Power-line checks

Checks in the Power lines section lists every problem, red for what fails and amber for warnings. Click one to select the line, support, cable or equipment it is about; failing supports and spans are ringed in red on the plan while the workspace is open.

Clearances

The conductor's lowest phase is followed along every span at every load case. Its lowest clearance over the ground must reach the line's Clearance rule. Where a span crosses an obstacle (drawn with Obstacle: a point or a line, with its height above the ground and its own clearance rule), the clearance over the obstacle's top is checked the same way.

What the Landscape workspace puts above the ground counts too. Single plants (their crown at mature spread and height), hedges and planting beds (the tallest species in them) and walls (their top) are obstacles under a line, without drawing them again. They keep the rules set in Load cases and limits…: Landscape plants under a line (the example sets use Trees and plants, 3 m) and Landscape walls under a line (Building); choose Not checked to leave them out. The clearance is measured straight up from the top of the plant or wall to the conductor where the span crosses it; the distance sideways to a crown beside the line is not checked. Moving a tree or raising a wall changes the checks at once.

Your clearance rules are your own: open them with Rules… beside any Clearance rule (or Load cases and limits…) to add, rename, change or remove them.

Spacing and swing

• Phase spacing needed: k·√(sag + insulator length) + U/150, with the hot case's sag and the voltage U in kV (a common form; k is your rule set's). Compared with the crossarm's phase spacing.
• Insulator swing on suspension supports, under the wind case: atan(transverse load ÷ vertical load), against the rule set's largest swing.
• Uplift: a suspension support lower than its neighbours can be pulled up in the cold; it is flagged.

Support loads and sizing

For each support and load case, with every conductor of the line:

• Transverse: wind per metre × the wind span (half of the two spans), plus 2·H·sin(turn ÷ 2) at a turn.
• Along the line: the difference of the two sides' tensions at a dead-end or angle; at a suspension support only under ice on one side (each span worked on its own, which errs on the safe side).
• Vertical: the vertical load per metre × the weight span (between the lowest points either side) plus the equipment.

The horizontal load is taken to the support's nominal point (equivalent load = load × attachment height ÷ height of the nominal point) and compared with its nominal load × the rule set's factor. When it is too weak, the smallest support of the same material in your library that carries it is suggested. A support with a stay passes the horizontal load to the stay, which carries load ÷ sin(stay angle) and is checked against its own rating.

Fittings (clamps, insulators, crossarms) are checked against their rated load: an anchoring fitting carries the conductor's tension, a suspension fitting its share of the vertical and transverse load. The foundation shown is the support's depth in the ground and a hole a little wider than its foot.

Data, connections and current

• An item with a needed field empty, or a key that is not in the library.
• A cable route end, or equipment, connected to nothing.
• Voltage drop and current from each source (equipment marked as a source) to the loads (kW and power factor on equipment), along overhead spans and cables: √3·I·L·(R cos φ + X sin φ), with R at 20 °C. More than the cable's current rating, or more drop than the rule set allows, is flagged.