TSL (Transmission Security Limits) – Transmission security is assessed as part of the NYISO reliability planning process.  TSL floor values seek to ensure that the minimum capacity procurement requirements established for localities don’t require reliance on transfer amounts into a locality that could create transmission security concerns during peak system conditions.

Source: https://www.nyiso.com/documents/20142/46865072/TSL%20Floor%20Methodology%20Update%20-%2009102024%20ICAPWG.pdf/6b6b842a-5b83-93fc-1d28-de23a96346ce