Cycle Time and Frequency Tracking

Praveen.A.N, Pravee n.A.N, Sr. Sr. Engineer, PG – GAS – 05/ 05/05/ 05/201 2016 6

Cycle Time Time and Frequen Frequency cy Tracking Tracking Introduction

Objective

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Recognize and Understand §

Task time groups

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Cycle – Time of a function block

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Order of a function block

Understand SMAI configuration §

Parameters of SMAI configuration

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Frequency Tracking

Case study §

Consequence of wrong execution order and cycle time

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Consequence of wrong frequency tracking setting

Cycle Time and Execution Order  Task Time Group  Application Manual REG670

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Execution of functions in ACT runs according to a fixed sequencey with different cycle time

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For each cycle time, function block has a serial execition number.

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Classified as fast, medium and slow

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Time value different between 650 and 670 series.

Cycle Time and Execution Order  Logical Function Blocks (FB) in IEDs

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Cycle Time and Execution Order 

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Execution of different function blocks within the same cycle is determined by the serial execution number.

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 Additional time delays might be needed when connecting FB with fast cycle time to FB with slow cycle time

Cycle Time and Execution Order 

Technical Reference Manual – REG670

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SMAI Pre-processor Function Block Technical Reference Manual – REG670

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Used to process the analog signals

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 All information of the analog signal like the RMS value, phase angle, frequency, harmonic content, sequence component etc (about 244 values in total)

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Information from the SMAI is then used in different function block in ACT.

SMAI Task Time Groups

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Frequency Tracking Parameter and Principle

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 Adaptive frequency tracking is needed in order to ensure proper operation of DFT based functions during varying frequency conditions.

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Frequency tracking is set using the DFTRefExtOut and DFTReference settings.

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These parameters provide DFT reference for DFT calculations.

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InternalDFTRef uses fixed DFT reference based on set system frequency.

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ExternalDFTRef will use reference based on input DFTSPFC.

Frequency Tracking Parameter and Principle §

Selected reference instance of SMAI must be voltage type.

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Positive sequence tracking feature.

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voltage is used for the frequency

IntBlockLevel is set in % of Ubase /  √ 3. If the positive sequence voltage IntBlockLevel, the feature is blocked.

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lower

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 Adaptive frequency tracking is applicable for IEDs in generating stations during start – up and shut – down.

Frequency Tracking Examples of DFT Based Function

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Generator Differential Protection

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Transformer Differential protection

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Over – Current and Earth Fault Protection

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Residual Over – Voltage and Over and under Voltage Protection

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Over – Excitation Protection

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Measurement Function

Frequency Tracking SMAI

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Frequency Tracking SMAI

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Frequency Tracking SMAI

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