Instrument transformers are necessary to provide values that can be used by these devices which can be. The most common usage of instrument transformers is to operate instruments or metering from high voltage or high current circuits, safely isolating secondary control circuity from the high voltages or currents. Instrument transformers cg power and industrial solutions. Highest quality instrument transformers temco is a member of the better business bureau, constructing and distributing only the finest quality instrument transformers. High voltage transformer hvt the standard voltage transformer svt is suitable to test the voltage transformer of single and double pole transformers. Nov 17, 2019 instrument transformers provide electrical isolation between high voltage power circuit and measuring instruments. Amrans product portfolio includes standard products as well as numerous custom products specifically designed and developed for oem specific. Tvi is a sf6 gasinsulated inductive voltage transformer built for revenue metering and protection in high voltage networks. Instrument transformers are thus installed when it is necessary to obtain. Arteche offers a wide range that covers all our customers needs. The most common use of instrument transformer is to safely isolate the secondary winding when the primary has high voltage and high current supply so that the measuring instrument, energy meters or relays which are connected to the secondary side of the transformer will not get damaged. 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 application guide abb group. Temco transformer manufacturer sales standard and custom instrument transformers manufactured to spec.
For this aim, devices called instrument transformers are used to reproduce primary parameters at scaled down values which are suitable for measuring instruments and protection relays. Instrument transformers are used in ac system for measurement of electrical quantities i. Cts current transformers pts potential transformers. What is the forecast of the instrument transformer market.
Types of transformer different types of transformer. Instrument transformers are special types of transformers intended to measure cur rents and voltages. Instrument transformers high voltage 5 current transformers are designed to provide a scaled down replica of the current in the hv line and isolate the measuring instruments, meters, relays, etc. It was found that higher harmonic from disturbance signal in the primary circuits of both voltage and current transformers causes increase of errors during the. The instrument transformers are current or voltage transformers to be used in combination.
Instrument transformer is an electrical device of high accuracy that is used to transform or isolate current or voltage 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. Instrument transformers convert the currents and voltages of the h. Ferroresonance can occur when the primary of a voltage transformer is connected line to ground in an ungrounded circuit. Transformers used for voltage potential measurement steps down the voltage to the level of voltmeter. Which reduces the electrical insulation requirement for measuring instruments and protective circuits and also assures the safety of operators. Amran instrument transformers is a leading manufacturer of low voltage and medium voltage instrument transformers current and voltage transformers with multiple manufacturing plants in usa and india. Several measuring instruments can be connected through a single transformer to power. The use of current or voltage transformer for other purpose then described above is forbidden if not agreed with the producer. The flux flows in the part of the core represented by the lefthand exciting branch of the equivalent circuit shown in figure 1. Instrument transformers are high accuracy class electrical devices used to isolate or transform voltage or current levels. Instrument transformers for low voltage applications are produced according national and international standards.
Applications include revenue metering, protection and control, power. The transformers are specifically designed to be used with the electrical equipment which falls into a variety of devices known as instruments. Their role in electrical systems is of primary importance as they are a means of stepping down the current or voltage of a system to measurable values, such as 5a or 1a in the case of a current transformers or 110v or 100v in the case of a voltage transformer. Instrument transformer technologies voltage and current. Voltage transformers are most commonly used to lower the high line voltages down to typically 120 volts on the secondary to be connected to a voltmeter, watthour meter, or protection relay. The instrument transformers like voltage transformer and current transformer are used for connecting the electrical instruments to the measuring instruments. There are three main types of voltage transformers. Measuring the voltage drop at the source combined with ohms law will give us the burden impedance. You can transform the voltage or current down with a transformer whose turns ratio is accurately known, then measuring the stepped down magnitude with a normal range instrument. Instrument transformer division residual voltage transformer residual voltage transformer is used to detect unbalanced voltage in three phase system and to supply voltage to directional earthfault relay. This configuration results in the magnetizing reactance of the vt being in a parallel. Voltage transformers voltage transformers are connected across the points at which the voltage to be measured. Temco manufactures a variety of electrical power transformers. Overall working of both the transformers is same, they both differ only in application point of view.
