Optical fiber type voltage measurement method and measurement mechanism thereof
The invention belongs to the power measurement technical field, relate to a kind of optical fiber type voltage measurement method and measurement mechanism thereof that various transient voltages are measured by the electric power network system that be used for.
Multinomial system debug test in the electric system nearly all be unable to do without the measurement to line voltage.Along with the development that power grid constructions at different levels especially UHV (ultra-high voltage) and extra-high voltage grid are built, high voltage measuring workload and difficulty are also increasing, and particularly the measurement to various transient voltages is more difficult in the electric system.Conventional voltage measurement method mainly contained two kinds in the electric system in the past, the method that promptly adopts the method for voltage measuring transformer and adopt bushing end screen to measure.Voltage transformer (VT) has two kinds of electromagnetic type and condenser types again by its principle, adopts the mode of voltage measuring transformer voltage generally can only be used for the slower transient voltage of stable state power-frequency voltage and change in voltage and measures; And when the measuring voltage transient state process has upper frequency, then can only adopt the method for bushing end screen to measure.This is external not to possess under the condition of above two kinds of voltage measurement modes, and just need installing independently, voltage divider carries out voltage measurement.Voltage divider independently is installed needs the transient characterisitics such as frequency, amplitude, duration according to measuring voltage to select suitable voltage divider for use.When measuring high voltage, the on-the-spot interim restriction that independent voltage divider can be subjected to space, place, safe distance etc. condition of installing, installation difficulty and workload are all bigger in addition.
Shield and install the measuring voltage mode of independent capacitance formula (capacitive divider uses more) voltage divider in the prior art for employing capacitance graded bushing end, need be according to the measuring voltage scope configuration second divided voltage capacitor of electric capacity and measuring equipment, need simultaneously to connect second divided voltage capacitor and survey record instrument with shielded cable, second divided voltage capacitor specific characteristics wherein, shielded cable characteristic (need install build-out resistor additional to higher frequency signals) and shielding connection state are bigger to measuring influence, the length of stube cable is also unsuitable oversize in addition, otherwise can increase the decay of measured signal and cause the reduction of its interference free performance.
Along with the development of UHV (ultra-high voltage) and UHV transmission line construction process, also more and more higher to the requirement of measuring various transient voltages.Fast transient overvoltage (VFTO) rising edge that electric system GIS (gas fully closed combined electric unit) equipment disconnector deciliter process produces can reach 3ns, transient frequency reaches 100MHz, obviously, measuring this voltage adopts usual manner can not satisfy measurement requirement.For this reason, in recent years the existing people in this area to propose to adopt the Optical Fiber Transmission metering system be that photoeletric measuring system comes measuring voltage.
Photoeletric measuring system is a kind of measuring system of utilizing various photoelectric effect or photoelectric communication mode to carry out, in this system, utilize optical fiber transmission line good insulation performance performance, measured high-tension apparatus and low pressure measurement instrument are carried out electric signal isolation, in order to realize safe and reliable measurement high-tension electricity characterisitic parameter.Adopt the mode of Optical Fiber Transmission measuring voltage that two big classes are arranged at present: a class is the measuring system that adopts the electrooptical effect sensor to constitute, using more is the measuring system that adopts bubble Ke Er (Pockels) electrooptical effect, and another kind of is the measuring system that condenser type field intensity probe (spheric probe) constitutes.Adopt the system characteristic of the measuring system of bubble electrooptic Kerr effect to depend primarily on the characteristic that electric light is changed crystal, the conversion characteristic of this crystal is subjected to Temperature Influence bigger, accurately measuring needs comparatively precise dose compensation, whole measuring system is divided photoelectricity part and record measure portion, and wherein the photoelectricity part is comparatively complicated.The measuring principle of the voltage measurement system that condenser type field intensity probe constitutes is to place pair of metal pole plate (being generally spherical pole plate) in measured electric field, the pole plate plane is vertical with direction of an electric field, this constitutes a capacitor field intensity probe to pole plate, draws electric field intensity by polar plate spacing from the voltage that reaches between measuring pad.Use strong method measuring voltage, need to calculate the voltage of tested electrified body with the relation of the voltage of electrified body and measured point electric field intensity, but present this voltage measurement system parameter strong in maximum measurement fields and measuring distance is not high, can not be used for the measurement of higher electric field intensity, the simultaneity factor structure is also comparatively complicated.
Summary of the invention
The objective of the invention is to solve at the problem that prior art exists, provide a kind of design proposal rationally, the optical fiber type voltage measurement method of measuring accuracy and good stability and application easy to implement, a kind of said method optical fiber type voltage measurement device that is used to realize is provided simultaneously.
