Introduction to System Protection Scheme (SPS)
ERLDC, POSOCO
Outline
• Introduction
• System Protection Schemes
• What
• Why
• Where
• General structure of an SPS
• Classification of SPS
• SPS Design and Operation
• Analysis of Operation
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System Protection Scheme
• A System Protection Scheme (SPS) or Remedial Action Scheme (RAS) is designed to detect
abnormal system conditions and take predetermined, corrective action (other than the
isolation of faulted elements) to preserve system integrity and provide acceptable system
performance.
• System Protection Scheme is generally for
• Rare contingencies
• Operating condition outside capability of conventional protection and manual action.
• Fast and Immediate action.
• Focus on power system supply capability rather than on a specific equipment
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System Protection Schemes Characteristics
• Normally sleeping systems
• Operate infrequently
• Control actions taken is predetermined
• Can be armed or disarmed depending upon system conditions
• Can comprise a large number of coordinated actions, in a cascaded
manner
• Under frequency controlled load shedding in a number of steps at different frequency
levels and/or with different time delays
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Why we use SPS on Power Network
The task of the power system planner is to find a technical and
economical trade-off between investments, operation cost and
customer service quality. SPS play a significant part in this trade-
off and are mainly used on a power system to:
1. Improve power system operation.
2. Operate power systems closer to their limits.
3. Increase power transfer limits while maintaining the same level of
system security.
4. In a temporary installation to compensate for delays in the construction
program
5. Increase power system security particularly towards extreme
contingencies leading to system collapse.
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Power System Phenomena with Possible SPS Solutions
• Problems on the power system include:
1. Short circuits
2. Abnormal conditions
• Transient angle instability;
• Small signal angle instability;
• Frequency instability;
• Voltage instability; and
• Cascaded tripping.
3. Equipment failures
The use of an SPS is most frequently justified for loss of network integrity
characterized by one/more of the above phenomena.
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General structure of an SPS.
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Classification of an SPS according to its input variables
1. Response-based :
1. Based on measured electric variables (such as voltage, frequency, etc.) and
2. Initiate their protective actions when the contingency has caused the measured value to hit the
trigger level.
3. For this class of SPS, the effect of unintended operation is generally limited because its actions are
restricted and localized
4. This type of SPS is simple and secure
5. The objective is to correct the deterioration of these variables by an action, which is generally
local.
2. Event-based SPS
1. operation only upon the recognition of a particular combination of events
2. based on the direct detection of the event (e.g. the loss of several lines in a station)
3. Pre-planned target actions could be local or remote.
4. This type of SPS is generally used for events whose severity largely exceeds the robustness of the
system
5. They are generally high-speed because their actions must be carried out before system behaviour
becomes overly degraded and system instability cannot be prevented.
6. The reliability of event-based SPS is often a concern, but good design and adequate levels of
redundancy can ensure high reliability.
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Classification of an SPS according to its action
▪ SPS related to Generation rejection
▪ SPS related to Load rejection
▪ SPS related to Generation/Load rejection
▪ SPS related to HVDC controls
▪ SPS related to others
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Classification of SPS according to impact and detection system
• Classification of an SPS according to its impact on the power system
Local area
Wide Area
• Classification of an SPS according to its detection system
Local area detection :
• Detection is considered local when all the information required by the decision-making
process is available at the same location where the action is performed.
• Generally, “local SPS” are considered the most dependable type of SPS because they do
not rely on telecommunication facilities
Wide Area detection :
• The action is initiated by information acquired at one or more key buses located
elsewhere in the power system.
• Generally used to counter complex and large phenomena that may jeopardize the
integrity of the whole power system.
• higher level of complexity than the local SPS and strongly depend on
telecommunication facilities.
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SPS Design and Operation Procedure
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Analysis of SPS scheme
• Why To Analyze ?
• Whether SPS operation was Desired.
• Whether SPS operation as per Design.
• Whether SPS operation gave the required relief.
• Whether SPS operation was Satisfactory or not.
• Whether SPS operation got reset.
• Whether SPS operation need review.
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How to Analyze SPS operation ?
• Analysis of SPS Requires Same Data as any Event .
• Get FIR from Control Room about the Event
• Start Checking pre SPS condition of the Grid.
• Sites/Substation to Inform Which SPS operated
• Load/Generation to Inform receipt of Signal and their Action (Response
Duration curve and data to be submitted in high Resolution format )
• Relevant DR/EL to be collected from Station from Where SPS got triggered.
• Start Creating Sequence of Event
• Check Whether SPS criteria Satisfied or not
• Use Simulation to Fine tune your analysis.
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Performance Criteria
• Any SPS operation can be classified into four categories which
are : n 1
• Successful Operation Effectiveness Index (EI) =
n1 + n2 + n3
• Failure Operation
n1
• Unsuccessful Operation Dependability Index (DI) =
n1 + n2
• Unnecessary Operation. n4
Unnecessary Operation Rate (UOR) =
ny
n1- Number of Successful Operations;
n2- Number of Failures;
n3- Number of Unsuccessful Operations;
n4- Number of Unnecessary Operations;
ny- Number of Scheme - Years of Operation;
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Conclusion
Validate Your
Analysis of Keep a Scheme, Test on Keep
Each SPS Track of SPS
regular Interval Performance
and Review with Parameters
operation Is Handy
Log Network or Op
Essential
Condition Change
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Thank You ☺
Any questions?
You can find me at:
saurav.sahay@posoco.in
