For a long time

it is unable to realize online monitoring of long-term operation error of voltage and current sensors for distribution network.As a result

it not only restricts the primary and secondary deep integration and intelligent development of distribution equipment

but also hinders the realization of intelligent distribution network.This paper proposes an online test method for long-term operation error of voltage and current sensors based on Fourier transform.An online test device for the error of voltage and current sensors is developed

which is composed of the standard voltage and current converter

the collector and the industrial computer.Through the high-precision measurement circuit and the decomposition processing and offline calibration of AC fundamental wave of digital signal

the overall measurement accuracy and operation reliability of the device are fully verified to ensure that it can meet the requirements of online test.Then

based on the proposed device

a long-term online error test platform for voltage and current sensors is built and used to carry out online error real-time test of four types of sensors for a long time（200 days）

including air-core coil and low-power current sensor

capacitive voltage divider and resistance voltage divider voltage sensor.Through the systematic analysis of a large number of measured data

the basic law of error variation of these four types of sensors under the long-term working condition is found out.Further

the technical measures are presented to reduce long-term operation error of different types of sensors

which provides technical support for the primary and secondary deep integration and intelligence of distribution equipment

and the intelligence of distribution network in the future.