On possibilities of smart meters switching at low voltage level for emergency grid management

Licentiatavhandling, 2015

Smart Meter (SM) is an advanced remotely readable energy meter with two-way communication capability which measures the electrical energy in real-time or near-real-time and securely sends data to Distribution System Operator (DSO). A smart metering system is an application of SMs on a larger scale, i.e. the application of a general principle on a system rather than on individual appliance. The European Commission (EC) has included ten common minimum functional requirements for electricity smart metering systems. One functionality requirement among these functional requirements is that the SM should allow remote ON/OFF switch to control the supply. Some DSOs who have installed remote ON/OFF switch are currently applying this technique for customers typically one by one when customers are changing addresses, or when contracts are terminated, or have defaulted on their payments. The switching functionalities of the SMs could be used for multiple customers, thereby opening up new possibilities for emergency electrical grid management by excluding prioritized customers. There is an interest to investigate if the multiple SMs switching might have some impacts on the Power Quality (PQ) of the electrical grid and also the challenges in implementing this technique on the existing smart metering system during emergency situation. In this thesis work, three field tests have been performed on multiple SMs switching focusing on the impact of the SMs switching on the PQ of the grid. A risk analysis was carried out before conducting the field tests. The PQ measurements were done by Power Quality Meters (PQMs) during the multiple SMs switching. Voltage variations and PQ events were recorded in the PQMs. Waveform data of the PQ events were recorded at 12.8 kHz sampling frequency. The test results are then evaluated based on PQ standards. Moreover, performance of the existing smart metering system was investigated during the multiple SMs switching to identify the challenges and possibilities of using multiple SMs switching. The analysis of the test results show that there were no other PQ events or voltage variations except some transient events which were recorded at some customer level during the reconnection of the SMs. However, the duration of the transient events was only fractions of a millisecond and deviation of the voltage transients were below +/-50% except for few transient events which have deviations of more than +/- 50% but less than +/-60%. This type of transient events may not be able to create damage to sensitive customers’ loads. The multiple SMs switching may not have impact on the PQ if the number of customers is low. However, SMs switching for large number of customers might have impact on the PQ which needs to be investigated. Moreover, the performance of the existing smart metering system during multiple SMs switching shows some limitations on implementing the switching technique for large scale of customers. The identified limitations are e.g., long time requirement for SMs switching and errors in the real-time status update report during SMs switching. Furthermore, the findings show that more research is needed to identify required functions for future smart metering system to implement multiple SMs switching during emergency grid management.