TECHNICAL SEMINAR TOPIC ON UNDERGROUND POWER TRANSMISSION Under The Guidance Of Mrs .N.SHANKER M.Tech Assistant Professor , EEE Department Submitted By Sk.Arif 17C11A0203 Contents 1. Abstract 2. Introduction 3. Underground Transmission 4. Types of Underground Transmission Tables 5. Advantages Of Underground Electric Transmission 6. Disadvantages Of Underground Power Systems 7. Fault Location 8. Conclusion ABSTRACT: The transmission of electrical power can be done overhead rather than underground using different types of transmission cables. These types of electrical power transmissions have their own benefits, pitfalls and also applications where it is frequently used. The selection of method mainly depends on the factors like cost, voltage, safety, application, etc. The overhead power transmission is cheap and the installation process is cheap. Whereas, underground power transmission is expensive and also has many advantages. The applications of this transmission mainly depend on the crowd areas as well as where the possibility of overhead power transmission is not possible. Sometimes, due to factors like physical, cost and environmental, the two types of cables are combined together for electrical power transmission This Technical Seminar topic discusses an overview of underground electric power transmission, types, installation, features and more. INTRODUCTION TO UNDERGROUND TRANSMISSION The electric power transmission can be done using a method like undergrounding as an alternative to overhead power transmission. These cables have low visibility and not affected by bad -weather. But, the cost of these cables is high and laying process is time-consuming instead of overhead building. The finding of faults in underground transmission lines takes much time for repairing as well as locating. In urban areas, this type of transmission is enclosed with shielded with dielectric liquid and a metal pipe that is either fixed or spread through pumps. If an electric-fault breaks the underground pipe & generates a dielectric liquid into the nearby mud, then the liquid nitrogen trucks are assembled to fix the damaged part of the pipe location. This kind of transmission cable can extend the fixed period as well as the cost of repair. The stats of the pipe and soil are monitored frequently throughout the period of repair TYPES OF UNDERGROUND TRANSMISSION CABLES The most common types of underground electric power transmission cables include the following. HPFF (High-Pressure Fluid Filled Pipe) HPGF (High-Pressure Gas Filled Pipe) SCFF (Self Contained Fluid Filled) XLPE (Solid Cable Cross-Linked Polyethylene) High-Pressure, Fluid-Filled Pipe-Type Cable: A high-pressure, fluid-filled (HPFF) pipe-type of underground transmission line, consists of a steel pipe that contains three high-voltage conductors. Figure illustrates a typical HPFF pipe-type cable. Each conductor is made of copper or aluminum; insulated with high-quality, oil-impregnated kraft paper insulation; and covered with metal shielding (usually lead) and skid wires (for protection during construction). Figure HPFF or HPGF Pipe-Type Cross Section HPFF or HPGF Pipe-Type Cross Section The outer steel pipe protects the conductors from mechanical damage, water infiltration, and minimizes the potential for oil leaks. The pipe is protected from the chemical and electrical environment of the soil by means of a coating and cathodic protection. Problems associated with HPFF pipe-type underground transmission lines include maintenance issues and possible contamination of surrounding soils and groundwater due to leaking oil. High-Pressure, Gas-Filled Pipe-Type Cable: The high-pressure, gas-filled (HPGF) pipe-type of underground transmission line is a variation of the HPFF pipe-type, described above. Instead of a dielectric oil, pressurized nitrogen gas is used to insulate the conductors. Nitrogen gas is less effective than dielectric fluids at suppressing electrical discharges and cooling. To compensate for this, the conductors’ insulation is about 20 percent thicker than the insulation in fluid-filled pipes. Thicker insulation and a warmer pipe reduce the amount of current the line can safely and efficiently carry. In case of a leak or break in the cable system, the nitrogen gas is easier to deal with than the dielectric oil in the surrounding environment. Self-Contained, Fluid-Filled Pipe-Type: The self-contained, fluid-filled (SCFF) pipe-type of underground transmission is often used for underwater transmission construction. The conductors are hollow and filled with an insulating fluid that is pressurized to 25 to 50 psi. In addition, the three cables are independent of each other. They are not placed together in a pipe. Each cable consists of a fluid-filled conductor insulated with high-quality kraft paper and protected by a lead-bronze or aluminum sheath and a plastic jacket. The fluid reduces the chance of electrical discharge and line failure. The sheath helps pressurize the conductor’s fluid and the plastic jacket keeps the water out. This type of construction reduces the risk of a total failure, but the construction costs are much higher than the single pipe used to construct the HPFF or HPGF systems. Solid Cable, Cross-Linked Polyethylene: The cross-linked polyethylene (XLPE) underground transmission line is often called solid di-electric cable. The solid dielectric material replaces the pressurized liquid or gas of the pipe-type cables. XLPE cable has become the national standard for underground electric transmission lines less than 200 kV. There is less maintenance with the solid cable, but impending insulation failures are much 4 more difficult to monitor and detect. The diameter of the XLPE cables increase with voltage XLPE Cable Cross-Section For 345 kV XLPE construction, two sets of three cables (six cables) are necessary for a number of reasons, primarily so that the capacity of the underground system matches the capacity of the overhead line. This design aids in limiting the scope of any cable failure and shortens restoration time in an emergency situation. Most underground transmission requires increased down time for the repair of operating problems or maintenance issues compared to overhead lines. The double Cross-linked Polyethylene Insulation Segmental Copper Conductor and Shield Outer Coverings 5 sets of cables allows for the rerouting of the power through the backup cable set, reducing the down time but increases the construction footprint of the line. ADVANTAGES OF UNDERGROUND ELECTRIC TRANSMISSION Safe Operation Good General Appearance Prone to Environmental Hazards Less Maintenance Cost Less Fault Occurrence Less Voltage Drop Disadvantages of Underground Power systems High Capital Cost Can’t Use for High Voltage Levels FAULT LOCATION Distance Fault Detection : Underground cables are prone to a wide variety of faults due to underground conditions, wear and tear, rodents etc. Also detecting fault source is difficult and entire line is to be dug in order to check entire line and fix faults. So here we propose an cable fault detection over IOT that detects the exact fault position over IOT that makes repairing work very easy. The repairmen know exactly which part has fault and only that area is to be dug to detect the fault source. This saves a lot of time, money and efforts and also allows to service underground cables faster. We use IOT technology that allows the authorities to monitor and check faults over internet. The system detects fault with the help of potential divider network laid across the cable. Fault Locater using arduino micro controller We can provide used power to the arduino board that is the 12V dc supply will passing though the board But we are using relay to sense the fault. The relay is working 12V.dc so we have to use adopter. The power will passing through arduino board to relay board. The relay is having some sound because relay is shifting one line to another line. We have 3-lines i.e. RYB. These switches are in this direction there is no fault. It any switch is in reverse direction in the place fault occurs. The distance network one switch to another switch is we have taken 3km to each. It a fault occurs in any line is at any distance that will be displayed CONCLUSION The underground cables are convenient for distributing power in urban and other areas where overhead cables may be not be possible. To ensure safety and service continuity, the underground power cabling systems must be protected against both fault conditions as well as physical damage. A proper protection indicates the presence of underground power cables, prevents physical damage to the cable, minimizes supply interruptions and reduces the risks of accidents and personal injury.