The conductor on which the transformer is mounted will act as primary windings of the current transformers. Make better business decisions with scalable and converged itot solutions. Type v current transformers vertical bar profile internal profile type cables mm bars mm rating ip5 a a commercial reference number vv 55 x 165 5000 metsect5vv500 g 6000 metsect5vv600 g type d current transformers vertical or horizontal bar dual secondary terminals da 32 x 65 400 metsect5da040. Window type bar type wound x 1 x2 x3x4x5 20 10 50 40 600. A current transformer is an instrument transformer, used along with measuring or protective devices, in which the secondary current is proportional to the primary current under normal conditions of operation and differs from it by an angle that is approximately zero. By far, the most common one is the wound type current transformer.
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. It transforms the high voltage current into the low voltage current due to which the heavy current flows through the transmission lines is safely monitored by the ammeter. The basics of current transformers nk technologies. A current transformer, abbreviated ct, is a type of transformer used to measure the current of a given circuit. At 5% rated current through 100%, the current transformer must maintain 0. They are fully insulated from the high operating voltage of the system and are usually bolted to the current carrying device. Suitable for operating meters, instruments and control devices. Testing polycast testing capabilities include polarity, ratio and. Schneider electrics extensive power monitoring product portfolio. By adding secondary turns, the same primary current will result in a decrease in secondary output. The correct way to specify and install current transformers. Current transformers,voltage transformers and instrument. They are fully insulated from the high operating voltage of the system and.
Efficiency ratings of low voltage dry type distribution transformers singlephase1 1 singlephase ventilated transformer efficiencies remain the same as the 2007 levels. Defining the transformer type with focus on fitting when the primary current is very low, a few amps to a few tens of amps, a wound primary transformer is preferably used. We always recommend current transformers with the same precision class for the umg measuring devices. Allentown, pa abstract more and more substations are retrofitted with numerical relays, meters and monitoring devices. 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. Scribd is the worlds largest social reading and publishing site. A current transformer operates with a set primary current and will try to output a constant current to the load, independent of the load. Current flows as if there is a physical connection. Medium voltage mv indoor current transformer bar primary. The term dead and live has their own meaning from the view point of potential of secondary windings and core. The new type ex energy efficient low voltage dry type distribution transformers comply with the new levels of efficiency. To check pricing and availability for a specific current transformer model, give us a call at 614 8896152 or use our quote request form. 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. It is high operating voltage which has been bolted to current carrying device.
Nominal primary current ip a number of secondary windings 1 to 3 for each secondary winding. The rated burden of this type is higher than the type ib. This type of ct often has compensating windings which improve the accuracy across the fullload range of the transformer. American national standard for instrument transformers for.
The primary of the current transformers is considered as the line or cable or busbar of the load circuit. You can also choose from single, three bar type current transformer there are 688 suppliers who sells bar type current transformer on, mainly located in asia. The iron core inside the transformer is magnetized. Utility metering transformer cabinet lake shore electric. Bar type current transformers have terminals for source and load connections of the primary circuit, and the body of the current transformer provides insulation between the primary circuit and ground. Current transformer safety precautions safety precautions care must be taken that the secondary of a current transformer is not disconnected from its load while current is flowing in the primary, as the transformer secondary will attempt to continue driving current across the effectively infinite impedance. Typically, the wound type is insulated to only 600 volts. Difference between dead tank and live tank ct electrical. Current transformer, simplified equivalent circuit. Instrument transformer basic technical information and.
We use three types of current transformers that come in all sizes. Bar type current transformers include a permanent bar that operates as 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. The product range comprises of current transformers up to 33kv and voltage transformers up to 22kv for use. Schneider electric is the global specialist in energy management with the most complete power.
Current transformers are essential components designed to be used with. The bushing type is typically used around the bushing on circuit breakers and transformers and may not have a hard protective outside. Window type cts should be mounted with the h1 side of the window towards the power source. The most common ct secondary full load current is 5 amps which matches the standard 5 amp full scale current rating of switchboard indicating devices, power metering equipment, and protective relays. The current transformer is designed to connect in series with the line to transform the line current to the standard 5 amperes suitable for the. With 150 amps through the 300 amp rated primary, the secondary current will be 2. Below is a list of all current transformers available through flexcore, however, not all models are instock. The current transformer will operate into either a short circuit or a resistive load until the voltage induced is enough to. Apr 25, 2017 the current transformer the current transformer c. The secondary circuit of a current transformer must not be operated opencircuited 3.
