error is generally not greater than 3m, and the contact resistance at the fault point is greater than 1 & omega; The resistance can be reduced to 1 & Omega by increasing the voltage and burning through; Next, measure according to this method. When measuring the circuit, first measure the resistance R1 between core wires a and B, R1 = 2RX R, where Rx is the phase resistance value from phase a or phase B to the cable fault point, which is only the contact resistance of the short contact. Then move the bridge to the other end of the cable and measure the DC resistance R2 between A1 and B1 core wires, then R2 = 2R (l-x) r, and R (l-x) is the phase resistance from A1 phase or B1 phase core wire to the cable fault point. After measuring R1 and R2, short circuit B1 and C1 according to the circuit shown in Figure 3, and measure the DC resistance value between B and C core wires, then 1 / 2 of the organization is the resistance value of each phase core wire, expressed by RL, RL = RX R (l-x), from which the contact resistance value of the fault point can be obtained: r = R1, r2-2rl table. Therefore, the resistance value of the core wires on both sides of the fault point can be expressed by the following formula: RX = (r1-r) / 2, R (l-x) = (r2-r) /2. After the three values of Rx, R (l-x) and RL are determined, the distance X or (l-x) between the fault point and the cable end can be calculated according to the proportional formula: x = (Rx / RL) l, (l-x) = (R (L-2) At the end of the cable, measure the capacitance currents IA1, IB2 and IC3 of the core wire of each phase to check the capacitance ratio between the intact core wire and the broken core wire, and preliminarily judge the approximate point of the broken wire distance. According to the capacitance calculation formula C = I / (2 & PI; Fu), when the positive voltage U and frequency f do not change, C is directly proportional to I. because the frequency of power frequency voltage is f (frequency) Constant, as long as the applied voltage is kept constant during measurement, the ratio of capacitance to current is the ratio of capacitance. If the total length of the cable is l and the distance of the core wire breaking point is x, then IA / ic = L / x, x = (IC / IA) 50. In the process of measurement, as long as the voltage remains unchanged, the reading of ammeter is accurate and the total length of cable is measured accurately, the measurement error is relatively small. The so-called sound measurement method is to find out according to the discharge sound of faulty cable. This method is more effective for the flashover discharge of high-voltage cable core to insulating layer. The equipment used in this method is DC withstand voltage tester. TB is high-voltage test Transformer, C refers to high-voltage capacitor, ve refers to high-voltage rectifier silicon stack, R refers to current limiting resistance, Q refers to discharge ball gap, and l refers to cable core. When capacitor C is charged to a certain voltage value, the ball gap discharges to the cable fault core, and the cable core discharges to the insulating layer at the cable fault, producing a loud and loud spark discharge sound. For open laying cables, it can be found directly by hearing. If it is buried electricity For cable, first determine and mark the cable direction. When searching, put the pickup close to the ground and move slowly along the cable direction. When the sound of Zi and Zi discharge is the largest, this is the cable fault point. Pay attention to safety when using this method, and assign special personnel to monitor at the end of the test equipment and the end of the cable. The cable fault locator produced by our company can not only measure the sound, but also To detect the magnetic signal, the signal strength is displayed visually and synchronously, which can locate the cable fault point faster and more accurately.
Cause Analysis of Insulation Failure of Power Cable
Cause Analysis of Insulation Failure of Power Cable
1. Insulation aging of insulation fault cables mainly occurs in the later stage of operation, generally in cable lines that have operated for 15 years or more, resulting in a significant increase in cable failure rate. Insulation aging is mainly divided into dendritic aging, electrothermal aging and insulation material aging. The air gap inside the cable insulation medium is free under the action of electric field, which reduces the insulation. When the insulation medium is ionized, ozone, nitrate drum and other chemicals are generated in the air gap, which corrodes the insulation layer. At the same time, the moisture in the insulation decomposes the insulation fiber, resulting in the decline of insulation strength. Overheating will accelerate the aging and deterioration of insulation. The electric dissociation generated by the air gap inside the cable insulation will cause local overheating, carbonize the insulating material and reduce the insulation strength. Cable overload is an important factor of cable overheating. Cables installed in poorly ventilated places such as cable dense areas, cable trenches and cable tunnels, cable paths parallel or cross with thermal pipelines without effective thermal insulation measures will overheat the cables and accelerate the damage of the insulation layer. When the cable insulation operates under the action of electricity and heat for a long time, its physical properties will change, resulting in the reduction of insulation strength or the increase of dielectric loss, which will eventually lead to insulation collapse and aging and failure. The main causes of insulation aging are: (1) improper cable selection, resulting in long-term over-voltage operation of the cable; (2) The surrounding of the cable line is close to the heat source, so that part of the cable or the whole cable line is heated for a long time and ages prematurely; (3) The cable is aged prematurely when working in an environment with adverse chemical reaction with insulation; (4) When multiple cables are running in parallel, one or more of them are in poor contact, resulting in overload operation of other cables in parallel; (5) When making cable accessories, the cable connecting pipe is not firmly crimped, resulting in increased contact resistance and overheating. 