The knee point is defined as the voltage at which a 10% increase in applied voltage increases the magnetizing current by 50%. For voltages greater than the knee point, the magnetizing current increases considerably even for small increments in voltage across the secondary terminals.
Why is Kneepoint important?
CT Magnetization Curve
The knee point is an important parameter for CT selection for a particular electrical installation. The knee point indicates the CT saturation point on the magnetization curve or B-H curve.
What is meant by the term knee voltage with respect to a CT?
Knee point voltage of a current transformer is the magnitude of secondary of current transformer. After or beyond this voltage the linearity between primary and secondary circuit that is the desired property of Current transformer does not work any more.
What is mean by key point voltage?
If we recall the definition of Knee point voltage, the value of voltage at which when the applied voltage is increased by 10 percent, causes the exciting current to increase by 50 percent.
What does 5P10 mean in CT?
If you see the specification or name plate of a protection class CT, you will find that it is given like 5P10. This CT can be interpreted as a protection class CT having an accuracy of 5% over a current range of 10 times of normal primary current rating.
In which type CT knee point voltage is mandatory?
Knee Point Voltage of Current Transformer is of importance in Protection Class CT i.e. where CT is used for protection purpose. Protection Class CT is normally specified as PS (Protection Special). PS is defined by knee point voltage of current transformer Vk and excitation current Ie at Vk/2.
What is compression knee point?
Among several WDRC factors, the compression threshold (CT), or “knee point,” is defined as the point where compression function starts in the nonlinear mode [1,2]. In this concept, CT is the first stage and critical for effectively providing nonlinear characteristics of the state-of-the art HA.
What happens after knee voltage?
Once the light-emitting diode is connected to an external voltage in the forward bias, the potential barrier height across the PN junction will be decreased. This exact voltage is known as the knee voltage of the LED. When this voltage is achieved, then the flow of current may raise however the voltage does not vary.
What is knee voltage and breakdown voltage?
The forward voltage at which the current through the junction starts increasing rapidly, is called the knee voltage or cut-in voltage. The reverse voltage at which P-N junction of a diode breaks down with sudden rise in reverse current is known as break down voltage.
What is cut in voltage or knee voltage?
Cut in voltage (Knee voltage):
The voltage at which the forward diode current starts increasing rapidly is known as the cut in voltage of a diode. The cut in voltage is very close to the barrier potential. Cut in voltage is also called as knee voltage.
How do you calculate knee voltage from a graph?
In the forward region of the graph, the voltage at which the current starts to increase quickly is called the knee voltage of the diode. Study of a diode circuit usually comes down to determining if the diode voltage is higher or lower than the knee voltage.
What is the difference between PS class and 5P20 CT?
the accuracy of PS class is not defined. generally used for unit protections differentials…. And a 5P20 CT means it will give a +_5% error when it reads 20 times the rated current …which means when a fault happens more than the CT ratting upto 20 times it can measure with a 5% errors with plus minus…
How do you test a knee point on a CT?
Excitation tests are performed by applying an AC voltage to the secondary winding of the CT and increasing the voltage in steps until the CT is in saturation. The “Knee” point is determined by observing a small voltage increase causing a large increase in current.
Which is better 5P10 or 5P20?
Its application which differetiate the use of 5P10 and 5P20. If the breaker is used for backup protection say incommer etc you can use 5P20, but if it is say an incommer ACB/ MCCBof PMCC, you should use 5P10 only.
What does 5P10 for a CT of 100 5 mean?
Similarly 5P10 can be explained as CT will sense the current with the specified accuracy of 5% even with 10 times of its secondary current flows in the secondary.
What is 0.2 S Class CT?
An 0.2s accuracy class means that the measurement has an error rate of 0.2% over a range of 20 to 120% of the nominal current (In) and at a specific accuracy above 1% of In.
What is difference between metering CT and protection CT?
The burden of protection CTs is quite high when compared with a metering class CT, which means that voltage drop across the burden will be high. Therefore, the knee point voltage of a protection class CT must be more than the voltage drop across the burden to maintain the CT core in its linear zone.
What is the class of CT?
CT Class
| Accuracy Class | ±Percentage Current (Ratio) Error at Percentage of Rated Current Shown Below | ±Phase Displacement at 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 |
What is PS in CT?
So for choosing CT for differential protection of transformer, one should consider current transformer PS class rather its convectional protection class. PS stands for protection special which is defined by knee point voltage of current transformer Vk and excitation current Ie at Vk/2.
What are normal bone conduction thresholds?
Bone conduction thresholds should be between 0–25 dB in the range of frequencies 500 Hz and 4,000 Hz. Any air conduction thresholds are acceptable, because ADHEAR relies on bone conduction. Temporary or chronic conductive hearing loss.
What is peak clipping audiology?
When the sum of the input level and gain exceed the maximum output of the hearing aid, however, the peaks of the output signal are clipped at the maximum output (Figure 1-12B). This is referred to as peak clipping.
Contents