DCDB Health Check
DC system is one of the most important systems in substation and must be maintained in healthy conditions at all the times. DC supply is required to operate protective equipment in substation during emergencies. By keeping the DCDB system healthy, severe damage to substation equipment and to human life can be avoided in the event of AC power failure.
Battery Bank is the most important part of the DC system. Always the batteries must be maintained in good condition so that they can supply the designated output constantly. A good battery charger is needed to keep the batteries in “charged” condition. If the RMS ripple current is not in acceptable limit, the charger can damage the battery instead of keeping them charged. The entire control system of DC source along with connecting cables and control equipment forms floating source, i.e., at no point it is electrically connected to earth.
But due to a cable damage or insulation failure the system gets electrically connected to earth and no more remains a floating system. A further fault happening to this earthed system in the opposite polarity results in overloading of DC source, cable burning and disruption of power to the control equipment.
If an earth fault exists in the system, in most cases the substation engineers is aware of that, but it is left without attending due to difficulty in tracing the fault among the bunch of cables running from control panel to various equipment in substation and over that the non-availability of drawings also makes the job much more difficult which can often lead to severe damage to substation equipment and to human life in the event of DC power failure.