An electrical transformer does not employ any moving parts to transfer energy which means that there is no friction and hence no windage losses. Morgan lacey in 1925, based on a series of pamphlets entitled transformer abstracts that were. The construction of potential transformer is quite similar to that of a power transformer but the loading of a potential transformer is always small, sometimes only a few voltampere. Potential transformer pt definition the potential transformer may be defined as an instrument transformer used for the transformation of voltage from a higher value to the lower value. Failure of transformer in power substation is not a sudden phenomenon, for that matter each and every failure will take place only after alerting through some presigns. Based on winding, the transformer can be of three types. If they went unnoticed or unattended will results into a failure. To do so, the primary winding of the transformer is connected across the high voltage lines. This is normally achieved by changing the ratios of the transformers on the system by altering the number of turns in one winding of the appropriate transformer s. The capacitor voltage transformer cvt uses a capacitance potential divider and is used at higher voltages due to a lower cost than an electromagnetic pt. According to the design, transformers can be classified into two. Potential transformers are also called voltage transformers. The secondary winding is designed so that a voltage of 100 to 120 v is delivered to the instrument load. Voltage transformer or potential transformer theory electrical4u.
The engineering mindset how does a transformer work working principle electrical engineering. This type of transformer is categorized on the basis of a number of turns in the primary and secondary windings and the induced emf. They are designed for connection linetoline or linetoneutral in the same manner as ordinary voltmeters. A potential transformer is a carefully designed, extremely accurate stepdown transformer.
These are used to operate and control measuring devices, relays and other devices. By multiplying the reading on the voltmeter called the deflections by the ratio of transformation, the user can determine the voltage on the high side. In the case of a yconnected winding with neutral point connected to ground. Current transformers ct are a series connected type of instrument. Transformer cant stepup or stepdown the level of dc voltage or dc current. The specific performance characteristics of instrument transformers are easily determined from the equivalent circuit.
In essence, electrical substations consist of power transformers, circuit breakers, and secondary systems for protection, load control and metering. A transformer is a stationary device which is used for stepping updown of voltage of alternating current. All transformer types pdf ebook by digital library of electrical and electronics engineering is a catalog of all different types of transformers that are around us. The potential transformer is mainly classified into two types, i. Voltage transformer or potential transformer theory. This means that there are no friction or windage losses associated with other electrical machines. Potential transformer accuracy voltage disturbance. Transformer types are also designated by the function the transformer serves in a circuit, such as an isolation transformer. Mar 07, 2016 a tap changer is a device fitted to power transformers for regulation of the output voltage to required levels. What are a potential transformer and a current transformer. A potential transformer is a conventional transformer having primary and secondary windings. The types of transformers differ in the manner in which the primary and secondary coils are provided around the laminated steel core of the transformer.
Replace the transformer and core to be lifted for thoroughly checking. Instrument transformers are of two types current transformer c. Voltage transformers are together with current transformers known as instrument transformers. Stepping up is done to evacuate the generated power while stepping down is done for the consumer requirements. Transformer basicsworking principle,construction,types. Potential transformer is also known as voltage transformer. It is based on the principle of mutual induction, a transformer is an ac device it cannot work on dc a transformer can only change the ac currentvoltage. Types of electrical transformers and their applications. Amp rating indicating diameter inches mm length inches mm ferrule length inches mm max voltage max ir rms sym spare parts clips spare parts live parts. Two types of voltage transformer are used for protectiverelaying purposes, as follows. Two types of voltage transformer are used for protectiverelaying purposes.
A tap changer is a device fitted to power transformers for regulation of the output voltage to required levels. This transformer step down the voltage to a safe limit value which can be easily measured by the ordinary low voltage instrument like a voltmeter, wattmeter and watthour meters, etc. On each end of the transformer core is an end terminal for the winding, but there is also a second winding that connects at a key intermediary point, forming a third terminal. Voltage transformers and potential transformers are also used to operate protective relays and devices, and in many other applications. However, transformers do suffer from other types of losses called copper losses and iron losses but generally these are quite small. Electrical transformer components free online course. Dec 30, 2018 potential transformer or voltage transformer gets used in electrical power system for stepping down the system voltage to a safe value which can be fed to low ratings meters and relays. In a transformer the energy is conveyed from primary to secondary. Take corrective action according to observations and oil test report. Instrument transformer in power system, the currents and voltages are very large therefore, their direct measurements are not possible. Types of transformer different types of transformer. There are several classes of accuracy for instrument transformers defined by the ieee, csa.
