Simplified stability analysis of a distribution system in a chemical plant with induction motors

The need for a simple method of stability analysis has become apparent now that the problem of voltage-dip protection is often encountered. Simplifying assumptions such as approximate vector addition, neglecting motorfault contributions and transients, are explained. The stability of a typical plant after a voltage dip is then calculated by slide rule using only motor torque/slip and current/slip curves. The results agree well with those obtained by a rigourous computer study. Methods of improving plant stability and points to be noted in the design of ancillary equipment are briefly noted.