Power Substation
Transformer Connection Star-Star
The windings of three phase transformers may be connected in by Y or Δ in the same manner as for three single phase transformer. Since the secondary’s may be connected either in Y or Δ regardless of which connection is used on… Read more
May 23, 2012 | By Jignesh Parmar
Industrial Automation
Using MODBUS for Process Control and Automation (1)
MODBUS is the most popular industrial protocol being used today, for good reasons. It is simple, inexpensive, universal and easy to use. Even though MODBUS has been around since the past century nearly 30 years, almost all major industrial instrumentation… Read more
May 21, 2012 | By Edvard Csanyi
Energy and Power
Special considerations when selecting transformer protection
Current transformer ratio selection and performance require special attention when applying transformer protection. Unique factors associated with transformers, including its winding ratios, magnetizing inrush current, and the presence of winding taps or load tap changers, are sources of difficulties in… Read more
May 19, 2012 | By Edvard Csanyi
Cables
Sizing of power cables for circuit breaker controlled feeders (part 3)
Continued from article Sizing of power cables for circuit breaker controlled feeders (part 2) This criterion is applied so that the cross sectional area of the cable is sufficient to keep the voltage drop (due to impedance of cable conductor)… Read more
May 17, 2012 | By Asif Eqbal
Electrical Lectures
Power Measurement In AC Circuits
Power measurement in AC circuits can be quite a bit more complex than with DC circuits for the simple reason that phase shift complicates the matter beyond multiplying voltage by current figures obtained with meters. What is needed is an instrument… Read more
May 15, 2012 | By Edvard Csanyi
Energy and Power
Introduction to instrument transformers
Instrument transformers (ITs) are designed to transform voltage of current from the high values in the transmission and distribution systems to the low values that can be utilized by low voltage metering devices. There are three primary applications for which… Read more
May 14, 2012 | By Edvard Csanyi
Cables
Sizing of power cables for circuit breaker controlled feeders (part 2)
Continued from article Sizing of power cables for circuit breaker controlled feeders (part 1) This criterion is applied so that cross section of the cable can carry the required load current continuously at the designed ambient temperature and laying condition. Ampacity… Read more
May 13, 2012 | By Asif Eqbal
Cables
Sizing of power cables for circuit breaker controlled feeders (part 1)
The following three criteria apply for the sizing of cables for circuit breaker controlled feeders: [fancy_header]I. Short circuit current withstand capacity[/fancy_header] This criteria is applied to determine the minimum cross section area of the cable, so that cable can withstand… Read more
May 10, 2012 | By Asif Eqbal
Energy and Power
Overvoltages Caused by Indirect Lightning Strokes
A direct stroke is defined as a lightning stroke when it hits a shield wire, a tower, or a phase conductor. An insulator string is stressed by very high voltages caused by a direct stroke. An insulator string can also… Read more
May 08, 2012 | By Edvard Csanyi
Metering
An Overview Of Clamp Meter
Clamp-on ammeter or simply ‘clamp meter’ is an instrument that is used to measure the current flowing through a conductor. An AC Clamp meter basically consists of a current transformer in its jaws, bar CT usually. Utilizing the principle of… Read more
May 06, 2012 | By S
Medium Voltage
Bus Switching Configurations In Air Insulated Substations (AIS)
Various factors affect the reliability of a substation, one of which is the arrangement of the switching devices. Arrangement of the switching devices will impact maintenance, protection, initial substation development, and cost. There are six types of substation bus switching… Read more
May 05, 2012 | By Edvard Csanyi
Energy and Power
Using AC and DC together in electrical system?
There are a number of issues to using AC and DC together in the same electrical system. Briefly, they are: circuit boxes and hardware, outlets, wiring schemes and sizes, and switches. The Electrical Code prohibits AC and DC in the same box. You’ll need two… Read more
May 05, 2012 | By Edvard Csanyi
Energy and Power
Types of Residual Current Devices (RCD)
For domestic applications only the first five of the below listed residual current devices (RCD) need to be considered. For industrial and commercial buildings all of the classifications need to be considered. Table below aims to identify where each type… Read more
May 03, 2012 | By Edvard Csanyi
Energy and Power
Time relays setting ranges explained in details
Time relays are used in control switching operations involving time delay. Most of these time relays have multiple time setting ranges and most of them are explained below. Time relays perform either on-delay or off-delay timing. An arrow is used… Read more
Apr 30, 2012 | By Edvard Csanyi
Electric Motor
Measurement of insulation resistance (IR) – Part 2
This article goes into details of insulation resistance values measured by Megger tester on many different kinds of equipment, such as switchgear, electrical wires & cables, electric motors, transmission & distribution lines, and other power system equipment. An insulation tester… Read more
Apr 29, 2012 | By Jignesh Parmar
