What “Neutral” Means

What “Neutral” Means

The neutral conductor is the conductor that leads back to the center tap of the utility transformer. It is connected to earth at two locations: the utility transformer and the main panel. That is why it is sometimes referred to as the grounded neutral conductor. Its designation is white or a white tape on a black cable. Neutral current is commonly referred to as return current, because once the current passes through the load, the white insulated neutral conductor makes the complete circuit back to the utility transformer. All electrical current must make a complete loop. The current starts at the utility transformer and must therefore return to the transformer; the neutral is simply the return part of that loop.
The neutral cable or wire can kill you just as readily as a “hot” cable. The same current that flows in a hot conductor flows out the neutral. If you place yourself in series within that loop, even on the neutral side, you will be electrocuted.

How Electricity Flows

How Electricity Flows

Wire works much like a garden hose, but instead of conveying water, it conveys electricity from one location to another. When you turn on a hose faucet, water entering from the spigot pushes on water already in the hose, which pushes water out the other end. Electricity flows in much the same way. An electron flows in one end of the wire, which knocks an electron, which in turn knocks another electron, until an electron eventually comes out the other end. The water analogy can be used to describe the other elements of electricity. To get water to flow, we need water pressure. To get electricity to flow, we need electrical pressure. 

Electrical pressure, or voltage, can be provided
from either an electrical utility or a battery. And just as greater water pressure means more water flow, higher voltages provide greater electrical flow. This flow is called “current.” With both water and electricity, the diameter of the hose or wire limits what you get out of it in a given amount of time. This flow restriction is referred to as “resistance.”

Which bulb glows brighter?

Very important question:

Two bulbs of 40W and 60W are connected in series with an AC power supply of 100V. Which bulb will glow brighter and why?
Ans:
1. When connected in series: In a series connection, current flowing across each element is same. So when 40W bulb and 60W bulb are connected in series, same current will flow through them. To find which bulb will glow brighter we need to find the power dissipation across each of them. From the relation
P=(I*I) R
since current is same we can say that power dissipation will be higher for the bulb with higher resistance i.e. 40W bulb.
Hence 40W bulb will glow brighter in series connection.
2. When connected in parallel: In a parallel connection, voltage across each element is same. So when 40W bulb and 60W bulb are connected in parallel, voltage across them will be same (100 V in the given case). To find which bulb will glow brighter we need to find the power dissipation across each of them. From the relation
P=(V*V)/R
since voltage is same we can say that power dissipation will be higher for the bulb with lower resistance i.e. 60W bulb.
Hence 60W bulb will glow brighter in parallel connection.
NOW HOW TO REMEMBER THIS-
***At our homes, loads (such as bulbs) are connected in parallel and you always see that higher rated bulb glows more brightly i.e 100W bulb glows more brightly than 60W bulb or 40W bulb.
***So always remember if bulbs are connected in parallel, the bulb with higher rated power will glow brighter and if they are connected in series, the bulb with lower rated power will glow brighter.

Limit Switches

Limit switches
Trustworthy detection devices
Limit switches are electro-mechanical devices. The contacts are mechanically linked to an actuator. By combining different types of actuators, casings and contacts, our limit switches are perfectly suited to a large variety of applications whatever the environment.

Main benefits

Reliable operations
Visible operations
Each application gets the right limit switch.
Main features

Plastic or metal casing, IP65 or IP67
Able to switch strong current up to 10 A
Mechanical durability up to 10 millions of operations.

Reclosers

MV outdoor vacuum reclosers
Single and three phase reclosers up to 38 kV, 16 kA and 1250 A for outdoor pole mount or substation installation.
Reclosers are predominantly located on the distribution feeder, though as the continuous and interrupting current ratings increase, they are seen in substations, where traditionally a circuit breaker would be located. Reclosers have two basic functions on the distribution system: reliability and overcurrent protection.



Why RECLOSERS?

Increased reliability - the highest creep distance among the recloser poles on the market ensures long-term performance in any environment
Unparalleled performance - the HCEP (Hydrophobic Cycloaliphatic Epoxy) material of the poles provides the best insulation for outdoor use, shedding water and debris, thus reducing the probability of flashovers even in heavily polluted areas
Simple, fast and safe maintenance as all the electronics are in the low voltage unit, eliminating the need for a bucket truck to isolate potentials to service electronics
Easy integration with multiple controller options, including the PCD, RER615, RER620 and SEL-651R, to accommodate any grid modernization application.

Transmission lines

Transmission lines are part of the system that gets the electricity from the power station to your home. The lines that are on poles down your street and that are connected to your house and other premises are referred to as the distribution network and are rarely higher than 11,000 volts. The ones to your house are probably no more than 440 volts. These lines come from a transformer that has an input of 11,000 or 22,000 volts. Some large customers take their electricity direct from the 22,000 network, and others take it at 11,000 volts. These high voltage distribution networks are supplied from transformers that are connected to the transmission system that usually operates at anything between 66,000 and 500,000 volts. These very high voltage lines are usually on large steel towers that run between power stations and large Transformer stations that distribute the power at 11,000 volts, and lower, to the end user.

Antifuse

An Antifuse is an electrical device that performs the opposite function to a fuse. Whereas a fuse starts with a low resistance and is designed to permanently break an electrically conductive path when the current through the circuit exceeds a specified value while an Antifuse starts with a high resistance and is designed to permanently create an electrically conductive path when the voltage across it exceeds a certain value.

It is an electrically programmable two-terminal device with small area and low parasitic resistance and capacitance. Figure below shows the symbolic representation of Untriggered and Controlled Antifuse.

It is a Programmable Chip Technology that creates permanent, conductive paths between transistors.  In contrast to “Blowing Fuses” in the fusible link method, which opens a circuit by breaking the conductive path, the Antifuse method closes the circuit by “growing” a conductive layer via  two metal layers in between a layer of non-conductive, amorphous silicon is sandwiched as shown in figure below. When voltage is applied to this middle layer, the amorphous silicon is turned into poly-silicon, which is conductive. 

A controlled Antifuse can be programmed by using some Chip so that when the Chip issues control command then a high voltage exceeding the limit value of Antifuse is applied and hence it becomes conductive and gives Logical / Boolean 1.

Antifuse – Non conductive when voltage is less than the limit value.

Antifuse – Conductive when voltage across the metal layers is more than the limit value.

For better understanding of Antifuse, I am explaining one use of it.  It is used in Christmas Light / Serial Light.

A Serial Light is connected to the domestic supply voltage. The individual bulbs are not rated for the domestic voltage.  However, as they are connected in series, they are able to withstand and function in the domestic supply voltage.

A series of 48 bulbs of a rating of 2.5 volts can withstand 120 volts. Similarly, a series of 96 lamps can withstand 240 volts.

When one bulb in the series fails, there is a risk of the other lamps not getting the supply as the circuit is open circuited. This is avoided by having an Antifuse below the filament which fuses i.e. becomes conductive when the bulb filament fails.  This happens because the system voltage is applied across the single bulb in this case and hence it becomes conductive.

Once the Antifuse operates and closes the open circuit, the current flows as usual to the remaining bulbs and therefore there is no interruption to the glow of bulbs in Serial Lamps / Christmas Light. It is mostly used to permanently programmed ICs.