Protection and earthing of the electrical power systems at Marian mill

The electrical power generation and distribution systems at Marian Mill were expanded to cope with an increase in crushing rate from 450 to 670 tonnes of cane per hour. To achieve the required expectations of power demand, a design figure of 12,000 watts (12 KW) per tonne of cane per hour was used to predict factory loadings. The expansion required the installation of an additional 12 circuit breakers at 11 KV and six 11,000 volts to 415 volt substations. As well, provision was made for the installation of future generation of 5 megawatts (MW) at 11 KV and a standby diesel generator at 0.75 MW at 415 volts. The interconnection with the electricity supply authority grid was increased to allow for an export capacity of 5 MW. This paper discusses these problems and work carried out to achieve the degree of security required.