What is PT in substation?
Answers
Answer:
A Potential transformer is actually a instrument transformer that used in power systems to step down primary current voltages and secondary voltages from a higher level to lower secondary potential output voltage level.
Answer:
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.
Explanation:
The potential transformer is mainly classified into two types, i.e., the conventional wound types (electromagnetic types) and the capacitor voltage potential transformers.
Conventional wound type transformer is very expensive because of the requirement of the insulations.Capacitor potential transformer is a combination of capacitor potential divider and a magnetic potential transformer of relatively small ratio.
The circuit diagram of the capacitor potential transformer is shown in the figure below. The stack of high voltage capacitor from the potential divider, the capacitors of two sections become C1 and C2, and the Z is the burden.
capacitor-potential-transformer-circuit-diagram
The voltage applied to the primary of the intermediate transformer is usually of the order 10kV. Both the potential divider and the intermediate transformer have the ratio and insulation requirement which are suitable for economical construction.
The intermediate transformer must be of very small ratio error, and phase angle gives the satisfactory performance of the complete unit. The secondary terminal voltage is given by the formula shown below.
capacitor-transformer
v2=v1× C1/c1+c2
Ratio and Phase Angle Errors of Potential Transformer
In an ideal potential transformer, the primary and the secondary voltage is exactly proportional to the primary voltage and exactly in phase opposition. But this cannot be achieved practically due to the primary and secondary voltage drops. Thus, both the primary and secondary voltage is introduced in the system.