Method for replacing sections of electrically conductive phases in a DC two phase power system
The present invention relates to replacing conductors in a high-voltage power transfer system. The method provides, for example, a method for maintaining sections of electrically conductive phases in a direct current (DC) two phase power conductor line, wherein the two phases are parallel and spaced apart. The phases are strung between support structures and supported above the ground. Maintenance work, which include replacement or repair, is performed on sections of the two phases without interrupting a power load in any one of the three phases and without transposing the relative positions of the phases.
1. A method for maintaining one or more sections of electrically conductive phases in a direct current (DC) two phase power system without interrupting power in either of the two phases, the two DC phases denoted as A and B phases, and wherein the two phases are parallel and are spaced apart, and wherein the A and B phases have corresponding A and B loads and at least one of the A and B phases has, of the one or more sections, a section needing maintenance, and the A and B phases are strung between two support structures supporting the two phases suspended above a ground, the method comprising steps of:
(a) enabling a D phase located proximal to an existing one of the A and B phase needing maintenance by methods chosen from: providing a new D phase in the DC two phase power system adjacent the A phase when the A phase is the phase needing maintenance or de-energizing, the new D phase configured to be located proximal to the A phase needing maintenance, while the A and B phases are strung, so that the new D phase that is located proximal to the A phase needing maintenance becomes the D phase, and wherein the providing the new D phase includes: providing an auxiliary support structure substantially adjacent the two support structures and proximal the A phase, moving the section of the one or more sections of the A phase needing maintenance to the auxiliary support structure, stringing a new D phase section between the two support structures while removing the section of the one or more sections of the A phase needing maintenance from the DC two phases and treating the new D phase section to form an energized conductor,
wherein the stringing of the new D phase section further comprising:
providing a pulling line having at least one non-conductive end,
connecting the at least one non-conductive end of the pulling line to a leading end of the new D phase section,
providing first and second equal potential zones at opposite ends of a stringing path where along the new D phase section is to be strung, wherein the first and second equal potential zones are grounded,
electrically connecting the pulling line to the first equal potential zone, electrically connecting the new D chase section to the second equal potential zone,
electrician connecting pulling equipment at the first equal potential zone to the first equal potential zone and electrically connecting pay-out equipment at the second equal potential zone to the second equal potential zone,
pulling the pulling line along the stringing path using the pulling and payout equipment so as to pull the pulling line into the first equal potential zone while paying-out the new D phase section along the stringing path from the second equal potential zone,
(b) paralleling with and transferring a power load carried by the phase needing maintenance to the D phase by:
(i) initiating transfer of the power load by establishing a parallel electrical connection between the phase needing maintenance and the D phase through a pair of jumpers extending in electrical connection between the phase needing maintenance and the D phase wherein the pair of jumpers do not cross over the other energized phase in the DC two phase power system; and
(ii) completing transfer of the power load to the D phase by de-energizing the phase needing maintenance; and
(c) maintaining the de-energized phase needing maintenance while maintaining its position relative to other phase in the DC two phase power system.
2. The method of claim 1 , wherein a first lateral distance between the new D phase section and the section of the one or more sections of the A phase needing maintenance supported on the auxiliary support structure is substantially no less than a phase-to-phase lateral separation.
3. The method of claim 1 , wherein the section of the one or more sections of the A phase needing maintenance strung on the auxiliary support structure is substantially parallel to the new D phase section strung between the two support structures.
4. The method of claim 1 , wherein the at least one non-conductive end of the pulling line is a flexible electrical isolator.