Abb Limited [Oil and Gas] manufactures Outdoor Square Shaped Window-type Current Transformer. Abb Limited [Oil and Gas] is an ISO 9001 certified company. The Outdoor Square Shaped Window-type Current Transformer, Model STBB-991 / 992, is a dry-type, solid-cast current transformer that operates with high accuracy for metering or relay applications. The Outdoor Square Shaped Window-type Current Transformer is an 8.7 kV, 75 kV BIL rated unit. The Outdoor Square Shaped Window-type Current Transformer has primary current ratios from 600:5 to 12000:5 at 60 Hertz [Hz] with a rating factor of up to 2.0.