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The lightning performance on four 500/220-kV segments of quadruple circuit lines on the same tower of Nanyan line is analyzed by traveling wave method and electric geometry method in this paper. The results indicate that double-circuit 220-kV transmission line protect double-circuit 500-kV transmission line because of different insulation protection, the lightning-understanding level of 220-kV line...
The detection system in substation of medium voltage overhead line can mostly detect only low impedance fault, neither broken conductor on the source side with high impedance, nor broken conductor on the load side with even direct to ground. This paper presents novel method to characterize such faults using time shifting in 3 phase line current. It can be applied, however, in parallel with the conventional...
Re-close scheme of transmission lines has been researched for many years, with the fast development of cities, more and more combined distribution lines composed of transmission line and cables are applied into electrical power network. A new smart re-close scheme of combined distribution transmission lines is put forward. The scheme comprehensively applies inferred voltage module and traveling wave...
Quality of electricity is of increasing importance within conditions enabling to maintain it to an even less extent. Now consumers neither tolerate outages with duration of seconds. This fact forces the electric utility companies to maintain network operation during single-phase earth faults. This paper presents the results of a joint research investigating the potential of overhead line poles during...
A new method is discovered for calculating the fault distance of the overhead line of the Neutral Indirect Grounded System (NIGS) in power distribution networks, in which the single phase to ground fault point or distance is difficult to detect, because the zero sequence current is in lower value. It is found that the information of the fault distance is kept in the zero sequence voltage vector which...
This paper puts forth a framework for estimating the transmission line parameters (including series resistance and reactance and shunt susceptance), line temperature and sag employing synchronized phasors obtained by Phasor Measurement Units (PMU) in real time. The estimated temperature and sag can be utilized for dynamic thermal rating for increased power transfer. The proposed algorithms harness...
The question of improving efficiencies of operation is nowadays more than ever considered a very critical issue. This is because losses have acquired recently an extra cost that of the CO2 release penalty. It is well known that a good portion of the electricity required to operate a power grid is spent as Overhead Line (OHL) power losses. In this paper the key points of the theory of maximum OHL transmission...
Overvoltages arising in 150 kV and 400 kV GIS substations due to backflashover of the incoming overhead transmission lines were computed with the aid of ATP-EMTP simulations, by considering the effects of several simulation models of the basic transmission line components. The protection offered against impinging surges by surge arresters operating at the substation entrance is evaluated with respect...
Analysis of induced voltages on transmission tower and conductors has been performed when a high voltage line is subjected to propagation of lightning transient. PSCAD/EMTDC software program is used to carry out the modelling and simulation works. Lightning strikes on the tower top or conductors result in large overvoltages appearing between the tower and the conductors. Two cases considered for these...
This paper analyzes the lightning performance of 22 kV, ChiangMai substation 4 to Doi-Suthep, overhead distribution line with covered conductors. The performance of line which related to the insulator flashover has been modeled and analyzed using EMTP. The backflashover rate (BFOR), shielding failure flashover rate (SFFOR) and induced voltage flashover rate (IVFOR) of line have been determined. The...
A novel fault finding correlation methodology, using pseudorandom binary sequences (PRBS), is presented as an alternative to time domain reflectometry (TDR) for multi-core power cable fault location and identification. The fulcrum of this method is the cross correlation (CCR) of the fault echo response with the input pseudonoise (pN) test sequence which results in a unique signature for identification...
The paper deals with the temporary overvoltages that build up in radial MV distribution networks following the inception of a 1-phase-to-ground fault (1-Phi -to-Gr). For extended cable/overhead MV distribution networks with ungrounded neutral, in case of low resistance faults at critical stretch of overhead lines, in [1] it has been evidenced that the temporary overvoltages on healthy phases can be...
The paper makes an analysis of the eighteen 220 and 400 kV overhead electric lines belonging to C.N. Transelectrica - Sibiu Branch (TSO) on the basis of a unitary methodology for assessing their technical state and taking into consideration the different types of expertise conducted until now, including the multispectral analysis from the helicopter of seven lines. Performance criteria for insulators,...
Because of the necessity to perform maintenance on one of the circuits of the high and very high tension double circuit lines that have one of the circuits operational, a case that lately becomes more frequent, the calculation of the currents and induced tensions in the circuit's conductors that is under induction is required to establish safety working conditions. This paper does not intend to modify...
Dry-band arc resistance determines the quality of fiber optic cable insulation materials. Three different brands of ADSS fiber optic cable qualities are determined with IEEE 1222 standard test method. Results give a ranking of the cables. During the experiment, it is noticed that randomly spread water droplets are a factor for the results. Therefore, the same cables are tested with another standard...
The overvoltage stresses due to lightning impulse has been studied by using simulation tool and a typical Thailand subtransmission system. The effect of lightning is considered as back-flashover at the insulator and shielding failure. Then, transmission line, tower, switchgear and transformer are modeled together as a system. The effect of tower footing resistance, underground cable connection between...
If lightning strikes on an overhead line connected with a cable, an over voltage will invade into this cable and induct an over voltage in its metal sheath. The sheath-lightning-overvoltage (SLOV) under one-terminal-grounding connection (OTGC) and cross-bonding connection (CBC) are simulated; and impulsive test was undertaken in real cable of Guangzhou power system. However it is hard to get the exact...
Having been learned a lot from the previous work , this paper proposed a new medium-frequency current ice-melting method employing skin effect and proximity effect phenomena to overcome the weaknesses of existing de-icing method of overhead line. By the interaction of the two phenomenon, the transmission line unit resistance is expected to increase, compared with the working frequency current, the...
This paper describes shielding method for lightning protection on high voltage transmission line and also how to protect lightning effects on the line. If the fault is present, additional power system will be damaged and minimizing system reliability. This shielding method used in transmission line bases the unequal lightning ground flash density all over the country. This paper is tend to specialize...
A novel pulse tester correlation strategy, using pseudonoise (pN) sequences, is presented as an alternative to Time Domain Reflectometry (TDR) for multicore power cable fault location and identification. The fulcrum of this method is the cross correlation (CCR) of the fault response echo with the input pN test excitation which results in the extraction of a unique signature for identification of the...
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