scope:

INTRODUCTION AND SCOPE

This manual is intended to bring to the attention of those seeking information concerning practices generally accepted in the petroleum industry, important features of electrical systems, based on generally acceptable electrical design, and installation practices which experience has shown result in safe, reliable, efficient, and economical operation of refinery equipment.

The refinery electrical system consists of various types of equipment, including switchgear, transmission lines, transformers, load centers, motors and controls. The proper application and installation of this equipment, taking into consideration short-circuit capacity, relay selectivity, suitable lighting, grounding, and lightning protection for safety of personnel and equipment, are essential to a dependable system.

The rapidly increasing dependence of petroleum refining upon electrical energy is shown by the fact that although crude-oil runs have increased 50 per cent in the last 10 years, electrical loads have more than tripled.

Reliability: The exceptional continuity of refinery process operations, couped with serious consequences of unscheduled shutdowns, determines the need for highly reliable electrical power systems.

Safety: Refinery electrical installation, in addition to being designed to protect against power failures, must also be designed to protect against electrical shock resulting from personal contact with energized conductors, and to prevent accidental ignition of flammable liquids of vapors released to the atmosphere.

Plant Expansion: System designers, initially, must provide for future increases of refinery power loads, because voltage levels, equipment ratings, and space requirements are affected.

Simplicity of Operation: The avoidance of complicated or dangerous switching operations is a big factor in safe and reliable plant operation during emergencies.

Equipment: The outdoor nature of refinery-processing installations dictates and need for carefully specifying materials, such as contacts, surface finishes, enclosures, and insulation, keeping in mind first cost and maintenance costs.

The recommendations of this manual shall not be considered mandatory. However, attention is directed to national, state, and local codes or regulations which usually set minimum requirements for electrical work.

The scope of this manual is limited to systems which supply electrical power to petroleum refinery utilization equipment. Instrumentation requirements are not discussed. Operating and maintenance problems are dealt with only insofar as they affect system and equipment selection. Reference should also be made to the following publications:

National Electrical Code

National Electrical Safety Code

API-RP 500: Recommended Practice for Classification of Areas for Electrical Installations in Petroleum Refineries

Proposed API Manual on Installation of Refinery Instruments and Control Systems

References: Where references is made to the National Electrical Code (NEC) or to any standard, or where any of these is applicable, it is recommended the reference be made directly to the full text of the current issue of that code or standard.