Basler Solutions for Power System Stabilizers

Adding a Power System Stabilizer
Replacing an existing Power System Stabilizer

Adding a Power System Stabilizer

The use of Power System Stabilizers has become increasingly important to provide improved stabilization of the system. Power system stabilizers are being used on generators from 35MW or a group of machines totalling 75MW in a plant that are connected to the transmission system.

North American Electric Reliability Council’s Eight Regions

NERC Policy involving Generator Testing

The North American Electric Reliability Council policies apply to anyone who sells power or is connected into the transmission grid and is one stepdown transformer removed from the system. NERC requires revalidating every five years.

Required testing information includes:

Reactive capability range of the machine.
Excitation system models with data validated by test.
Generator characteristics including synchronous, transient, subsynchronous, and reactance, that is verified by test data.
Excitation Limiters must be modeled and verified.

Generator Protection Relays must be tested and verified that they coordinate with the excitation limiters, such as the Volts/Hertz limiter versus Volts/Hertz protection.
The excitation system must be operated in automatic voltage regulation mode to help provide voltage support to the system in the event of a disturbance.
For excitation and generator systems operating in western United States, a power system stabilizer must be enabled and operating and a verified model provided

Oscillography internal to the excitation system provides a means to store files after performance testing has been accomplished and compare old performance to new test data. Oscillography triggers can be set to monitor MW, line current, generator voltage, vars, field voltage and field current in order to analyze the behavior of the system during an event and understand the cause and reaction of the generator/excitation system.

For more information on the types of tests that are required, operating modes of the excitation system, and how these tests help ensure increased transmission system reliability, see NERC Policies Affecting the Power Industry.

DECS-400 The Integrated Solution

The DECS-400 Digital Excitation Control System provides excitation control, flexible logic control, and optional power system stabilization for synchronous machines in an integrated package.

The optional Power System Stabilizer is an IEEE-type PSS2A, dual input, "integral of accelerating power" stabilizer that provides supplementary damping for low-frequency local mode, inter area, and inter unit power system oscillations.

Basler BESTCOMS software offers built in features to perform step tests and automatically log the data into COMTRADE or log files to speed testing and commissioning requirements.

The DECS-400 features an optional built-in power system stabilizer function

If you would prefer a discrete Power System Stabilizer or do not need to replace your AVR, the PSS-100 can be used in applications where the excitation works directly into either the brush or brushless rotating exciter, as well as static excitation systems working into the main field of the generator..

Basler's PSS-100 has been configured to work with a number of existing automatic voltage regulators

Basler’s PSS-100

AVR Manufacturer	AVR Name
Brush	Micro AVR, Prismic A30
Cutler Hammer	MGR
ABB	Unitrol F Digital, Unitrol M Analog
Westinghouse	WTA
Basler Electric	DECS-200, DECS-200N SSE, SSE-N, DECS-300

For more information on power system stabilizers and the issues involved in their usage, see Technical Papers:

Understanding Power System Stability - This paper discusses the types of power system instability and the effects of system impedance and excitation. A review of various types of Power System Stabilizers also is presented.
For more information on negative field forcing voltage regulators and power system stabilizers, see the technical paper "Suitability of Excitation Systems for PSS Applications" from the Power Engineering Society General Meeting, 2003
Power System Stabilizer Performance with Summing Point type Var/Power Factor Controllers - Power System Stabilizer performance does not have to deteriorate during a system transient when voltage support is needed using a summing point VAR/PF control and does not require operator intervention.

And, Application Notes:

EX-PSS1 - Solutions utilizing voltage regulator adjustment or a power system stabilizer for power plant stability and oscillation problems.
EX-PSS2 - The features of the PSS-100 Power System Stabilizer, a dual input device that measures both frequency (compensated frequency) and electrical power, reduce the time required to tune a power system stabilizer. The PSS-100 also has additional features to quickly calibrate the power system stabilizer to meet varying site conditions with multiple settings combinations.

Replacing existing Power System Stabilizer

Power system stabilizers were developed to aid in the damping of the power oscillations resulting from the high performance of continuously acting automatic voltage regulators by modulating the excitation supplied to the synchronous machine.

However, since originally developed in the 1960s, dramatic changes have been made in the power system stabilizer to make it more effective at frequency damping. See Application Note EX-D200N1 - DECS-200N Negative Field Forcing Capability Offers Tuning Advantages for Rotating Exciter Systems

Today’s power system stabilizer, represented by Basler’s DECS-400 with optional PSS function and PSS-100, are dual input device that measure both frequency (compensated frequency) and electrical power. They act as a replacement for several older power system stabilizer models.

Manufacturer	Product Name	Power System Stabilizing Method	Recommended Replacement for AVR and Power System Stabilizer	Recommended Replacement for Discrete Power System Stabilizer	Basler Power System Stabilizing Method
Westinghouse	F7	Frequency Based	Basler DECS-400 with optional PSS function	Basler PSS-100	Integral of Accelerating Power
GE	LA300	Frequency Based or Speed Based
GE	LA400 (µPSS)	Frequency Based
Power Technologies Inc.	PTI Stabilizer	Integral of Accelerating Power


For more information, contact Technical Support or your local sales representative.

	Return to Power Plant Operators page or view more solutions for - Excitation Systems - Bridge Replacement for Alterrex™ Rectifiers - Synchronous Motor Control and Protection - Rotating Diode Modules - Protective Relays - Automatic Synchronizers - Energy Storage Devices for Shunt Breaker Trip - Motor Operated Potentiometer Replacements