Frequency Management
Frequency Rate of Change
1 Frequency Control
Technical Background Technical Assessments Technical Solutions Commercial Assessments Commercial Solutions Timelines
2 Technical Background
Frequency Automatic frequency response ramps up over 2 to 10 seconds
50Hz
RoCoF based If the rate of change is protection operates high enough, ~500ms distributed generators shut down causing a If the volume of further fall in frequency distributed generation at risk is high enough, there is a risk that LFDD occurs Containment limit (49.2Hz)
Low Frequency Demand Disconnection Stage 1 (48.8Hz)
Instantaneous Infeed Loss Automatic Frequency Response Time 3 (Primary) fully delivered Technical Background
Stored Energy in Transmission Contracted Synchronised Generation for the 1B Cardinal Point (overnight minimum demand period)
350,000
300,000
250,000
200,000 MWseconds
150,000
100,000 01-Jan-10 04-Jul-10 04-Jan-11 07-Jul-11 07-Jan-12 09-Jul-12 09-Jan-13
4 Technical Assessment
Frequency The difference indicates the contribution ‘demand’ makes to 50Hz system inertia
Measured Frequency
Simulated Frequency
Time
5 Technical Assessment
Generator Step Up Export to the Transformer System
Power output and inertia is lost when the circuit breaker Power System opens Frequency
Time Time
Output/Frequency for an “electrical” trip Output/Frequency for a “non-electrical” trip 6 Technical Assessment
50.15 500ms 50.2 50.1 28th September 2012
50.05 50
50 49.8
49.95 49.6 49.9 01:48:30 01:48:38 01:48:46
49.85 Frequency (Hz) 49.8
49.75
49.7
49.65 01:48:32 01:48:34 01:48:36 01:48:38 Time 7 Scotland NW SE Technical Solutions
Options for Managing the Risk Limiting the largest loss limits the rate of change Increasing inertia by synchronising additional plant reduces the rate of change Limiting the Rate of Change using automatic action (not currently feasible) Changing or Removing RoCoF based protection
8 Commercial Assessment
The maximum rate of change risk occurs when demand is low and there is a large instantaneous infeed or offtake risk to manage The maximum rate of change is rising because Synchronous generation is being displaced by non- synchronous plant – interconnectors and wind There will be larger infeed losses in the future There are trends within consumer demand which are reducing system inertia
9 Commercial Assessment
Interaction with other system issues Downward Regulation
System Voltage Inertia Issues
Issues are all most prevalent overnight under high wind/import conditions System must be optimised to all three issues concurrently Requires a tool to forecast which machines will be on overnight and then enables us to create and optimal solution to all three 10 issues 10 Commercial Solutions
As now, some of these system issues can and will be managed through existing balancing service tools However, National Grid will be looking to tender for services across the summer period, that assist in the management of these system issues. The nature of the service provisions are likely to consist of; Low power or energy output – to minimise impact on downward regulation High reactive capability – MVAr range and output Provide inertia value – sync comp, or synchronous output with low power output e.g. a low SEL capability
11 Commercial Solutions
The issue related to Relays will be reduced in 2014/15 however, Inertia will be a prevalent system issue going forwards Longer Term Solutions HF, LF and Dynamic services on Wind Dynamic Frequency Response on Wind De-coupled/Sync Comp Machines Low-load operation
12 Timelines
2013 2014 2015
Code Changes
Information Gathering Technical Potential Relay Setting Changes Tools Development DRIVE Tender 2013
Commercial Longer Term Balancing Service Solutions
13 Q&A