Lightning shielding failure and back flashover recognizing method of overhead power transmission line
The invention discloses a lightning shielding failure and back flashover recognizing method of an overhead power transmission line. The method includes the steps of firstly, obtaining the level difference of an insulator string and a buried current signal of a tower; then, judging the position of a lightning strike according to a lightning strike position feature value; finally, judging a lightning shielding failure and a back flashover, wherein when a lightning strike point is located on the top of the tower and a first minimum value is smaller than a threshold, back flashover occurs in the tower, when a second minimum value is smaller than the threshold, back flashover occurs in an adjacent tower, otherwise, no faults exist in the back flashover, when the lightning strike point is located on a wire and the first minimum value is smaller than the threshold, the lightning shielding failure occurs in the tower, if the second minimum value is smaller than the threshold, the lightning shielding failure occurs in the adjacent tower, and otherwise, no faults exist in the lightning shielding failure. The method achieves lightning shielding failure and back flashover recognition on the condition that the lightning strike is faulty or not faulty, the recognition result can detect the lightning-prevention effect of lines, and lightning-prevention design and isolation matching are improved before faults specifically. According to the method, only time domain features are extracted, calculation is simple, physical concepts are clear and visual, and the method is easy to achieve. 1. Overhead transmission line method for identifying the thunder and lightning, characterized in that comprises the following steps: S1: load place cross through the mounting for the non-contact voltage sensor to obtain the insulator string potential difference signal, through the four pole tower Roche eliminating the tower coil to obtain the total current signal; S2: normalization processing the insulating string are potential difference and the pole tower lightning current signal and calculate the time of the 1st phase insulator potential difference between the effective value U1 Uins minimum 1st, and 2nd time of the lightning strike occurs all-phase insulator potential difference U2 Uins 2nd minimum value of the effective value; S3: processing the insulating string according to the normalized difference current signal are judged and tower lightning strike point position; S4: when the thunder stroke spot position is located in the tower when the top of the tower, U1 judge minimum 1st Uthres is less than a preset threshold, if it is, is the base poles and towers counterattacks flashover; S5:if not, judgement 2nd minimum value U2 Uthres is less than a preset threshold, if it is, then the neighbouring tower strike back the flashover; if not, the counter of the circuit is not fault; S6: thunder stroke spot position located on the wire; the minimum 1st U1 Uthres is less than a preset threshold, if it is, is the basic tower lightning flashover; S7:if not, judgement 2nd minimum value U2 Uthres is less than a preset threshold, if it is, then the neighbouring tower lightning flashover; if not, the failure of the circuit is not fault. 2. Overhead transmission line method for identifying the thunder and lightning according to Claim 1, characterized in that the stated step S3 thunder stroke spot is in the position of the is judged through following steps: S31: translation along the axis of ordinates the Uins, so that its initial value is zero, calculating the time difference of the insulator t Uins waveform after the occurrence of lightning strikes on the axle in the region surrounded by the 1st 1st area S1; S32: if 1st area S1 > 0, the potential difference of the insulator Uins > 0, direction 1st Di=+ 1 ; if the 1st area S1 < 0, the potential difference of the insulator Uins < 0, direction 1st Di=-1; The direction of the insulator string wherein 1st Di Uins the two ends in the direction of potential difference; S33: computing tower Ig are t current waveform with the time after the occurrence of lightning strikes on the axle in the region surrounded by the 2nd 2nd area S2; S34: if 2nd area S2 > 0, scaling current Ig the tower > 0, Dt=+ 1 2nd direction; if the 2nd area S2 < 0, scaling current Ig the tower < 0, direction 2nd Dt=-1; Dt wherein 2nd direction to the direction of the current are Ig tower; S35: the 1st and 2nd direction Di Dt direction shall makes the product D lightning strike position characteristic value, if lightning strike position characteristic value D=-1, the lightning strike position is located in the wire; D=+ 1 position characteristic value if struck by lightning, the lightning strike position is located in the tower top of the tower. 3. Overhead transmission line method for identifying the thunder and lightning according to Claim 1, characterized in that the all-phase insulator potential difference Uins effective value is calculated through the following formula: In the formula, expressed Urms phase voltage effective value, calculating N the number of data points in the section, the section calculating k in article k data points, U (n) in the section for calculating the value of a data point. 4. Overhead transmission line method for identifying the thunder and lightning according to Claim 1, characterized in that the pre-set threshold value of the parameter according to the specific Uthres the transmission line. 5. Overhead transmission line method for identifying the thunder and lightning according to Claim 1, characterized in that the time of the 1st to the lightning 5 us of after 100 us inner, the 2nd period of the lightning 1.5ms of the 1ms inner. 6. Overhead transmission line method for identifying the thunder and lightning according to Claim 1, characterized in that the stated 1st zone time is the time after the occurrence of lightning strikes on the axle t 1.5 us interval; the 2nd t zone time is the time after the occurrence of lightning strikes on the axle 20 us interval.