Read more difference between dead tank and live tank ct. Bartype current transformer the bar type transformer has only secondary windings. Since the load current passes through primary windings in the ct, screw terminals are provided for the load and secondary conductors. Bar current transformers of type jld are used in indoor and outdoor applications for medium or high voltage systems. Ktf values required in practice depend on relay type and design. To correctly measure current, the ct has to be able to wrap around the entire conductor of the current being measured. When current flows through the primary winding, the following actions occur. A wide variety of bar type current transformer options are available to you, such as power, current, and instrument. Stemars works are fully equipped to manufacture and test current transformers to any specified standard with primary currents up to 20000 amps and secondary currents up to 10amps. Current electric was established in 1982 and is the leading manufacturer of current and voltage transformers in south africa, in june 2008 the business was acquired by actom group previously known as alstom electrical industries. Window type transformers, where the primary conductor is a cable or a bar passing through the transformer, are used when the currents to be measured are above 150a. Typically, the single straight line considers as primary winding.
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. By use of oil insulation and porcelain bushings, such transformers can. Wound primary current transformers are recommended where high accuracy is required at a lower ratio 55a through 3005a typically. They are very popular in submetering applications where existing systems are being upgraded and it is impractical to isolate the primary conductor. 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. Current transformers measurementmetering protection. Selecting current transformers janitza electronics. What is the working principle of a current transformer. Toroidal current transformer this transformer does not contain primary windings. Current transformers gifu 2501 larger unit for protection and metering current transformers gifu 2503 lighter unit for metering only current transformers. Excellent measurement technology requires highquality current transformers. It is available in five internal window diameter sizes and dual and multiratio designs are available upon request. For the transformer with reconnectable andor tapped secondaries, unused terminals must be left open as seen in figure ct.
Nov 15, 2019 a current transformer is an instrument transformer, used along with measuring or protective devices, in which the secondary current is proportional to the primary current under normal conditions of operation and differs from it by an angle which is approximately zero. Apr 18, 2020 suppose, you have one current transformer with current ratio 4001 a and its protection core is situated at 500 a. Current transformers cts have long been a vital component in high voltage transmission and distribution networks. The current transformer is designed to connect in series with the line to transform the line current to the. Types of transformer different types of transformer. The line through which the current flow in the network is. The secondary of the current transformer is portable. The magnitude of the secondary current is dependent on the turns ratio of the transformer. Accessories ac current transformer max 30x10 mm busbar. Relays are required to perform in fault current type situations.
The scg current transformer is used as the source of current for relaying and metering. Current transformers are available at mouser electronics. Abb type geiti equivalent abb product bulletin page 50 to 2. Ansi instrument transformers for medium voltage outdoor. Current transformers are classified as dead tank type and live tank type cts based on their construction. Apr 16, 2011 the most common one is the wound type current transformer. The main role of current transformer for which it is highly known is providing the current adjusted according. Utilitycurrent transformer metering cooper industries. Current transformer design guide an effective design of a ring type c. One ct also buzzed a little, so i wiped off the mating ends of. The product portfolio comprises a wide range of current transformers for load currents operating currents and residual currents rcm. The wound type provides excellent performance under a wide operating range. The classification of protection current transformers follows the following. Current transformer basics and the current transformer.
Simply short the secondary of the ct through the sensing window of the sensor. Medium voltage current transformers bar primary bushing type ttr are cast in epoxy resin and are designed for installation voltage up to 24 kv 25 kv. Oct 24, 2014 bar type current transformer the cable or bus bar of main circuit has been used in bar type current transformer as the primary winding. Bar types are available with higher insulation levels and are usually bolted to the current caring device. Today there is a new generation of nonconventional cts ncits that overcome many of the shortcomings of traditional designs. If the primary current of the current transformer becomes a the secondary current will still be 1. Bar and donut type cts do not have a physical primary winding and are considered to have one primary turn.
