When a current transformer is in operation, its secondary circuit is always closed. During installation, ensure correct connection of the primary and secondary sides to prevent short circuits or open circuits, and perform regular maintenance and calibration. Short circuits are strictly prohibited on the secondary side of voltage transformers (and open circuits are strictly prohibited on current transformers (CTs)); otherwise, the equipment may be damaged. The secondary side must be reliably grounded to prevent high voltage from endangering personnel and equipment in case of insulation breakdown. Wiring must be correct; V/V, Y/Y, and other connection methods are suitable for different scenarios. For high-voltage applications, transformers convert the current and voltage of high-voltage lines into measurable values for instruments and protection devices.
As a crucial part of metrology, on-site calibration of transformers has a profound impact on power supply reliability and customer service quality. Transformer calibration instruments are required to perform error testing and polarity verification on transformers. For special locations such as high-speed rail traction stations, specific transformer calibration plans must be developed in advance. According to regulations, transformers must be periodically calibrated to ensure their measurement accuracy meets requirements. For electronic current transformers, because their output is a weak electrical signal including digital values, new verification methods and standards must be explored.
Common faults of current transformers include metering inaccuracies caused by improper installation or configuration. For example, replacing a new type of electricity meter during construction without simultaneously updating the matching current transformer can lead to undercharging due to mismatched parameters between the old and new equipment; or the low-voltage feeder connected to the metering device may only have one turn with the current transformer, resulting in a significant discrepancy between the applied charging multiplier and the correct metering multiplier, causing undercharging.