Smart Grid and EMC
The primary role of CISPR (International Special Committee on Radio Interference) is to provide standardization to control emissions from devices above 9 kHz. It has published various international standards that apply to Smart Grid system emission measurements and control. If the Smart Grid is to reach its full potential, emissions must be addressed effectively to avoid interference and protect the radio frequency spectrum. Smart Grid systems must be immune to sources of interference from a wide array of RF signals and RF disturbances.
CISPR has prepared a Guide to EMC in Smart Grid which gives further insight into issues that should be taken into consideration when designing and developing equipment for connection and inter-operation with the Smart Grid.
To perform as intended, the Smart Grid must be at least as reliable, secure, and fault-tolerant as the current power grid. Among the issues that must be addressed is its ability to withstand the electromagnetic (EM) environment without causing interference (disturbances) primarily to radio reception, but also to other digital/electronic devices.
Electromagnetic disturbances of various types, from a variety of sources, have been reported to cause performance degradation, outages, shutdowns, and even large scale system failure of the power grid. For this reason, EMC standards are crucial for Smart Grids.
Five broad categories of EMC events need to be considered:
- Mutual interaction (degradation of performance) of grid-connected electric and/or electronic devices (including communication equipment) due to conducted RF disturbances in LV AC mains installations, particularly in the range 2 kHz to 150 kHz;
- RF interference from various kinds of wireless transmitters and from unintentional radiators;
- Commonly occurring EMC immunity events like electrostatic discharges, fast transients, and power line disturbances;
- Coexistence of wireless transmitters so that wireless communications can be incorporated beneficially into the Smart Grid;
- High-level EMC disturbances from naturally occurring events such as lightning surges and geomagnetic storms or even from terrorist acts.
Items 1 to 3 above fall well within the scope of CISPR and TC 77, respectively. Item 4 is more probably within the scope of ITU-R and item 5 is considered by TC 77.
Since both the use of wireless communications and communications overpower/mains lines is a key part of the Smart Grid system, the use of CISPR standards is essential to minimise the risk to both radio services and to electronic products in close proximity to Smart Grid devices. Only CISPR has this international role of standardization in the field of EMC for RF emissions.
The standards that should be referenced in all Smart Grid planning documentation for item 2 include the following:
- CISPR 11 (Emission from industrial, scientific, and medical devices);
- CISPR 32 (Emissions from information technology and multimedia equipment as well as receivers). This is identified in the IEC Smart Grid standardization roadmap;
- CISPR 16 is also indirectly applicable. Its various parts include basic RF measurement methods and test instrumentation specifications including measurement uncertainty. They are also referenced in other CISPR product committee standards;
- CISPR 24 for immunity of ITE in Smart Grid control and appliances/devices. This standard references much of the TC 77 immunity test standards with additional information on the particular test set up and device operation;
- CISPR 12/25 for vehicles provides test methods for emission measurements which considers the impact of electric vehicles and distributed charging stations.
Hereafter an application of CISPR 11 that demonstrates the impact of a disruption of Smart Grid communications:
Power convertors can cause conducted disturbances on power cables. These disturbances can degrade the performance of other equipment connected to the same power cable. For example a smart meter which measures electricity consumption and is controlled by Smart Grid communications might not be able to operate properly.
Household appliances and lighting equipment can be switched from stand-by mode to active mode of operation by these kinds of conducted disturbances. Immunity standards help protect such devices, including the smart meter.
CISPR 11 test methods and restrictions can limit this undesired response.