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 and automation equipment vendors continue to support it in new products. Although new analyzers, flowmeters …
Special considerations when selecting transformer protection
Current Transformers 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 engineering a dependable and secure protection scheme for the transformer. Errors resulting from …
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) 3. Criteria Starting and running voltage drops in cable 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) within the specified limit so that …
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 able to determine the product (multiplication) of instantaneous voltage and current. Fortunately, the common electrodynamometer movement with …
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 ITs are used: metering (for energy billing and transaction purposes); protection control (for system protection …
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) 2. Criteria-2 Continuous current capacity (Ampacity) 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 is defined as the current in amperes a conductor …
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: This criteria is applied to determine the minimum cross section area of the cable, so that cable can withstand the short circuit current. Failure to check the conductor size for short-circuit heating could result in permanent damage to the cable …
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 be stressed by high transient voltages when a lightning stroke hits the nearby ground. An …
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 current transformer, the reading will be displayed. Whereas a DC clamp meter is quite different. …
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. 1. Single Bus Configuration This arrangement involves one main bus with all circuits connected directly to the bus. The reliability of this type …
