"Demand Side Response System Frequency Control (DSR SFC) is a way of decreasing (or increasing) the demand of Temperature Controlled Devices, for example, fridges, freezers, heat pumps, immersion heaters, during periods of frequency deviations in the network.
During large disturbances in the network, for example caused by the loss of one or several generation units, a large shortage of power will occur. This will result in decrease of frequency and to prevent a total system collapse the automatic load shedding relays will disconnect a part of the load, causing a partial black-out of the system. This automatic activation of the Low Frequency Demand Disconnection (LFDD) is the last defence line to prevent a total black-out of the system.
DSR SFC may be used either only as a second last defence line before the Low Frequency Demand Disconnection (LFDD) will be activated automatically or with a wider setting range for providing automated frequency response to frequency fluctuations from nominal frequency. Depending on their point in the hysteresis cycle of heating or cooling of Temperature Controlled Devices, the device can be switched off within a specified range. The accumulated effect of switching a large number of Temperature Controlled Devices, will give a substantial reduction of load in the system.
In this way it should be able to prevent activating the LFDD and thus preventing large scale system black-outs, or with a wider setting provide necessary adjustments to the frequency/demand balance to restore the system to stable operation and restore system frequency back to nominal.
Due to the proportional nature of DSR SFC, it is expected this demand will respond before the normal wide spread arbitrary demand disconnection of users occurs. Dependant on the frequency range over which the demand will progressively respond, this will define whether some of this response will supplement other generation or DSR services. The setting of the frequency range will likely be determined at a synchronous system level, possibly consistent for all systems, and provides the flexibility to compliment other market services to achieve a sustainable operational capability to respond to greater future uncertainty arising from greater RES integration and pan European power transfers.
The DSR SFC makes use of the built in hysteresis of the Temperature Controlled Device. The hysteresis between the on and off temperature range of the device can be used to temporary delay the switch-on of the device or to temporary switch-off the device. The Temperature Controlled Devices on and off temperature range settings will not be exceeded by the DSR SFC when responding to frequency deviations from the nominal frequency. The DSR SFC will provide a response to deviations in Network frequency across a frequency range by corresponding changes to the Target Temperature in proportion of its maximum temperature range. The maximum change in Target Temperature will be at the widest when the system frequency is at the boundary of the system operating range defined by the Relevant TSO.
The open and high-level functional requirement on DSR-SFC as given in the code allows for different possible technical solutions to implement the requirement. As such, it is not expected that this could result in a monopoly for an existing patented design as the sole means to comply with this provision. Further technical specifications on the implementation are expected to be given in collaborating standardization activities.
This functional requirement (DSR-SFC) shall be applicable to apply to all future installations of electricity demands which are intended to deliver a controlled temperature. The identification of which devices will be fitted with DSR SFC by default will be specified following an implementing measure of the Ecodesign Directive. The DSR-SFC functionality is expected to be implemented by inclusion in relevant European Standards for electrical heating and cooling equipment and associated control systems. The systems shall be designed to have no noticeable or negligible effect on the primary use of the facility. The priority of the temperature controlled devicesshall at all times be to deliver the performance and comfort to a high quality level. This level shall be defined within the European Standards in accordance with the principle defined in this Network Code.
Even if measures to address the potential impact of DSR-SFC on third parties, e.g. portfolio implications for Balance Responsible Parties as defined in some countries, is out of the scope of this Network Code, it is assumed that this impact will be covered by evolutions of market mechanisms that are driven by various factors."
SOURCE: NETWORK CODE ON DEMAND CONNECTION - FREQUENTLY ASKED QUESTIONS 21 DECEMBER 2012