Carrier-current losses on 132-kv line

Abstract

the Public Service Company of Northern Illinois have an interconnecting 132-kv power line over which a reliable carrier transmission channel is desirable.The carrier channel difficulties arise chiefly from the 5.8 miles of 600,000-circular-mil paper-insulated oil-filled leadcovered cable extending out from Northwest Station. This Chicago city limits (see Figure 1); the line tap at Skokie Substation; the normal overhead conductor attenuation; and the carrier terminal equipment loss at Station 6 in Waukegan. Losses and changes in attenuation also result from two other 132-kv lines that parallel the overhead section; line noise is increased by a nearby electric railway.The carrier losses were measured in each component ofFigure 1. One-line diagram of underground-cable overhead-conductor 132-kv line and diagram of cable sheath connections NORTHWEST STATION o UJZ-I Ξζδ WATTS:-100-■ _ιϋ PER UNIT: DB LOSS 0.9 1.7---WATT LOSS 18.72 --26.38-length of cable would not be particularly difficult were it not for the fact that it is equipped with sheath bonding transformers which are used to reduce circulating currents in the sheaths. This avoids decrease in cable load capacity. However, the sheath bonding transformers present a very high loss return path to carrier-frequency currents. The overhead section of the line is 31 miles in length.Adding to the carrier problems are the increased terminal equipment losses at Northwest Station. These losses are greater than for an overhead line terminal, because of the fact that the carrier energy is fed into the low-impedance cable. The test results at Northwest Station show that 71 per cent of the available carrier energy at 75 kc is lost in the terminal equipment before reaching the 132-kv cable.Other factors that contribute to the carrier transmission losses are: the cable-overhead conductor mismatch at the