Smart Distribution Systems: Introducing the Single-Phase (micro)Phasor Measurement Unit

Smart Distribution Systems: Introducing the Single-Phase Phasor Measurement Unit

A single-phase Phasor Measurement Unit (PMU) is a device used for accurate measurement of synchronous phasor of voltages and currents at separated points across the power grid1. These units are widely installed at the transmission level.

The PMU is necessary for components control, fault detection and control, energy management in distribution network. The architecture of PMU setup has been fully designed and it integrates field measurements to deliver Global Positioning System (GPS) synchronized phasor data to the distribution networks.

This platform provides real-time data detection, power quality analysis and direction to future efforts to analyze data in cloud calculation, harmonic state estimation, etc.

There’s also a variant called Micro-phasor Measurement Units (μPMUs) which creates real-time synchrophasor data from the consumer voltage level, providing new insight into modern power systems. These units can be created more cheaply than current commercial PMUs.

Phasor Measurement Units (PMUs) and Micro-Phasor Measurement Units (μPMUs) are both devices used to estimate the magnitude and phase angle of an electrical phasor quantity (such as voltage or current) in the electricity grid using a common time source for synchronization. However, there are some key differences between them:

1. Resolution and Accuracy: μPMUs claim a capability of micro-second resolution and milli-degree accuracy, which is 100 times the resolution of traditional transmission-type PMU2. This makes μPMUs extremely useful for distribution systems and microgrids.

2. Usage: PMUs have been used for several years to record information on power system, especially in transmission system. Their ability to synchronize to Global Positioning System (GPS) time, enables them to make accurate measurements of angle differences2. However, due to their cost and the small angle differences they are rarely used in distribution system.

3. Cost: μPMUs can be created more cheaply than current commercial PMUs.

4. Sampling Rate: A typical commercial PMU can report measurements with very high temporal resolution, up to 120 measurements per second. On the other hand, a μPMU measures time-synchronized voltage and phase angle at high sample rates ~30/s for transmission and 120/s for distribution.

Implementing and installing μPMUs involves several steps and considerations:

Implementation:

1. A μPMU is a phasor measurement unit that measures time-synchronized voltage and phase angle at high sample rates.

2. It is a power quality recording instrument with a GPS receiver to enable highly accurate time-stamping for voltage and phase angle measurement.

3. Conventional PMUs in use for the transmission system have ±1° accuracy, and μPMU has 0.01°.

4. A multiphase power flow model and state estimation for distribution systems have been formulated, and solution methods have been presented.

5. It also addresses issues like modeling, implementation, observability, and performance.

Installation:

1. The installation of PMUs in the power grids is mainly focused on the transmission systems.

2. Due to the advancement in distribution system, i.e., for smart distribution system, a device is going to be installed which creates real-time synchrophasor data from the consumer voltage level, called μPMUs.

3. These units can be created more cheaply, an order of magnitude less, than current commercial PMUs.

4. For this reason, many more μPMUs could be deployed and provide a much higher resolution of the distribution grid.

5. Network buses connected with Distributed Generators (DGs) require direct measurement from μPMUs. Therefore, it is necessary to install μPMUs at DG buses2.

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