POWER-CABLE GROUND CURRENT SELF-ADAPTIVE MONITORING METHOD

摘要

The present invention provides a power-cable ground current self-adaptive monitoring method. The steps including configuring a sample baseline, determining an impact factor set of the sample data, sampling real-time data of ground current by a power-cable ground current monitoring system, perform digital filtering on the sampled real-time data of ground current, applying a self-adaptive method to process the filtered sample data, and uploading the processed sample data to a backend monitoring device for real-time monitoring. The present invention may solve high energy loss and low information amount problems. The power consumption of monitoring device may be reduced by more than 50%, and server resource occupancy percentage may be lowered by about 20%. Efficiencies of evaluating external insulation status of the are enhanced. The present invention provides a novel grade ranking criterion, which may be dynamically corrected based on actual power-line operations, and reduces objective interferences during value determination process.

主权项

1. A power-cable ground current self-adaptive monitoring method, implemented by a power-cable ground current monitoring system, the power-cable ground current monitoring system including a power-cable ground current real-time sampling device and a backend monitoring device, comprising:
step (1): configuring a sampling baseline, wherein: three-phase induced electromotive forces (EMF) of ground cables A, B, and C are obtained by:EB=lI2ω(ln2SD)×10-7,EA=EC=lI(2ω(ln2SD)×10-7)2+2ω(ln2SD)×10-7×2ω(ln2)×10-7+(2ω(ln2)×10-7)2,wherein D denotes a diameter of a metal layer of a cable; S denotes a distance between centers of the cables; l denotes a cable length; I denotes a cable operating current; and ω denotes an angular frequency;
based on the three-phase induced electromotive forces, three-phase induced currents I1 are obtained by:I1A=EAZOA+R1+R2+Re+Xhe×L,I1B=EBZOB+R1+R2+Re+Xhe×L,I1C=ECZOC+R1+R2+Re+Xhe×L.wherein ZOA, ZOB, and ZOC denote self-impedance of cable sheaths; R1 and R2 denote ground resistance at a beginning of the cable sheath and at an end of the cable sheath; Re denotes earth leakage resistance; and Xhe denotes mutual inductance of the earth leakage current with respect to the cable sheath;
a capacitive current of the cable is I2=JωCU, wherein ω denotes the angular frequency, C denotes a capacitance of the cable, and U denotes cable voltage; I3 denotes an induced current change of the cable sheath according to load current fluctuation, and I3 is recorded online by the power-cable ground current real-time sampling device; and based on equation Id=I1+I2+I3, a minimum monitoring valid value, also referred to as the sampling baseline, is obtained, and is configured in the backend monitoring device for the power-cable ground current; step (2): determining an impact factor set of a sample data, wherein: the impact factor set is denoted as U={U1,U2}, wherein: U1={u11,u12}, u11 denotes a time point in a day; u12 denotes a time period in a year; U2={u21,u22,u23}; u21 denotes a dispatch quota; u22 denotes a dispatch duration; and u23 denotes a dispatch impact factor; step (3): sampling, by the power cable ground current real-time sampling device, data of the ground current in real-time; step (4): performing, by a digital filter, digital filtering on the sample data of the real-time power-cable ground current, wherein a function model of the digital filter is:H(i)2=11+(iic)2n=11+ɛ2(iip)2n,wherein, n denotes a filter order; ic denotes a cutoff value as of the ground current; and ip denotes a band-pass edge of the ground current;
step (5): applying a self-adaptive algorithm to process the filtered sample data, wherein the self-adaptive algorithm is{H(i)2=11+(iic)2n=11+ɛ2(iip)2nic=id+θΔI-rθ={U1,U2}, wherein ΔI denotes a difference between a present ground current measurement value and id; θ denotes the impact factor set; and r denotes a rate-adjusting variable; and
step (6): uploading the processed sample data to the backend monitoring device for real-time monitoring.