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# Frequency Measure Element

**Properties**: Determines the fundamental frequency of a bus voltage symbol

**Features**: Can be used with any bus in the network using a basic frequency

**General Parameters**

**Basic Frequency:** Normal fundamental frequency of the network used as the main frequency of the bandpass filter (Hz)

**Bandpass Filter Parameters****Bandwidth:** Width of bandpass filter (Hz)

**List of Available Signals**

At acquisition, the following signals are made available by the sensors:

Freq_label | Fundamental frequency (Hz) |

Periode_label | Fundamental period (s) |

Vaf label | Filtered bus voltage for phase A (V) |

Vbf label | Filtered bus voltage for phase B (V) |

Vcf_label | Filtered bus voltage for phase C (V) |

**Frequency Measure Control Panel**

The following figure shows an example of the parameters used for a 60 Hertz test.

**Frequency Measure Model**

The block diagram of the frequency measure element is shown in the next figure. The bus voltages are read and filtered, then the time between two zero crossings of these voltages is calculated.

When a voltage rise is detected, a counter is reset and increments until the next rise. The mean of three calculated periods is then determined and inverted to obtain the frequency. The variables

used in the block diagram are defined as follows:

Va, Vb, Vc | Bus voltages |

Vaf, Vbf, Vcf | Filtered voltages |

FB | Basic frequency |

LB | Filter bandwidth |

Num | Parameters for the numerator polynomial of the filter |

Den | Parameters for the denominator polynomial of the filter |

Ra, Rb, Rc | Signals to reset the counters used to calculate the period |

Pa, Pb, Pc | Calculated periods for three phases |

f | Fundamental frequency |

Block Diagram of Frequency Measure 1

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