In a control center-based scheme, the substation computer is used as a gateway to transmitting field IED data back to the outage management system at the control center and control commands from the control center to the field IEDs. The first uses industry-accepted protocols such as IEC61850, DNP3, and Modbus, to obtain the necessary data from each of the feeder IEDs, and then analyzes these data to detect if a fault has occurred in the system. In the event of a fault, the gateway sends this information upstream to the DMS. After data analysis, DMS determines the location of the fault and subsequently runs the RSA, generating the proper isolation and restoration switching actions that should be taken. The DMS then sends the switching control commands to the gateway either automatically or after an operator authorization action, whichever is preset in the control center DMS application.
With the integrated control center-based restoration scheme, the gateway detects the outage based on the IED-sensed network events and informs the DMS automatically. When the DMS receives this notice, it will run the RSA with respect to the outage area and generate power restoration schemes. The RSA is based on the detailed network model and unbalanced load flow analysis of this model to insure that the post-restoration network does not have current and voltage violations. The RSA combines a network topology tree-tracing and genetic algorithm, thereby enabling it to support both lightly and heavily loaded network conditions. If the loading of the network is light, then single-path restoration is sufficient. If it is heavily loaded, either multi-path restoration or a multi-layer RSA must be used. The concept of the multi-layer RSA is illustrated in Figure 8, where green squares represent tie switches or fault clearance/isolation switches. The tie switches that bound the unserved load area are called the first layer of tie switches for restoration.
Subsequent layers are named sequentially (e. g., second layer, third layer). Under heavy load conditions, closing only the first layer restoration switches may not be sufficient for meeting the power requirements of the unserved loads. Thus, load transfers from the zone between the first and second layers to that between the second and the third layers may be necessary.
Fig. 8 The multi-layer RSA concept