NASPI Voltage Stability Workshop Houston, TX October 2014 Voltage Stability Test Case 2 Objective: Demonstrate voltage stability analytics and visualization for a small test system, incorporating security assessment for N-­‐1 contingencies. Intended Users: Real-­‐time System Operators, System Operations Engineers Problem Statement: The concern is voltage insecurity for high transfer levels into the load area. Generation retirements in the load area result in higher required imports, and therefore increase the risk of voltage insecurity and collapse. Dispatchers need awareness of real and reactive power margins for pre-­‐ and post-­‐contingency operating conditions to manage imports reliably. Import is shown below. Determine the following times and provide real-­‐time indicators for dispatcher situational awareness: 1. Time at which system moves into insecure operating region. Insecurity is determined using N-­‐1 contingency analysis as described below. 2. Time at which system loses stability. 3. Real and reactive power stability margins for transfer into Zone 10. (*NOTE: Report P = total load in Zone 10 at a minimum for PV curve analysis.) 4. Visual alarming of system conditions using software capabilities 5. Any other useful information dispatcher would like to have for this scenario. System Assessment Assumptions: •
Only N-­‐1 contingencies considered for security assessment. No N-­‐2 or N-­‐1-­‐1 contingencies should be included. Credible N-­‐1 contingencies include: 1) any single transmission circuit, including transmission lines and two-­‐winding transformers, 2) any fixed or dynamic shunt VAR device, and 3) any single generating unit. (NOTE: Detailed list of credible contingencies is included; do not include additional contingencies.) •
Voltage criteria for all buses pre-­‐ and post-­‐contingency: o
Voltage deviation (ΔV) > ±0.05 pu o
Voltage violation: V < 0.95 pu, V > 1.05 pu •
Thermal violations are NOT considered for this assessment. •
Capacitors are allowed to switch dynamically in steady-­‐state conditions. •
Capacitors are locked (not allowed to switch) for contingency conditions. •
STATCOM is allowed to move for both steady-­‐state and contingency conditions. NASPI Voltage Stability Workshop Houston, TX October 2014 •
Under-­‐Load Tap Changers (ULTCs) is locked for all conditions. Not considered for simplicity. •
Load scaling for future projections should use: 1) scaling proportional to starting conditions (except for fixed loads), and 2) 50/50 pickup between the two equivalences. •
Loads are modeled as constant MVA for real and reactive components. Measurement Assumptions: The following assumptions are used for this scenario: 1. The dispatcher is using a hybrid PMU-­‐ and SCADA-­‐based measurement system. This system retrieves time-­‐synchronized PMU data and unsynchronized SCADA in its applications at a 2-­‐
second down-­‐sampled rate. The data provided is the only viable measurement set available. 2. Measurements are located at the locations provided in the attached spreadsheet(s). 3. The root (starting point) system model extracted from the state estimator is provided.