# Current Transformer And Potential Transformer Theory Pdf

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## Electrical Sensors: Potential Transformers (PTs) and Current Transformers (CTs)

Hence the secondary of current transformer is never left open. Accuracy class: Metering needs high accuracy at load current while Protection need not have that high accuracy. Safety Factor: It determines the multiplicity of load current at which the CT saturates. Metering CT should have lesser value so that it saturates before the meters can get damaged due to some abnormality. Protection should have high value since its main purpose desires the CT to withstand high fault currents to be sensed back to the relays. The primary is typically the main power line conductor, which passes directly through the toroidal core. M is designation for metering.

## Instrument Transformers - CT and PT

Current Transformers CT and Potential Transformers PT are used to measure the current and voltage in a circuit of the order of hundreds of amperes and volts respectively. A CT has large number of turns on its secondary winding, but very few turns on its primary winding. The primary winding is connected in series with the load so that it carries full load current. A low voltage range ammeter A is connected across the secondary winding terminals. Secondary of the CT is practically short circuited since the ammeter resistance is very low.

From these primary variables, we may determine impedance, reactance, resistance, as well as the reciprocals of those quantities admittance, susceptance, and conductance. Other sensors more common to general process measurements such as temperature, pressure, level, and flow are also used in electric power systems, but their coverage in other chapters of this book is sufficient to avoid repetition in this chapter. Two common types of electrical sensors used in the power industry are potential transformers PTs and current transformers CTs. Electrical power systems typically operate at dangerously high voltage. It would be both impractical and unsafe to connect panel-mounted instruments directly to the conductors of a power system if the voltage of that power system exceeds several hundred volts. For this reason, we must use a special type of step-down transformer referred to as a potential transformer to reduce and isolate the high line voltage of a power system to levels safe for panel-mounted instruments to input.

The electrical instruments are not directly connected to the meters or control apparatus of high voltage for safety purpose. The instrument transformers like voltage transformer and current transformer are used for connecting the electrical instruments to the measuring instruments. These transformers reduce the voltage and current from high value to the low value which can be measured by conventional instruments. The construction of the current and potential transformer is similar as both have the magnetic circuit in their primary and secondary winding. But they are different in the method of working. There are several types of differences between the voltage and the current transformer.

## Difference between Current Transformer and Potential Transformer

Current Transformers CT and Potential Transformers PT are used to measure the current and voltage in a circuit of the order of hundreds of amperes and volts respectively. A CT has large number of turns on its secondary winding, but very few turns on its primary winding. The primary winding is connected in series with the load so that it carries full load current. A low voltage range ammeter A is connected across the secondary winding terminals. Secondary of the CT is practically short circuited since the ammeter resistance is very low.

Recieve free updates Via Email! Home Electrical machines Power system Ask a question Contact electricaleasy. Share: Facebook Twitter Linkedin. Instrument Transformers How will you measure AC currents and voltages of very high magnitude? You will need the measuring instruments having higher range, which literally mean huge instruments.

Free download application of potential transformer pdf. 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. 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 watt-hour meters, etc. The potential transformers and accessories covered by this specification shall comply with the requirement of the latest edition of the following standards unless otherwise stated in this specification: IS: Part I-IV : Specification for Voltage Transformer.

Кокетка до мозга костей, трижды разведенная, Мидж двигалась по шестикомнатным директорским апартаментам с вызывающей самоуверенностью. Она отличалась острым умом, хорошей интуицией, частенько засиживалась допоздна и, как говорили, знала о внутренних делах АНБ куда больше самого Господа Бога. Черт возьми, - подумал Бринкерхофф, разглядывая ее серое кашемировое платье, - или я старею, или она молодеет.

Танкадо мертв. Партнер Танкадо обнаружен.

Кольца на пальце уже не. ГЛАВА 118 - Это может служить доказательством, - решительно заявил Фонтейн.  - Танкадо избавился от кольца. Он хотел, чтобы оно оказалось как можно дальше от него - чтобы мы его никогда не нашли.

Сьюзан стояла прямо и неподвижно, как статуя. Глаза ее были полны слез. - Сьюзан. По ее щеке скатилась слеза.

Он задумал способствовать распространению алгоритма, который АНБ с легкостью взломает. - Полный и всеобщий доступ, - объяснял Стратмор.  - Цифровая крепость сразу же станет всеобщим стандартом шифрования. - Сразу же? - усомнилась Сьюзан.

Сьюзан едва заметно кивнула: - Он требовал, чтобы мы сделали признание… о ТРАНСТЕКСТЕ… это стоило ему… - Признание? - растерянно прервал ее Бринкерхофф.  - Танкадо требует, чтобы мы признали существование ТРАНСТЕКСТА. Но он несколько опоздал.

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