caused a circuit breaker to trip, resulting in the loss of supply to two major south London substations. September 2003 A week after the London blackout, on 5 September 2003, an incident occurred at Hams Hall substation which affected supply to 201,000 customers in east Birmingham. Affected customers included Network Rail, Birmingham International Airport, and the National Exhibition Centre, with a total of 301 MW of load lost. This was attributed to an error made by National Grid when commissioning protection systems after upgrading components in the substation that August. May 2008 On 27 May 2008 starting at 11:34, two of Britain's largest power stations, Longannet in Fife and Sizewell B in Suffolk, disconnected from the grid ("tripped") within minutes of each other. The total combined loss of generation caused by these trips was at least 1714 MW — larger than the maximum loss of 1260 MW which the grid was required to support that day. The system frequency immediately dropped to 49.2 Hz, and subsequent additional trips of generation due to automatic protection caused the frequency to fall further to a low of 48.8 Hz. This caused the distribution networks to automatically disconnect some customers in order to arrest the frequency drop, and over the next few hours National Grid ordered the distribution networks to reduce voltage in order to reduce demand. At least 500,000 customers lost power. Within 40 minutes, distribution networks were allowed to reconnect all customers, although voltage control continued in some areas until 18:07. The incident was described as a "gigantic coincidence" and was not attributed to lack of investment. Nonetheless, a number of issues were exposed by the event. The behaviour of generation protection during sudden frequency changes caused a number of generators to disconnect from the grid incorrectly. The Low Frequency Demand Disconnection and voltage control schemes also did not deliver as much demand reduction as they were intended to, but this did not have a significant impact on the outage. August 2019 The third event occurred on 9 August 2019, when around a million customers across Great Britain found themselves without power. Lightning struck a transmission line at 4:52 pm, causing the loss of 500 MW embedded (mostly solar) generation. Almost immediately, Little Barford Power Station and Hornsea Wind Farm tripped within seconds of each other, removing 1.378 GW of generation, which was in excess of the 1 GW of backup power