Siemens Phasor measurement unit (PMU)

Siemens Phasor measurement units (PMUs) and its measured synchrophasors make a valuable contribution to the dynamic monitoring of transient processes in energy supply systems. These data are the basis for the Wide Area Monitoring system SIGUARD PDP. This fast monitoring system detects the events and trends in grids with fluctuating load flows or highly loaded lines which conventional systems cannot detect at all or can detect too late.

Siemens Phasor measurement units : Features

Phasor measurement units (PMUs) measure current and voltage by amplitude and phase at selected stations of the transmission system. The high-precision time synchronization (via GPS) allows comparing measured values (synchrophasors) from different substations far apart and drawing conclusions as to the system state and dynamic events such as power swing conditions.

All SIPROTEC 5 devices can be used as a phasor measurement unit. When selecting the option Phasor Measurement Unit, the devices determine current and voltage phasors, provide them with highly accurate time stamps and transmit them for analysis together with other measured values (frequency, speed of frequency change) using the IEEE C37.118 communication protocol, which are typically sent to the control center.

SIGUARD PDP (Phasor Data Processor) is a system for Wide Area Monitoring and Grid Monitoring that, as its measured variables, uses synchrophasors from phasor measurement units serving as sensors. It helps with quick recognition of the current network situation and indicates both power swings and transient phenomena, transparently as well as instantly. Replication of the respective network topology is not required. The tool supports control center personnel in assessing critical grid situations and contributes to the taking of suitable action. As all measured results are stored, power system disturbances can be promptly analyzed.

Phasor measurement (PMU) with SIPROTEC 5

PMU – overview of function
A phasor measurement unit (PMU) measures the phasor values of current and voltage. These values get a high precision time stamp and together with the values of power frequency, power frequency change rate and optional binary data that are also time stamped are transmitted to a central analysis station. The standardized transmission protocol IEEEC 37.118 is used to do this.

Structure of the function group

The PMU function group is activated by selecting the protocol IEEE C37.118PMU on an Ethernet module (electrical or optical). The PMU obtains the measured values from the measuring points and the precise time from time synchronization. The time-stamped synchrophasors for current and voltage are formed from this and transferred together with additional values via the communication module to a server (PDC, Phasor Data Concentrator).

PMU – function description
The synchrophasors, sent from the PMU in a continuous data stream to a PDC, are provided with time stamps and thus are comparable with the measured values of other PMUs. The power frequency, the power frequency change rate and optional binary information are also transmitted as time-stamped measured values. Therefore, you receive an overview of the transient processes in a distributed energy transfer system, for example network fluctuations and compensating processes.

 

Synchrophasors of the PMU	Measured values from the measuring points
Continuous updating (measured value of current) with, for example, 10 values per second (reporting rate)	Slow updating (typically every 5 seconds)
Every measured value has a time stamp	No time stamp for the measured values
Phasor values of current and voltage (amplitude and phase angle)	RMS values without phase angle

 

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