Power cable high resistant and flashover fault test device
Technical field
Power cable high resistant and flashover fault test device belong to power cable fault testing apparatus field.
Background technology
To the failure cable direct current that adds high pressure, when voltage arrives a certain value, voltage is very high, when field intensity is enough big, exist a spot of free electron under electric field action, to produce ionization by impact in the medium, the free-electron collision neutral molecule, make its excitation free and produce new electronics and positive ion, these electronics and positive ion obtain to collide mutually with other neutral molecule again after the electric field energy, this process constantly development is gone down, and makes electron stream in the medium " snowslide " aggravation, causes insulating medium to puncture, form conductive channel, the trouble spot is by powerful electron stream instantaneous short circuit.Be that Method of Cable Trouble Point can be breakdown suddenly, fault point voltage sharply reduces almost nil, and electric current increases suddenly, has produced an electrical discharge arc.According to the electric arc theory, the apparent resistance of this electric arc is very little, can think a low-resistance or short trouble.
In the moment that high-voltage arc produces, launch an action of low-voltage pulse to cable, write down this reflection configuration, because electric arc can be thought the fault of a low-resistance or short circuit, transmitting pulse waveform is opposite with reflected impulse waveform polarity, and reflection configuration polarity is for negative, and waveform downwards as shown in Figure 3.
After electrical discharge arc extinguished, cable returned to high resistant or flashover state, and launch an action of low-voltage pulse to cable this moment again, writes down this reflection configuration, and what waveform reflected is the pulse waveform of cable latter end open circuit.Two waveforms are simultaneously displayed on the screen.Because the notable difference point appears in two pulse-echo waveforms in the trouble spot, failure judgement point position as shown in Figure 4 easily.
But because the time that the electric arc that cable fault produces when puncturing exists is too short, generally tens between the hundreds of microsecond, and flame current drop sharply to by last kiloampere zero, the electric arc instability.Therefore for obtaining typical case's's (intact) electrical discharge arc transmitted waveform, must prolong the life period of electrical discharge arc.Still there is not at present the device that can prolong the electrical discharge arc life period.
The utility model content
The technical problems to be solved in the utility model is: design and a kind ofly can prolong the electrical discharge arc life period, make the high resistant of power cable and flashover trouble spot detect accurately power cable high resistant simple in structure, that cost is low and flashover fault test device.
The utility model solves its technical scheme that adopts: this power cable high resistant and flashover fault test device, comprise sending and receiving apparatus, High-voltage Signal Generator, cable under test, it is characterized in that: the high pressure input of High-voltage Signal Generator is isolated the back output terminal that links to each other respectively with high pressure and is linked to each other with cable under test with high pressure isolation, the coupling of second pulse signal with trap, the freewheeling circuit that boosts, and the coupling of second pulse signal links to each other with sending and receiving apparatus.
Trap comprises silicon stack VD1, resistance R 1.The high pressure input signal is connected to the measuring junction of cable under test through high-power resistance R1.Mainly play the wave arrestment effect, stop TDR to send the low pressure burst pulse and enter High-voltage Signal Generator, influence the reflection amplitude of remote fault.The main isolated high-voltage signal of silicon stack VD1 prevents that high-voltage signal from producing destruction to low-voltage capacitance.After the cable under test fault punctures, when voltage drops to a certain degree, with the electric weight of storing in the low-voltage capacitance, slowly discharge by resistance R 2 simultaneously, the electric arc that produces during for high-voltage breakdown provides energy, the pilot arc electric current.Prolong arc duration and reach 30ms at least.
The freewheeling circuit that boosts comprises capacitor C 1-C5, diode VD2-VD4, resistance R 2.By silicon stack VD1, the measuring junction of resistance R 2 and cable under test links to each other.Be mainly electric capacity and charge, store electrical energy.
High pressure is isolated and is comprised that the freewheeling circuit high pressure is isolated, the signal coupled high voltage is isolated, and the freewheeling circuit high pressure is isolated into silicon stack VD1, and the signal coupled high voltage is isolated into capacitor C 6.
Coupling of second pulse signal and protection; comprise pulse transformer T2, discharge tube V1, Transient Suppression Diode TVS1-TVS4; pulsed-discharge tube, Transient Suppression Diode TVS1 are connected in parallel on pulse transformer T2 input end, and Transient Suppression Diode TVS2-TVS4 is connected on the yi end of pulse transformer T2.
After the low pressure narrow pulse signal was coupled by pulse transformer T2, C7 entered cable under test through the high pressure isolation capacitance.Transient Suppression Diode TVS is in parallel with pulse transformer T2, shields.Pulse transformer T2 mainly is coupled to cable under test with the low pressure burst pulse of TDR emission.Provide trigger pip for TDR simultaneously.If unexpected the generation arranged, when high-voltage signal passes capacitor C 4, produce heavy-current discharge, deboost prevents from operating personnel and instrument are caused damage.
