Abstract: When the main power of systems with micro power grid-connected disappear, undervoltage separation protection is often used to rapid trip off micro power, in order to guarantee the reliable operation of terminal substations.Undervoltage separation protection due to high sensitivity, should be reliable locked when TV wire-break, while according to the analysis usual anti-error solutions not entirely suitable for micro power grid-connected situations.In order to solve this problem, the TV secondary break situation and single phase grounding fault are analyzed in detail, based on the compare of voltage changes, an universal anti-error solution to undervoltage separation for micro power grid-connected is proposed.After verified by projects, the solution is reliable, easy to realize, suitable for various main connections and operation modes of terminal substations.