Instrumentation interviw quetions

What is seeback effect?
The Seebeck effect is the conversion of temperature differences directly into electricityWhat is peltier effect?
The Peltier effect is the reverse of the Seebeck effect; a creation of a heat difference from an electric voltage.
It occurs when a current is passed through two dissimilar metals (semiconductor n-type and p-type) that are connected to each other at two junctions (Peltier junctions). The current drives a transfer of heat from one junction to the other: one junction cools off while the other heats up; as a result, the effect is often used for thermoelectric cooling
What is thomson effect?
The Thomson effect was predicted and subsequently experimentally observed by Lord Kelvin in 1851. It describes the heating or cooling of a current-carrying conductor with a temperature gradient.
Any current-carrying conductor , with a temperature difference between two points, will either absorb or emit heat, depending on the material.
If a current density J is passed through a homogeneous conductor, heat production per unit volume;

Temperature types
K -CROMEL ALUMEL
E- CROMEL CONSTANTAN
J -IRON CONSTANTAN
N-NOCROSIL NISIL
B-PLATINUM RHODIUM
R-PLATINUM RHODUIM
S-PLATINUM RHODIUM

What is Substation?
facility where transformers lower electricity’s voltage
A collection of equipment for the purpose of raising, lowering and regulating the voltage of electricity
An electrical substation is a subsidiary station of an electricitygeneration, transmission and distribution system where voltage is transformed from high to low or the reverse using transformers. Electric power may flow through several substations between generating plant and consumer, and may be changed in voltage in several steps.
A substation that has a step-up transformer increases the voltage while decreasing the current, while a step-down transformer decreases the voltage while increasing the current for domestic and commercial distribution. The word substation comes from the days before the distribution system became a grid. The first substations were connected to only one power station where the generator was housed, and were subsidiaries of that power station
Substations generally contain one or more transformers, and have switching, protection and control equipment. In a large substation, circuit breakers are used to interrupt any short-circuits or overload currents that may occur on the network. Smaller distribution stations may use recloser circuit breakers or fuses for protection of branch circuits. Substations do not (usually) have generators, although a power plantmay have a substation nearby. A typical substation will contain line termination structures, high-voltage switchgear, one or more power transformers, low voltage switchgear, surge protection, controls, grounding (earthing) system, and metering. Other devices such as power factor correction capacitors and voltage regulators may also be located at a substation.


What is IED?
An Intelligent Electronic Device (IED) is a term used in the electric power industry to describe microprocessor-based controllers of power system equipment, such as circuit breakers, transformers, and capacitor banks.

IEDs receive data from sensors and power equipment, and can issue control commands, such as tripping circuit breakers if they sense voltage, current, or frequency anomalies, or raise/lower voltage levels in order to maintain the desired level. Common types of IEDs include protective relaying devices, load tap changer controllers, circuit breaker controllers, capacitor bank switches, recloser controllers, voltage regulators, etc.
Protection relays being manufactured these days are primarily IEDs. This is because, with the available microprocessor technology a single unit can perform several protective, control, and similar functions.
A typical IED can contain around 5-12 protection functions, 5-8 control functions controlling separate devices, an autoreclose function, self monitoring function, communication functions etc. Hence, they are aptly named as Intelligent Electronic Devices . ABB IED's are very much compatible for IEC61850 protocol. They are tested successfully for interoperability between ABB and SIEMENS Protection Relays.
What is humming?
Electric hum, mains hum, or power line hum is an audible oscillation at the frequency of the mains alternating current, which is usually 50 or 60 hertz depending on the local electric utility configuration . The sound often has heavy harmonic content.
The most common cause of electric hum is magnetostriction, wherein ferromagnetic materials change shape minutely when exposed to magnetic fields. Magnetostrictive electric hum is most often noticed around large linear transformers, particularly when the transformers are handling large amounts of current.

By Manoj