Read through the different types we supply below and use our instrument transformer rfq form to request a specific part to meet your requirements. The current transformer is used to measure the current of the transmission and distribution line, a potential or voltage transformer is used to measure the voltage. 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. This type of transformer is categorized on the basis of a number of turns in the primary and secondary windings and the induced emf. The ratio of an instrument transformer is the relationship of its primary rating to its secondary rating.
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. In coretype transformer, the windings are given to a considerable part of the core. These offer a small footprint for the design engineer looking to sensor current on. 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. Electrical engineering electrical transformer components. Based on the function of a potential transformer, there are two types, metering voltage transformers. This means that there are no friction or windage losses associated with other electrical machines. Potential transformer accuracy february 17, 2019 admin power engineering potential transformer definition. Ideal for sharing with potential employers include it in your cv, professional social media profiles and job applications. 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.
Types of transformer different types of transformer. 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. In a transformer the energy is conveyed from primary to secondary. A potential transformer is a conventional transformer having primary and secondary windings. Instrument transformers are high accuracy class electrical devices used to isolate or transform.
Instrument transformers are of two types current transformer c. What are a potential transformer and a current transformer. The working procedure on how transformers work types. The various types of transformer shown in the figure above are explained in detail below.
They are designed to present negligible load to the supply being measured and have an accurate voltage ratio and phase relat. 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. To do so, the primary winding of the transformer is connected across the high voltage lines. Digital certificate a downloadable certificate in pdf format. 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. Unit 14 transformers objectives after studying this unit, the student will be able to state the purpose of a transformer. Based on winding, the transformer can be of three types. Types of transformers the transformers are classified based on voltage levels, core medium used, winding arrangements, use and installation place etc. These are connected across or parallel to the line which is to be monitored. 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. 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. 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. 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. These are the most commonly used transformer types for all the applications. Distribution transformers are generally used in electrical power distribution and transmission systems. 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. For the instrument transformers the typical engineering. Potential transformers used primarily in a step down environment to monitor voltage. 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.
A transformer is a stationary device which is used for stepping updown of voltage of alternating current. If they went unnoticed or unattended will results into a failure. However, transformers do suffer from other types of losses called copper losses and iron losses but generally these are quite small. Transformer operates when both circuits take effect of mutual induction. Voltage transformers and potential transformers are also used to operate protective relays and devices, and in many other applications. These are widely used transformer types for all the applications. The electromagnetic potential transformer is a wirewound transformer. 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. The potential transformer may be defined as an instrument transformer used for the transformation of voltage from a higher value to the lower value. Two types of voltage transformer are used for protectiverelaying purposes, as follows. Mar 07, 2016 a tap changer is a device fitted to power transformers for regulation of the output voltage to required levels.
Transformer only stepup or stepdown the level of ac voltage or ac current. Capacitor potential transformer is a combination of capacitor potential divider and a magnetic potential transformer of relatively small ratio. All transformer types pdf ebook electrical and electronics. Transformers based on voltage levels the transformers are classified as stepup and stepdown transformers as the voltage ratios from primary to secondary. Stepping up is done to evacuate the generated power while stepping down is done for the consumer requirements. This is a simplest form of potential transformer definition. Instrument transformer in power system, the currents and voltages are very large therefore, their direct measurements are not possible. A tap changer is a device fitted to power transformers for regulation of the output voltage to required levels. Instrument transformers convert signal levels from dangerous high voltage or inconvenient high current, or current at high voltage to levels appropriate for metering. 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. The specific performance characteristics of instrument transformers are easily determined from the equivalent circuit. Transformer basicsworking principle,construction,types.
Morgan lacey in 1925, based on a series of pamphlets entitled transformer abstracts that were. Commercially available relays and meters used for protection and metering, are designed for low voltage. A general overview of abbs current and voltage transformers. Any internal fault such as short circuited core, core bolts clamps insulation failure etc.
For current transformers, the value of the reactance x is determined in a special way so that it represents the leakage flux. Instrument transformers are specific types of transformers used for voltage and current measurements. Explained types of transformer with applications etechnog. The following points highlight the two main types of power 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. 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. Majorly these are classified into outdoor and indoor potential transformers. Replace the transformer and core to be lifted for thoroughly checking. Transformers explaining the basics of transformers. Figure 4 works well for most instrument transformers. 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. 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. Transformer cant stepup or stepdown the level of dc voltage or dc current.
