In thrutype units, busbar and copper tube inside the unit need to be at the same potential. For use with rectifier type analog panel meters or digital indicators. Turns ratio tests optional test this test is to ensure the turns ratio of ct at all taps. Transformers used for voltage potential measurement steps down. When current flow exceeds that rating, the metering core will become saturated, thereby limiting the amount of current level within the device. The classification of protection current transformers follows the. Current transformers ct are used in high voltage hv and medium voltage mv 1 installations to give an image of electrical current to protection relays and units and metering equipment and they are designed to provide a current in its secondary proportional to the current flowing in its primary. A true bar type current transformer is a toroidal type transformer with a bus bar as an integral part of the current transformer which is permanently inserted. Transformer with the primary current be turned twice which help to keep the samerated turns ratio1. Like the power transformer, the current transformer also contains a primary and a. They are very popular in submetering applications where existing systems are being upgraded and it is impractical to isolate the primary conductor. A bartype current transformer which has 1 turn on its primary and 160 turns on its secondary is to be used with a standard range of ammeters that have an internal resistance of 0. December 2019 type rlc current transformer 600 volt, 10 kv bil, indoor or outdoor.
The basics of current transformers nk technologies. They are designed using top core current transformer construction. They transform high current into stan dardised values for meters. Current transformers, model 186 current transformer. Pa current transformers are filled with pcbfree transformer oil. The classification of protection current transformers follows the following.
At 5% rated current through 100%, the current transformer must maintain 0. Bartype current transformer this type of current transformer uses the actual cable or busbar of the main circuit as the primary winding, which. The circuit connection shall be made as shown figure 4. Abb complete and comprehensive range of ct current trans formers is the perfect. Current transformer white paper the basics of current transformers ratio the ct ratio is the ratio of primary current input to secondary current output at full load. Bartype cts have primary connections that boltup directly to the substation bus bars. The current transformer can be used in commercial grade applications. May 2014 type imc current transformer 600 volt, 10 kv bil, indoor. Bartype current transformer this type of current transformer uses the actual cable or busbar of the main circuit as the primary winding, which is equivalent to a single turn. Tape wound measuring and protection current transformers. Standard current transformer multiratio taps 214 burden standards 214 5 kv 36 kv indoor voltage transformers primary current class abb type geiti equivalent abb product bulletin page 2400 to. Used in ac system for the measurement of current, voltage, power and energy.
Current transformers, along with voltage or potential transformers, are instrument transformers. It produces a current in its secondary which is proportional to the current in its primary. Transformers used for voltage potential measurement steps down the voltage to the level of voltmeter. The simplest form any current transformer can take is the ring type or window type, examples of which are given in the below figure which shows three commonly used shapes i. The pa current transformers are used in electric power grids with system voltage of up to 145 kv and frequency of 50 hz. Abb library is a web tool for searching for documents related to abb products. They are fully insulated from the high operating voltage of the system and are usually bolted to the currentcarrying device.
Types kotd110, 150, and 200 current transformers medium voltage. It should be connected measuring devices before application of primary connection as seen in figure1. Protection current transformers are constructed to feed the protection relay. A current transformer ct is a type of transformer that is used to reduce or multiply an alternating current ac. Nov 15, 2019 the basic principle of the current transformer is the same as that of the power transformer. Tropicalized for cable or bar current transformer t1. Allentown, pa abstract more and more substations are retrofitted with numerical relays. It buffers the meter from experiencing excessive torques that might be.
Wound cts have a primary and secondary winding like a normal transformer. The simplest form any current transformer can take is the ring type or window type, examples of which are given in the below figure which shows three. This type of current transformer is available to measure ac currents from 100a to 600a, at 50 to 400hz. Current transformers type jof are used in high voltage networks within the 24 550 kv range. Types of transformer different types of transformer. Eaton s 5a solid core current transformer is ideal for new construction and retrofit applications where no current transformer exists. The secondary of the current transformer is portable. Unsure which of our hobut current transformer range you need. The polarity marks of a current transformer indicate that when a primary current enters at the polarity mark h1 of the primary, a current in.
Typically, the single straight line considers as primary winding. Current transformer type elk without primary conductor is designed for installation in sf6 gas insulated switchgear gis indoor or outdoor systems up to 420 kv. The secondary winding of current transformer which will not be used must always be shortcircuited and earthed as seen in figure2. Most often, the older relay gets replaced with a newer relay with the rest of the installation such as current transformer ct and lead. Schneider electrics extensive power monitoring product portfolio. Window type cts should be mounted with the h1 side of the window towards the power source. Whenever an alternating current flows through the primary winding, alternating magnetic flux is produced, which then induces alternating current in the. The basic principle of the current transformer is the same as that of the power transformer. The current transformer can be used in commercial grade applications such as control panels and panelboards, and for most industrial metering and relay applications in switchboards, switchgear, and motor control centers. The active elements are located in a hermetic housing inside the head of the transformer. Another very common type of construction is the socalled window, through or donut type current transformer in which the core has an opening through which the conductor carrying the primary load current is passed.
