CN106771505A - Single-phase overhead transmission line of electricity phase voltage method for self-calibrating based on series capacitance - Google Patents

Abstract

Circuit is considered as a bulky capacitor and carries out partial pressure to it by a kind of method for self-calibrating of single-phase overhead transmission line of electricity phase voltage, utilization space principle of capacitive divider with the earth, using air as dielectric.Wire metals part is directly connected with top crown, wherein tandem tap electric capacity, change stray capacitance of the top crown to wire by changing its capacitance, different magnitudes of voltage will be measured on sampling capacitance, so as to each unknown stray capacitance size and voltage swing to be measured can be extrapolated, the contactless self calibration of wire phase voltage is realized.The present invention is applied to the requirement of distribution distributed devices, better than existing voltage measurement scheme.

Description

Single-phase overhead transmission line of electricity phase voltage method for self-calibrating based on series capacitance

Technical field

The present invention relates to a kind of single-phase overhead based on series capacitance being applied in trolley line distributed electrical pressure sensor Transmission line of electricity phase voltage method for self-calibrating.

Background technology

With continuing to develop for China's power industry level, the developing direction that strong intelligent grid turns into following is built. Current China's distribution network line has a large capacity and a wide range line length, and local environment is complicated, fault rate is high, developing low-cost distributed monitoring dress Put, realize to the real time on-line monitoring with Running State with fault location to realizing that it is great that the operation of power distribution network high-efficiency and economic has Meaning.

The accurate measurement of distribution to distribution network overhead line phase voltage is a difficult point.Now widely used voltage sensor Device mainly has electromagnetic type (PT), condenser type (CVT) voltage transformer, optical voltage sensor etc..Optical voltage sensor stabilization Sex chromosome mosaicism is not yet solved very well, it is necessary to high accuracy processing technology and technique for sticking, not yet obtain extensive in electric power mutual-inductor Using.Traditional PT capacity is smaller, high cost, insulation system are complicated, there is ferromagnetic resonance phenomenon, have the factors such as leakage inductance distribution capacity Influence, the demand of nowadays power network is not suitable with gradually.CVT is mainly used in more than 330kV power networks, and volume is big, involves great expense, no It is easy to install, it is impossible to meet the requirement of inexpensive distributed devices.Hence set up a kind of phase electricity suitable for distribution distributed devices Pressure measuring method, and contactless self calibration can be realized, the voltage measurement accuracy to improving distributed devices is significant.

The content of the invention

It is an object of the invention to propose it is a kind of it is new suitable for miniaturization distributed devices based on series capacitance The method for self-calibrating of single-phase overhead transmission line of electricity phase voltage, overcomes the shortcomings of existing PT, CVT, optical voltage sensor, with height Certainty of measurement.Its utilization space principle of capacitive divider, voltage two-stage is considered as by transmission line of electricity with the earth, has upper bottom crown by one Plane-parallel capacitor be placed in one as sampling capacitance, take into full account stray capacitance of two pieces of pole plates to voltage two-stage, set up Lumped parameter equivalent circuit.Wire is directly connected with top crown, wherein concatenate a switching capacity, by change its capacitance so as to Change top crown to the stray capacitance of wire, different magnitudes of voltage will be measured on sampling capacitance, so as to can extrapolate each unknown Stray capacitance size and voltage swing to be measured.

Technical solution of the invention is as follows：

A kind of single-phase overhead transmission line of electricity phase voltage method for self-calibrating based on series capacitance, its feature is, the method Comprise the following steps：

1) distributed Voltage sensor surveying unit is installed on single-phase overhead circuit, wherein sampling capacitance capacitance size Choose μ F ranks.Sampling capacitance top crown and high-voltage conducting wires metal part short circuit, do not concatenate switching capacity, and bottom crown is hanging.Its Partial pressure value is measured for U_c1.Input computer sets up equation below：

Wherein, C_gIt is the electric capacity of bottom crown to the earth, C is the capacitance of the sampling capacitance between two-plate, and U is circuit to be measured Magnitude of voltage.

2) disconnection short circuit circuit, the tandem tap electric capacity between measurement apparatus top crown and high-voltage conducting wires, its value is known Amount, size is C_h, then bottom crown is equivalent to earth capacitance C_gAnd C_hSeries connection,Partial pressure value U is then measured for the second time_c2, Input computer sets up equation below：

3) sampled value input computer measured by first two steps is made into following computing, you can obtain C_gCapacitance size

4) by step 3) calculated by C_gIn generation, returns step 1) in equation can try to achieve wire voltage U to be measured

5) by the way that switching capacity value C is varied multiple times_h, it is possible to achieve repeatedly calibration, improves certainty of measurement.

