230 kV Operation of a Substation Designed for 115 kV by Controlling Voltage Transients

Present arrester technology enables the use of smaller clearances and insulation levels than are currently standardized for HV substation. This permits voltage uprating or compacting of substations such that substations can meet the safety standards. For the uprated substation the statement can be made that if it met the safety standards before uprating, it would automatically meet the standards after uprating. However, the relevant standards could be improved to clarify the interpretation, and promote flexibility of design. The W.G. on recommended clearances in substations has discussed the issues and set forth, in this paper, their views, which are intended to help the engineer involved with upratingkompacting safety. Brief comment on insulation coordination is given since this sets the bases for clearances. The needed choice of BIL values for the same voltage rating in the HV range is supported, making the safety clearance issue straightforward.

Safety aspects in substation voltage uprating

1992

Substation voltage upgrading

Panek¹,

Elahi²

1989

Needs, practices and possibilities for substation voltage upgrading are discussed. The survey of U.S. utilities shows significant activities in upgrading stations with operating voltages below 242 kV. The review of standards governing the present practices reveals substantially larger margins in insulation levels with lower voltages. If the BIL of substations rated below 242 kV is decreased by two steps, the margin will still be the same or better than that of 800 kV substations. Furthermore, application of ZnO arresters enables a substantial decrease in minimum clearances. A need for revision of presently required insulation levels and clearances for substations in the lower voltage range is identified.Such revision may open the door to economic benefits without compromising on performance of voltage uprated stations.

A simple approach to improve lightning performance of an uprated substation

Harrington

Mueen

1996

This paper presents a simple method to minimize lightning surges entering an uprated or compact substation. A severe lightnmg stress is caused by a backllashover in close proximity to the substation. Feasibility of uprating is based on the surge arrester technology available at present. However, some aspects of line design offer opportunities in reducing Gequency and seven@ of lightrwg surges imposed on the substation. The tower surge response adds an inductive 'overshoot' only during the front of' the stroke whch reduces considerably during the tail. If backflashover does not occur before reflections from adjacent towers anive, it is unlikely to occur at all. Use of guys and underbuilt ground wires in the limiting distance will produce reflections with larger maptude and reduce the effective surge impedance of the towes. Th~s would not only reduce backflashover frequency but will also r " i : . e crest and duration of surges entering the substation.