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The Rankine Cycle comprises of 4 thermodynamic processes on which the steam engine or turbine is based to convert the heat energy into mechanical work. It is also the ideal vapour cycle which is used for comparing the performance of various power generating plants running on steam. Basic …
The Carnot cycle is the thermodynamic power cycle that was introduced by a French military Engineer, Nicolas Léonard Sadi Carnot in the year 1824 in his work, “reflection on motive power of fire”. It is a theoretical power cycle which is reversible with conserved entropy. Working The Carnot …
Parallel operation of the transformer is a method of operating two or more transformers that are primarily connected to a common source and whose secondary sides cater to a common load such that the load is shared between the connected transformers. Parallel operation of the transformers is considered …
A synchronous condenser is an electrical machine, used in the substations for absorbing or supplying reactive power by controlling the excitation of the machine, thus making the grid stable and also regulate the voltage levels. Working Principle of synchronous condenser The synchronous condenser works like a synchronous motor …
Reactive power, in an AC circuit, is the rate of energy that flows in and out of inductive and capacitive elements. As these elements result in a phase difference between voltage and current, causing the energy to be alternately stored and released in the respective electric and magnetic …
Frequency meters are instruments that are widely used for the measurement of the frequency in various power system applications. Frequency is a very critical parameter in the electrical system as system stability, equipment performance, grid reliability, power quality, and economic efficiency all depend heavily on system frequency. Hence …
A flexible AC Transmission system includes the use of power electronics for controlling the voltage and the power flow of the AC transmission system. The power electronics include controlled shunt and series reactive power such as static Var compensator, static compensator (STATCOM), Thyristor controlled series compensation system (TCSC) …
The dissolved gas analysis of a transformer also called transformer gas analysis is an essential process or technique through which the condition of the transformer and its life expectancy can be calculated. Periodic dissolved gas analysis or DGA test can forecast the faults present in the oil-insulated electrical …
Air blast circuit breakers are a fast operating circuit breaker in which the quenching of the arc is achieved by a blast of compressed air inside the interrupter chamber. These breakers are mainly used for high-voltage applications because of their high speed operation. These breakers are suited for …
VRLA battery or valve-regulated lead acid is a type of lead acid battery that promotes minimum to no water addition maintenance, sealed in a structure with no acid leaks and no mists. It has a one-way valve to allow the escape of gas formed inside above a predetermined …
Vacuum circuit breakers uses high vacuum inside the interrupter unit as a dielectric media for suspension of the arc that is generated on contact separation. Vacuum has a very high dielectric strength in the range 106 -108 Volts/meter with excellent arc quenching characteristics. At high vacuum inside the …
The high voltage DC power line transmission is a system in which the bulk power is transmitted over long distances using direct current at a much-elevated voltage level. For long-distance transmission, the conventional AC system incurs various power losses making it an expensive mode of transmission. However, high …
Electrical continuity essentially means that there exists a conductive part, through which electricity can flow sufficiently. Electrical continuity can present itself in the insulated electrical part making it unsafe for further operation or is a much-needed aspect for the conductors for efficient propagation of electricity into any circuit. …
A smart meter is an electronic device that keeps a record of energy consumption, and electrical parameters like voltage levels, current, power factor, etc. These meters have a built-in communication channel through which it can communicate both ways between the meter and a central system. This communication can …
An uninterruptible power supply or UPS is a much-needed system for catering reliable, uninterrupted, high-quality power to vital loads such as data centers, critical health care support equipment, domestic equipment, and many more. Uninterruptable power supply is mostly a backup to the main power source from the utility …
Air Circuit Breaker (ACB) Air circuit breaker is the simplest form of circuit breaker. In this circuit breaker, the interruption of the arc is achieved by the natural deionization of gases by cooling. The arc is also lengthened for its resistance to get increased so that the source …
Design Parameters for EARTHMAT DESIGN 132 KV Reference Standard IEEE – 80 – 2000 Resistivity Data for EARTHMAT DESIGN 132 KV SS Soil Resistivity, ρ = 90 Ω m Surface layer resistivity, ρs = 3000 Ω m Surface layer thickness, hs=0.10 m Reflection factor between different resistivities …
Thermographic inspection Thermographic inspection is a nondestructive testing method, part of the maintenance schedule that is applied in different sectors. The power sector is one of them, and its use is quite widespread. It is applied to all types of facilities and voltage levels. Although, thermographic inspection points …
