The Secondary Circuit Voltage Drop Mechanism Of Voltage Transformers And Improved Schemes

Because the PT secondary loop voltage drop directly affects the accuracy of the electric energy measurement. After consulting a great amount of materials, the best method to reduce the PT secondary loop voltage drop was put forward based on analyzing the cause of which.First of all, the cause of PT secondary loop voltage drop was analyzed and the conclusions were draw as below:1. The PT secondary loop voltage drop equals to the product of the PT secondary loop impedance and the loop current.2. The PT secondary loop impedance is divided to the elements self impedance and the contact impedance. The contact impedance takes the dominant part, so the PT secondary loop impedance has the dynamic characteristics and certain randomness.3. The PT secondary loop current is correlated with the loop impedance, therefore the secondary loop current is varied too.4. The PT secondary loop voltage drop is a changing amount and has the characteristics of indirection and certain randomness.The second, according to the cause of PT secondary loop voltage drop, the different methods to reduce the PT secondary loop voltage drop were analyzed and the conclusions are draw as below:1. Changing bigger section wire and maintaining the connector plugs regularly can reduce the PT secondary loop voltage drop effectively, but can't guarantee which meets the relevant rules.2. The separation of the protection loop and measurement loop can reduce the PT secondary loop current effectively, but can't guarantee which meets the relevant rules.3. The fix value compensator and the current follow compensator has the inherent limitation and will cause the overcompensation, so they can't be used in secondary loop voltage drop compensation.4. Voltage follow compensator combined the voltage vector sampling and amplitude self-adaptive can improve the high accuracy results and guarantee the secondary comprehensive voltage has the indirection characteristics and meet the relevant rules.The third, according to the analyzing result above the experiments were carried out and it proved that the voltage follow compensator has the characteristics of high accuracy and error indirection.