Today we will know about the potential transformer. They are designed to present negligible load to the supply being measured and have an accurate voltage ratio and phase relat. Institute of electrical engineers, 33 west 39th street, new york 18, n. Here we discuss different types of transformers are the step up and step down transformer, distribution transformer, potential transformer, power transformer, 1. Voltage and potential transformers selection guide. For example, suppose a potential transformer establishes a ratio of 500 to 1. Majorly these are classified into outdoor and indoor potential transformers. These offer a small footprint for the design engineer looking to sensor current on.
The winding connections also influence the magnitude of fault current. Transformer only stepup or stepdown the level of ac voltage or ac current. Validating current and voltage transformer wiring youtube. Instrument transformers are high accuracy class electrical devices used to isolate or transform. All transformer types pdf ebook electrical and electronics. Voltage and potential transformers that are designed for monitoring singlephase. Apr 16, 2016 types of transformers the transformers are classified based on voltage levels, core medium used, winding arrangements, use and installation place etc. This is normally achieved by changing the ratios of the transformers on the system by altering the number of turns in one winding of the appropriate transformers. Transformers are classified based on many things and factors like voltage level, core types, windings arrangements, core medium, and many other factors.
Potential transformer or voltage transformer gets used in electrical power system for stepping down the system voltage to a safe value which can be fed to low ratings meters and relays. For current transformers, the value of the reactance x is determined in a special way so that it represents the leakage flux. It is normally used with a standard 120volt voltmeter. By using inductively coupled electrical conductors as the main agent of transfer, a change in current in the first circuit is carried over to the second circuit, which subsequently assumes the. Voltage transformer or potential transformer voltage transformers vt, also called potential transformers pt, are a parallel connected type of instrument transformer, used for metering and protection in highvoltage circuits or phasor phase shift isolation. Potential transformer voltage transformer is used for protection and measurement. In coretype transformer, the windings are given to a considerable part of the core. On the secondary side, all the measuring tools and instruments such as meters are connected to measure and analyse the voltage level. Transformers are more than just extraterrestrial robotstheyre also highly useful devices for transferring energy between circuits, and there are various different types of electrical transformers. The electromagnetic potential transformer is a wirewound transformer. The potential transformers shall be electromagnetic, outdoor type, single phase. Troubleshooting transformer in power substation and. Mar 11, 2017 a potential transformer or voltage transformer is a special kind of transformer used to measure voltages higher than you would want to measure directly. A general overview of abbs current and voltage transformers.
Basics, maintenance, and diagnostics vii contents continued page 4. There are several transformer types used in the electrical power system for different purposes, like in power generation, distribution and transmission and utilization of electrical power. Different types of transformers and their applications. Electrical engineering electrical transformer components. Supply authorities are under obligation to their customers to maintain the supply voltage between certain limits. Instrument transformers convert signal levels from dangerous high voltage or inconvenient high current, or current at high voltage to levels appropriate for metering.
Instrument transformers are specific types of transformers used for voltage and current measurements. Actually they are protective type voltage transformer. Potential transformer definition potential transformer or voltage transformer gets used in electrical power system for stepping down the system. These are widely used transformer types for all the applications. The working procedure on how transformers work types. Voltage transformers are in most situations connected between phase and ground. Cts current transformers pts potential transformers. Current transformer is used to step down the current of power system to a lower level to make it feasible to be measured by small rating ammeter i. A potential transformer or voltage transformer is a special kind of transformer used to measure voltages higher than you would want to measure directly. For the instrument transformers the typical engineering.
