page_57

< previous page | page_57 | next page >

Page 57

| Ammeters |

| Other means of monitoring the loads carried by a transformer include measurement of either primary or secondary currents by ammeters and by the measurement of the collective energy of the loads connected to it. |

| Ammeters may be of the instant-reading type, the recording type, or the maximum-indicating type. The first type indicates the current carried at the particular times of reading. If the time chosen corresponds to well-known periods of peak load, the reading may suffice to give some indication of the load condition of the transformer. The recording ammeter provides a graphic record of the load carried by the transformer over a period of time, from which peak conditions as to magnitude and duration may be observed. The maximum-indicating ammeter is installed over a period of time and essentially is an indicating ammeter with a second free-floating needle which, being pushed by the indicating needle, is left in the maximum position to which it is pushed; it is a more economical device than a recording ammeter. Records of ammeter readings serve to indicate progressive changes in transformer loadings and call attention to possible approaching critical conditions. |

| Transformer Load Monitoring.. |

| Computers have made possible the reading of the energy consumed by the several loads (consumers) connected to the transformer. The individual meter readings used for billing purposes are added together in the computer to give an approximate total amount of energy supplied by the transformer to which they are connected. From test patterns developed separately, a factor is determined which, applied to the total energy consumption, enables the approximate calculation of the load current carried by the transformers. This operation is known as transformer load monitoring. |

| Ambients |

| As the safe operation of a transformer depends on how hot its insulation is permitted to become, the readings of load amperes provide only an approximate method of determining the adequacy of the transformer to supply its load safely. Both the ambient temperatures and the time and duration of the peak loads supplied have an effect on the internal temperature of the transformer. Evening periods are usually cooler than day time; winter is cooler than the other seasons. Summertime ampere readings may tend to give deceptive indications of the real transformer condition since the ambient temperature may be high; air-conditioning loads may impose peak loads of very long duration, sometimes approaching twenty-four hours. |

< previous page | page_57 | next page >