Requirement for a Tower Grounding Device The transmission tower grounding devices basically conducts the direct lightning current and power-frequency short-circuit currents efficiently into the earth. They are critical components which ensures the safety of persons around the towers as they hold certain lightning protection levels. The impulse impedance …
Methods for decreasing grounding resistance Decreasing grounding resistance of a system can efficiently bring down the ground potential rise which is fault current multiplied by the grounding resistance. Thus it makes the site safer during faults. Decreasing grounding resistance also makes the transfer potential lower, which is the …
Fault Current Division Factor During a local or remote earth fault in the substation, the fault current reaches the neutral of the power system via the earth. Part of this fault current flows to the earth from the earthing grid, the ratio between the portion of fault current …
Decrement Factor for grounding design Decrement factor Df is basically the ratio between the rms value of the asymmetrical fault current to the symmetrical grounding fault current. IG is the maximum asymmetrical alternating current flowing from the grounding grid to the surrounding earth, which includes the rms symmetric …
Principle to Determine Maximum Grounding Grid Current The maximum grounding grid current, IG is the maximum fault current that flows into the earth from the grounding grid for an internal fault at the substation or vice-versa for any external remote fault outside the substation. It is the most …
Data Required for the Design of Earth Mat of a Substation (i) Soil resistivity model for the site of the substation or soil resistivity test data where earth grid or earth mat has to be constructed. (ii) Electrical circuit single line diagram for the station where earth grid …
Safety Clearances The “safety clearance” is the minimum distance in air which is to be maintained between a live conductor and earth, or other equipment on which work has to be carried out. There are many different values of safety clearances used by various utilities around the world. …
Site Selection of a Grid Substation The site selection of a Grid Substation is the first and most important activity. This needs meticulous planning, foresight, skillful observation, and handling so that the selected site is technically, environmentally, economically, and socially optimal and is the best suited to the …
Arrangement for capacitor bank can be configured based on available voltage levels, protection phillosophy and required relaibility and flexibility of use. Most substations uses a star connected bank, however distribution units may be star or delta connected. Some system uses H arrangement in the units per phase of …
Shunt capacitor Banks Shunt capacitor Banks or SCBs are used in the power system as they deliver capacitive reactive power compensation that aids in improving power factor. These capacitor banks are easy to install and maintain providing an affordable and simple solution to power factor correction needs. Other …
Leakage Resistance of a Capacitor The resistance of the dielectric of the capacitor is called the leakage resistance of a capacitor. The dielectric medium in the ideal capacitor is considered a perfect insulator (i.e., it has infinite resistance), with zero current flowing through it when a potential difference …
In general, the electrical resistance of a material changes with the change in temperature. The effect of temperature on resistance varies according to the type of material as discussed below EFFECT OF TEMPERATURE ON RESISTANCE OF PURE METALS The effect of temperature on resistance is such that the …
The CT core sizing depends on the relay consideration for the feeder protection. FOR METERING CT CORE SIZING: The CT can be a multi-radio CT and the turns ratio or CTR can be calculated based on the estimated load/demand/requirement in the feeder. Also to take into consideration the …
The relay selection for transmission line protection utilizes one of the two major relaying philosophies. One is distance protection and the other is differential protection. Both of these protection philosophies are discussed in detail in previous posts. The other relays such as an overcurrent and earth fault relay …
PROTECTION CORE OF CT It is known that current transformers are used for protection and metering purposes. A current transformer or CT can have more than one core in the case of a multi-core CT that is normally used in power stations. One is used for metering purposes, …
INSTRUMENT SECURITY FACTOR OF CT Instrument security factor, ISF is the times of rated current above which the CT metering core will saturate. The ratio of the saturating primary current to the CT-rated current is known as the Instrument security factor. The multi-functioning meters or energy meters connected …
The burden of current transformer is basically the apparent power that is consumed at the secondary side at a specific power factor, rated secondary voltage, and current. It is because of the impedance/ admittance at the secondary circuit expressed in Siemens or ohm and power factor. Unlike a …
The accuracy class of Current Transformers used in the industry is designated by the highest permissible percentage ratio error at rated primary current and rated output. The RATIO ERROR in the accuracy class of current transformer The ratio error plays a major role in determining the accuracy class …