Optical fiber type voltage measurement method of the present invention comprises following implementation step: place a metal induction pole plate on tested high-pressure conductor surface, utilize this induction pole plate to form a capacitive divider (referring to accompanying drawing 1) with capacitor C 2 and the C1 that tested high-pressure conductor (high-voltage conducting wires) and ground constitute respectively, because the voltage on the capacitor C 2 is proportional to high-pressure conductor voltage over the ground, behind the magnitude of voltage on intrinsic standoff ratio that records capacitive divider and the capacitor C 2, according to the tested high-pressure conductor voltage-to-ground value of magnitude of voltage conversion acquisition of capacitance partial pressure ratio and C2.In the real work, can record the intrinsic standoff ratio K of capacitive divider by the standard voltage divider calibration, and collect voltage signal on the capacitor C 2 by the data acquisition unit that is placed on noble potential that connects with metal induction pole plate, then more successively by the voltage signal on the capacitor C 2 being sent into computer system processor record and display voltage data, obtain tested high-pressure conductor voltage-to-ground value according to the dividing potential drop ratio of capacitive divider and the magnitude of voltage conversion of C2 at last with electrical optical converter (optical sender), optical fiber and the photoelectric transformer (photoreceiver) of data acquisition unit UNICOM.
Be used to realize that the optical fiber type voltage measurement device of above-mentioned voltage measurement method is a kind of device that the various transient voltages of electric system (the outside VFTO that comprises very high frequency) are measured that can be used for, it is by the front end processor that is equipped with metal induction pole plate outward, optical fiber, light-to-current inversion module and computer department are grouped into, metal induction pole plate and front end processor shielding case are formed the capacitor voltage sensor, in the front end processor shielding case, be provided with data acquisition unit and electro-optical conversion module, the signal output part of capacitor voltage sensor passes to the input end of electro-optical conversion module through data acquisition unit, electro-optical conversion module output terminal connects with the light-to-current inversion module input by optical fiber, and light-to-current inversion module output terminal passes to the signal input part of computing machine.
Compared with prior art, the advantage that has of the present invention is:
A) adopt the condenser type field strength sensor, directly measure the electrified body surface electric field intensity, can improve the accuracy and the stability of measuring voltage;
B) voltage sensor, measurement and light-to-current inversion are concentrated to one, can effectively be improved interference free performance;
C) the data acquisition unit piece is placed noble potential and by computer control, have that measurement range is wide, frequency response good, the signal record capacity big, measure flexible characteristic;
D) adopt digital fiber communication, can realize the 10km telemeasurement;
E) adopt the dull and stereotyped induction of small size pole plate, frequency response is wide;
F) simple in structure, easy to install, cost is low, cost performance is high.
Description of drawings
Fig. 1 is a voltage measurement schematic diagram of the present invention.
Fig. 2 is the theory structure block diagram of a specific embodiment of measurement mechanism of the present invention.
Fig. 3 is the structural representation of a kind of capacitor voltage sensor in the measurement mechanism of the present invention.
Fig. 4 is the structural representation of another kind of capacitor voltage sensor in this measurement mechanism.
Referring to accompanying drawing, the measuring principle of optical fiber type voltage measurement method of the present invention and measurement mechanism thereof is: place a metal induction pole plate on high-pressure conductor (high-voltage conducting wires) surface, metal induction pole plate and high pressure conductor form capacitor C 2, form capacitor C 1 with ground.
When high-pressure conductor voltage over the ground is V (alternating voltage, below identical),
Voltage on the C2:
When on known high-pressure conductor voltage-to-ground V and the capacitor C 2 during voltage V2, can try to achieve intrinsic standoff ratio K according to (3) formula, or behind voltage V2 on known intrinsic standoff ratio K and the capacitor C 2, can try to achieve high-pressure conductor voltage over the ground according to (3) formula.In actual applications, can record the intrinsic standoff ratio K of capacitive divider, and record V2, and then calculate high-pressure conductor voltage-to-ground V by (3) formula by the optical fiber type voltage measurement device by the standard voltage divider calibration.
An example structure of optical fiber type voltage measurement device of the present invention as shown in Figure 2, whole device is divided into electrification in high voltage part (front end processor), optical fiber and as the photoelectric conversion units and the ground-based computer part of terminating machine.Front end processor is mainly by the capacitor voltage sensor that is used for electric field signal is transformed into voltage signal, be used for the analog voltage signal of sensor is transformed to the modulus data acquisition unit of digital signal and storage, be used to finish electro-optical conversion module (optical-fibre communications module) and the electric battery (front end processor working power) and the full-shield cabinet composition of electricity-light conversion, between capacitor voltage sensor and data acquisition unit, be equipped with a range and measure control module, between data acquisition unit and electro-optical conversion module, be equipped with data communication module, the I/O end of data communication units connects with the output/input end of range and measurement control module simultaneously, is provided with the optoelectronic switch that is used for receiving terminal machine order control front end processor power supply between electro-optical conversion module and data acquisition unit.The performance of shielding case is very important to the stability and the reliability of whole measuring system, when shielding case can not become a complete metallic shield body (seamless), its shield effectiveness the most important thing is to handle the slit of metal junction except that outside the Pass having with shielding thickness; Shielding case is also formed the capacitor voltage sensor with the induction pole plate, so this part also is the key of whole shield effectiveness except that finishing function of shielding.Terminating machine is made up of three parts: light-to-current inversion module (optical-fibre communications module), optical fiber telemetry power switch emission control module, computing machine and measuring system software, the measurement control software of computing machine wherein, the digital collection module that employing is purchased carries software, this software function is simple, use operation to compare than big-difference, can satisfy use basically with the data acquisition unit software of routine.The optical fiber that adopts in the measurement mechanism is chosen the four optical-fiber cable of length 200m, satisfies communication and teleswitch and uses.
