Automatic printing Ammeter

A new instrument has been developed which will automatically read and record in numerals, at predetermined time intervals, the ampere loading on 50 different electric circuits. This instrument also adds the readings on groups of circuits and prints these totals in columns beside the ampere load readings. The paper outlines briefly the reasons for developing such a device. The paper also describes, with the aid of schematic diagrams, the process by which the instrument obtains and prints all the measurements and totals on a single “log sheet.” Need for Compact Ammeter Records The rating of most electrical equipment is on an ampere basis. To determine when additional capacity in lines, transformers, or generators, is required on a power system, it is necessary to have an accurate record of past ammeter loads. For maximum usefulness, these ammeter records should be as compact and legible as possible for ready determination of the shape of the load curves and rate of growth. In large power stations it is common practice for an operator to note and record on a “log sheet” the ammeter readings on all outgoing transmission lines at frequent intervals. When several of these outgoing lines supply the same load it is necessary to totalize the loads on all lines in a given group in order to estimate the load growth on the combined group. Figure 1 illustrates a typical group of substations fed by several lines from the same generating station. When 50 to 100 or more lines emanate from the same station the instrument readings must be recorded with a minimum of effort and in the most usable form. Recording instruments would be suitable for this purpose if their record could be compact enough.