DC control battery system protection and coordination
Battery system failure jeopardizes a power system by eliminating the DC control power source for AC system circuit breakers and protective devices. The protection of control battery system components including the battery, battery charger and individual circuits is reviewed. Optimum battery system protective device coordination is discussed.<<ETX>>
Maintaining 'maintenance-free' batteries
The maintenance of valve-regulated sealed lead-acid stationary batteries is described, and comparisons are made with traditional vented lead-acid battery maintenance practices. The operation of the valve-regulated sealed lead-acid battery is also discussed. Two designs are currently available, both of which operate on the oxygen recombinant cycle. This cycle effectively eliminates evolution of free hydrogen gas under normal operating conditions. Maintenance considerations for valve-regulated sealed lead-acid cells are similar to those for flooded cells. It is noted that the terms 'sealed' and 'maintenance-free' commonly associated with these cells are misnomers, and it is urged that the use of such terms should be discontinued.<<ETX>>
Transient nonlinear thermal stability analysis of metro cable under pulse power
The load of metro cable system varies a lot from morning rush hours to the evening closure time. With many trains hopping in the rush hours, the long term and economical short term thermal stability become a big issue as a result of the large difference between thermal time constant and the electrical time constant of cable. Based on a 10kV three-core XLPE metro power cable model, the theoretical thermal capacity was calculated according IEC standard. Then, a Finite Element Method (FEM) was employed to analyze the transient electro-thermal phenomena, taking into account various types of power loss in cable system and the non-linear electrical conductivity of the conductor. Finally, the thermal distribution inside the cable was presented as a function of time, and the maximum thermal capacity was predicted in metro cable.