Underground service cables are at the interface between the supply authority and the consumer, and the cables differ according to where the line of demarcation is drawn between the supply authority responsibilities and those of the consumer. Originally intended for residential consumer applications, these types of service cables have been extended to light commercial applications, and even some specialized industrial applications. The constructions outlined here may differ in detail, but the purpose is the same whether the supply authority or the Canadian Electrical Code governs the service.
The residential consumer is typically serviced with a centre-tap 240/120 volt single phase system. Commercially and industrially the system is more likely to be three-phase, and carries the extra insulated conductor in the assembly. Power is most often derived from an overhead pole mount transformer, a pad mount transformer at grade level, or a submersed transformer. The cables are run underground to connect the secondary side of the transformer to the terminals of the meter base at the dwelling.
Most cable constructions feature 90°C rated cross-linked polyethylene insulation due to its mechanical ruggedness, excellent low temperature handling and high level of resistance to overheating. Some utilities and other end-users install products with 75°C rated thermoplastic polyethylene insulation, which are satisfactory when there is no risk of overheating. All standard products feature compact conductors, carry a minus 40C low temperature rating, and are rated 600v.
Multiplexed assemblies of polyethylene and cross-linked polyethylene-insulated, individually PVC-jacketed aluminium conductors have been used in underground service applications for many years, particularly in eastern Canada. These constructions grew out of the Ontario Hydro constructions designed in accordance with their requirements contained in their specification M-302. The CSA standard C22.2 No. 52 adopted these constructions and re-defined them according to the broader needs of a national standard of Canada. These constructions consequently were recognized in the Canadian Electrical Code for underground services.
Cables are commonly available in triplexed form (three insulated, jacketed conductors), but quadruplexed constructions are available on request. The neutral conductor of the multiplexed conductors is insulated, a feature which is responsible for the "I" in the USEI75 and USEI90 type designation. The application of the jacket over the individual conductors, rather than over the assembly of insulated conductors, is responsible for the comparative flexibility of the cables. Coloured PVC is supplied as a standard feature to satisfy CEA specification requirements, and the products are dually marked, but black is standard on CSA type designations which are not dually marked. Full size neutral conductor sizes are standard, but a reduced neutral conductor is available on request.
Several years ago, electrical utilities represented by the Canadian Electrical Association decided to incorporate the utility variations on the foregoing constructions in a national specification,WCWG-04. They were provided with utility type designations carrying the prefix "USC", a descriptor intended to represent "Underground Service Cable". Tests commensurate with the needs of utilities were adopted at the same time. The circle has been completed with the offering of products in triplexed assemblies, providing the simultaneous satisfaction of both utility and electrical code requirements. These products are dually marked to indicate acceptance by each jurisdiction. All dually marked products are provided with compact NUAL conductors for the highest level of connection performance and flexibility.