Reed switch protection of double-circuit lines without current and voltage transformers

Protection of 6-35 kV double-circuit lines from the supply side is suggested. It allows saving copper, steel, and high-voltage insulation in amounts unprecedented for relay protections. The protection is based on the control of sequence of actuation of reed switches fastened near the corresponding phases at a safe distance and of the time & UDelta;t between their actuation. The effect of all possible errors on & UDelta;t is studied and the number of reed switches required to be mounted near the phases of the lines is determined. The peculiarities of selection of & UDelta;t and inductions for the protection operation, points of reed switch mounting, sensitivity estimates, and the fields of use of the protection are analyzed. An example of the selection is considered. The protection operation algorithm is formulated and written in the form of switching algebra functions with allowance for the protection operability in the case of reed switch failures. The correct operation of the protection is shown in all actual modes of operation of the lines (including the failure of one of reed switches). A construction for fastening reed switches at a safe distance from the line phases is presented.