The use of coupling capacitor voltage transformers ccvts for revenue metering applications is limited to 500 kv and above. Metering current transformers cts are used with the measuring instruments, such as ammeters, voltmeters, kilowatthour meters, etc to. The lake shore electric utility metering transformer cabinet provides the solution. Ae specification e0746 pdf requirements for 5th terminal lugs in meter socket.
Metering class current transformers dd 8619page 1 of 1 accurate to 0. 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. Current transformers technical datasheet schneider electric is the global specialist in energy management with the most complete power monitoring product line. Multiple conductors electrically connected to the same point with reference to the meter will be considered one point of delivery. These splitcore current transformers allow for easy installation, retrofit, and service. Medium voltage instrument transformers ritz instrument. Make better business decisions with scalable and converged itot solutions. Low voltage current transformers comprehensive metering grade ct offering spiltcore, flexible and solid core designs siemens instrument grade current transformers ct have a splitcore construction and provide a safe 5a secondary output. Data sent by current transformers are processed by protection, control and monitoring units that send signals to operate switchgear andor information to a supervisory unit or to a central control room. Reach out to our customer team in your country or region if you have any. Selecting ansi class metering current transformers 142 h b0. Tape wound measuring and protection current transformers. Ecostruxure lets you thrive in todays digital world. Scope this document describes the calculation of the actual accuracy limit factor f a for protectiontype p current transformers ct.
Abb range of current transformers are designed to be part of metering systems, where they are used to allow indirect meas uring of electrical parameters of the. Utilitycurrent t ransformer metering this enclosure is assembled with the test switch installed at a factory offset distance from the cover see figure 1. This protects connected metering devices from overloading in the presence of fault level current flows. Calculation of the current transformer 1mrs 755481 accuracy limit factor 1. Within the meter box, each wire coupled with a metering 2,756,399 patented july 24, 1956 connection is included in the primary winding of a metering current transformer, the output of which is fed to an associated meter. Open ended loomharness ct fixedopen at meter connection. Current transformer metering ct metering overview b. In practice, it becomes necessary for timetotime, to remove such transformers for repairs, inspections and periodic. Current transformer metering crescent electric supply.
Product features ul 414 listed 100% rated copper bus. Current transformers,voltage transformers and instrument. A fault current is 10 times more than the usual full load curren. The basics of current transformers nk technologies. Connecting too low a burden compared to the design burden of the current transformer will allow higher currents through the metering. Comprehensive metering grade ct offering spiltcore. Choosing your standard industrial current transformer. When current flow exceeds that rating, the metering core will become saturated, thereby limiting the amount of current level within the device. While the latter configuration would not be used today, one may be required to make this calculation on an existing system. Revenue metering applications involving installations served from 60 kv through 230 kv require the use of combination metering units ptct. Nonmetered loads customer owned conductor terminations nearest to the aep owned conductor terminations. Metering current transformers are designed to be within quite accurate values up to say two x rated current, and down to utilitycurrent transformer metering 400800 amp50k aicbussed current transformer mounting base 7 utilitycurrent t ransformer metering application ul 414 listed, complies with ansi c12.
Ritz offers 600v current and voltage transformers for utility customers. Calculation of the current transformer accuracy limit factor. Current transformers are essential components designed to be used with schneider electrics extensive power monitoring product portfolio. Similarly, current transformers take a high current and reduce it to typically 5 amps. Three metering accuracy classes are defined for instrument transformers. We have over 40 years of experience with manufacturing metering current transformers of various specifications for customers all over the globe. Browse all current transformer metering pricing and availability for your job or project. Ansi and ieee standards for metering pjm interconnection. Current transformers cts can be used for monitoring current or for transforming primary current into reduced secondary current used for meters, relays, control equipment and other instruments. The matching of cts with protection relays calls for a thorough knowledge of current transformers. Isolate the instruments from the power circuits, standardise the instruments, usually at 5 amps or 1 amp. The new current transformer and metering speci cations like the iec618692 table above now require accuracies from 0. It does so in a predictable and proportionate way, allowing for the accurate measurement of the total current to be.
Some current transformers have secondary windings dedicated to protection and metering. 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. Cts that transform current isolate the high voltage primary. In the past, current transformers were designed to accurately measure down to 10% of the current rating on the name plate of the transformer. An opensecondary protection device is available separately. Eatons bline series current transformer metering product line includes ct rated meter sockets, ct enclosures, ct mounting bases, combination ct enclosure meter sockets, test switches and transockets that are designed to meet customers needs in a variety of applications, and are suited for many utility specifications. What is the difference between metering and protection ct. The task, consisting of identifying and rating the current transformers and associating them with the protection andor metering units, has always. Current transformers are commonly used in metering and protective relays in the electrical power industry. These instrument and protection cts are governed by standard iec 600441 in france nf c 42502. Slipover bushing cts are also available for mounting.
Ge is an industry leader in the design and manufacturing of high, medium and low voltage instrument transformers. First, the calculation of the actual burden of the ct, including connection wires and protection relay impedance, is presented. Whereas the basic purpose of the protection ct is to provide protection in case of any fault. Current transformers are available in dry type or watercooled with a center hole for bus bar or cable. Current transformer basics and the current transformer. Instrument transformers are used for measurement and protective application, together with equipment such as meters and relays. Loosen and remove the screws holding the perch to the bracket, remove the perch. The model 190xsum is a summing transformer for use when two, three, four, or.
Construction ringless cover type 3r construction 16 ga. The scale of the instrument according to the ct ratio, then becomes the only nonstandard feature of. A metering ct carries the full load current and are designed near the saturation point. A metering transformer, also known as an instrument transformer, can be used where the circuit current is too high to deploy measuring or metering instruments directly.
If you require more information on measuring class, please refer to our guide pdf. If a greater offset is desired, follow these instructions. A metering core is designed to work more accurately within the rated current range designated. Current transformers potential voltage transformers typically, services over 400 amps are required to have a conforming enclosure to house utility provided metering current transformers. A current transformer isolates the measuring instruments from what may be very high voltage in the monitored circuit. Current transformers come in window, bar, and woundprimary designs for use in metering or protection applications. Instrument transformer basic technical information and. The metering transformer reduces the current to a level that those instruments can safely handle. In order to minimize the number of 90 degree bends maximum of 3 per the. High accuracy extended range current transformers can increase utility revenue through improved metering. This occurs on systems with variable currents such as wind or solar power generation. Current transformers and power line transformers for smart metering. Us2756399a mounting for metering current transformers.
Optimum current transformers for smart metering oct 2015 2. Supreme accuracy current transformer super accuracy for 0. Current transformers are used to supply information to the protective relays andor current, power and energy metering instruments. With more than 100 years of experience, ge offers a broad array of standard and high accuracy models for revenue metering and system protection applications. Can i use same current transformer for metering and. Current transformers reduce high voltage currents to a much lower value and provide a convenient way of safely monitoring the actual electrical current flowing in an ac. These have to be very carefully filtered and amplified to keep the meters specified accuracy in the low current level.
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