What is the ratio of potential transformer?
Potential Transformer ratio is the ratio of the primary rated voltage of the PT divided by the secondary rated voltage of the PT. A 480:120V rated PT will have a PT ratio of 4.
How do you calculate Pt ratio?
You can determine the PT ratio by dividing the phase-to-phase voltage, which is 4,160V, by the voltmeter full-scale range, which is 150V. This simple calculation results in a value of 27.7, which you would interpret as an approximate 28:1 ratio.
What is ratio test of potential transformer?
The transformer turns ratio test is used to determine the number of turns in one winding of a transformer in relation to the number of turns in the other windings of the same phase of the transformer. The transformer polarity test determines the vectoral relationships of the various transformer windings.
What is the ratio of voltage transformer?
VR = TR. A voltage ratio of 1:5 means that for each volt on the primary, there will be 5 volts on the secondary. If the secondary voltage of a transformer is greater than the primary voltage, the transformer is referred to as a “step-up” transformer.
What is CT ratio and Pt ratio?
CT is used to measure current while PT is used to measure voltage. CT is connected in series while PT is connected in parallel. CT ratio range is from 1 to 5A while the PT range is from 110V.
What is a PT potential?
A potential transformer (P.T.) is an instrument transformer which is used for the protection and measurement purposes in the power systems. A potential transformer is mainly used to measure high alternating voltage in a power system.
How do I choose a potential transformer?
How do we select the proper voltage transformer for a given…
- Rated primary voltage(s) or insulation level Ur/Ud/Ui in kV.
- Rated secondary voltage(s).
- Rated frequency (e.g. 50 or 60Hz).
- Earthing system (isolated or not).
- Desired accuracy class in measurement chain (e.g. class 1, 0.5 …etc).
What are the errors of PT?
Errors in Potential Transformers In potential transformers, the voltage drops due to the reactance and resistance in primary and secondary and also the power factor on secondary causes phase shift errors and voltage errors.
What is a potential transformer?
Voltage transformers (VT), also called potential transformers (PT), are a parallel-connected type of instrument transformer. They are designed to present a negligible load to the supply being measured and have an accurate voltage ratio and phase relationship to enable accurate secondary connected metering.
What is the voltage ratio formula?
A change in voltage, from V1 to V2 can be expressed as a ratio in decibels with the equation RV = 20*log(V2 / V1). A doubling in the voltage level translates to a power ratio of 6 dB. Similarly, halving the power equals a -6 dB voltage ratio.
What is nominal ratio of transformer?
In instrument transformers, the nominal ratio is the ratio of rated primary winding quantity to the rated secondary winding quantity. In current transformers, nominal ratio = rated primary current/rated secondary current. In potential transformers, nominal ratio = rated primary voltage/rated secondary voltage.
How is CT PT ratio calculated?
PT’s and CT’s step down the line currents and voltage to much safer levels. To connect to these circuits, we need to know the step-down ratio. Voltage is a simple division answer, simply divide a 1:1 PT ratio value into the known line voltage; For example; 4160 / 120 = 34.66 or 35:1.