By Huw Jones LONDON (Reuters) -A temporary brake on gas and electricity derivatives when prices spike could improve how energy markets operate, the European Union’s securities watchdog proposed on Thursday, along with more fundamental changes over time. The European Securities and Markets Authority (ESMA) said the number of trading halts in energy derivatives has been very low in recent weeks despite rules on circuit breakers already in place and prices racing higher following Russia’s invasion of Ukraine in February. “It would, therefore, appear useful to consider implementing, on a temporary…