The potential transformers shall be electromagnetic, outdoor type, single phase. 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. Conventional wound type transformer is very expensive because of the requirement of the insulations. Troubleshooting transformer in power substation and. Current transformers ct are a series connected type of instrument. Here we discuss different types of transformers are the step up and step down transformer, distribution transformer, potential transformer, power transformer, 1. 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.
Lets say, for instance, that you have a 100kv grid and want to know how much powerenergy you. Voltage transformer is necessary for directional, voltage, distance protection. There are three primary types of potential transformers pt. 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. The potential transformer is mainly classified into two types, i. A potential transformer is a carefully designed, extremely accurate stepdown transformer. 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. An electrical transformer does not employ any moving parts to transfer energy which means that there is no friction and hence no windage losses. Transformers are classified based on many things and factors like voltage level, core types, windings arrangements, core medium, and many other factors. Basics, maintenance, and diagnostics vii contents continued page 4. Cts current transformers pts potential transformers. A transformer does not require any moving parts to transfer energy.
There are several classes of accuracy for instrument transformers defined by the ieee, csa. In essence, electrical substations consist of power transformers, circuit breakers, and secondary systems for protection, load control and metering. The standard that describes voltage transformers in details is iec 186. Potential transformers are also called voltage transformers. 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.
Instrument transformer theory and testing steve hudson, pe. These are used to operate and control measuring devices, relays and other devices. It is normally used with a standard 120volt voltmeter. Voltage transformers are in most situations connected between phase and ground. Voltage and potential transformers are used to measure voltage potential. Instrument transformers comprise a large category of current and potential transformers for. Today we will know about the potential transformer. Voltage and potential transformers selection guide. For example, suppose a potential transformer establishes a ratio of 500 to 1.
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. What is a transformer tap changer engineering tutorial. 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 winding connections also influence the magnitude of fault current. 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. 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. According to the design, transformers can be classified into two. Actually they are protective type voltage transformer. A potential transformer or voltage transformer is a special kind of transformer used to measure voltages higher than you would want to measure directly. Voltage and potential transformers can be used with voltmeters for voltage measurements, or with current transformers for wattmeter or watthour meter measurements. Types of electrical transformers and their applications. Supply authorities are under obligation to their customers to maintain the supply voltage between certain limits. Instrument transformer basic technical information and. These are available in single or threephase and operate with the highest accuracy.
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. Potential transformer definition potential transformer or voltage transformer gets used in electrical power system for stepping down the system. Take corrective action according to observations and oil test report. On the secondary side, all the measuring tools and instruments such as meters are connected to measure and analyse the voltage level. 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. Potential transformer voltage transformer is used for protection and measurement. Working of potential transformer the electrical portal. This class of transformer has the highest power, or voltampere ratings, and the highest. Electrical transformer components free online course. Transformers multiple choice questions with answers 1.
The types of transformers differ in the manner in which the primary and secondary coils are provided around the laminated steel core. The transformers are classified based on voltage levels, core medium used, winding arrangements, use and installation place, etc. Potential transformer accuracy voltage disturbance. Voltage transformer or potential transformer theory electrical4u. Institute of electrical engineers, 33 west 39th street, new york 18, n. Potential transformer is also known as voltage transformer.
Voltage transformers is also called as potential transformers this is a parallel connected type of instrument transformer. Different types of transformers and their applications. Troubleshooting transformer in power substation and detailed. 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.
Voltage and potential transformers that are designed for monitoring singlephase. Validating current and voltage transformer wiring youtube. Transformer types are also designated by the function the transformer serves in a circuit, such as an isolation transformer. 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. They are designed for connection linetoline or linetoneutral in the same manner as ordinary voltmeters. Apr 16, 2016 types of transformers the transformers are classified based on voltage levels, core medium used, winding arrangements, use and installation place etc. The engineering mindset how does a transformer work working principle electrical engineering. Which of the following does not change in a transformer. The secondary voltage is substantially proportional to the primary voltage and differs from it in phase by an angle that is approximately zero. Voltage transformer or potential transformer theory. In the case of a yconnected winding with neutral point connected to ground. Voltage transformers are together with current transformers known as instrument transformers. For example, the potential transformer mentioned above having a rating of 480. 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.