Analysis Of Causes Of Measurement Errors In Jiangmen Area And Study On Its Solution

Energy metering is essential for power plants,power grids and consumers.As a commodity in the market economy conditions,electricity cannot be sold as normal due to its own characteristics.The birth of electric energy measuring instruments successfully solve the problem of the electric energy metering.However,it is still a remained problem to measure the electrical power accurately.The development of electrical industry has promoted the modern society to success,while the enlarged utilization of large amount of electrical power has accelerated the development of the electrical industry itself as well.In low-level modern power systems,the electrical consumption varies widely during different periods of time due to heavy demand and uncontrolled load.Furthermore,the metering error may be dramatically increased because of the distortion of voltage and current curves due to the behavior of nonlinear loads.To solve the problem of metering accurately,several works are finished in this thesis:1.Reasons to cause measurement error is located by analyzing the structure and the operating principle of the metering devices in depth;2.In the Jiangmen power network level,reasons to cause measurement error is deduced by analyzing the power supply circuits,neutral point grounding mode as well as the variation of the ratios of CTs or PTs,while several conclusions are drawn as: 1)intrinsic errors of the metering devices can cause measuring errors;2)Incorrect equipment selection can cause measuring errors;3)zero-sequence current by different neutral point grounding mode can cause measuring errors;4)wrong ratios of CTs and PTs,and so on.3.Experiments to study the error mechanism for 3-phase-3-wire electronic Watt-hour meters are implemented on 3-phase energy meter calibration devices;4.Several methods to reduce measurement error is proposed: 1)Selection of metering devices with appropriate accuracy;2)Selection of appropriate CTs and PTs;3)prevention of error caused by zero-sequence current by 3-phase-4-wire devices;4)Reduction the error caused by the secondary voltage loss of PTs;5)Monitoring the metering points by modern electric energy metering system.