The capacitor voltage sensor is the basis of entire measuring device among the present invention, the measurement performance of the performance decision total system of voltage sensor.The major parameter of capacitor voltage sensor has: voltage output range; Impedance operator; Frequency characteristic; Structural behaviour etc.The capacitive transducer that originally deviser manufactures experimently as shown in Figure 3.Induction pole plate among the figure is a circular metal thin plate, is placed on apart from 30mm place, shielding case surface, and the induction pole plate is connected with external voltage-dividing capacitor (secondary electric capacity), from the voltage-dividing capacitor output voltage.It is in order to make sensor can export the higher voltage signal that pole plate and shielding case have the distance of 30mm, and inserting a dividing potential drop electric capacity is in order to reduce the output impedance of sensor.But, find that also there is following problem in this sensor: 1. through test of many times. owing to there is a second divided voltage electric capacity, the frequency response of sensor is not high, does not reach designing requirement; 2.. the induction pole plate hight goes out shielding case 30mm, and system's electric field uniformity coefficient is bad; 3.. structure is difficult for into as a whole.For this reason, the deviser makes new improvement to the sensor again.Capacitor voltage sensor construction after it improves as shown in Figure 4, it by shielding case, be embedded in the metal induction pole plate above the shielding case and the polyester insulated film that is filled between metal induction pole plate and the shielding case constitutes, induction pole plate upper surface is mutually concordant with the shielding case upper surface, and the thickness of the polyester insulated film between metal induction pole plate and shielding case is less than 0.1mm.Compare with sensor shown in Figure 3, novel sensor after the improvement has reduced the relative height of induction pole plate and shielding case, between pole plate and shielding case, fill high frequency characteristics mylar preferably, its thickness is less than 0.1mm, to increase the capacitance of induction pole plate and shielding case, reduce output impedance; Induction pole plate and shielding case are in a plane, help improving the whole electric field uniformity coefficient and the integral rigidity of structure; Remove second divided voltage electric capacity, back level equipment is directly arrived in output.Through the performance test to this modified capacitor voltage sensor, its performance has reached designing requirement.
It is the device of PicoScope5204 that data acquisition unit of the present invention can adopt the module model, comprises range in this device and measures control module, data communication module and corresponding solidification software.Because the input impedance of data acquisition unit generally has only 1M Ω, the output impedance of capacitor voltage sensor when power frequency 50Hz is about 1M Ω, data acquisition unit directly connects the capacitance voltage sensor can cause bigger frequency width of cloth error, for this reason, between data acquisition unit and capacitance voltage sensor, to insert a high resistant attenuator.After having inserted the high resistant attenuator, when frequency input signal changes from 50Hz to 250Mhz, acquired signal range error≤1%.Choose dark storage data more than 100M, then can be with the sampling rate tracer signal length of 1G/s greater than 100ms.When measuring the superpotential of VFTO, open type disconnector deciliter aircraft carrier line, just can more intactly record the high speed transient waveform like this.
The data communication module of this device is the module that front end processor and terminating machine are connected with light signal, and choosing of communication module is that interface shape with collector is chosen.To the collector of domestic 50MHz, its interface shape is RJ45, and the communication module of at this moment selecting for use is: RJ45 changes optical fiber and optical fiber changes RJ45; The import collector is a USB interface, and the module of choosing is that USB changes optical fiber and optical fiber changes USB.The optical fiber interface of RJ45 is comparatively universal at home, the optical fiber interface of USB is produced seldom at home, through USB optical fiber interface test to domestic production, its data transmission rate low performance instability, chosen the USB optic fiber converter of import at last, through overtesting and performance test, this USB optic fiber converter can satisfy request for utilization.
Optoelectronic switch in Fig. 2 device is selected the optical fiber telemetry power switch, and its quiescent dissipation is: voltage 12V, electric current 15mA; Power connection electric current 45mA.It is the USB optical communication module of USB2.0Ranger444 that electro-optical conversion module and light-to-current inversion module all adopt model.