Circuit is considered as one by the present invention as a result of above technical scheme, utilization space principle of capacitive divider with the earth Individual bulky capacitor carries out partial pressure measurement to it, using air as dielectric.Wire metals part is directly connected with top crown, its Middle concatenation switching capacity, stray capacitance of the top crown to wire is changed by changing its capacitance, will be surveyed on sampling capacitance Different magnitudes of voltage are obtained, so as to each unknown stray capacitance size and voltage swing to be measured can be extrapolated, wire voltage is realized Self calibration.

Brief description of the drawings

Fig. 1 is equivalent measurement circuit diagram of the invention

Fig. 2 is tandem tap capacitor self-calibration equivalent circuit diagram of the invention

Fig. 3 is the voltage sensor work block diagram of present example

Fig. 4 is the overhead transmission line experimental situation simulation drawing of present example

Specific embodiment

Embodiments of the invention are elaborated below in conjunction with accompanying drawing, but protection model of the invention should not be limited with this Enclose.

Please referring initially to Fig. 1, Fig. 2, please referring initially to Fig. 1, Fig. 2, Fig. 1 is measurement apparatus measurement model equivalent electric of the invention Road, Fig. 2 is tandem tap electric capacity schematic diagram of the invention.As seen from the figure, the method comprises the following steps：

1) distributed Voltage sensor surveying unit is installed on single-phase overhead circuit, wherein sampling capacitance capacitance size Choose μ F ranks.Sampling capacitance top crown and high-voltage conducting wires metal part short circuit, do not concatenate switching capacity, and bottom crown is hanging.Its Partial pressure value is measured for U_c1.Input computer sets up equation below：

Wherein, C_gIt is the electric capacity of bottom crown to the earth, C is the capacitance of the sampling capacitance between two-plate, and U is circuit to be measured Magnitude of voltage.

2) disconnection short circuit circuit, the tandem tap electric capacity between measurement apparatus top crown and high-voltage conducting wires, its value is known Amount, size is C_h, then bottom crown is equivalent to earth capacitance C_gAnd C_hSeries connection,Partial pressure value U is then measured for the second time_c2, Input computer sets up equation below：

3) sampled value input computer measured by first two steps is made into following computing, you can obtain C_gCapacitance size

4) by step 3) calculated by C_gIn generation, returns step 1) in equation can try to achieve wire voltage U to be measured

Principle of the invention is as follows：

By distributed Voltage sensor surveying unit (hereinafter referred to as measurement apparatus) as on overhead transmission line, it is with empty Between capacitance partial pressure principle measure traverse line phase voltage over the ground.Wire phase voltage over the ground is realized using the principle of space capacitance partial pressure Measurement and calibration, its core parts is a capacitor, and wire is considered as a pole of bulky capacitor, is greatly another pole.By electric capacity Device is inserted between wire and the earth, and its top crown is joined directly together with wire metals part, forms equivalent survey as shown in Figure 1 Amount circuit.

According to principle of capacitive divider, partial pressure value has following relation with wire voltage on sampling capacitance：

Wherein C is sampling capacitance value, C_gIt is bottom crown stray capacitance over the ground.

Due to C_gIt is stray capacitance, general all very little, the order of magnitude is several pF to tens pF rank, and derided capacitors C Capacitance can choose it is very big, such as reach μ F ranks, then C ＞ ＞ C_g, then C+C_g≈C

Wherein, Cg, U are unknown quantity, and remaining is known quantity.

A kind of single-phase overhead transmission line of electricity phase voltage method for self-calibrating based on series capacitance, its feature is as follows：

Because single-phase bare conductor model of power transmission system is relatively simple, its phase voltage self-calibration process has two unknown parameters Need calibration, respectively C_gFor the electric capacity of bottom crown to the earth, U are line voltage value to be measured.Therefore the appearance of sampling capacitance is changed The value size of value known quantity C can not increase new effective equation number, and need to change the size of unknown quantity could increase new effective Equation.If can realize being superimposed a known quantity in a certain unknown quantity by concatenating switching capacity, according to front and rear remaining known quantity Change can obtain all unknown quantitys, realize the self calibration of the single-phase overhead transmission line of electricity phase voltage based on series capacitance.Its school Quasi- circuit is as shown in Figure 2.Can specifically realize as follows：

