UPDATE 1-UK power grid, train systems need review after August blackout - grid operator

* Review needed to ensure system resilience - National Grid

* Electric trains hit by outage and drop in power frequency

* Ofgem to investigate, can impose financial penalties (Recasts, adds more detail)

By Nina Chestney

LONDON, Sept 10 (Reuters) - Systems that secure Britain's power supplies and keep trains running should be reviewed after a blackout caused by a lightning strike and unexpected power outages last month created travel chaos, the grid operator said on Tuesday.

An outage lasting about an hour on the evening of Aug. 9 cut off 1.1 million electricity customers, including homes, businesses, a hospital and Newcastle Airport, as well as causing severe disruption on the rail network.

A lightning strike and unexpected generation losses resulted in more than 1 gigawatt (GW) of supply going offline and a large drop in the frequency of electricity running through the grid.

National Grid said in its final, technical report to the regulator Ofgem that there should be a review of the electricity grid system to ensure it was resilient as the scale of power generation loss exceeded normal protection standards.

It also said internal protection systems on electric trains should be reviewed to ensure they could continue to operate through disturbances in the electricity system, such as a drop in frequency, one of the reasons some trains stopped running.

"There should also be a wider industry review, including (the government), Ofgem, the ENA (Energy Networks Association) and other stakeholders to establish new and enduring communication arrangements for similar events," National Grid said in the report, commissioned by Ofgem.

Ofgem, which can impose penalties up to a maximum of 10% of the regulated companies turnover in Britain, opened its own investigation to establish whether any of the grid and network operators or generators breached their licence conditions.

National Grid said a lightning strike hit the transmission system late afternoon on Aug. 9, which resulted in tripping around 150 megawatts (MW) of generation.

At the same time, unexpected power losses at Orsted's Hornsea offshore wind farm and RWE Generation's Little Barford gas-fired power station, resulted in more than 1 GW going offline and a large drop in frequency.

The frequency drop resulted in a further trip of 350 MW of generation and then one of the gas turbines at Little Barton tripped, bringing the total loss of generation to almost 1.7 GW. This led to customers being automatically disconnected.

Supplies were restored within 40 minutes, the report said. However, disruption to rail services extended through into Saturday morning as 30 trains stopped operating.

(Reporting by Nina Chestney; Additional reporting by Muvija M and Noor Zainab Hussain in Bengaluru; Editing by Louise Heavens and Edmund Blair)