PROTECTIVE RELAY COORDINATION 349publish their curves showing the tolerances in the performance of their relays. These tolerances are
shown as a band or range about a nominal curve. From a recent survey of relays and circuit breakers
it was found that the tolerances and adjustments can be illustrated as shown in Figure 12.21.
Note: The characteristic between points A and B may be a horizontal line, a straight sloping line or
an inverse curve.
References
1.Applied protective relaying. Westinghouse Electric Corporation, 1976 Relay-Instrument Division, Newark,
NJ 07101. Library of Congress Card No. 76–8060.
2.COMBIFLEX generator protective relaying. Pamphlet RK 64–200 E Edition 1. ASEA, now part of ABB
(March 1980).
3.Protective relays application guide. Third edition, reprinted March 1995. Alstom T&D Protection & Control
Ltd, Stafford, UK.
- J. Lewis Blackburn,Protective relaying principles and applications. Marcel Dekker Inc. (1987). ISBN 0
824-77445-0
5.Generator system grounding. Low or high impedance?Pamphlet KK 318–502 E Edition 1. ASEA, now part
of ABB (March 1970). - R. Ball and G. W. Stephens,Neutral earthing of marine electrical power systems. Institute of Marine Engi-
neers UK. Trans. I Mar E, 1982, Vol. 95, Paper No.32. - W. C. Bloomquist, K. J. Owen and R. L. Gooch,High-resistance grounding power systems – why not? IEEE
Transactions on Industrial Applications.Vol. IA-12, Paper No.6, 1976. - A. R. Kelly,Allowing for decrement and fault voltage in industrial relaying. IEEE Transactions on Industrial
and General Applications.Pages 130 to 139, March/April 1965.