TRANSMISSION LINES DESIGN and ELECTRICAL ENGINEERING HUB

For thousands of years, the nature of electricity puzzled and mystified some of the most brilliant minds. It wasn’t until scientists such as Benjamin Franklin, André-Marie Ampère, Alessandro Volta, and Michael Faraday contributed to our understanding of electricity that we began to unlock its secrets. Step by step, bit by bit, we built a plausible model of electricity that fits a mathematical model and provides a real-world explanation of this phenomenon. Even after we had a basic understanding of the key relationships and the fundamentals of electricity, early pioneers such as Joseph Swan, Thomas Edison, Nikola Tesla, and George Westinghouse still struggled to harness its power for daily use in a safe and efficient manner. During that time — the late 1800s and early 1900s — one of the first practical uses of electricity was to illuminate common areas such as city streets and town squares. New York City quickly became entangled — quite literally — in electrical wires and electr...

Make no mistake about it: electricity can kill. It takes as little as 60 milliamps (a milliamp is one thousandth of an amp) passing through the heart to make it fibrillate and stop, causing death within a few minutes. And that’s not the only way it can kill you. Even if the current doesn’t pass directly through your heart, it can contract the muscles in your chest and asphyxiate you; it can burn you internally; it can damage your brain so much that you can stop breathing. Fortunately, our skin, which happens to be the largest human organ, provides a relatively high amount of resistance when it is dry. It helps protect us as long as we use common sense, like wearing rubber soled boots, wearing gloves, and standing on an insulating carpet or rug. On the other hand, risky behavior like standing barefoot on a concrete floor in a puddle of water is asking for trouble. But the vast majority of fatal accidents involving electricity are not caused by electric shock. They are instea...

The earth is the zero-volt reference for power distribution systems. In North America and other countries it’s called ground, and in Europe, Australia, and other countries it is called earth. Voltage is only meaningful when it is referenced to another point. When a bird lands on a high-voltage wire, it doesn’t get electrocuted because it does not complete a circuit to a zero-voltage reference or to another point in the circuit with a different potential. If the bird happens to straddle the gap between the high-voltage line and the metal transmission tower or another line, sparks will fly. That’s because the voltage needs a reference. We typically take zero volts as the absolute reference for voltage measurement. The exception is when we want to know the voltage drop across a particular component such as a resistor or a transistor. But normally, for example, a 12-volt DC power supply means that the positive terminal is 12 volts higher than a zero-volt reference. When w...

As mentioned previously, the effects of static electricity are of considerable importance in the design, operation, and maintenance of aircraft. This is particularly true because modern airplanes are equipped with radio and other electronic equipment. The pop and crackle of static is familiar to everyone who has listened to a radio receiver when static conditions are prevalent. An airplane in flight picks up static charges because of contact with rain, snow, clouds, dust, and other particles in the air. The charges thus produced in the aircraft structure result in precipitation static (p static). The charges flow about the metal structure of the airplane as they tend to equalize, and if any part of the airplane is partially insulated from another part, the static electricity causes minute sparks as it jumps across the insulated joints. Every spark causes p-static noise in the radio communication equipment and also causes disturbances in other electronic systems. For this ...

Some meters must be constructed with a high degree of sensitivity. The sensitivity is determined by the amount of current required to produce a full-scale deflection of the indicating needle. Very sensitive movements may require as little as 0.00005 amp to produce a full-scale deflection. This value is commonly called 20,000 ohms per volt, because it requires 20,000 ohms to limit the current to 0.00005 amp when an emf of 1 volt is applied. Movements having a sensitivity of 1,000 ohms per volt are commonly used by electricians when the power consumed by the instrument is of no consequence. In electronic work, where very small currents and voltages must be measured, instruments of very high sensitivity are required. Electronic measuring instruments, such as the vacuum-tube voltmeter (vtvm) or the solidstate voltmeter (ssvm), are normally used for the measurement of currents and voltages in electronic circuits. These instruments are designed to isolate the measuring circuit ...