2. Accessories: the cable intermediate joint and terminal head are usually completed by the installation personnel at the laying site, and mistakes are easy to occur without paying attention. Cable accessory failure accounts for the main part of cable line failure, which is mainly manifested in composite interface discharge and accessory material aging. The failure of cable accessories is often due to the poor manufacturing process and the carelessness of personnel. During the manufacturing process, bubbles, moisture, impurities and other defects appear in the accessories, resulting in partial discharge and insulation breakdown, which is mainly reflected in: (1) the manufacturing quality of cable intermediate joints and terminals is not high; (a) when stripping the outer semiconducting layer, Damage the lower insulation or there is half a track of particles, dust and other impurities on the insulation surface, or the removal distance of the semi conductive layer is short and the creepage distance is not enough. After the test or operation, the impurities are free under the action of strong electric field and produce electric branches. (b) During the manufacturing process, the crimping quality of the metal connecting pipe is poor, resulting in excessive contact resistance and heating of the joint, or excessive thermal shrinkage, resulting in insulation carbonization, aging and breakdown of the insulating layer, resulting in cable grounding or phase to phase short circuit fault, and may damage other nearby cables. (c) The cable joint process is not standard and the sealing is not standard, so that the insulation is invaded by moisture and moisture, resulting in the deterioration of the insulation of the intermediate joint. In serious cases, water enters into a large area inside the main insulation of the cable, resulting in the overall moisture of the main insulation, the insulation is reduced, and finally the cable breakdown fault occurs. (d) The treatment process of conductor connecting pipe is poor. The selection of crimping die for conductor connecting pipe is unreasonable, and the edges and corners are not polished smoothly. Especially at the edge of crimping die, there are sharp corners, burrs and protrusions, which is very easy to cause uneven electric field at this part, partial discharge during operation, aging insulation, degradation of insulation performance and breakdown fault. (e) The installation size is wrong, the installation position of the stress tube is too low, or the stress cone is not effectively overlapped with the half layer fracture, resulting in the failure of reliable stress evacuation at the semi conductive fracture of the cable. During the test or long-term operation, serious corona discharge occurs at the fracture, resulting in overheating, reducing the insulation, and finally leading to breakdown. (f) The connection of the grounding wire of the cable metal shielding layer is unreliable and does not meet the requirements of grounding resistance, resulting in excessive grounding resistance. When the cable is subjected to overvoltage, the metal shielding layer will produce high induced overvoltage, which will lead to aging and breakdown of the insulating part. (2) During operation, the cable expands and contracts due to the change of load and environmental factors, especially the heat shrinkable accessories can not lose the sealing effect with elastic deformation, forming a respiratory effect between the accessories and the cable insulation layer, bringing moisture and moisture in the atmosphere into the accessories, causing the internal short circuit fault of the cable accessories. Poor quality of cold shrinkable accessories, reduced shrinkage or defective sealing at the parts requiring reliable sealing will lead to external moisture intrusion and eventually cable failure. (3) When making the cable head, due to the high environmental moisture and humidity, reliable dehumidification and moisture drive measures were not taken, the cable insulation was partially affected by moisture, the insulation performance decreased, and developed into a penetrating channel during operation, resulting in cable breakdown accident. 3. The problem of outer sheath is more and more widely used in medium and high voltage power grid. The outer sheath of power cable is the first line of defense to protect the cable. Its integrity is directly related to the safety of internal structure and the service life of the cable. There are three main causes of cable outer sheath failure: (1) hard object damage or external force damage around the cable. There are sharp corners of hard objects at the top and bottom of the directly buried cable that directly contact the outer protective layer. Especially in the road section with vehicles, the sharp corners of hard objects may pierce the outer protective layer for a long time, resulting in damage to the internal structure. In addition, with the change of cable load, the thermal expansion and contraction of the cable itself and the uneven distribution of electric field at the damaged parts, resulting in damage to the insulating layer; During pipe laying, the outer protective layer may be damaged if the steps or inner wall at the pipe connection are not smooth; The outer sheath is damaged due to mechanical construction or pipe jacking around the cable path. (2) Defects and hidden dangers left during construction. During the cable laying construction, the damaged and cracked parts of the outer sheath are in the row pipe, and the personnel cannot find them in time; After running for a period of time, the bending part of 110kV and above cables will crack, the insulation of the outer sheath will be reduced, the metal sheath will be grounded at multiple points, and the circulating current will increase, resulting in thermal aging and breakdown of the insulation. (3) Termite decay. Once a termite erosion site is found, there are often multiple erosion sites on the cable line, which should be paid enough attention. Termite erosion is relatively rare in the northern power grid.
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