Supply system voltage fluctuations caused by an AM transmitter load

The amplitude modulated (AM) broadcast transmitter is a varying electrical load on the supply system; the consequent voltage disturbances may be negligible if the supply system is strong, but if the system is weak the first cause for complaint from other consumers is the visible flickering of tungsten filament lamps. Research coordinated by the International Union for Electroheat (UIE) has enabled a disturbance analyser to be developed. The author presents the results of measurements carried out by EPD Consultants soon after the commissioning of a high frequency transmitting station on an island site. Planning calculations had indicated that flicker severity would not be excessive, but measurements were required as part of an agreement with the local electricity supply company. The results are used to derive guidelines for the fault level required at the point of common coupling (PCC) for amplitude modulated transmitters. This is particularly relevant when planning for high power transmitter capacity with supply from electrically weak supply systems