Transmission Security Limits (TSL) – Transmission security is evaluated as part of NYISO’s reliability planning process. TSL floor values are designed to ensure that minimum capacity requirements for specific localities can be met without depending on transfer levels that might pose transmission security risks 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