Types of transformers the transformers are classified based on voltage levels, core medium used, winding arrangements, use and installation place etc. The types of transformers differ in the manner in which the primary and secondary coils are provided around the laminated steel core. The standard that describes voltage transformers in details is iec 186. The first and second terminals conduct the primary voltage, while the third terminal works alongside either the first or second terminal to provide a secondary form of. The secondary voltage is substantially proportional to the primary voltage and differs from it in phase by an angle that is approximately zero. Transformer book is still in demand is a tribute to the publishers and to the authors who have carried the torch to light our way for 75 years. Cts current transformers pts potential transformers 5 potential transformers pts pts step down high voltages to the voltage needed by the meter usually 120v occasionally 67v.
Troubleshooting transformer in power substation and detailed. Voltage transformers is also called as potential transformers this is a parallel connected type of instrument transformer. What is a transformer tap changer engineering tutorial. Based on the function of a potential transformer, there are two types, metering voltage transformers. Voltage transformer is necessary for directional, voltage, distance protection. Instrument transformer theory and testing steve hudson, pe. Power transformers unit substation distribution instrument transformers potential transformer current transformer transformer types on the basis of stepping stepup transformer stepdown transformer on the basis. Potential transformers used primarily in a step down environment to monitor voltage. Ideal for sharing with potential employers include it in your cv, professional social media profiles and job applications. Working of potential transformer the electrical portal. The different types of transformer are step up and step down transformer, power transformer, distribution transformer, instrument transformer comprising current and potential transformer, single phase and three phase transformer, auto transformer, etc.
Jun 01, 2015 potential transformer is a voltage stepdown transformer which reduces the voltage of a high voltage circuit to a lower level for the purpose of measurement. Current transformers are connected in ac power circuits to feed the current coils of indicating and metering instruments ammeters, wattmeters, and watthour meters and protective relays. The transformers are classified based on voltage levels, core medium used, winding arrangements, use and installation place, etc. Unit 14 transformers objectives after studying this unit, the student will be able to state the purpose of a transformer. Explained types of transformer with applications etechnog. The following points highlight the two main types of power transformers. Which of the following does not change in a transformer. Commercially available relays and meters used for protection and metering, are designed for low voltage. Transformers based on voltage levels the transformers are classified as stepup and stepdown transformers as the voltage ratios from primary to secondary. Transformers explaining the basics of transformers. Voltage and potential transformers are used to measure voltage potential. Digital certificate a downloadable certificate in pdf format. There are three primary types of potential transformers pt.
Figure 4 works well for most instrument transformers. These can be single or three phase voltage transformers available for different range of operating voltages that are used for outdoor relaying and metering applications. For example, the potential transformer mentioned above having a rating of 480. A fault on a transformer winding will result in currents that depend on the source, neutral grounding impedance, leakage reactance of the transformer, and the position of the fault in the windings. It might appear that the extension of range could be conveniently done by the use of shunts for currents and multiplier for voltage measurement, as in dc. Transformer operates when both circuits take effect of mutual induction. The potential transformer may be defined as an instrument transformer used for the transformation of voltage from a higher value to the lower value. Capacitor potential transformer is a combination of capacitor potential divider and a magnetic potential transformer of relatively small ratio.
Potential transformers are the types of instrument transformers that establish a known ratio between the potential difference across the equipment and the potential difference across a voltmeter. Distribution transformers are generally used in electrical power distribution and transmission systems. A transformer does not require any moving parts to transfer energy. Instrument transformers comprise a large category of current and potential transformers for. Potential transformer accuracy february 17, 2019 admin power engineering potential transformer definition. These are the most commonly used transformer types for all the applications. These are connected across or parallel to the line which is to be monitored. These are available in single or threephase and operate with the highest accuracy. The various types of transformer shown in the figure above are explained in detail below. Any internal fault such as short circuited core, core bolts clamps insulation failure etc. This is a simplest form of potential transformer definition. This class of transformer has the highest power, or voltampere ratings, and the highest. Instrument transformer basic technical information and. Potential transformers pt or voltage transformers vt can be defined as devices used to step down voltage from high voltage typically used in transmission and distribution to a low voltage typically between 50150v.
1025 951 845 607 1520 880 446 102 146 524 1198 1625 408 1060 1587 1665 190 14 1334 110 937 1657 345 1256 247 413 1655 1223 264 960 457 338 1403 61 1356 1013 1446 135 1115 1368