Surplus sales of nebraska carries a large variety of sizes and older hard to find current transformers in stock, ready to ship today. Square d brand ex low voltage distribution transformers. Cts with a 1 amp fullload value and matching instruments with a 1 amp full. Instrument transformers convert signal levels from dangerous high voltage or inconvenient high current, or current at high voltage to levels appropriate for metering. In bar type cts, the primary winding has only one turn that means the conductor itself acts as primary winding. Ansi outdoor medium voltage transformers are encapsulated in hydrophobic cycloaliphatic epoxy hcep using the automatic pressure gelation apg process. The ratio of the current transformer can be modified by altering the number of secondary turns by forward or backwinding the secondary lead through the window of the current transformer. Primary current secondary current option ordering key cablebus bar type current transformer with dinrailbus bar and panel mounting facility. Current transformers ratio polarity types educypedia. Cts with a 1 amp fullload value and matching instruments with a 1 amp full range value are also available. Cts current transformers pts potential transformers. Current transformer latch is a little uncertain so squeeze the assembly firmly once clamped around the monitored feed line.
Current and voltage transformers are available in voltage classes ranging from 5 kv to 34. Jun 02, 2015 the primary winding of the current transformer consists of one or more turns having a heavy cross sectional area and is connected in series with the circuit in which the current flow is to be sensed. National electrical manufacturers association approved november 6, 2007 american national standards institute, inc. American national standard for instrument transformers for revenue metering 10kv bil through 350 kv bil 0. Current transformers for residual current and load current.
Current transformers measure the current of a single conductor passing through its center. Accessories ac current transformer max 30x10 mm bus bar type ctd2x type selection input specifications operating frequency 45 to 65 hz max. The primary winding of the current transformer consists of one or more turns having a heavy cross sectional area and is connected in series with the circuit in which the current flow is to be sensed. Reach out to our customer team in your country or region if you have any. Suitable for operating meters, instruments, relays and control devices. 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. Low voltage current transformers low voltage switchgear and general purpose primary current. Splitcore current transformers this type of current transformer is available to measure ac currents from 100a to 600a, at 50 to 400hz. This type of transformer is categorized on the basis of a number of turns in the primary and secondary windings and the induced emf. For the encapsulated type current transformer, the windings are enclosed in a compact and heat resistant split cap. Dead tank itself means that the potential of the tank of ct is at earth potential i. Cable current transformers pfiffner instrument transformers ltd.
Application guide to selecting current transformers. Utility metering transformer cabinet introduction lake shore electric metering transformer cabinets are ul listed and utility company compliant. 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. Chapter 16 current transformer design university of north. The secondary winding of a current transformer which will not be used must always be shortcircuited and earthed as seen in figure ct2 4. Ecostruxure lets you thrive in todays digital world. Current transformer metering ct metering overview b. Typically, larger amounts of electricity require larger wires, so its important to keep window size in mind. Accurate, easy to install and use, perfectly adaptable with any type of system. By subtracting turns, the same primary current will result in. They are fully insulated from the high operating voltage of the system and are usually bolted to the currentcarrying device. When the rated primary amps is exceeded, which is usually the case when a fault occurs on the system, the amount of secondary current will increase. 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 are divided into 2 major categories.
Construction features the ring type core is insulated and toroidally wound with a fully distributed secondary winding. Current transformer ct construction and working principle. Abb oem instrument transformer reference guide april 2014. The x1 secondary terminal is the polarity terminal figure 3. The current transformer function is different than that of a voltage transformer. In this video you will learn about what is current transformer, important concepts of current transformer, how current transformer work, use of current transformer. General index guide 600 volt current transformers primary current window diameter in.
Instrument transformers are used for measurement and protective application, together with equipment such as meters and relays. The various types of transformer shown in the figure above are explained in detail below. Bar type current transformers are installed in place of removable links standard cabinets have split, hinged doors with removable center post. Coupled with an ammeter, cts are used to protect the main lines of the power grid, by measuring highvoltage electrical current and preventing damage to sensitive equipment. A current transformer is a device that is used for the transformation of current from a higher value into a proportionate current to a lower value.