Price of 600A/1000V Transformer Comprehensive Tester

Price of 600A/1000V Transformer Comprehensive Tester-Error Curve Explanation

The data of the 5% and 10% error curves between the current multiple (M) calculated based on the excitation current and voltage on the secondary side of the transformer and the allowable secondary load (ZII) can also be used to determine whether the transformer protection winding is qualified:

1) If the actual load measured near the theoretical current multiple is greater than the theoretical load value on the transformer nameplate, it indicates that the transformer is qualified

2) The actual current multiple measured near the theoretical load is greater than the theoretical current multiple on the transformer nameplate, which also indicates that the transformer is qualified

The secondary load of the protective current transformer should meet the requirement of a 5% error curve. As long as the actual secondary load of the current transformer is less than the load allowed by the 5% error curve, the measurement error of a qualified current transformer is within 5% at the rated current multiple. The larger the secondary load, the easier it is for the iron core of the current transformer to saturate, and the smaller the allowed current multiple. Therefore, the 5% error curve, also known as the n/ZL curve, is shown in Figure 9 (please consult customer service for instructions). In the example shown in Figure 38 (please consult customer service for instructions), the measured protective CT is 5P10 20VA: where 5 is the accuracy level (error limit of 5%), P is the transformer form (protection level), 10 is the accuracy limit coefficient (10 times the rated current), and 20VA represents the rated secondary load (capacity). When the current multiple is 10.27 times (close to 10 times), the allowable secondary load is 27.19 Ω, which is greater than the rated load of the CT by 20VA (20VA/1=20 Ω). This data can be used to determine that the transformer is qualified. In addition, when the secondary load is 19.58 Ω (close to 20 Ω), the allowable secondary load is 27.19 Ω, which is greater than the rated load of the CT by 20VA (20VA/1=20 Ω). This data can be used to determine that the transformer is qualified. In addition, when the secondary load is 19.58 Ω (close to 20 Ω), the allowed current multiple is 12.85 times, which is greater than the rated current multiple of the CT (10 times). This data can also be used to determine that the transformer is qualified. In fact, as long as either of these two key points is identified, it is possible to determine whether the measured transformer is qualified.

If the 10% error does not meet the requirements, the general approach is:

Increase the interface area of the secondary cable (reduce the secondary impedance)

Series connection of current transformers of the same type and ratio (reducing the excitation current of the transformer)

Switch to windings with higher volt ampere characteristics (increased excitation impedance)

Increase the current transformer ratio (increase excitation impedance)

Price of 600A/1000V Transformer Comprehensive Tester