Oct 27 (Reuters) - China"s state planner said it met with coal producers and the industry association on Wednesday to discuss measures to intervene in coal prices, as well as details such as price levels and the time frame for their implementation. The meeting came on the heels of the National Development and Reform Commission"s (NDRC) announcement on Tuesday that it is studying a new mechanism to guide thermal coal prices to a reasonable range over the long run. read moreIn a statement on the talks, the NDRC did not disclose what price level would be imposed, but three major Chinese coal producers announced on Wednesday they would set thermal coal price ceilings at 1,200 yuan ($188) a tonne for the winter heating season. [nL1N2RN0W9] In night trading on Wednesday, thermal coal futures on the Zhengzhou Commodity Exchange plunged as much as 13% to 1,033.8 yuan a tonne, the lowest since Sept 17. That brought the total decline from a 1,982 yuan record high a week ago to 47.8% as the NDRC rolls out various measures to time high prices. The companies that announced the 1,200 yuan price caps were Shanxi Coking Coal Group, Shanxi Jinneng Holding Group and Inner Mongolia Huineng Coal and Electric, respectively China"s seventh, eighth and 18th biggest coal producers in 2020. Shanxi Coking Coal and Huineng said their price caps were effective from Wednesday, while Jinneng did not give an exact time frame. The NDRC said in its statement it would continue to pay close attention to coal price fluctuations and further study ways of intervening. ($1 = 6.39338 Chinese yuan renminbi)