A current transformer can also be used as an input to a current relay or transmitter, or to reduce the current so that a current switch or transducer can be utilized. This protects connected metering devices from overloading in the presence of fault level current flows. Browse our products in tropicalized for cable or bar for current transformer t1 current transformers from 40a to 6000a. The x1 secondary terminal is the polarity terminal figure 3. The transformer is a static electric device consisting essentially of two or more windings wound on the same core electromagnetic induction transforms electric energy from one circuit to another circuit such that the frequency of the energy remains unchanged while the voltage and current usually change definition of a transformers. Here we discuss different types of transformers are the step up and step down transformer, distribution transformer, potential transformer, power transformer, 1. They are very popular in submetering applications where existing systems are being upgraded and it. Current transformers type pa 123 kv and 145 kv instrument. For the encapsulated type current transformer, the windings are enclosed in a. These transformers provide insulation against the high. Current transformer basics and the current transformer. Simply short the secondary of the ct through the sensing window of the sensor. The primary of the current transformers is considered as the line or cable or busbar of the load circuit. Instead, the line that carries the current flowing in the network is threaded through a window or hole in the toroidal transformer.
Ensure the ct is connected to system properly in all respect primary and secondary. Abb library is a web tool for searching for documents related to abb products and services. Introduction generally a transformer is an electrical device or machine which inductively transfers the electrical power operating at a particular current and voltage of one circuit to the other. Outdoorrated versions of this equipment are used in pole mounted primary metering installations. It is even possible to install this type of transformer while the conductor is energized. Current transformers are essential components designed to be used with. Secondary winding of a current transformer must not be operated with an open circuit. To confirm the physical condition and electrical characteristics of current transformer installed in the installation.
Another very common type of construction is the socalled window, through or donut type current transformer in which the core has an opening through which. The various types of transformer shown in the figure above are explained in detail below. These transformers provide insulation against the high voltage of the power circuit, and also supply the relays with quantities proportional to those of the. May 2014 type imc current transformer 600 volt, 10 kv bil. Low voltage current transformer low voltage current transformer general reference standards iec600441, vde0414441, din57414, bs3938, bs7626, en600441, gb12082009 measuring current transformers are constructed to feed on other low voltage apparatus such as measuring instruments, relays, watthour meters kw meter and these type of current. Standard current transformer multiratio taps 214 burden standards 214 5 kv 36 kv indoor voltage transformers primary current class abb type geiti equivalent abb product bulletin page 2400 to 4800 5 kv indoor viy60 ptw3160 and ptw3260 1vap429511db 148149 2400 to 72007200 8. However, the concept of knee point voltage is very pertinent to protection current transformers, since they are necessarily exposed to currents of 20 or. Current transformers 99 protective relays of the ac type are actuated by current and voltage supplied by current and voltage transformers. Basics, maintenance, and diagnostics vii contents continued page 4.
Schneider electric is the global specialist in energy management with the most complete power. This type of transformer is categorized on the basis of a number of turns in. The elk current transformers have a possibility of reconnection on the secondary side. Allentown, pa abstract more and more substations are retrofitted with numerical relays, meters and monitoring devices. This type of ct often has compensating windings which improve the accuracy across the full load range of the transformer. The bar type is inserted in the circuit to be monitored. For example, if 150 amps flow through the 300 amp rated primary, the secondary current would be 2. Perfect for low current measurement where a donut current transformer would not sense a signal download datasheet. The primary winding is connected in series with the load and carries the load current to be measured. Indooroutdoor current transformer elk cn3 instrument. Different types of transformers and their applications. If the primary current changes, the secondary current output will change accordingly. A current transformer is an instrument transformer in which the current ratio is within the specified limit. The ratio of a current transformer is equivalent to the voltage ratio of potential transformers.
The primary current of minimum of 25% rated primary. A current transformer in which the primary winding consists of a bar of suitable size and the material forming an integral part of the transformer. Like the power transformer, the current transformer also contains a primary and a secondary winding. Bar type cts operate on the same principle of donut cts but have a permanent bar installed as a primary conductor. This type of transformer is categorized on the basis of a number of turns in the primary and secondary windings and the induced emf. Instrument transformer basic technical information and. The kneepoint voltage is less applicable for metering current transformers as their accuracy is generally much tighter but constrained within a very small bandwidth of the current transformer rating, typically 1. A true bar type current transformer is a toroidal type transformer with a bus bar as an integral part of the current transformer which is permanently inserted through the window of the torroid. Current transformers pfiffner instrument transformers ltd. These are the most commonly used transformer types for all the applications.
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