IEEE Std C37.95:2002 pdf free download

IEEE Std C37.95:2002 pdf free download.IEEE Guide for Protective Relaying of Utility-Consumer Interconnections.
3.3.3 Future utility system changes
The utility should inform the consumer of any substantial utility system changes. For example, the installation of a large transformer that alters short-circuit currents at the supply point may affect the consumer’s power system.
3.4 Specific supply considerations
In determining the final supply method, consideration should be given to the design of the interconnection. the arrangement of the utility’s supply system. its protective relaying requirements, and its maintenance requirements and responsibilities.
3.4.1 Division of ownership
Individual operating and maintenance philosophies of the consumer and utility may impact electric system design. Regardless of ownership, however, the protective equipment should be specified and designed to provide a coordinated system. Proper engineering design must not be compromised, but the protection of the utility-consumer interconnection facilities should satisfy the objectives of both parties. In all cases, the protection requirements, equipment specifications, relay settings, fuse ratings, station battery requirements, and testing procedures should be discussed and agreed on by both parties.
3.4.2 Supply line reliability
Line length. construction, fault clearing times, and utility transmission system configuration all affect the supply line reliability. Reliability requirements should be determined based on both long-term and momentary outages.
3.4.2.1 Long-term outages
Long-term outages result from equipment failures that require an extended time to repair or replace. If a utility-consumer irnerconnection consists o1 a single line supplied from a single source connected to a single transformer, it is subject to long-term interruptions due to forced or planned outages of the supply source. line, or transformer. To reduce the possibility of long-term outages, a second supply line may be considered, This can, for example, be provided by
a) Two lines from separate utility sources
b) Two lines derived by sectionaliing an existing utility tie line
Continuity of service will be further enhanced by the addition of a second transformer. The service to the consumer can be arranged so that it is normally provided by one source with standby supply from the second. This enables restoration of service by automatic or manual switching operations upon the failure of the principal source of supply. Another alternative is parallel operation with two full-capacity lines and transformers. These and other supply configurations are covered in detail in Clause 4.