Power Quality
The NES System gives utilities a wealth of information on power quality that can be used to manage assets like transformers, distribute loads evenly across phases, and minimize outages by finding trouble spots in advance. NES residential meters provide a rich suite of power-quality measurements that help utilities monitor power quality at no extra cost.
Two emerging trends in power quality measurement are very important to utilities:
- Consumers’ rising energy requirements are causing the load on each phase to rise. Very often the load increase is not evenly distributed across phases. This results in phase imbalances that cause uneven voltages. In severe cases, utilities may decide to reconfigure the distribution network or use larger distribution transformers to address the problem.
- An accelerated increase in the use of non-sinusoidal loads (such as switch mode power supplies used in televisions, computers, energy-efficient lamps, and electronic speed controls) is increasing harmonic currents and causing transformer heating.
In both cases, utilities end up with increased maintenance and inventory costs. In the case of over-voltage, an increase in the cost of goods to consumers results in a decreased lifespan of electronic components.
Total Harmonic Distortion
Harmonic distortion is the change in the waveform of the supply voltage from the ideal sinusoidal waveform. It’s caused by the interaction of distorting customer loads with the impedance of the supply network. Its major adverse effects are the heating of transformers, capacitors, induction motors, and the overloading of neutral conductors that are not rated to carry large currents. Therefore, monitoring Total Harmonic Distortion (THD) is very important to utilities.
NES residential meters can measure voltage THD, current THD, and VA THD to the 10th harmonic and, more importantly, log THD events when THD exceeds a specified threshold. This lets utilities identify trouble spots to chart a plan of action.
Sags and Swells
NES smart meters allow both magnitude and duration thresholds of voltage sags and swells to be defined. After that, meters log occurrences of sags and swells, which can indicate abnormal load conditions or phase imbalances. Selected events are recorded in the meter’s event log with a time stamp. Each NES meter logs brown outs, long outages, and counts the number of short outages.
Neighborhood Meter Network
A CT meter installed at the low-voltage distribution transformer can work in harmony with the residential meters. On its own, the CT meter measures and records neighborhood meter network data as an aggregate, including energy supplied, power factor, voltage, and current on a per-phase basis to help detect and diagnose abnormal conditions.
Key Attributes of the NES System that Support Power Quality Solutions
- Embedded grid intelligence measures power quality metrics
- Measures voltage, current, and VA harmonic distortion
- Sag and swell logging with configurable threshold and duration
- Neighborhood meter network data analysis between measurements from a CT meter and residential meters
- Power quality-affiliated logging and alarms/alerts built-in and configurable through software