Abstract :
The paper draws attention to the desirability of clear definition of such terms as power factor, kVA, etc., with regard to tariffs. Ambiguities are possible, and Sections (1) to (6) deal with those relating to polyphase power factor. The ¿ vector sum ¿ and ¿ arithmetic sum ¿ definitions of 3-phase power factor are stated, and a hypothetical 3-phase case is considered in order to support the contention that the latter definition is more advantageous as a tariff basis than the former. A suggestion is made with regard to the basis of a tariff when there is diversity of incidence of demand on individual phases. Sections (7) et seq. deal with the use of sine and cosine meters and the possible ambiguities resulting from variable power factors. Two single-phase meters on 3-phase balanced loads give rise to the same ambiguities from the same cause. A table of figures and a set of curves are given exhibiting the range of errors which may result in estimating kVA-hours and average power factor from these combinations of meters. The conclusion is drawn that it is not advisable to use them in certain circumstances. Section (17) summarizes the author´s opinions on current practice in kVA measurement. Appendix 1 contains observations relating to the ideal neutral point of a 3-phase system when no real neutral is accessible.
