Research On Key Technologies Of Harmonic Voltage Ratio Standard

With the development of the industrial economy,more and more non-linear and high-power loads are connected to the power system.Among them,high-power rectifier devices and metallurgical arc furnaces have the greatest influence on the system.In recent years,the rapidly developing distributed energy sources also have certain harmonics in the on-grid electrical signals due to the large number of rectifier devices.According to the relevant regulations,high-voltage energy metering equipment such as voltage transformers are calibrated at 50 Hz,and their measurement characteristics under harmonic conditions have not yet been formally included in the relevant assessment.The actual measurement on site found that the above-mentioned typical load field voltage waveform contains a large amount of harmonic components for a long time.If the harmonics are calculated according to the national standard GB/T 14549-93 power quality utility grid harmonics,the measurement accuracy of harmonic transformers only need to meet 5%.After long-term operation,it will cause great error in energy metering and bring about large economic losses.At present,the measurement standard of voltage transformer under the harmonic condition has not been established in China,and the evaluation of the harmonic measurement characteristics of the transformer is still blank.The distribution parameters of the equipment under high frequency conditions will bring a large measurement error to the metering equipment,while the transformer equipment is bulky and high voltage,and the distributed parameter control technology is difficult,and the biggest difficulty in establishing the harmonic voltage transformer proportional standard is how to complete the traceability of the transformer,design a set of perfect tracer tracing method under harmonic frequency,from the low voltage to the highest voltage.In this paper,based on the demand of voltage transformer traceability under harmonic conditions,the method of traceability of harmonic transformer under harmonic voltage is proposed,and the corresponding standard equipment is developed.The uncertainties of different devices are assessed,and some voltage transformers were tested under harmonic condition.The main work are as follows1)The "step-up harmonic voltage proportional device traceability method was proposed based on the capacitive voltage divider formed by the gas capacitor.The voltage divider and the inductive-type standard voltage transformer are designed to be mutually calibrated2)The voltage addition traceability method under power frequency is successfully extended to the traceability of the transformer under harmonic conditions,and the traceability of the lOkV inductive-type voltage transformer is completed.The method is used to verificate the step-up traceability method3)A dual-channel data switching method is proposed to realize the mutual switching acquisition of different channel data during the dual-channel acquisition process,which greatly reduces the measurement error caused by the error and offset of the component and buffer circuit itself.The error measurement tests shows that the measurement error is better than 1 × 10-7 for the acquisition equipment using this technology4)An active voltage divider based on the principle of operational amplifier is designed The high voltage arm of the voltage divider is a compressed gas capacitor,and the low voltage arm are ceramic capacitor.Based on the principle of operational amplifier,a voltage divider is formed to complete the basic circuit,loop gain,notch design,and stability and error calculations.lOkV and 110kv/(?)capacitive active electronic voltage dividers were fabricated.5)Using the step-up method,the traceability of the inductive-type harmonic voltage proportional standard and the capacitive active electronic voltage divider are completed.The inductive harmonic voltage ratio standard meet a measurement accuracy class of 0.01.6)The evaluation of the measurement uncertainty of the "step-up method is completed,and the uncertainty components of the traceability are listed in detail.In the range of 50Hz to 2500Hz,the measurement uncertainty of 10kV capacitor divider is from 5.6×10-6 to 84.2×10-6,6?rad to 55.2?rad,respectively.The measurement uncertainty of 110kv/(?)capacitor divider is from19 ×10-6 to 96.4×10-6,from 20.2 ?rad to 67.6 ?rad,respectively.7)Based on the harmonic active voltage divider and error calibration equipment,the frequency characteristics of 10kV,35kV inductive voltage transformer and 35kV CVT are tested.The test results show that 10kV inductive voltage transformer has better frequency characteristics at 2500 Hz.The overall error at 2500 Hz still meets the requirements of 0.5-level transformer.However,the error of CVT has a sharp change when the frequencies are not 50Hz.The error of the ratio is up to 54.4%,and the maximum phase shift is 5426.15'.It cannot be used for harmonic measurement.