Compared with prior art, the beneficial effect that the utility model had is: can prolong the electrical discharge arc life period, make the high resistant of power cable and flashover trouble spot detect accurately simple in structure, low cost and other advantages.
Description of drawings
Fig. 1 is a schematic block circuit diagram of the present utility model;
Fig. 2 is circuit theory diagrams of the present utility model;
Fig. 3 is the high-voltage arc reflection configuration;
Fig. 4 is the second pulse waveform.
Fig. 1-the 4th, most preferred embodiment of the present utility model, wherein: K1 switch LED light R1-R4 resistance VD1 silicon stack T1 transformer T2 pulse transformer C1-C7 electric capacity V1 discharge tube VD2-VD4 diode TVS1-TVS4 Transient Suppression Diode.
Embodiment
As shown in Figure 1: this power cable high resistant and flashover fault test device, mainly comprise sending and receiving apparatus, High-voltage Signal Generator, cable under test, the high pressure input of High-voltage Signal Generator is isolated the back output terminal that links to each other respectively with high pressure isolation, the coupling of second pulse signal with high pressure and is linked to each other coupling of second pulse signal and sending and receiving apparatus with cable under test with trap, the freewheeling circuit that boosts.
As shown in Figure 2: input signal is connected to the measuring junction of cable under test through high-power resistance R1.Silicon stack VD1 and resistance R 2, diode VD4 is in series, capacitor C 4, C5 is in series, capacitor C 5 negative poles are connected on the centre of resistance R 2 and diode VD4, the negative pole of diode VD4 connects the positive pole of diode VD3, capacitor C 4 positive poles connect the negative pole of diode VD3, capacitor C 2, C3 is in series between the negative pole of the positive pole that is connected on diode VD3 and diode VD2, capacitor C 3 negative poles connect diode VD3 positive pole, capacitor C 2 connects diode VD2 negative pole, diode VD2 is coupled in transformer T1 output terminal by capacitor C 1, the plus earth of capacitor C 1, transformer T1 input end resistance in series R4, parallel connection power supply pilot lamp LED, be connected in series K switch 1 again, the high pressure input signal is by capacitor C 4 serial connection Transient Suppression Diode TVS1, and Transient Suppression Diode TVS1 is attempted by the yi end of pulse transformer T2, the other end of pulse transformer T2 also meets three Transient Suppression Diode TVS2-TVS4 that are in series, and T-903A links to each other with sending and receiving apparatus.
The freewheeling circuit that boosts comprises capacitor C 1-C5, diode VD2-VD4, resistance R 2.By silicon stack VD1, the measuring junction of resistance R 2 and cable under test links to each other.Be mainly electric capacity and charge, store electrical energy.
High pressure is isolated and is comprised that the freewheeling circuit high pressure is isolated, the signal coupled high voltage is isolated, and the freewheeling circuit high pressure is isolated into silicon stack VD1, and the signal coupled high voltage is isolated into capacitor C 6.
Coupling of second pulse signal and protection; comprise pulse transformer T2, discharge tube V1, Transient Suppression Diode TVS1-TVS4; pulsed-discharge tube, Transient Suppression Diode TVS1 are connected in parallel on pulse transformer T2 input end, and Transient Suppression Diode TVS2-TVS4 is connected on the yi end of pulse transformer T2.
After the low pressure narrow pulse signal was coupled by pulse transformer T2, C7 entered cable under test through the high pressure isolation capacitance.Transient Suppression Diode TVS is in parallel with pulse transformer T2, shields.Pulse transformer T2 mainly is coupled to cable under test with the low pressure burst pulse of TDR emission.Provide trigger pip for TDR simultaneously.If unexpected the generation arranged, when high-voltage signal passes capacitor C 4, produce heavy-current discharge, deboost prevents from operating personnel and instrument are caused damage.
The course of work is as follows: open K switch 1, after circuit powered on, power light LED was bright, begin to voltage-multiplying circuit charging, treat voltage rise to-930V about after, the High-voltage Signal Generator discharge, the negative high voltage signal enters cable under test through resistance R 1, and the trouble spot is punctured, and produces electric arc.Voltage on the cable sharply rises simultaneously, terminal voltage to be measured rises to-during the 930V left and right sides, silicon stack VD1 conducting, the stored electric energy of the electric capacity in the voltage-multiplying circuit discharges through the electric arc of silicon stack VD1 and resistance R 2 and cable under test generation, and the life period of electric arc is extended to more than the 30ms.Launch low pressure burst pulse through high pressure isolation capacitance C7 to cable under test by pulse transformer T2 this moment, carries out the Method of Cable Trouble Point distance test.