ABSTRACT
Protective relay is one of the most important parts in the electric power system ensuring the credibility of the transmitting network. Protective relay instruments are being widely used in the transformer substations and switches,examining the operating status, registering thepower failure and control the movements of the switches. Collier underground service condition is very particularity,if there is a lack of indispensability amd reliable protector,there will be a fire or gas explosion caused by long-term overload,creepage and short circuit. So ,collier downhole security power suplly is the homologous step for the particularity working condition.
The pivot of this rated is the microcomputer current protection of the low-voltage protection’ current protection.The microcomputer shiled is composed by two parts which are the hardware and the software.The hardware dvice of the microcomputer current protection systerm contins three macromoduls.They are analog quantity input systerm,CPU host systerm and on-off input/output systerm.Voltage signal and electric signal which are taken from the colliery power supply systerm are tansformed to digital signals and loaded to the CPU systerm to be read by the analog quantity input systerm. In order to complete the mission of the shield,different kinds of the information is analysesed and processed the CPU systerm.The software part is realized primarily by the monolithic computer and its rate .
KEYWORDS: low-voltage switch; elctric current quick break shield; blast protection; microcomputer protection; hardware design.