Step 1, chooses the sampling capacitance of μ F ranks, and short circuit between sampling capacitance top crown and high-voltage conducting wires is not concatenated out Powered-down appearance, bottom crown is hanging.It measures partial pressure value for U_c1.Then its value has following relation：

Step 2, disconnects short circuit circuit, and switching capacity is concatenated between top crown and high-voltage conducting wires, and its value is known quantity, greatly Small is C_h.Partial pressure value U is then measured for the second time_c2, its value has following relation：

Wherein：

Step 3, will twice measure sampled value and make following computing：

In step 4, generation, returns above formula and can try to achieve wire voltage U to be measured

Step 5, by the way that switching capacity value C is varied multiple times_h, it is possible to achieve repeatedly calibration, improves certainty of measurement.

It is checking effectiveness of the invention, devising an intelligent voltage for being applied to distribution line according to this invention senses Device, pcb board is directly welded in by derided capacitors C, and high-tension line is directly connected by conductor structure with C top crowns, and is gone here and there wherein Connection switching capacity.Short circuit, and the different capacitances that can connect on demand under normal circumstances.The upper voltage signals of C are after nursing one's health and amplifying Changing into data signal via sampling, then carry out treatment by CPU transfers to the communication module to carry out being wirelessly transmitted to system background, just In preservation and subsequent analysis, the block diagram that worked after its simplification is as shown in Figure 3.Device is calculated by Comsol Multiphysics Spuious distribution capacity is about 0.8pF, therefore design derided capacitors C=16nF over the ground, and 4 orders of magnitude bigger than stray capacitance are used for Partial pressure post-sampling.

Shaft tower is simulated using support, the parallel ground of wire is fixed, and connected with high pressure generator.Sensor is hung on On wire, it is 10kv power frequency sinusoidal voltages that high pressure generator produces virtual value, and experimental situation is built such as Fig. 4.Sensor collection electricity Hold both end voltage difference Δ U, its internal work chip is MSP430F5438A, and sample rate is 1kHz, every time ten cycles of sampling.Point Annexation between C top crowns and high-voltage conducting wires is not set as：Short circuit, one electric capacity of string, two electric capacity of series connection, on measurement C Partial pressure value is as a result as follows：

Connected mode	Short circuit	Series connection 1nF
			Partial pressure value (V)	0.48795	0.48757

Substituting into formula using preceding two groups of sampled values can calculate：

C_g=0.77938pF, U=10.01725kV

In sum, this method for self-calibrating can accurately solve uniline unknown capacitance parameter and line voltage distribution, realize The self calibration of the uniline phase voltage based on series capacitance.

Claims (1)

1. a kind of single-phase overhead transmission line of electricity phase voltage method for self-calibrating based on series capacitance, it is characterised in that including as follows Step：

1) distributed Voltage sensor surveying unit is installed on single-phase overhead circuit, wherein sampling capacitance capacitance size is chosen μ F ranks, sampling capacitance top crown and high-voltage conducting wires metal part short circuit, do not concatenate switching capacity, and bottom crown is hanging, distributed Voltage sensor measurement apparatus measure partial pressure value for U_c1, and be input into computer and set up equation below：

$U_{c1}=\frac{C_g}{C}\·U$

Wherein, C_gIt is the electric capacity of bottom crown to the earth, C is the capacitance of the sampling capacitance between two-plate, and U is line voltage distribution to be measured Value；

2) short circuit circuit is disconnected, the tandem tap electricity between distributed Voltage sensor surveying unit top crown and high-voltage conducting wires Hold, size is C_h, then bottom crown is equivalent to earth capacitance C_gAnd C_hSeries connection,Partial pressure value U is then measured for the second time_c2, Input computer sets up equation below：

$U_{c2}=\frac{C_g^{\′}}{C}\·U$

3) by step 1) and 2) measured by sampled value input computer make following computing, you can obtain C_gCapacitance

$\begin{array}{c}\frac{U_{c1}}{U_{c2}}=\frac{C_g}{C_g^{\′}}=\frac{C_g+C_h}{C_h}\\ \⇒C_g=C_h\·(\frac{U_{c1}}{U_{c2}}-1)\end{array}$

4) by step 3) calculated by C_gIn generation, returns step 1) in equation can try to achieve wire voltage U to be measured

$U=\frac{U_{c1}\·C}{C_h\·(\frac{U_{c1}}{U_{c2}}-1)}$

5) by the way that switching capacity value C is varied multiple times_h, repeatedly calibration is realized, improve certainty of measurement.