Research On Energy Measurement Method Of A Natural Gas Pipeline Network Based On TGNET Software

At present,China still adopts volume measurement to measure and price natural gas.Compared with volume measurement,energy measurement is more scientific and fairer,so it is widely used in the handover measurement of international natural gas trade.The energy of natural gas is to determine the calorific value of natural gas distributed to users on the basis of volume measurement,and then multiply the two.At present,most class B and class C metering stations in China are not equipped with on-line gas chromatograph,so it is impossible to obtain natural gas composition and calorific value.Simulation software can be used to track the composition of natural gas and assign value to the calorific value of natural gas.The research of this paper has important theoretical significance and application value for the popularization and implementation of energy measurement in China.First,this paper analyzes and evaluates the model solving algorithm,component tracking method,calorific value calculation method and User Defined Logic of TGNET software,so as to determine that TGNET software has certain applicability in energy measurement,and lays a theoretical foundation for subsequent simulation and research.Then,the principle of Minimizing the Influence of Instrument Measurement Error on Simulation Accuracy is proposed.Through the closure analysis of transient simulation equations and the sensitivity analysis of pressure and flow measurements to simulation results,a combination method of boundary conditions suitable for the transient simulation of multi-source and multi-user natural gas pipeline network is recommended.By studying the influence law of pre simulation on transient simulation results,the pre simulation time is determined,which provides a basis for determining the initial conditions of transient simulation.Using the boundary conditions and initial conditions obtained from the research and based on the historical operation data of the pipeline network,a transient simulation model for energy metering for NWZP natural gas pipeline network is established.The model can realize the dynamic tracking of pressure,temperature,flow,composition and calorific value.Using the User Defined Logic module of TGNET software,aiming at the pressure simulation error of each node not exceeding 1.0%,the automatic calibration of gas transmission efficiency of pipe section is realized by Python language programming.After that,the overall heat transfer coefficient is calibrated through multiple trial simulations,so that the simulation error of node temperature is within 1.0℃.Based on the calibrated simulation model and historical operation data,the accuracy of the simulation model is verified.It is verified that the simulation error of pressure and flow is within 1.0%,the temperature simulation error is within 1.0℃,and the calorific value simulation error is within 0.3%,which meets the allowable error specified in GB/T 18603-2014.Using the calibrated simulation model of NWZP natural gas pipeline network,the quality tracking of natural gas pipeline network is realized,the time of natural gas transmission from the gas source point to each offtake station is determined,and the calorific value of each offtake point is calculated.Considering the variation range of gas source calorific value and natural gas transmission time,the calorific value of natural gas in the offtake station without on-line gas chromatograph is assigned.Using the volume / energy line pack and energy flow obtained by simulation,the calculation of the Unaccounted for Gas based on volume and energy is realized,which lays a foundation for the monitoring and management of the Unaccounted for Gas.