A novel approach for optimizing dead time of extra high voltage transmission lines

Reducing dead time of high voltage power transmission lines is one of the most important issues in power system protection. Besides, need for reducing the dead time is a matter of grave concern to increase voltage level of power transmission lines and insulation coordination. In this paper, different methods for decreasing the capacitive coupling and consequently reducing the dead time of power transmission lines are compared. This leads to faster quenching of secondary arc and limit the transient over voltage. Moreover, a novel hybrid approach is presented for reducing dead time of power transmission lines and faster quenching of secondary arc current. Simulations performed in electromagnetic transient program are performed for different cases. Simulation results show that dead time is reduced appropriately by proposed method.

I. Introduction

Nearly, 70% to 90% of faults in high voltage Power Transmission Lines (PTLs) are intrinsically transient. The most prevalent potentials of transient faults are lightning and jiff contact of PTL with external objects. A Single Line to Ground (SLG) fault in one phase of PTL and subsequently opening of faulted phase can cause overvoltage in this phase [1]–[5]. This transient overvoltage results in a high amplitude current named secondary arc current when breaker is open [6]. This current causes longer presence of arc and prevents its rapid quenching. The voltage created in opened phase is depended on [7]: •

Capacitive and inductive coupling between line's phases which depend on line geometry, length and distance between phases,

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Operational conditions in prefault including line load current, line's voltage and etc,

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Short Circuit Capacity (SCC) from viewpoint of buses and

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Location of SLG fault (experimental tests show that the secondary arc current is minimum in the middle of transmission line).