<story><title>Ercot nearly at capacity for Texas power grid</title><url>http://www.ercot.com/content/cdr/html/real_time_system_conditions.html</url></story><parent_chain><item><author>cameronh90</author><text>Preface: I know very little about power grids, but had a couple thoughts.&lt;p&gt;In the UK, there is a system of load shedding that is tied to the grid frequency. My understanding is that some industrial users agree terms where they get cheaper rates but if the demand outstrips supply, they are first to be cut. This load shedding is implemented by components that monitor the grid frequency, and if it drops below a fixed value, it disconnects. It seemed a nice system to me as in theory it operates just based on the principles of an AC power supply.&lt;p&gt;Secondly, the UK has its own grid but is linked up to the EU grid with asynchronous HVDC connectors. We get a lot of our energy though those. Is this inefficient?</text></item><item><author>don-code</author><text>Some time ago, I worked for a defunct energy company that provided demand-side relief in exactly this scenario - when total system load outstrips total system capacity, we&amp;#x27;d begin taking actions on behalf of end users, not the utility. Lights would turn off, generators would spin up, fridge temperatures would be raised.&lt;p&gt;ERCOT (Texas) is an interesting case in that it can&amp;#x27;t import power from other states as easily - it has its &amp;quot;own grid&amp;quot; at 60Hz, but not necessarily in phase with either of the other two major grids in the country (there&amp;#x27;s eastern US, western US, and &amp;quot;most of Texas&amp;quot;). So to import power, it first has to convert grid-scale amounts of energy from AC to DC, then back to AC, which incurs a pretty significant loss.</text></item></parent_chain><comment><author>eigenvector</author><text>The technical term for what you&amp;#x27;re describing is under-frequency load shedding (UFLS) and it is part of most modern power systems around the world, including all of the North American grids. It is an important safeguard against system collapse, however, the goal of system operators is to avoid reaching this stage. In fact, resolving contingency events without interruption of &amp;quot;firm load&amp;quot; (that is, loads that have not previously agreed to be interrupted) is an important performance metric for any grid operator.&lt;p&gt;UFLS is mostly intended to buffer transient loss of power supply (for instance, tripping of several large generators). If the grid operator knows they are facing an inadequacy of generation supply and all resources have already been called in, they will start to shed load under manual operator action to avoid UFLS activation. Before doing this they will declare an emergency which, generally speaking, requires all generators to make best efforts to supply as much energy as they can to the system.&lt;p&gt;Think of it like automated emergency braking on a car vs driver braking. AEB is great, but if you can already see that you&amp;#x27;re gonna hit something, just hit the brakes right now instead of waiting for AEB. By the time UFLS kicks in, you&amp;#x27;re already in dire straits and have only moments before reaching an unrecoverable state.</text></comment>
<story><title>Ercot nearly at capacity for Texas power grid</title><url>http://www.ercot.com/content/cdr/html/real_time_system_conditions.html</url></story><parent_chain><item><author>cameronh90</author><text>Preface: I know very little about power grids, but had a couple thoughts.&lt;p&gt;In the UK, there is a system of load shedding that is tied to the grid frequency. My understanding is that some industrial users agree terms where they get cheaper rates but if the demand outstrips supply, they are first to be cut. This load shedding is implemented by components that monitor the grid frequency, and if it drops below a fixed value, it disconnects. It seemed a nice system to me as in theory it operates just based on the principles of an AC power supply.&lt;p&gt;Secondly, the UK has its own grid but is linked up to the EU grid with asynchronous HVDC connectors. We get a lot of our energy though those. Is this inefficient?</text></item><item><author>don-code</author><text>Some time ago, I worked for a defunct energy company that provided demand-side relief in exactly this scenario - when total system load outstrips total system capacity, we&amp;#x27;d begin taking actions on behalf of end users, not the utility. Lights would turn off, generators would spin up, fridge temperatures would be raised.&lt;p&gt;ERCOT (Texas) is an interesting case in that it can&amp;#x27;t import power from other states as easily - it has its &amp;quot;own grid&amp;quot; at 60Hz, but not necessarily in phase with either of the other two major grids in the country (there&amp;#x27;s eastern US, western US, and &amp;quot;most of Texas&amp;quot;). So to import power, it first has to convert grid-scale amounts of energy from AC to DC, then back to AC, which incurs a pretty significant loss.</text></item></parent_chain><comment><author>bombcar</author><text>Load shedding exists in the USA - however industrial customers who can shut off probably already have given the rise in spot prices.&lt;p&gt;I know the Datacenter we were in years ago would be asked to go to generators during CA power crisis.</text></comment>