This publication provides over 200 pages of technical guidance for electrical and mechanical engineers and other professional engineers and construction managers interested in operation and maintenance of auxiliary electric power systems and equipment. Here is what is discussed: 1. INTRODUCTION, 2. EMERGENCY POWER SYSTEMS, 3. PRIME MOVERS, 4. GENERATORS AND EXCITERS, 5. SWITCHGEAR, 6. OPERATION AND MAINTENANCE, 7. LUBRICATING OIL PURIFICATION