SIGNIFICANCE OF CT POLARITY Current transformer polarity is the direction of current in the secondary winding in relation to the primary current. It is often marked by square markings or P1 and P2. The polarity of the CT connection is of utmost importance in substation protection as the …
Step potential and touch potential are very essential factors in the designing of the earthing system of any substation. Step potential and touch potential also decide the overall safety of personnel working in the substation. As for humans, 25mA current can prove fatal hence calculation of step potential …
CONDUCTOR SIZING WITH IEEE-605 We have already discussed the busbar and the conductors in the previous articles. Now the essential part is to know how the conductor sizing is done for the main busbar of any substation. To explain this, we shall take the example of a 132KV …
Cable laying is a very essential part of any electrical installation. It helps optimize the power flow, reduces electromagnetic interferences on control cables, reduces fire risks, etc. MINIMUM PERMISSIBLE BENDING RADII OF CABLE LAYING. The electrical power cables should not be bent in a very sharp radius in …
CABLE SELECTION CRITERIA The design is based on a minimum of three factors: Short circuit current rating: It is the most important part of the cable selection criteria. It basically is the maximum current that the cable has to handle in case of a fault until the fault …
KNEE POINT TEMPERATURE The temperature at which the envelope of a conductor becomes mechanically unloaded is called knee point temperature. When the temperature of a composite conductor is increased, the aluminium (or aluminium alloy) envelope wires undergoes more expansion than the core does. This expansion results in reduction …
DIFFERENT TYPES OF HTLS CONDUCTORS High temperature low sag, htls conductors are modern conductors with enhanced thermal sag properties. Their maximum continous operating temperature is also increased, which aids in the conductor’s high current carrying capacity and also optimizing transmission network of a region. These high performance conductors …
POWER CONDUCTORS Power Conductors are the most essential part of the transmission and distribution of electricity. It is the medium via which the current flows. Normally it is made of copper or aluminium alloy as these metals have proven good service and have less resistivity and cost. TYPES …
POWER CLAMPS Electrical energy flows through many equipment and various lines to reach the end consumer or load. In this process, it requires many terminations of conductors to all the equipment it passes through. This termination is made possible through the use of various clamps and connectors that …
KNEE POINT VOLTAGE OF A CURRENT TRANSFORMER As we know from our previous discussions the function of a current transformer is to translate the current of its primary winding into a proportional value of current in the secondary winding. This stepping down of current from higher primary values …
CT SATURATION: In the ideal scenario of the operation of a current transformer, the secondary current of the CT, (Is) is directly proportional to its primary current (Ip). However, in the case of saturation of the CT, the proportionality does not remain the same. Let us discuss why. …
RESTRICTED EARTH FAULT PROTECTION The most vital and important protection for a transformer is the biased differential relay protection of the transformer, which is discussed in detail in previous articles. It provides excellent protection against phase-to-phase faults and phase-to-earth faults within the differential zone of protection. It covers …
OVER FLUXING PROTECTION OF TRANSFORMER In transformer design practice the rated value of flux density is 1.7 to 1.8 Tesla. However, the saturation flux density of the CRGO steel sheet is of the order of 1.9 to 2.1 Tesla. This means the transformer core can handle a flux …
Supply of continuous electricity is the main motto of power generation, transmission and distribution. However, from our previous discussions, it is known to us that a continuous supply of power is an ideal case. Auto recloser is therefore a relay that functions to reclose the contacts of a …
STUB PROTECTION: It is basically an in-built function of a distance relay. It falls under the auxiliary part of the distance relay. It is mostly used in one-and-half-bus bar schemes. As we already know from our previous article on the bus bar scheme in one-and-a-half bus bar schemes, …
MULTIPLICATION FACTOR OF ENERGY METERS We generally use a Special energy meter for keeping the count of energy flowing through the system. The meter we use has an input connection from the current transformer’s metering core’s secondary side. With current input, we also provide the voltage input to …
ENERGY METER The meter used for the measurement of electrical energy consumed by loads in a definite time period is called an energy meter. The meter’s units are basically graded in Kwh. Energy meters are used to account for all energy transferred via the metering point for the …
OLTC OLTC or On-load tap changer is a device that is used for voltage regulation of a transformer without any interruption in the power flow to the load. Tap changing basically alters the turns ratio of the transformer thus regulating the voltage. The main feature of the On-load …
CARRIER AIDED PROTECTION The main aim of electrical power transmission is to maintain an uninterrupted power supply of electricity to all consumers. Electrical faults however cause interruption of supply. When the fault is detected by the protective relays, the fault current is interrupted by the circuit breaker. In …
