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Travelling wave based protection is becoming attractive in ultra-high voltage (UHV) transmission systems due to the requirement for high-speed protection. However, the poor transfer characteristics of coupling capacitor voltage transformers (CCVTs) for high-frequency voltage have strictly limited its application. A travelling wave based protection prototype considering the characteristics of CCVTs...
In this paper, real-time information record mainly includes real-time current and voltage waveform record, switch signal record, traveling wave record and weather condition record. When distribution network works in different states, the detected current and voltage waveform also are different. To some degree, waveforms can reveal a lot not only the real-time operating state of distribution network,...
When faults occur on the circuit to which the distributed generation (DG) is connected, the circuit breaker of power distribution system trips the faulted circuit, and forms DG islanding. This paper examines the performance of anti-islanding protection based on asymmetric tripping of feeder circuit breaker under fault scenarios. Considering that the protection relay equipped by DG such as overcurrent...
Travelling wave protection is one of the most attractive line protection techniques in high voltage direct current (HVDC) transmission system. However, it has a low sensitivity in high impedance fault conditions as the initial wave is insignificant. This paper presents a non-unit fault protection principle based on the initial wave as well as the reflected waves to improve the protection sensitivity...
Current travelling wave based single-ended fault location method needs to recognize the travelling waves propagating from the fault direction as well as the travelling wave reflected from the fault point or remote-end bus. This paper firstly compares the current travelling waves of the fault line and the longest health line connected to the local bus based on dyadic wavelet transform to obtain the...
Single Line to Ground (SLG) faults in non-effectively grounded networks are difficult to detect. Immune to neutral point grounding type, load conditions and system operation conditions, traveling-wave based method is an effective fault line identification method. However, due to the strong coupling between the double-circuit lines, the wavefront magnitude of them are the same, and the polarity of...
Travelling wave based line protection has the advantage in fast response speed, however, its performance in practice is still unsatisfactory due to the high frequency limitation characteristic of coupling capacitor voltage transformer (CCVT). This paper presents a directional comparison protection principle based on travelling wave, which utilizes the polarities of high frequency current and low frequency...
Identification of the travelling wave reflected from the fault point or the remote-end bus is the core of travelling wave based single-end fault location method. Because the polarity of the travelling wave reflected from the fault point or the remote-end bus is affected by the bus configuration at both ends of the fault line, it is difficult to identify whether the travelling wave is reflected from...
Identification of the wave fronts is the precondition of travelling wave based fault location. Many factors may affect a precise identification of the wave fronts, among which the transfer characteristics of the secondary circuit are in focus. The resonance nature of the secondary circuit which consists of current transformers and secondary cables causes certain noises in the recorded travelling waves...
Wave-head characteristics of the fault-generated travelling wave on transmission line in different frequency bands are studied by using wavelet multi-resolution decomposition in this paper. Firstly, the travelling wave process on transmission line is analyzed and the fault-generated travelling wave is described by analytical expression. Then, the fault-generated travelling wave is decomposed into...
This paper figures out the analytical expression of the travelling wave caused by the fault on a transmission line. With the help of the expression, how the different fault situations (including fault type, fault position, fault transition resistance, fault voltage phase angle, bus structure, etc.) can influence the performance of the travelling wave fault locators is discussed. In the paper, a simulation...
A typical radial ungrounded distribution network model is set up in the 10kV true type distribution network fault simulation laboratory. Through a series of single-phase-to-ground fault tests, the zero sequence and three-phase voltage and current waveforms of traveling wave and power frequency are obtained. Wavelet multiresolution analysis is used to decompose the current and voltage traveling waves...
An islanding detection method in ungrounded power distribution system based on single-phase operating mechanisms of the circuit breaker (CB) is proposed in this paper. When CB opens three phase circuits to form an island, one phase circuit is opened firstly and the other two phase circuits are opened secondly after certain duration. During the period when only one phase circuit is opened, negative...
This paper proposes a new fault location algorithm based on two-phase voltage and current measured at the power system side for unbalanced power distribution systems. Taking single-phase-to-ground fault as an example, the paper elaborates the algorithm for feeders with and without laterals. A simple feeder in power distribution system and IEEE-13 node power distribution system are used as test systems...
The paper presents traveling waves based fault forecast for feeders in power distribution system. Firstly, the paper introduces field fault phenomenon from intermittent traveling waves to permanent power-frequency voltage or current change. Then the basic principle of fault forecast is proposed based on detecting disturbance generated traveling waves occurrence frequency in one feeder. Further the...
Backup protection is indispensable, particularly as for adjacent devices. Unfortunately, the backup protection has played a negative role during the overload and power swing, and sometimes caused the cascading tripping blackouts. Therefore, it is necessary to re-recognize the role and the scheme of backup protection. This paper presents an integrated backup protection scheme, which separates the backup...
It is very difficult to correctly identify single-phase-to-ground fault (SFG) in distribution system with neutral non-effectively grounded (NNG). A novel travelling wave based single-phase-to-ground protection is proposed in the paper. The polarity of initial transient current and voltage travelling waves are used to identify the fault direction, and power frequency voltages are used to distinguish...
Travelling wave protection, which performs brilliantly with high operation speed, is perfectly feasible for ultra-high voltage (UHV) transmission line protection. Since nearly 70% faults in UHV transmission lines are single-line to ground (SLG) faults, the cooperation of single phase tripping and auto-reclosing is the most common and effective method to isolate SLG faults and improve the stability...
Effective analysis method is required to analyze the entire traveling wave (TW) process, which includes the initial and succeeding TWs. As TW directional protection only uses the initial TWs to avoid potential confusion that may be caused by the aliasing of TWs, a long-term reliable criterion is difficult to offer. Thus, this paper proposes an analysis method for the whole TW process based on an equivalent...
Surge Impedance Relay(SIR) is applied to DC system. Characteristics of SIR in DC line are analysed. A DC SIR algorithm implementing wavelet transform applied to HVDC line protection is proposed. The feasibility of DC SIR is verified and the performance of DC SIR is simulated and analysed.
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