What is S in accuracy class?
An accuracy class of 0.2 s means that the measurement has an error rate of 0.2% ranging from 20 to 120% of the nominal current (In) and with a specified accuracy above 1% In.
What is the difference between class 0.5 and 0.5 S CT?
As you can see from the table above, a class 0.5 system typically has 1.6% accuracy, which is not enough. Class 0.5S system has an accuracy of 1.1%with HACS (or direct link) 0.6% accuracy – almost three times better!
What does CT class mean?
The class designation is approximate measure of the accuracy of a current transformer. The ratio error (primary to secondary current) of a class 1 current transformer is 1% at the rated current; class 0.5 current transformer error is 0.5% or less. Phase errors are also important, especially in power measurement circuits.
What is the accuracy class of the CT?
Current transformer accuracy class
The accuracy class or simply the class of the measuring current transformer is 0.1, means the maximum permissible error limit is 0.1%more clearly, if we try to measure 100A with a 0.1 class current transformer, the measured value can be 100.1 or 99.9A or whatever between these ranges.
What is 0.2S CT?
0.2 and 0.2s refer to accuracy of the current transformer. CT 0.2S has a much higher accuracy than 0.2. Accuracy class 0.2 means error +/- 0.2%. But the declared accuracy is only guaranteed between 100% and 120% of the rating.
What is the PX class in CT?
The PS CT class is also known as the PX class or simply Class X current transformer. It is a special type of current transformer intended for protection purposes. The different protection classes of the current transformers as described in IS 2705 Part 3 are only suitable for overcurrent protection.
How to choose the CT ratio?
The correct selection of the primary rated current is of great importance for the accuracy of the measurement. It is recommended ratio slightly above the measured / defined maximum load current (In). Example: In = 1154 A; the selected transformer ratio = 1250/5.
How do you read the CT score?
The CT ratio is ratio of primary current input to secondary current output at full load. For example, a 300: 5 current transformer is rated for 300 primary amps at full load and will produce 5 amps secondary when 300 amps pass through the primary winding.
What are the different classes of computed tomography?
CT class
| Accuracy class | ± Percentage error of the current (ratio) in percent of the rated current shown below | ± Phase shift as a percentage of rated current shown below |
|---|---|---|
| 0.1 | 0.4 | 0.24 |
| 0.2 | 0.75 | 0.45 |
| 0.5 | 1.50 | 1.35 |
| 1.0 | 3.0 | 2.7 |
How do you read the CT nameplate?
CT ratio: 100 / 5-5 AND
A 100/5 ratio means that if the primary CT has a current of 100 amps, the output of the secondary CT will be 5 amps. Double 5-5 A means the first core used for protection and the second core used for measurement purposes.
What class of current transformers is preferred for differential protection?
PS class current transformers they are used for differential protection. Differential protection is also called zone or unit protection.
What is the CT Assessment Factor?
The basic formula for a current transformer increase of 55 ° C is: The Rated Factor (RF) is a term that refers to a current transformer. … It is very important to consider the ambient temperature when using CTs above the rated value. Typical CT assessment factors are 1.0, 1.25, 1.33, 1.5, 2.0, 3.0 and 4.0.
What is the use of CT in current measurements?
A current transformer (CT) is used to measure the current of another circuit. Current transformers are used all over the world to monitor high voltage lines in national power grids. The current transformer is designed to produce an alternating current in the secondary which is proportional to the current measured in the primary winding.
What is VK in CT?
According to IEC, the voltage at the knee point of a current transformer is defined as the voltage where a 10% increase in the secondary voltage of the current transformer results in a 50% increase in the secondary current.
What is CT saturation?
Saturation of CT
When the primary current is so high that the core can no longer withstand the fluxCT is said to be saturated. In saturation, there is no flux change when the primary current changes (because the core already has the maximum flux). Since there is no flux change, there is no secondary current flowing.
What is CT ratio and Pt ratio?
The voltage transformers operate on the same premise as the current transformers in that they bring the higher voltages down to utility levels. Most PTs have a secondary voltage of 120 volts. A PT with a ratio of 4: 1 would take the voltage down from 480 volts to 120 volts. … The installed current transformer has a factor 400: 5 and PT is 4: 1.
How to calculate CT current?
The The ratio of the current transformers is the reciprocal of the voltage ratio. In this example, the voltage ratio is 1: 5, so the current transformers ratio is 5: 1. This means that the current level is stepped down 5 times, where if the primary current is 200 amps, the CT output is 40 amps.
What is CT excitation?
The excitation curve of the act is a measure of steady-state performance. The excitation curves have a voltage at the break point defined by a 45 ° line drawn tangent to the curve. Note, however, that the knee point is the point of maximum transmittance, not the saturation point.