Reliability and Voltage Stability Test System

Leonardo Lima

Kestrel Power Engineering

1

Single Line Diagram

• 75 buses, 32 generators

• 3200 MW (generation)

• 230 kV (black) and 138 kV (blue)

2

System Characteristics

• Based on the 1979 IEEE Reliability Test System

• Added explicit representation of generator step-up transformers

• Moved loads to MV buses with step-down transformers with on-load tap changers (power flow and dynamics)

• This is a test system: system configuration and dispatch is not N-1 secure

Additional Features

• Slow voltage collapse phenomena

– Transformer automatic on-load tap changers

– Generator over-excitation limiter

– Load characteristics recovering from voltage-dependent models (usual representation for dynamics) to constant power (usual representation for power flow)

Additional Features

• Fast voltage collapse phenomena

– Fraction of total load represented by induction motor model

– Application of SVC

Critical Contingency

• 138 kV underground cable (106 to 110)

– 250 MVAr of total charging

– 75 MVAr reactor at each terminal

– Line-connected shunt reactors

R X

2

B

2

B

cable represented by -model

breakerBus

106

Bus

110

Line-connected

reactor

PV and QV Curves

0 MVAr

PV and QV Curves

• Base case (N-0) in red

• Two non-critical contingencies

• No power flow solution for critical contingencies

Slow Voltage Collapse

• Critical outage

– Trip cable (and line-connected reactors)

– No fault

• Simulations

– With automatic OLTC, without load recovery

– With automatic OLTC, with load recovery

– With SVC, without load recovery

– With SVC, with load recovery

Slow Voltage Collapse

Slow Voltage Collapse

Slow Voltage Collapse

Initial load MW

Slow Voltage Collapse

Initial load MVAr

Fast Voltage Collapse

• Modeling a fraction of the total load as induction motors

• Three-phase fault at bus 106

• Total clearing time = 6 cycles

• Trip cable 106-110

Fast Voltage Collapse

Fast Voltage Collapse

Fast Voltage Collapse

Fast Voltage Collapse

System Data

• PSS/E format

• DSA Tools format

Specific Models

• Generators

– GENSAL (5th order model, salient pole machines)

– GENROU (6th order model, round rotor machines)

• Excitation Systems

– IEEET1 (IEEE Std. 421.5 DC1A)

– EXAC1 (IEEE Std. 421.5 AC1A)

– SCRX (simplified IEEE Std. 421.5 ST1A)

Specific Models

• Power System Stabilizers

– IEEE Std. 421.5 PSS2B

• Over-Excitation Limiter

– MAXEX2 (summation point OEL)

• Turbine/Speed Governors

– IEEEG1 (steam turbines)

– HYGOV (hydro turbines)

Specific Models

• Loads

– Constant current (active power) and constant impedance (reactive power)

– Load recovery to constant power

PMLTmax

PMLTmin

KP

s

1

Pinitial

PMLT

Pinitial

–

+

Pinitial

y=(u)

y

uVinitial

V

Pf(V)

voltage dependent

load model

Perr

Pload

load reset model

(back to constant MW)

Specific Models

• Loads

– Complex load (with induction motor participation)

Specific Models

• SVC