Monitor and determine transient stability of the system
Transient Stability Assessment by PJM
In addition to the special operating procedures addressing stability limit issues in Manual-03B, PJM utilizes a real-time Transient Stability Assessment (TSA) tool. TSA can monitor and determine transient stability of the system subject to a select set of EMS contingencies for balanced and unbalanced faults. PJM models a select set of three-phase faults with normal clearing and single-phase faults with delayed clearing. The contingencies or faults are in alignment with most planning events as defined in TPL-001-4 categories P1 through P4.
TSA will also monitor and control for dynamic stability using a 3% damping criteria for the RTO. TSA will display contingencies and impacted generators not meeting 3% damping criteria for units 10 MVA or above, as simulated between 10 and 15 seconds. PJM will perform additional simulations to validate damping results not meeting criteria in Real-time.
TSA is also utilized to assess transient voltage response. The transient voltage criteria is recovery to a minimum of 0.7 p.u after 2.5 seconds (0.7 p.u. of nominal voltage). Refer to Manual-37: Reliability Coordination for additional information. The typical controlling actions for transient voltage exceedance are switching of static reactive devices, such as capacitor and reactors, to maintain a strong pre-contingency voltage profile and reserving dynamic reactive output from SVCs, STATCOMs, and generators, for post-contingency voltage support.
TSA computes stability limits by using real time network models. It interfaces with the EMS and uses the State Estimation solution. Other input data includes the dynamic model for over 3000 generators and fault clearing times for specific equipment. For equipment without a specific fault clearing time, TSA will use zonal default clearing times. TSA also calculates and provides recommended stability control measures to prevent generator instability. Typically, the control measure is expressed in terms of generator-specific MW adjustment. In some cases, a Mvar adjustment may resolve a stability issue.
TSA is used to monitor and control the generators with known stability concerns as defined in PJM Manual-03B. Since TSA uses real-time system conditions to assess stability, the limits tend to be less conservative or less restrictive than the manual operational procedures. The operational procedure limits are usually determined using conservative assumptions in order to cover a wider range of operating conditions. For scheduled transmission outages, TSA studies are used to determine the stability limits. For forced outages, the Manual-03B operational procedure limits are used until a real-time TSA run is completed. PJM will also use the Manual-03B operational procedure stability limits in certain cases, such as when TSA is down.