Instrument transformers are divided in to two categories. Instrument transformers are used for measurement and protective application, together with equipment such as meters and relays. Routine test report together with instrument transformer are delivered. Hence, it is essential to inspect and calibrate those instrument transformers at regular intervals. What are the difference between power transformer and. Gasinsulated instrument transformer for enhanced safety and reliability tvi is a sf6 gasinsulated inductive voltage transformer built for revenue metering and protection in high voltage networks. Used in ac system for the measurement of current, voltage, power and energy. Instrument transformers are used to supply measured quantities of current and voltage in an appropriate form to controlling and protective apparatus, such as energy meters, indicating instruments, protective relays, fault locators, fault recorders and synchronizers. A specialised business unit spearheads the export thrust for inhouse products as well as carefully outsourced synergestic. Power voltage transformers station service transformers. Instrument transformer article about instrument transformer. Therefore, they are the perfect solution wherever low voltage is needed and high. Therefore, they are the perfect solution wherever low voltage is needed and high voltage is available. Instrument transformers are necessary to provide values that can be used by these devices which.
For current transformers, the value of the reactance x is determined in a special way so that it represents the leakage flux. Instrument transformer sale, instrument transformers on sale. Trench power voltage transformers power vts combine the attributes of an inductive voltage transformer with the application of a small power transformer. Potential transformer instrument exhxvt series f eatu r es used with 150 volt full scale a. Figure 1 shows some of the most basic uses for instrument transformers. Read pdf abb instrument transformer guide voltage instrument transformers applicaton guide. The original magnitude can be determined by just multiplying the result with the transformation ratio. To insulate the metering circuit from the primary high voltage system. Power transformers are used to transfer large amount of power form 1 voltage level to other voltage level for obvious reasons and are used at p. The tvi has been designed for voltage up to 420 kv. The name instrument transformer is a general classification applied to current and voltage devices used to change currents and voltages from one magnitude to another or to perform an isolating function, that is, to isolate the utilization current or voltage from the supply voltage for safety to both the operator and the end device in use.
Instrument transformer basic technical information and. Instrument transformers for lowvoltage applications are produced according national and international standards. 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. Power voltage transformers power vts combine the attributes of an inductive voltage transformer with the application of a small power transformer. Magnetic voltage transformers ordinary two winding type used for l. A potential transformer is a conventional transformer having primary and secondary windings. Current transformer burdens are typically expressed in va.
Analyzing the voltage drop patterns throughout the circuit confirms the wiring is correct. Ehv instrument transformer, medium voltage vacuum switchgear and lightning arresters. Finds a wide application in protection circuits of power system ex. Here we will cover six important aspects of using instrument transformer in the power system.
Generally, the metering its require high accuracy in the range of normal oper ating voltage and current. Current transformers reduce high voltage currents to a much lower value and provide a convenient way of safely monitoring the. Instrument transformers are also used with protective relays for protection of power system basic function of instrument transformers is to step down the ac system voltage and current. We also offer specially designed and custombuilt solutions for your specific applications. The primary reason for having an instrument transformer is to provide analog information at low voltage levels, insulated from the higher system voltages.
The high voltage transformer hvt generates the test voltage for the accuracy test of the voltage instrument transformers. Instrument transformers for metering purposes must have a high degree of accuracy up to class 0. In this area you will find catalogues with comprehensive information as well as forms and documents as pdf files for downloading. Itec cto current transformers utilize high permeability, grain oriented. Solutions main characteristics of power vts in the trench group portfolio. Temco has experience manufacturing and selling quality electrical products since 1968. The most common usage of instrument transformers is to operate instruments or metering from high voltage or high. Protection its require linearity in a wide range of voltages. Current, voltage and combined transformers, oilpaper or gas insulated up to 800 kv. Gasinsulated instrument transformer for enhanced safety and reliability. These transformers reduce the voltage and current from high value to the low value which can be measured by conventional instruments. The current and voltage transformers can be calibrated for different countries and delivered with the corresponding certificate. Current and voltage transformers are responsible for scaling primary system signals.
The primary winding of the transformer is connected to the high voltage or high current circuit, and the meter or relay is connected to the secondary circuit. Such specially constructed transformers with accurate turns ratio are called as instrument transformers. Instrument transformers mitsubishi electric corporation. All documents offered for download remain property of ritz instrument transformers gmbh and are made available for your information only. Instrument transformer technologies pty ltd is known and respected throughout southern africa, thanks to the continuous development of knowhow and technology, the highly trained staff and the efficient state of production and testing facilities.
Similarly, current transformers take a high current. Current and voltage potential instrument transformers. Metering transformer applications in mv electrical distribution, the high current and voltage values mean that they cannot be used directly by metering or protection units. Current transformer basics and the current transformer. Voltage transformers are most commonly used to lower the high line voltages down to typically 120 volts on the secondary to be connected to a voltmeter, watthour. The primary winding of the vt is connected in parallel with the monitored circuit, while the primary winding of the ct is connected in series. Operations commenced in 1980 with the manufacture of medium voltage switchgear, which was relocated from kanjur mumbai works. To transform currents or voltages from a usually high value to a value easy to handle for relays and instruments.
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