What are the main errors of Power Current Transformer?

1. Impact on measurement
Inaccurate power metering: The ratio error and phase error of Power Current Transformer will cause the current value measured by the power meter to deviate from the actual current value, resulting in errors in power metering. In long-term operation, this measurement error may cause disputes in the settlement of electricity bills between power companies and users, affecting fair transactions in the electricity market. For example, if the error of Power Current Transformer is positive, the power meter will measure more electricity than the actual electricity consumption, and users will pay more for electricity; conversely, if the error is negative, the power company will charge less for electricity.
Unable to accurately monitor equipment load: Inaccurate current measurement will affect the accurate judgment of the load situation of power equipment. Operators cannot accurately understand the actual operating status of the equipment based on inaccurate current data, and it is difficult to determine whether the equipment is overloaded, underloaded or in normal operation, so they cannot reasonably adjust the operation mode of the equipment and distribute the load, which may cause the equipment to operate under unreasonable load conditions for a long time, reducing the service life and operating efficiency of the equipment.
2. Impact on protection
Protection device malfunction or refusal to operate: The error of Power Current Transformer may cause the current signal received by the protection device to be inaccurate, thus affecting its judgment and action on the fault. For example, in overcurrent protection, if the ratio error of Power Current Transformer is too large, so that the measured fault current is less than the actual fault current, the protection device may refuse to operate, fail to cut off the fault circuit in time, expand the fault range, and cause more serious damage to the power equipment. On the contrary, if the error makes the measured current greater than the actual current, it may cause the protection device to malfunction, causing unnecessary power outages and affecting the power supply reliability of the power system.
Reduced protection sensitivity: Phase error will affect the performance of protection devices such as differential protection that are sensitive to current phase. Due to the existence of phase error, the current phase difference measurement of the current flowing into and out of the protected device is inaccurate, which may lead to reduced sensitivity of differential protection, and failure to detect minor faults inside the equipment in time, thus affecting the effective protection of the protection device to the power equipment.
3. Impact on power system control
Automatic control device misjudgment: Many automatic control devices in modern power systems rely on the current signal provided by the Power Current Transformer for control decisions. If the error of the Power Current Transformer is large, the current information received by the automatic control device will be distorted, resulting in incorrect judgments and control instructions. For example, in the reactive power automatic compensation device of the power grid, inaccurate current signals may make the compensation device unable to accurately compensate according to the reactive power demand of the system, affecting the voltage quality and power factor of the power grid, and reducing the operating stability and economy of the power system.
Deviation of system operation status assessment: The error of the Power Current Transformer will affect the accurate assessment of the overall operation status of the power system. The analysis results such as system flow calculation and short-circuit current calculation based on inaccurate current measurement data will deviate from the actual situation, which may cause the operator to make incorrect judgments on the operation status of the system, fail to discover potential safety hazards and operation problems in time, and are not conducive to the safe and stable operation and optimized scheduling of the power system.
4. Impact on equipment selection and verification
Irrational equipment selection: If the error of the Power Current Transformer is not fully considered in the design stage, it may lead to unreasonable equipment selection. For example, if the accuracy level of the selected Power Current Transformer cannot meet the actual measurement and protection requirements, the measurement accuracy and protection reliability will not meet the expected goals, affecting the overall performance of the power system. In addition, inaccurate error assessment may also cause the rated capacity of the selected Power Current Transformer to not match the actual secondary load, further increasing the measurement error.
Inaccurate verification results: When verifying the Power Current Transformer, the presence of errors will affect the accuracy of the verification results. If the error factor is not properly considered during the verification process, it may lead to misjudgment of the performance of the Power Current Transformer, believing that the qualified transformer actually has a large error, while the unqualified transformer is misjudged as qualified, so that the problematic transformer is put into operation, affecting the safe and reliable operation of the power system.