The trip circuit supervision relay is the relay that monitors the healthiness of the trip circuit of a circuit breaker. It remains always vigilant and on the occurrence of any fault in the trip circuit, it raises an alarm. It is one of the most important parts of …
MASTER TRIP RELAY A master trip relay is a contact multiplier auxiliary relay used in the control and relay panel of a substation or any plant. It is a very essential part of the control and protection scheme of any substation. It offers high reliability and high contact …
The term BCU refers to the Bay Control Unit of a substation’s associated bay or feeder. The BCU or Bay control unit performs various bay operations based on pre-defined logic. It acts as an interface between the operator and the electrical switchgear present in the associated bay. It …
OTI is the oil temperature indicator of an oil-filled transformer. Since the transformer oil is also used for cooling purposes, the temperature of the oil gives out the internal thermal condition of the transformer. WTI is the winding temperature indicator of the power transformer. The windings of the …
A pressure relief valve of a transformer or PRV is a mechanical safety device used for the protection of transformers, on-load tap changers OLTC and other similar equipment which can release the excess pressure inside them because of various reasons. The Pressure relief valve of a transformer mitigates …
A protective relay works like a brain in the power system. It collects the electrical parameters from the field and computes them, senses faults, takes decisions, and gives output to the associated circuit breaker to isolate the faulted section. Protective relays can be broadly classified into three types. …
Buchholz relay is a mechanical, gas-actuated device that utilizes mercury switches to initiate alarm and trip signals on the occurrence of incipient faults inside an oil-filled transformer. It may be noted that these relays are installed on transformers above 750KVA capacity. Incipient faults are those faults that are …
Earth fault protection is a protective scheme used for the protection of an element of a power system against electrical faults involving the earth. An earth fault is an electrical fault that involves the ground. Examples are—single line-to-ground (L-G) faults and double line-to-ground (2L-G) faults. Faults that are …
A directional relay is one which is actuated by two electrical parameters namely current and voltage. The directional elements in the relay help the relay to recognize the direction of power flow based on phase angle comparison and isolate electrical faults in reverse the direction of normal power …
Overcurrent protection relays are the protective relay that operates to issue a trip command when the current value in a circuit exceeds a preset. The preset value of the current which if exceeded, makes the relay operational is known as the pickup value of the overcurrent protection relay. …
Differential protection is a relaying scheme used to protect an element of a power system from electrical faults. The differential protection scheme utilizes the vector difference of two or more similar electrical parameters and compares it to a preset value. If the preset value is exceeded it generates …
Distance protection is basically a non-unit form of protection in the power system that protects a transmission line by sensing and comparing the impedance to a set impedance value of the line. It is economical and has technical benefits. Unlike the phase, neutral overcurrent protection the main advantage …
Local breaker backup or LBB protection is a circuit breaker failure scheme that operates to protect a faulty circuit when the associated circuit breaker fails to trip, by tripping all other circuit breakers associated with the bus bar. Thus, isolating the faulty circuit. A circuit breaker functions to …
In the substation, the disconnector or Isolator does the same work as the circuit breaker do i.e., isolation of the circuit from the power supply. But the difference is that initially automatic circuit isolation/ tripping is achieved by a circuit breaker or CB due to the arc quenching …
A lightning arrester is a protective device which conducts or diverts the harmful high voltage surges on the power system safely to the ground. It is the frontline warrior used for the protection of equipment against the travelling waves and overvoltages in the overhead transmission line. Though the …
Potential Transformer: A potential Transformer or voltage transformer is a type of instrument transformer that is used to step down the voltage from a higher level to an optimal level where it can be measured safely. It has higher turns in the primary winding and a smaller number …
A Current transformer is a type of instrument transformer that is used to step down the current of the primary side to a minimal value on the secondary side for ease of metering using standard ammeters and for protection purposes. As nowadays most relays are numeric and digital …
Transformer oil or mineral oil is used extensively in the transformer to provide electrical insulation between the core, windings, and the body of the transformer. The live part of the transformer, core, and winding are submerged in transformer oil that provides electrical insulation to the main tank. Transformer …
A Circuit breaker is a device that can operate on command to make or break an electrical circuit in a fraction of a second. Breaking a circuit on detection of an electrical fault is very essential otherwise fault current propagation for enhanced time can potentially damage the electrical …
